Experiments on pool boiling of a dielectric fluid on extended surfaces

An experimental study on pool boiling heat transfer from finned copper surfaces immersed in a saturated dielectric liquid (Galden HT-55) is presented. Two extended surfaces of different dimensions were tested using vertical and horizontal orientations. The effects of nonboiling waiting period, pressure and spine dimensions on boiling behavior were examined. A marked enhancement of heat transfer performance was observed on passing from plane to extended surfaces. Increasing the pressure improved the heat transfer coefficient and critical heat flux. The nonboiling period, orientation and pressure significantly influenced the boiling incipience and the hysteresis phenomenon that accompanies increasing and decreasing heat fluxes. Experimental data are expressed in terms of enhancement ratios of extended surfaces as a function of base surface superheat and pressure.