EXAMIANS
An electric cable of aluminium conductor (k = 240 W/mK) is to be insulated with rubber (k = 0.15 W/mK). The cable is to be located in air (h = 6 W/m²). The critical thickness of insulation will be
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The thermal diffusivities for gases are generally
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According to Stefan Boltzmann law, the total radiation from a black body per second per unit area is directly proportional to the
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A non-dimensional number generally associated with natural convection heat transfer is
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Which of the following is the case of heat transfer by radiation?
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According to Kirchoff's law, the ratio of emissive power to absorptivity for all bodies is equal to the emissive power of a
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Total emissivity of polished silver compared to black body is
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The unit of overall coefficient of heat transfer is
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Thermal diffusivity of a substance is given by (where h = Thermal diffusivity, ρ = Density of substance, S = Specific heat, and k = Thermal conductivity)
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Fourier's law of heat conduction is (where Q = Amount of heat flow through the body in unit time, A = Surface area of heat flow, taken at right angles to the direction of heat flow, dT = Temperature difference on the two faces of the body, dx = Thickness of the body, through which the heat flows, taken along the direction of heat flow, and k = Thermal conductivity of the body)
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