Spray cooling of plain and copper-foam enhanced surfaces

This paper deals with the experimental evaluation of spray cooling of a horizontal upward-facing 25-mm diameter heater onto which a 5-mm high copper foam disk of same diameter was brazed. The copper foam had a porosity of 90% and a pore density of 10 PPI (pores per inch). A commercially available single-orifice pressure swirl atomizer was used to produce a spray with mass flow rates of 3.0 and 5.0 kg/h for system (saturation) pressures of 500 and 600 kPa. R-134a was the working fluid. An inlet sub-cooling degree of 5 °C was used in all tests. Data are presented in the form of boiling curves and as plots of heat transfer coefficient as a function of the heat flux. Results are compared with those obtained with a plain surface and enhancement factors as high as 1.39 (for a 22 W/cm2 heat flux) were observed. A critical heat flux of 30 W/cm2 was achieved for the 3.0 kg/h mass flow rate for both plain and metal foam surfaces.

► Experimental analysis of spray cooling of upward-facing plain and copper-foam surfaces.
► Copper-foam element of 90% porosity and pore density of 10 PPI.
► Test conditions are typical of vapor compression refrigeration systems using R-134a.
► Enhancement factors are high as 1.39 obtained for the copper-foam surface.
► Critical heat flux of 30 W/cm2 was achieved for both plain and copper-foam surfaces at 3.0 kg/h.