A wall-mounted natural gas heater uses combustion on a

Chapter , Problem 13.127

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A wall-mounted natural gas heater uses combustion on a porous catalytic pad to maintain a ceramic plate of emissivity c 0.95 at a uniform temperature of Tc 1000 K. The ceramic plate is separated from a glass plate by an air gap of thickness L 50 mm. The surface of the glass is diffuse, and its spectral transmissivity and absorptivity may be approximated as 0 and 1 for 0 0.4 m, 1 and 0 for 0.4 1.6 m, and 0 and 0.9 for 1.6 m. The exterior surface of the glass is exposed to quiescent ambient air and large surroundings for which T Tsur 300 K. The height and width of the heater are H W 2 m. (a) What is the total transmissivity of the glass to irradiation from the ceramic plate? Can the glass be approximated as opaque and gray? (b) For the prescribed conditions, evaluate the glass temperature, Tg, and the rate of heat transfer from the heater, qh. (c) A fan may be used to control the convection coefficient ho at the exterior surface of the glass. Compute and plot Tg and qh as a function of ho for 10 ho 100 W/m2 K. Participati