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Consider the following statements: 1. Absorptivity depends on wave length of incident radiation waves 2. Emissivity is dependent on wave length of incident radiation waves Which of the above statements is/are correct?
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
Two large parallel planes with emissivity 0.4 are maintained at different temperatures and exchange heat only by radiation. What percentage change in net radiative heat transfer would occur if two equally large radiation shields with surface emissivity 0.04 are introduced in parallel to the plates?
If a black body at 1000 K and a gray body at 1250 K emit the same amount of radiation, what should be the emissivity of the gray body?
In a city 40% of the people have black hair, 25% have black eyes and 10% have both black hair and black eyes. What percentage of the people in the city has neither black hair nor black eyes?
In a certain city 40% of the people have black hair, 25% have black eyes and 10% have both black hair and black eyes. What percentage of the people in the city have neither black hair nor black eyes?
Absorptivity of a perfect black body is unity. Which of the following has maximum 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
Consider a deep-space probe constructed as 1 m diameter polished aluminum sphere. Estimate the equilibrium temperature that the probe reaches if the solar energy received is 300 W/m2. For solar radiation, absorptivity of aluminum is 0.3 and the average emissivity appropriate for aluminum at low temperature is 0.04
The grey body shape factor for radiant heat exchange between a small body (emissivity = 0.4) in a large enclosure (emissivity = 0.5) is