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

Abstract

This paper 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 100-500 kg m-2 s-1 at three different saturation conditions (40, 50 and 50 °C). The resulting data was compared with the nonequilibrium condensation models of Agarwal & Hrnjak (2014), Kondou & Hrnjak (2012) and Xiao & Hrnjak (2017), as well as the equilibrium model of Cavallini et al. (2006) with the Gnielinski (1976) correlation for predictions in subcooled and saturated regions. The additional mass transfer effects were accounted for by applying the Silver (1947), Bell & Ghaly (1973) mixture correction. The non-equilibrium Kondou & Hrnjak (2012) model, with the predictions in the subcooled region from Gnielinski (1976) 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.

Performances Investigation of the Eco-friendly Refrigerant R13I1 used as Working Fluid in the Ejector-Expansion Refrigeration Cycle

“…Furthermore, although R744 fluid is ecofriendly, it undergoes high running pressure and relatively low performance, which results in a ponderous and expensive refrigeration machine. In addition, the zeotropic blends exhibit various problems in the cooling cycles (CMVCRC, EERC) due to their behavior compared to the single-fluids such as mole fraction difference of the vapor to liquid and temperature variation during constant pressure phase change, they present also a low coefficient of performance [20][21][22]3], this can be induced by the delay of the liquid-vapor equilibria such as overheating or undercooling, which results from the temperature change during the cooling process (temperature glides) [20]. The dilemma for the refrigeration industry is finding a new working fluid in the EERC system that can meet the requirements of environmental properties, safety and high performance at the same time.…”