Heat and Mass Transfer Which of the following is the case of heat transfer by radiation? Heat received by a person from fireplace Blast furnace Heating of building Cooling of parts in furnace Heat received by a person from fireplace Blast furnace Heating of building Cooling of parts in furnace ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer Absorptivity of a body will be equal to its emissivity At all temperatures At one particular temperature When system is under thermal equilibrium At critical temperature At all temperatures At one particular temperature When system is under thermal equilibrium At critical temperature ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer The ratio of the emissive power and absorptive power of all bodies is the same and is equal to the emissive power of a perfectly black body. This statement is known as Kirchhoff's law Wien's law Stefan's law Planck's law Kirchhoff's law Wien's law Stefan's law Planck's law 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 40 mm 160 mm 25 mm 800 mm 40 mm 160 mm 25 mm 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 = [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) 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 Thermal conductivity of air with rise in temperature May increase or decrease depending on temperature Remain constant Increases Decreases May increase or decrease depending on temperature Remain constant Increases Decreases ANSWER DOWNLOAD EXAMIANS APP