Numerical investigation of the screen mesh effects on the heat transfer performance of wick structured heat pipe

Abstract

The wick structure is the key component of heat pipe, which drives the working fluid circulation and greatly influences the heat transfer performance. This study investigated the steady state operation of heat pipes with seven different screen mesh numbers and four input powers through numerical simulation methods. A capillary force model was established to formulate the relationship between the driving force of wick structure and the effective pore size of screen mesh. The Lee model and Volume of Fluid (VOF) model were employed to simulate the phase changes and two-phase flow within the heat pipe. The numerical model was first validated by the published experiment data. The simulation results revealed that the variation screen mesh number greatly affected the internal state of heat pipe, such as the distributions of temperature, mixed velocity, and phase fraction. The equivalent thermal resistance calculated from the temperature differences of the outer wall also showed a dependence on the screen mesh number, but its sensitivity decreased as the input power increased. The underlying mechanism was interpreted by the screen mesh effects on the circulation efficiency of working fluid, which was characterized by a net mass flow into the wick region of condenser section. Moreover, a critical power concept was proposed that the heat pipe performance was governed by the balance between evaporation and condensation rates, along with the liquid volume fraction in the wick region.