Experimental Study on the Cooling Performance of the Two‐Phase Loop Thermosyphon With Square Rib in the Evaporator

ABSTRACT As an efficient cooling technique, two‐phase loop thermosyphon (TPLT) has great application prospects in power electronics, and it is necessary to improve and strengthen its cooling performance. In this study, an experimental visualization setup was set up to study the mechanism of enhancement of heat transfer by a square‐rib surface. The behaviors of bubble growth, slide, and suction were captured. Results indicate that the bubble growth promotes the disturbance of the coolant at the top of the rib and strengthens the heat transfer in the boundary layer. The large bubble sliding between the ribs significantly enhanced heat transfer on the heating surface, and the bubble suction strengthened the heat transfer away from the heating surface. The cooling performance of TPLT with various rib heights and widths was investigated. The heat transfer characteristics of the TPLT can be significantly improved by increasing the rib height or reducing the rib width. The rib height and width have little effect on the two‐phase flow characteristics of the TPLT. The experimental frictional pressure drop and heat transfer coefficient are compared with the prediction. The results indicate that the Friedel and Gungor and Winterton correlations are applicable for cooling performance prediction of TPLT.