A note on the Nusselt number adjacent to a vertical isothermal plate immersed in thermally stratified water at low temperatures

The local Nusselt number of a buoyancy induced boundary layer adjacent to an isothermal vertical plate immersed in a linearly thermally stratified water at low temperatures is investigated. The results are obtained with direct numerical solution of the boundary layer equations. Both upward and downward flow is considered. When the plate temperature is equal to maximum density temperature the Nusselt number shows a maximum. It was also observed that the Nusselt number curve changes from linear to nonlinear form as the plate temperature varies from the linear to nonlinear temperature range.