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Research Papers: Heat Exchangers

# Air-Side Heat Transfer and Friction Correlations for Flat-Tube Louver-Fin Heat Exchangers

[+] Author and Article Information
Young-Gil Park1

Department of Mechanical Science and Engineering, University of Illinois, 1206 West Green Street, Urbana, IL 61801ypark5@uiuc.edu

Anthony M. Jacobi

Department of Mechanical Science and Engineering, University of Illinois, 1206 West Green Street, Urbana, IL 61801a-jacobi@uiuc.edu

We believe that these six sets of data are simply plotted with a scaling error in the Reynolds number; all the corresponding data appear to have a significant shift (27%) in Reynolds number.

The digitizing uncertainty is based on a partial set of the data plotted with reasonable image quality. The increase of overall data uncertainty due to this process is insignificant.

An empirically based model may yield an unreasonable fit if too many parameters are included when fitting from a limited database. Overfitted models typically show poor validation with new data.

1

Corresponding author.

J. Heat Transfer 131(2), 021801 (Dec 11, 2008) (12 pages) doi:10.1115/1.3000609 History: Received November 12, 2007; Revised September 15, 2008; Published December 11, 2008

## Abstract

The objective of this study is to develop an accurate, reliable, and updated predictive model for the air-side performance of flat-tube louver-fin heat exchangers. Using the most comprehensive experimental database to date—consisting of 1030 heat-transfer and 1270 pressure-drop measurements, from nine independent laboratories for 126 sample heat exchangers—$j$- and $f$-factor correlations are developed to predict the air-side performance of heat exchangers. The database is analyzed, the form of the curve fits is explored, and the predictive performance of the correlations is evaluated. The $j$- and $f$-factor correlations predict the experimental data with rms errors of 11.5% and 16.1%, respectively. Multiple regressions for a locally linearized data model were used to estimate the confidence intervals and covariances of the regression constants. A comparison to prior correlations shows the proposed correlations to provide more accurate predictions and to span a much broader parameter space than prior work. Practical utility in design and optimization, and unavoidable limitations in developing such correlations are discussed.

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## Figures

Figure 3

Comparison of the present f-factor correlation and the experimental data

Figure 4

Comparison of two similar heat exchangers (Chang and Wang (6) Source 10 and Webb and Jung (13) Source 2). The uncertainty of f-factor by Chang and Wang was 2–7% and unknown for data by Webb and Jung—it is unlikely that the discrepancy of f-factor is solely due to the experimental uncertainty.

Figure 1

Schematic of a flat-tube louver-fin heat exchanger: (a) close-up frontal view; (b) cross-sectional view of louver fin

Figure 2

Comparison of the present j-factor correlation and the experimental data (J, Jacobi (11); KB, Kim and Bullard (4), D, Davenport (2); CW, Chang and Wang (6); AC, Achaichia and Cowell (1); WJ, Webb and Jung (13); R, Rugh (7); SS, Sunden and Svantesson (5); KYL, Kim (12))

## Errata

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