Evaluation of Vapor Chambers Incorporating Square-Shaped and Topology Optimized Pedestals

Air cooling of high power electronic devices is typically limited by heat spreading. Vapor chamber (VC) technology provides an effective means of heat spreading using passive two- phase heat transfer. In this research, the impact of VC base plate geometry is investigated through numerical and experimental studies. Two vapor chambers were fabricated to experimentally assess the impact of a square copper pedestal on thermal resistance and maximum heat flux. The VC without the pedestal had a total thermal resistance of 0.27 K/W for a maximum power of 560 W, and the VC with the pedestal had a total thermal resistance of 0.2 K/W for a maximum power of 695 W within the test conditions. Experimental results were compared with simulation studies to suggest local dryout occurring when a pedestal is not used. A series of parametric and topology optimization studies are then presented to offer alternative structures to improve VC performance. It is shown that a VC incorporating a pedestal lowers the maximum heat flux over a wider area at the evaporator surface, with thicker pedestals performing better, and engaging a greater number of internal compound pillar fluid return pathways, leading to enhanced performance. Optimal sizes and topologies of the pedestal are numerically investigated to clarify trade-offs in performance versus added mass.