THERMO-FLUID MODEL FOR HIGH THERMAL CONDUCTIVITY THERMAL GROUND PLANES

The thermal ground plane (TOP) 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 TGP, including the effects of the presence of non-condensable gases (NCGs). 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 TOP decreases when the substrate and/or wick are thicker and/or with the presence of NCGs. Moreover, it was demonstrated that the thermo-fluid model may be utilized to optimize the performance of the TOP by estimating the limits of wick thickness and vapor space thickness for a recognized internal volume of the TOP. The wick porosity plays an important effect on maximum heat transport capability. A large adverse gravitational field strongly decreases the maximum heat transport capability of the TOP. Axial effective thermal conductivity is mostly unaffected by the gravitational field. The maximum length of the TOP before reaching the capillary limit is inversely proportional to input power.