Chapter 13, Problem 13.83P

A small disk of diameter $D_1=50\text{mm}$ and emissivity ${\epsilon }_1=0.6$ is maintained at a temperature of $T_1=900\text{K}$ . The disk is covered with a hemispherical radiation shield of the same diameter and an emissivity of ${\epsilon }_2=0.02$ (both sides). Tue disk and cap are located at the bottom of a large evacuated refractory container $\left({\epsilon }_4=0.85\right)$ , facing another disk of diameter $D_3=D_1$ , emissivity ${\epsilon }_3=0.4$ , and temperature $T_3=400\text{K}$ . The view factor F₂₃of the shield with respect to the upper disk is 0.3.

(a) Construct an equivalent thermal circuit for the above system. Label all nodes, resistances, and currents.
(b) Find the net rate of heat transfer between the hot disk and the rest of the system.