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 = 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) ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer Two long parallel surfaces each of emissivity 0.7 are maintained at different temperatures and accordingly have radiation heat exchange between them. It is desired to reduce 75% of the radiant heat transfer by inserting thin parallel shields of emissivity 1 on both sides. The number of shields should be Three One Four Two Three One Four Two ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer Log mean temperature difference in case of counter flow compared to parallel flow will be Depends on other factors Less Same More Depends on other factors Less Same More ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer The emissivity for a black body is 0.75 0.5 1 0.75 0.5 1 ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer Thermal conductivity of wood depends on Temperature Density All of these Moisture Temperature Density All of these Moisture ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer In free convection heat transfer, Nusselt number is function of Prandtl number and Reynold number Grashoff number and Prandtl number Grashoff number and Reynold number Grashoff number, Prandtl number and Reynold number Prandtl number and Reynold number Grashoff number and Prandtl number Grashoff number and Reynold number Grashoff number, Prandtl number and Reynold number ANSWER DOWNLOAD EXAMIANS APP
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