Steady state model of a loop heat pipe (LHP) with coherent porous silicon (CPS) wick in the evaporator

A theoretical study is conducted to explore the effect of different parameters on the performance of a Loop Heat Pipe (LHP). These parameters are evaporator temperature. condenser temperature, total mass charge, the tube size of piping system, and pumping distance between evaporator and condenser. This paper presents a steady state model that describes the thermodynamics, heat transfer, and fluid mechanics inside an LHP. A LHP is a two-phase device with extremely high effective thermal conductivity that utilizes the thermodynamic pressure difference that developed between the evaporator and condenser to circulate a working fluid through a closed loop. The loop heat pipe efficiently transports the heat generated by a highly localized concentrated heat source and discharges this heat to a convenient sink. The steady state LHP model is described by the conservation equations, thermodynamic relations, and capillary and nucleate boiling limits. The loop heat pipe cycle is presented on a temperature-entropy diagram. A relationship is developed to predict the ratio of the heat of evaporation to the heat leaked to the compensation chamber. This work predicts the size of a LHP, the pumping distance, and the maximum power that can be dissipated for a fixed source temperature.