This paper presents a theoretical approach to the design of gravity-assisted heat pipe heat excha... more This paper presents a theoretical approach to the design of gravity-assisted heat pipe heat exchangers (GAHPHE). Based on this analysis, the variation of overall effectiveness of GAHPHE with CJCo for different values of: tube spacing normal to the direction of flow; number of fins per metre; fin thickness and evaporator and condenser lengths, are plotted. Furthermore, in order to obtain an optimum design for GAHPHE, the variation of overall effectiveness with conductance ratio for different values of modified number of transfer units, for a rather broad design range, is presented.
International Journal of Low-Carbon Technologies, 2012
The use of the heat pipe as a component in a heat recovery device has gained worldwide acceptance... more The use of the heat pipe as a component in a heat recovery device has gained worldwide acceptance. Heat pipes are passive, highly reliable and offer high heat transfer rates. This study summarizes the investigation of different types of heat pipe heat recovery systems (HPHRSs). The studies are classified on the basis of the type of the HPHRS. This research is based on 30 years of experience on heat pipe and heat recovery systems that are presented in this study.
ABSTRACT This paper presents a theoretical approach to the design of gravity-assisted heat pipe h... more ABSTRACT This paper presents a theoretical approach to the design of gravity-assisted heat pipe heat exchangers (GAHPHE). Based on this analysis, the variation of overall effectiveness of GAHPHE with , for different values of: tube spacing normal to the direction of flow; number of fins per metre; fin thickness and evaporator and condenser lengths, are plotted. Furthermore, in order to obtain an optimum design for GAHPHE, the variation of overall effectiveness with conductance ratio for different values of modified number of transfer units, for a rather broad design range, is presented.
Abstraet--A co-axial heat pipe solar collector was built and tested at MERC. The measured el~cien... more Abstraet--A co-axial heat pipe solar collector was built and tested at MERC. The measured el~ciencies for half-hour periods over a range of temperature differences between the average fluid temperature (average of inlet and outlet) and the ambient air temperature divided by the insolation are presented.
ABSTRACT This paper presents a theoretical analysis of multi-stage heat pipe heat recovery system... more ABSTRACT This paper presents a theoretical analysis of multi-stage heat pipe heat recovery system. In this study thermal performance and temperature profile in flow direction both evaporator and condenser sections of the heat pipe heat recovery system were developed.
A theoreUcal study on the thermal performance of a circular finned heat ptpe heat recovery system... more A theoreUcal study on the thermal performance of a circular finned heat ptpe heat recovery system was developed to predict the temperature distribution in the longitudinal rows both for evaporator and condenser sechons of the heat recovery system
This paper describes a theoretical analysis of co-axial heat pipe heat exchanger (CAHPHE). The an... more This paper describes a theoretical analysis of co-axial heat pipe heat exchanger (CAHPHE). The analysis is based on NTU-effectiveness approach to deduce its heat transfer characteristics. In this study the variation of overall effectiveness of CAHPHE with CJC c is presented and the effects of the number of rows of co-axial heat pipes on the thermal performance of the exchanger were determined. NOMENCLATURE A heat transfer area [m 2] Cc flow-stream capacity rate of cold-side fluid [WK-~] C, flow-stream capacity rate of hot-side fluid [WK-~] C I heat pipe working fluid capacity rate [WK -~ ] Cp specific heat at constant pressure [J Kg-t K-i ] C exchanger flow-stream mass velocity [kg m-2 s-t ]
ABSTRACT This paper presents a theoretical study of an air-to-water heat pipe heat exchanger. In ... more ABSTRACT This paper presents a theoretical study of an air-to-water heat pipe heat exchanger. In this study the variation of heat exchanger effectiveness with ratio of cold to hot flow-stream capacity rate for 8, 10 and 12 rows are presented.
Al~traet--This paper describes a design study on a water-to-air gravity-assisted heat pipe heat e... more Al~traet--This paper describes a design study on a water-to-air gravity-assisted heat pipe heat exchanger. The characteristics of the heat exchanger are studied analytically to present the performance of the heat exchanger. The variation of overall effectiveness of exchanger with Ce/Cc and Re* for different values of Cc are plotted and also overall effectiveness as a function of outlet air temperature from the exchanger to a solar dryer with and without a heat recovery unit are presented. NOMENCLATURE A Ac c, c~ c~ c,, d E FI G g g~ h J k /,.
This paper presents a theoretical and experimental study of a solar water heater using gravity-as... more This paper presents a theoretical and experimental study of a solar water heater using gravity-assisted heat pipes with methanol as the working fluid.
ABSTRACT Analytical studies were conducted to investigate the thermal performance of a heat pipe ... more ABSTRACT Analytical studies were conducted to investigate the thermal performance of a heat pipe heat exchanger to recover thermal energy from exhaust hot gas from a boiler, in order to replace a conventional heat recovery system (Ljungstrom) in the steam power plant.
New comparative tests on three different types of heat pipe solar collectors are presented in thi... more New comparative tests on three different types of heat pipe solar collectors are presented in this paper. These three collectors are installed in parallel and tested at the same working conditions.
ABSTRACT The performance of heat pipe solar collector is investigated theoretically and experimen... more ABSTRACT The performance of heat pipe solar collector is investigated theoretically and experimentally. The system employs wick-assisted heat pipe for the heat transfer from the absorber (evaporator) to a heat exchanger (condenser). The heat pipe is made with a copper tube and the evaporator section is finned with aluminium plate. Theoretical model predicts the outlet water from heat exchanger, heat pipe temperature and also the thermal efficiency of solar collector. The results are compared with experimental data.
The thermal performance of co-axial heat pipe solar collector which consist of a collector 15 co-... more The thermal performance of co-axial heat pipe solar collector which consist of a collector 15 co-axial heat pipes surrounded by a transparent envelope and which heat a fluid flowing through the condenser tubes have been predicted using heat transfer analytical methods. The analysis considers conductive and convective losses and energy transferred to a fluid flowing through the collector condenser tubes.
ABSTRACT A theoretical model has been developed to investigate the thermal performance of a conti... more ABSTRACT A theoretical model has been developed to investigate the thermal performance of a continuous finned circular tubing of an air-to-air thermosyphon-based heat pipe heat exchanger. The model has been used to determine the heat transfer capacity, which expresses the thermal performance of heat pipe heat exchanger. The model predicts the temperature distribution in the flow direction for both evaporator and condenser sections and also the saturation temperature of the heat pipes. The approach used for the present study considers row-by-row heat-transfer in evaporator and condenser sections of the heat pipe heat exchanger.
ABSTRACT An indirect forced circulation solar water heating system using a flat-plate collector i... more ABSTRACT An indirect forced circulation solar water heating system using a flat-plate collector is modeled for domestic hot water requirements for the people living in Hadji-abad village. This project is designed using F-chart. The water heating load or the amount of energy required to warm water from the inlet cold water to a desired temperature, is dependent on several factors such as hot water consumption rate, cold water inlet and desired hot water set temperatures, location and orientation of the building. The system was installed to supply hot water for 12 showers and 4 private baths for a public bath complex to serve the hot water demands throughout the year for 150 people per day. The system was built in 2004 in the village of Hadji-abad near the city of Birjand in the eastern part of Iran. The installation is composed of two solar collector fields (195m2) and two storage tanks (of 3m3 capacity each). This paper emphasizes the factors associated with subsystems that are required to extract heat from 195m2 solar collectors, store this heat in two thermally insulated hot water storage tanks and the heat distribution system with electrically operated pumps for water circulation. The results show that by utilizing solar energy, the designed system could provide the total hot water demands.
This paper presents a theoretical approach to the design of gravity-assisted heat pipe heat excha... more This paper presents a theoretical approach to the design of gravity-assisted heat pipe heat exchangers (GAHPHE). Based on this analysis, the variation of overall effectiveness of GAHPHE with CJCo for different values of: tube spacing normal to the direction of flow; number of fins per metre; fin thickness and evaporator and condenser lengths, are plotted. Furthermore, in order to obtain an optimum design for GAHPHE, the variation of overall effectiveness with conductance ratio for different values of modified number of transfer units, for a rather broad design range, is presented.
International Journal of Low-Carbon Technologies, 2012
The use of the heat pipe as a component in a heat recovery device has gained worldwide acceptance... more The use of the heat pipe as a component in a heat recovery device has gained worldwide acceptance. Heat pipes are passive, highly reliable and offer high heat transfer rates. This study summarizes the investigation of different types of heat pipe heat recovery systems (HPHRSs). The studies are classified on the basis of the type of the HPHRS. This research is based on 30 years of experience on heat pipe and heat recovery systems that are presented in this study.
ABSTRACT This paper presents a theoretical approach to the design of gravity-assisted heat pipe h... more ABSTRACT This paper presents a theoretical approach to the design of gravity-assisted heat pipe heat exchangers (GAHPHE). Based on this analysis, the variation of overall effectiveness of GAHPHE with , for different values of: tube spacing normal to the direction of flow; number of fins per metre; fin thickness and evaporator and condenser lengths, are plotted. Furthermore, in order to obtain an optimum design for GAHPHE, the variation of overall effectiveness with conductance ratio for different values of modified number of transfer units, for a rather broad design range, is presented.
Abstraet--A co-axial heat pipe solar collector was built and tested at MERC. The measured el~cien... more Abstraet--A co-axial heat pipe solar collector was built and tested at MERC. The measured el~ciencies for half-hour periods over a range of temperature differences between the average fluid temperature (average of inlet and outlet) and the ambient air temperature divided by the insolation are presented.
ABSTRACT This paper presents a theoretical analysis of multi-stage heat pipe heat recovery system... more ABSTRACT This paper presents a theoretical analysis of multi-stage heat pipe heat recovery system. In this study thermal performance and temperature profile in flow direction both evaporator and condenser sections of the heat pipe heat recovery system were developed.
A theoreUcal study on the thermal performance of a circular finned heat ptpe heat recovery system... more A theoreUcal study on the thermal performance of a circular finned heat ptpe heat recovery system was developed to predict the temperature distribution in the longitudinal rows both for evaporator and condenser sechons of the heat recovery system
This paper describes a theoretical analysis of co-axial heat pipe heat exchanger (CAHPHE). The an... more This paper describes a theoretical analysis of co-axial heat pipe heat exchanger (CAHPHE). The analysis is based on NTU-effectiveness approach to deduce its heat transfer characteristics. In this study the variation of overall effectiveness of CAHPHE with CJC c is presented and the effects of the number of rows of co-axial heat pipes on the thermal performance of the exchanger were determined. NOMENCLATURE A heat transfer area [m 2] Cc flow-stream capacity rate of cold-side fluid [WK-~] C, flow-stream capacity rate of hot-side fluid [WK-~] C I heat pipe working fluid capacity rate [WK -~ ] Cp specific heat at constant pressure [J Kg-t K-i ] C exchanger flow-stream mass velocity [kg m-2 s-t ]
ABSTRACT This paper presents a theoretical study of an air-to-water heat pipe heat exchanger. In ... more ABSTRACT This paper presents a theoretical study of an air-to-water heat pipe heat exchanger. In this study the variation of heat exchanger effectiveness with ratio of cold to hot flow-stream capacity rate for 8, 10 and 12 rows are presented.
Al~traet--This paper describes a design study on a water-to-air gravity-assisted heat pipe heat e... more Al~traet--This paper describes a design study on a water-to-air gravity-assisted heat pipe heat exchanger. The characteristics of the heat exchanger are studied analytically to present the performance of the heat exchanger. The variation of overall effectiveness of exchanger with Ce/Cc and Re* for different values of Cc are plotted and also overall effectiveness as a function of outlet air temperature from the exchanger to a solar dryer with and without a heat recovery unit are presented. NOMENCLATURE A Ac c, c~ c~ c,, d E FI G g g~ h J k /,.
This paper presents a theoretical and experimental study of a solar water heater using gravity-as... more This paper presents a theoretical and experimental study of a solar water heater using gravity-assisted heat pipes with methanol as the working fluid.
ABSTRACT Analytical studies were conducted to investigate the thermal performance of a heat pipe ... more ABSTRACT Analytical studies were conducted to investigate the thermal performance of a heat pipe heat exchanger to recover thermal energy from exhaust hot gas from a boiler, in order to replace a conventional heat recovery system (Ljungstrom) in the steam power plant.
New comparative tests on three different types of heat pipe solar collectors are presented in thi... more New comparative tests on three different types of heat pipe solar collectors are presented in this paper. These three collectors are installed in parallel and tested at the same working conditions.
ABSTRACT The performance of heat pipe solar collector is investigated theoretically and experimen... more ABSTRACT The performance of heat pipe solar collector is investigated theoretically and experimentally. The system employs wick-assisted heat pipe for the heat transfer from the absorber (evaporator) to a heat exchanger (condenser). The heat pipe is made with a copper tube and the evaporator section is finned with aluminium plate. Theoretical model predicts the outlet water from heat exchanger, heat pipe temperature and also the thermal efficiency of solar collector. The results are compared with experimental data.
The thermal performance of co-axial heat pipe solar collector which consist of a collector 15 co-... more The thermal performance of co-axial heat pipe solar collector which consist of a collector 15 co-axial heat pipes surrounded by a transparent envelope and which heat a fluid flowing through the condenser tubes have been predicted using heat transfer analytical methods. The analysis considers conductive and convective losses and energy transferred to a fluid flowing through the collector condenser tubes.
ABSTRACT A theoretical model has been developed to investigate the thermal performance of a conti... more ABSTRACT A theoretical model has been developed to investigate the thermal performance of a continuous finned circular tubing of an air-to-air thermosyphon-based heat pipe heat exchanger. The model has been used to determine the heat transfer capacity, which expresses the thermal performance of heat pipe heat exchanger. The model predicts the temperature distribution in the flow direction for both evaporator and condenser sections and also the saturation temperature of the heat pipes. The approach used for the present study considers row-by-row heat-transfer in evaporator and condenser sections of the heat pipe heat exchanger.
ABSTRACT An indirect forced circulation solar water heating system using a flat-plate collector i... more ABSTRACT An indirect forced circulation solar water heating system using a flat-plate collector is modeled for domestic hot water requirements for the people living in Hadji-abad village. This project is designed using F-chart. The water heating load or the amount of energy required to warm water from the inlet cold water to a desired temperature, is dependent on several factors such as hot water consumption rate, cold water inlet and desired hot water set temperatures, location and orientation of the building. The system was installed to supply hot water for 12 showers and 4 private baths for a public bath complex to serve the hot water demands throughout the year for 150 people per day. The system was built in 2004 in the village of Hadji-abad near the city of Birjand in the eastern part of Iran. The installation is composed of two solar collector fields (195m2) and two storage tanks (of 3m3 capacity each). This paper emphasizes the factors associated with subsystems that are required to extract heat from 195m2 solar collectors, store this heat in two thermally insulated hot water storage tanks and the heat distribution system with electrically operated pumps for water circulation. The results show that by utilizing solar energy, the designed system could provide the total hot water demands.
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