Heat and Mass Transfer 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 Newton's law of cooling First law of thermodynamics Stefan's law Newton's law of heating Newton's law of cooling First law of thermodynamics Stefan's law Newton's law of heating ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer Reynolds number is the ratio of Kinematic viscosity to thermal diffusivity None of these Inertia force to viscous force Energy transferred by convection to that by conduction Kinematic viscosity to thermal diffusivity None of these Inertia force to viscous force Energy transferred by convection to that by conduction ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer Which of the following would lead to a reduction in thermal resistance? In conduction, reduction in the thickness of the material and an increase in thermal conductivity. In radiation, increasing the temperature and reducing the emissivity. In convection, stirring of the fluid and cleaning the heating surface. All of these In conduction, reduction in the thickness of the material and an increase in thermal conductivity. In radiation, increasing the temperature and reducing the emissivity. In convection, stirring of the fluid and cleaning the heating surface. All of these ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer Fouling factor is used When a liquid exchanges heat with a gas In case of Newtonian fluids In heat exchanger design as a safety factor None of these When a liquid exchanges heat with a gas In case of Newtonian fluids In heat exchanger design as a safety factor None of these 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 = [2π (T₁ - T₂)]/2.3 lk log (r₂/r₁) Q = = 2πlk/2.3 (T₁ - T₂) log (r₂/r₁) Q = 2.3 log (r₂/r₁)/[2πlk (T₁ - T₂)] Q = [2πlk (T₁ - T₂)]/2.3 log (r₂/r₁) Q = [2π (T₁ - T₂)]/2.3 lk log (r₂/r₁) Q = = 2πlk/2.3 (T₁ - T₂) log (r₂/r₁) Q = 2.3 log (r₂/r₁)/[2πlk (T₁ - T₂)] Q = [2πlk (T₁ - T₂)]/2.3 log (r₂/r₁) ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer A cube at high temperature is immersed in a constant temperature bath. It loses heat from its top, bottom and side surfaces with heat transfer coefficients of h₁, h₂ and h₃ respectively. The average heat transfer coefficient for the cube is None of these (h₁.h₂.h₃)1/3 1/h₁ + 1/h₂ + 1/h₃ h₁ + h₂ + h₃ None of these (h₁.h₂.h₃)1/3 1/h₁ + 1/h₂ + 1/h₃ h₁ + h₂ + h₃ ANSWER DOWNLOAD EXAMIANS APP
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