A friction factor correlation for the offset strip-fin matrix

This work deals with the offset strip fin surface geometry used in parallel plate fin 'compact' heat exchangers. Previous attempts to correlate existing data have been impaired by the possibility that burrs may exist on the leading and trailing edges of the fins. Such burrs are believed to affect the heat transfer and friction characteristics. Patankar and Prakash (1981) have numerically predicted the heat transfer and friction characteristics of one geometry, but were unable to validate their results because of lack of accurate data on the geometry modeled. The experimental objective of this work was to obtain friction data on scaled-up matrix geometries that had precisely known dimensions, and no burred fin-edges. Data were taken on eight surface geometries that span a wide range of geometric parameters. These data were correlated within + or - 10 percent to provide a generalized equation for the friction factor as a function of the geometric parameters and Reynolds number. The resulting correlation predicts actual heat exchanger friction data with good accuracy. This work further suggests that the effect of burrs on the published data for actual heat exchanger geometries is insignificant.