Investigation of Performance of Heat Pipe as Heat Exchanger Using Alternative Refrigerants

Abstract

An experimental and theoretical study was performed to investigate the thermal performance of heat pipes as a heat exchanger. A series of experiments was conducted using R410A, R134a, R22, and R407C as working fluids. The dimensions of the heat pipes that were used in the test rig included 660 mm length, 20 mm outer diameter and 4 mm fin spacing with staggered arrangements. During the tests, the dry bulb temperature of the evaporator inlet was varied from 35 to 55°C and the condenser inlet dry bulb temperature was varied from 20 to 25°C. The influence of face velocity on the performance of the heat pipe heat exchanger was also studied. Many investigations were made to obtain the thermal performance and to ensure efficient and reliable operation of the heat pipe heat exchanger, and the results are presented in the present paper. Tests showed that using R410A, R134a, and R22 provided comparative results, whereas R407C was the least effective. The experimental thermal effectiveness of the heat pipe heat exchanger obtained from the experiments varied between 25 and 70% for R410A, R134a, and R22, whereas the experimental thermal effectiveness of R407C varied between 15 and 50%. A computer simulation program based on the effectiveness method and the number of transfer units was developed to estimate the thermal performance of the heat pipe heat exchanger and to compare the theoretical and experimental results.