This document presents a numerical and experimental study of frost formation on cold cylinders. It begins with an introduction and literature review of previous research on modeling and measuring frost. The document then describes the mathematical model developed, which divides frost formation into two stages: 1) one-dimensional crystal growth and 2) interaction between crystals forming a porous frost layer. Equations for heat and mass transfer are formulated for the first stage. The document validates the numerical model with experimental measurements of frost thickness and deposition rate on a cylinder under varying conditions.
Double Diffusive Convection and the Improvement of Flow in Square Porous AnnulusIJERA Editor
There has been increased interest shown in recent years to investigate the behavior of heat and mass transfer in a square annulus with a porous medium fixed between the inner and outer walls. This paper aims to evaluate the Soret effect arising in the case of heat and mass transfer in a porous medium bounded by a square annulus and subjected to isothermal heating of the inner surfaces as well as the outer horizontal surfaces. The phenomenon is governed by 3 partial differential equations, the momentum, energy and concentration equations, that are coupled together and result in a situation where change in one variable affects the other equations and vice versa. The partial differential equations are converted into finite element equations with the help of the Galerkin method and then solved to predict solution variables such as temperature, stream function and concentration in the porous medium. It is found that the heat transfer rate at the hot wall decreases with increasing viscous dissipation effect in the porous medium.
Heat transfer studies were carried out in a laboratory scale gas-solid fluidized bed with 0.1m
ID x 1 m length column, using three sizes of local sand particles of 301, 454, and 560 µm. the bed
region was heated bya horizontal heat transfer probe. It was made of copper rod (15 mm ODx50 mm
long) and insulated at the ends by Teflon. A hole was drilled at the center of the rod to accommodate
a cartridge heater 200 W (6.5 mm OD x 42 mm long). Three bed inventories of sand 1.5 kg, 2.0 kg,
and 2.5 kg, four superficial air velocities of 1.0 m/s, 1.25 m/s, 1.5 m/s, 1.75 m/s were used. Three
heat fluxes of 1698.9, 2928.4, 4675.7 W m-2 were employed. The data obtained showed how the heat
transfer coefficient effected by the above operating parameters. The heat transfer coefficient is
directly proportional with air superficial velocity as well as the bed inventory and heat fluxes but
inversely proportional with sand particles size.
This document presents an analysis of free convective flow and heat transfer of a viscous incompressible fluid over a linearly moving vertical porous plate with suction and viscous dissipation. The fluid viscosity is assumed to vary linearly with temperature. Governing boundary layer equations are non-dimensionalized using similarity transformations and reduced to a boundary value problem. The problem is solved numerically using a shooting method along with the 4th order Runge-Kutta method. Results for dimensionless velocity and temperature distributions are presented for various parameter values, and skin friction and Nusselt numbers are reported in tables.
This document describes a study of gravity-driven film flow along an inclined wall where the physical properties (density, viscosity, thermal conductivity, specific heat) vary with temperature. The study uses similarity transformations to solve the boundary value problem of the governing equations for water, air, and engine oil. Results are presented showing the effect of variable physical properties on flow and heat transfer for a water film with inlet temperatures of 20°C and 60°C.
Computational Fluid Dynamics (CFD) Analysis of Natural Convection of Converge...IJERA Editor
Computational Fluid Dynamics (CFD) analysis was carried out for the convergent-divergent fins arranged inline and staggered on the base plate as per the experimental setup provided in the technical paper [1]. This paper reports on the validation of results of modeling and simulation in CFD. The simulation was carried out using the ANSYS 12.0 as the CFD modeling software. The main objective of the CFD analysis was to calculate the temperature distribution on the surface of the base plate and surface of the convergent-divergent fins for the given inline and staggered arrangement of fins due to the effect of natural convection heat transfer for different heat power inputs, and also to compare the CFD results with the experimental results.
The document compares earthquake wave propagation analysis results from SHAKE2000 and Plaxis v8 based on Indonesian standards SNI 03-1726-2012 for North, Central, and South Jakarta. The analysis models soil at five locations using synthetic ground motions for a 2500-year earthquake. The results show site-specific spectra are generally higher than the standard. Linear Elastic modeling in Plaxis gives very high values unsuitable for seismic analysis, while Mohr-Coulomb is also unsuitable. Hardening Soil with Small Strain modeling is most suitable. SHAKE2000's Linear Equivalent modeling best matches the standard but more study of soil parameters is needed.
This document discusses the use of pedotransfer functions (PTFs) to estimate soil hydraulic properties for use in soil water balance models. The performance of published PTFs developed by Vereecken et al. (1989, 1990) were evaluated by comparing simulated soil moisture contents, pressure heads, and drainage fluxes using estimated soil hydraulic properties against measured field data from a test site. Simulations using estimated properties overpredicted soil moisture contents and drainage fluxes compared to simulations using measured soil hydraulic properties from the test site. The study highlights the need for further evaluation of PTFs against field measurements of soil water balance components before widespread application in models.
Double Diffusive Convection and the Improvement of Flow in Square Porous AnnulusIJERA Editor
There has been increased interest shown in recent years to investigate the behavior of heat and mass transfer in a square annulus with a porous medium fixed between the inner and outer walls. This paper aims to evaluate the Soret effect arising in the case of heat and mass transfer in a porous medium bounded by a square annulus and subjected to isothermal heating of the inner surfaces as well as the outer horizontal surfaces. The phenomenon is governed by 3 partial differential equations, the momentum, energy and concentration equations, that are coupled together and result in a situation where change in one variable affects the other equations and vice versa. The partial differential equations are converted into finite element equations with the help of the Galerkin method and then solved to predict solution variables such as temperature, stream function and concentration in the porous medium. It is found that the heat transfer rate at the hot wall decreases with increasing viscous dissipation effect in the porous medium.
Heat transfer studies were carried out in a laboratory scale gas-solid fluidized bed with 0.1m
ID x 1 m length column, using three sizes of local sand particles of 301, 454, and 560 µm. the bed
region was heated bya horizontal heat transfer probe. It was made of copper rod (15 mm ODx50 mm
long) and insulated at the ends by Teflon. A hole was drilled at the center of the rod to accommodate
a cartridge heater 200 W (6.5 mm OD x 42 mm long). Three bed inventories of sand 1.5 kg, 2.0 kg,
and 2.5 kg, four superficial air velocities of 1.0 m/s, 1.25 m/s, 1.5 m/s, 1.75 m/s were used. Three
heat fluxes of 1698.9, 2928.4, 4675.7 W m-2 were employed. The data obtained showed how the heat
transfer coefficient effected by the above operating parameters. The heat transfer coefficient is
directly proportional with air superficial velocity as well as the bed inventory and heat fluxes but
inversely proportional with sand particles size.
This document presents an analysis of free convective flow and heat transfer of a viscous incompressible fluid over a linearly moving vertical porous plate with suction and viscous dissipation. The fluid viscosity is assumed to vary linearly with temperature. Governing boundary layer equations are non-dimensionalized using similarity transformations and reduced to a boundary value problem. The problem is solved numerically using a shooting method along with the 4th order Runge-Kutta method. Results for dimensionless velocity and temperature distributions are presented for various parameter values, and skin friction and Nusselt numbers are reported in tables.
This document describes a study of gravity-driven film flow along an inclined wall where the physical properties (density, viscosity, thermal conductivity, specific heat) vary with temperature. The study uses similarity transformations to solve the boundary value problem of the governing equations for water, air, and engine oil. Results are presented showing the effect of variable physical properties on flow and heat transfer for a water film with inlet temperatures of 20°C and 60°C.
Computational Fluid Dynamics (CFD) Analysis of Natural Convection of Converge...IJERA Editor
Computational Fluid Dynamics (CFD) analysis was carried out for the convergent-divergent fins arranged inline and staggered on the base plate as per the experimental setup provided in the technical paper [1]. This paper reports on the validation of results of modeling and simulation in CFD. The simulation was carried out using the ANSYS 12.0 as the CFD modeling software. The main objective of the CFD analysis was to calculate the temperature distribution on the surface of the base plate and surface of the convergent-divergent fins for the given inline and staggered arrangement of fins due to the effect of natural convection heat transfer for different heat power inputs, and also to compare the CFD results with the experimental results.
The document compares earthquake wave propagation analysis results from SHAKE2000 and Plaxis v8 based on Indonesian standards SNI 03-1726-2012 for North, Central, and South Jakarta. The analysis models soil at five locations using synthetic ground motions for a 2500-year earthquake. The results show site-specific spectra are generally higher than the standard. Linear Elastic modeling in Plaxis gives very high values unsuitable for seismic analysis, while Mohr-Coulomb is also unsuitable. Hardening Soil with Small Strain modeling is most suitable. SHAKE2000's Linear Equivalent modeling best matches the standard but more study of soil parameters is needed.
This document discusses the use of pedotransfer functions (PTFs) to estimate soil hydraulic properties for use in soil water balance models. The performance of published PTFs developed by Vereecken et al. (1989, 1990) were evaluated by comparing simulated soil moisture contents, pressure heads, and drainage fluxes using estimated soil hydraulic properties against measured field data from a test site. Simulations using estimated properties overpredicted soil moisture contents and drainage fluxes compared to simulations using measured soil hydraulic properties from the test site. The study highlights the need for further evaluation of PTFs against field measurements of soil water balance components before widespread application in models.
11.[9 20] analytical study of rainfal of nigeriaAlexander Decker
This document analyzes rainfall and temperature trends in catchment states and stations of the Benin-Owena River Basin in Nigeria over a 35-year period. The trends were analyzed using Cumulative Summation and rank-sum tests. The results show that as temperature increases, rainfall also increases. However, the trends indicate no significant departures in climatic parameters across the studied states. Temperature variation ranges from 0.4% to 3.5% while rainfall variation ranges from 0.2% to 2.7%, both showing an upward trend. In conclusion, the analyses found no evidence of serious interventions in meteorological data, suggesting rainfall data comes from areas of similar climate with no significant changes over time.
A strategy for an efficient simulation of countcorrent flows in the iron blas...Josué Medeiros
This document summarizes a strategy for efficiently simulating countercurrent gas and solids flows in an iron blast furnace. Key aspects of the strategy include:
1) Modeling the gas flow using an anisotropic Ergun equation that accounts for layered porous media and can be solved using a computationally efficient algorithm.
2) Modeling the slow descending solids flow using an irrotational flow assumption and conservation of mass.
3) Modeling heat transfer between the gas and solids using energy balance equations that account for convection and heat exchange, with appropriate enthalpy-temperature relationships.
4) Accounting for the stagnant central "deadman" zone and high-flow "race
The document discusses using fractal dimension to analyze cloud structure. It is hypothesized that the fractal dimension of cloud-top temperature is related to the fractal dimension of ice particles in the cloud. The researcher calculates the fractal dimension of cloud boundaries in satellite images using a grid method. Results show a strong positive correlation between higher fractal dimension and higher cloud-top temperature, consistent with prior research finding ice crystals have higher fractal dimension at warmer temperatures. This relationship could provide insight into cloud geometry and properties for radiation modeling.
Settlement prediction research on the gravel pile in soft soil subgradeIJERA Editor
Settlement prediction methods of soft subgrade based on the soil mechanical theories and mathematical statistics emerges in endlessly, but together with its limitations; the single theoretical calculation method maybe sometimes good, sometimes bad without the capacity to consider the change of the load; however the study of the theory of the combined forecast method is far from perfect. Under this situation, in view of the engineering practice in soft soil subgrade deformation law research in order to put forward a reasonable settlement prediction method, which is a problem urgently to be solved at present. Relying on gravel pile in soft soil subgrade construction in the highway K9+420-K9+550 section, and analyzing the data measured according to the soft soil foundation in the loading and constant loading period, taking classification of embankment load into account, and based on the related parameters of soil at the same time using the numerical analysis of saturated soft soil subgrade deformation-seepage coupling calculation, comparing the measured data with the finite element results and checking the fit, based on detailed sedimentation data by using curve-fitting method for calculating ultimate settlement value and compared with the finite element method settlement value for several years under broaden embankment. The two values differ by 1.5cm, which is in a controllable range for soft soil. Then thus the results are true and reliable in order to have implications for similar projects.
Splashing mechanism during impact of a hollow droplet on a substrate(156)docamarjitkene
1) The document summarizes a numerical study comparing the splashing behavior of continuous and hollow molten droplets during impact on a substrate.
2) For continuous droplets, splashing occurs very early during spreading due to high spreading velocities creating instabilities at the edge, detaching satellite droplets that solidify and create barriers for further spreading.
3) In contrast, hollow droplets were found to experience significantly less splashing due to a new phenomenon of counter liquid jetting during flattening, which suppresses instabilities.
Predicting MassmovementProcesses induced in Periglazial AreasInfoAndina CONDESAN
This document summarizes a study on predicting mass movement processes induced in periglacial areas in central Switzerland. The study examines climate change impacts using process models to simulate rockfall, landslides, debris flows, and their deposition volumes. The results indicate that glacier retreat, rising temperatures, and thawing permafrost will increase the frequency and magnitude of mass movements. Specifically, rockfall deposition volumes are projected to increase from 150,000 cubic meters currently to over 2 million cubic meters by 2060 due to these climate change impacts. The conclusions emphasize the importance of understanding ongoing geomorphic processes and process chains to accurately predict future mass movement risks.
Steve's presentation at ICCC 2009(Stephen Mc Intyre)Wladimir Illescas
This document discusses criticisms of claims that the 1990s were the warmest decade and 1998 the warmest year of the millennium based on temperature reconstructions. It notes that minor variations in data versions and proxies can yield opposite results. It also discusses criticisms of the "hockey stick" temperature graph that was featured prominently in IPCC reports and disputes that multiple independent studies all found late 20th century warming, noting many used common proxies. The document questions whether key proxies like bristlecones have been robustly updated and whether simple statistical models apply to complex trees.
1) The document discusses a study evaluating a new turbine nozzle guide vane design with radial cylindrical cooling holes on the pressure side to improve film cooling effectiveness in a cooling blind area near the pressure side gill region.
2) Experiments were conducted on a scaled nozzle guide vane cascade model with four rows of radial cooling holes at various blowing ratios. Pressure sensitive painting was used to measure film cooling effectiveness.
3) The results showed that film cooling effectiveness near the pressure side gill region increased with the new design, with a double-peak cooled region developing towards the suction side at higher blowing ratios. Pressure side radial cooling holes improved film cooling in the gill region but effectiveness decreased along the axial chord at low
Mapping Gradex values on the Tensift basin (Morocco)IJERA Editor
The aim of this study is to elaborate the cartography of Gradex parameter used in the Gradex method for estimating flood peaks in order to size hydraulic structures. Map of spatial variation is elaborated using the geostatistical method of kriging. Several reference functions (exponential model, spherical, linear, Gaussian and cubic) were used for modeling the kriging variogram. Cross-validation enabled a comparison between the results of these models and choice of spherical model with anisotropy and trend fit by a second-order polynomial as the most suitable. The use of available series of annual maximum daily rainfall recorded at 23 rainfall stations, distributed over the Tensift basin, led also to develop the cartography of standard prediction errors‟ values associated to the predicted parameter for each point of Tensift basin. These errors vary from acceptable values (16.8%) to very high ones depending on the density of the rainfall stations at the desired site.
Theoretical study of heat transfer through a sun space filled with a porous m...Ahmed Al-Sammarraie
This document presents a theoretical study of heat transfer through a sun space filled with either a porous medium (glass balls) or air. The study developed mathematical models to describe the heat transfer based on energy balances of the glass layer, storage wall surfaces, and wall layer. The models were one-dimensional and assumed constant properties. The results showed that using a porous medium enhanced both the heat transferred to and stored in the storage wall, with increases of 19.7% for outside wall temperature and 20.3% for inside wall temperature, compared to using air.
Review on Effect of Chevron Angle and Numerical Investigation of Dimensionles...IRJET Journal
The document reviews the effect of chevron angle and numerical investigation of dimensionless numbers in plate heat exchangers. It discusses previous research that has examined heat transfer coefficients and pressure drops at different chevron angles. The paper aims to design a plate heat exchanger using different chevron angles and evaluate heat transfer performance through simulation analysis of numbers like Nusselt, Reynolds, and Prandtl.
FIELD AND THEORETICAL ANALYSIS OF ACCELERATED CONSOLIDATION USING VERTICAL DR...P singh
Mumbai is the region consisting of soft compressible marine clay deposits. There are several construction problems on such soils and thus ground improvement is need to be carried out. Vertical drains is generally preferred technique as accelerated settlement is achieved during the construction phase itself if planned accordingly. The concept of vertical drains is based on the theory of three dimensional consolidation as described by Terzaghi (1943). Based on this concept, a consolidation programme is developed and an attempt is made to determine the field to laboratory coefficient of vertical consolidation ratio by Taylor’s Square Root of Time Method and Casagrande’s Logarithm of Time Fitting Method for this region by considering the case study of Bhandup Lagoon Works Embankment. Based on this ratio, the rate of consolidation and time required for consolidation in the field can be determined knowing the consolidation parameters. Equations are developed by using output of the programme and it is explained.
The document discusses the phenomenon of rewetting, where a liquid comes into contact with a hot surface. Initially, a vapor layer forms preventing contact between the liquid and hot surface. As the surface cools, the vapor layer collapses and the liquid wets the surface, increasing heat transfer. The study analyzes rewetting during emergency cooling following loss of coolant accidents and quenching applications. A test facility uses an impinging liquid jet on a heated metal foil to observe rewetting front propagation and surface temperature changes, evaluating how parameters like initial temperature and nozzle spacing affect rewetting velocity and heat flux.
This document discusses the modulus of subgrade reaction (Ks), which represents the relationship between applied stress and associated soil settlement beneath foundations. It defines Ks and describes several analytical models and methods for calculating Ks values, including plate loading tests, correlations with soil properties, and pseudo-coupled approaches that assign different Ks values depending on location beneath the foundation. Factors that influence Ks include soil type, moisture content, and foundation geometry.
This document summarizes a numerical study on mixed convection flow from a moving vertical plate in a parallel free stream. The plate moves with constant velocity in the direction of the flow. The study considers the effects of thermophoresis and thermal radiation on the flow. The governing equations are non-dimensionalized and solved using an implicit finite difference scheme. Results for the velocity and concentration profiles and wall deposition velocity are presented for various parameter values. The results are verified by comparing with previous studies and good agreement is found. Key parameters influencing the flow include thermophoresis, mixed convection, thermal radiation, and the plate and free stream velocities.
This document analyzes the thermal characteristics of flared and rectangular fin profiles using finite element analysis. Solid models of the fin geometries were created in SolidWorks. Meshing was performed in ANSYS using tetrahedral and hexahedral elements. Boundary conditions were set up and the analysis was run to obtain temperature distributions and heat fluxes. Results for the different fin profiles were compared to determine the more efficient design. Prior research on heat transfer analysis of fins using finite element methods is also reviewed.
Radiation and magneticfield effects on unsteady naturalAlexander Decker
This document discusses research on the effects of thermal radiation and magnetic fields on unsteady natural convective flow of nanofluids past an infinite vertical plate with a heat source. The following key points are discussed:
- Governing equations for the unsteady, two-dimensional flow are derived taking into account radiation, magnetic fields, and thermophysical properties of nanofluids.
- The equations are solved numerically using Laplace transform techniques. Parameters like radiation, magnetic field, heat source, and nanoparticle volume fraction are examined.
- It is found that increasing the magnetic field decreases fluid velocity, while radiation, heat source, and nanoparticle volume fraction have a greater influence on fluid velocity and temperature profiles. Nan
NUMERICAL INVESTIGATION OF AN UNSTEADY MIXED CONVECTIVE MASS AND HEAT TRANSFE...IAEME Publication
In the present paper an analysis of mixed convection of an unsteady magneto hydrodynamic (MHD) flow of an incompressible viscous fluid through porous media due to a vertical porous stretching sheet in the presence of viscous dissipation, thermal radiation and heat source /sink has been carried out. The fluid considered is viscous and incompressible. The governing partial differential equations of the flow, mass and heat transfer are highly non linear hence are converted into a system of ordinary differential equations using suitable similarity transformations. These ordinary differential equations are further converted into 7 first order ordinary differential equations and are solved numerically by Matlab ode-45 solver via shooting method.
Fuzzy numbers, Nth - order Fuzzy Initial Value Problems, Runge-Kutta method, ...IOSR Journals
A numerical study is presented of two-dimensional laminar steady-state on megneto-hydrodynamics
(MHD) free convection for heat flow patterns within trapezoidal enclosures. A finite element analysis is
performed to investigate the effects of unifor heating and is also used for solving the Navier-Stokes and
Energybalance equations.In this study, cold bottom walls, uniformly heated left and right (side) walls and
insulated top walls with inclination angles (ф) are considered in a trapezoidal enclosure. The present numerical
procedure adopted in this investigation yields consistent performance over a wide range of parameters, Prandtl
numbers, (Pr = 0.026 - 0.7), and Rayleigh numbers (Ra = 103 – 105), Hartmann number (Ha = 50) with various
tilt angles Ф = 450, 300 and 00(square).Numerical results are presented in terms of streamlines, isotherms, heat
function (total heat flux) and nusselt numbers.for different Ra and Pr. As Ra increases conduction dominant
region changes for different Pr. Complete heat transfer analysis is performed in terms of local and average
nusselt numbers.
This document proposes an M-payment scheme where a customer sends a cheque image email to a merchant for payment. It discusses issues with existing payment schemes like lack of broadcast capabilities, costly infrastructure, and security/authentication issues. The proposed scheme uses email and a bank module to address these issues. The bank module authenticates the cheque image, transfers funds, and sends confirmation messages. This allows for secure M-payments without additional charges or infrastructure requirements beyond existing mobile and internet technologies.
The document discusses several major video game companies:
- Electronic Arts (EA) is one of the largest third-party video game publishers founded in 1982 by Trip Hawkins. EA is headed by Andrew Wilson and Frank Gibeau.
- Rockstar is a British video game developer founded in 1998 and known for the Grand Theft Auto series. It was acquired by Take-Two Interactive.
- Activision is one of the largest third-party video game publishers founded in 1979. It merged with Vivendi Games in 2008 to form Activision Blizzard.
This document provides lesson materials for a math lesson on reading algebraic expressions where letters stand for numbers. It includes examples of expressing algebraic expressions using words, such as "a minus b" for a-b and "4 times f plus u" for 4f + u. Students are asked to complete practice problems identifying parts of expressions using mathematical terms and writing expressions using words. The document concludes with an exit ticket question assessing a student's understanding of reading an expression.
11.[9 20] analytical study of rainfal of nigeriaAlexander Decker
This document analyzes rainfall and temperature trends in catchment states and stations of the Benin-Owena River Basin in Nigeria over a 35-year period. The trends were analyzed using Cumulative Summation and rank-sum tests. The results show that as temperature increases, rainfall also increases. However, the trends indicate no significant departures in climatic parameters across the studied states. Temperature variation ranges from 0.4% to 3.5% while rainfall variation ranges from 0.2% to 2.7%, both showing an upward trend. In conclusion, the analyses found no evidence of serious interventions in meteorological data, suggesting rainfall data comes from areas of similar climate with no significant changes over time.
A strategy for an efficient simulation of countcorrent flows in the iron blas...Josué Medeiros
This document summarizes a strategy for efficiently simulating countercurrent gas and solids flows in an iron blast furnace. Key aspects of the strategy include:
1) Modeling the gas flow using an anisotropic Ergun equation that accounts for layered porous media and can be solved using a computationally efficient algorithm.
2) Modeling the slow descending solids flow using an irrotational flow assumption and conservation of mass.
3) Modeling heat transfer between the gas and solids using energy balance equations that account for convection and heat exchange, with appropriate enthalpy-temperature relationships.
4) Accounting for the stagnant central "deadman" zone and high-flow "race
The document discusses using fractal dimension to analyze cloud structure. It is hypothesized that the fractal dimension of cloud-top temperature is related to the fractal dimension of ice particles in the cloud. The researcher calculates the fractal dimension of cloud boundaries in satellite images using a grid method. Results show a strong positive correlation between higher fractal dimension and higher cloud-top temperature, consistent with prior research finding ice crystals have higher fractal dimension at warmer temperatures. This relationship could provide insight into cloud geometry and properties for radiation modeling.
Settlement prediction research on the gravel pile in soft soil subgradeIJERA Editor
Settlement prediction methods of soft subgrade based on the soil mechanical theories and mathematical statistics emerges in endlessly, but together with its limitations; the single theoretical calculation method maybe sometimes good, sometimes bad without the capacity to consider the change of the load; however the study of the theory of the combined forecast method is far from perfect. Under this situation, in view of the engineering practice in soft soil subgrade deformation law research in order to put forward a reasonable settlement prediction method, which is a problem urgently to be solved at present. Relying on gravel pile in soft soil subgrade construction in the highway K9+420-K9+550 section, and analyzing the data measured according to the soft soil foundation in the loading and constant loading period, taking classification of embankment load into account, and based on the related parameters of soil at the same time using the numerical analysis of saturated soft soil subgrade deformation-seepage coupling calculation, comparing the measured data with the finite element results and checking the fit, based on detailed sedimentation data by using curve-fitting method for calculating ultimate settlement value and compared with the finite element method settlement value for several years under broaden embankment. The two values differ by 1.5cm, which is in a controllable range for soft soil. Then thus the results are true and reliable in order to have implications for similar projects.
Splashing mechanism during impact of a hollow droplet on a substrate(156)docamarjitkene
1) The document summarizes a numerical study comparing the splashing behavior of continuous and hollow molten droplets during impact on a substrate.
2) For continuous droplets, splashing occurs very early during spreading due to high spreading velocities creating instabilities at the edge, detaching satellite droplets that solidify and create barriers for further spreading.
3) In contrast, hollow droplets were found to experience significantly less splashing due to a new phenomenon of counter liquid jetting during flattening, which suppresses instabilities.
Predicting MassmovementProcesses induced in Periglazial AreasInfoAndina CONDESAN
This document summarizes a study on predicting mass movement processes induced in periglacial areas in central Switzerland. The study examines climate change impacts using process models to simulate rockfall, landslides, debris flows, and their deposition volumes. The results indicate that glacier retreat, rising temperatures, and thawing permafrost will increase the frequency and magnitude of mass movements. Specifically, rockfall deposition volumes are projected to increase from 150,000 cubic meters currently to over 2 million cubic meters by 2060 due to these climate change impacts. The conclusions emphasize the importance of understanding ongoing geomorphic processes and process chains to accurately predict future mass movement risks.
Steve's presentation at ICCC 2009(Stephen Mc Intyre)Wladimir Illescas
This document discusses criticisms of claims that the 1990s were the warmest decade and 1998 the warmest year of the millennium based on temperature reconstructions. It notes that minor variations in data versions and proxies can yield opposite results. It also discusses criticisms of the "hockey stick" temperature graph that was featured prominently in IPCC reports and disputes that multiple independent studies all found late 20th century warming, noting many used common proxies. The document questions whether key proxies like bristlecones have been robustly updated and whether simple statistical models apply to complex trees.
1) The document discusses a study evaluating a new turbine nozzle guide vane design with radial cylindrical cooling holes on the pressure side to improve film cooling effectiveness in a cooling blind area near the pressure side gill region.
2) Experiments were conducted on a scaled nozzle guide vane cascade model with four rows of radial cooling holes at various blowing ratios. Pressure sensitive painting was used to measure film cooling effectiveness.
3) The results showed that film cooling effectiveness near the pressure side gill region increased with the new design, with a double-peak cooled region developing towards the suction side at higher blowing ratios. Pressure side radial cooling holes improved film cooling in the gill region but effectiveness decreased along the axial chord at low
Mapping Gradex values on the Tensift basin (Morocco)IJERA Editor
The aim of this study is to elaborate the cartography of Gradex parameter used in the Gradex method for estimating flood peaks in order to size hydraulic structures. Map of spatial variation is elaborated using the geostatistical method of kriging. Several reference functions (exponential model, spherical, linear, Gaussian and cubic) were used for modeling the kriging variogram. Cross-validation enabled a comparison between the results of these models and choice of spherical model with anisotropy and trend fit by a second-order polynomial as the most suitable. The use of available series of annual maximum daily rainfall recorded at 23 rainfall stations, distributed over the Tensift basin, led also to develop the cartography of standard prediction errors‟ values associated to the predicted parameter for each point of Tensift basin. These errors vary from acceptable values (16.8%) to very high ones depending on the density of the rainfall stations at the desired site.
Theoretical study of heat transfer through a sun space filled with a porous m...Ahmed Al-Sammarraie
This document presents a theoretical study of heat transfer through a sun space filled with either a porous medium (glass balls) or air. The study developed mathematical models to describe the heat transfer based on energy balances of the glass layer, storage wall surfaces, and wall layer. The models were one-dimensional and assumed constant properties. The results showed that using a porous medium enhanced both the heat transferred to and stored in the storage wall, with increases of 19.7% for outside wall temperature and 20.3% for inside wall temperature, compared to using air.
Review on Effect of Chevron Angle and Numerical Investigation of Dimensionles...IRJET Journal
The document reviews the effect of chevron angle and numerical investigation of dimensionless numbers in plate heat exchangers. It discusses previous research that has examined heat transfer coefficients and pressure drops at different chevron angles. The paper aims to design a plate heat exchanger using different chevron angles and evaluate heat transfer performance through simulation analysis of numbers like Nusselt, Reynolds, and Prandtl.
FIELD AND THEORETICAL ANALYSIS OF ACCELERATED CONSOLIDATION USING VERTICAL DR...P singh
Mumbai is the region consisting of soft compressible marine clay deposits. There are several construction problems on such soils and thus ground improvement is need to be carried out. Vertical drains is generally preferred technique as accelerated settlement is achieved during the construction phase itself if planned accordingly. The concept of vertical drains is based on the theory of three dimensional consolidation as described by Terzaghi (1943). Based on this concept, a consolidation programme is developed and an attempt is made to determine the field to laboratory coefficient of vertical consolidation ratio by Taylor’s Square Root of Time Method and Casagrande’s Logarithm of Time Fitting Method for this region by considering the case study of Bhandup Lagoon Works Embankment. Based on this ratio, the rate of consolidation and time required for consolidation in the field can be determined knowing the consolidation parameters. Equations are developed by using output of the programme and it is explained.
The document discusses the phenomenon of rewetting, where a liquid comes into contact with a hot surface. Initially, a vapor layer forms preventing contact between the liquid and hot surface. As the surface cools, the vapor layer collapses and the liquid wets the surface, increasing heat transfer. The study analyzes rewetting during emergency cooling following loss of coolant accidents and quenching applications. A test facility uses an impinging liquid jet on a heated metal foil to observe rewetting front propagation and surface temperature changes, evaluating how parameters like initial temperature and nozzle spacing affect rewetting velocity and heat flux.
This document discusses the modulus of subgrade reaction (Ks), which represents the relationship between applied stress and associated soil settlement beneath foundations. It defines Ks and describes several analytical models and methods for calculating Ks values, including plate loading tests, correlations with soil properties, and pseudo-coupled approaches that assign different Ks values depending on location beneath the foundation. Factors that influence Ks include soil type, moisture content, and foundation geometry.
This document summarizes a numerical study on mixed convection flow from a moving vertical plate in a parallel free stream. The plate moves with constant velocity in the direction of the flow. The study considers the effects of thermophoresis and thermal radiation on the flow. The governing equations are non-dimensionalized and solved using an implicit finite difference scheme. Results for the velocity and concentration profiles and wall deposition velocity are presented for various parameter values. The results are verified by comparing with previous studies and good agreement is found. Key parameters influencing the flow include thermophoresis, mixed convection, thermal radiation, and the plate and free stream velocities.
This document analyzes the thermal characteristics of flared and rectangular fin profiles using finite element analysis. Solid models of the fin geometries were created in SolidWorks. Meshing was performed in ANSYS using tetrahedral and hexahedral elements. Boundary conditions were set up and the analysis was run to obtain temperature distributions and heat fluxes. Results for the different fin profiles were compared to determine the more efficient design. Prior research on heat transfer analysis of fins using finite element methods is also reviewed.
Radiation and magneticfield effects on unsteady naturalAlexander Decker
This document discusses research on the effects of thermal radiation and magnetic fields on unsteady natural convective flow of nanofluids past an infinite vertical plate with a heat source. The following key points are discussed:
- Governing equations for the unsteady, two-dimensional flow are derived taking into account radiation, magnetic fields, and thermophysical properties of nanofluids.
- The equations are solved numerically using Laplace transform techniques. Parameters like radiation, magnetic field, heat source, and nanoparticle volume fraction are examined.
- It is found that increasing the magnetic field decreases fluid velocity, while radiation, heat source, and nanoparticle volume fraction have a greater influence on fluid velocity and temperature profiles. Nan
NUMERICAL INVESTIGATION OF AN UNSTEADY MIXED CONVECTIVE MASS AND HEAT TRANSFE...IAEME Publication
In the present paper an analysis of mixed convection of an unsteady magneto hydrodynamic (MHD) flow of an incompressible viscous fluid through porous media due to a vertical porous stretching sheet in the presence of viscous dissipation, thermal radiation and heat source /sink has been carried out. The fluid considered is viscous and incompressible. The governing partial differential equations of the flow, mass and heat transfer are highly non linear hence are converted into a system of ordinary differential equations using suitable similarity transformations. These ordinary differential equations are further converted into 7 first order ordinary differential equations and are solved numerically by Matlab ode-45 solver via shooting method.
Fuzzy numbers, Nth - order Fuzzy Initial Value Problems, Runge-Kutta method, ...IOSR Journals
A numerical study is presented of two-dimensional laminar steady-state on megneto-hydrodynamics
(MHD) free convection for heat flow patterns within trapezoidal enclosures. A finite element analysis is
performed to investigate the effects of unifor heating and is also used for solving the Navier-Stokes and
Energybalance equations.In this study, cold bottom walls, uniformly heated left and right (side) walls and
insulated top walls with inclination angles (ф) are considered in a trapezoidal enclosure. The present numerical
procedure adopted in this investigation yields consistent performance over a wide range of parameters, Prandtl
numbers, (Pr = 0.026 - 0.7), and Rayleigh numbers (Ra = 103 – 105), Hartmann number (Ha = 50) with various
tilt angles Ф = 450, 300 and 00(square).Numerical results are presented in terms of streamlines, isotherms, heat
function (total heat flux) and nusselt numbers.for different Ra and Pr. As Ra increases conduction dominant
region changes for different Pr. Complete heat transfer analysis is performed in terms of local and average
nusselt numbers.
This document proposes an M-payment scheme where a customer sends a cheque image email to a merchant for payment. It discusses issues with existing payment schemes like lack of broadcast capabilities, costly infrastructure, and security/authentication issues. The proposed scheme uses email and a bank module to address these issues. The bank module authenticates the cheque image, transfers funds, and sends confirmation messages. This allows for secure M-payments without additional charges or infrastructure requirements beyond existing mobile and internet technologies.
The document discusses several major video game companies:
- Electronic Arts (EA) is one of the largest third-party video game publishers founded in 1982 by Trip Hawkins. EA is headed by Andrew Wilson and Frank Gibeau.
- Rockstar is a British video game developer founded in 1998 and known for the Grand Theft Auto series. It was acquired by Take-Two Interactive.
- Activision is one of the largest third-party video game publishers founded in 1979. It merged with Vivendi Games in 2008 to form Activision Blizzard.
This document provides lesson materials for a math lesson on reading algebraic expressions where letters stand for numbers. It includes examples of expressing algebraic expressions using words, such as "a minus b" for a-b and "4 times f plus u" for 4f + u. Students are asked to complete practice problems identifying parts of expressions using mathematical terms and writing expressions using words. The document concludes with an exit ticket question assessing a student's understanding of reading an expression.
This document provides a summary of Pocholo D. Gonzales' professional background and experience. It includes details about his education, work history in radio, television and voice acting, organizations involved in, and events spoken at. Specifically, it outlines his role as a founder and managing director of his own voice production companies, host of youth radio programs, and freelance voice talent for various TV networks and productions over the past 20 years.
AIDS is caused by the HIV virus. HIV stands for Human Immunodeficiency Virus. If a person has HIV, they are HIV positive but may not have developed AIDS. AIDS is the final stage of HIV infection where the immune system is severely damaged. There is no cure for HIV/AIDS but it can be prevented through safe sex practices and avoiding contact with infected bodily fluids. People living with HIV/AIDS should be treated with empathy, allowed to participate normally in family life, and supported with proper medical care and healthy lifestyle habits. Discrimination against those with HIV/AIDS should be avoided.
The use of solar energy for water desalination becomes vital for sustainable water supply.
This paper aims to analyze the experimental behavior of double slope solar theoretically still
(DSSS). In this work, we proposed a theoretical model that can predict the DSSS performance. The
theoretical results of temperatures and the impact of wind speed on water production are in good
agreement with experimental findings. It is found that the temperature augments with augmenting the wind speed until a critical value, where the temperature starts to drop. In addition, water
production increases with increasing speed. In this way, we determined the optimum wind speed
to have maximum water production with minimum energy consumption simultaneously. The validation of the theoretical model allows us to predict the DSSS production under different climatic
conditions and to scale DSSS dimensions according to the need of water. The salinity of the water
is not a determining factor in its production. The production at 4.2 kWh/m2 daily insolation was
0.58 L/d. The volume of distilled water reaches a maximum value (62.3% efficiency) when glass
and environment temperatures are similar. This phenomenon occurs at 5.5 m/s wind speed
IRJET- Jet Impingement Heat Transfer – A ReviewIRJET Journal
This document reviews research on jet impingement heat transfer. Jet impingement involves directing a jet of fluid at a surface and is an effective method for transferring heat. It has various industrial applications like cooling electronics and turbine blades. The review examines factors that influence heat transfer like jet geometry, cross flow effects, and frequency. It summarizes studies on single and multiple jet impingement, and the effects of parameters like Reynolds number. Conjugate heat transfer involving solid-fluid interaction is also discussed. The review provides an overview of research conducted on jet impingement heat transfer.
CFD Analysis of Single Basin Double Slope Solar Stilljournal ijrtem
Abstract : This paper deals with thethermal and CFD analysis of single basin double slope solar still. The modeling of still is done in solid works software and CFD analysis in ANSYS. CFD analysis for different months of solar irradiance was carried out. Maximum production rate and temperature distribution in the still was analyzed. Keywords: Double slope solar still, CFD analysis, solar irradiance, desalination system.
IRJET- Model Development and Performance Enhancement of Solar Pavement Energy...IRJET Journal
This document describes the development and testing of a solar pavement energy collector. The collector consists of tubes embedded in asphalt pavement that circulate a fluid to transfer solar heat from the pavement surface. Experiments were conducted using wooden frames with copper tubing set in asphalt and insulating materials below. Temperature data at varying flow rates showed increased heat transfer at lower flow rates. The maximum temperature difference between asphalt and non-asphalt surfaces was 7.1°C, indicating the asphalt enhances heat collection. Such systems could utilize solar energy gains to heat buildings while also reducing pavement temperatures and extending road lifespan.
A theoretical evaluation of a double slope solar still using the Energy2D computer program is presented in this document. The heat absorbing plate is 0.25 m2 square, 5 cm high and constructed of stainless steel. The water film is 3 cm high. Conduction heat losses of three commercial thermal insulation were studied: (i) polyurethane (PU), (ii) glass wool (GW), and (iii) expanded polystyrene (EPS). The insulation thickness is 15 cm and the glass cover is tilted at an angle of 30°. For the simulation, thermal conductivity, specific heat, mass density, and optical properties such as emittance, absorptance, reflectance, and transmittance coefficients were considered. After five hours of simulation, the left, central and right zones of insulator indicates 29.7°C; 45.2°C; 25.2°C, while the left, central and right zones indicates 75.7°C; 75.0°C; 75.5°C. The heat flux insulator, water and glass cover in its central zones are: 16.4, 301 and 72.9 W.m–2, correspondingly. The lower heat loss was observed when PU is used as thermal insulation, while the greater loss when EPS is used. The three materials PU, EPS, and GW registered a temperature of 45°C, at a simulation time of 3 h, 1.5 h, and 45 min, respectively.
1. The document describes an experiment investigating the use of staggered slots upstream of a nozzle guide vane cascade to simulate combustor-turbine leakage flow and improve film cooling effectiveness on the endwall surface.
2. Pressure sensitive painting (PSP) technique was used to measure film cooling effectiveness distributions on the endwall. The experiment tested different blowing ratios and found that staggered slots increased film cooling effectiveness along the pitchwise direction and developed a larger cooled region towards the suction side at higher blowing ratios.
3. The advantage of the staggered slots was apparent near the inlet area at low blowing ratios but their influence was only detected downstream at higher blowing ratios, as the coolant film weakened along the axial chord at low
HEAT TRANSFER DURING MULTI SWIRL JET IMPINGEMENT: EXPERIMENTATIONIAEME Publication
Of the Active Cooling Techniques, Jet impingement achieves high localized heat
transfer rates. Introduction of swirl is one of the methods of augmentation of heat
transfer rates. The current work aims at verifying the expression derived in our
previous work experimentally. Three cases, for which simulations were performed
previously, are executed. The required ducts are manufactured by additive
manufacturing. Thermistors are used for measuring temperatures. Anemometer is
used to monitor air flow rates. Smoke tests are executed to demonstrate the generation
of swirl and then experimentation is executed to study the heat transfer
characteristics. The experimental results are in agreement with those of simulation
results
CFD Simulation on Gas turbine blade and Effect of Hole Shape on leading edge ...IJMER
International Journal of Modern Engineering Research (IJMER) is Peer reviewed, online Journal. It serves as an international archival forum of scholarly research related to engineering and science education.
International Journal of Modern Engineering Research (IJMER) covers all the fields of engineering and science: Electrical Engineering, Mechanical Engineering, Civil Engineering, Chemical Engineering, Computer Engineering, Agricultural Engineering, Aerospace Engineering, Thermodynamics, Structural Engineering, Control Engineering, Robotics, Mechatronics, Fluid Mechanics, Nanotechnology, Simulators, Web-based Learning, Remote Laboratories, Engineering Design Methods, Education Research, Students' Satisfaction and Motivation, Global Projects, and Assessment…. And many more.
This document summarizes an experimental investigation into the effects of nonperiodic inlet rotating flow on endwall film cooling in neighboring turbine passages. The experiment compares film cooling effectiveness for three configurations of anticlockwise rotating inlet flow, analyzed using pressure-sensitive painting. Key findings include: 1) Inlet rotating flow influences effectiveness upstream, especially from leakage flows. 2) Effectiveness differs between passages depending on rotating flow core position. 3) Downstream effectiveness is also partly influenced by upstream rotating flow. Rotating inlet flow introduces challenges for film cooling design between neighboring passages in gas turbines.
Experimental Investigation of a Dimpled Plate by Natural Convection Heat Tran...IRJET Journal
This document summarizes previous research on using dimpled surfaces to enhance heat transfer via natural convection. It begins by defining natural convection and explaining how dimpled surfaces promote turbulence and vortex formation, augmenting heat transfer. The document then reviews several studies that experimentally investigated heat transfer over dimpled plates and tubes. Most found that heat transfer increased with dimple density, depth, and Reynolds number. The objectives of the proposed new study are to analyze heat transfer from vertically heated dimpled plates with variations in dimple shape, size, and arrangement. It is hypothesized that dimpled plates will enhance thermal performance over smooth plates through increased surface area and reduced flow separation.
This document summarizes an experimental investigation into the effects of trailing edge discharge cooling on the film cooling effectiveness of a turbine nozzle guide vane endwall. The study uses pressure sensitive paint to measure film cooling effectiveness on an endwall downstream of turbine blade trailing edges with discharge holes at compound angles. It examines the interaction between coolant from the endwall and trailing edge, referred to as "phantom cooling", and how blowing ratio and compound angle configuration affect film cooling performance. The experiments were conducted on a scale model turbine nozzle guide vane cascade with Reynolds number of 3.5×105 and inlet Mach number of 0.1 while varying the blowing ratio from 0.7 to 1.3 and compound angle of the trailing edge holes.
EFFECT OF LOWERING CONDENSING SURFACE TEMPERATURE ON THE PERFORMANCE OF SOLAR...IAEME Publication
In the present work an attempt has been made to study the effect of increasing temperature difference between evaporating surface and condensing surface on the performance of solar distillation system. An indoor simulation study has been performed on a constant temperature bath.
In order to increase the temperature difference between evaporating water surface and the condensing surface, the condensing surface temperature has been reduced by putting ice on the glass cover. It is observed that a maximum of 205 % rise in distillate is obtained by 54 % reduction in the
condensing surface temperature for constant temperature of the evaporating water at 50 0C.
Computational analysis for different characteristics of the circular microcha...IRJET Journal
This document summarizes research on computational analysis of flow characteristics in circular microchannels under low Reynolds number conditions. It discusses how a variable diameter design can improve flow rate and heat dissipation from electronic chips. The document reviews several past studies on microchannel flow and heat transfer. It is found that increasing the microchannel diameter increases heat dissipation rate, with a proposed design improving flow rate and heat removal for chip cooling.
The document studied the effect of various operating parameters on the heat transfer coefficient in a gas-solid fluidized bed using a horizontal heat transfer probe. Experiments were conducted in a fluidized bed with different particle sizes, bed inventories, heat fluxes, and air velocities. The results showed that the heat transfer coefficient increased with air velocity and bed inventory, but decreased with particle size. The heat transfer coefficient was also directly proportional to the applied heat flux. The study provides insights into heat transfer in gas-solid fluidized beds and how it is impacted by key operating parameters.
This document summarizes an experimental investigation into the effect of turbine phantom cooling on the suction side of a nozzle guide vane. Phantom cooling refers to coolant injected from the endwall that moves toward the airfoil suction side, providing a secondary cooling effect. The study uses pressure sensitive paint to measure film cooling effectiveness on a scale model turbine vane under different blowing ratios and incidence angles. It finds that incidence angle can alter the direction of coolant jets on the pressure side and change film cooling effectiveness distributions on the airfoil suction side.
This document summarizes a study that developed a mathematical model to simulate the heat transfer during the collision of a liquid Al-33 wt.% Cu droplet impacting a 304 stainless steel substrate. The model simultaneously considers fluid flow and heat transfer in the liquid droplet, surrounding gas, and substrate, including the contact resistance between the liquid alloy and substrate. Simulation results correctly predicted the total droplet spread and variation in interlamellar spacing along the droplet radius, matching experimental measurements. The comprehensive model incorporates many factors influencing droplet solidification, including cooling during flight, fluid flow accounting for surface tension, coupled solidification and heat transfer, and variation of physical properties with temperature.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
Study on Air-Water & Water-Water Heat Exchange in a Finned Tube ExchangerAnamika Sarkar
Heat exchange characteristics between hot and cold water as well as cold air and hot water have been investigated in a finned tube heat exchanger. The exchanger was operated in both parallel and counter-flow modes. For water-water heat exchange, the tube side (hot water) fluid flow rate was varied to observe the effects on heating the cold water. Conversely, for air-water system, the shell side (cold air) flow rate was varied to evaluate the cooling effectiveness of air in the finned tube exchanger. COMSOL Multiphysics 5.6 was used to simulate the system in 3-D mode, and the temperature profiles along with heat flux and velocity streamlines were evaluated. The NTU and effectiveness for varying fluid flow rates for both water-water and air-water systems were calculated. NTU values were considerably higher for air-water heat exchange and showed a decreasing trend with increasing fluid flow rate. To ascertain the reliability of the simulation models, the experimental and simulated results were compared. To evaluate the performance of the fins, the fin efficiencies and effectivenesses were calculated and the values were notably higher in case of air-water system. This is consistent with established literature. Also, increasing shell-side fluid flow rate led to a reduction in fin efficiency and effectiveness, which is again consistent with literature.
Effect of non uniform heat source for the ucm fluid over a stretching sheet w...IAEME Publication
This document summarizes a study on the effect of a non-uniform heat source on fluid flow over a stretching sheet with an applied magnetic field. The fluid is modeled as an upper-convected Maxwell (UCM) fluid. Similarity transformations are used to reduce the governing non-linear partial differential equations to an ordinary differential equation, which is then solved numerically using a fourth-order Runge-Kutta method. Graphical results are presented showing the effects of various parameters like the elastic parameter, Eckert number, magnetic parameter, and non-uniform heat source on the velocity and temperature profiles. The key findings are that a non-uniform heat sink provides more effective cooling than a heat source, and increasing the elastic
International Journal of Engineering and Science Invention (IJESI) is an international journal intended for professionals and researchers in all fields of computer science and electronics. IJESI publishes research articles and reviews within the whole field Engineering Science and Technology, new teaching methods, assessment, validation and the impact of new technologies and it will continue to provide information on the latest trends and developments in this ever-expanding subject. The publications of papers are selected through double peer reviewed to ensure originality, relevance, and readability. The articles published in our journal can be accessed online.
This document proposes methods for generating electricity from speed breakers. It discusses 5 classifications of speed breaker power generators that use different mechanisms: 1) a chain drive mechanism, 2) a rack and pinion system, 3) direct use of the load through a reciprocating device, 4) a translator and stator topology, and 5) a pressure lever mechanism. The document also outlines the advantages of using speed breakers for power generation such as low cost and maintenance and being a renewable source. Some challenges are also noted such as selecting a suitable generator and dealing with rain damage.
Cassava waste water was used as an admixture to replace distilled water in ratios of 5%, 10%, 15%, and 20% for producing sandcrete blocks. 60 sandcrete blocks of size 450mm x 150mm x 225mm were produced with different admixture ratios and a control with 0% admixture. The blocks were cured for 7, 14, 21, and 28 days and then tested for moisture content, specific gravity, water absorption, and compressive strength. Test results showed that blocks with 20% cassava waste water admixture met the minimum compressive strength requirement of 3.30 N/mm2 set by Nigerian standards, indicating the potential of cassava waste water to improve sandcrete block quality and
The document presents a theorem on random fixed points in metric spaces. It begins with introductions to fixed point theory, random fixed point theory, and relevant definitions. The main result is Theorem 3.1, which proves that if a self-mapping E on a complete metric space X satisfies certain contraction conditions involving parameters between 0 and 1, then E has a unique fixed point. The proof constructs a Cauchy sequence that converges to the unique fixed point. The document contributes to the study of random equations and random fixed point theory, which has applications in nonlinear analysis, probability theory, and other fields.
1. The document discusses applying multi-curve reconstruction technology to seismic inversion to improve accuracy and reliability. It focuses on reconstructing SP and RMN curves from well logs that are affected by various distortions.
2. The process of reconstructing the curves involves removing baseline drift, standardizing values, applying linear filtering, and fitting the curves. This removes interference and retains valid lithological information.
3. Reconstructing high quality curves improves the resolution and credibility of seismic inversion results. The method is shown to effectively predict sand distribution with little error.
This document compares the performance of a Minimum-Mean-Square-Error (MMSE) adaptive receiver and a conventional Rake receiver for receiving Ultra-Wideband (UWB) signals over a multipath fading channel. It first describes the UWB pulse shapes and channel model used, including the 6th derivative of the Gaussian pulse and the IEEE 802.15.3a modified Saleh-Valenzuela channel model. It then discusses the Direct-Sequence and Time-Hopping transmission and multiple access schemes for UWB. The document presents the receiver structures for the MMSE adaptive receiver and Rake receiver and compares their performance using MATLAB simulations.
This document summarizes a study on establishing logging interpretation models for reservoir parameters like porosity, permeability, oil saturation, and gas saturation in the Gaotaizi Reservoir of the L Oilfield. Models were developed using core data from 4 wells and include:
1) A porosity model relating acoustic travel time to porosity with an error of 0.92%
2) A permeability model relating permeability to porosity with an error of 0.31%
3) An oil saturation model using resistivity data with empirically determined parameters
4) A method to determine original gas saturation from mercury injection data.
Application of the models improved interpretation precision and allowed recalculation of oil and gas reserves for the
This document discusses predicting spam videos on social media platforms using machine learning. It proposes using attributes like number of likes, comments, and view count to classify videos as spam or not spam. A predictive algorithm is developed that uses threshold values for attributes and natural language processing of comments to classify videos. Testing of the algorithm on a dataset achieved a spam prediction precision of 93.6%. Issues with small datasets decreasing accuracy are also discussed, along with continuing work to address this issue.
1) The study experimentally evaluated the compatibility relationship between polymer solutions and oil layers through core flooding tests with different permeability cores.
2) The results showed that injection rate decreased with increasing polymer concentration and molecular weight, and increased with permeability.
3) Based on the results, boundaries for injection capability were established and a compatibility chart was proposed to guide polymer solution selection for different sedimentary microfacies in the field based on permeability and pore size.
1. The document discusses the identification of lithologic traps in the D3 Member of the Gaonan Region using seismic attribute analysis, acoustic impedance inversion, and sedimentary microfacies analysis.
2. Several lithologic traps were identified in the I and II oil groups of the D3 Member, with the largest trap located between wells G46 and G146X1 covering an area of about 2.35 km2.
3. Impedance inversion, seismic attribute analysis, and sedimentary microfacies characterization using 3D seismic data helped determine the location and development of effective lithologic traps in the thin sandstone-shale interbeds of the target stratum.
This document examines using coal ash as a partial replacement for cement in concrete. Coal ash was substituted for cement at rates of 5%, 10%, and 15% by weight. Testing found that concrete with a 5% substitution of coal ash exhibited only a slight decrease in compressive strength of 2% at 28 days while gaining improved workability. Higher substitution rates of 10% and 15% coal ash led to greater decreases in compressive and tensile strength. The study concludes that a 5% substitution of coal ash for cement provides benefits of reduced cost and improved workability with minimal strength impacts, representing an effective use of a waste material that addresses sustainability.
Accounting professional judgment involves handling accounting events and compiling financial reports according to regulations and standards. However, professional judgment is sometimes manipulated to distort accounting information. The document discusses three ways manipulation occurs: 1) abandoning accounting principles, 2) optional changes to accounting policies, and 3) abuse of accounting estimates. The causes of manipulation include distorted motivations from corporate governance issues and catering to various stakeholder interests. Strengthening supervision and improving the accounting system are proposed to manage manipulation of professional judgment.
The document discusses research on the distribution of oil and water in the eastern block of the Chao202-2 area in China. It establishes standards for identifying oil, poor oil, dry, and water layers using well logging data. Analysis shows structural reservoirs are dominant and fault and sand body configuration control oil-water distribution. Oil-water distribution varies between fault blocks from "up oil, bottom water" to "up water, bottom oil" depending on structure and sand body development.
The document describes an intelligent fault diagnosis system for reciprocating pumps that uses pressure and flow signals as inputs. It consists of hardware for data acquisition and a software system for signal processing, feature extraction, and fault diagnosis using wavelet neural networks. The system was able to accurately diagnose three main fault types - seal ring faults, valve damage, and spring faults - based on differences observed in the pressure curves. Testing on over 12 samples of each fault type achieved a correct diagnosis rate of over 94%. The system provides a fast and effective means of remotely monitoring reciprocating pumps and identifying faults.
This document discusses the application of meta-learning algorithms in banking sector data mining for fraud detection. It proposes using Classification and Regression Tree (CART), AdaBoost, LogitBoost, Bagging and Dagging algorithms for classification of banking transaction data. The experimental results show that Bagging algorithm has the best performance with the lowest misclassification rate, making it effective for banking fraud detection through data mining. Data mining can help banks detect patterns for applications like credit scoring, payment default prediction, fraud detection and risk management by analyzing customer transaction history and loan details.
This document presents a numerical solution for unsteady heat and mass transfer flow past an infinite vertical plate with variable thermal conductivity, taking into account Dufour number and heat source effects. The governing equations are non-linear and coupled, and were solved numerically using an implicit finite difference scheme. Various parameters, including Dufour number and heat source, were found to influence the velocity, temperature, and concentration profiles. Skin friction, Nusselt number, and Sherwood number were also calculated.
The document discusses methods for obtaining a background image using depth information from a depth camera to more accurately extract foreground objects. It finds that accumulating depth images and taking the median value at each pixel provides the most accurate background image. The accuracy of three methods - average, median, and mode - are evaluated using simulated depth data of a captured plane. The median method provides the best results, followed by average, while mode performs worst. More accumulated images provide a more accurate background image across all methods.
This document presents a mathematical model for determining the minimum overtaking sight distance (OSDm) required for an ascending vehicle to safely pass another slower vehicle on a single lane highway with an incline. It defines sight distance, stopping sight distance, perception-reaction time and derives equations to calculate the reaction distance (d1), overtaking distance (d2), vehicle travel distance during overtaking (d3), and total minimum OSDm based on vehicle characteristics, road geometry, and coefficients of friction. The safe overtaking zone is defined as 3 times the minimum OSDm. The model accounts for effects of slope angle and aims to satisfy laws of mechanics for overtaking maneuvers on inclined two-way single lane highways.
This document discusses a novel technique for better analysis of ice properties using Kalman filtering. It summarizes previous research on sea ice segmentation using SAR imagery and dual polarization techniques. It proposes using an automated SAR algorithm along with Kalman filtering to more accurately detect sea ice properties from RADARSAT1 and RADARSAT2 imagery data. The document reviews techniques for image segmentation, dual polarization, PMA detection, and related work on sea ice classification using statistical ice properties, edge preserving region models, and object extraction methods.
This document summarizes a study on the bioaccumulation of heavy metals in bass fish (Morone Saxatilis) caught at Rodoni Cape in the Adriatic Sea in Albania. Samples of bass fish were collected from five sites and analyzed for mercury, lead, and cadmium levels in their muscles. The concentrations of heavy metals varied between fish and sites but were below international limits for human consumption. While the fish were found to be safe for eating, the study recommends continuous monitoring of metal levels in fish from the area due to various factors that can influence metal uptake over time.
This document discusses optimal maintenance policies for repairable systems with linearly increasing hazard rates. It considers a system with a constant repair rate and predetermined availability requirement. There are two maintenance policies: corrective maintenance only, and preventive maintenance at set time intervals. The goal is to determine the preventive maintenance interval that guarantees the availability requirement at minimum cost. Equations are developed to calculate the availability under each policy and the optimal preventive maintenance interval based on both availability and cost. A numerical example is provided to demonstrate the decision process in determining the optimal policy.
Alt. GDG Cloud Southlake #33: Boule & Rebala: Effective AppSec in SDLC using ...James Anderson
Effective Application Security in Software Delivery lifecycle using Deployment Firewall and DBOM
The modern software delivery process (or the CI/CD process) includes many tools, distributed teams, open-source code, and cloud platforms. Constant focus on speed to release software to market, along with the traditional slow and manual security checks has caused gaps in continuous security as an important piece in the software supply chain. Today organizations feel more susceptible to external and internal cyber threats due to the vast attack surface in their applications supply chain and the lack of end-to-end governance and risk management.
The software team must secure its software delivery process to avoid vulnerability and security breaches. This needs to be achieved with existing tool chains and without extensive rework of the delivery processes. This talk will present strategies and techniques for providing visibility into the true risk of the existing vulnerabilities, preventing the introduction of security issues in the software, resolving vulnerabilities in production environments quickly, and capturing the deployment bill of materials (DBOM).
Speakers:
Bob Boule
Robert Boule is a technology enthusiast with PASSION for technology and making things work along with a knack for helping others understand how things work. He comes with around 20 years of solution engineering experience in application security, software continuous delivery, and SaaS platforms. He is known for his dynamic presentations in CI/CD and application security integrated in software delivery lifecycle.
Gopinath Rebala
Gopinath Rebala is the CTO of OpsMx, where he has overall responsibility for the machine learning and data processing architectures for Secure Software Delivery. Gopi also has a strong connection with our customers, leading design and architecture for strategic implementations. Gopi is a frequent speaker and well-known leader in continuous delivery and integrating security into software delivery.
GraphSummit Singapore | The Art of the Possible with Graph - Q2 2024Neo4j
Neha Bajwa, Vice President of Product Marketing, Neo4j
Join us as we explore breakthrough innovations enabled by interconnected data and AI. Discover firsthand how organizations use relationships in data to uncover contextual insights and solve our most pressing challenges – from optimizing supply chains, detecting fraud, and improving customer experiences to accelerating drug discoveries.
Encryption in Microsoft 365 - ExpertsLive Netherlands 2024Albert Hoitingh
In this session I delve into the encryption technology used in Microsoft 365 and Microsoft Purview. Including the concepts of Customer Key and Double Key Encryption.
Dr. Sean Tan, Head of Data Science, Changi Airport Group
Discover how Changi Airport Group (CAG) leverages graph technologies and generative AI to revolutionize their search capabilities. This session delves into the unique search needs of CAG’s diverse passengers and customers, showcasing how graph data structures enhance the accuracy and relevance of AI-generated search results, mitigating the risk of “hallucinations” and improving the overall customer journey.
UiPath Test Automation using UiPath Test Suite series, part 5DianaGray10
Welcome to UiPath Test Automation using UiPath Test Suite series part 5. In this session, we will cover CI/CD with devops.
Topics covered:
CI/CD with in UiPath
End-to-end overview of CI/CD pipeline with Azure devops
Speaker:
Lyndsey Byblow, Test Suite Sales Engineer @ UiPath, Inc.
Full-RAG: A modern architecture for hyper-personalizationZilliz
Mike Del Balso, CEO & Co-Founder at Tecton, presents "Full RAG," a novel approach to AI recommendation systems, aiming to push beyond the limitations of traditional models through a deep integration of contextual insights and real-time data, leveraging the Retrieval-Augmented Generation architecture. This talk will outline Full RAG's potential to significantly enhance personalization, address engineering challenges such as data management and model training, and introduce data enrichment with reranking as a key solution. Attendees will gain crucial insights into the importance of hyperpersonalization in AI, the capabilities of Full RAG for advanced personalization, and strategies for managing complex data integrations for deploying cutting-edge AI solutions.
In the rapidly evolving landscape of technologies, XML continues to play a vital role in structuring, storing, and transporting data across diverse systems. The recent advancements in artificial intelligence (AI) present new methodologies for enhancing XML development workflows, introducing efficiency, automation, and intelligent capabilities. This presentation will outline the scope and perspective of utilizing AI in XML development. The potential benefits and the possible pitfalls will be highlighted, providing a balanced view of the subject.
We will explore the capabilities of AI in understanding XML markup languages and autonomously creating structured XML content. Additionally, we will examine the capacity of AI to enrich plain text with appropriate XML markup. Practical examples and methodological guidelines will be provided to elucidate how AI can be effectively prompted to interpret and generate accurate XML markup.
Further emphasis will be placed on the role of AI in developing XSLT, or schemas such as XSD and Schematron. We will address the techniques and strategies adopted to create prompts for generating code, explaining code, or refactoring the code, and the results achieved.
The discussion will extend to how AI can be used to transform XML content. In particular, the focus will be on the use of AI XPath extension functions in XSLT, Schematron, Schematron Quick Fixes, or for XML content refactoring.
The presentation aims to deliver a comprehensive overview of AI usage in XML development, providing attendees with the necessary knowledge to make informed decisions. Whether you’re at the early stages of adopting AI or considering integrating it in advanced XML development, this presentation will cover all levels of expertise.
By highlighting the potential advantages and challenges of integrating AI with XML development tools and languages, the presentation seeks to inspire thoughtful conversation around the future of XML development. We’ll not only delve into the technical aspects of AI-powered XML development but also discuss practical implications and possible future directions.
A tale of scale & speed: How the US Navy is enabling software delivery from l...sonjaschweigert1
Rapid and secure feature delivery is a goal across every application team and every branch of the DoD. The Navy’s DevSecOps platform, Party Barge, has achieved:
- Reduction in onboarding time from 5 weeks to 1 day
- Improved developer experience and productivity through actionable findings and reduction of false positives
- Maintenance of superior security standards and inherent policy enforcement with Authorization to Operate (ATO)
Development teams can ship efficiently and ensure applications are cyber ready for Navy Authorizing Officials (AOs). In this webinar, Sigma Defense and Anchore will give attendees a look behind the scenes and demo secure pipeline automation and security artifacts that speed up application ATO and time to production.
We will cover:
- How to remove silos in DevSecOps
- How to build efficient development pipeline roles and component templates
- How to deliver security artifacts that matter for ATO’s (SBOMs, vulnerability reports, and policy evidence)
- How to streamline operations with automated policy checks on container images
Observability Concepts EVERY Developer Should Know -- DeveloperWeek Europe.pdfPaige Cruz
Monitoring and observability aren’t traditionally found in software curriculums and many of us cobble this knowledge together from whatever vendor or ecosystem we were first introduced to and whatever is a part of your current company’s observability stack.
While the dev and ops silo continues to crumble….many organizations still relegate monitoring & observability as the purview of ops, infra and SRE teams. This is a mistake - achieving a highly observable system requires collaboration up and down the stack.
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Welcome to UiPath Test Automation using UiPath Test Suite series part 6. In this session, we will cover Test Automation with generative AI and Open AI.
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Throughout the session, participants will discover how this synergy empowers testers to automate repetitive tasks, enhance testing accuracy, and expedite the software testing life cycle. Topics covered include the seamless integration process, practical use cases, and the benefits of harnessing AI-driven automation for UiPath testing initiatives. By attending this webinar, testers, and automation professionals can gain valuable insights into harnessing the power of AI to optimize their test automation workflows within the UiPath ecosystem, ultimately driving efficiency and quality in software development processes.
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2. Understanding how this integration enhances test automation within the UiPath platform
3. Practical demonstrations
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UiPath integration with generative AI
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UiPath Test Automation using UiPath Test Suite series, part 6
H05324358
1. IOSR Journal of Engineering (IOSRJEN) www.iosrjen.org
ISSN (e): 2250-3021, ISSN (p): 2278-8719
Vol. 05, Issue 03 (March. 2015), ||V2|| PP 43-58
International organization of Scientific Research 43 | P a g e
Numerical and Experimental Investigation on Frost Formation on
Cold Cylinders
Kamal A. R. Ismail1
, Fatima A. Morais Lino1
, Carlos T. Salinas1
, Luiz Vicente
Scalon2
, Raquel da Cunha Ribeiro da Silva1
1
Department of Energy, Faculty of Mechanical Engineering, State University of Campinas, UNICAMP, CEP
13083-860, Campinas (SP), Brazil. Phone: +55 19 35213376; Fax: +55 19 32893722.
2
Depto de Engenharia Mecânica-FEB, Av. Luiz E. Carrijo Coube nº.14-01, Vargem Limpa ,17.033-360 -
Bauru/ SP.
Abstract:This paper presents the results of a study to develop a fast calculation routine which enables the
prediction of the frost layer growth and the deposition velocity in terms of the surface temperature of the cold
body, the rate of flow of the humid air and the rate of flow heat transfer and mass transfer equation for the flow
of wet air around a circular cylinder are formulated and solved and the results are presented in function of the
surface temperature, mass flow rate of the humid air and the mass flow rate of the working fluid. In order to
validate the model and the numerical predictions, an experimental rig is constructed and adequately
instrumented. Experiments were realized and the results were composed with the numerical predictions to
confirm the validity of the model.
Keywords- Frost; Frost predictions, Frost thickness; modeling of frost; measurements of frost
I. INTRODUCTION AND BIBLIOGRAPHIC REVIEW
When humid air passes over cold surfaces the liquid particles are deposited over the surface in the form
of crystals by complicated mechanisms of heat and mass transfer forming a porous layer. If the process of frost
deposition continues for long periods this may lead to the formation of thick glacial layer of frost which impairs
the performance of the equipment and increases the pressure losses. In these cases the formed frost may be
removed by a variety of methods causing additional heat gains and the usual undesirable interruption of the
cooling process. For these and other reasons it is necessary to study deeply the process of frost formation to be
able to operate the equipments efficiently and for long periods.
One of the first experimental studies on frost formation was realized by [1] in which the effects on the heat
transfer and pressure drop were evaluated [2] estimated the effects of the frost growth on the energy losses in air
conditioning and refrigeration systems and found that about 20% of the total energy is spent in the defrost
process. Other important experimental contributions are due to [3],[4],[5],[6], [7] and [8].
Mau et al. [9] reported data and empirical correlations of the frost growth and its properties in terms of the
temperature of the flat plate, air temperature, humidity, and velocity.
Lee and Ro [10] studied the frost formation on the surface of a horizontal cylinder in a wet air stream and
obtained results of the heat transfer flow rate around the cylinder, the effective thermal conductivity of the frost
and the temperature distribution around the cylinder. Yang and Lee [11] proposed correlations for the frost
deposition on the surface of the cylinder of the frost thickness, density, temperature of the surface of the frost
layer.
The literature survey shows that during the last fifty years many models were proposed to describe the
phenomenon of frost formation as the model due to [3] which is strongly based upon experimental data and
empirical equations. Parish and Sepsy [12] proposed a model to formulate the frost formation around a cylinder
which by the use of global balances in the equations of momentum, energy and concentration try to quantify and
evaluate the process of frost formation. The model proposed by Jones and Parker [13] uses global balances and
considers the variation of the internal properties of the frost layer which makes the balances more representative.
Hayashi et al.[14] elaborated a model which divides the process of frost formation into three successive periods,
where the first is the one dimensional growth of the crystals, the second period is for three dimensional growth
and the last period is the period of total development or nearly static growth.
Tokura et al. [7] elaborated a set of parameters which enables the determination of the effective thermal
conductivity. Aoki et al. [15] studied the third period of Hayashi et al. model in great details.
Sami and Duong [16] proposed modifications in Jones and Parker model by using local frost properties to obtain
better predictions. Padki et al. [17] proposed an approximate model for frost formation by the use of empirical
correlations to estimate the heat and mass film coefficients. Sherif [18] presented a transient semi-empirical
model for frost formation over a flat plate. The model estimates the surface temperature and the frost layer
2. Numerical and Experimental Investigation on Frost Formation on Cold Cylinders
International organization of Scientific Research 44 | P a g e
growth using existent correlations for the heat transfer coefficient and Lewis’ analogy to calculate the mass
transfer coefficient.
Tao et al. [19] proposed a frost formation model on a flat plate. The model is based upon the basic equations of
heat and mass transfer and empirical correlations. The model solves the problem of frost formation in two
stages, the first stage of short duration one dimensional crystal formation followed by the second stage which
uses the data from the first stage as entry values.
Scalon [20] solved the problem of frost formation over a vertical cylinder in a wet air stream. He used the
equations developed by [19], but differently from Tao et al., he solved the flow field equations to determine the
convection and diffusion coefficients between the flow and the surface of the frost layer.
Salinas [21] and Ismail and Salinas [22] studied the case of frost formation over a flat plate placed parallel to the
direction of wet air flow by using a formulation based upon the average volume local technique and were able to
calculate the local density, frost layer thickness, mass deposition rate and phases mass fraction. They compared
their results with available experimental and numerical data. Later Ismail and Salinas [22] extended their work
to treat the case of flow of humid air and frost deposition between two parallel plates.
Some recent experimental work was realized by [23] on the formation of frost on vertical cold cylinders of
different arrangements including the case of two cylinders in series and three cylinders in a triangular
geometrical arrangement.
This paper presents the results of an investigation to develop a calculation routine which enables the
prediction of the frost layer growth rate and the thickness of the frost layer under different operational
conditions of mass flow rate of the working fluid, the surface temperature of the cold surface and the mass flow
rate of the humid air. Experiments were realized on an experimental rig designed and instrumented to enable the
variation of the air flow rate, the secondary working fluid flow rate and its temperature. The frost interface
position was determined by a digital camera. The photographs were discretized to determine the real frost
interface position. The experimental frost thickness and the frost deposition velocity were used to validate the
numerical model and the numerical predictions.
II. FORMULATION OF THE PROBLEM
The mathematical model developed by [20] based upon [19] with some adaptation, was used in the
present work to describe the process of frost formation around a vertical cold cylinder placed in a wet air stream.
Accepting the model due to [19] ,at the moment is the most accepted model even it is not exact one, that the
process of frost formation can be divided into two stages, where the first stage is one dimensional crystal growth
followed by the second stage of interaction between neighboring crystals forming a porous matrix. Both Tao et
al. and [20] used an empirical parameter called the transition time taken as 2/3 of the transition time given by
[14]. The transition time is a parameter which indicates the transition predominance from one phase to the other,
given in Fig. 1.
Fig.1 Values of transition times in the range of -20°C the 0°C.
1.1 ONE DIMENSIONAL CRYSTAL GROWTH
In this stage ice nucleus are formed on the cold surface and grow in the vertical direction as a consequence of
the heat and mass transfer.
3. Numerical and Experimental Investigation on Frost Formation on Cold Cylinders
International organization of Scientific Research 45 | P a g e
Following the model proposed by [19], the crystal growth is normal to the surface as shows in Fig. 2. Applying
the energy equation on the element shown in Fig. 2.
Fig. 2 Physical model for the growth of the ice crystals, [19]
𝜌 𝑔 𝑐 𝑝,𝑔
𝜕𝑇
𝜕𝑡
𝜋
4
𝑑2
𝑑𝑟 − 𝜌 𝑔 𝜆
𝜋
4𝑑𝑡
𝑑 +
𝜕𝑑
𝜕𝑡
𝑑𝑡
2
− 𝑑2
𝑑𝑟 = 𝑞𝑟 + 𝑞𝑐𝑜𝑛𝑣 − 𝑞𝑟+𝑑𝑟 (1)
𝜌 𝑔 𝑐 𝑝,𝑔
𝜕𝑇
𝜕𝑡
𝜋
4
𝑑2
𝑑𝑟 − 𝜌 𝑔 𝜆
𝜋
4
2𝑑
𝜕𝑑
𝜕𝑡
𝑑𝑟 =
−𝑘 𝛽
𝜋
4
𝑑2 𝜕𝑇
𝜕𝑟
+ 𝜋 𝑑 𝑑𝑟 𝑇𝛾 − 𝑇𝛽 − 𝑘 𝑔
𝜋
4
𝑑2 𝜕𝑇
𝜕𝑟
+
𝜕
𝜕𝑟
𝑘 𝑔
𝜋
4
𝑑2 𝜕𝑇
𝜕𝑟
𝑑𝑟 (2)
𝜌𝑐 𝑝,𝑔 𝑑
𝜕𝑇
𝜕𝑡
= 4 𝑇𝛾 − 𝑇𝛽 +
1
𝑑
𝜕
𝜕𝑟
𝑘 𝑔 𝑑2
𝜕𝑇
𝜕𝑟
+ 2𝜌 𝑔 𝜆
𝜕𝑑
𝜕𝑡
𝜌𝑐 𝑝,𝑔 𝑑
𝜕𝑇
𝜕𝑡
= 4 𝑇𝛾 − 𝑇𝛽 + 2𝑘 𝑔
𝜕𝑑
𝜕𝑟
𝜕𝑇
𝜕𝑟
+ 𝑘 𝑔 𝑑
𝜕2 𝑇
𝜕𝑟2 + 2𝜌 𝑔 𝜆
𝜕𝑑
𝜕𝑡
(3)
Applying the mass diffusion equation one can obtain
𝜌 𝑔
𝜋
4𝑑𝑡
𝑑 +
𝜕𝑑
𝜕𝑡
𝑑𝑡
2
− 𝑑2
𝑑𝑟 = 𝑚 𝜋𝑑𝑑𝑟 𝑊𝛾 − 𝑊𝛽 (4)
𝜌 𝑔
𝜋
4
2𝑑
𝜕𝑑
𝜕𝑡
𝑑𝑟 = 𝑚 𝜋𝑑𝑑𝑟 𝑊𝛾 − 𝑊𝛽 (5)
Where 𝑊𝛽 indicates the concentration evaluated at the temperature 𝑇𝛽 of the solid phase and the result is:
𝜌 𝑔
𝜕𝑑
𝜕𝑡
= 2 𝑚 𝑊𝛾 − 𝑊𝛽 (6)
These two equations represent the model for the first stage. The initial and boundary conditions necessary to
solve this model are
When r =
𝑑 = 𝑑0 (7)
−𝜌𝜆𝑑0
𝜕𝛿
𝜕𝑡
= 𝑘 𝑔 𝑑0
𝜕𝑇
𝜕𝑟 𝛿
+ 𝑑0 𝑇∞ − 𝑇𝑠
𝜕𝑇
𝜕𝑟 𝛿
=
𝑘 𝑠
𝑇∞ − 𝑇𝑠 +
𝜌 𝑔 𝜆
𝑘 𝑔
𝜕𝛿
𝜕𝑡
(8)
𝜌 𝑔 𝑑0
𝜕𝛿
𝜕𝑡
= 𝑚 𝑊∞ − 𝑊𝛿
𝜕𝛿
𝜕𝑡
=
𝑚
𝜌 𝑔
𝑊∞ − 𝑊𝛿 (9)
4. Numerical and Experimental Investigation on Frost Formation on Cold Cylinders
International organization of Scientific Research 46 | P a g e
When r = 0
𝑇𝑠 = 𝑇𝑒 (10)
𝜕𝑑
𝜕𝑡
= 0 (11)
When t = 0
𝑑 = 𝑑0 (12)
𝛿 = 𝛿0 (13)
𝑇𝛿 = 𝑇𝑒 (14)
It is worth mentioning here that the gas phase temperature 𝑇𝛾 is function of the ambient temperature 𝑇∞ and the
cylinder surface temperature 𝑇𝛽 , and the factor α whose value, according to [19], varies between zero for small
values of Reynolds number and 1 for large values of Reynolds number.
Thus
𝑇𝛾 = 𝛼𝑇∞ + (1 − 𝛼) (15)
Since the nucleation phenomenon is not well understood, we adopted here that each control volume contains
only one nucleus and hence we can write
𝑑0 = 𝐾𝑓𝑟𝑎𝑐
where 𝐾𝑓𝑟𝑎𝑐 is the size of the control volume along the direction parallel to the surface and has the values as
shown in Table 1 where Δ𝐶 is given in 𝑘𝑔/𝑚3
. It is important to mention that 𝛿0 cannot be zero because of
numerical reasons, and in the present study a small value given by 𝛿0 =
𝑑0
30
is adopted.
Table 1 Adopted values of 𝐾𝑓𝑟𝑎𝑐 .
Δ𝐶 < 0.008 0.008 < 𝛥𝐶
< 0.01
0.01 < 𝛥𝐶
< 0.013
Δ𝐶 > 0.013
0.5 0.65 0.7 0.75
The frost formation model divided the process artificially into two stages, but the real formation process is a
continuous one and the ice column are transformed into porous mesh of different structures. Hence a set of
coupling equations are necessary to adequate the results of the first stage of column structure as entries to the
second stage of frost formation.
These coupling equations are:
The volumetric fraction 𝜀𝛽,𝑖 is given by
𝜀𝛽,𝑖 =
𝜋𝑑 𝑖
2
4𝑙2 (16)
The temperature 𝑇𝑖can be evaluated by
𝑇𝑖 = 𝜀𝛽,𝑖 𝑇𝛽 + (1 − 𝜀𝛽,𝑖)𝑇𝛾 (17)
The density 𝜌𝑓,𝑖 and the specific heat 𝑐 𝑝,𝑖 are evaluated by
𝜌𝑓,𝑖 = 𝜀𝛽 ,𝑖 𝜌 𝛽 + (1 − 𝜀𝛽,𝑖)𝜌𝛾 (18)
𝑐 𝑝,𝑖 = 𝜀𝛽,𝑖 𝑐 𝑝,𝛽,𝑖 + (1 − 𝜀𝛽 ,𝑖)𝑐 𝑝,𝛾,𝑖 (19)
5. Numerical and Experimental Investigation on Frost Formation on Cold Cylinders
International organization of Scientific Research 47 | P a g e
1.2 THE CRYSTALS SPREADING PHASE
As mentioned before, in this phase the crystals are spread over the cold surface forming a porous medium. This
model is subject to some restrictions such as heat and mass transfer are one dimensional;
- constant internal pressure in the porous medium;
- thermal equilibrium among the phases;
- dominant thermal diffusion in relation to convection; and,
- Saturated air in the porous medium.
Considering a control volume in the porous medium, as shown in Fig.3 one can write the energy balance in the
form
𝜌𝑓 𝑐 𝑝,𝑓
𝜕𝑇
𝜕𝑡
+ 𝑚 𝜆 =
𝜕
𝜕𝑟
𝑘 𝑒𝑓
𝜕𝑇
𝜕𝑟
(20)
The mass balance for a control volume
Fig. 3 Control volume representation in the porous medium after [19].
Phase 𝛾
𝜕𝜀 𝛾 𝑊
𝜕𝑡
=
𝜕
𝜕𝑟
𝐷𝑒𝑓
𝜕𝑊
𝜕𝑟
(21)
Phase β
𝜕𝜀 𝛽
𝜕𝑡
= 𝑚 = 𝑊 − 𝑊𝑠𝑎𝑡 (22)
Equations (20) to (22) represent the second stage model. By using adequate initial and boundary conditions
these equations can be solved.
It is important to mention that for the solution the equations (20) to (22) the coupling equations (16) to (19) are
used to adapt the results of the first stage to be used as entry values for the second stage.
The boundary conditions are:
On the surface of the cylinder r = 0,
𝑇𝑠 = 𝑇𝑒
𝜕𝜀 𝑑
𝜕𝑟
= 0
The conditions at the moving frost interface at
𝑟 = 𝛿
𝑚 𝑊∞ − 𝑊𝛿 = 𝐷𝑒𝑓,𝑠
𝜕𝑊
𝜕𝑟
+ 𝜌𝑓,𝑠
𝜕𝛿
𝜕𝑡
(23)
𝑇∞ − 𝑇𝑠 = 𝑘 𝑒𝑓
𝜕𝑇
𝜕𝑟
− 𝜌𝑓,𝑠 𝜆
𝜕𝛿
𝜕𝑡
(24)
𝜕𝜀 𝛿
𝜕𝑟
= 0
The relevant thermal properties of the frost and air are obtained from the literature as below:
The thermal conductivity 𝑘 𝑔 [24]
𝑘 𝑔 =
630
𝑇
[W/mK], where T in K. (25)
6. Numerical and Experimental Investigation on Frost Formation on Cold Cylinders
International organization of Scientific Research 48 | P a g e
The specific heat 𝑐 𝑝,𝑔 [24]
𝑐 𝑝,𝑔 = 2116.56 + 7.284510−3
𝑇 [kJ/kgK], where T in K. (26)
Specific volume 𝑣𝑔 [25]
𝑣𝑔 = 1.0907𝑥10−3
+ 1.4635𝑥10−3
𝑇[m³/kg], where T in K. (27)
The density 𝜌 𝑔 [16]
1
𝜌 𝑔
= 0.0010907 + 1.4635𝑥10−7
𝑇[kg/m³], where T in K. (28)
The properties of dry air are obtained from [25].
The thermal conductivity 𝑘 𝑎𝑟
𝑘 𝑎𝑟 = 0.001968 + 8.15𝑥10−5
𝑇 [W/mK], where T in K. (29)
The specific heat 𝑐 𝑝,𝑎𝑟
𝑐 𝑝,𝑎𝑟 = 1.004 [kJ/kgK], where T in K .(30)
The density 𝜌 𝑎𝑟
𝜌 𝑎𝑟 =
344.9
𝑇
[kg/m³], where T in K. (31)
The effective diffusion coefficient is evaluated using [19]
𝐷𝑒𝑓 = 𝜀 𝛾 𝐷(1 + 𝐹)[m²/s] (32)
where D is the binary diffusion coefficient evaluated from
𝐷 = 2.19
𝑇
𝑇0
1.81
10−5
[m²/s] (33)
The effective diffusion coefficient on the surface is
𝐷𝑒𝑓𝑓 = 𝜀 𝛾 𝐷 1 + 𝐹𝑠 [m²/s]
(34)
Fig. 4 Factors F and 𝐹𝑠 as a function of temperature, [19].
where F and Fs are given by [19] and shown in Fig. 4.
The saturation humidity of the air is
𝑊 = 0.6218
𝑃 𝑣𝑎𝑝 ,𝑠𝑎𝑡
𝑃 𝑡𝑜𝑡𝑎𝑙 −𝑃 𝑣𝑎𝑝 ,𝑠𝑎𝑡
= (35)
The saturation pressure at any position in the frost layer is evaluated from [17],
7. Numerical and Experimental Investigation on Frost Formation on Cold Cylinders
International organization of Scientific Research 49 | P a g e
ln 𝑃𝑣𝑎𝑝 ,𝑠𝑎𝑡 =
𝐶1
𝑇
+ 𝐶2 + 𝐶3 + 𝐶4 𝑇2
+ 𝐶5 𝑇3
+ 𝐶6 𝑇4
+ 𝐶7ln(𝑇) (36)
where
C1 = −5.674 535 9 103
C2 = 6.392 524 7
C3 = −9.677 843 0 10−3
C4 = 6.221 570 1 10−7
C5 = 2.074 782 5 10−9
C6 = −9.484 024 0 10−13
C7 = 4.1635019
Equation (36) is valid for the interval -100°C<T<0°C where T is in K and 𝑃𝑣𝑎𝑝 ,𝑠𝑎𝑡 is in Pa
The total specific volume is,
𝑣 = 1.611168. 10−2 𝑇
𝑃
1 +
𝑃 𝑣𝑎𝑝
𝑃
[m³/kg] (36a)
The value of the sublimation latent heat, [12]
𝜆 = 𝑣𝑎𝑝,𝑇 − 𝑖𝑐𝑒 ,𝑇 = −0.195386. 𝑇 𝑘 + 2837.77 [kJ/kg] (37)
The effective thermal conductivity is evaluated by using the model due to [24], where the frost is treated as a
porous medium of volumetric fraction given by
𝜀 =
𝜌 𝑔−𝜌 𝑓
𝜌 𝑔−𝜌 𝑎
(38)
The effective thermal conductivity is evaluated by
𝑘 𝑒𝑓 =
1
4
3𝜀𝑐 − 1 𝑘1 + 3𝑥 𝑐 − 1 𝑘 𝑢 + 3𝜀𝑐 − 1 𝑘1 + 3𝑥 𝑐 − 1 𝑘 𝑢
2 + 8 𝑘𝑙 𝑘 𝑢 (39)
Where
𝑘 𝑢 = 1 − 𝜀 𝑘 𝑏 + 𝜀𝑘 𝑐 (Upper limit)
𝑘1 = 1 − 𝜀 𝑘 𝑝 + 𝜀𝑘 𝑠 (Lower limit)
Let us define
𝑎 =
𝑘 𝑒,𝑎𝑟
𝑘𝑖𝑐𝑒
𝑘 𝑒,𝑎𝑟 = 𝑘 𝑎𝑟 +
𝑇𝑆 𝑘 𝑣
𝜀
𝑇𝑆 =
1
(1 + 𝐹𝑠)
where
(a) Contribution due to air bubbles (𝑘 𝑏 ):
𝑘 𝑏 = 𝑘 𝑔
1 − 2𝜀
1 − 𝑎
2 + 𝑎
1 + 𝜀
1 − 𝑎
2 + 𝑎
(b) Contribution due to the frost cylinders(𝑘 𝑐 ):
𝑘 𝑐 = (1 − 𝜀)𝑘 𝑔 + 𝜀𝑘 𝑒,𝑎𝑟
(c) Contribution due to the frost spheres(𝑘 𝑠):
𝑘 𝑠 = 𝑘 𝑔
3 + 𝜀(𝑎 − 1)
3 − 𝜀
𝑎 − 1
𝑎
(d) Contribution due to the flat plate frost(𝑘 𝑝 ):
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𝑘 𝑝 =
𝑘 𝑔 𝑘 𝑒,𝑎𝑟
1 − 𝜀 𝑘 𝑒,𝑎𝑟 + 𝜀𝑘 𝑔
The value of 𝜀𝑐 is given by the correlation obtained from experimental data:
𝜀𝑐 = 13.6(𝜀2 − 𝜀1)(𝜀 − 𝜀1)2
1 −
2
3
𝜀−𝜀1
𝜀3−𝜀1
+
𝜀−𝜀1
𝜀2−𝜀1
+
𝜀−𝜀1
2
2 𝜀3−𝜀1 𝜀2−𝜀1
Where
𝜀1 = 0.1726
𝑇
273.16
𝜀2 = 0.751
𝜀3 = 0.3𝑠𝑖𝑛
𝜋
2
1 −
𝑇
273.16
1 −
𝑇𝑒
273.16
If 𝜀 < 𝜀1, then 𝜀𝑐 = 0. The value of 𝑥 𝑐 is defined as: 𝑥 𝑐 = 1 − 𝜀𝑐 .
The equations of the first stage, the coupling equations and the equations of the second stage together
with the respective boundary and initial conditions were discretized by using the finite difference
approximation. The numerical program was written in C++ and the numerical tests were realized to optimize the
computational grid and make the results independent of the grid size. The value of dr was varied from 10-1
to 10-5
mm and dt from 10s to 10-4
s.
The predicted results were found to compare well with the experimental measurements for dr = 10-3
mm and dt
= 10-2
s, and hence these values were used for all the present calculations.
III. EXPERIMENTAL MEASUREMENTS
In order to validate the model and the numerical predictions, an experimental rig was constructed and
adequately instrumented, Fig.5. The experimental rig is composed of a wind tunnel with the test section made of
acrylic sheet of 10mm thickness where the cold tube was fixed vertically and fed by the secondary fluid circuit.
The air flow in the tunnel was controlled by varying the frequency of the driving motor, and the working section
was calibrated such that both its mean velocity and the air flow rate are obtained in terms of the frequency of the
driving motor. The humidity of the air was changed by using a commercial electric humidifier and the air was
usually maintained as fully saturated. The circulating secondary fluid flow rate was measured by a calibrated
orifice plate and its temperature at entry and exit of the cylinder were measured by calibrated thermocouples.
Fig. 5 Experimental rig.
The dry and wet bulb temperatures were measured before and after the test tube.
The deposition of frost on the surface of the cylinder was measured by photographing the cylinder by
means of a high speed digital camera fixed normal to the cylinder axis. A precision measuring scale was fixed
close to the cylinder and was always photographed together with the cylinder.
The uncertainty in the measurements and error propagation analysis were performed for all the experiments
realized and the final values are listed in Table 2.
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Table 2 Results of the uncertainty analysis
At the beginning of the frost deposition process the temperature gradient between the surface of the
cylinder and the air stream is big and consequently water droplets present in the wet air stream collide against
the cold surface of the cylinder forming ice crystals. As the process continues more ice crystals are deposited
over the cylinder surface forming a porous matrix. As the frost layer gets thicker it’s the thermal resistance
increases and the temperature difference decreases provoking the fusion of the solidified ice crystals and
changing it to the liquid phase. When this occurs, the thermal resistance decreases and the liquid layer freezes
and more ice particles are formed on the surface of the cylinder. This process is repeated many times and the
final result is the formation of a layer of very dense frost or a layer of glacial ice. Figs.6 a,b show images of the
frost porous layer and the frost glacial layer.
Fig. 6a Formation of the porous frost.
Fig. 6b Formation of the glacial frost.
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IV. RESULTS AND DISCUSSION
As was mentioned before some numerical tests were realized to establish the optimum computational
grids which make the numerical predictions independent of the grid size. The predicted test results were
compared with the experimental measurements. It was found that mmdr ³10
and sdt ²10
gave good
agreements with the experiments. Therefore these values were adopted for all the calculations.
Fig. 7 shows the variation of frost thickness with time and as function of the surface temperature of the cylinder.
As can be seen the lower the surface temperature of the cylinder the thicker the frost layer for the same
conditions and time.
Fig.7 Variation of the frost layer thickness due to variation of the cylinder surface temperature for
𝑉𝑎𝑟 = 0.03 𝑚3
/𝑠 and 𝑚𝑓𝑠𝑐 = 0.028
𝑘𝑔
𝑠
.
Fig.8 Variation of the frost deposition velocity due to variation of the cylinder surface temperature for 𝑉𝑎𝑟 =
0.03 𝑚3
/𝑠 and 𝑚𝑓𝑠𝑐 = 0.028
𝑘𝑔
𝑠
.
Fig.8. shows the variation of the frost deposition velocity with time and with the surface temperature of
the cylinder. As can be seen, the lower the surface temperature of the cylinder the higher the frost deposition
velocity. Also one can observe that the high initial frost deposition velocity due to the small initial thermal
resistance. As the time goes on more frost is deposited the surface of the cylinder causing the increase of
thermal resistance and consequently reducing of frost deposition velocity. The deposition of frost continues until
towards the end of the process where the frost layer is so thick and the thermal resistance is too high so that the
deposition velocity is very low and the frost deposition nearly stops.
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Fig.9 Variation of the frost thickness due to variation of the flow rate of the humid air for 𝑇𝑓𝑠𝑐 = −10 𝑜
𝐶 and
𝑚𝑓𝑠𝑐 = 0.028
𝑘𝑔
𝑠
.
Fig. 9 shows the growth of the frost layer thickness with time for various wet air mass flow rates. As can be seen
the increase of the wet air mass flow rate decreases of the frost layer thickness. This increase of the wet air mass
flow rate increases the shear action on the layer, tearing off liquid particles and carrying it away with the air
stream.
Fig.10 Variation of the frost deposition velocity due to variation of the flow rate of the humid air for 𝑇𝑓𝑠𝑐 =
−10 𝑜
𝐶 and 𝑚𝑓𝑠𝑐 = 0.028
𝑘𝑔
𝑠
.
The effect of the mass flow rate of humid air on the frost deposition velocity can be seen in Fig. 10. Where one
can verify that high air flow rate reduces the deposition velocity. This effect can be explained by the shearing
action of the high velocity, hence reducing the frost thickness and consequently the frost deposition velocity.
Fig.11 Variation of the frost thickness due to variation of the mass flow rate of the working fluid for 𝑇𝑓𝑠𝑐 =
−10 𝑜
𝐶 and 𝑚𝑓𝑠𝑐 = 0.028
𝑘𝑔
𝑠
.
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Fig. 11 shows the effect of increasing the mass flow rate of the secondary fluid on the frost thickness. It is found
that increasing the mass flow rate, leads to increase the internal heat transfer coefficient and hence reduces the
thermal resistance, increases the temperature gradient and the deposition of frost.
Fig. 12 Variation of the frost deposition velocity due to variation of the mass flow rate of the working fluid for
𝑇𝑓𝑠𝑐 = −13 𝑜
𝐶 and 𝑉𝑎𝑟 = 0.028
𝑘𝑔
𝑠
.
Fig. 12 shows that increasing the secondary mass flow rate, increases the internal heat transfer coefficient,
increases the heat removal rate and hence increases the deposition velocity.
Fig.13 Comparison between the predicted frost thickness and the experimental measurements.
Fig.13. shows a comparison between predicted frost thickness and the experimental measurements. As can be
seen the agreement is relatively good indicating that the model and the predicted results can be used for
preliminary analysis of the frost deposition problem.
Fig.14 shows the variation of the frost deposition velocity with time both numerically and experimentally. As
can be seen the agreement is good over the whole period.
Fig.14 Comparison between the predicted frost deposition velocity and the experimental measurements.
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Fig. 15 shows a comparison between the predicted frost thickness and frost deposition velocity and the
experimental measurements. As can be seen the agreement is good. One can observe some abrupt change in the
inclination of the numerically predicted thickness. This variation is only numerical due to the effect of the
coupling model. The same can be said in relation to Fig. 16, which shows the predicted frost deposition velocity
compared to the experimental measurements. One can observe the good agreement and the presence of the slight
kink due to the coupling model.
Fig.15 Comparison between numerical and experimental frost layer growth.
Fig.16 Comparison between numerical and experimental frost deposition velocity.
Fig.17 Effects of the humid air flow rate on the frost deposition rate for -10°C and 0.028kg/s.
0,02 0,04 0,06 0,08 0,10 0,12
1,2
1,4
1,6
1,8
2,0
2,2
2,4
2,6
2,8
3,0
3,2
3,4
3,6
Time 60 minutes
Time 100 minutes
Time 140 minutes
Thicknessoffrost(mm)
Humid air flow rate (m³/s)
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Fig.18 Effects of the humid air flow rate on the frost deposition rate for -10°C and 0.028kg/s.
Fig. 17 and 18 show the effect of the humid air mass flow rate on the frost thickness and deposition velocity. It
is found that the increase of the wet air mass flow rate leads reducing the frost thickness and the deposition
velocity because of the shearing action on the frost surface.
Fig. 19 Effects of temperature of the cold surface on the frost deposition rate for 0.03m³/s and 0.028kg/s.
Fig. 20 Effects of temperature of the cold surface on the frost deposition rate for 0.03m³/s and 0.028kg/s.
Fig. 19 shows the effect of the surface temperature of the cylinder on the thickness of the frost layer.
As can be seen lowering the surface temperature of the cylinder increases the temperature gradient and hence
increases the deposition of frost on the surface of the cylinder. As the time goes on the rate of deposition is
slowed down as can be seen from the decrease of the inclination of the deposition curve.
-20 -18 -16 -14 -12 -10
1,4
1,6
1,8
2,0
2,2
2,4
2,6
2,8
3,0
3,2
3,4
3,6
Thicknessoffrost[mm]
Temperature [°C]
Time 60 minutes
Time 100 minutes
Time 140 minutes
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Fig. 20 shows the effect of the cylinder surface temperature on the frost deposition velocity. As can be seen,
lowering the surface temperature leads to increase the deposition velocity.
Fig.21 Effects of mass flow rate of the secondary fluid on the frost deposition rate for -13°C and 0.03m³/s.
Fig.22 Effects of mass flow rate of the secondary fluid on the frost deposition rate for -13°C and 0.03m³/s.
Figs. 21 and 22 show the effect of increasing the secondary fluid mass flow rate. A can be seen increase the
secondary fluid mass flow rate increases the internal Reynolds number and hence the internal coefficient of heat
transfer. This leads to increasing the frost thickness and the frost deposition velocity.
V. CONCLUSIONS
Based upon the results and discussion, one can make the following conclusions.
1. The frost layer thickness and the frost deposition velocity decrease with the increase of the volumetric flow
rate of the wet air.
2. The decrease of the cylinder wall temperature increases the frost layer thickness and increases the frost
deposition velocity.
3. The increase of the mass flow rate of the secondary fluid circulating into the cold cylinder increases the
frost deposited thickness and the frost deposition velocity.
4. The comparisons between the numerical predictions and the experimental results show relatively good
agreement and thus validating the model and numerical predictions. This allows using the model for
preliminary evaluation of frost formation.
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VI. ACKNOWLEDGEMENTS
The authors wish to thank the CNPQ for the PQ research grant and the doctorate degree scholarship for the
second author.
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