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Journal of Enhanced Heat Transfer

Impact factor: 0.605

ISSN Print: 1065-5131
ISSN Online: 1563-5074

Journal of Enhanced Heat Transfer

DOI: 10.1615/JEnhHeatTransf.v11.i1.50
pages 61-74

Numerical Analyses of Effects of Tube Shape on Performance of a Finned Tube Heat Exchanger

Jungchin Min
The Key Lab of Education Ministry for Enhanced Heat Transfer and Energy Conversion, Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China
Ralph L. Webb
Department of Mechanical Engineering The Pennsylvania State University, University Park, PA 16802, USA
Specialist in enhanced heat transfer and heat exchanger design

ABSTRACT

This article discusses the effects of tube geometry on the performance of a multi-row finned tube heat exchanger having herringbone wavy fins. The air-side heat transfer and pressure drop characteristics of the heat exchanger were predicted numerically and the tube-side heat transfer coefficient and pressure drop were calculated using commonly adopted equations for turbulent flow in a smooth tube. The numerical calculations were performed in three dimensions for three frontal air velocities of 1.0, 2.0, and 3.0 m/s, yielding hydraulic diameter Reynolds numbers from 297 to 999. Investigated were five tube geometries, including a round tube, three elliptical oval tubes, and a flat oval tube. The round tube has a 15.875 mm (5/8") outside diameter and serves as the baseline tube. The four oval tubes were made by reforming the baseline round tube and have the same perimeter as that of the round tube. The aspect ratios of the three elliptical tubes are 2.00, 3.00, and 4.29, respectively, and the aspect ratio of the flat oval tube is 3.00. As the tube aspect ratio is increased, the air-side heat transfer coefficient and pressure drop decrease, but the water-side heat transfer coefficient and pressure drop increase. At 2.0 m/s frontal velocity, the 3.00 aspect ratio elliptical tube yields a 6.9% lower air-side heat transfer coefficient and a 45.9% lower air pressure drop than the round tube. As compared to the 3.00 aspect ratio elliptical tube, the same aspect ratio flat tube has a 0.6% higher air-side heat transfer coefficient and a 2.5% higher air pressure drop.