Question: A furnace wall consists of two layers of firebrick, kl = 0.8 Btu/(h ft OF) and k2 = 0.1 Btu/(h ft OF), and a steel plate k3 = 25 Btu/(h ft OF) as shown in the following illustration.
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Calculate the heat flux [Btu/(h ft2)] and the interface temperatures between materials 1 and 2,2 and 3.