Numerical investigation of non-Fourier natural convection of Newtonian nanofluids

Abstract

In the present study, effects of non-Fourier diffusion on the unsteady natural convection heat transfer are investigated in a cavity filled with Newtonian nanofluid. Time delay between heat flux and temperature gradient is modeled using dual-phase lag model (DPL) in which two scales of time, namely, relaxation and retardation times, are considered. Validation is performed using the results of unsteady free convection of Newtonian Fourier nanofluids problem in the literature in which an oscillating heat flux is partially imposed on one of the walls of the cavity. The results suggest that by increasing the volume fraction of solid particles, the non-Fourier effect is amplified in the flow. The DPL model underestimates the temperature distribution in comparison with the results of the Fourier free convection model. The results also indicate that by increasing the oscillation period of imposed boundary heat flux, the DPL model gives greater values for temperature distribution. Finally, the findings indicate that the DPL model gives greater values for the Nusselt number in comparison with those of the Fourier model.