Consider the two parallel coaxial disks of diameters a and b, shown in Fig. P21€“132. For this geometry, the view factor from the smaller disk to the larger disk can be calculated from

where, A = a/2L, B = b/2L, and C = 1 + [(1 + A²)/B²]. The diameter, emissivity, and temperature are 20 cm, 0.60, and 600°C, respectively, for disk a, and 40 cm, 0.80, and 200°C for disk b. The distance between the two disks is L = 10 cm.

(a) Calculate F_ab and F_ba.

(b) Calculate the net rate of radiation heat exchange between disks a and b in steady operation.

(c) Suppose another (infinitely) large disk c, of negligible thickness and ε = 0.7, is inserted between disks a and b such that it is parallel and equidistant to both disks. Calculate the net rate of radiation heat exchange between disks a and c and disks c and b in steady operation.

Transcribed Image Text:

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