Heat and Mass Transfer Absorptivity of a body will be equal to its emissivity At critical temperature At all temperatures When system is under thermal equilibrium At one particular temperature At critical temperature At all temperatures When system is under thermal equilibrium At one particular temperature ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer Which of the following property of air does not increase with rise in temperature? Thermal diffusivity Dynamic viscosity Thermal conductivity Density Thermal diffusivity Dynamic viscosity Thermal conductivity Density ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer The logarithmic mean temperature difference (tm) is given by (where Δt1 and Δt2 are temperature differences between the hot and cold fluids at entrance and exit) tm = loge (Δt1 - Δt2)/ Δt1/Δt2 tm = (Δt1 - Δt2)/ loge (Δt1/Δt2) tm = loge (Δt1/Δt2)/ (Δt1 - Δt2) tm = tm = (Δt1 - Δt2) loge (Δt1/Δt2) tm = loge (Δt1 - Δt2)/ Δt1/Δt2 tm = (Δt1 - Δt2)/ loge (Δt1/Δt2) tm = loge (Δt1/Δt2)/ (Δt1 - Δt2) tm = tm = (Δt1 - Δt2) loge (Δt1/Δt2) ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer The critical thickness of insulation for a sphere is k/h₀ h₀/2k 2k/h₀ h₀/k k/h₀ h₀/2k 2k/h₀ h₀/k ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer Thermal conductivity of solid metals with rise in temperature normally Increases Remain constant May increase or decrease depending on temperature Decreases Increases Remain constant May increase or decrease depending on temperature Decreases ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer Wien’s law states that the wave length corresponding to ________ is proportional to the absolute temperature. None of these Minimum energy Maximum energy Both (A) and (B) None of these Minimum energy Maximum energy Both (A) and (B) ANSWER DOWNLOAD EXAMIANS APP
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