- A numerical model was developed to simulate capillary tube performance in split air conditioners under varying outdoor temperatures.
- The model analyzed the effects of increasing ambient temperature from 35°C to 55°C on capillary tubes using refrigerants R22, R290, R407C, and R410A.
- The results showed that higher ambient temperatures increase the choking length of the capillary tube. R290 required the longest capillary tube lengths while R410A required the shortest.
Numerical Investigation of Mixed Convective Flow inside a Straight Pipe and B...iosrjce
The present study deals with a numerical investigation of steady laminar and turbulent mixed
convection heat transfer in a horizontal pipe and bend pipe using air as the working fluid.The thermal boundary
condition chosen is that of uniform temperature at the outer wall. Computations were performed to investigate
the effect of inlet Rayleigh number and Reynolds number in the velocity and temperature profile at inside of the
pipe. The secondary flow is more intense in the upper part of the cross-section. It increases throughout the
cross-section until its intensity reaches a maximum, and then it becomes weak at far downstream. For the
horizontal pipe the value of the L/D ratio becomes more than 10 the secondary flow effects are neutralized and
the velocity profile almost become constant throughout.
Heat Transfer Analysis of Refrigerant Flow in an Evaporator TubeIJMER
the paper aim is to presenting the heat transfer analysis of refrigerant flow in an evaporator
tube is done. The main objective of this paper is to find the length of the evaporator tube for a pre-defined
refrigerant inlet state such that the refrigerant at the tube outlet is superheated. The problem involves
refrigerant flowing inside a straight, horizontal copper tube over which water is in cross flow. Inlet
condition of the both fluids and evaporator tube detail except its length are specified. here pressure and
enthalpy at discrete points along the tube are calculated by using two-phase frictional pressure drop model.
Predicted values were compared using another different pressure drop model. A computer-code using
Turbo C has been developed for performing the entire calculation
NUMERICAL INVESTIGATION OF LAMINAR NANOFLUID FLOW IN MICRO CHANNEL HEAT SINKS IAEME Publication
The effect of using nanofluids on heat transfer and aerodynamics characteristics in rectangular shaped micro channel heat sink (MCHS) is numerically investigated for Reynolds number range of (100-400 ) and different value of heat flux (50 , 100, 150 ) / . In this study,the MCHS performance using tow type of nanofluid with volume
fraction 10% was used as a coolant is examined. The three-dimensional steady, laminar flow and heat transfer governing equations are solved using The computational fluid dynamics code (FLUENT). The MCHS performance is evaluated in terms of temperature profile, heat transfer,velocity profile, pressure drop and friction factor.
Conjugate Heat Transfer Analysis in a Cryogenic Microchannel Heat ExchangerIRJET Journal
This document presents a numerical analysis of conjugate heat transfer in a cryogenic microchannel heat exchanger. A counterflow rectangular microchannel printed circuit heat exchanger model is designed and simulated. Performance is investigated numerically with helium at cryogenic temperatures for Reynolds numbers less than 100 and varying material thermal conductivity ratios. Results show axial conduction affects performance at low Reynolds numbers. Effectiveness decreases with increasing axial conduction and increases with Reynolds number. Nusselt number and heat flux along the channels are also determined.
The document presents the results of calculations of parameters of turbulent fluid flow in a pipe with a circular cross-section. Graphs and mathematical functions show how total pressure, velocity, vorticity, turbulent length, dissipation, viscosity, energy, and time change along the length of the pipe for different mass flow rates. A transition from laminar to turbulent flow occurs at around 2/5 the length of the pipe from the inlet. Parameters generally increase with mass flow rate and distance along the pipe, while turbulent time decreases. Functions are given to describe the variation of each parameter within different sections of the pipe.
International Journal of Engineering and Science Invention (IJESI)inventionjournals
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.
Thermal analysis of various duct cross sections using altair hyperworks softwaresushil Choudhary
In this work thermal analysis and comparison of various duct cross sections is done computationally using Altair
Hyperworks Software. Simple Analytical results were obtained for conduction and convection through the ducts
which can be used to build up thermal circuit. The inner surface of all ducts is maintained at constant
temperature and ambient air is at certain temperature that is less than inner surface temperature of pipe. Due to
temperature difference heat will flow from higher temperature to lower temperature. Due to temperature
difference heat will flow from higher temperature to lower temperature. The material of pipe provides
conductive resistance and air provides convective resistance. Hence this is a mix mode of heat transfer. The heat
transfer takes place in one dimension only and properties are considered to be isotropic. The ducts are assumed
to be made of aluminium having known thermal conductivity and density. The surroundings of ducts have
known convective heat transfer coefficient and temperature. The results are obtained on hyperview which are for
heat flux, temperature gradient and grid temperature. The different characteristics can be obtained by varying the
material of the ducts.
This document summarizes a study on the thermal performance of a shell and tube heat exchanger using nanofluids. Finite volume modeling was used to analyze heat transfer and flow characteristics. Various nanofluids including Ag, Al2O3, CuO, SiO2, and TiO2 suspensions in water were tested and compared to pure water. The objectives were to analyze temperature profiles, heat transfer coefficients, pressure drops, and effectiveness. Results showed nanofluids had higher overall temperatures indicating more heat transfer compared to water alone. This study analyzed the potential for nanofluids to enhance heat exchanger performance.
Numerical Investigation of Mixed Convective Flow inside a Straight Pipe and B...iosrjce
The present study deals with a numerical investigation of steady laminar and turbulent mixed
convection heat transfer in a horizontal pipe and bend pipe using air as the working fluid.The thermal boundary
condition chosen is that of uniform temperature at the outer wall. Computations were performed to investigate
the effect of inlet Rayleigh number and Reynolds number in the velocity and temperature profile at inside of the
pipe. The secondary flow is more intense in the upper part of the cross-section. It increases throughout the
cross-section until its intensity reaches a maximum, and then it becomes weak at far downstream. For the
horizontal pipe the value of the L/D ratio becomes more than 10 the secondary flow effects are neutralized and
the velocity profile almost become constant throughout.
Heat Transfer Analysis of Refrigerant Flow in an Evaporator TubeIJMER
the paper aim is to presenting the heat transfer analysis of refrigerant flow in an evaporator
tube is done. The main objective of this paper is to find the length of the evaporator tube for a pre-defined
refrigerant inlet state such that the refrigerant at the tube outlet is superheated. The problem involves
refrigerant flowing inside a straight, horizontal copper tube over which water is in cross flow. Inlet
condition of the both fluids and evaporator tube detail except its length are specified. here pressure and
enthalpy at discrete points along the tube are calculated by using two-phase frictional pressure drop model.
Predicted values were compared using another different pressure drop model. A computer-code using
Turbo C has been developed for performing the entire calculation
NUMERICAL INVESTIGATION OF LAMINAR NANOFLUID FLOW IN MICRO CHANNEL HEAT SINKS IAEME Publication
The effect of using nanofluids on heat transfer and aerodynamics characteristics in rectangular shaped micro channel heat sink (MCHS) is numerically investigated for Reynolds number range of (100-400 ) and different value of heat flux (50 , 100, 150 ) / . In this study,the MCHS performance using tow type of nanofluid with volume
fraction 10% was used as a coolant is examined. The three-dimensional steady, laminar flow and heat transfer governing equations are solved using The computational fluid dynamics code (FLUENT). The MCHS performance is evaluated in terms of temperature profile, heat transfer,velocity profile, pressure drop and friction factor.
Conjugate Heat Transfer Analysis in a Cryogenic Microchannel Heat ExchangerIRJET Journal
This document presents a numerical analysis of conjugate heat transfer in a cryogenic microchannel heat exchanger. A counterflow rectangular microchannel printed circuit heat exchanger model is designed and simulated. Performance is investigated numerically with helium at cryogenic temperatures for Reynolds numbers less than 100 and varying material thermal conductivity ratios. Results show axial conduction affects performance at low Reynolds numbers. Effectiveness decreases with increasing axial conduction and increases with Reynolds number. Nusselt number and heat flux along the channels are also determined.
The document presents the results of calculations of parameters of turbulent fluid flow in a pipe with a circular cross-section. Graphs and mathematical functions show how total pressure, velocity, vorticity, turbulent length, dissipation, viscosity, energy, and time change along the length of the pipe for different mass flow rates. A transition from laminar to turbulent flow occurs at around 2/5 the length of the pipe from the inlet. Parameters generally increase with mass flow rate and distance along the pipe, while turbulent time decreases. Functions are given to describe the variation of each parameter within different sections of the pipe.
International Journal of Engineering and Science Invention (IJESI)inventionjournals
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.
Thermal analysis of various duct cross sections using altair hyperworks softwaresushil Choudhary
In this work thermal analysis and comparison of various duct cross sections is done computationally using Altair
Hyperworks Software. Simple Analytical results were obtained for conduction and convection through the ducts
which can be used to build up thermal circuit. The inner surface of all ducts is maintained at constant
temperature and ambient air is at certain temperature that is less than inner surface temperature of pipe. Due to
temperature difference heat will flow from higher temperature to lower temperature. Due to temperature
difference heat will flow from higher temperature to lower temperature. The material of pipe provides
conductive resistance and air provides convective resistance. Hence this is a mix mode of heat transfer. The heat
transfer takes place in one dimension only and properties are considered to be isotropic. The ducts are assumed
to be made of aluminium having known thermal conductivity and density. The surroundings of ducts have
known convective heat transfer coefficient and temperature. The results are obtained on hyperview which are for
heat flux, temperature gradient and grid temperature. The different characteristics can be obtained by varying the
material of the ducts.
This document summarizes a study on the thermal performance of a shell and tube heat exchanger using nanofluids. Finite volume modeling was used to analyze heat transfer and flow characteristics. Various nanofluids including Ag, Al2O3, CuO, SiO2, and TiO2 suspensions in water were tested and compared to pure water. The objectives were to analyze temperature profiles, heat transfer coefficients, pressure drops, and effectiveness. Results showed nanofluids had higher overall temperatures indicating more heat transfer compared to water alone. This study analyzed the potential for nanofluids to enhance heat exchanger performance.
This document discusses wellbore performance and flow modeling. It covers:
1) Single phase liquid, gas, and two phase flow models based on mechanical energy balance equations. Pressure drops are calculated considering elevation change, kinetic energy, and friction.
2) Methods for calculating friction factors including Fanning, Darcy, and Moody charts. Correlations for gas properties like viscosity and deviation factor are also presented.
3) Examples of calculating pressure drops in single phase liquid and gas flows. Numerical methods for solving gas flow equations are described.
4) Multiphase flow is more complex due to different flow regimes affecting pressure gradients. Models include homogeneous and separated flow approaches.
SPLIT SECOND ANALYSIS COVERING HIGH PRESSURE GAS FLOW DYNAMICS AT PIPE OUTLET...AEIJjournal2
A detailed investigation covering piped gas flow characteristics in high pressure flow conditions. Such flow analysis can be resolved using established mathematical equations known as the Fanno condition, which usually cover steady state, or final flow conditions. However, in real life, such flow conditions are
transient, varying with time. This paper uses CFD analysis providing a split second “snapshot” at what happens at the pipe outlet, and therefore, a closer understanding at what happens at the pipe’s outlet in high pressure gas flow condition
Numerical_Analysis_of_Turbulent_Momentum_and_Heat_Transfer_in_a_Rectangular_H...Nate Werner
- The document analyzes turbulent momentum and heat transfer in a rectangular helical duct using water and freon-12 as working fluids.
- It develops a 3D model of the helical duct geometry based on prior research. Simulations are run using ANSYS Fluent and CFX to analyze flow, temperature, and turbulence fields.
- The results show secondary flows developing with higher velocities near the outer wall. While some aspects agree with prior work, the simulations produce higher velocities and different vortex structures than expected. Thermal development also takes longer than velocity development.
New Microsoft Office PowerPoint PresentationSudhir Shinde
This document summarizes a seminar presentation on heat transfer via jet impingement. The presentation discusses how jet impingement is used to effectively remove large amounts of heat from surfaces, such as in cooling turbine blades and electronics. It reviews factors that influence heat transfer, including nozzle diameter, jet-to-surface spacing, and Reynolds number. The experimental setup examines heat transfer characteristics of air and water jets impinging on a heated surface. Results show that lower jet diameters and spacings and higher Reynolds numbers increase heat transfer. The conclusion is that jet impingement is effective for cooling applications due to the high heat transfer coefficients that can be achieved.
Abstract:This paper deals with the thermal and CFD analysis of automobile radiator. The theoretical calculation has been done in MAT Lab by varying the mass flow rate of coolant. Modeling has been done in Solidworks and exported to Ansys for CFD analysis. The temperature distribution, heat transfer rate for different velocities of coolant to has been done for different tube materials such as copper, aluminium and stainless steel. The numerical results were compared and found that copper has best heat transfer rate and has better efficiency than the others.
Transient Three-dimensional Numerical Analysis of Forced Convection Flow and ...IOSR Journals
A three-dimensional transient numerical study of a constant property Newtonian fluid in curved pipe under laminar flow conditions is presented for a uniform wall temperature boundary condition. Numerical solutions were obtained using the control volume method described by Patankar for the range of. The working fluid was water. The transient flow pattern and the temperature distribution on the tube section were derived for different values of the Reynolds number. Graphical results for velocity and temperature are presented and analyzed. Results have shown that the maximum velocity in center of velocity profile increase with increasing of Reynolds number. In curved pipes, time averaged results exhibited Dean circulation and a strong velocity and temperature stratification in the radial direction. Flow and heat transfer were strongly asymmetric, with higher values near the outer pipe bend.
Numerical Predictions of Enhanced Impingement Jet Cooling with Ribs and Pins ...AZOJETE UNIMAID
This document presents a numerical study of enhanced impingement jet cooling with ribs and pins on target surfaces. Computational fluid dynamics (CFD) simulations were conducted using commercial codes to predict heat transfer with different obstacle wall configurations. The obstacles investigated were ribs and rectangular pin-fins in both co-flow and cross-flow alignments. The CFD predictions showed good agreement with previous experimental results and revealed that obstacles increase turbulence but also reduce the highest thermal gradients and downstream cross-flow.
THE EFFECT OF GEOMETRICAL PARAMETERS ON HEAT TRANSFER AND HYDRO DYNAMICAL CHA...ijmech
Compact size and high heat transfer coefficient of helical coil heat exchangers causes them to have an
important role in various industrial applications. This paper investigate numerically on the influence of
different parameters such as coil radius, coil pitch and diameter of tube on the hydrodynamic and
heat transfer characteristics of helical double tube heat exchangers using the CFD software which is
based on the principles of heat transfer, fluid mechanics and thermodynamics. The results indicated that
heat transfer augmentation occurs by increasing of the inner Dean Number, inner tube diameter, curvature
ratio and by the reduction of the pitch of heat exchanger coil. By increasing the radius of coils, the
secondary flow effects due to centrifugal forces diminishes and flow of fluid through the coils tends to flow
in a straight path and as a result, the friction coefficient decreases consequently.
This document discusses air transient cooling characteristics in the entry regions of ducts with non-circular cross sections. It presents correlations and equations to calculate the hydrodynamic and thermal entrance lengths for triangular, rectangular, circular and square ducts. It also provides equations for the local Nusselt number and convective heat transfer coefficient in the combined entry region where the flow is both thermally and hydrodynamically developing. The analysis considers the transient heat transfer in the duct entry regions using temperature-dependent air properties and numerical modeling. The results indicate that the triangular duct enhances heat transfer the most compared to the other cross section ducts.
Effect of Arresters on Erosion in Economizer Zone and its AnalysisIDES Editor
Thermal Power Stations all over the world are facing
the problem of boiler tube leakage frequently. The consequences
of which affects the performance of power plant and huge
amount of money loss. It was also found from the trends of
failure that the economizer is the zone where the leakages are
found more. The maximum number of cause of failure in
economizer unit is due to flue gas erosion. The authors in this
paper have attempted to suggest a probable solution for
reduction of erosion in economiser zone and its analysis using
CFD tool. The past failure details revels that erosion is more in
U-bend areas of Economizer Unit because of increase in flue
gas velocity near these bends. Horizontal Arresters were
provided on the way of flue gas to reduce its velocity near these
bends. But it is observed that the velocity of flue gases
surprisingly increases near the lower bends as compared to
upper ones. In this paper the authors have submitted the
findings of analysis of finned tube economizer with Arresters
at different inclinations. A steady 3D CFD tool is used for
analysis and flow of the flue gases over the coils has been
observed. The effect of provision of arresters on the surface
temperature, the flue gas temperature, pressure and velocity
field of fluid flow within an economizer tube using the actual
boundary conditions have been analyzed using CFD tool. The
analysis considered the inclination of Arresters both in upward
and downward directions. The optimum dimensions of arrester
and feasible inclination is recommended as a result of the study.
The installation of Arresters, may affect the performance of
economizer. The authors have analyzed the performance and
tried to comment on this issue too.
This document analyzes critical heat flux (CHF) in vertical rectangular narrow channels. It summarizes several previous studies that experimentally analyzed CHF in narrow channels using different fluids, channel dimensions, and heating conditions. The document then describes the author's own experiment on CHF using a vertical stainless steel plate with a 1 mm gap. Results showed the highest CHF occurred at the middle of the plate and CHF decreased towards the upper and lower parts. CHF values were compared to several existing correlations, with some correlations showing better agreement with results from different plate positions. The study contributes to understanding CHF in narrow channels.
Heat transfer enhancement in fire tube boiler using hellically ribbed tubes.IRJET Journal
This document summarizes a computational fluid dynamics study comparing heat transfer in plain tubes and helically ribbed tubes for a fire tube boiler. The CFD analysis found that the helically ribbed tube has a higher heat transfer rate and surface temperature than the plain tube. Specifically:
1) For the same tube length, the helically ribbed tube had a total heat transfer rate 4% higher than the plain tube and a surface temperature of 247°C compared to 209°C.
2) For the same total heat transfer rate, the length of the helically ribbed tube could be reduced to 700mm while the plain tube required 1750mm, allowing for a more compact boiler design.
3)
1. As gas injection rate increases, the gravitational pressure drop decreases while the frictional pressure drop increases in an oil well.
2. Oil production rate increases when the decrease in gravitational pressure drop is greater than the increase in frictional pressure drop.
3. Oil production rate declines when the increase in frictional pressure drop is greater than the decrease in gravitational pressure drop.
Cfd Simulation and Experimentalverification of Air Flow through Heated PipeIOSR Journals
The aim of this work is to validate the Dittus-Boelter equation by experimental,correlation and Simulation method. It used to find the value of heat transfer coefficient ‘h’ for turbulent flow in many fluid transfer systems. This work discusses how the Dittus-Boelter equation is applied to the problem of circular pipe. In CFD simulation ICEM CFD for modeling and CFX13 for analysis are used. Results of CFD simulation will be obtained by CFD-POST. Here heat transfer coefficient value is compared by correlations,experiment and CFD simulations, finally the aim of this work is to validate Dittus-Boelter equation.
IRJET- Study of Jet Impingement Heat TransferIRJET Journal
This document reviews research on jet impingement heat transfer. It discusses the flow and heat transfer characteristics of single and multiple impinging jets. Key factors that influence heat transfer are jet Reynolds number, nozzle-to-plate spacing, jet pattern, and crossflow. The document summarizes various empirical correlations that have been developed to predict average heat transfer coefficients. It also reviews numerical studies on modeling heat transfer for multi-jet systems and discusses the effects of parameters like Reynolds number, nozzle spacing, crossflow, and jet interference.
Mathematical model of refrigerants boiling process in theAlexander Decker
The document presents a mathematical model of the boiling process of refrigerants in a partially closed volume. Key points:
1) The model considers heat transfer and fluid flow in a tube with outer fins that form a partially closed volume around the tube.
2) Bubbles form within this volume and grow until exiting through openings, with the liquid maintaining contact between the tube and fins.
3) Equations were developed to model the heat transfer between the boiling refrigerant and tube, mass transfer between the phases, and fluid dynamics within the partially closed volume.
4) Comparisons showed close agreement between the mathematical model and experimental data, demonstrating its ability to predict performance improvements over standard finned tubes.
International Journal of Computational Engineering Research(IJCER)ijceronline
International Journal of Computational Engineering Research(IJCER) is an intentional online Journal in English monthly publishing journal. This Journal publish original research work that contributes significantly to further the scientific knowledge in engineering and Technology
Flow And Heat Transfer Characteristics On A Confined Slot Jet Impinging On A ...Dahiru Lawal
This document describes a study on the flow and heat transfer characteristics of a confined slot jet impinging on a constant heat flux surface. The study examines the effects of varying the jet width-to-height ratio (H/W) and Reynolds number (Re) on heat transfer properties. Numerical simulations are conducted to analyze the velocity contours, temperature distributions, Nusselt numbers, and pressure coefficients. Results show that heat transfer rate increases with higher H/W ratios and Re numbers. Flow and thermal fields also become time-dependent and asymmetric if Re exceeds a critical value. Validation of the numerical model is also performed.
Second Law Analysis of Fluid Flow and Heat Transfer through Porous Channel wi...inventionjournals
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 presents a numerical investigation of mixed convective flow inside straight and bend pipes. The study examines the effects of inlet Rayleigh number and Reynolds number on velocity and temperature profiles within the pipes. For a straight horizontal pipe, secondary flow develops at higher L/D ratios due to density variations, producing maximum velocity at the bottom. For bend pipes, secondary flow in the horizontal section combines with buoyancy effects in the vertical section. Higher Rayleigh numbers indicate a transition from forced to mixed to free convection. Results show secondary flow weakens and profiles become more uniform at farther downstream positions.
This document presents a numerical investigation of mixed convective flow inside straight and bend pipes. The study examines the effects of inlet Rayleigh number and Reynolds number on velocity and temperature profiles within the pipes. For a straight horizontal pipe, secondary flow develops at higher L/D ratios, producing maximum velocity at the bottom of the pipe. As L/D increases beyond 10, secondary flow effects diminish. Higher Rayleigh numbers indicate stronger buoyancy effects on flow and temperature distribution. In a bend pipe, secondary flow and buoyancy-driven effects combine to influence mixed convection patterns.
Exploring the Use of Computation Fluid Dynamics to Model a T-Junction for UM ...Doug Kripke
1) This document discusses using computational fluid dynamics (CFD) to model a T-junction where hot and cold fluid flows combine. Specifically, it will compare the realizable and standard k-ε turbulence models in replicating experimental velocity field measurements of water in a T-junction.
2) Extensive previous water experiments on a T-junction characterized the thermal striping phenomenon and measured velocity and temperature distributions. This project will use those experimental conditions and measurements for validation of CFD simulations.
3) Reynolds number calculations confirmed the flows are fully turbulent, validating the use of turbulence models. The CFD model setup and boundary conditions aimed to replicate the previous experimental conditions for validation purposes.
This document discusses wellbore performance and flow modeling. It covers:
1) Single phase liquid, gas, and two phase flow models based on mechanical energy balance equations. Pressure drops are calculated considering elevation change, kinetic energy, and friction.
2) Methods for calculating friction factors including Fanning, Darcy, and Moody charts. Correlations for gas properties like viscosity and deviation factor are also presented.
3) Examples of calculating pressure drops in single phase liquid and gas flows. Numerical methods for solving gas flow equations are described.
4) Multiphase flow is more complex due to different flow regimes affecting pressure gradients. Models include homogeneous and separated flow approaches.
SPLIT SECOND ANALYSIS COVERING HIGH PRESSURE GAS FLOW DYNAMICS AT PIPE OUTLET...AEIJjournal2
A detailed investigation covering piped gas flow characteristics in high pressure flow conditions. Such flow analysis can be resolved using established mathematical equations known as the Fanno condition, which usually cover steady state, or final flow conditions. However, in real life, such flow conditions are
transient, varying with time. This paper uses CFD analysis providing a split second “snapshot” at what happens at the pipe outlet, and therefore, a closer understanding at what happens at the pipe’s outlet in high pressure gas flow condition
Numerical_Analysis_of_Turbulent_Momentum_and_Heat_Transfer_in_a_Rectangular_H...Nate Werner
- The document analyzes turbulent momentum and heat transfer in a rectangular helical duct using water and freon-12 as working fluids.
- It develops a 3D model of the helical duct geometry based on prior research. Simulations are run using ANSYS Fluent and CFX to analyze flow, temperature, and turbulence fields.
- The results show secondary flows developing with higher velocities near the outer wall. While some aspects agree with prior work, the simulations produce higher velocities and different vortex structures than expected. Thermal development also takes longer than velocity development.
New Microsoft Office PowerPoint PresentationSudhir Shinde
This document summarizes a seminar presentation on heat transfer via jet impingement. The presentation discusses how jet impingement is used to effectively remove large amounts of heat from surfaces, such as in cooling turbine blades and electronics. It reviews factors that influence heat transfer, including nozzle diameter, jet-to-surface spacing, and Reynolds number. The experimental setup examines heat transfer characteristics of air and water jets impinging on a heated surface. Results show that lower jet diameters and spacings and higher Reynolds numbers increase heat transfer. The conclusion is that jet impingement is effective for cooling applications due to the high heat transfer coefficients that can be achieved.
Abstract:This paper deals with the thermal and CFD analysis of automobile radiator. The theoretical calculation has been done in MAT Lab by varying the mass flow rate of coolant. Modeling has been done in Solidworks and exported to Ansys for CFD analysis. The temperature distribution, heat transfer rate for different velocities of coolant to has been done for different tube materials such as copper, aluminium and stainless steel. The numerical results were compared and found that copper has best heat transfer rate and has better efficiency than the others.
Transient Three-dimensional Numerical Analysis of Forced Convection Flow and ...IOSR Journals
A three-dimensional transient numerical study of a constant property Newtonian fluid in curved pipe under laminar flow conditions is presented for a uniform wall temperature boundary condition. Numerical solutions were obtained using the control volume method described by Patankar for the range of. The working fluid was water. The transient flow pattern and the temperature distribution on the tube section were derived for different values of the Reynolds number. Graphical results for velocity and temperature are presented and analyzed. Results have shown that the maximum velocity in center of velocity profile increase with increasing of Reynolds number. In curved pipes, time averaged results exhibited Dean circulation and a strong velocity and temperature stratification in the radial direction. Flow and heat transfer were strongly asymmetric, with higher values near the outer pipe bend.
Numerical Predictions of Enhanced Impingement Jet Cooling with Ribs and Pins ...AZOJETE UNIMAID
This document presents a numerical study of enhanced impingement jet cooling with ribs and pins on target surfaces. Computational fluid dynamics (CFD) simulations were conducted using commercial codes to predict heat transfer with different obstacle wall configurations. The obstacles investigated were ribs and rectangular pin-fins in both co-flow and cross-flow alignments. The CFD predictions showed good agreement with previous experimental results and revealed that obstacles increase turbulence but also reduce the highest thermal gradients and downstream cross-flow.
THE EFFECT OF GEOMETRICAL PARAMETERS ON HEAT TRANSFER AND HYDRO DYNAMICAL CHA...ijmech
Compact size and high heat transfer coefficient of helical coil heat exchangers causes them to have an
important role in various industrial applications. This paper investigate numerically on the influence of
different parameters such as coil radius, coil pitch and diameter of tube on the hydrodynamic and
heat transfer characteristics of helical double tube heat exchangers using the CFD software which is
based on the principles of heat transfer, fluid mechanics and thermodynamics. The results indicated that
heat transfer augmentation occurs by increasing of the inner Dean Number, inner tube diameter, curvature
ratio and by the reduction of the pitch of heat exchanger coil. By increasing the radius of coils, the
secondary flow effects due to centrifugal forces diminishes and flow of fluid through the coils tends to flow
in a straight path and as a result, the friction coefficient decreases consequently.
This document discusses air transient cooling characteristics in the entry regions of ducts with non-circular cross sections. It presents correlations and equations to calculate the hydrodynamic and thermal entrance lengths for triangular, rectangular, circular and square ducts. It also provides equations for the local Nusselt number and convective heat transfer coefficient in the combined entry region where the flow is both thermally and hydrodynamically developing. The analysis considers the transient heat transfer in the duct entry regions using temperature-dependent air properties and numerical modeling. The results indicate that the triangular duct enhances heat transfer the most compared to the other cross section ducts.
Effect of Arresters on Erosion in Economizer Zone and its AnalysisIDES Editor
Thermal Power Stations all over the world are facing
the problem of boiler tube leakage frequently. The consequences
of which affects the performance of power plant and huge
amount of money loss. It was also found from the trends of
failure that the economizer is the zone where the leakages are
found more. The maximum number of cause of failure in
economizer unit is due to flue gas erosion. The authors in this
paper have attempted to suggest a probable solution for
reduction of erosion in economiser zone and its analysis using
CFD tool. The past failure details revels that erosion is more in
U-bend areas of Economizer Unit because of increase in flue
gas velocity near these bends. Horizontal Arresters were
provided on the way of flue gas to reduce its velocity near these
bends. But it is observed that the velocity of flue gases
surprisingly increases near the lower bends as compared to
upper ones. In this paper the authors have submitted the
findings of analysis of finned tube economizer with Arresters
at different inclinations. A steady 3D CFD tool is used for
analysis and flow of the flue gases over the coils has been
observed. The effect of provision of arresters on the surface
temperature, the flue gas temperature, pressure and velocity
field of fluid flow within an economizer tube using the actual
boundary conditions have been analyzed using CFD tool. The
analysis considered the inclination of Arresters both in upward
and downward directions. The optimum dimensions of arrester
and feasible inclination is recommended as a result of the study.
The installation of Arresters, may affect the performance of
economizer. The authors have analyzed the performance and
tried to comment on this issue too.
This document analyzes critical heat flux (CHF) in vertical rectangular narrow channels. It summarizes several previous studies that experimentally analyzed CHF in narrow channels using different fluids, channel dimensions, and heating conditions. The document then describes the author's own experiment on CHF using a vertical stainless steel plate with a 1 mm gap. Results showed the highest CHF occurred at the middle of the plate and CHF decreased towards the upper and lower parts. CHF values were compared to several existing correlations, with some correlations showing better agreement with results from different plate positions. The study contributes to understanding CHF in narrow channels.
Heat transfer enhancement in fire tube boiler using hellically ribbed tubes.IRJET Journal
This document summarizes a computational fluid dynamics study comparing heat transfer in plain tubes and helically ribbed tubes for a fire tube boiler. The CFD analysis found that the helically ribbed tube has a higher heat transfer rate and surface temperature than the plain tube. Specifically:
1) For the same tube length, the helically ribbed tube had a total heat transfer rate 4% higher than the plain tube and a surface temperature of 247°C compared to 209°C.
2) For the same total heat transfer rate, the length of the helically ribbed tube could be reduced to 700mm while the plain tube required 1750mm, allowing for a more compact boiler design.
3)
1. As gas injection rate increases, the gravitational pressure drop decreases while the frictional pressure drop increases in an oil well.
2. Oil production rate increases when the decrease in gravitational pressure drop is greater than the increase in frictional pressure drop.
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A numerical simulation of the effect of ambient temperature on capillary tube performance in domestic split air conditioners with r22 alternatives
1. Journal of Information Engineering and Applications www.iiste.org
ISSN 2224-5782 (print) ISSN 2225-0506 (online)
Vol.4, No.3, 2014
21
A Numerical Simulation of the Effect of Ambient Temperature on
Capillary Tube Performance in Domestic Split Air Conditioners
with R22 Alternatives
Khalid A. Joudi*
,Qusay R. Al-Amir
Dept.Mech. Eng.,Babylon Univ., Iraq
E-mail address: khalid47joudi@yahoo.com
Abstract
A numerical model has been formulated to simulate the capillary tube insplit air conditioners of 1 and 2 TR
capacities under high outdoor air temperatures. The outdoor air temperature was varied from 35 to 55°C with
5 °Cincrements. Three environment friendly refrigerantswereused as alternatives to R22. They are R290, R407C
and R410A. Finite difference method has been adopted in conjunction with EES software. This model is capable
of predicting pressure, temperature, quality, velocityandviscositydistributions through the capillary tube for all
refrigerants. The geometrical parameters and input conditions to the capillary tube model areextracted from
experimental data. Theseinclude inner diameter, mass flow rate, surface roughness, temperature and pressure of
the subcooledliquid refrigerant. Theresults show that the capillary choking length increases with increasing
outdoor air temperature. Results of the simulation show thatR290 needsmore capillary length than the other
refrigerants investigated,whereas R410A needs less capillary tube length.
Keywords: Capillary tube simulation; capillary tube with R22,R290, R407C, R410A; high ambient effect on
capillary tube.
Highlights:
- Capillary tube characteristics at high ambient for R22 and Alternatives
-R290, R407C, R410A performance in capillary tubes at high ambient
- Capillary tubes simulation with R290, R407C, R410A in split A/C at high ambient.
1.Introduction
A capillary tube is a constant area expansion device, which is commonly used in low capacity systems such as
domestic refrigerators, freezers, and room air conditioners because of its simplicity and low cost. The capillary
tube creates the pressure drop between the high and low pressure sides.
In the past decades, most studies essentially focused on the flow through straight capillary
tubes([1],[2],[3],[4]).Jung et al.[1] performed experimental and theoretical studies of pressure drop through a
capillary tube to predict the size of capillary tubes used in residential air conditioners and also to provide simple
correlations for practicing engineers. The study covered condensing temperatures of 40 0
C, 45 0
C, 50 0
C, and
subcooling (0 0
C, 2.5 0
C, 5 0
C), capillary tube diameter (1.2 - 2.4mm), mass flow rate (5-50g/s). The results
indicated that the capillary tube length varies uniformly with the changes in condensing temperature and
subcooling.
Kim et al.[2] discussed the characteristics of flow and pressure drop in adiabatic capillary tubes of inner
diameters of 1.2 to 2.0 mm, and tube lengths of 500 to 2000 mm for several condensing temperatures and
various degrees of subcoolingwith R22.
A numerical simulation of straight capillary tube was carried out by Imran [3]for R22 and alternative
R407C.Zhou and Zhang[4] investigated the performance of coiled adiabatic capillary tubes both theoretically
and experimentally. They developed a new method including metastable liquid and two phase regions.
The main objective of this study is to study theeffect of ambient temperature on coiled capillary tubesindomestic
split air conditioners with ozone friendly refrigerants under high outdoor air temperatures.
2.ADIABATICCAPILLARY TUBE MODELING
The refrigerant flow inside the capillary tube can be divided into single phase and two-phase regions. Fig.(1) is
aschematic diagram of the coiled capillary tube where point 1 denotes the condenser exit and point 2 is the
capillary tube inlet. There is a small pressure drop between these points due to entrance loss. The refrigerant
enters the capillary tube at point 2 as a subcooled liquid. The pressure decreases linearly until the refrigerant
becomes saturated liquid at point 3. Beyond point 3, the refrigerant enters the two phase region where the
pressure decreases non-linearly with length until it reaches the end of the capillary tube at point 4. Finally, point
5 represents the evaporator inlet.
The present model uses the following assumptions:
1.The capillary tube operates at steady state.
2. Journal of Information Engineering and Applications www.iiste.org
ISSN 2224-5782 (print) ISSN 2225-0506 (online)
Vol.4, No.3, 2014
22
2.Asubcooled liquid enters the capillary tube .
3.The flow of refrigerant inside the capillary tube is one dimensional, homogenous and adiabatic.
4.Changes in kinetic and potential energies are negligible.
5.Isenthalpic expansion through the capillary tube.
Fig.1 Schematic diagram of a capillary tube
Applying the Bernoulli equation between points 1 and 2, the minor pressure drop at the entrance was
calculated by Sinpiboon and Wongwises [5] as;
.
2
)1(
2
21
V
kPP
ρ
+=− (1)
Wherekis the entrance loss factor. References are not in agreement about its value. The value of k=0.5 is used
here as given by Chen [6].
In the single phase region between points 2 and 3, the pressure at point 2 decreases linearly until saturation
pressure at point 3 according to the following equation (Munson and Young [7]);
.
2
2
32
V
d
L
fPP
ca
s
s
ρ
=− (2)
The single phase length Ls is calculated from substituting equation 2 in equation 1( Sukkarin and Somchai[8])
thus;
( )
+−−= )1(
2
. 312
kPP
Gf
d
L
s
ca
s
ρ
(3)
whereG is the mass velocity and fsis the friction factor, which can be determined from the Moody
correlation(Moody [9]).
2
2
Re
74.5
7.3
/
ln
325.1
+
=
ca
s
de
f (4)
By applying the steady flow energy equation for the single phase liquid region in the capillary tube with
negligible work and heat exchange, we get:
H2=H3=Hs (5)
Applying the steady flow energy equation for each element lying in the two phase region, between points 3
and 4:
( )2
22
3
3 .
22
fgffgf vxv
G
HxH
V
H +++=+ (6)
Equation 6 is quadratic in x and the quality x can be expressed as ;
( )
22
2
3
3
22
22222
.
22
.
..2....
fg
f
f
fgfgffgffg
vG
H
V
H
vG
vGvvGvvGH
x
+−−−−−
=
m
(7)
Once the quality for element i is known, properties such as viscosity,density and entropy can be easily calculated
by using the saturated properties for the liquid and vapor phases as:
ifiigii xx µµµ )1( −+= (8)
3. Journal of Information Engineering and Applications www.iiste.org
ISSN 2224-5782 (print) ISSN 2225-0506 (online)
Vol.4, No.3, 2014
23
1
)1(
−
−
+=
if
i
ig
i
i
xx
ρρ
ρ (9)
ifiigii sxsxs )1( −+= (10)
The Reynolds number in the two phase region is determined as:
i
caii
i
dV
µ
ρ ..
Re = (11)
Where Vi is the velocity for element i in the two phase region. The two phase friction factor if is calculated by
the correlation given by Sami and Tribes [10];
( )
−
−
=
4.2
)1(
exp
1Re
1.3
25.0
i
ii
i
x
x
f (12)
The incremental length of each section in the two-phase region is calculated as follows(Sukkarin and
Somchai,[11]):
∆
+
∆−
=∆
i
i
i
ca
i
G
P
f
d
L
ρ
ρρ
2
.
2
(13)
The calculation in two phase flow region is terminated when the flow approaches the choked.The total length of
the two-phase region is;
∑=
∆=
n
i
it LL
2
(14)
Finally, the total length of the capillary tube is the sum of the single phase and two-phase lengths, i.e.
tstot LLL += (15)
The coiling effect of the capillary tube can be entered in the calculation of the friction factors. A straight tube
model can also be applied to coiled capillary tubes by changing the corresponding friction factor equations
(Sukkarin and Somchai,[11]). The equation proposed by Mori and Nakayama [12] is used here with different
coefficients for the tube coiled wall roughness as;
( )
( )[ ] ( )[ ]
+=
1615.2
2
1615.2
5.0
1
Re
1
Re ccacca
cca
c
Dd
C
Dd
DdC
f (16)
Where:
( ) ( )
( )
( ) ( )
( )36
242
2
37
241
1
10*54555343.2
10*0613314.1388038.2510*79778633.6
10*31570014.1
10*63030629.42472168.8510*88411177.1
ca
caca
ca
caca
de
dedeC
de
dedeC
+
−+=
+
−+=
−
−
This method is used for both liquid and two phase regions.
3. SOLUTION PROCEDURE
The Engineering Equation Solver (EES) software(Klein [13]) is used in this work for computer programming.
Refrigerant thermo-dynamicand transport properties such as density, dynamic viscosity, specific enthalpy,
thermalconductivity are taken from EES software. In the single-phase region, after calculating the Reynolds
number, the single phase friction factorand singlephase length were calculated.Initial condition of two phase
region is the end condition of thesingle phase flow region.Calculation of the two-phase region length Ltrequired
a numerical solution due to the change in quality along this region (see Eq.7).For each elementin the two-phase
region, the pressure Pi, the temperature Ti, the vapor quality xi, the entropySiand the two-phase friction factor (ft)
were calculated. At each element, the calculatedentropy Siwas compared with the entropy of the previous
element Si-1, to make sure thatthe entropy increased as the refrigerant flows through the capillary tube. The
entropyincreases continuously through the capillary tube to a certain maximum and then it begins to decrease
(choking condition). The two phase region length is calculated by eq.(14).The total capillary tube length is the
……(17)
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Vol.4, No.3, 2014
24
sum of thetwo region lengths.
Fig. 3 shows the flow chart of simulation model for the capillary tube .
FIG. 2.SIMULATION MODEL FLOW CHART FOR THE CAPILLARY TUBE
4. RESULTS AND DISCUSION
Fig.3Comparesthe pressure distribution along the capillary tube inthe present study and that of Sukkarin et
al.[8]The comparison is good. Only R22 and R410A results are shown as typical results.The present model can
be used to predict the flow characteristics forthe other alternatives.
Fig.4shows the pressure distribution along the capillary tube at ASHAREstandard test conditions for 1 TR and 2
TR systems. For an actual cycle, each refrigeranthas a different condensing temperature and pressure. Therefore,
the capillary tube length is different for each one. The capillary tube length depends on the operating conditions
at the inlet of the capillary tube and thermo-physical properties, especially viscosity, of the refrigerant. It is
observed that there is a linear drop in pressure for R22 and its alternatives between the entrance of the capillary
tube and saturation (flash) point in the single phase region. The pressure dropsrapidly near the end of the tube in
the two phase region.Results showed that R290 required more length for chokingdue to its lower liquid viscosity
and refrigerant mass flow rate than the other refrigerants tested. R410A needed less. The magnitude of pressure
drops is different for each refrigerant depending on its mass flow rate (or its specific volume). Thus, R290 shows
the lowest pressure drops owing to its large specific volume. Whereas, the similar specific volumes of R22 and
Is
Pi≥Pe
yes
yes
Start
Input physical parameters: dc,Dco, k
Calculate hf, ρf, µf, ∆Ploss at inlet of capillary tube
Calculate: f, V ,G and Re
Calculate :Lsp
Divide two phase region into no. of element(i), ∆Li
Initialize: Ltp = 0
Solve Eq. (7) for x at element i and calculate fi, hi, µi, si,ρi, Gi and Vi
Calculate Capillary Tube Increment Length, ∆Li
Ltp,i=Ltp+∆Li
Check if
Si ≤Smax
Pi =Pi,choked
Calculate: L=Lsp+Ltp
Calculate: Po, xo, To, ho
Input Operating Conditions m, Pin, Tin ,Tout
END
Pi =Pi,choked
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Vol.4, No.3, 2014
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R407C make their pressure drops similar. R410A has the largest pressure drop. This is true for both systems.
The change in vapor quality with length of the capillary tube is shown in Fig.5. For all refrigerants, the quality is
zero up to the flash point. After that, the change of vapor quality increases sharply towards the end of the tubein
the two phase region. The reason for this behavior is thatthe acceleration and friction effects in the two-phase
region increase the pressure gradient giving rise to a higher vaporization rate.Fig. 6shows the temperature
distribution along the capillary tube at standard conditions for the1 TR and 2 T R systems. The temperature drop,
of all refrigerants is insignificant in the single phase region. However, in the two-phase region, the temperature
dropssharply with pressure.
The Reynolds number along the capillary tube at standard conditions for R22 and its alternatives for both 1 TR
and 2 TRsystems is shown inFig.7. In the single phase region, the variations of Reynolds number is minimal
because the thermo-physical properties of the liquid refrigerant do not change significantly. In the two phase flow,
the values of Reynolds number start to drop because the thermo-physical properties, especially the viscosity,
increases as the capillary tube length increases. The velocity distributions along the capillary tube at standard
conditions for the two systems is shown in Fig.8. In the single phase region, the velocity remains constant
because the refrigerant remains liquid. In the two phase region, the flow velocity of refrigerant increases because
of the specific volume of the mixtureincreases due to vaporization.
Figs.9and10show the effect of outdoor air temperature on pressure distribution along the capillary tube for R22
and R410A as typical results.As the outdoor air temperature increases, the condenser pressure and mass flow also
increase. This increases the both the single phase and two phase lengths. Therefore, the total length of the
capillary tube for R22 refrigerant increased from 1.78 m to 2.69 m as theoutdoor air temperature increased from
35O
C to 55O
C. For R410A, it increased from 1.29m to2.43 m.
Fig 11 showsthe vapor quality along the capillary tube as a function of outdoor air temperatures for R290 as a
typical results. When the outdoor air temperature increases, the quality values at exit increase due to the increase
of the specific volume of the mixture. Fig.12showsa typical temperature distribution along the capillary tube as a
function of outdoor air temperatures for R407C.As the outdoor air temperature increases, the condensing
temperature at the entrance to the capillary tube increases. The capillary tube length increases accordingly with
the condensing temperature. Extensive details for all four refrigerants are given by Al-Amir [17].
5. CONCLUSIONS
1.R290 required the longest capillary tube length due to its lower liquid viscosity and mass flow rate than the
other refrigerant. R410A needed the shortest length .
2.The magnitude of pressure drops is different for each refrigerant. R290 showed the smallest pressure drop.
Similar specific volumes of R22 and R407C made their pressure drops similar. R410A showed the largest
pressure drop across the capillary tube.
3.Increasing theoutdoor air temperature,increasesthe condenser pressure for all refrigerants. This increasedboth
the single phase and two phase lengths.
REFERENCES
[1] Jung D., Park C., Park P., 1999, " Capillary tube selection for HCFC22 alternative", International Journal of
Refrigeration 22, 604-614.
[2] Kim S. G., Kim M. S., Ro S.T., 2001, " Flow and Pressure Drop Characteristics of R22 In Adiabatic
Capillary Tubes" KSME International Journal; Vol. 15 No.9, pp. 1328-1338.
[3] Imran A. A. , 2009, " Adiabatic and Separated Flow of R-22 and R-407C in Capillary Tube", Eng& Tech.
Journal , Vol .27, No 6.
[4] Zhou G., Zhang Y., 2006, " Numerical and experimental investigations on the performance of coiled
adiabatic capillary tubes", Applied Thermal Engineering 26, 1106–1114.
[5] Sinpiboon J. ,Wongwises S., 2002," Numerical investigation of refrigerant flow through non-adiabatic
capillary tubes" Applied Thermal Engineering , 22, 2015–2032.
[6] Chen W., 2008," A comparative study on the performance and environmental characteristics of R-410A and
R-22 residential air conditioners", Applied Thermal Engineering , Vol. 28, 1-7.
[7] Munson B. R., Young D. F., 2010, " Fundamentals of Fluid Mechanics" Fourth edition, John Wiley & Sons.
Inc. USA.
[8] Sukkarin C., Somchai W., 2010, " Effects of coil diameter and pitch on the flow characteristics of alternative
refrigerants flowing through adiabatic helical capillary tubes" International Communications in Heat and Mass
Transfer 37, 1305–1311.
[9] Moody, L.F., Friction Factors for Pipe Flow, ASME, Vol. 66, pp. 671-684, 1944.
[10]Sami S. M. and Tribes C., 1998, “Numerical Prediction of Capillary Tube Behavior with Pure and Binary
Alternative refrigerants”, Journal of Applied Thermal Engineering, Vol. 18, No 6, P.491-502.
[11]Sukkarin C., Somchai W., 2011," A comparison of flow characteristics of refrigerants flowing through
6. Journal of Information Engineering and Applications www.iiste.org
ISSN 2224-5782 (print) ISSN 2225-0506 (online)
Vol.4, No.3, 2014
26
adiabatic straight and helical capillary tubes" International Communications in Heat and Mass Transfer 38, 398–
404.
[12] Mori Y., Nakayama W., 1967, "Study on forced convective heat transfer in curve pipes II", International
Journal of Heat and Mass Transfer, Vol.10, No.1, 37–59. Quoted by Sukkarin et al.,2011.
[13] Klein S.A., 2006, Engineering Equation Solver commercial version V8.914 .
[14] G. Bo, L. Yuanguang, W. Zhiyi, J. Buyun, Analysis on the adiabatic flow of R407C in capillary tube, Appl.
Therm. Eng. 23 (2003) 1871–1880
[15] J.L. Hermes , M. Cludio, T. K. Fernando, Algebraic solution of capillary tube flows. Part II: Capillary tube
suction line heat exchangers, Appl. Therm. Eng. 30 (2010) 770–775
[16] P.K. Bansal , G. Wang, Numerical analysis of choked refrigerant flow in adiabatic capillary tubes, Appl.
Therm. Eng. 24 (2004) 851–863
[17] Al-Amir Q. R., 2013," Experimental assessment and numerical simulation of the performance of small scale
air-conditioning systems using alternative refrigerants to R-22", PhD thesis, College of Engineering, University
of Baghdad.
NOMENCLATURE
D
d
e
Coiling Diameter(m)
Capillary tube inner diameter (m)
Roughness (m)
-
f Friction factor
G Mass flux(kg/s.m2
)
H
K
k
Enthalpy(kJ/kg)
Thermal conductivity(W/m.K)
Entrance loss factor
L
P
Length (m)
Pressure(N/m2
)
Re Reynolds number
S
V
v
x
Entropy (kJ/kg.k)
Velocity(m/s)
Specific volume(m3
/kg)
Vapor quality
Greek Symbols
∆
µ
ρ
Change
Dynamic viscosity (kg/m,
s)
Density (kg/m3
)
Subscripts
c condenser
cacapillary
e evaporator
ssingle phase
ttwo phase
fliquid
g vapor
ielement
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27
0 0.5 1 1.5 2 2.5 3 3.5 4
0
400
800
1200
1600
Capillary Tube Length(m)
Pressure(kpa)
Present studyPresent study
Sukkarin et al[ ]Sukkarin et al[ ]
R22
R410A
Tcond=20[C]
Pcond=15 bar[C]
di=1.4 mm
Dc=40 mm
ε/δι=0.0003
mass flow rate=30.5kg/h
Fig.3Pressure distribution along the capillary tube.
0 0.5 1 1.5 2 2.5 3
0
500
1000
1500
2000
2500
3000
Capillary Tube Length(m)
Pressure(kpa)
R22R22
R290R290
R407CR407C
R410AR410A
SYSTEM(2TR)
a) 2TR system
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
0
500
1000
1500
2000
2500
3000
Capillary Tube Length(m)
Pressure(kpa)
SYSTEM (1TR)
R22R22
R290R290
R410AR410A
R407CR407C
b)1TR system
Fig.4Pressure distribution along the capillary tube at standard test conditions for 1 TR and 2 T Rsystems .
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Vol.4, No.3, 2014
28
0 0.5 1 1.5 2 2.5 3
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
Capillary Tube Length(m)
Qualitty(-)
SYSTEM 2TR
R290R290
R407CR407C
R410AR410A
R22R22
a)2TR system
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
Capillary Tube Length(m)
Quality(-)
SYSTEM (1TR)
R22R22
R290R290
R410AR410A
R407CR407C
b)1 TR system
Fig.5Quality distributions along the capillary tube at standard conditions for 1 TR and 2 T Rsystems.
0 0.5 1 1.5 2 2.5 3
0
10
20
30
40
50
60
Capillary Tube Length(m)
Temperature(C)
SYSTEM(2TR)
R22R22
R290R290
R407CR407C
R410AR410A
a) 2TR system
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29
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
0
10
20
30
40
50
Capillary Tube Length(m)
Temperature(C) SYSTEM (1TR)
R22R22
R290R290
R410AR410A
R407CR407C
b)1TR system
Fig.6Temperature distributions along the capillary tube at standard conditions for 1 TR and 2 T R systems .
0 0.5 1 1.5 2 2.5 3
0
20000
40000
60000
80000
100000
120000
140000
160000
180000
Capillary Tube Length(m)
ReynoldNumber(-)
R22R22
SYSTEM(2TR)
R290R290
R407CR407C
R410AR410A
a)2TR system
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
60000
80000
100000
120000
140000
160000
180000
200000
220000
Capillary Tube Length(m)
ReynoldNumber(-)
SYSTEM (1TR)
R22R22
R290R290
R410AR410A
R407CR407C
b)1TR system
Fig.7Reynolds numbers along the capillary tube at standard conditions for 1 TR and 2 T Rsystems.
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30
0 0.5 1 1.5 2 2.5 3
0
20
40
60
80
100
120
140
Capillary Tube Length(m)
Velocity(m/s)
R22R22
SYSTEM(2TR)
R290R290
R407CR407C
R410AR410A
a)2TR system
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
0
20
40
60
80
100
120
140
160
Capillary Tube Length(m)
Velocity(m/s)
SYSTEM (1TR)
R22R22
R290R290
R410AR410A
R407CR407C
b)1TR system
Fig.8Velocity distributions along the capillary tube at standard conditions for 1 TR and 2 T Rsystems .
0 0.5 1 1.5 2 2.5 3
0
500
1000
1500
2000
2500
3000
Capillary Tube Length(m)
Pressure(kpa)
R22 (2TR)
Tamb=35CTamb=35C
Tamb=40CTamb=40C
Tamb=45CTamb=45C
Tamb=50CTamb=50C
Tamb=55CTamb=55C
Fig.9Pressure distribution along the capillary tube at different outdoor air temperature for R22
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0 0.5 1 1.5 2 2.5 3
500
1000
1500
2000
2500
3000
3500
Capillary Tube Length[m]
Pressure(kpa)
R410A(2TR)
Tamb=35CTamb=35C
Tamb=40CTamb=40C
Tamb=45CTamb=45C
Tamb=50CTamb=50C
Tamb=55CTamb=55C
Fig.10Pressure distribution along the capillary tube at differentoutdoor air temp.for R410A
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5
0
0.05
0.1
0.15
0.2
0.25
0.3
Capillary Tube Length[m]
Quality(-)
R290(2TR)
Tamb=35CTamb=35C
Tamb=40CTamb=40C
Tamb=45CTamb=45C
Tamb=50CTamb=50C
Tamb=55CTamb=55C
Fig.11Quality distribution along the capillary tube at different outdoor air temperature for R290
0 0.5 1 1.5 2 2.5 3 3.5 4
0
5
10
15
20
25
30
35
40
45
50
55
Capillary Tube Length(m)
Temperature(C)
R407C(2TR)
Tamb=35CTamb=35C
Tamb=40CTamb=40C
Tamb=45CTamb=45C
Tamb=50CTamb=50C
Tamb=55CTamb=55C
Fig.12Temperature distribution along the capillary tube at different outdoor air temperature for R407C