A Frozen Startup Limit for Room Temperature Heat Pipes

Abstract

Abstract The frozen startup performance of two room temperature heat pipes (one copper/water and one stainless-steel/biphenyl) was investigated. Biphenyl was selected as the second fluid due to its above ambient melting temperature of 69°C. The effects of steady-state input power, restart power, and non-condensable gas (NCG) charging on startup were examined. Also, the effects of the evaporator/ condenser length ratio were examined using the stainless-steel/biphenyl heat pipe. The presence of a non-condensable gas charge was found to have a more pronounced effect on startup characteristics than restart power or geometry. For cases typically of greater evaporator length to condenser length, the presence of NCG was not required to restart a room temperature heat pipe from the frozen state. All other cases were found to require NCG charging to successfully restart. Additionally, a previous analytical frozen startup limit developed for liquid metal heat pipes was modified for room temperature heat pipes to predict startup success/failure. It was shown that the newly developed frozen startup limit can successfully predict the startup performance of room temperature heat pipes.