Chapter 1, Problem 1.83P

The diameter and surface emissivity of an electricallyheated plate are $D=300\text{mm}$ and $\in =0.80,$ respectively.
(a) Estimate the power needed to maintain a surfacetemperature of 200°C in a room [or which the airand the walls are at 25°C. The coefficient characterizing heat transfer by natural convection depends on the surface temperature and, in units of ${\text{W/m}}^{\text{2}}\cdot \text{K}$ , may be approximated by an expression ofthe form $h=0.80{\left(T_s-T_{\infty }\right)}^{1/3}$ .
(b) Assess the effect of surface temperature on thepower requirement, as well as on the relative contributions of convection and radiation to heat transfer from the surface.