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 andR-134a presents nearly 30% lower mass flow rates. These results are connected with the different saturation pressure curves for each fluid
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