Enhancement of R123 pool boiling by the addition of hydrocarbons

This paper presents pool boiling heat transfer data for 10 different R123/h ydrocarbon mixtures. The data consisted of pool bailing performance of a GE WA-T(R) surface for pure R123 and for 10 dilute solutions of five different hydrocarbons: (1) pentane, (2) isopentane, (3) hexane, (4) cyclohexane, an d (5) heptane with R123. The heat flux and the wall superheat were measured for each fluid at 277.6 K. A maximum (19 +/- 3.5)% increase over the pure R123 heat flux was achieved with the addition of 0.5% mass isopentane to R1 23. Other mixtures of isopentane, pentane, hexane, and cyclohexane with R12 3 exhibited smaller maximums than that of the R123/isopentane (99.5/0.5) mi xture. Presumably, a layer enriched in hydrocarbon at the heat transfer sur face caused the heat transfer enhancement. Conversely, an R123/heptane (99. 5/0.5) mixture and an R123/cylcohexane (99.5/0.5) mixture exhibited only de gradations with respect to the pure component performance for all test cond itions. Several characteristics of the hydrocarbons were examined to determ ine their influence on the boiling heat transfer performance: molecular wei ght, molecular structure, composition, surface tension, and vapor pressure. (C) 2000 Elsevier Science Ltd and IIR. All rights reserved.