Q. 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.

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Q. A blind cylindrical hole of 2 cm diameter and 3 cm length is drilled into a metal slab having emissivity 0.7. If the metal slab is maintained at 650 K, make calculations for the radiation heat escape from the hole

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Q. 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?

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Q. Consider radiant heat exchange between two non-black parallel surfaces. The surface 1 emits radiant energy E 1 which strikes the surface 2. Identify the correct option

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Q. Find the shape factor F 12 for the arrangement shown in the figure. The areas A 1 and A 2 are perpendicular but do not share the common edge

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Q. The energy radiated out decreases with increases in α and becomes zero at an angle of

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Q. A black body of 0.2 m² area has an effective temperature of 800 K. Calculate the intensity of normal radiations

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Q. The total emissive power of the emitter with area d A and temperature T is given by

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Q. 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

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Q. A small surface emits diffusively, and measurements indicate that the total intensity associated with emission in the normal direction I n = 6500 W/square m sr. The emitted radiation is intercepted by three surfaces. Mark calculations for intensity associated with emission

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Q. The intensity of normal radiation In is how much times the emissive power?

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Q. If I n denotes the normal intensity and I α represents the intensity at angle α, then

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Q. When the incident surface is a sphere, the projection of surface normal to the line of propagation is the silhouette disk of the sphere which is a circle of the diameter of

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Q. The plane angle is defined by a region by the rays of a circle, and is measured as

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Q. The solid angle is defined by a region by the rays of a sphere, and is measured as

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Q. Consider two surfaces, one absolutely black and the other non-black. These surfaces are arranged parallel to each other and so close that the radiation of one falls totally on the other. Choose the correct option

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Q. In the given diagram let r be the length of the line of propagation between the radiating and the incident surfaces. What is the value of solid angle W?

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Q. Consider a system of concentric spheres of radius r 1 and r 2 (r 2 is greater than r 1). If r 1 = 5 cm, determine the radius r 2 if it is desired to have the value of shape factor F 21 equal to 0.6

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Q. What is the shape factor for a hemispherical bowl with respect to itself of diameter d? The cavity is closed on its outer surface with a flat plate

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Q. Establish a relation for shape factor for a conical cavity with respect to itself of depth h and diameter d. The cavity is closed on its outer surface with a flat plate

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