Experimental performance of R134a-filled and water-filled loop heat pipe heat exchangers.

K S Ong, Journal Heat Transfer Engineering, 2010

Experimental investigations were conducted to compare the thermal performances of a thermosyphon heat pipe heat exchanger (THPHE) and a loop heat pipe heat exchanger (LHPHE) for hot and cold energy recovery for air conditioning purposes. For such applications the heat pipe heat exchangers (HPHE’s) are operated at low temperatures. The experimental THPHE was filled with R-134a and the LHPHE with distilled water. Both exchangers were operated in the counter-current flow mode. This paper presents the experimental results obtained. The results showed that heat transfer rate increases as evaporator inlet temperature increased and as both evaporator and condenser air flow rates ncrease. Overall effectiveness was found to approach a minimum when both air streams have equal velocities. Overall effectiveness of up to 0.90 could be achieved from the THPHE or the LHPHE.