The effect of a boiling additive on R123 condensation on a vertical integral-fin surface

This payer examines the effect of the addition of 0.5% mass isopentane to R 123 on the vapor-space condensation heat transfer of R123. In a previous st udy, the pool boiling performance of R123 was improved by adding 0.5% mass isopentane. Consequently, the impetus of the present study was a desire to quantify the consequence of the boiling additive on the condensation heat t ransfer performance of pure R123. In this way, the net effect of the additi ve on the cycle performance of pure R123 can be estimated. The data consist ed of the heat flux and the wall temperature difference measurements for pu rr R123 and R123/isopentane (99.5/0.5) on an integral-trapezoidal-fin surfa ce. The temperature of the saturated vapor was held constant at 313.15 K fo r all of the tests. On average, the R123/isopentane mixture exhibited a 4% smaller heat flux than that of pure R123. Presumably, the degradation was c aused by the zeotropic behavior of the mixture, which led to a loss of avai lable driving temperature difference for heat transfer across the liquid fi lm. Considering that the boiling performance was enhanced on average by 10% with the addition of 0.5% mass isopentane, isopentane may still be a viabl e means of improving the cycle performance of R123 despite the 4% condensat ion heat transfer degradation. (C) 2000 Elsevier Science Ltd and IIR. All r ights reserved.