Problem. 13–88 Two coaxial cylinders of diameters D1 = 0.10 m and D2 = 0.50 m and emissivities ε1 = 0.7 and ε2 = 0.4 are maintained at uniform temperatures of T1 = 750 K and T2 = 500 K, respectively. Now a coaxial radiation shield of diameter D3 = 0.20 m and emissivity ε3 = 0.2 is placed between the two cylinders. Determine the net rate of radiation heat transfer between the two cylinders per unit length of the cylinders and compare the result with that without the shield.

Reconsider Prob. 13–88. Using EES (or other) software, investigate the effects of the diameter of the outer cylinder and the emissivity of the radiation shield on the net rate of radiation heat transfer between the two cylinders. Let the diameter vary from 0.25 m to 0.50 m and the emissivity from 0.05 to 0.35. Plot the rate of radiation heat transfer as functions of the diameter and the emissivity, and discuss the results.

Problem. 13–88

Two coaxial cylinders of diameters D₁ = 0.10 m and D₂ = 0.50 m and emissivities ε₁ = 0.7 and ε₂ = 0.4 are maintained at uniform temperatures of T₁ = 750 K and T₂ = 500 K, respectively. Now a coaxial radiation shield of diameter D₃ = 0.20 m and emissivity ε₃ = 0.2 is placed between the two cylinders. Determine the net rate of radiation heat transfer between the two cylinders per unit length of the cylinders and compare the result with that without the shield.