Conjugate heat transfer in a duct using nanofluid by two-phase Eulerian–Lagrangian method: Effect of non-uniform heating

Abstract

The underlying physics behind the effect of non-uniform heating on the heat transfer characteristics for flow of Al2O3-water nanofluid through a duct having finite wall thickness subjected to sinusoidal heat flux has been numerically investigated in this study. The nanofluid is modelled as a single fluid with two phases using the Eulerian-Lagrangian formulation. The concomitant implications of thermal conductivity ratio of solid to fluid, outer tube diameter to inner tube diameter ratio, amplitude of sinusoidal heat flux and volume fraction of nanoparticles on the thermal attributes have been explored and quantified by local and average Nusselt number. The results elucidate a close resemblance between the nature of the variation of local Nusselt number and the applied heat flux, particularly at the intermediate region of the channel. The results also reveal a damping effect on the conjugate heat transfer due to the increase in conducting wall thickness, irrespective of the volume fraction of nanofluid. The confluence of various key parameters on the variation of the magnitudes of the crests and troughs of local Nusselt number are analyzed and this variation proves to be a prime factor in determining the variation of average Nusselt number. Furthermore, the average Nusselt number decreases with amplitude of heat flux. The rate of heat transfer for flow of base fluid through a duct having finite wall thickness is always lower in case of non-uniform heating. However, the use of nanofluid as the heat transfer medium can compensate the decrement in heat transfer due to non-uniform heating.