4503 -- A Numerical Study of Pressure Distribution and Flow through Rigid Short-Tube Orifices

A finite element model was used to estimate the pressure distribution inside a short-tube orifice and mass flow for single-phase flow of R-22 and R-134a. The results for the numerical model were compared to published experimental data. The study included three different length-to-diameter (L/D) ratios and upstream pressures ranging from 1.45 to 1.72 MPa for R-22 and from 0.9 to 1.17 MPa for R-134a. Downstream pressures ranged from 1 to 1.36 MPa for R-22 and from 0.6 to 0.86 MPa for R-134a. A constant subcooling of 13.9ºC was used for all cases.

Pressure distribution results from the numerical model showed close agreement with the experimental data for R-22. Moreover, with R-134a, the model tended to overpredict the pressure recovery after the vena-contracta when the down-stream pressure was very close to the saturation pressure. The numerical model captured the expected sharp drop in pressure at the tube inlet. For mass flow, the model was within 7% of the published experimental data for both R-22 and R-134a.

Units: SI