Thermal analysis of micro heat pipes using a porous-medium model

Using Darcy's equation for two-phase flows in porous media and Laplace's capillary equation, a one-dimensional model of a micro heat pipe is developed to investigate its thermal and fluid-mechanical behaviors within its capillary limitation. The effects of various parameters are incorporated into the analysis. These parameters are: the capillary number, the charge level of the working fluid, the vapor-liquid viscosity ratio, contact angle, the relative lengths of the evaporator and condenser sections, the orientation of the micro heat pipe, and the Bond number. Furthermore, comparisons with existing experimental results show that the porous-medium model is reasonably adequate for the prediction of the capillary performance limit of a micro heat pipe.