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 u sing vertical and horizontal orientations. The effects of nonboiling w aiting period, pressure and spine dimensions on boiling behavior were examined. A marked enhancement of heat transfer performance was observ ed on passing from plane to extended surfaces. Increasing the pressure improved the heat transfer coefficient and critical heat flux. The no nboiling period, orientation and pressure significantly influenced the boiling incipience and the hysteresis phenomenon that accompanies inc reasing and decreasing heat fluxes. Experimental data are expressed in terms of enhancement ratios of extended surfaces as a function of bas e surface superheat and pressure.