Experimental study on the heat transfer performance of liquid metal high-temperature oscillating heat pipes with diamond nanoparticles

In order to realize effcient thermal dissipation at high temperatures, diamond nanoparticles were added in the sodium-potassium (NaK) alloy liquid metal high-temperature oscillating heat pipes (LMHOHPs) to improve the heat transfer performance. The NaK alloy with different mass fractions (0 wt%, 0.25 wt%, 0.50 wt%, 0.75 wt%, 1.00 wt%) of diamond nanoparticles was used as the working fluids. Under the input power of 2000-3500 W and the inclination angle of 0 degrees, 30 degrees, 60 degrees, and 90 degrees, the start-up characteristics and heat transfer performance of LMHOHPs after adding diamond nanoparticles were measured and analyzed. The results showed that after adding diamond nanoparticles, the LMHOHP started more smoothly and could effectively promote the unidirectional circulation flow of the working fluid. The enhancement effects of diamond nanoparticles were more obvious at low input powers. When the inclination angle was 0 degrees, nanoparticles generally presented an enhancement effect. In this study, there was an optimal nanoparticle concentration of 0.50 wt%, which enhanced the heat transfer performance under all the investigated conditions. When the nanoparticle concentration was 0.75 % and the inclination angle was 30 degrees, the maximum enhancement rate of 15.41 % was reached at the input power was 2250 W.