Entropy generation due to mixed convection over vertical permeable cylinders using nanofluids

This paper discusses the thermal stratification and suction/injection effects on the entropy generation and heat transfer due to convective boundary layer flow over a vertical stretching cylinder using Buongiorno's model for nanofluids. For the nanoparticle volume fraction, the boundary conditions are taken such that its normal fluxes are zero. The governing equations and the entropy equation are derived in cylindrical coordinates, in details. Similar transformations are used to convert the governing equation into ordinary differential equations and the resulting system is solved numerically using MATLAB function bvp4c. The obtained results are presented in terms of velocity profiles, temperature distributions, nanoparticle volume fraction, local entropy generation, skin friction coefficient and local Nusselt number. It is found that the minimum values of the entropy generation occur in the injection case, while the suction case maximizes the entropy generation. The increase in the thermal stratification parameter decreases the profiles of velocity temperature and nanoparticle volume fraction, while it enhances the entropy generation. (C) 2017 The Authors. Production and hosting by Elsevier B.V. on behalf of King Saud University.