Experiments were performed to determine the heat transfer and fluid flow characteristics of their air side of a cross-flow compact heat exchanger. This heat exchanger, which is used for passenger compartment heating in autombiles, consists of flat, internally ribbed brass tubes with louvered copper fins soldered to the outside of the tube. The high fin density (approximately 20 fins/cm of tube) makes it exceptionally compact. The heat exchanger was tested in a wind tunnel with hot water flowing through the tubes. Temperatures, the heat transfer rate, and the pressure drop on the air side were measured. From the measured heat transfer rate and the known fin and prime surface areas, the air side heat transfer coefficient was calculated at several different air flow rates. To determine the effects of louvering the fins, similar tests were conduced on a heat exchanger having the same fin density but without louvers on the fins. Results are presented as plots of Fanning friction factor and Colburn j factor against the Reynolds number in the range 150 to 300. Comparisons are drawn with standard correlations for the entrance region of rectangular ducts and for flow through offset strip fins. Louvering was found to produce an approximately 25 % increase in heat transfer and 110 % increase in pressure drop relative to the plain fin.
A study of a very compact heat exchanger used for passenger compartment heating in automobiles
Untersuchung eines sehr kompakten Wärmetauschers für die Beheizung des Fahrgastraums in Autos
1992
10 Seiten, 14 Bilder, 2 Tabellen, 14 Quellen
Conference paper
English
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