Assuming the sun to be a black body emitting radiation with maximum intensity at 1 = 0.48u m, determine the following: (i) The surface temperature of the sun, and (ii) The heat flux at surface of the sun.
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- Determine the rate of radiant heat emission in watts per square meter from a blackbody at (a) 15C, (b) 600C, and (c) 5700C.1.28 The sun has a radius of and approximates a blackbody with a surface temperature of about 5800 K. Calculate the total rate of radiation from the sun and the emitted radiation flux per square meter of surface area.Two large parallel plates with surface conditions approximating those of a blackbody are maintained at 816C and 260C, respectively. Determine the rate of heat transfer by radiation between the plates in W/m2 and the radiative heat transfer coefficient in W/m2K.
- A circular ceramic plate that can be modeled as a blackbody is being heated by an electrical heater. The plate is 30 cm in diameter and is situated in a surrounding ambient temperature of 15°C where the natural convection heat transfer coefficient is 12 W/m2?K. If the efficiency of the electrical heater to transfer heat to the plate is 80%, determine the electric power that the heater needs to keep the surface temperature of the plate at 200°C.Two aligned parallel rectangles with dimensions 6 m * 8 m are spaced apart by a distance of 2 m. If the two parallel rectangles are experiencing radiation heat transfer as black surfaces, determine the percentage of change in radiation heat transfer rate when the rectangles are moved 8 m apart.Assuming sun to be a black body emitting radiation with maximum intensity at A = 0.5 u calculatione the temperature of the surface of the sun and the heat lux at its surface.
- Two infinite black plates at 800°C and 300°C exchange heat by radiation. Calculate the heat transfer per unit area. ANSWER MUST BE IN KW/m2A surface gains 500 W/m2 heat at an equilibrium temperature of 30 °C and it is subjected to a simultaneous heat loss to environment by convection and to surroundings by radiation. The convection conditions are 10 °C and 20 W/m2 K. If the surface assumed to be black what should be the surrounding temperature to sustain this physical condition?Define Stefan-Boltzmann Law and emissivity. Is there any surface whose emissivity value is greater than 1? If no, explain the reason.
- A 5-in-diameter spherical ball is known to emit radiation at a rate of 550 Btu/h when its surface temperature is 950 R. Determine the average emissivity of the ball at this temperature.An oil radiator has an outside surface area of 0.18 m2 and operates at a surface temperature of 85 degree Celsius. If the oil radiator behaves as a black body and the Stefan-Boltzmann constant value is equal to 5.67 X 10-8 W/(m²-K4), calculate the radiation heat flux at the surface of the radiator. O 0.53 W/m² O 2.96 W/m² O 167.64 W/m² O 931.35 W/m²Earth absorbs solar energy and radiates infrared energy. The intensity of the solar radiation incident on earth is J = 1350 Wm-2, also known as the solar constant. Assume earth’s surface (ground) temperature to be uniform at Ts, and that the ground and atmosphere are black (emissivity = 1) for infrared radiation. The radius of the earth is 6.378 x 106 m. The diagram shows the ground at the surface temperature Ts and the atmosphere, represented as a thin black layer, at temperature Ta . Suppose the atmosphere absorbs 100% of the infrared radiation emitted by the ground. Assume that the ground absorbs 47.5% of the incident solar energy, and that the atmosphere absorbs 17.5% of the incident solar energy (for a total of 65% absorbed by the planet). Calculate the "steady state” numerical values of the earth’s ground temperature Ts and the atmospheric temperature Ta taking into account the “greenhouse effect” of atmospheric infrared absorption and emission described above.