Critical and optimal inclination angles of two-phase closed thermosyphon under different operating conditions

Abstract

Two-phase closed thermosyphon (TPCT) is widely used and usually installed vertically, but the inclination angle has significant effects on TPCT performance. This work presents an experimental study of TPCT with water as working fluid. The critical and optimal inclination angles of TPCT under non-forced convection cooling conditions are investigated from three aspects of start-up, operating, and heat transfer characteristics at different operating temperatures. The results show that TPCT has the critical inclination angle and the optimal inclination angle. A critical inclination angle of 45° is obtained under different operating conditions. The optimal inclination angle of TPCT is 60° at the operating temperature of 80–150 °C, but it is 90° (vertical) at 150–185 °C. Furthermore, the start-up and heat transfer performance of TPCT gradually improves with the augment of heating power. This study provides a reference for future research on heat pipe performance enhancement methods and related applications, and presents experimental basis for performance changes in TPCT applications when accidental dry burning occurs.