An Ultrathin-Walled Foam Heat Pipe

Abstract

We present an advanced thermal solution for capillary-driven heat pipes that addresses a fundamental problem with existing heat pipes being inefficient space utilization and limited thermal spreading performance. Our solution features the full occupation of open-cell foam core and ultrathin-walled envelope - an ultrathin-walled foam heat pipe (uFHP). A copper layer is formed sequentially via electroless - and electro-plating, and envelopes a tailored block of open-cell foam core, followed by a series of chemical surface treatments that create a nanoscale texture on the foam ligament and envelope's inner surfaces for improved capillary pumping. The high porosity foam core (e = 0.974) for vapor passaging and wicking, and the ultrathin-walled envelope of ~50 µm, make the uFHP remarkably lightweight (64% lighter than commercial heat pipes). Further, conductive spreading and convective transfer of heat from vapor and condensate by foam ligaments to the envelope, increase overall heat rejection. Consequently, the thermal resistance and evaporator temperature are reduced. More importantly, the uFHP could be tailored into any cross-sectional (e.g., non-circular) shape. This tailorable uFHP can be an alternative heat pipe thermal solution for extreme compact operations that require improved thermal performance.