An experimental investigation of two-phase flow of mixtures of Refrigerant 134a with 168 SUS polyalkylene glycol (PAG) oil through short tube orifices was performed for oil concentrations ranging from 0 to 5.1%. Both two-phase and subcooled liquid flow entering short tubes were studied for an upstream pressure of 1172 kPa, for subcoolings as high as 13.9 C, and for qualities as high as 8% at the inlet of the short tube. Downstream pressures were varied from saturation pressure, Psat,to 310 kPa. The effects of the lubricant on the flow characteristics were discussed as a function of downstream pressure, upstream subcooling/quality and upstream pressure. The effects of oil concentration on mass flow through short tubes varied as a function of upstream subcooling or quality. The maximum reduction in flow occurred at zero subcooling, where the flow was reduced by approximately 12.1% for a 5.1% oil concentration. For entering subcooling above 8.3 C and at a quality of 5%. there were small increases in flow for the addition of oil to the refrigerant. The observed flow trends were analyzed using pressure profile measurements and visualization tests.
ASJC Scopus subject areas
- Condensed Matter Physics
- Mechanical Engineering
- Fluid Flow and Transfer Processes