Boiling of R290+CF3i mixture inside an offset strip fin plate heat exchanger

Abstract

In this study, evaporation characteristics of mildly flammable R290 + CF3i mixture (35 % + 65 % by weight) were conducted experimentally in an offset strip fins (OSSF) embedded plate heat exchanger (PHEX). Various operating conditions, namely, saturation temperature (Tsat), heat flux (q), inlet vapor quality (xin), and mass flux (G), were considered in the range of 5–15 °C, 4–10 kW m−2, 0.1–0.8, and 40–80 kg m−2 s−1, respectively. From this study, it was found that nucleate boiling was quenched at lower xin regardless of the operating conditions, although the boiling process was led by convection at high xin. Except at higher G, there was a presence of dry-out at a mean x ranging between 0.36 and 0.50, while the two-phase frictional pressure drop increased steadily with mean x. The heat transfer coefficient was largely augmented with increments in G of 50.15 %, followed by increments in q and T of 15.1 % and 12.3 %, respectively. Similarly, the two-phase frictional pressure drop was increased by 12.3 % and 175.4 % with increases in q and G, respectively, although it diminished by 21.9 % with Tsat. Compared to R1234yf, the mean HTC of R290 + CF3i was 6 % lower with 7 % increased TP-FPD. Additionally, Nusselt number and friction factor correlations have been developed with excellent predictability of 7 % and 12 % of mean absolute error, respectively.