Numerical study of flow patterns of compact plate-fin heat exchangers and generation of design data for offset and wavy fins

Abstract

Thermo-hydraulic design of compact heat exchangers (CHEs) is strongly dependent upon the predicted/measured dimensionless performance (Colburn factor j and Fanning friction factor f vs. Reynolds number Re) of heat transfer surfaces. Also, air (gas) flow maldistribution in the headers, caused by the orientation of inlet and outlet nozzles in the heat exchanger, affects the exchanger performance. Three typical compact plate-fin heat exchangers have been analyzed using Fluent software for quantification of flow maldistribution effects with ideal and real cases. The headers have modified by providing suitable baffle plates for improvement in flow distribution. Three offset strip fin and 16 wavy fin geometries used in the compact plate-fin heat exchangers have also been analyzed numerically. The j and f vs. Re design data are generated using CFD analysis only for turbulent flow region. For the validation of the numerical analysis conducted in the present study, a rectangular fin geometry having same dimensions as that of the wavy fin has been analyzed. The results of the wavy fin have been compared with the analytical results of a rectangular fin and found good agreement. Similarly, the numerical results of offset strip fin are compared with the correlations available in the open literature and found good agreement with most of the earlier findings.