logistic_guy
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The diameter and surface emissivity of an electrically heated plate are \(\displaystyle D = 300 \ \text{mm}\) and \(\displaystyle \varepsilon = 0.80\), respectively.
\(\displaystyle \bold{(a)}\) Estimate the power needed to maintain a surface temperature of \(\displaystyle 200^{\circ}\text{C}\) in a room for which the air and the walls are at \(\displaystyle 25^{\circ}\text{C}\). The coefficient characterizing heat transfer by natural convection depends on the surface temperature and, in units of \(\displaystyle \text{W}\text{/m}^{2} \cdot \text{K}\), may be approximated by an expression of the form \(\displaystyle h = 0.80(T_s - T_{\infty})^{1/3}\).
\(\displaystyle \bold{(b)}\) 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.
\(\displaystyle \bold{(a)}\) Estimate the power needed to maintain a surface temperature of \(\displaystyle 200^{\circ}\text{C}\) in a room for which the air and the walls are at \(\displaystyle 25^{\circ}\text{C}\). The coefficient characterizing heat transfer by natural convection depends on the surface temperature and, in units of \(\displaystyle \text{W}\text{/m}^{2} \cdot \text{K}\), may be approximated by an expression of the form \(\displaystyle h = 0.80(T_s - T_{\infty})^{1/3}\).
\(\displaystyle \bold{(b)}\) 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.