Operational characteristics of oscillating heat pipe charged with R-134a for heat recovery at low temperature

Abstract

The oscillating heat pipe could transport heat quickly using rapid self-excited two-phase flow oscillation within very simple structure than any other conventional heat pipe technologies, thus it can cause significant improvement of heat exchange performance specially for waste heat recovery at low temperature. In the present study, the thermal performance of the oscillating heat pipe heat exchangers under temperature-controlled mode was experimentally and theoretically investigated. The oscillating heat pipe with 5-turns and 20-turns were manufactured using a copper meandering tube with inner diameter of 2 mm and R-134a was used as the working fluid due to its superior heat transfer performance at low temperatures. It is found that the smaller inclination angles cause the delay of the start-up and performance degradation for oscillating heat pipe with 5-turns. However, the oscillating heat pipe with 20-turns represents the same start-up operation and thermal performance regardless of inclination angles. The suggested theoretical model well predicts the thermal performance of the oscillating heat pipe heat exchangers with 5-turns and 20-turns under conditions in which the oscillating heat pipe operates normally with high thermal performance.