Thermal performance of U-shaped and L-shaped heat pipes

Abstract

A comprehensive three-dimensional numerical model is developed to evaluate the effects of bending on the performance of both low temperature and high temperature heat pipes. The model solves for wall, wick, and vapor regions and includes the compressibility effects of the vapor. The proposed model can calculate the operating pressure and temperature of the heat pipe based on the operational and physical conditions. The effects of one 90-degree bend (L-Shaped) and two 90-degree bends (U-Shaped) are evaluated based on the hydrodynamics and thermal performance of the cylindrical heat pipes. The effects of bending on the heat pipe wall temperature are more significant for a high temperature heat pipe at a lower operating temperature range compared to a low-temperature heat pipe. The effects of bending on heat pipe is not significant if the wick of the heat pipe is not damaged due to bending and the blockage of liquid flow does not occur. In addition, if the heat pipe is operating in a horizontal plane where the evaporator and condenser are at the same level, the liquid pressure drop in the wick is not affected significantly by bending. Furthermore, the effects of gravity can be important when bending heat pipes and consideration should be given for this factor.