9.14 Show that the laminar, free convection correlations for a vertical, isothermal flat plate of height L can be applied to a vertical, isothermal cylinder of diameter D and height L if the boundary layer thickness at the top of the cylinder is approximately one-fourth the cylin- der diameter. Determine the critical cylinder diameter, Derit, below which the flat plate correlations cannot be applied when the surface is at T, = 35°C, the surround- ing, quiescent air is at T = 25°C, and L = 0.75 m. Cal- culate the rate of free convection heat transfer from the vertical cylinder wall corresponding to the critical cyl- inder diameter. 0