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International Heat Transfer Conference 9

ISSN: 2377-424X (online)
ISSN: 2377-4371 (flashdrive)

CONDENSATION HEAT TRANSFER AND PRESSURE DROP OF OIL-REFRIGERANT MIXTURES INSIDE SMOOTH AND INTERNALLY FINNED TUBES

B. Sur
Department of Mechanical Engineering Kansas State University, Manhattan, KS 66506, USA

N. Z. Azer
Department of Mechanical Engineering Kansas State University, Manhattan, KS 66506, USA

DOI: 10.1615/IHTC9.1020
pages 33-38

Abstract

Heat transfer and pressure drop data were taken during condensation of Refrigerant-113 and 150-SUS naphthanic mineral oil mixtures inside smooth and internally finned tubes. Mixtures with oil concentrations of 1.2 %, 2.8 % and 4.0 % by weight, in addition to pure refrigerants, were tested. The data were collected from three sets of tube-in-tube, counter flow test condensers where test fluid condensed inside the inner tube and the cooling water flowed in the annulus. Each set had two condensers. Within each set, the inner tube of one of the condensers had internal fins on the inside while the other had a smooth surface. Both tubes had the same outside diameter. The inner tubes of the three sets differed in the outside diameters and the geometric parameters of the fins.
The presence of oil resulted in a reduction in the heat transfer coefficient for both smooth and internally finned tubes. These reductions were approximately 7%, 12% and 16% for oil concentrations of 1.2%, 2.8% and 4.0%, respectively, for both smooth and internally finned tubes. The heat transfer for both oil-free and refrigerant-oil mixtures were enhanced by internal fins. This enhancement was in the range of 25-85%. Internal fins increased the pressure drop of both oil-free and refrigerant-oil mixtures in the range of 75-480% over the smooth tube results. However, the presence of oil had little effect on pressure drop for all the tubes tested.

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