Nucleate pool-boiling of R-114 refrigerant and oil mixtures from water-heated enhanced surfaces
McManus, Stephen M.
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Heat- transfer measurements were made for a single, water-heated tube in a pool of R-114 to simulate operating conditions of a water chiller. Data were obtained for a smooth copper tube, and for two commercially available tubes: a spirally roped copper-nickel tube with a porous coating; and a copper tube with a structured outer surface and a multiple-start helical ridged inner surface. Measurements were made for refrigerant-oil mixtures at oil concentrations from 0 to 6 mass percent with a boiling pool temperature of 13.8 ˚C. Results for the two enhanced tubes with and without oil are compared to the smooth tube data. Enhancement factors for the overall heat- transfer coefficient were 4.0 and 3.6 for the structured surface and porous-coated tubes, respectively, in pure refrigerant and at a water Velocity of 2 m/s. For these same conditions the enhancement factors for the outside heat- transfer coefficient were 14.6 and 6.4 for the porous-coated and structured surface tubes, respectively.
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