Heat and Mass Transfer Depending on the radiating properties, a body will be black when(Where a = absorptivity, p = reflectivity, X = transmissivity.) X = 0, a + p = 0 P = 0, x = 1 and a = 0 P = 0, x = 0 and a = 1 P= 1, T = 0 and a = 0 X = 0, a + p = 0 P = 0, x = 1 and a = 0 P = 0, x = 0 and a = 1 P= 1, T = 0 and a = 0 ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer 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 800 mm 160 mm 40 mm 25 mm 800 mm 160 mm 40 mm 25 mm ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer According to Prevost theory of heat exchange All bodies above absolute zero emit radiation It is impossible to transfer heat from low temperature source to t high temperature source Heat transfer by radiation requires no medium Heat transfer in most of the cases takes place by combination of conduction, convection and radiation All bodies above absolute zero emit radiation It is impossible to transfer heat from low temperature source to t high temperature source Heat transfer by radiation requires no medium Heat transfer in most of the cases takes place by combination of conduction, convection and radiation ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer The thermal diffusivities for gases are generally More than those for solids Dependent on the viscosity Less than those for liquids More than those for liquids More than those for solids Dependent on the viscosity Less than those for liquids More than those for liquids ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer Kirchhoff's law states that The wave length corresponding to the maximum energy is proportional to the absolute temperature None of these The ratio of the emissive power and absorptive power of all bodies is the same and is equal to the emissive power of a perfectly black body The total radiation from a black body per second per unit area is directly proportional to the fourth power of the absolute temperature The wave length corresponding to the maximum energy is proportional to the absolute temperature None of these The ratio of the emissive power and absorptive power of all bodies is the same and is equal to the emissive power of a perfectly black body The total radiation from a black body per second per unit area is directly proportional to the fourth power of the absolute temperature ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer When α is absorptivity, ρ is reflectivity and τ is transmissivity, then for a diathermanous body, α + ρ = 1 and τ = 0 α = 1, ρ = 0 and τ = 0 α = 0, ρ = 0 and τ = 1 α = 0, ρ = 1 and τ = 0 α + ρ = 1 and τ = 0 α = 1, ρ = 0 and τ = 0 α = 0, ρ = 0 and τ = 1 α = 0, ρ = 1 and τ = 0 ANSWER DOWNLOAD EXAMIANS APP
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