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Title:Predicting the Air-Side Thermal -Hydraulic Performance Characteristics of Flat-Tube Louver-Fin Heat Exchangers Under Dry and Wet Conditions
Author(s):Park, Young-Gil
Doctoral Committee Chair(s):Jacobi, Anthony M.
Department / Program:Mechanical Engineering
Discipline:Mechanical Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Engineering, Mechanical
Abstract:A simple area-partitioning method for analyzing the wind-tunnel data is developed for flat-tube heat exchangers under partially wet conditions, and new air-side performance correlations are presented for both dry- and wet-surface conditions. Correlations between the Colbum j or f factors and the Reynolds numbers are developed in the conventional way and compared to multivariate non-parametric regressions. The conventional correlations significantly extend prior work by expanding the parameter space and establishing a physical basis for the form of the fits. However, it is found that multivariate non-parametric regressions can dramatically reduce the RMS errors if a large, well-structured dataset is used. Furthermore, this method provides statistical indicators that can be used to prevent over-fitting when the dataset is limited. Important condensate retention and drainage mechanisms are identified and modeled using analytical and numerical methods. When condensate obstructs the louver gap, boundary layer re-starting does not occur, and the most important heat transfer enhancement mechanism in these flows lost. It is shown that surface tension can maintain inter-louver condensate bridges against gravity and flow-generated shear and pressure forces, even at air-side Reynolds numbers much higher than are typical to the applications of interest. Thus, maintaining wet-surface heat transfer performance depends on avoiding the initial formation of inter-louver bridges.
Issue Date:2007
Description:191 p.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2007.
Other Identifier(s):(MiAaPQ)AAI3270001
Date Available in IDEALS:2015-09-25
Date Deposited:2007

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