Turbulent forced convection in a square duct heat exchanger (SDHX) equipped with combined vortex turbulators (CVT): A numerical investigation

This research presents a numerical study on flow structures, heat transfer, and thermal performance evaluation in a square duct heat exchanger (SDHX) equipped with combined vortex turbulators (CVTs). The aim of installing CVTs is to create vortex flow, impinging flow, and disrupt the thermal boundary layer, thereby enhancing the convective heat transfer coefficient and increasing the heat transfer ability and SDHX performance. V-shaped ribs and rectangular winglets are selected as CVTs due to their effectiveness in enhancing heat transfer rates. The study investigates the effects of CVT height (the values of a/H and b/H range from 0.05 to 0.20.), flow direction (V-apex pointing downstream (V-Downstream) and V-apex pointing upstream (V-Upstream)), and CVT arrangement (in-line and staggered arrangements) on flow structure and heat transfer characteristics. A comparison between V-shaped ribs and rectangular winglets is presented in terms of CVT types (A and B). The study focuses on turbulent flow with Reynolds numbers ranging from 3000 to 20,000. The results demonstrate that the flow behavior aligns with the proposed hypotheses, leading to increased heat transfer rates, which are 1.24 to 7.71 times greater than those of the empty duct. For thermal performance evaluation, the highest thermal enhancement factor (TEF) value of 1.77 is observed with type A CVT, in a staggered arrangement, and with the V-Upstream flow direction, when considering a Reynolds number (Re) of 3000. Additionally, the results of the study are presented in the form of TEF contours and correlations to assist in the design of vortex turbulators for heat exchange systems.