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Measurements were made on short tube orifices with L/D more than 5 but less than 20 for Refrigerant-22 in a 3/8" (9.53mm) refrigerant line. Data were collected for upstream pressures ranging from 210 to 291 psia (1,448 to 2,006 kPa) and for qualities as high as 10% and subcoolings as high as 25 deg F (13.9 deg C). A mass flow model and flow charts were developed by empirically correcting the modified single-phase orifice equation to satisfy the short-tube orifice flow. The data and conditions extend beyond the range of and are presented in a format similar to a study by Aaron and Domanski (1990). For normal heat pump operating conditions, the mass flow rate was dependent on upstream pressure and upstream subcooling, but it was insensitive to downstream pressure due to approximate choking. As found in previous investigations, the mass flow rate also dependent on cross-sectional area, chamfer depth, and short-tube length. For two-phase flow entering the short tube, the flow rate decreased with increasing quality.

KEYWORDS: refrigerants, R22, orifices, measuring, tubes, pressure, heat pumps, fluid flow, flow rate, subcooling

Citation: ASHRAE Trans. 1994, Vol.100, Part 1, Paper number 3768, 323-334, 12 figs., 1 tab., refs.