Pool Boiling Heat Transfer of Borated (H3BO3) Water on a Nanoporous Surface

Abstract

With regard to potential application in pressurized water reactors (PWRs), a nanoporous heated surface was tested in pool boiling of an aqueous solution of boric acid (H3BO3), or borated water (1% volume concentration). The effect of system pressure and surface orientation on pool boiling heat transfer (BHT) was studied. The nanoporous surface consisted of a coating of alumina nanoparticles applied on a 1 cm2 flat copper surface through nanofluid boiling. An uncoated surface in borated water was similarly tested, and due to boric acid deposition, the BHT degraded and the critical heat flux (CHF) enhanced relative to pure water. Also, the possibility of transient pool boiling behavior of borated water was investigated but none was detected. With pressure and orientation variation, the nanoporous surface imposed on borated water showed a trend of further CHF enhancement to the CHF limit produced by the nanoporous surface in pure water. Over the nanoporous surface, the CHF of borated water was increasingly better with decreasing pressure, than that over the plain surface. However, BHT degraded slightly further. Boric acid deposition over the nanoporous surface was believed to be the source of this BHT degradation, but played no apparent role in the further CHF enhancement.