Reconsider Prob. 13–86. Using EES (or other) software, investigate the effect of the percent reduction in the net rate of radiation heat transfer between the plates on the emissivity of the radiation shields. Let the percent reduction vary from 40 to 95 percent. Plot the emissivity versus the percent reduction in heat transfer, and discuss the results.

Data from problem 86

A radiation shield that has the same emissivity ε₃ on both sides is placed between two large parallel plates, which are maintained at uniform temperatures of T₁ = 650 K and T₂ = 400 K and have emissivities of ε₁ = 0.6 and ε₂ = 0.9, respectively. Determine the emissivity of the radiation shield if the radiation heat transfer between the plates is to be reduced to 15 percent of that without the radiation shield.