Effect of space distance for boiling heat transfer on micro porous coated surface in confined space

This work provides an experimental analysis of the boiling heat transfer of methanol on plain and micro porous coated surfaces inside confined space. Three space confinements with distance of 1.0, 2.0, 3.0 mm and an unconfined space were tested on plain and micro porous coating surfaces. Effects of space confinement, surface treatment and heat flux on the heat transfer coefficient and critical heat flux were discussed. From the test results, we may deduct that the boiling heat transfer performance in confined spaces was affected by four major effects, i.e. (a) vapor blowing and liquid suction effect, (b) thin film evaporation, (c) vapor leaving resistance and (d) partial dryout effect on plain surface. But only (a) and (c) are important on micro porous coating surface. The combination of these effects resulted in the micro porous to plain surfaces heat transfer enhancement ratio to have different characteristics at low, moderate and high heat flux conditions. Micro porous coating is a very effective boiling heat transfer enhancement treatment at low and moderate heat fluxes conditions. The enhancement ratio reduced in very narrow space confinement or at very high heat flux condition.