Foam Flow of Oil-Refrigerant R134A Mixture in a Small Diameter Tube (original) (raw)

This paper presents a numerical study on the performance of capillary tubes with R-22 and some alternatives considered for R-22 replacement, namely R-407C, R-410A and R-134a. It is compared the mass flow rate as function of inlet conditions (condensing temperature, subcooling degree or inlet quality) for a given geometry. Numerical results show that, taking R-22 as the reference, R-407C mass flow rates are slightly higher (about 5%), R-410A presents about 30% higher mass flow rates and R-134a presents nearly 30% lower mass flow rates. These results are connected with the different saturation pressure curves for each fluid NOMENCLATURE A Area X quality c sound speed y molar fraction Cc contraction coefficient z position d diameter a void fraction f Darci friction factor creJ relative rouglmess G mass flux a area ratio h specific enthalpy subscripts he convection heat transfer coefficient cd condenser, condensation k liquid conductivity ct capillary tube m mass flow rate ev evaporator...