Forced convection steam condensation experiments within thin porous coatings

Abstract

This paper reports the experimental findings of forced convective condensation heat transfer on plates with a thin porous coating. The composite system consists of a relatively thin, highly conductive and permeable porous coating bonded to a cold isothermal condensing surface which is placed parallel to saturated steam flow. The porous coatings ranged in thickness from 0 to 254 μm and are used as a passive technique for heat transfer augmentation. The inclined and isothermal plates were exposed to bulk vapor velocities of 0.9–6.5 m s −1 resulting in free-steam Reynolds numbers of 5.0 × 10 4-2.7× 10 6. The forced convective heat transfer coefficients show a substantial heat transfer enhancement (250% increase) when compared to noncoated surface under the prescribed conditions. The experimental data exhibits as much as a 600% increase over previously measured free convection condensation results. The effect of subcooling temperature and plate inclination (vertical to horizontal) is also documented. The results of this study provide valuable fundamental predictions of condensation heat transfer that can be used in a number of thermal engineering applications which require heat transfer enhancement or retardation of an impermeable surface.