3321 (RP-469) -- Performance Predictions of Refrigerant-Oil Mixtures in Smooth and Internally Finned Tubes - Part 2: Design Equations PDF

Equations to predict the heat transfer and pressure drop performance of refrigerant-oil mixtures in smooth and augmented tubes are presented. These equations are based on data obtained during an experimental test program. Testing was carried out in a smooth tube, a micro-fin tube, and a low-fin tube, each having an outside diameter of 0.375 in. (9.52mm). Various concentrations up to 5% by weight of 150- and 300-SUS naphthenic mineral oil were tested, and mass flux was varied from 92,000 to 294,000 lb/h.sq.ft. (125 to 400 Kg/sq.mt.s). Nominal evaporation conditions were 37 deg F (3 deg C) with inlet and outlet qualities of 15% and 85%, respectively. Past correlations, both for pure refrigerants and refrigerant-oil mixtures, were investigated to determine if they could adequately predict the current data in some cases, agreement between current data and earlier correlations is quite good, while in other cases, there is poor agreement. Statistical equations also were developed based on average system parameters, such as oil concentration or mass flux, which do not require the determination of fluid properties.

KEYWORDS: performance, calculating, refrigerants, oils, mixtures, tubes, finned tubes, heat flow, heat transfer fluids, designing, pressure drop, testing, R12, R22, statistics, lubricants.