Enhancing heat transfer in vortex generator-type multifunctional heat exchangers
Résumé
Global and local analysis of the heat transfer in turbulent vortical flows is studied using threedimensionalnumerical simulations. Vorticity is generated by inclined vortex generators in a turbulentcircular pipe flow with twelve different configurations that fall into three categories. In the first categoryare rows of trapezoidal vortex generators in different arrangements; in the second category the vortexgenerators are fixed at certain distance from the tube wall, and the third category has vortex generatorrows between which a row of small protrusions are inserted on the tube wall. First, a global analysis ofthe thermal performance is performed for all these configurations, which are also compared with otherheat exchangers from the literature. New correlations for the friction factor and Nusselt number are thenobtained. Local analysis of the effect of the flow structure on the temperature distribution is carried outfor the four configurations showing the best performances. The local analysis involves studying thestreamwise vorticity flux to characterize the convective transport process, the turbulent kinetic energycharacterizing the turbulent mixing, and finally the local Nusselt number.