Heat and Mass Transfer Unit of thermal conductivity in S.I. units is J/m² sec Option (B) and (C) above J/m °K sec W/m °K J/m² sec Option (B) and (C) above J/m °K sec W/m °K ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer If the temperature of a solid surface changes form 27°C to 627°C, then its emissive power changes in the ratio of 3 9 270 81 3 9 270 81 ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer The logarithmic mean temperature difference (tm) is given by (where Δt1 and Δt2 are temperature differences between the hot and cold fluids at entrance and exit) tm = loge (Δt1/Δt2)/ (Δt1 - Δt2) tm = (Δt1 - Δt2)/ loge (Δt1/Δt2) tm = tm = (Δt1 - Δt2) loge (Δt1/Δt2) tm = loge (Δt1 - Δt2)/ Δt1/Δt2 tm = loge (Δt1/Δt2)/ (Δt1 - Δt2) tm = (Δt1 - Δt2)/ loge (Δt1/Δt2) tm = tm = (Δt1 - Δt2) loge (Δt1/Δt2) tm = loge (Δt1 - Δt2)/ Δt1/Δt2 ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer Fourier's law of heat conduction is (where Q = Amount of heat flow through the body in unit time, A = Surface area of heat flow, taken at right angles to the direction of heat flow, dT = Temperature difference on the two faces of the body, dx = Thickness of the body, through which the heat flows, taken along the direction of heat flow, and k = Thermal conductivity of the body) (dx/dT) k. (dx/dT) (dT/dx) k. (dT/dx) k. k. (dx/dT) k. (dx/dT) (dT/dx) k. (dT/dx) k. k. ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer Reynolds number (RN) is given by (where h = Film coefficient, l = Linear dimension, V = Velocity of fluid, k = Thermal conductivity, t = Temperature, ρ = Density of fluid, cp = Specific heat at constant pressure, and μ = Coefficient of absolute viscosity) RN = hl/k RN = μ cp/k RN = ρ V l /μ RN = V²/t.cp RN = hl/k RN = μ cp/k RN = ρ V l /μ RN = V²/t.cp ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer According to Prevost theory of heat exchange All bodies above absolute zero emit radiation Heat transfer in most of the cases takes place by combination of conduction, convection and radiation It is impossible to transfer heat from low temperature source to t high temperature source Heat transfer by radiation requires no medium All bodies above absolute zero emit radiation Heat transfer in most of the cases takes place by combination of conduction, convection and radiation It is impossible to transfer heat from low temperature source to t high temperature source Heat transfer by radiation requires no medium ANSWER DOWNLOAD EXAMIANS APP
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