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 = 2.3 log (r₂/r₁)/[2πlk (T₁ - T₂)] Q = = 2πlk/2.3 (T₁ - T₂) log (r₂/r₁) Q = [2π (T₁ - T₂)]/2.3 lk log (r₂/r₁) Q = [2πlk (T₁ - T₂)]/2.3 log (r₂/r₁) Q = 2.3 log (r₂/r₁)/[2πlk (T₁ - T₂)] Q = = 2πlk/2.3 (T₁ - T₂) log (r₂/r₁) Q = [2π (T₁ - T₂)]/2.3 lk log (r₂/r₁) ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer The total radiation from a black body per second per unit area is ________ fourth power of the absolute temperature. This statement is known as Stefan Boltzmann law. None of these Inversely proportional to Directly proportional to Equal to None of these Inversely proportional to Directly proportional to Equal to ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer A designer chooses the values of fluid flow rates and specific heats in such a manner that the heat capacities of the two fluids are equal. A hot fluid enters the counter flow heat exchanger at 100°C and leaves at 60°C. A cold fluid enters the heat exchanger at 40°C. The mean temperature difference between the two fluids is 40°C 60°C 20°C 66.7°C 40°C 60°C 20°C 66.7°C ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer Depending on the radiating properties, a body will be white when(Where a = absorptivity, p = reflectivity, x = transmissivity) X = 0, a + p = 1 P=1, T = 0 and a = 0 P = 0, x = 1 and a = 0 P = 0, x = 0 and a = 1 X = 0, a + p = 1 P=1, T = 0 and a = 0 P = 0, x = 1 and a = 0 P = 0, x = 0 and a = 1 ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer The emissivity for a black body is 0.5 1 0.75 0.5 1 0.75 ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer A grey body is one whose absorptivity Does not vary with temperature and. wavelength of the incident ray Varies with wavelength of the incident ray Varies with temperature Is equal to its emissivity Does not vary with temperature and. wavelength of the incident ray Varies with wavelength of the incident ray Varies with temperature Is equal to its emissivity ANSWER DOWNLOAD EXAMIANS APP
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