A robust three-dimensional numerical model for heat transfer characteristics in sintered–grooved thin flat heat pipes

In the current research, a robust three-dimensional numerical model is developed for thin flat heat pipes (TFHPs) with a hybrid sintered–grooved wick structure. Numerical simulations for laminar incompressible flow in liquid wick and ideal gas incompressible flow in the vapor core are performed to predict temperature, pressure, and velocity profiles. The model utilized non-Darcy transport through a porous wick to determine liquid flow in the liquid-wick section. The mass flow rate of the fluid at the liquid–vapor interface is modeled using kinetic theory. Furthermore, the hybrid wick structure is modeled as an inhomogeneous porous medium. Additionally, this formulation enhances the stability and convergence of the numerical solution and accelerates the solving time. The developed model is validated with experimental data, showing very good agreement with axial wall temperatures, with a maximum error of about 2% in steady-state conditions. The numerical results, including system pressure, wall temperature, mass transfer at the liquid and vapor interface, and velocity magnitude streamlines, are investigated for a comprehensive understanding of the flow physics and performance of the hybrid wick. The results show that, at heat inputs of 5, 10, 20, and 30 W, the thermal efficiency of hybrid wick TFHP is 4.9%, 10.4%, 34.38%, and 23.3%, respectively, greater than that of the grooved wick. The TFHP with a hybrid wick indicates the best thermal efficiency at a heat input of 20 W, with a thermal resistance of 0.95 K/W.