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Journal of Enhanced Heat Transfer

Theory and Application in High Performance Heat and Mass Transfer

ISSN for PRINT: 1065-5131

Institutional price:	$577.00
Issues per year:	4

Best Paper Award Selection - Editorial Board Site

2005, Volume12

104 pages

DOI: 10.1615/JEnhHeatTransf.v12.i4

Issue price - $138.00

Numerical Prediction of the Performances of the Fins with Punched Delta Winglets and the Louver Fins and Their Comparison

Jingchun Min
The Key Lab of Education Ministry for Enhanced Heat Transfer and Energy Conversion, Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China

Wei Xu
The Key Lab of Education Ministry for Enhanced Heat Transfer and Energy Conversion, Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China

ABSTRACT

Performances of the plain fin, the fins with punched delta winglets, and the louver fin used in a flat-tube heat exchanger application were numerically predicted and compared, with the plain fin serving as the baseline fin. Calculations were made in three dimensions and account for conduction within the fin for two frontal air velocities of 1.0 and 4.0 m/s, yielding fin-pitch-based Reynolds numbers of 210 and 840. The time-dependent laminar flow model was adopted in the calculations. As compared to the plain fin, the louver fin enhances heat transfer by 114.1−139.1% while the fin with three winglet rows enhances heat transfer by 46.5−76.1%, indicating that the enhancement level of the louver fin is considerably higher than that of the fin with winglets. The j to f factor ratio of the louver fin is smaller than that of the fin with three winglet rows, but the j to f^1/3 ratio of the former is greater than that of the latter, so the louver fin is superior to the fin with winglets, if the ratio j/f^1/3 is used as the performance evaluation criterion. The spanwise averaged heat-transfer coefficient of the louver fin varies significantly along the streamwise direction, sharp peaks appear over the fin region, each peak corresponds to each of the leading edges of the louvers, while the minima occur at the slits between two consecutive louvers. The spanwise averaged heat-transfer coefficient of the fin with winglets exhibits a more gentle variation along the streamwise direction, it increases at winglets and decays over the winglet-free regions.