13-56 Consider two rectangular surfaces perpendicular to each other with a common edge which is 1.6 m long. The horizontal surface is 0.8 m wide, and the vertical surface is 1.2 m high. The horizontal surface has an emissivity of 0.75 and is maintained at 450 K. The vertical surface is black and is maintained at 700 K. The back sides of the surfaces are insulated. The surrounding surfaces are at 290 K and can be considered to have an emissivity of 0.85. Determine the net rate of radiation heat transfer between the two surfaces and between the horizontal surface and the surroundings. FIGURE P13–56 Tz= 700 K e2 = 1 W = 1.6 m T3 = 290 K E3= 0.85 Lz= 1.2 m A2 L1 = 0.8 m A1 Tj = 450 K €1 = 0.75

consider a 1m by 1m blackbody surface at ts = 300k. determine the blackbody emissive power. determine the total intensity. determine the radiosity. if the plane size is 100E-6m can you use the black body concept?

Consider a cuboidal furnace (l = 5 m, b = 4 m, h = 3 m), whose surfaces closely approximateblack surfaces. The base, top, and side surfaces of the furnace are maintained at uniformtemperatures of (1040) K, (840) K, and (540) K, respectively. Determine (a)the net rate of radiation heat transfer between the base and the side surfaces, (b) the net rate ofradiation heat transfer between the base and the top surface, and (c) the net radiation heattransfer from the base surface.   Steam in a heating system flows through tubes whose outer radius is r1 = (3) cm and whosewalls are maintained at a temperature of 127 °C. Circular aluminum fins (k = 180 W/m K) ofouter radius r2 = (6) cm and constant thickness t = 1 mm are attached to the tube. The spacebetween the fins is 3 mm. Heat is transferred to the surrounding air at 27 °C, with a combinedheat transfer coefficient of 60 W/m2 K. Determine the increase in heat transfer from the tubeper meter of its length as a result of adding fins

A 5 mm-thick steel firewall is suddenly exposed to a radiant heat source that can be approximated as a blackbody at 1000K. How long will it take for the surface to reach 500 K if the initial temperature of the wall is 300K?