Experimental investigation of startup behaviors of a dual compensation chamber loop heat pipe with insufficient fluid inventory

To address the problem of the relative orientation limit between the evaporator and the compensation chambers (CCs), a dual-compensation chamber loop heat pipe (DCCLHP) was developed, and its startup characteristics with small heat loads and insufficient fluid inventory were experimentally investigated in this work. Based on the experimental results, the conclusions below can be drawn: (1) The DCCLHP can start up reliably at small heat loads, but sometimes the temperature overshoot is rather high. (2) The startup performance of the DCCLHP is different when its evaporator and CCs are at different attitudes due to different liquid/vapor composition in the evaporator and heat leak from the evaporator to the CCs. (3) In general, evaporation in the evaporator core is inevitable, which results in a large heat leak from the evaporator to the CCs and generates large temperature overshoot during the startup process. (4) Because the superheat of liquid to initiate nucleate boiling reduces as its temperature rises, nucleate boiling can also occur in the vapor grooves although the temperature of the evaporator rises at the same rate as that of the CCs. (5) The startup performance of LHPs mainly depends on the heat load and thermal resistance between the evaporator and CCs. When the startup heat load is big enough, the DCCLHP has no start-up difficulty.