A blackbody radiation source at Ti = 500?C is used to irradiate three different surfaces, namely,
(i) aluminum (commercial sheet),
(ii) nickel oxide, and
(iii) paper. The irradiating surfaces have an area Ar = 1 m2 and are assumed gray, diffuse, and opaque. Use the emissivities in Table C.18 [for
(ii) extrapolate; for others use the available data].
(a) Sketch the radiation heat transfer arriving and leaving the surface, showing the blackbody emitter and the irradiated surface [see Figure 4.9(b)]. Show heat transfer as irradiation Qr,i, absorption Qr,α, reflection Qr,ρ, emission Qr,, and radiosity Qr,o (sum of emission and reflection).
(b) If the three surfaces are kept at Ts = 100?C, determine the amounts of reflected and absorbed energies.
(c) Determine the rates of energy emitted and the radiosity for each surface.
(d) Determine the net radiation heat transfer rate for each surface. Which surface experiences the highest amount of radiation heating?