申論題

7.(15%) A thin rod of diameter D, shown in Fig. 5, is initially in equilibrium with its surroundings, a large vacuum enclosure at temperature Tsur. Suddenly, an electrical current I (Ampere) is passed through the rod having an electrical resistivity ρe (Ωㆍ m) and emissivity ε. Other pertinent thermophysical properties are identified in Fig. 5. Derive the transient, finite-difference equation for node m. (P.S.: The resistance: Length, A: Area)