Effect of temperature dependent properties on natural convection of water near its density maximum in enclosures

A numerical study has been performed to investigate the problem of natural convection of water near its density maximum in an enclosure with temperature dependent properties. The viscosity and thermal conductivity of the water is varied with reference temperature and calculated by fourth degree polynomial in all grid points. The governing equations are solved by finite volume method. The results are depicted graphically in the form of streamlines, isotherms and velocity vectors and are discussed for various values of reference temperature parameter, Rayleigh number, density inversion parameter and aspect ratio. It is observed that the temperature of maximum density leaves strong effects on fluid flow and heat transfer due to the formation of bi-cellular structure. The heat transfer rate behaves non-linearly with density inversion parameter. The average Nusselt number values considering temperature-dependent fluid properties are lower than the constant properties result except density. There is no significant effect on fluid flow and temperature distributions when changing the values of temperature difference parameter. The average heat transfer rate considering temperature-dependent viscosity are higher than considering both temperature-dependent viscosity and thermal conductivity.