Heat transfer characteristics of a constant heat flux vertical plate in water

Experimental examination of the heat transfer characteristics of a vertical plate in water is presented. Results are given as the variation of local Nusselt number with Rayleigh number for different heat fluxes. The experiments included temperature measurements and flow visualization by the use of the simple and precise method of electrochemical formation of dye technique. Arrangements were made so that color changes occured both at the surface of the vertical plate and within the boundary layer. The free convection heat transfer in water, as expressed by the power-law relationship between the Nusselt number and Rayleigh number, Nu = 0.89 Ra^0.2, is shown to be adequate for the range of Rayleigh numbers 10⁴ < Ra < 10¹³ for a constant heat flux boundary condition. There appear to be similarities in the mechanisms of transition from laminar to turbulent boundary layer flow between those for natural convection and those for the Blasius-type forced flow over a flat plate. The Emmons spot source band for natural convection flow is large when compared to the narrow band for Blasius flow.