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Consider an enclosure formed by three surfaces having the following values of shape factors, emissivities and temperatures Surface 1 i.e. curved cylindrical has an emissivity 0.75 and temperature 800 K Surface 2 i.e. closing disc has an emissivity 0.8 and temperature 700 K Surface 3 i.e. closing disc has an emissivity 0.8 and temperature 700 K The closing flat discs are 25 mm in diameter and they have interspacing distance equal to 100 mm. If the shape factor between these two identical discs is 0.05, calculate the net rate of radiant heat flow from the curve surface to each of the closing end surface
Absorptivity of a body will be equal to its emissivity
Absorptivity of a body is equal to its emissivity
The grey body shape factor for radiant heat exchange between a small body (emissivity = 0.4) in a large enclosure (emissivity = 0.5) is
Absorptivity of a perfect black body is unity. Which of the following has maximum absorptivity?
In thermal radiation for a black body (where, ε is emissivity and α is absorptivity)
The emissivity and the absorptivity of a real surface are equal for radiation with identical temperature and wavelength. This law is referred to as
In which of the following case we can surely say that the body A is charged: a) When a positively charged body is kept near to body A and it gets attracted b) When a negatively charged body is kept near to body A and it gets  attracted c) When a positively charged body is kept near to body A and it gets repelled
Two long parallel surfaces, each of emissivity 0.7 are at different temperatures and accordingly have radiation exchange between them. It is desired to reduce 75% of this radiant heat transfer by inserting thin parallel shields of equal emissivity 0.7 on both sides. What should be the number of shields?
Measurements were made of the monochromatic absorptivity and monochromatic hemispherical irradiation incident on an opaque surface, and the variation of these parameters with wavelength may be approximated by the result shown below. Determine the total hemispherical absorptivity