Question Bank • QB_EXP_DFE_RAD_001 NAT • 2 Marks

Section 7: Dairy and Food Engineering

Radiation Heat Transfer & Emissivity

Subtopic: Emissive power of food baking surface

Question Statement:

A baking oven radiant heating panel operates at a surface temperature of $T = 250^\circ\text{C}$ ($523.15\text{ K}$) with a surface emissivity of $\epsilon = 0.85$. Taking the Stefan-Boltzmann constant $\sigma = 5.67 \times 10^{-8}\text{ W/(m}^2\,\text{K}^4\text{)}$, the total emissive power of the panel is ________ $\text{W/m}^2$ (round off to one decimal place).

Answer Key:

3610.0

Step-by-Step Solution & Explanation

From the Stefan-Boltzmann law for a gray surface: $E = \epsilon \sigma T^4$ Given $\epsilon = 0.85$, $\sigma = 5.67 \times 10^{-8}\text{ W/(m}^2\text{ K}^4\text{)}$, and $T = 523.15\text{ K}$: $E = 0.85 \times (5.67 \times 10^{-8}) \times (523.15)^4 = 3610.0\text{ W/m}^2$
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