A numerical model for transport in heat pipes considering wick microstructure effects

A three-dimensional flow and heat transfer model for heat pipes and vapor chambers is presented. The Navier-Stokes equations along with the energy equation are solved numerically for the liquid and vapor flows in the heat pipe. A porous medium formulation is used for the wick region. Evaporation and condensation at the liquid-vapor interface are modeled using kinetic theory. The effect of the microstructured wick on evaporation and condensation mass fluxes at the liquid-vapor interface is accounted for by integrating a microstructure-level evaporation model (micromodel) with the device-level model (macromodel). Meniscus curvature in the wick is calculated at every location as a result of this coupling. The model accounts for the change in interfacial area in the wick pore, thin-film evaporation, and Marangoni convection effects during phase change at the liquid-vapor interface. The coupled model is used to predict the performance of a screen-mesh wick in a heat pipe and the implications of the coupling are discussed.