Unit of thermal diffusivity is
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Mechanical Engineering · all questionsHeat And Mass Transfer
Heat And Mass Transfer
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Temperature of steam at around 540°C can be measured by
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The total radiation from a black body per second per unit area is ________ fourth power of the absolute temperature. This statement is known as Stefan Boltzmann law.
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The use of heat exchangers is made in
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The heat transfer from a hot body to a cold body is directly proportional to the surface area and difference of temperatures between the two bodies. This statement is called
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Which of the following statement is wrong?
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When α is absorptivity, ρ is reflectivity and τ is transmissivity, then for a diathermanous body,
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Planck’s law holds good for
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Thermal conductivity of a material may be defined as the
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A perfect black body is one which
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Film coefficient is defined as the ratio of
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The highest thermal diffusivity is of
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The rate of energy transferred by convection to that by conduction is called
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Thermal conductivity of water _________ with rise in temperature.
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Which of the following property of air does not increase with rise in temperature?
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Two balls of same material and finish have their diameters in the ratio of 2 : 1 and both are heated to same temperature and allowed to cool by radiation. Rate of cooling by big ball as compared to smaller one will be in the ratio of
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Thermal conductivity of glass wool varies from sample to sample because of variation in
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Two plates spaced 150 mm apart are maintained at 1000°C and 70°C. The heat transfer will take place mainly by
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According to Stefan Boltzmann law, ideal radiators emit radiant energy at a rate proportional to
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The critical radius is the insulation radius at which the resistance to heat flow is
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