Optimization of winglet vortex generators combined with riblets for wall/fluid heat exchange enhancement

Abstract This work focuses on the thermal performance enhancement of fluid heat exchanger with asymmetrical heating. Industrial heat exchangers such as solar receivers often have asymmetrical heating. The forced internal convective heat transfer and friction loss behaviours are studied for turbulent flows promoted by a combination of delta winglet vortex generators (DWVG) and riblets. The use of such a combination of devices maximizes the efficiency of the channel heat exchanger. The efficiency is characterized by two criteria: one based on the turbulent kinetic energy and another one based on the Nusselt number and the friction coefficient. The comparison of those two criteria allows separating the heat transfer intensification due to turbulence and exchange surface enhancement. Several heights of DWVGs and various sizes and shapes of downstream riblets are simulated using a Reynolds Averaged Navier–Stokes (RANS) approach. The numerical results show that bigger and thinner riblets provide the best thermal performance. Concerning the DWVGs, a half-channel height is found to be the optimum.

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