Transient analysis of heat transfer and fluid flow in a polymer-based Micro Flat Heat Pipe with hybrid wicks

A transient analysis of a polymer-based Micro Flat Heat Pipe with hybrid wicks was performed via a solid numerical procedure. Strongly coupled velocity, temperature, and pressure fields together with phase change and significant change of vapor density are the major challenges during a heat pipe modeling. Finite volume method was used to discretize the two-dimensional unsteady Navier-Stokes governing equations while kinetic theory was used to address the condensation/evaporation at the interface. Implicit approach was adopted to discretize time gradient terms. The density of the vapor core was calculated by the delay method while a new under-relaxation approach was successfully used to secure the convergence. To validate the accuracy of the present numerical model, the consistency of the numerical method was examined by different parameters and the numerical results were compared to experimental data at steady state conditions. The transformation point and transformation line criteria were introduced in the analysis for the first time to track the finalization of the evaporation and the beginning of the condensation process.