Flow mechanisms of HFC-410A inside short-tube orifices during flashing process

New experimental data of HFC-410A flow mechanisms, including pressure and temperature distributions, flow pattern, and mass flow rate inside a short-tube orifice are studied. Different short-tube orifice lengths of 10 mm, 15 mm, and 20 mm, with short-tube orifice diameters ranging from 0.849 to 1.096 mm were manufactured for this experiment. The test runs are done at upstream pressures ranging from 2100 to 2600 kPa, and with a degree of subcooling between 4 and 12 °C. The results show that the refrigerant flow mechanisms in the entrance region and inside a short-tube orifice agree with incompressible flow theory, but the refrigerant flow mechanisms in the exit region are similar to choked flow in a theoretical compressible flow. The temperature distribution inside a short-tube orifice is directly related to the pressure distribution. The mass flow rate is directly proportional to the upstream pressure and degree of subcooling, whereas it is strongly affected by the short-tube diameter. The downstream pressure has insignificant effects on the mass flow rate and pressure distribution inside a short-tube orifice. However, the downstream pressure has a slight effect on the temperature distribution inside a short-tube orifice.