Type your question here Radiation Heat Transfer in Two-Surfac a Consider an encl
ID: 1827184 • Letter: T
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Radiation Heat Transfer in Two-Surfac a Consider an enclosure consisting of two opaque surfaces Enclosu shown 13-24, and try to determine the net radiation heat transfer between the two surfaces with the Al and A Surfaces 1 and 2 emissivities 81 and E2 area are maintained at uniform temperatures 11 and 12, respectively. The ar two surfaces in the enclosure, and we can write That is, the net rate of radiation heat transfer from surface 1 to surface 2 m equal the net rate of radiation heat transfer from surface 1 and the net ra radiation heat transfer to surface 2. The radiation network of this two-surface enclosure consists of two surface resistances and one space resistance, as shown in Fig. 13-24. In an electrical network, the electric current flowing through these resistances connected in series would be determined by dividing the otential difference between sure points A and B by the total resistance betw ne same two points. The net ated rate of radiation transfer is determined in the manner and is expressed as R1 R12 R2 (13-36 A F This important result is applicable to any two gray, diffuse, and opaque sur faces that form an enclosure. The view factor F12 depends on the geometry and must be determined first. Simplified forms of Eq. 13-36 for some famil iar arrangements that form a two-surface enclosure are given in Table Note that F12 1 for all of these special cases. EXAMPLE 13-7 Radiation Heat Transfer between Parallel Plates Two 800 very large parallel plates are maintained at uniform temperatures K and 500 K and have emissivities 81 tively, as shown in Fig. 13-25. Determine the net rate of radiation h fer between the two surfaces per unit surface area of the pla 0.7, resp rge DaraExplanation / Answer
heat = 5.67*10^-8*(573^4 -353^4)/[(1-0.8)/(0.15*0.2 + 1/(.15*0.2)]
= 5.23*10^3/40
=130
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