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 (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) ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer The concept of overall coefficient of heat transfer is used in case of heat transfer by Convection Conduction Conduction and convection Radiation Convection Conduction Conduction and convection Radiation ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer The heat of sun reaches to us according to Conduction None of these Convection Radiation Conduction None of these Convection Radiation 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 66.7°C 20°C 40°C 60°C 66.7°C 20°C 40°C 60°C ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer Upto the critical radius of insulation, Heat flux will decrease Added insulation will increase heat loss Added insulation will decrease heat loss Convective heat loss will be less than conductive heat loss Heat flux will decrease Added insulation will increase heat loss Added insulation will decrease heat loss Convective heat loss will be less than conductive heat loss ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer An electric cable of aluminium conductor (k = 240 W/mK) is to be insulated with rubber (k = 0.15 W/mK). The cable is to be located in air (h = 6 W/m²). The critical thickness of insulation will be 40 mm 800 mm 160 mm 25 mm 40 mm 800 mm 160 mm 25 mm ANSWER DOWNLOAD EXAMIANS APP
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