Modeling laminar heat transfer in a curved rectangular duct with a computational fluid dynamics code

Flow and convective heat transfer in a curved rectangular channel was modeled and the heat transfer coefficient assessed, using the FLUENT code. The conditions considered are representative of an application to solar collectors with heat pipes. A wide range of Reynolds and Dean numbers was considered, under laminar flow conditions. Results show that the Nusselt number for the curved duct is up to 10 times higher than for a straight duct, due to counterrotating secondary vortices formation. The flow pattern changes from one pair of vortices to three pairs, for a Dean number of 131. Above a Dean number of 1,200, the contours of secondary flow streamlines are similar and the variation in Nusselt number is small.