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 400 K. The vertical surface is black and is maintained at 550 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 transfers between the two surfaces, and between the horizontal surface and the surroundings. A. 2245 W, 725 W B. 1245 W, 725 W C. 1245 W, 825 W D. 2245 W, 825 W

2_5190874259647370... A cylindrical shape is with diameter of 1.2m and length of 1.2m. The top surface has an emissivity of 0.7 and temperature 500 K. The bottom surface has an emissivity of o.5 and temperature 650 K. The side surface has an emissivity of 0.4. Determine the shape factors for all surfaces. E 0.0 L=650 K II >

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Consider a 20-cm-diameter spherical ball at 800 K suspended in air as shown in Fig. 12-12. Assuming the ball closely approximates a blackbody, determine (a) the total blackbody emissive power, (b) the total amount of radiation emit- ted by the ball in 5 min, and (c) the spectral blackbody emissive power at a wavelength of 3 µ.m.

This experiment is conducted to determine the emissivity of a certain material. A long cylindrical rod of diameter D₁ = 0.01 m is coated with this new material and is placed in an evacuated long cylindrical enclosure of diameter D₂ = 0.1 m and emissivity 2 = 0.95, which is cooled externally and maintained at a temperature of 200 K at all times. The rod is heated by passing the electric current through it. When steady operating conditions are reached, it is observed that the rod is dissipating electric power at a rate of 16 W per unit of its length, and its surface temperature is 600 K. Based on these measurements, determine the emissivity of the coating on the rod. The emissivity of the coating on the rod is 0.1165

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

Two very large parallel plates are kept at uniform temperatures T1=800 K and T2=500 K, and have emissivities ε1=0.2 y  ε2=0.7, respectively, as shown in the figure. Determine the net rate of radiation heat transfer between the two surfaces per unit surface area of the plates.