Copper foam based vapor chamber for high heat flux dissipation

A copper foam based vapor chamber was designed, built and tested in this paper. The vapor chamber consists of a top and bottom copper foam pieces which are sintered on the two copper plates. Several copper foam bars directly contact the tip of the condenser and evaporator wicks. The surface temperature non-uniformity was defined to characterize the temperature distribution on the condenser and evaporator surfaces. It is found that the water and ethanol based vapor chambers have the best and worst thermal performance, respectively, among the three working fluids of water, acetone and ethanol. The surface temperature non-uniformity on the bottom (evaporator) surface are 3–5 times of those on the top (condenser) surface. Generally thermal resistances of vapor chambers are decreased with increases in heating powers. Charge ratios and inclined angles are combined to influence the thermal performance of vapor chambers. The maximum heating power attains 170 W, corresponding to the heat flux of 216 W/cm2 without the capillary or boiling limits reached. The minimum thermal resistance is 0.09 K/W. The significantly extended operation range of heat flux is due to the distinct nature of high porosity and multiscale pore sizes of copper foams.

► Copper foam was newly used as the wick structure of vapor chambers.
► The surface temperature non-uniformity of vapor chambers was newly defined.
► Effects of working fluids, charge ratios and inclination angles were studied.
► The high heat flux of ∼220 W/cm2 is reached.
► High porosity and multiscale pore sizes of metallic foams dissipate high heat flux.