Example: Natural Convection – Flat Plate
A 10cm high vertical plate is maintained at 261°C in 260°C compressed water (16MPa). Determine the Nusselt number using the simple correlation for a vertical flat plate.
To calculate the Rayleigh number, we have to know:
- the coefficient of thermal expansion, which is: β = 0.0022
- the Prandtl number (for 260°C), which is: Pr = 0.87
- the kinematic viscosity (for 260°C), which is ν = 0.13 x 10-6 (note that, this value is significantly lower than that for 20°C)
The resulting Rayleigh number is:
The resulting Nusselt number, which represents the enhancement of heat transfer through a fluid layer as a result of convection relative to conduction across the same fluid layer is: