In-Tube condensation of zeotropic refrigerant R454C from superheated vapor to subcooled liquid

Abstract

This article investigates the in-tube, superheated, saturated, and subcooled condensation of zeotropic refrigerant mixture R454C. R454C is proposed to replace R404A for commercial refrigeration applications. Quasi-local heat transfer coefficients were measured in a 4.7 mm horizontal tube at mass fluxes ranging from 100 to 500 kg m−2 s−1 at three different saturation conditions (40, 50, and 50 °C). The resulting data was compared with the non-equilibrium condensation models of Agarwal and Hrnjak, Kondou and Hrnjak, and Xiao and Hrnjak, as well as the equilibrium model of Cavallini et al. with the Gnielinski correlation for predictions in subcooled and superheated regions. The additional mass transfer effects were accounted for by applying the Silver, Bell and Ghaly mixture correction. The non-equilibrium Kondou and Hrnjak model, with the predictions in the subcooled region from Gnielinski correlation, agrees best with the data (mean average percent error = 9%). An air-cooled condenser for a 1055 kW refrigeration system is designed by following both the non-equilibrium and equilibrium approaches. This non-equilibrium approach leads to a 4.8 and 9.1% reduction in heat transfer area for R454C and R404A, respectively. R454C condenser area is 17–21% larger than that of a R404A condenser.