Investigation of low power start-up characteristics of a loop heat pipe

An important problem of the all two-phase thermal transport devices is their start-up characteristics. Although Loop Heat Pipes (LHPs) are easier to start than Capillary Pumped Loops (CPLs), both devices may experience start-up problems at low powers. In this study, the low power start-up characteristics of an LHP were experimentally investigated at different loop orientations. The start-up parameters such as the superheat and the time required for evaporation were analyzed. The minimum start-up power was searched at the horizontal and vertical positions of the loop. In explaining the observed phenomena, the importance of the heat leak, and the presence of the vapor bubbles in the vapor grooves prior to start-up was emphasized.