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 >

A furnace that has a 40-cm * 40-cm glass window can be considered to be a blackbody at 1200 K. If the transmissivity of the glass is 0.7 for radiation at wavelengths less than 3 mm and zero for radiation at wavelengths greater than 3 mm, determine the fraction and the rate of radiation coming from the furnace and transmitted through the window.

Liquid nitrogen is stored in a spherical tank of 1-m diameter, where tank surface is maintained uniformly at 80 K. The spherical tank is enclosed by a 1.6-m diameter concentric sphere with uniform surface temperature of 273 K. Both spherical surfaces have an emissivity of 0.01, and the gap between the inner sphere and outer sphere is vacuumed. Determine the rate of vaporization for the liquid nitrogen.

A spherical tank of diameter, D = 2 m that is filled with liquid nitrogen at 100 K is kept in an evacuated cubic enclosure whose sides are 3 m long. The emissivities of the spherical tank and the enclosure are 0.1 and 0.8, respectively. If the temperature of the cubic enclosure is measured to be 240 K, determine the net radiation of heat transfer to the liquid nitrogen, assuming the enclosure to be a real surface (as described earlier).

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

2. Two very long concentric cylinders of diameters Dı= 0.35 m and D2 = 0.5 m are maintained at uniform temperatures of T1 = 950 K and T2 = 500 K and have emissivities ɛ1 = 1 and ɛ2 = 0.55, respectively. Determine the net rate of radiation heat transfer between the two cylinders per unit length of the cylinders. What happens if the properties are just reversed.

Define Stefan-Boltzmann Law and emissivity. Is there any surface whose emissivity value is greater than 1? If no, explain the reason.