Experimental study on startup performance of high temperature potassium heat pipe at different inclination angles and input powers for nuclear reactor application

Due to thermal superconductivity and great isothermality, high temperature alkali metal heat pipes have a wide range of applications in aerospace, residual heat removal systems of nuclear reactors, et at. In order to investigate the effect of inclination angle and input power on the startup performance of high temperature alkali heat pipes, systematical experiments were conducted with a high temperature wick-type potassium heat pipe heated with constant heat flux. Some distinctive experimental phenomena were observed and explained, based on which, a diagram was given to illustrate the regime category and provide a reference range for heat pipe startup. According to the experimental data and theoretical analysis, it is demonstrated that the startup performance of a high temperature wick-type heat pipe under uniform and constant heat flux is mainly influenced by capillary and viscosity heat transfer limit. In terms of startup performance, horizontal heat pipes have the highest input power capability. Comparatively, the input power capability of inclined heat pipes is obviously limited by the lack of working fluid backflow caused by over-evaporation. Additionally, the startup failure of negative inclined heat pipe is due to the negative effects of gravity. This research may provide valid experimental data for modeling heat pipe startup as well as references for heat pipe industrial applications. (C) 2019 Elsevier Ltd. All rights reserved.