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 = = 2πlk/2.3 (T₁ - T₂) log (r₂/r₁) Q = 2.3 log (r₂/r₁)/[2πlk (T₁ - T₂)] Q = [2π (T₁ - T₂)]/2.3 lk log (r₂/r₁) Q = [2πlk (T₁ - T₂)]/2.3 log (r₂/r₁) Q = = 2πlk/2.3 (T₁ - T₂) log (r₂/r₁) Q = 2.3 log (r₂/r₁)/[2πlk (T₁ - T₂)] Q = [2π (T₁ - T₂)]/2.3 lk log (r₂/r₁) 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 800 mm 160 mm 25 mm 40 mm 800 mm 160 mm 25 mm 40 mm ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer The unit of Stefan Boltzmann constant is watt/cm2 °K⁴ watt2/cm °K⁴ watt/cm4 °K watt/cm3 °K watt/cm2 °K⁴ watt2/cm °K⁴ watt/cm4 °K watt/cm3 °K ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer Depending on the radiating properties, a body will be black when(Where a = absorptivity, p = reflectivity, X = transmissivity.) P = 0, x = 1 and a = 0 P = 0, x = 0 and a = 1 X = 0, a + p = 0 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 = 0 P= 1, T = 0 and a = 0 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 Parallel flow Cross flow All of these Counter flow Parallel flow Cross flow All of these Counter flow ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer Fourier's law of heat conduction gives the heat flow for Irregular surfaces One dimensional cases only Two dimensional cases only Nonuniform temperature surfaces Irregular surfaces One dimensional cases only Two dimensional cases only Nonuniform temperature surfaces ANSWER DOWNLOAD EXAMIANS APP