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Title:Air-side condensate management: Drainage channels in heat exchangers
Author(s):Gupta, Deep
Advisor(s):Jacobi, Anthony M.
Department / Program:Mechanical Sci & Engineering
Discipline:Mechanical Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Abstract:Condensate on the air-side surface of flat-tube air-cooling heat exchangers can result in several adverse effects on the overall thermal-hydraulic performance. In order to improve the performance of compact heat exchangers under wet-surface conditions, promoting the drainage of condensed water is critical. Drainage channels on tube walls might provide a robust solution to promote condensate drainage from compact heat exchangers. A quantitative and qualitative evaluation of the effectiveness of drainage channels on the condensate retention characteristics of compact flat-tube louver-fin heat exchangers is presented. Various geometries of drainage channels are engraved on surrogate tubes in contact with fin stock. Two fin designs are tested using a dynamic dip testing method, and four designs are tested in a small wind tunnel apparatus. Data from the quantitative results and the visualization tests show that the drainage channels reduce the condensate retention for all the fin designs tested, except one. Fin structure plays an important role in determining the condensate retention behavior and hence the effect of drainage channels. Other important parameters, such as fin gap and louver gap, which have an effect on the condensate retention behavior are identified. The results include a comparison of drainage channel geometry and dimensions, over a range of incoming air velocity and relative humidity, and at different sample inclinations. The maximum effect obtained is a 27% reduction in steady- state retention. A method to implement drainage channels in full-size heat exchangers is suggested and an analysis suggests heat transfer can be improved by 12% while pressure drop is reduced by 9%.
Issue Date:2010-08-31
Rights Information:Copyright 2010 Gupta Deep
Date Available in IDEALS:2010-08-31
Date Deposited:2010-08

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