Numerical study of turbulent natural convection of nanofluids in differentially heated rectangular cavities

Abstract

In this work we study numerically the turbulent natural convection of nanofluids (water + Al2O3/NTC/Cu) in rectangular cavities differentially heated. The objective is to compare the effect of the macro-structural aspect of the rectangular cavity and the effect of the types of nanofluids studied on the thermal exchange by turbulent natural convection in this type of geometry. Therefore, we have numerically treated the cases of these three nanofluids, for different particles volume fractions (0 ? ? ? 0.06) and for different form ratios of the rectangular cavity. The standard k-? turbulence model is used to take into account the effects of turbulence. The governing equations are discretized by the finite volume method using the power law scheme which offers a good stability characteristic in this type of flow. The results are presented in the form of streamlines and isothermal lines. The variation of the average Nusselt number is calculated as a function of the types of nanoparticles, of theirs particles volume fractions, for different form ratios of the cavity, and for different Rayleigh numbers. The results show that the average Nusselt number is greater as the form ratio is large and that the effect of the use of CNT in suspension in a water prevails for voluminal fractions and large Rayleigh numbers.