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. All of these In convection, stirring of the fluid and cleaning the heating surface. In radiation, increasing the temperature and reducing the emissivity. In conduction, reduction in the thickness of the material and an increase in thermal conductivity. All of these In convection, stirring of the fluid and cleaning the heating surface. In radiation, increasing the temperature and reducing the emissivity. 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 = 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) Q = [2πlk (T₁ - T₂)]/2.3 log (r₂/r₁) Q = [2π (T₁ - T₂)]/2.3 lk log (r₂/r₁) ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer The value of the wave length for maximum emissive power is given by Wine’s law Planck’s law Kirchhoff’s law Stefan’s law Wine’s law Planck’s law Kirchhoff’s law Stefan’s law ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer The automobile radiator is a heat exchanger of Regenerator type Cross flow type Counter flow type Parallel flow type Regenerator type Cross flow type Counter flow type Parallel flow type ANSWER DOWNLOAD EXAMIANS APP
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 Newton's law of heating First law of thermodynamics Stefan's law Newton's law of cooling Newton's law of heating First law of thermodynamics Stefan's law ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer In convection heat transfer from hot flue gases to water tube, even though flow may be turbulent, a laminar flow region (boundary layer of film) exists close to the tube. The heat transfer through this film takes place by Both convection and conduction Conduction Convection Radiation Both convection and conduction Conduction Convection Radiation ANSWER DOWNLOAD EXAMIANS APP
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