Thermal-Fluid Modeling For High Thermal Conductivity Heat Pipe Thermal Ground Planes

摘要

The thermal ground plane is an advanced planar heat pipe designed for cooling microelectronics in high gravitational fields. A thermal resistance model is developed to predict the thermal performance of the thermal ground plane, including the effects of the presence of noncondensable gases. Viscous laminar flow pressure losses are predicted to determine the maximum heat load when the capillary limit is reached. This paper shows that the axial effective thermal conductivity of the thermal ground plane decreases when the substrate and/or wick are thicker and/ or with the presence of noncondensable gases. Moreover, it was demonstrated that the thermal-fluid model may be used to optimize the performance of the thermal ground plane by estimating the limits of wick thickness and vapor space thickness for a recognized internal volume of the thermal ground plane. The wick porosity plays a significant role in maximum heat transport capability. A large adverse gravitational field strongly decreases the maximum heat transport capability of the thermal ground plane. Axial effective thermal conductivity is mostly unaffected by the gravitational field. The maximum length of the thermal ground plane prior to reaching the capillary limit is inversely proportional to input power.