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A household oven door of height 0.6-m and width 0.7-m reaches an average surface temperature of Ts=48°C during operation. Ambient air temperature is T=22°C. The door has an Emissivity value

of e-0.85. Surrounding temperature is also Tsur-22 °C. Use the following property values: \begin{array}{l} \text { Air: } \mathrm{v}=15.89 \times 10^{-6} \mathrm{~m}^{2} / \mathrm{s} ; \mathrm{K}_{\mathrm{f}}=26.3 \times 10^{3} \mathrm{~W} / \mathrm{mk} \\ \alpha=22.5 \times 10^{-6} \mathrm{~m}^{2} / \mathrm{s} ; \mathrm{Pr}=0.707 \end{array} \text { Stefan-Boltzmann Constant: } \sigma=5.67 \times 10^{-8} \mathrm{w} / \mathrm{m}^{2} \mathrm{k}^{4} Find: (1) What is the B value? (2 points)

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