A row of regularly spaced, cylindrical heating elements (1) is used to cure a surface coating that is applied to a large panel (2) positioned below the elements. A second large panel (3), whose top surface is well insulated, is positioned above the elements. The elements are black and maintained at T₁ = 600 K, while the panel has an emissivity of ?₂ = 0.5 and is maintained at T₂ = 400 K. The cavity is filled with a nonparticipating gas and convection heat transfer occurs at surfaces 1 and 2, with h₁ = 10 W/m² ? K and h₂ = 2 W/m² ? K. (Convection at the insulated panel may be neglected.)

(a) Evaluate the mean gas temperature, T_m.

(b) What is the rate per unit axial length at which electrical energy must be supplied to each element to maintain its prescribed temperature?

(c) What is the rate of heat transfer to a portion of the coated panel that is 1 m wide by 1 m long?

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3) D= 25 mm s= 50 mm 42 Gas, T 2)