Effect of different charge ratios on transient performance of a flat type of the LHP with a shared compensation chamber

Abstract

In this paper, the loop heat pipe (LHP) with a shared compensation chamber (SCC) has been put forward, and the SCC must supply working fluid to two primary wicks in the opposite replenishment way. Thus, charge ratio of the working fluid would have a great influence on operating behaviors of this new LHP system. Through the calculation, the optimal charge ratio for this new system ranged from 0.69 to 0.77. In this investigation, transient performance of this system were analyzed at charge ratio of 60% (below the optimal value) and 75% (optimal value), respectively. With the evaporator temperature below (90 ± 2)°C, the experimental results showed that the LHP system could start up successfully at the given heat load range when one side was only heated or two sides were heated simultaneously. With Charge ratio fixed at 60% and the LHP system in the horizontal orientation, startup tests with two sides manifested reverse direction of fluid circulation because of heat leak from two heating sides. For the LHP system with 100 of tilt angle (the condenser above the evaporator), startup with one side could enter into steady state at the heat load ranging from 10 W to 140 W. However, with charge ratio increasing to 75% and the LHP system located at 10° of tilt angle, operating performance with two sides was greatly improved, and the total transferred maximum heat load reached up to 240 W. Especially at low heat load ranges, the LHP system stability was obviously improved. Otherwise, continuous operation with two sides was tested, and the total thermal resistances of two different cases were discussed based on parallel electrical resistance analysis.