Conjugate Buoyant Convective Transport of Different Nanofluids in An Enclosed Annular Geometry

A vertical annular configuration with differently heated cylindrical surfaces and horizontal adiabatic boundaries is extensively studied due to many industrial applications. In this paper, we investigate the effects of conjugate buoyant heat transport within water based nanofluid with different nanoparticles such as alumina, titanium oxide or copper, which is contained in the gap of the enclosed annulus. The enclosed annulus is constituted by a thick inner cylinder with a constant high temperature, an exterior boundary with a constant low temperature and thermally insulated upper and lower surfaces. By investigating heat transport for broad spectrum of Rayleigh number, solid wall thickness, thermal conductivity ratio and nanoparticle volume fraction, we found that the influence of wall thickness on thermal dissipation rate along wall and interface greatly depend on conductivity ratio and vice-versa. In particular, we uncover that the choice of nanoparticle in a nanofluid and its concentration are key factors in enhancing the thermal transport along the interface. Specially, copper based nanofluids produces higher heat transport among other nanoparticles, and increasing nanoparticle concentration leads to enhanced thermal dissipation along interface. Our results are applicable to choose nanofluids along with other critical parameters for the desired heat transport.