This document summarizes a thermal analysis of the Badovli Dam in Iran. Some key points:
- The Badovli Dam will be located in northwest Iran and will provide water for drinking, agriculture, and hydropower. It will have a total volume of 350,000 cubic meters of roller compacted concrete (RCC).
- Since the RCC will be placed quickly, a thermal analysis is needed to calculate heat generation and stresses to determine a suitable construction schedule. The analysis models heat transfer through the dam considering boundary conditions and temperature effects on hydration rate.
- Two types of cracking are considered: surface cracking due to temperature gradients and mass cracking due to restraint during cooling. The analysis finds
1. Thermal analysis was conducted on the Kahir RCC dam in Iran to analyze temperature distributions and cracking risks over 6000 days.
2. Finite element modeling in ANSYS simulated heat generation during hydration and temperature changes over time for the dam's two-part construction schedule.
3. Results found maximum temperature changes up to 21.7°C without resulting cracking risks, due to the dam's low restraint from its foundation properties. Movement joints were still advised for differential settlement prevention.
Investigation of Different Types of Cement Material on Thermal Properties of ...IJERA Editor
One of the challenges in sustainable development is to optimize the energy efficiency of buildings during their
lifespan. Nowadays the applying of different types of cements in modern concretes provide low embodied CO2
with the intrinsic property called “thermal mass” that reduces the risk of overheating in the summer and
provides passive heating in the winter. Thermal mass is affected by thermal properties of concrete which it is the
ability of the element to exchange heat with the environment and is based on thermal capacity, conductivity, and
density. Laboratory experiments measured density, specific capacity and thermal conductivity of sustainable
concrete mixes with various percentages of GGBS, PFA, SF. The results contribute to the investigation of the
performance of thermal properties performance in sustainable concrete.
Air Conditioning System with Ground Source Heat ExchangerIOSR Journals
This document summarizes the design, development, and testing of an air conditioning system with a ground source heat exchanger (ACSWGSHE). The ACSWGSHE was tested with the borehole filled with still air, water, and sand. Testing found that the ACSWGSHE achieved the highest coefficient of performance (COP) of 3.72 when the borehole was filled with water, compared to a COP of 2.11 for a conventional split air conditioner. Power consumption was also 29% lower for the ACSWGSHE with water filling compared to the conventional system. However, when the borehole was filled with sand, the COP decreased to 1.07 due to improper heat exchange between the condenser
8
12
16
20
24
Time(Hrs)
January 2009
Fig.21 Indoor temperature variation in RCC and
PCM rooms January 2009
0
4
8
12
16
20
24
Time(Hrs)
February 2009
Fig.22 Indoor temperature variation in RCC and
PCM rooms February 2009
1) The document discusses the development of novel roof structures for thermal comfort and energy savings in buildings, with a focus on structures with and without phase change materials (PCMs).
2) It outlines the theoretical simulation and modeling analysis conducted
This document discusses a study on the effect of micro-grooved fins on the thermal and hydraulic performance of fin-and-tube heat exchangers. It fabricated fins with parallel micro-grooves using photolithography and chemical etching. It then tested four full-scale heat exchangers with these fins, measuring dry and wet air-side pressure drop and heat transfer coefficients. The micro-grooved fins reduced wet air-side pressure drop by 9.3-53% while having a negligible impact on dry and wet heat transfer coefficients. This novel fin design improved performance by better managing condensate, demonstrating potential benefits for HVAC&R systems. It also evaluated the durability of an alkyl silane coating applied
This document summarizes the development of a high-power lithium target for accelerator-based boron neutron capture therapy (BNCT). Key points:
- A water-cooled conical target is being developed to accept a 50 kW proton beam and produce neutrons via the 7Li(p,n)7Be reaction for BNCT applications.
- Computational fluid dynamics modeling was used to design the target with 20 helical water channels to keep the lithium surface below 150°C with a water flow of 80 kg/min.
- An initial prototype target was fabricated and underwent preliminary hydraulic testing matching CFD predictions. Further electron beam thermal testing is planned at Sandia National Laboratories to validate the
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.
Cfd and conjugate heat transfer analysis of heat sinks with different fin geo...eSAT Journals
This document discusses a computational fluid dynamics (CFD) and conjugate heat transfer analysis of different fin geometries for heat sinks used in electronics cooling. Five fin geometries - zigzag, fluted, slanted mirror, custom pin fin, and staggered array - were analyzed under different heat loads and air velocity. The results show that the slanted mirror geometry provided the best thermal performance with the lowest thermal resistance and highest heat transfer coefficient, while maintaining a relatively low pressure drop. CFD simulations using ANSYS Fluent were conducted to analyze fluid flow, heat transfer, temperature distribution, and thermal performance of the different heat sink designs.
1. Thermal analysis was conducted on the Kahir RCC dam in Iran to analyze temperature distributions and cracking risks over 6000 days.
2. Finite element modeling in ANSYS simulated heat generation during hydration and temperature changes over time for the dam's two-part construction schedule.
3. Results found maximum temperature changes up to 21.7°C without resulting cracking risks, due to the dam's low restraint from its foundation properties. Movement joints were still advised for differential settlement prevention.
Investigation of Different Types of Cement Material on Thermal Properties of ...IJERA Editor
One of the challenges in sustainable development is to optimize the energy efficiency of buildings during their
lifespan. Nowadays the applying of different types of cements in modern concretes provide low embodied CO2
with the intrinsic property called “thermal mass” that reduces the risk of overheating in the summer and
provides passive heating in the winter. Thermal mass is affected by thermal properties of concrete which it is the
ability of the element to exchange heat with the environment and is based on thermal capacity, conductivity, and
density. Laboratory experiments measured density, specific capacity and thermal conductivity of sustainable
concrete mixes with various percentages of GGBS, PFA, SF. The results contribute to the investigation of the
performance of thermal properties performance in sustainable concrete.
Air Conditioning System with Ground Source Heat ExchangerIOSR Journals
This document summarizes the design, development, and testing of an air conditioning system with a ground source heat exchanger (ACSWGSHE). The ACSWGSHE was tested with the borehole filled with still air, water, and sand. Testing found that the ACSWGSHE achieved the highest coefficient of performance (COP) of 3.72 when the borehole was filled with water, compared to a COP of 2.11 for a conventional split air conditioner. Power consumption was also 29% lower for the ACSWGSHE with water filling compared to the conventional system. However, when the borehole was filled with sand, the COP decreased to 1.07 due to improper heat exchange between the condenser
8
12
16
20
24
Time(Hrs)
January 2009
Fig.21 Indoor temperature variation in RCC and
PCM rooms January 2009
0
4
8
12
16
20
24
Time(Hrs)
February 2009
Fig.22 Indoor temperature variation in RCC and
PCM rooms February 2009
1) The document discusses the development of novel roof structures for thermal comfort and energy savings in buildings, with a focus on structures with and without phase change materials (PCMs).
2) It outlines the theoretical simulation and modeling analysis conducted
This document discusses a study on the effect of micro-grooved fins on the thermal and hydraulic performance of fin-and-tube heat exchangers. It fabricated fins with parallel micro-grooves using photolithography and chemical etching. It then tested four full-scale heat exchangers with these fins, measuring dry and wet air-side pressure drop and heat transfer coefficients. The micro-grooved fins reduced wet air-side pressure drop by 9.3-53% while having a negligible impact on dry and wet heat transfer coefficients. This novel fin design improved performance by better managing condensate, demonstrating potential benefits for HVAC&R systems. It also evaluated the durability of an alkyl silane coating applied
This document summarizes the development of a high-power lithium target for accelerator-based boron neutron capture therapy (BNCT). Key points:
- A water-cooled conical target is being developed to accept a 50 kW proton beam and produce neutrons via the 7Li(p,n)7Be reaction for BNCT applications.
- Computational fluid dynamics modeling was used to design the target with 20 helical water channels to keep the lithium surface below 150°C with a water flow of 80 kg/min.
- An initial prototype target was fabricated and underwent preliminary hydraulic testing matching CFD predictions. Further electron beam thermal testing is planned at Sandia National Laboratories to validate the
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.
Cfd and conjugate heat transfer analysis of heat sinks with different fin geo...eSAT Journals
This document discusses a computational fluid dynamics (CFD) and conjugate heat transfer analysis of different fin geometries for heat sinks used in electronics cooling. Five fin geometries - zigzag, fluted, slanted mirror, custom pin fin, and staggered array - were analyzed under different heat loads and air velocity. The results show that the slanted mirror geometry provided the best thermal performance with the lowest thermal resistance and highest heat transfer coefficient, while maintaining a relatively low pressure drop. CFD simulations using ANSYS Fluent were conducted to analyze fluid flow, heat transfer, temperature distribution, and thermal performance of the different heat sink designs.
Analysis of A Double Spiral Counter Flow Calorimeter in Impinging Flame Jet U...IJERA Editor
This document analyzes a double spiral counter flow calorimeter (DSCFC) using computational fluid dynamics (CFD). The DSCFC consists of two concentric spiral channels for fluid flow over a heated base plate, allowing for heat transfer between the solid and fluid. CFD simulations are performed using ANSYS-CFX to analyze heat transfer characteristics at varying Reynolds numbers and base temperatures. The results show heat transfer decreases with increasing Reynolds number but increases with higher base temperature. Pressure and temperature profiles within the DSCFC are also presented. In conclusion, the CFD analysis finds uniform pressure drop along the spiral channels except at the mid-length, with pressure and outlet temperature decreasing at higher Reynolds numbers.
PREDICTIONS AT THE BLOW END OF THE LD-KGC CONVERTER BY A SEMI-DYNAMIC CONTROL...ijmech
The decision to perform direct turn-down or not, based on an accurate estimate of temperature at the blow end, prevents two types of problems: (a) the loss of productivity due to the wait time in the steelmaking; and (b) tapping of off-specification heat.
In the present work, a technique and model for temperature prediction at the blow end are briefly discussed, along with their limitations and perspectives for application. As a result of this analysis, a mathematical model based in heat and mass balances has been developed with a view to evaluating the possibility of improving this prediction capability. The formulation of said model and its preliminary adjustment to industrial data are presented and discussed, and the main limitations and difficulties in the application of the methodology are highlighted.
The study here presented focuses the development of a semi-dynamic control model in the LD-KGC converter (Linz-Donawitz-Kawasaki Gas Control Converter). The control model enables one to predict the temperature of the blow end by solving both the energy and mass equations. The computational language adopted is Fortran 90; the equations are solved iteratively until a solution for temperature is found. The inputs to the control model are the load data of the LD-KGC converter at the blow beginning and the collected data by the lance to 89% of oxygen blow. The results obtained in the present work were compared to the data measured in steel making. The semi-dynamic control model results agree well with data for LDKGC converters. However, the model is sensitive to the premises here adopted, like those pertaining to the exit gas composition (CO and CO2).
This document describes an experimental apparatus designed to visualize mixed convection flows in vertical, horizontal, and inclined pipes. The key aspects of the design allow for flow visualization over the entire heated portion of the test section for the first time. This is achieved through use of a thin, electrically conductive gold film heater attached to the outside of a plexiglass pipe, and enclosing this pipe within a larger evacuated plexiglass tube for insulation. The experimental apparatus is used to investigate flow patterns through dye injection visualization in the different pipe orientations. Flow patterns observed include steady recirculating flows and laminar instabilities in vertical pipes, and steady spiraling flows in inclined and horizontal pipes.
1) The document presents a CFD study analyzing heat transfer enhancement in multi-lead rifled (MLR) boiler tubes compared to plain wall tubes.
2) The study varied geometric parameters of MLR tubes like number of riflings, rifling height, and pitch length to optimize heat transfer.
3) Simulation results at the operating conditions of an actual boiler show increased heat transfer and temperature with MLR tubes versus plain tubes. Implementation of optimized MLR tubes in the boiler is recommended to improve furnace heat transfer.
Comparative CFD Analysis of Shell and Serpentine Tube Heat ExchangerIRJET Journal
1. The document presents a comparative CFD analysis of a shell and tube heat exchanger with a serpentine tube using two different materials: ASTM A179 carbon steel and C12200 copper alloy.
2. The analysis found that the heat exchanger was up to 14% more effective when using the C12200 copper alloy tube compared to the carbon steel tube, due to the higher thermal conductivity of copper.
3. While copper provided better heat transfer, material selection for heat exchangers must also consider other factors like corrosion resistance, mechanical properties, and cost.
This document describes a mathematical heat transfer model to predict the heating of steel slabs in a reheating furnace. The model considers heat transfer between the slab and its surroundings, including radiative heat transfer between slabs, skids, furnace gases and walls, as well as convective heat transfer from the gases. The model also predicts the formation and growth of scale on the slab surface over time in order to investigate its effect on slab heating. Preliminary results from the model show reasonable agreement with experimental data and indicate that the presence of scale has a considerable effect on slab heating characteristics.
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.
Heat exchangers are used widely in industrial application such as chemical,
food processing, power production, refrigeration and air-conditioning
industries. Helical coiled heat exchangers are used in order to obtain a large
heat transfer per unit volume and to enhance the heat transfer rate on the inside
surface. In the present study, CFD simulations are carried out for a counter
flow tube in tube helical heat exchanger where hot water flows through the
inner tube and cold water flows through the outer tube. From the simulation
results heat transfer coefficient, pressure drop and nusselt number are
calculated. The heat transfer characteristics of the same are compared with that
of a counter flow tube in tube straight tube heat exchanger of same length
under same temperature and flow conditions. CFD simulation results showed
that the helical tube in tube heat exchanger is more effective than the straight
tube in tube heat exchanger.
Heat loss through wall/slab/foundation joint for high-rise buildings Kathrine Brejnrod
This document provides details on calculating heat loss through the joint between an outer wall and ground slab of a high-rise building. It describes modeling the joint in the simulation program HEAT2 to determine the linear heat transmission coefficient and lowest indoor surface temperature to evaluate heat loss and condensation risk. Both steady-state and transient calculations are performed and compared. The original construction and alternative improvements are analyzed. The report concludes that transient simulation provides a more accurate assessment than steady-state. It suggests an alternative build-up to reduce heat loss and moisture issues at the wall/slab joint.
Influence of Operating Variables on Functional Parameters of Ammonia Synthesi...Premier Publishers
The document discusses the influence of operating temperature and pressure on the functional parameters of an ammonia synthesis reactor. It presents equations to calculate the reactor volume, space velocity, and mean residence time as functions of temperature, pressure, and nitrogen conversion. The analysis found that at a constant conversion, increasing the operating temperature and pressure decreases the reactor volume and mean residence time, while increasing the space velocity and heat generated per reactor volume. For example, from 698-773K at 250 atm pressure and 0.32 conversion, the volume and mean residence decreased while space velocity and heat generated per volume increased.
Numerical Analysis of Heat Transfer Enhancement in Pipe-inPipe Helical Coiled...iosrjce
This document presents a numerical analysis of heat transfer enhancement in pipe-in-pipe helical coiled heat exchangers. Computational fluid dynamics (CFD) was used to analyze the effect of varying parameters like inner tube diameter, mass flow rates, and flow configuration (parallel vs. counter flow). The results show that overall heat transfer coefficients increase with increasing inner Dean number and mass flow rates. Heat transfer rates also increase with higher inner mass flow rates. Counter flow configuration provides better heat transfer than parallel flow. Increasing the inner tube size decreases the total heat transfer rate due to a reduction in annulus cross-sectional area. Measured inner Nusselt numbers agree reasonably well with existing correlations.
Various parameters affecting the performance of a regeneratorIJESFT
Main objective of this review paper is to show how various parameters affect the performance of regenerator. Performance of regenerator is very important parameter to design it. Various parameters which affect the performance of regenerator have been discussed.
This document discusses a study that tested the performance of heat exchangers constructed from fins with anisotropic micro-grooved surfaces. Two prototype heat exchangers were constructed with fins that had microchannels etched into them to create anisotropic wettability. Testing was conducted to measure contact angles, critical sliding angles, water retention during dip testing, and changes in air-side pressure drop between dry and wet conditions. The results showed that the micro-grooved fin surfaces, in combination with an alkyl silane coating, could reduce water retention by over 27% and decrease the wet air-side pressure drop by 30-36% compared to a baseline heat exchanger. The document provides context on related research and describes the experimental methods
Coefficient of Performance Enhancement of Refrigeration CyclesIJERA Editor
This document summarizes an experimental study that investigated enhancing the coefficient of performance (COP) of refrigeration cycles by using different condenser designs. Three condenser designs were tested in a refrigerator: the original design and two new designs (one with plain copper tubes and one with copper tubes welded to a stainless steel plate). Measurements of temperature, pressure, heat rejection, and COP were taken over time under varying evaporator loads. The results showed that the COP of the new designs increased by up to 20% compared to the original design when no load was applied. COP generally increased with higher evaporator loads. The plain copper tube design performed best, providing better heat transfer than the welded plate design.
This study experimentally analyzed the heat transfer characteristics of R744/R1270 refrigerant mixtures flowing in a horizontal smooth tube. Tests were conducted at varying mass fluxes (40-80 kg/m2s) and heat fluxes (15-24 kW/m2). The heat transfer coefficient, inner wall temperature, and Nusselt number were found to decrease along the length of the tube. Higher mass and heat fluxes resulted in higher heat transfer coefficients and inner wall temperatures. The mixture of R744/R1270 at a 25/75 ratio and mass flux of 80 kg/m2s provided maximum heat transfer.
Investigation on pulse velocity changes in RCC with different cement content ...Hamidreza Araghian
Ultrasonic pulse velocity was measured on 20 types of roller compacted concrete mixtures with different cement contents and admixtures. Pulse velocity increased with higher cement content and was most improved by superplasticizers, followed by plasticizers, with retarders having the lowest impact. Higher pulse velocities correlated with increased compressive strength, tensile strength, elastic modulus, and density/permeability. Dynamic elastic modulus was calculated from pulse velocity tests and compared to results from standard static modulus tests.
The document discusses the benefits of exercise for mental health. Regular physical activity can help reduce anxiety and depression and improve mood and cognitive function. Exercise causes chemical changes in the brain that may help protect against mental illness and improve symptoms.
Meals on Wheels of Central Maryland (MOWCM) provides nutritious meals and services to help seniors live independently at home. In the past year, MOWCM expanded programs and services through increased partnerships. Volunteers contributed over 70,000 hours of service, allowing MOWCM to serve more clients. Events like culinary dinners and triathlons raised funds and awareness in the community. MOWCM aims to meet the growing needs of seniors through quality services and community support.
- Certain minerals, like quartz, exhibit piezoelectricity, which is the ability to generate an electric charge when subjected to mechanical stress.
- Piezoelectricity occurs because these minerals have asymmetrical crystal structures that become imbalanced when compressed, producing separated positive and negative charges.
- Common applications of piezoelectricity include its use in lighters, where quartz crystals produce sparks to ignite gas, and in devices like watches, microphones, and record players.
Analysis of A Double Spiral Counter Flow Calorimeter in Impinging Flame Jet U...IJERA Editor
This document analyzes a double spiral counter flow calorimeter (DSCFC) using computational fluid dynamics (CFD). The DSCFC consists of two concentric spiral channels for fluid flow over a heated base plate, allowing for heat transfer between the solid and fluid. CFD simulations are performed using ANSYS-CFX to analyze heat transfer characteristics at varying Reynolds numbers and base temperatures. The results show heat transfer decreases with increasing Reynolds number but increases with higher base temperature. Pressure and temperature profiles within the DSCFC are also presented. In conclusion, the CFD analysis finds uniform pressure drop along the spiral channels except at the mid-length, with pressure and outlet temperature decreasing at higher Reynolds numbers.
PREDICTIONS AT THE BLOW END OF THE LD-KGC CONVERTER BY A SEMI-DYNAMIC CONTROL...ijmech
The decision to perform direct turn-down or not, based on an accurate estimate of temperature at the blow end, prevents two types of problems: (a) the loss of productivity due to the wait time in the steelmaking; and (b) tapping of off-specification heat.
In the present work, a technique and model for temperature prediction at the blow end are briefly discussed, along with their limitations and perspectives for application. As a result of this analysis, a mathematical model based in heat and mass balances has been developed with a view to evaluating the possibility of improving this prediction capability. The formulation of said model and its preliminary adjustment to industrial data are presented and discussed, and the main limitations and difficulties in the application of the methodology are highlighted.
The study here presented focuses the development of a semi-dynamic control model in the LD-KGC converter (Linz-Donawitz-Kawasaki Gas Control Converter). The control model enables one to predict the temperature of the blow end by solving both the energy and mass equations. The computational language adopted is Fortran 90; the equations are solved iteratively until a solution for temperature is found. The inputs to the control model are the load data of the LD-KGC converter at the blow beginning and the collected data by the lance to 89% of oxygen blow. The results obtained in the present work were compared to the data measured in steel making. The semi-dynamic control model results agree well with data for LDKGC converters. However, the model is sensitive to the premises here adopted, like those pertaining to the exit gas composition (CO and CO2).
This document describes an experimental apparatus designed to visualize mixed convection flows in vertical, horizontal, and inclined pipes. The key aspects of the design allow for flow visualization over the entire heated portion of the test section for the first time. This is achieved through use of a thin, electrically conductive gold film heater attached to the outside of a plexiglass pipe, and enclosing this pipe within a larger evacuated plexiglass tube for insulation. The experimental apparatus is used to investigate flow patterns through dye injection visualization in the different pipe orientations. Flow patterns observed include steady recirculating flows and laminar instabilities in vertical pipes, and steady spiraling flows in inclined and horizontal pipes.
1) The document presents a CFD study analyzing heat transfer enhancement in multi-lead rifled (MLR) boiler tubes compared to plain wall tubes.
2) The study varied geometric parameters of MLR tubes like number of riflings, rifling height, and pitch length to optimize heat transfer.
3) Simulation results at the operating conditions of an actual boiler show increased heat transfer and temperature with MLR tubes versus plain tubes. Implementation of optimized MLR tubes in the boiler is recommended to improve furnace heat transfer.
Comparative CFD Analysis of Shell and Serpentine Tube Heat ExchangerIRJET Journal
1. The document presents a comparative CFD analysis of a shell and tube heat exchanger with a serpentine tube using two different materials: ASTM A179 carbon steel and C12200 copper alloy.
2. The analysis found that the heat exchanger was up to 14% more effective when using the C12200 copper alloy tube compared to the carbon steel tube, due to the higher thermal conductivity of copper.
3. While copper provided better heat transfer, material selection for heat exchangers must also consider other factors like corrosion resistance, mechanical properties, and cost.
This document describes a mathematical heat transfer model to predict the heating of steel slabs in a reheating furnace. The model considers heat transfer between the slab and its surroundings, including radiative heat transfer between slabs, skids, furnace gases and walls, as well as convective heat transfer from the gases. The model also predicts the formation and growth of scale on the slab surface over time in order to investigate its effect on slab heating. Preliminary results from the model show reasonable agreement with experimental data and indicate that the presence of scale has a considerable effect on slab heating characteristics.
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.
Heat exchangers are used widely in industrial application such as chemical,
food processing, power production, refrigeration and air-conditioning
industries. Helical coiled heat exchangers are used in order to obtain a large
heat transfer per unit volume and to enhance the heat transfer rate on the inside
surface. In the present study, CFD simulations are carried out for a counter
flow tube in tube helical heat exchanger where hot water flows through the
inner tube and cold water flows through the outer tube. From the simulation
results heat transfer coefficient, pressure drop and nusselt number are
calculated. The heat transfer characteristics of the same are compared with that
of a counter flow tube in tube straight tube heat exchanger of same length
under same temperature and flow conditions. CFD simulation results showed
that the helical tube in tube heat exchanger is more effective than the straight
tube in tube heat exchanger.
Heat loss through wall/slab/foundation joint for high-rise buildings Kathrine Brejnrod
This document provides details on calculating heat loss through the joint between an outer wall and ground slab of a high-rise building. It describes modeling the joint in the simulation program HEAT2 to determine the linear heat transmission coefficient and lowest indoor surface temperature to evaluate heat loss and condensation risk. Both steady-state and transient calculations are performed and compared. The original construction and alternative improvements are analyzed. The report concludes that transient simulation provides a more accurate assessment than steady-state. It suggests an alternative build-up to reduce heat loss and moisture issues at the wall/slab joint.
Influence of Operating Variables on Functional Parameters of Ammonia Synthesi...Premier Publishers
The document discusses the influence of operating temperature and pressure on the functional parameters of an ammonia synthesis reactor. It presents equations to calculate the reactor volume, space velocity, and mean residence time as functions of temperature, pressure, and nitrogen conversion. The analysis found that at a constant conversion, increasing the operating temperature and pressure decreases the reactor volume and mean residence time, while increasing the space velocity and heat generated per reactor volume. For example, from 698-773K at 250 atm pressure and 0.32 conversion, the volume and mean residence decreased while space velocity and heat generated per volume increased.
Numerical Analysis of Heat Transfer Enhancement in Pipe-inPipe Helical Coiled...iosrjce
This document presents a numerical analysis of heat transfer enhancement in pipe-in-pipe helical coiled heat exchangers. Computational fluid dynamics (CFD) was used to analyze the effect of varying parameters like inner tube diameter, mass flow rates, and flow configuration (parallel vs. counter flow). The results show that overall heat transfer coefficients increase with increasing inner Dean number and mass flow rates. Heat transfer rates also increase with higher inner mass flow rates. Counter flow configuration provides better heat transfer than parallel flow. Increasing the inner tube size decreases the total heat transfer rate due to a reduction in annulus cross-sectional area. Measured inner Nusselt numbers agree reasonably well with existing correlations.
Various parameters affecting the performance of a regeneratorIJESFT
Main objective of this review paper is to show how various parameters affect the performance of regenerator. Performance of regenerator is very important parameter to design it. Various parameters which affect the performance of regenerator have been discussed.
This document discusses a study that tested the performance of heat exchangers constructed from fins with anisotropic micro-grooved surfaces. Two prototype heat exchangers were constructed with fins that had microchannels etched into them to create anisotropic wettability. Testing was conducted to measure contact angles, critical sliding angles, water retention during dip testing, and changes in air-side pressure drop between dry and wet conditions. The results showed that the micro-grooved fin surfaces, in combination with an alkyl silane coating, could reduce water retention by over 27% and decrease the wet air-side pressure drop by 30-36% compared to a baseline heat exchanger. The document provides context on related research and describes the experimental methods
Coefficient of Performance Enhancement of Refrigeration CyclesIJERA Editor
This document summarizes an experimental study that investigated enhancing the coefficient of performance (COP) of refrigeration cycles by using different condenser designs. Three condenser designs were tested in a refrigerator: the original design and two new designs (one with plain copper tubes and one with copper tubes welded to a stainless steel plate). Measurements of temperature, pressure, heat rejection, and COP were taken over time under varying evaporator loads. The results showed that the COP of the new designs increased by up to 20% compared to the original design when no load was applied. COP generally increased with higher evaporator loads. The plain copper tube design performed best, providing better heat transfer than the welded plate design.
This study experimentally analyzed the heat transfer characteristics of R744/R1270 refrigerant mixtures flowing in a horizontal smooth tube. Tests were conducted at varying mass fluxes (40-80 kg/m2s) and heat fluxes (15-24 kW/m2). The heat transfer coefficient, inner wall temperature, and Nusselt number were found to decrease along the length of the tube. Higher mass and heat fluxes resulted in higher heat transfer coefficients and inner wall temperatures. The mixture of R744/R1270 at a 25/75 ratio and mass flux of 80 kg/m2s provided maximum heat transfer.
Investigation on pulse velocity changes in RCC with different cement content ...Hamidreza Araghian
Ultrasonic pulse velocity was measured on 20 types of roller compacted concrete mixtures with different cement contents and admixtures. Pulse velocity increased with higher cement content and was most improved by superplasticizers, followed by plasticizers, with retarders having the lowest impact. Higher pulse velocities correlated with increased compressive strength, tensile strength, elastic modulus, and density/permeability. Dynamic elastic modulus was calculated from pulse velocity tests and compared to results from standard static modulus tests.
The document discusses the benefits of exercise for mental health. Regular physical activity can help reduce anxiety and depression and improve mood and cognitive function. Exercise causes chemical changes in the brain that may help protect against mental illness and improve symptoms.
Meals on Wheels of Central Maryland (MOWCM) provides nutritious meals and services to help seniors live independently at home. In the past year, MOWCM expanded programs and services through increased partnerships. Volunteers contributed over 70,000 hours of service, allowing MOWCM to serve more clients. Events like culinary dinners and triathlons raised funds and awareness in the community. MOWCM aims to meet the growing needs of seniors through quality services and community support.
- Certain minerals, like quartz, exhibit piezoelectricity, which is the ability to generate an electric charge when subjected to mechanical stress.
- Piezoelectricity occurs because these minerals have asymmetrical crystal structures that become imbalanced when compressed, producing separated positive and negative charges.
- Common applications of piezoelectricity include its use in lighters, where quartz crystals produce sparks to ignite gas, and in devices like watches, microphones, and record players.
Current knowledge of the transversity quark distribution function, or how transversely polarized quarks are distributed in a transversely polarized proton?
Service Solahart Cabang Jakarta Selatan Kami Dari CV. Davinatama Service Menyediakan Jasa Perbaikan Pemanas Air SOLAHART SERVICE & PENJUALAN Pemanas air solar water heater tenaga matahari khususnya SOLAHART
This document provides a subject index for information related to adult congenital heart disease. It lists topics, conditions, procedures, and other terms alphabetically and provides the corresponding page numbers for where they are discussed in the referenced material. Some of the main topics covered include arrhythmias, aortopathies, atrial septal defect, Ebstein's anomaly, Fontan procedure, pulmonary hypertension, tetralogy of Fallot, and transposition of the great arteries. The page numbers are often followed by "f" or "t" to indicate they refer to figures or tables, respectively, on those pages.
Object oriented programming involves modeling real-world entities as objects that encapsulate both data and behavior. Programmers define classes that specify the attributes and methods of these objects. This is a different approach than traditional procedural programming, as it focuses on objects rather than functions.
The document promotes the Gettep activity tracker mobile app which has over 70 million users across Android, iOS, and Windows Phone platforms. It has helped users track over 10 million pounds of weight loss and encourages people to love their brand. It provides contact information for Katica Babarczi and Akos Boros to learn more about Gettep and its website www.gettep.com.
Contrive Experiences prepared By Liselle Bautistapompoms29
This document discusses contrived experiences, which are edited copies of reality that are used as substitutes for real things in the classroom when it is not practical or possible to bring the real thing. Contrived experiences include models, mock ups, specimens, objects, simulations, and games. They are used to overcome limitations of space and time, edit reality to focus on parts or processes, overcome difficulties of size, understand inaccessible concepts, and help learners understand abstractions. Common contrived experiences are models, which are small reproductions of real things made of synthetic materials, and mock ups, which create representations of reality.
This short document contains a greeting repeated multiple times. It consists of the phrase "Hi there" written four separate times with no other words or context provided.
Alicia Douglas has over 30 years of experience in aviation operations and engineering at both air carriers and the FAA. She currently manages the Planning & Financial Resources branch at the FAA, overseeing budgeting, planning, and IT projects. Previously she held various roles developing regulations and policies, overseeing web and IT programs, and ensuring regulatory compliance for air carriers. She has a diverse background including airline certification, flight operations, maintenance, and engineering.
Streams are used in C++ for input/output (I/O) operations. The stream is the central concept of the iostream classes, which handle input from and output to external entities. There are different stream classes for different I/O needs, such as ostream for output streams, ifstream for input streams, and fstream for simultaneous input and output streams. Iterators and algorithms in the Standard Template Library (STL) allow containers like vectors to be used with I/O streams to read from and write to files.
Avijit Kumar Singh is seeking a position as an Accounts Officer. He has over 3 years of experience working as an Accounts Officer and Finance Executive. He is proficient in Tally ERP 9.0, MS Office, and maintaining accurate financial reports. He is responsible for accounts receivable, credit management, bank reconciliation, and assisting with budget preparation.
Experimental Investigation of Pool Boiling Enhancement on Different Structure...IRJET Journal
1) The document experimentally investigates pool boiling enhancement on different structured surfaces, including plain, V-shaped, and square structures.
2) The experiment was conducted in a boiling chamber by varying the electric supply and applying/not applying vibration. Surface temperature and heat flux were calculated.
3) The results showed that the square surface provided more appreciable heat flux and heat transfer coefficient compared to the other surfaces. Modifying the surface structure can enhance pool boiling heat transfer.
JIMEC Thermal modeling and Simulation of HX Conference PaperAhmed Sohail Izhar
1) The document describes a thermal modeling and simulation of an industrial shell and tube heat exchanger used to cool raw natural gas.
2) A thermal model was developed using the effectiveness-NTU method to determine the required heat transfer area and estimate the tube-side and shell-side heat transfer coefficients.
3) The results of the model showed that a heat transfer area of about 1132 m2 is required to provide a thermal duty of 1.4 MW, with tube-side and shell-side heat transfer coefficients of 950 W/m2K and 495 W/m2K respectively.
Palladium Tower Dayanım Gelişimi Kalıp Alma ve Beton Sıcaklığı Bildiri Mayıs ...Ali Elmaskaya
This document summarizes the methods used to control temperature and ensure proper strength development during the casting and curing of the large, deep foundation of the Palladium Tower building in Istanbul. Key points include:
- The 3m deep foundation was cast in 3 layers of 1m each to control heat generation and cracking.
- Temperature monitoring ensured internal and surface temperatures differed by less than 20°C and average temperatures remained below 55°C.
- Concrete mixtures and curing were designed to achieve the required compressive strengths before removing formwork to prevent cracking. Strength-time curves were developed from on-site cylinder tests.
Corrosion resistance performance of fly ash blended cement concreteseSAT Journals
Abstract Durability of reinforced concrete with respect to corrosion of reinforcement is one of the major aspects to be considered in the management of civil infrastructure systems. An accelerated laboratory test method developed at SERC where the concrete specimen containing rebar is subjected to polarization under a constant voltage in a sodium chloride solution. It is found that the current response with time follows that of a typical service life model indicating depassivation and corrosion propagation. Index terms- Materials, cement, super plasticizer, workability, compressive strength etc.
Corrosion resistance performance of fly ash blended cement concreteseSAT Publishing House
1) The document describes an experimental study on the corrosion resistance of reinforced concrete with different percentages of fly ash replacement.
2) An accelerated corrosion test method was used where concrete cylinders containing rebar were subjected to polarization in a sodium chloride solution. This simulated rebar corrosion in marine environments.
3) The test results showed that concretes with 30% fly ash replacement had the highest corrosion resistance, with initiation times of 54 and 63 days for M25 and M30 grade concrete, respectively.
4) Graphs of current over time showed changes in slope indicating the initiation time and time for cracking, which increased with higher percentages of fly ash replacement up to 30%.
Remaining life assessment of refinery furnace tubes using finite element methodBarhm Mohamad
Crude oil heater 9Cre-1Mo steel tubes from a refinery plant were studied, after 5 years of service at nominally 650 Cº and 3 bar, to predict their remnant lives. The investigation included dimensional, hardness and tensile measurements in addition to accelerated stress rupture tests between 650 Cº and 700 Cº and microstructural examination. Tube specimens were taken from two sections, the overheated side and the side which only saw the nominal operating temperature. The method employed involved the prediction of the increase in temperature with increasing sediment deposition during the operating life times using an FEM model. In addition the predicted temperatures are used to derive appropriate creep properties at relevant temperatures in a 3D pipe FEM creep analysis to predict the pipe deformation rate. All compare well with the actual service exposed pipe measurements and layer deposition. The overheated side revealed a small loss of creep strength in a stress rupture test. A layer of sediment (appr. 10 mm thickness) consisting basically of sintered carbon (coke) spread over the inside of the tube was acting as a thermal barrier causing the temperature to rise above 650 Cº. Analysis for the overheated side predicted an upper bound temperature of 800 Cº and a life of about 50 h suggesting that failure by creep rupture could occur rapidly in the sediment region.
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.
ANALYSIS OF HEAT TRANSFER CHARACTERISTICS IN CROSS FLOW PLATE FIN TYPE HEAT E...IRJET Journal
This document summarizes an analysis of heat transfer characteristics in a cross-flow plate fin heat exchanger using non-Newtonian fluids. The study used a cross-flow plate fin heat exchanger constructed of aluminum with corrugated fins to transfer heat between hot water and cold fluids of varying concentrations of carboxy methyl cellulose (CMC). Experiments were conducted at different flow rates and CMC concentrations to determine parameters such as heat transfer coefficients, effectiveness, and heat transfer performance. Results showed that increasing CMC concentration and flow rate affected these parameters.
The document summarizes research on designing and analyzing grooved heat pipes. Heat pipes use both heat conductivity and phase change to efficiently transfer heat between two different surfaces. The researchers focused on improving heat transfer by introducing grooves on the inner surface of heat pipes to increase surface area. They analyzed conventional and grooved heat pipe models made of different materials using ANSYS software. The results showed that grooved heat pipes and different materials increased heat transmission compared to conventional designs. Velocity, pressure, and temperature distributions within the pipes were also examined.
The document describes an air conditioning system with a ground source heat exchanger (ACSWGSHE) that was designed and tested. A conventional 1.5 ton split air conditioner was modified by replacing the condenser with a ground heat exchanger placed 15 meters underground. The heat exchanger was made of copper tubing in a helical coil shape. Testing showed the system performed best when the borehole was filled with water, achieving a coefficient of performance of 3.72, higher than the 2.11 COP of the conventional split system.
IRJET- Fundamentals of Maturity Methods for Estimating Concrete Strength: ReviewIRJET Journal
This document reviews different maturity methods used to predict the compressive strength of concrete based on its temperature history. It discusses two main maturity models - the Nurse-Saul function and the Arrhenius function. The Nurse-Saul function calculates maturity as the sum of time multiplied by temperature above a datum temperature (usually -10°C). The Arrhenius function is based on the concept of activation energy from chemistry and calculates maturity as an integral of time and temperature. The document also reviews past literature on maturity methods and discusses how maturity can be used to estimate in-place concrete strength for purposes like formwork removal or post-tensioning schedules.
FIRE RESISTANT ANALYSIS OF RC BEAM COLUMN JOINTIRJET Journal
This document summarizes a study that uses finite element analysis to analyze the fire resistant behavior of reinforced concrete beam-column joints. The study models beam-column joints exposed to fire based on the ISO 834 standard fire curve and analyzes the effects of different exposure conditions (2 sides, 3 sides, or 4 sides exposed). It finds that failure occurs more quickly when more sides of the joint are exposed to fire. The study concludes that the number of exposed sides significantly impacts a structure's ability to withstand fire, and that thermal failure criteria are more important than deflection criteria during a fire.
This document discusses waste heat recovery using thermoelectric generators. It begins by introducing the Seebeck effect which allows heat to be directly converted to electricity via a temperature gradient across conductors. The key factors for good thermoelectric materials - high Seebeck coefficient, electrical conductivity and low thermal conductivity - are discussed. Lead telluride is identified as a suitable high performance material for recovering waste heat between 200-600°C. A thermoelectric couple model is analyzed using ANSYS software, showing a voltage of 0.074806V, current of 19.083A and power of 1.4275W can be generated. The summary concludes the analysis demonstrates the potential of thermoelectric generation to recover low grade waste heat as
Geothermal energy piles use closed loop heat exchangers embedded in reinforced concrete piles to extract heat from below ground for building heating and cooling needs. While case studies have examined heating and cooling performance, little work has been done to understand the thermo-mechanical effects on pile structural performance from thermal cycles. This project uses analytical tools to create a 3D model of an energy pile system and conduct a finite element analysis to better understand performance under real conditions.
IRJET- Modelling and CFD Simulation of Prototype of AC Plant Chiller On-Board...IRJET Journal
This document summarizes a study that models and simulates a shell and tube heat exchanger used in marine ship air conditioning plants. The study involves:
1. Modeling the geometry of a prototype shell and tube heat exchanger in Solidworks based on design calculations.
2. Meshing the model in ICEM CFD and applying boundary conditions representing different mass flow rates to simulate heat transfer.
3. Using ANSYS Fluent CFD software to analyze temperature distribution and flow patterns within the shell and tubes at 100% and 75% loading.
4. Comparing CFD results to experimental temperature data from factory acceptance trials to validate the simulation model.
The goal is to model the
THERMAL ANALYSIS OF SHELL AND TUBE TYPE HEAT EXCHANGER TO DEMONSTRATE THE HEA...IAEME Publication
This paper consists of a simplified model of shell and tube type heat exchanger having both interacting mediums as water and steam. In this paper we have first designed a shell and tube heat exchanger to heat water from 40℃ to 70℃ by steam at 140℃ temperature. The design has been done using Kern’s method in order to obtain various dimensions such as shell, tubes, baffles etc. A computer model using CATIA V5 has been developed by using the derived dimensions of heat exchanger. Then the thermal simulation in ANSYS has been performed by applying several thermal loads on different faces and edges. The heat transfer capabilities of several thermal materials have been compared by assigning different materials.
Ch 2 - Steady state 1-D, Heat conduction.pdfAyaAya64793
This document discusses heat conduction through plane walls and hollow cylinders. It introduces the concepts of one-dimensional steady-state heat conduction without heat generation. The differential equation for heat conduction is derived for plane walls and cylindrical coordinates. Methods to solve for temperature distributions and heat fluxes are presented, including the use of thermal resistance networks and overall heat transfer coefficients. Multilayer walls and composite materials are also analyzed.
QUENCHING CRACK ANALYSIS OF BIG SIZE FORGING BY FE ANALYSISIAEME Publication
Heat treatment crack is one of the main defects of big size forging manufacturing
process. In this research finite element method has been applied to predict crack
initiation by mass effect during water agitation cooling. Cooling curve of specimens
was measured water quenching test and convective coefficients were calculated by
inverse method based on finite element method. Water quenching processes were
analyzed by Deform software and Jmatpro. Crack initiation has been predicted by
comparison of stress distribution and strength on the temperature basis
This document discusses the thermal and hydraulic design of brazed aluminum plate-fin heat exchangers. It covers topics such as single and multiple banking configurations, multi-stream designs, thermal design procedures and relationships, hydraulic design considerations, and the selection of fin geometry. Key points include defining the components of heat transfer surface area and pressure drop, methods for calculating overall heat transfer coefficients and temperature differences, and considerations for single-phase versus two-phase stream calculations.
This document summarizes a study on using computational fluid dynamics (CFD) to model and analyze the heat transfer performance of ceramic heat exchangers with different duct cross-sectional shapes (rectangular, elliptical, cylindrical). CFD was used to calculate parameters like temperature distribution, velocity distribution, heat transfer rate, and effectiveness. The predicted heat transfer rate from CFD analysis was found to be 15% higher than theoretical calculations. Analysis showed that cylindrical ducts had the highest effectiveness at 62%, followed by elliptical at 55% and rectangular at 52%. The document also provides background on the need to improve energy efficiency and reduce emissions, and discusses objectives, assumptions, and modeling steps of the CFD analysis.
Similar to Published - Badovli Thermal Analysis (20)
2. 3 Analysis assumptions
The following assumptions have been applied in the
current analysis:
(1) Concrete is considered Isotropic & Homogeneous
consequently all of the thermal properties are the same
in all directions.
(2) Thermal and structural properties of concrete are
constant for all of temperature and time intervals.
(3) The Nonlinear effect of temperature on heat
generation rate has been considered in the analysis.
This is an important factor in calculation of temperature
in concrete.
(4) The Analysis will be performed in the plane of
the dam. (2 - dimentional thermal analysis)
(5) The Compressive strains in the dam body will be
neglected conservatively.
may occure in the colder months of the first or second
year after the construction. These type of cracks are
nearly closed after reduction of the Surface thermal
gradient .
Mass gradient cracking of concrete can be visible
after final cooling of the internal part of the mass and
this may take even many years.
4 Dam section geometry
Fig. 2 shows the largest block of the dam. The crest
elevation is 1,664.5 m. the height of dam is 98.8 m. The
lower part of main monolith, acts as cofferdam during
construction. The embedded parts such as irrigation
and water intake pipes have been located in this part.
Since this part of the dam should be constructed in
the diyersion stage and RCC mixes may not be
available at that time. based on the proposal of the
contractor this part may'be constructed as Conventional
concrete.
~
= T2
>T1
.9
~
.a
£~
0
v
e00
v
"0
t2
t1
time
All
J1
Where: te is equivalent age at reference curing temperature;
dt is chronological time interval, h;
T is average concrete temperature during time
.interval dt;
To is reference temperature, °C (20°C or 293 K
for cement);
Eo is activation energy, J/mol and R is universal
gas constant.
Heat generation of the concrete is also a function of
time. This function can be expressed as below form:
Q=Qm(l-e-m.tcr
) (3)
In the above equation, Qm is total heat of concrete,
m is a coefficient depends on the Type of cement, and
te is the equal age which can be calculated based on
Maturity of concrete.
Tensile stress due to the concrete cooling can be
expressed as Eq. (4):
u=k . a . E . iYl' (4)
In this equation, compressive stresses have been
neglected conservatively. This is due to the higher
creep in the early ages after concrete placement. k is
the total restraint (foundation and geometry), E the
elasticity modulus and aT the cooling degree of the
concrete element in the dam.
Fig. 1. Factors affecting the degree of hydration of concrete
2 Thermal cracking in RCC dams
7 +1,653.5
Two different types of Thermal cracking can be
expected in Conventional Concrete and Roller Compacted
concrete dams: Mass Gradient cracking & Surface
gradient cracking.
Surface gradient cracking caused by the tensile
stresses induced due to the temperature difference
between surface and internal part of the massive
concrete structure. Mass gradient cracking is a dangerous
the~ cracking that caused by restraint against the
movement of total mass of the dam during cooling up
to the fmal stable temperature. these type ofcracks can
c~use large amount ofleakage in concrete dams.
Normally Surface gradient cracks are narrower and
616
0.85
Rce
g 1,58820
evc
Fig. 2 Typical Cross Section of Badovli Dam
The lower part modelled in 1 meter lifts with time
3. interval of 5 days. This is due to the lack of pre-cooled
aggregates in that time. The RCC part will be
constructed in 0.3 m lifts and 1 day between two
successive list left. Upstream and downstream face
concrete thicknesses are 1.5 & 1.0 meter of air
entrained concrete to provide enough durability against
freezing and thawing.
5 Environmental condition
Continue
Property Rce eve
Thermal Expansion Coeff. 8.8xl0-6
8.8xI0-6
Elasticity Modulus (Gpa) 18 22
Tensile strain capacity-Rapid 80J.l 100 J.l
Tensile strain capacity-Slow 110 J.l 150 J.l
Poisson ratio 0.2 0.2
6 Concrete mix designs
Based on mentioned results, the Qm and m will be
72 callgram and 0.206 respectively.
Based on the Laboratory results, RCC and CVC mix
designs consist of 160 kg and 220 kg of cementitious
materials respectively. Cement Type is Natural Portland
pozzolanic Cement (IP). the results of heat of hydration
test (Based on ASTM CI86), is in the Table 1.
Table 1 Heat of hydration of Uromia IP
cement based on ASTM C186
8 Finite element model
ANSYS finite element program was applied for
modeling and analysis. This software has excellent
capabilities of modeling concrete structures temperature
& construction procedure effect on the internal
temperature of the dam. The Model consists of 2,193
PLANE77 Elements and 6,871 Nodes. This type of
element, with its great features, enables user to model
temperature in the dam body. By using kill option, the
user will be able to model construction effects .The
geometry of the generated mesh for BADOVLI has
been modified to present a reliable model for getting
the required data's.
BADOWLI THERMALANALYSIS
72
28 d
Heat of hydration(caVg)
55
7d
Badovli Dam site is a cold region; the average annual
temperature of dam-site is about 8.9 °C. The sinusoidal
function of the temperature in Badovli may be
expressed as below:
Temp(t) = 8.2 +11.2sin 27[(t - 95) (5)
365
Where: t is the temperature and t is time in days from
beginning of the year. The maximum and minimum
monthly average temperature is 19.4 °C and -3°C
respectively.
7 Thermal and structural properties Fig. 3 Meshed dam body
Thermal and structural properties are shown in the
Table 2. . 9 Placing Temperatures
617
Property RCC cvc
Thermal diffusivity(m2
/d) 0.113 0.113
Specific heat [J/(kg.oC)] 950 950
Density (kglm3
) 2,420 2,420
Thermal Surface transmit ion-
60 60coeff [kcall(m
2
.h·C)]
..... ,
Table 2 Thermal & structural properties
of RCC and evc
According on US Army the placing temperature of the
roller compacted concrete calculated as Table 3.
Based on these temperatures, RCC shall be started
in the February and ended in the November Before the
temperature falling below 5 °C. during the winter
RCC shall be protected form the low temperatures. in
the next year RCC placing will be started in February
again. Time interval between successive lifts is about
1 day, and a maximum volume of 1,500 m3
/d predicted
to be placed.
4. Table 3 Ree and eve placing temperatures
RCC Placing Temperature in BADOVLI Dam
Jan.* Feb.* Mar. Apr. May June July Aug. Sep. Oct. Nov.* Dec.*
- 8.9 10 10 10 10 10 10 8.5 - -
* Indicates that in these months the placing should be stopped.
1.00 P""-lIlii~--r---,----r-------r---....,.--------.
A =0.035,825
B =0.188,592
C =0.341, 359
D =0.494, 127
E =0 .646, 894
F =0.799, 661
G =0.952, 428
H = 1.105
I 1.258
and restraint is high. So it is reasonable to expect mass
concrete gradient cracks are started from the middle
part.
Fig. 5 Restraint factor for Badovli Dam body (perpendicular
to dam axis)
Restraint factors of Fig. 4 & Fig. 5 .are calculated
based on the overall cooling of dam, While in a real
case, because of differential cooling of the dam, these
restraints may be increased. This effect bas been
considered in the current analysis for Badovli Dam.
It sh?uld be noted that the mass gradient cracking
sball be checked along dam axis and perpendicular to
dam axis. Cracking perpendicular to dam axis
(transverse cracks), will endanger the water tightness
and longitudinal cracking may divide dam section in
to two or more column that will oscillate separately
during the earth quake and the dam may not be stable
in this condition.
11 Surface gradient analysis
6040 50
Height above foundation (m)
---- Joint-dist=45m.
-._. Joint-dist=9Om
3010
--+-Joint-dist=30m
-Joint-dist=15m
0.90 tfr;;-~~---+---I----+---+-----I
6
] 0.80 t-t-~~---+---+----+---1--~
.s 0.70 ~1f-T-+~--+---+----+---1-----I
CI:S
~ 0.60 ~t"*-T+-~-+---I----+---+-----I
~
0.50 t--....-t.....,...------.,;=v---+----+---I--~
0.40 t---t:::-T-t'~-~T_-+----+---1--~
0.30 t---t----r.:~--+--~+----+---+--___I
020 J----t-+r-~-+---~~-+---I--___I
0.10 I----,...-+-~r_i~--I---~---I--___I
'''-0.00 1....-----.-~.....~~I:lI:::l1IIiI...~t__~. . . . ....._...
o
10 Restraint Factors
Restraint factor for badowli dam -along crest
( crown-cantilever)
Restraint factors in dam body calculated by using a
comprehensive 3d model. The results have been
shown in the Fig. 4 & Fig. 5.Transverse joint spacing
has a major effect on the restraint factor and tensile
thermal stresses induced in dam body parallel to dam
axis.
When total volume of the dam body cools down
simultaneously and homogenously, the foundation
restraint effect may decrease the stresses. Because this
is not true due to the variations in peak temperature of
concrete in different points, so it is reasonable to
neglect this effect.
So the low modulus of the foundation rock may
decrease the thermal stresses of dam body slightly, but
in the analysis this effect has been neglected
conservatively.
618
Rg. 4 Restraint factor for Badovli Dam with different contraction
joint spacings (along dam axis)
As shown in Fig. 4, when the joint spacing increases,
the restraint against thermal movement of the dam
also increases for a specified point in the dam, and
restraint in the middle part is higher than 'that of
upstream and downstream faces. So it is reasonable to
e~pect that mass gradient cracks to be started from the
. middle part of the dam where both of the temperature
Because Badovli Dam has been located in a cold
region, the temperature gradient between core and
surface may cause cracking so it is necessary the
strains shall be calculated in the analyses and the
surface tensile strain shan be checked to be less than
cr~ckiDg strain for the concrete with consideration of
contraction joint effects.
Fig. 6 shows induced strains in the dam body after
placing 20 meters ofevc in the lower part of the dam.
5. As can be seen, the maximum tensile strain is
117micro in z direction, which is higher than short-term
tensile strain capacity of the CVC (Table 2). The crack
spacing will be more than 50 meters that is higher than
maximum joint space, so the cracking doesn't occur.
Internal part of the dam is under compressive
strains that can be tolerated by RCC safely. After
ending the frrst winter, surface of concrete will be
covered by roller compacted concrete, so the fIrst
winter is almost the worst condition for this concrete
form thermal stresses view point.
It is planned that the major part of the aggregate to
be produced in the colder months. RCC should be
placed with a temperature not more that 10°C.
Since the most probable occurrence time of the
surface gradient cracking is the first or second winter
The Isothermal and strain contours have been shown
in these two seasons (Fig. 7 and Fig. 8). As it can be
seen the maximum tensile strain in the second winter
due to temperature gradient is 160 micro that is more
than tolerable strain by RCC (100 micro strain).
Because the contraction joints in the dam, are
designed to be located at a maximum 19 meters
distance, and this tensile strain may produce a
cracking distance about 33 meters so the cracking
doesn't occur. So the dam is safe against surface
cracking.
BADOWLI THERMAL
ANAL YSIS
ANSYS5.4
DEC 12005
22:45:06-
Nodal solution
TIME=155
TEMP (AVG)
RSYS=O
Power graphics
EFACET=1
AVRES=Mat
SMN=- 3.307
SMX=24.989
A =-1.735
B =1.409
C =4.553
D=7.697
E =10.841
F =13.985
G =17.129
H =20.273
I =23.417
BADOWLI THERMAL
ANAL YSIS
ANSYS5.4
DEC 1 2005
22:51:56
Nodal solution
STEP=1
SUB=1
TIME=1
EPTOZ (AVO)
RSYS=O
Power graphics
EFACET=1
AVRES=Mat
DMX =0.001,504
SMN =-0.882E-04
SlvIX =0. 160E-03
A =- 0.744E-04
B =-467E-04
C =-191E-04
D =0.851E-05
E =0.361E-04
F = 0 .638E-04
G =0.914E-04
H =0.119E-03
I =0.147E-03
Fig. 6 Isothermal contours (left) and thermal strains (right) in the lower part (CVC) of the dam body
BADOWLI THERMAL
ANAL YSIS
BADOWLI THERMAL
ANAL YSIS
ANSYS5.4
DEC 2 2005
19:34:23
Nodal solution
STEP=1
SUB=1
TIME=1
BFETEMP (AVG)
DMX =0.003, 307
SMN =-3.887
SMX=29.442
A=- 2.036
B=1.668
C=5.371
D=9.074
E=12.777
F=16.48
G=20.148
H=23.887
1=27.59
ANSYS5.4
DEC 2 2005
19:34:37
Nodal solution
STEP=l
SUB=I
TIME=1
EPTOZ (AVG)
RSYS=O
Power graphics
EFACET=l
AVRES=Mat
DMX = 0 .003, 301
SMN =-0.143E-03
SMX =0.I64E-03
A=-0.126E-03
B =-0.917E-04
C =- O. 576E- 04
D =-0.235E-04
E =0.105E-04~.-:::...- --r- ....:::..-~ F =0. 446E-04
G =0.787E-04
H =0.1l3E-03
I =0.147E-03
Fig. 7 (Left) Isothermal contours at second winter (Right) thermal strain in the dam body in the second winter
(at 540 days after starting the construction of the dam)
12 Mass gradient cracking
In order to investigate the mass gradient cracking
occurrence, the temperature history in different
locations of dam body have been calculated by using
the Finite element model. The cooling of dam body up
to 4,500 days after start of the construction, have been
modeled. The maximum temperature in the dam body
is 30.4 °C. The maximum mass gradient in the dam
body is 26.1 °c in the height of 52 meters of the dam.
This Gradient produces a crack distance of 50 m that
is more than maximum contraction joint distance of
619
6. dam body and mass gradient cracking doesn't occur.
The Temperature histories at different nodes are
shown in the Fig. 9. Node 3,554 is in the middle part
of the dam and in the height of 49 meters above the
foundation. Node 3,830 is Near Upstream face at the
same height. So due to the effect of the surrounding
air, some temperature oscillation can be seen in this
node. Node 4,031 is also in the middle part between
upstream and downstream of the dam and 54 meters
above the foundation. After almost 3,500 days, the
dam body reaches to its final stable temperature that is
8.5 C for Badovli Dam.
Because of 3 d nature of real temperature flow, the
real temperature history might show some discrepancy
from the analysis results. However, the maximum and
minimum temperature will be the same.
ANSYS5.4
DEC 2 2005
17:34:46
Nodal solution
TIME =400
TEMP (AVG)
RSYS=O
Power graphics
EFACET=1
AVRES=Mat
SMN=5
SMX=30.22
A =6.401
B=9.203
C=12.006
0=14.808
E =17.61
F =20.412
G=23.215
H=26.017
1=28.819
ANSYS5.4
DEC 2 2005
17:34:11
Nodal solution
TIME=lOOO
TEMP (AVG)
RSYS=O
Power graphics
EFACET=l
AVRES=Mat
SMN =3.483
SMX=23.841
A =4.614
B =6.876
C =9.138
0=11.4
E =13.662
F =15.924
G =18.186
H=20.448
1=22.71
Badowli thennal analysis Badowli thermal analysis
Fig. 8 (left) Isothermal contours at 400 days after start (right) Isothermal contours at 1000 days after start of placing
Temperature history ofdifferent nodes
35 r----..,-----,------,------r------,
e30 1---.r.--+----4-----I-----+----I
G)
·S 25 t--l ~+----4-----I-----+----I
G
~ 20
~ 15 1--t-t-'"'II'-ir+:PI--..~~----I-----+----I
10 I-JjL-Y-+J-U~~~~-i..£.rL_~
51----+---=---JlL-Y~~~I:.f.-_t.:H___Ir¥_-___I
o 1,000 2,000 3,000 4,000 5,000
TlJDe(d)
-Node 35S4 .......Node 3830 ---Node 4031
Fig. 9 Temperature history at different nodes
13 Conclusions
All of the analyses were done based on the RCC
placement in 9. months. Based on analysis no major
crack which endangers dam performance and its water
tightness is expected in future.
In this design stage analysis, the foundation restraint
factor considered to be 100%.
(1) The heat liberation rate of the cement has a
great influence on the heat storage in the concrete
. inass. So including the effect of temperature on cement
hydration in the thennal analysis of RCC dams, especially
in cold areas, results in higher peak temperature in the
concrete. This is due to the retarding effect of low air
temperature on hydration of concrete.
(2) Controlling Surface gradient cracking especially
in the cold regions has a great degree of importance.
Because surface cracking may be harmful for water
tightnes.s of the dam.
(3) fu the lower part of the dam, restraints against
movement of the dam due to the thermal shrinkage are
high so the risk of thermal cracking will be higher in
this part. In the Badovli Dam, the maximum temperature
of lower part has been limited to 25°C to control
cracking parallel to dam axis and between contraction
joints.
References
[ 1] ACI 207.2R - 95. Effect of Restraint, Volume
Change, and Reinforcement on Cracking of Mass
Concrete
[2] ACI 207.1R. Mass Concrete
[3] ACI 207.4R. Cooling and Insulating. Systems for
Mass Concrete
[4] ACI 209.R. 92. Prediction Of Creep, Shrinkage
and Temperature Effects in Concrete Structures
[5] ASTM CI074. Standard Practice for Estimating
620
7. Concrete Strength by the Maturity Method
[6J ANSYS 5.4ADPL. User's Manual
[7 J F.R.Andriolo. The Use of Roller Compacted
Concrete
[ 8J Bentz and de Larrard, "Prediction of Adiabatic
Temperature Rise in Conventional and High
Performance Concretes Using a 3-D Micro structural
Model". Cement and Concrete Research
[9J P, Kumar Mehta & Paulo. J. Monteiro. Concrete:
Microstructure, Properties, and Materials
[ 10J Andrade, F.R.Andriolo, Thennal Analysis of Roller
Compacted Concrete
[ 11] Hamidreza Araghian, Thermal Analysis of
RAEESALI DELVAJU dam
621