Boiling of enhanced surfaces at high heat fluxes in a small boiler

High operating heat fluxes and small boiling space are the two major challenges to apply boiling heat transfer in electronics cooling. This experimental study seeks to find a good boiling performance surface that is suitable for cooling a CPU dissipating up to 88 W through a 14 mm x 14 mm surface area in a 15 mm x 54mm x 54mm vessel. Three structured boiling surfaces and three porous surfaces were tested in water at 60 degrees C pool temperature. The experimental data showed that the best cross-grooved surface and the best porous surface have similar boiling performance curves. The evaporation resistances of these two surfaces vary from 0.12 to 0.26 K/W. The minimum evaporation resistance of the best cross-grooved surface was 0.125 K/W at 86.5 W. Because the evaporator area is much smaller than the condenser or the heat sink area, the thermal resistance is dominated by the evaporator. The condensation resistance of the 54mm x 54mm condensing area varies from 0.01 to 0.022 K/W, which is much smaller than the evaporation resistance of every boiling surface in the present test.