Heat transfer and entropy generation of mixed convection flow in Cu-water nanofluid-filled lid-driven cavity with wavy surface

A numerical investigation is performed into the heat transfer effect and associated entropy generation of mixed convection flow in a lid-driven wavy-wall cavity filled with Cu-water nanofluid. In modeling the cavity, it is assumed that the left wall has a flat surface and a constant high temperature, while the right wall has a wavy surface and a constant low temperature. In addition, the left wall moves in the vertical direction, while the right wall remains stationary. Finally, the upper and lower walls are both flat and insulated. The simulations focus on the effects of the flow parameters and wavy-wall geometry conditions on the Nusselt number, entropy generation rate and Bejan number. In addition, the energy flux vectors are used in order to clarify the heat energy transport process. The results show that the mean Nusselt number and total entropy generation increase as the Richardson number, nanoparticle volume fraction and Reynolds number increase. The Bejan number reduces as the irreversibility distribution ratio increases, but increases as the Reynolds number increases. The mean Nusselt number and total entropy generation both increase as the amplitude of the wavy surface increases. Finally, an optimal heat transfer effect is obtained given an appropriate wavelength of the wavy surface depending on the Richardson numbers. (C) 2017 Elsevier Ltd. All rights reserved.