Numerical analysis of heat and mass transfer in heat pipe using a triple-phase coupled model

A numerical prediction model is proposed to analyze the performance of heat pipe. The model is transient and applicable to both cylindrical and Cartesian coordinate systems. The vapor flow within the vapor core, the non-Darcian liquid flow with in the porous wick, and the phase change processes at the vapor-liquid interface are considered. The triple-phase coupling is realized through boundary conditions, imposed using user-defined functions(UDFs). The model is employed to solve the hydraulic and heat transfer performance of heat pipes. A flat heat pipe and a cylindrical heat pipe are calculated to validate the model. Both steady and transient characteristics of the flat heat pipe are studied. It is found that the variation tendencies of the wall temperature difference, velocity and pressure drop of vapor and liquid are consistent. As heating power changes from 10 to 50 W, the maximum wall temperature difference rises from 0.75 to 2.41 K. The maximum velocity of vapor and liquid increases by2.977m/sand 9.72?10-5m/s, respectively. Additionally, the maximum pressure drop of vapor and liquid increases by 13.9 and 42 Pa, respectively. The heating power is found to be critical for the flow characteristics.