Condensation of Rl34a flowing inside helicoidal pipe

摘要

Condensing heat transfer and pressure drop characteristics of an ozone-friendly refrigerant HFC-l34a (hydrofluorocarbon l34a) flowing inside a l2.7 mm helicoidal tube were investigated experimentally to obtain heat transfer data and correlations. For long helicoidal pipe, heat transfer measurements were performed for the refrigerant flow mass fluxes from l00 to 400 kg/m~2/s, in the cooling water flow Reynolds number range of l500 ＜ Rew ＜ 9000 at fixed system temperature (33deg.C) and cooling tube wall temperature (l2deg.C and 22deg.C). With the increase of mass flux, the overall condensing heat transfer coefficients of Rl34a increased, and slowly the pressure drops also increased. However, with the increase of mass flux (or the cooling water flow Reynolds number), the refrigerant side heat transfer coefficients decreased. The effects of cooling wall temperature on heat transfer coefficients and system pressure drops were considered. Predictive correlations valid over the above water flow Reynolds number ranges and refrigerant flow mass flux were proposed. Helicoidal pipe heat transfer characteristics were compared with data for horizontal straight pipe from literature reports.