Mathematical modeling of the transient operating characteristics of a low-temperature heat pipe

A computational model has been developed based on finite-difference approximations for predicting the transient operating characteristics of low-temperature heat pipes. To stimulate startup from the supercritical state, a simplified cooldown is modeled using bulk liquid flow through the capillary structure with phase change at the liquid front. Variations of thermal properties are considered using cubic spline interpolation, and nodal temperatures are calculated by an alternating direction implicit method. A fluid gap in the wick and a variety of thermal couplings have been incorporated in the model. Comparisons between predicted and experimental values were made on a refrigerant 11 heat pipe, and agreement is good for normal operation. For cooldown from the supercritical state, the present model predicts operating trends of the device and correct final steady-state performance.