Heat transfer and entropy generation in fully-developed mixed convection nanofluid flow in vertical channel

A numerical investigation is performed into the heat transfer and entropy generation within a fully-developed mixed convection flow of Al2O3-water nanofluid in a vertical channel. The simulations focus specifically on the effects of the Brinkman number, mixed convection dimensionless parameter, and nanoparticle concentration on the velocity distribution, temperature distribution, Nusselt number and entropy generation within the channel. In performing the simulations, the velocity and temperature fields within the channel are computed using the differential transformation method (DTM) given the assumption of asymmetric heated walls. It is shown that the results obtained by the DTM method for the Nusselt numbers on the hot and cold walls, respectively, are in good agreement with the analytical results presented in the literature. In addition, it is shown that for a lower Brinkman number, the local Nusselt number of the nanofluid on the hot wall is greater than that of pure water and increases with an increasing nanoparticle concentration. However, given a higher value of the Brinkman number, the local Nusselt number of the nanofluid on the cold wall is less than that of pure water. Finally, it is shown that the average entropy generation number of the nanofluid is less than that of pure water. In general, the results presented in this study confirm the accuracy and feasibility of the DTM method in solving fluidic heat transfer problems and provide a useful insight into the effects of viscous dissipation on the entropy generation within vertical asymmetrically-heated channels containing mixed convection flow. (C) 2014 Elsevier Ltd. All rights reserved.