Influence of the geometry on the thermohydraulics of a compound heat exchanger consisting of louvered fins and delta winglets

Louvered fin heat exchangers with round tubes are frequently used in heating, ventilation, air conditioning and refrigeration applications. In this paper delta winglet vortex generators are punched out of the louver surface, resulting in a so called compound design. Three-dimensional numerical simulations were performed. The delta winglets serve to reduce the size of the tube wakes, which are zones of poor heat transfer. A screening analysis of the most important geometrical parameters showed that the delta winglet geometry highly contributes to the thermal and hydraulic performance at low Reynolds numbers, while at higher Reynolds numbers the performance is mainly determined by the louver geometry. The compound heat exchanger has a better thermal hydraulic performance than when the louvers or the delta winglets are applied separately. The performance of the compound design is also compared to louvered, slit and plain fin heat exchangers. This clearly shows its potential. Especially for low Reynolds applications, the compound heat exchanger can be made smaller in size and thus more economical in cost.

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