Microporous Coatings to Maximize Pool Boiling Heat Transfer of Saturated R 123 and Water

Abstract

The present research is an experimental study for the enhancement of boiling heat transfer using microporous coatings. Two types of coatings are investigated: one that is bonded using epoxy and the other by soldering. Effects on pool boiling performance were investigated, of different metal particle sizes of the epoxybased coating, on R123 refrigerants, and on water. All boiling tests were performed with 1 cm أ— 1 cm test heaters in the horizontal, upwardfacing orientation in saturated conditions at atmospheric pressure and under increasing heat flux. The surface enhanced by the epoxybased microporous coatings significantly augmented both nucleate boiling heat transfer coefficients and critical heat flux (CHF) of R123 relative to those of a plain surface. However, for water, with the same microporous coating, boiling performance did not improve as much, and thermal resistance of the epoxy component limited the maximum heat flux that could be applied. Therefore, for water, to seek improved performance, the solderbased microporous coating was applied. This thermally conductive microporous coating, TCMC, greatly enhanced the boiling performance of water relative to the plain surface, increasing the heat transfer coefficient up to ∼5.6 times, and doubling the CHF.