Problem 3 (10 pts) The variation of emissivity of a surface at a specified temperature (1000...
PROBLEM 2-Emissivity A wall is at 300K and 600K. It has the following spectral emissivity in the long wavelength end of the thermal radiation spectrum: <10 μm = 0.0 10 μm to 100 μm > 100 μm 0.0 0.35 Calculate the total emissivity and emissive power at the specified temperatures. Does the total emissivity increase or decrease at the higher temperature?
A small object with an opaque, diffuse surface at a temperature
of 500 K is suspended in a large furnace with walls at 2000 K.
Assume that the walls of the furnace provide a diffuse irradiation
to the object at a blackbody temperature equal to the furnace wall
temperature. The object’s surface has a spectral hemispherical
emissivity and absorptivity as given below. (a) Determine the total
emissivity and total absorptivity of the object’s surface. Partial
Ans: ?=0.021 (b) Evaluate the...
Problem 3 (15 points) A white ceramic surface has a hemispherical spectral emissivity distribution at 1600 K as shown. What is the hemispherical total emissivity of the surface at this surface temperature? My guess is you need to do a numerical integration here. 1.0 0.8 0.6 E N 0.4 0.2 10 10 2 4 6 8 10 12 λ, μ
Problem 3 (15 points) A white ceramic surface has a hemispherical spectral emissivity distribution at 1600 K as shown. What...
1.0 3) A diffuse surface at T = (600 + 200)K.has the spectral, hemispherical emissivity illustrated. Determine the following: 0.8 2 - 2 2 - 5 3 a. the total, hemispherical emissivity is a = (+0.001) 0.4 b. the total emissive power is E = kW/m2 (+0.1%) 0 5 2. Gum
1.0 3) A diffuse surface at T = 1200K.has the spectral, hemispherical emissivity illustrated. Determine the following: o. E2 00 2. = 2 um 12 = 5 um 3 a. the total, hemispherical emissivity is a = (+0.001) E1 0.4 b. the total emissive power is E = kW/m² (+ 0.1%) 0 0 2 5 2. (um)
1.0 A diffuse surface at T = (9400) K. has the spectral, hemispherical emissivity illustrated. Determine the following: E2 0.8 2. = 2 um 12 = 5 um a. the total, hemispherical emissivity is ε = (+0.001) E, () E1 0.4 b. the total emissive power is E = kW/m² (+0.1%) 0 2 5 (um)
1.0 A diffuse surface at T = (2200) K. has the spectral, hemispherical emissivity illustrated. Determine the following: 0.8 21 = 2 pm 12 = 5 um a. the total, hemispherical emissivity is ε = (+0.001) E, () E1 0.4 b. the total emissive power is E = kW/m² (+ 0.1%) 0 2 5 (um)
Problem 5 (10 points) A gray surface has a directional emissivity isotropic with respect to circumferential angle as shown in the figure. The properties are (a) What is the hemispherical emissivity of this surface? (b) If the energy from a directions, what fraction of the incident energy is absorbed by this surface? (c) If the surface is placed in a very cold environment, at what rate must energy be added per unit area to maintain the surface temperature at 1000...
Problem 5 (10 points) A gray surface has a directional emissivity isotropic with respect to circumferential angle as shown in the figure. The properties are (a) What is the hemispherical emissivity of this surface? (b) If the energy from a directions, what fraction of the incident energy is absorbed by this surface? (c) If the surface is placed in a very cold environment, at what rate must energy be added per unit area to maintain the surface temperature at 1000...
2. (25 Pts) A horizontal, opaque surface at a steady- state temperature of 77°C. The emissive power of the surface is 628W/m2, the irradiation is 1380 W/ m2, and the absorptivity is 0.40. a) (5 Pts) determine the reflectivity of the surface. b) (5 Pts) Determine the radiosity of the surface Determine the net radiation heat transfer rate for this surface. (Indicate whether this heat transfer is to the surface or from the surface.) d) (5 Pts) Calculate the emissivity...