Experimental observation of thermal behavior of a loop heat pipe with a bypass line under high heat flux

Abstract

An experimental study was conducted to improve the steady-state thermal performance of a loop heat pipe (LHP) under high heat fluxes by employing a bypass line. The LHP had a sintered metal wick and a flat evaporator, of which the planar dimensions were 40mm×50mm. The wall and tubing system were made of stainless steel, and distilled water was used as the working fluid. The bypass line was installed between the vapor channel of the evaporator and the liquid reservoir to control the thermal performance of the LHP. A control valve was placed in the bypass line to enable changing between the normal and bypass line operation modes. An experimental investigation was conducted to identify the effect of the bypass line on the LHP performance, from the viewpoints of the temperatures at representative points and the thermal resistance. The steady-state performances of the LHPs with and without the bypass line were analyzed and compared with each other, under thermal loads of 100 W–260 W (21.2 W/cm2). Typical results showed that the evaporator wall temperature was decreased by approximately 45 °C, resulting in reduction of thermal resistance by 28.1 %, for the LHP with the bypass line.