Heat and Mass Transfer Absorptivity of a body will be equal to its emissivity When system is under thermal equilibrium At one particular temperature At all temperatures At critical temperature When system is under thermal equilibrium At one particular temperature At all temperatures At critical temperature ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer The heat transfer takes place according to Zeroth law of thermodynamics First law of thermodynamics Kirchhoff's law Second law of thermodynamics Zeroth law of thermodynamics First law of thermodynamics Kirchhoff's law Second law of thermodynamics ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer The ratio of the thickness of thermal boundary layer to the thickness of hydrodynamic boundary layer is equal to (Prandtl number) n, where n is equal to -1 1 =-2/3 =-1/3 -1 1 =-2/3 =-1/3 ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer Thermal diffusivity is A dimensionless parameter Function of temperature A physical property of the material Used as mathematical model A dimensionless parameter Function of temperature A physical property of the material Used as mathematical model ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer In a heat exchanger with one fluid evaporating or condensing, the surface area required is least in Counter flow Parallel flow All of these Cross flow Counter flow Parallel flow All of these Cross flow ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer The heat transfer by conduction through a thick cylinder (Q) is given by (where T₁ = Higher temperature, T₂ = Lower temperature, r₁ = Inside radius, r₂ = Outside radius, l = Length of cylinder, and k = Thermal conductivity) Q = [2πlk (T₁ - T₂)]/2.3 log (r₂/r₁) Q = [2π (T₁ - T₂)]/2.3 lk log (r₂/r₁) Q = 2.3 log (r₂/r₁)/[2πlk (T₁ - T₂)] Q = = 2πlk/2.3 (T₁ - T₂) log (r₂/r₁) Q = [2πlk (T₁ - T₂)]/2.3 log (r₂/r₁) Q = [2π (T₁ - T₂)]/2.3 lk log (r₂/r₁) Q = 2.3 log (r₂/r₁)/[2πlk (T₁ - T₂)] Q = = 2πlk/2.3 (T₁ - T₂) log (r₂/r₁) ANSWER DOWNLOAD EXAMIANS APP
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