The emissivities of 2 very broad parallel plates, surface 1 and surface 2, respectively, are 0.9 and 0.9, respectively. They were maintained at 49C and 21C, respectively. An aluminum plate with an emissivity of 0.06 was used as the medium (surface

m) which can transmit heat and is placed between the two plates. a. Draw an electrical network analogous to the radiation heat transfer process and the direction of the heat transfer arrow, for radiant heat transfer from surface 1 to surface 2, determine b. total heat resistance, c. net radiant heat rate per unit area from surface 1 to 2 (Joule/ (second.m?). Boltzmann constant = 1.380649 10-23 Joule/ (second.m^2 K^4).