摘要
In the present paper,the effect of variable fluid properties(density,viscosity,thermal conductivity and specific heat) on the convection in the classical Rayleigh-Bénard problem is investigated.The investigation concerns water,air,and engine oil by taking into account the variation of fluid properties with temperature.The results are obtained by numerically solving the governing equations,using the SIMPLE algorithm and covering large temperature differences.It is found that the critical Rayleigh number increases as the temperature difference increases considering all fluid properties variable.However,when the fluid properties are kept constant,calculated at the mean temperature,and only density is considered variable,the critical Rayleigh number either decreases or remains constant.
In the present paper, the effect of variable fluid properties （density, viscosity, thermal conductivity and specific heat） on the convection in the classical Rayleigh-Benard problem is investigated. The investigation concerns water, air, and engine oil by taking into account the variation of fluid properties with temperature. The results are obtained by numerically solving the governing equations, using the SIMPLE algorithm and covering large temperature differences. It is found that the critical Rayleigh number increases as the temperature difference increases considering all fluid properties variable. However, when the fluid properties are kept constant, calculated at the mean temperature, and only density is considered variable, the critical Rayleigh number either decreases or remains constant.
