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International Heat Transfer Conference 7

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

AUGMENTATION OF CONDENSATION HEAT TRANSFER BY INTERNALLY FINNED TUBES AND TWISTED TAPE INSERTS

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

S. A. Said
Department of Mechanical Engineering Kansas State University, Manhattan, KS 66506 USA

DOI: 10.1615/IHTC7.340
pages 33-38

Abstract

Heat transfer and pressure drop data were taken during condensation of R-113 inside seven horizontal tubes. One tube was smooth, four were internally finned with different outside diameters and fin geometries, and the remaining two had twisted tape inserts with different pitch to diameter ratios. The smooth tube results were used to identify, among existing smooth tube correlations, the best predictors of the experimental measurements of this investigation. For each of the augmentation techniques tested, new appropriate modifiers were identified and applied to the smooth tube correlations to bring about the best agreement between the measurements of the augmented tubes and predictions. Over the mass flux range tested, the best performing internally finned tube enhanced the heat transfer coefficients by 51% above the smooth tube, on a nominal area basis. The twisted tape inserts enhanced the heat transfer coefficients by as much as 23% over the smooth tube, on a nominal area basis. Correlations were proposed for predicting the overall average heat transfer coefficients and pressure drop for the two augmentation techniques tested.

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