Pressure Drop of Two-Phase Refrigerant-Oil Mixtures in a Small Channel

摘要

The adiabatic pressure drop of two-phase flow of refrigerant-oil mixtures in a small rectangular channel (d_h=148.0 microns) has been investigated. Tests have been performed with R134a with varying concentrations of a POE 32 oil. Pressure drop tests of pure refrigerant in these size channels have found reasonable agreement to the homogeneous pressure drop models, although flow visualization studies show that such flows are not always in regimes that can be considered homogeneous. The fluid properties of the liquid phase (density, viscosity, etc.) are difficult to characterize because they are governed by the amount of refrigerant that remains dissolved in the oil. Fluid property data measured for this refrigerant-oil pair is used to determine the actual properties of the liquid phase. A separated flow model that was developed from pressure drop of four different pure refrigerants to account for the varying fluid properties (Field and Hrnjak 2006) was compared to the data with the actual liquid phase properties, showing moderate success especially in the high quality region.