Enhancement of R123 pool boiling by the addition of N-hexane

This paper presents the heat transfer data used to file international paten t WO 94/18282. The data consisted of pool boiling performance of a GEWA-T(T M) surface for three fluids: (1) pure R123, (2) R123/n-hexane (99/1), and ( 3) R123/n-hexane (98/2). The heat flux and the wall superheat were measured for each fluid at 277.6 K. A (47 +/- 7)% increase over the pure R123 heat flux was achieved with the addition of 1% mass hexane to R123. Similarly, t he R123/hexane (98/2) mixture gave a maximum percent heat flux enhancement over pure R123 of (29 +/- 7)%. The boiling was filmed with a 16 mm highspee d camera. The observations were used to describe various boiling modes on t he GEWA-T(TM) surface. The addition of hexane to pure R123 caused a simulta neous reduction in the bubble diameter and increase in the site density. Th e increase in site density enhanced the boiling despite the reduction in bu bble size. Presumably, the site density enhancement was caused by a layer e nriched in hexane at the heat transfer surface.