Experimental study of the loop heat pipe with a flat disk-shaped evaporator

A miniature loop heat pipe (LHP) with a flat evaporator is a promising solution for dealing with cooling requirements for high-power electronic devices. The present paper discusses the operating performance and heat transfer characteristics of a miniature LHP with a flat disk-shaped evaporator. It had a heated disk diameter of 40 mm and height of 19 mm, and was designed with brass as the evaporator material with braze welding, 630 mesh stainless steel wire mesh as the wick and methanol as the working fluid. In this investigation, both start-up and variable heat load tests were conducted. Three start-up modes were experimentally observed in this investigation: (1) zigzag start-up, (2) overshoot start-up, and (3) stable start-up. When the evaporator's heated wall temperature was lower than 85 °C, with a variable heat load ranging from 20 W to 240 W corresponding to the heat flux of 1.6-19.1 W/cm2, the LHP ran stably and showed good self-adjusting ability. Moreover, comparison of the impacts of sealing method for evaporator on operating performance of miniature LHP with flat-disk type evaporator was conducted. With the same structural parameters and operating conditions, the LHP with an O-ring sealing evaporator could only work stably with heat loads ranging from 30 W to 140 W, corresponding to the heat flux of 2.38-11.1 W/cm2. This work was able to verify the importance of the sealing method in improving the performance of the miniature flat type LHPs.