Experimental Study of Thermosiphon Heat Pipe Heat Exchanger Using Water as a Working Fluid

الملخص

     The use of water as working fluid in thermosiphon heat pipe heat exchanger (THPHE) offers several distinct advantages over organic-based working fluid but research data appears to be still limited. In this study, the performance of water-filled heat pipe heat exchangers constructed of finned copper tubes was investigated in a test rig set up in the laboratory. Tests were carried out on heat pipe heat exchangers with two and four rows of copper tubes under different air flow rates through the condenser and evaporator, and at various evaporator inlet air temperatures of up to about 100 ^oC. The results show that the effectiveness of the heat pipe heat exchangers decreased with air flow rate; and when operating under different air flow rates through the condenser and evaporator, minimum effectiveness was found when the air flow rates were equal. It was found that the operation of the water-filled heat pipe heat exchanger required at least 20 K temperature difference between the air streams. With higher temperature difference, the effectiveness increased but the rate of increase tapered off appreciably beyond 45 K. for the range of operating conditions tested, the heat pipe heat exchanger produced marginally higher effectiveness than conventional cross-flow heat exchangers with two unmixed streams.