A numerical study on non-homogeneous model for the conjugate-mixed convection of a Cu-water nanofluid in an enclosure with thick wavy wall

摘要

Conjugate heat transfer due to the mixed convection and conduction of a Cu-water nanofluid in a thick-wall enclosure is conducted numerically based on the non-homogeneous model for nanofluids. We consider an enclosure with a thick wavy hot left side wall with the right vertical wall being allowed to move vertically downwards to develop a shear driven flow. This in combination with the horizontal temperature gradient leads to a mixed convection within the enclosure. The wavy geometry is transformed to a square domain by the co-ordinate transformation method and the governing equations along with the specified boundary conditions are solved using the finite volume method. The Richardson number and Reynolds number, which governs the mixed convection, are varied up to a moderate range at different choices of the nanoparticle volume fraction and its size, solid-to-fluid conductivity ratio, wave length and amplitude of the wavy interface. The heat transfer characteristics of the nanofluid is analyzed by evaluating the entropy generation and Bejan number. Results show that the impact of the dispersion of nanoparticles on the mixed convection is pronounced for a higher range of the Richardson number and nanoparticle volume fraction. The heat transfer and entropy generation both enhances with the increase of wave amplitude and wave number, however, the heat transfer enhancement rate dominates the entropy generation rate. Entropy generation due to heat transfer is more significant than that of fluid friction irreversibility for all the cases addressed here.