Chapter 1, Problem 1.83P

The diameter and surface emissivity of an electrically heated plate are $D=300\text{mm}$ and $\epsilon =0.80,$ respectively.

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