Influence of Working Fluids to Heat Transfer Characteristics of Heat Exchanger using Oscillating Capillary Tube Heat Pipe for Low Temperature Waste Heat Recovery

Heat transfer characteristics of a heat exchanger for low temperature waste heat recovery using oscillating capillary tube heat pipe(OCHP) were evaluated against the charging ratio variation of working fluid and various working fluids. R-142b, R-22 and R-290 were used as working fluids. The heat exchanger was composed of heat pipe with capillary tube bundles, having a 2.6 ㎜ in outside diameter, 1.4 ㎜ in inside diameter with 101 m length and 140 turns. Charging ratio of working fluid was 40% and 50%. Water was used as secondary fluid. Inlet temperature and mass velocity for each secondary fluid were 297 K, 280 K and 9~27 ㎏/㎡s, respectively. From experimental results, it was found that heat transfer performance of R-22 was higher than those of R-142b and R-290 and it was proportional to Figure of Merit for thermosyphon. As a result, it was thought that R-22 was the most reasonable working fluid of waste heat recovery for low temperature waste heat recovery.