INVESTIGATION OF HEAT PIPES AS A MEANS OF HEAT TRANSFER DEVICE FOR SOLAR THERMAL APPLICATIONS

摘要

Experimental investigation of an axial transient thermal performance of heat pipes has been carried out. An experimental apparatus was designed and constructed to produce heat pipes. Two types of heat pipes, with wick and wickless, in lengths of 1m, 1.3m and 1.6m were produced. The inclination angle of the heat pipe with respect to the horizontal ground level was varied in angles of 7°, 8°, 9° and 10°. The influence of the parameters has been observed for various configurations of the experiment to provide vital information on the performance of the heat pipes. The set up includes a hot water storage to model the heat source. Copper heat pipe with internal and external diameters of 11.7mm and 12.7mm respectively and cold water storage were used to model the heat load. Thermocouples were attached at different points to measure temperature. The initial temperature of the hot storage was 80°C. Axial temperature gradient of the heat pipes for the different configurations was measured and recorded using a data logger. Maximum condenser temperatures of 77°C and 72.29°C are obtained for heat pipes with wick for 1 m and 1.3 m respectively. For wickless heat pipes, maximum condenser temperatures of 72.37°C and 71 °C are obtained for 1 m and 1.3m respectively. These results are for the set up when there is no heat load at the condenser section. But when there is heat load at the condenser section, maximum condenser temperatures of 47.26°C and 45.62°C for heat pipes with wick are obtained for 1 m and 1.3 m respectively. For wickless heat pipes, maximum condenser temperatures of 39.55°C, 36.5 °C and 29.83°C are obtained for 1 m, 1.3 m and 1.6 m respectively. As a result of the experimental investigation, copper heat pipes can be employed to achieve low cost and compact heat exchangers for the application of solar thermal systems.