Mass flow rate of R-410A through short tubes working near the critical point

Experimental data were taken to examine R-410A mass flow rate characteristics through short tube restrictors at upstream pressures approaching the critical point. Four short tube restrictors were tested by varying upstream pressure from 2619 to 4551 kPa (corresponding to saturation temperature from 43.9 to 71.7 °C), upstream subcooling from 2.8 to 11.1 °C and downstream pressure from 772 to 1274 kPa. The experimental data were represented as a function of major operating parameters and short tube diameter. As compared to mass flow trends at typical upstream pressures, flow dependency on upstream subcooling was more significant at high upstream pressures due to a higher density change. Based on the database obtained from this study and literature, an empirical correlation was developed from a power law form of dimensionless parameters generated by the Buckingham Pi theorem. The post-predictions of the new correlation yielded average and mean deviations of 0.11 and 2.4%, respectively.