CH-93-14-3 -- Pool Boiling of R-11 and R-123 Oil-Refrigerant Mixtures on Plain and Enhanced Tube Geometries PDF

Describes work to determine the effects of various concentrations of compressor oil on the heat transfer coefficients of refrigerants boiling on enhanced tube geometries. Data are presented for pool boiling of refrigerant-oil mixtures on a horizontal plain tube and two enhanced tube geometries using R11 and R123 at 40 deg F (4.4 deg C). The data were taken for oil concentrations of 0.05%, 1%, 2%, and 5% at 40 deg F refrigerant temperature. The data show that increased oil content reduces the boiling coefficient for all geometries. The results also show that a smaller performance degradation occurs for R123 than for R11. Further, oil degrades the boiling performance of enhanced tubes more than for plain tubes for both refrigerants. At 2% oil, the performance degradation for the enhanced tubes is approximately 10% for R123 and 20% for R11.

KEYWORDS: boiling, refrigerants, mixtures, R11, R123, lubricants, compressors, evaporators, heat flow, heat transfer coefficient, vapour compression heat pumps, heat pumps, geometry, performance, refrigeration, tubes, deteriorating.