Experimental Investigation of a 12-Turn High Temperature Oscillating Heat Pipe

Abstract Oscillating heat pipes (OHPs) can efficiently transfer heat through the thermally excited oscillation and phase change heat transfer within a sealed, capillary-sized channels. The working fluid capable of effective evaporation and condensation plays a critical role in the OHP performance, directly influencing its thermal stability and heat transfer performance. A 12-turn high temperature oscillating heat pipe (HTOHP) charged with liquid metal, NaK (78% K) and a total length of 609.6 mm was fabricated and tested. The HTOHP was made from stainless-steel 316 tubing with an inner diameter of 3.05 mm and an outer diameter of 6.35 mm. The charged HTOHP was placed inside of a stainless-steel test chamber to 1) enclose the system to combat radiative heat influence; and 2) allow the HTOHP to be rotated to determine the inclination angle effect on the heat transfer performance of the HTOHP. The heat inputs tested for the HTOHP ranged from 500 - 3250 W for inclination angles of −30°, 0°, 30°, 60°, and 90°. Experimental results show that heat transfer performance in a HTOHP significantly depended on the power input and the inclination angle. Results show that a 12-turn tubular OHP can transfer a power up to 3250 W for which the coolant temperature of the OHP condenser was 334 °C and the evaporator temperature was 906 °C. The heat transfer performance observed under these conditions is roughly 100 times better than stainless steel on its own.