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 = loge (Δt1/Δt2)/ (Δt1 - Δt2) tm = tm = (Δt1 - Δt2) loge (Δt1/Δt2) tm = (Δt1 - Δt2)/ loge (Δt1/Δt2) tm = loge (Δt1 - Δt2)/ Δt1/Δt2 tm = loge (Δt1/Δt2)/ (Δt1 - Δt2) tm = tm = (Δt1 - Δt2) loge (Δt1/Δt2) tm = (Δt1 - Δt2)/ loge (Δt1/Δt2) ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer Thermal diffusivity of a substance is given by (where h = Thermal diffusivity, ρ = Density of substance, S = Specific heat, and k = Thermal conductivity) h = ρS/k h = kρ/S h = S/ρk h = k/ ρS h = ρS/k h = kρ/S h = S/ρk h = k/ ρS ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer Emissivity of a white polished body in comparison to a black body is Depends upon the shape of body Lower Higher Same Depends upon the shape of body Lower Higher Same 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 = 0 and a = 1 X = 0, a + p = 0 P = 0, x = 1 and a = 0 P= 1, T = 0 and a = 0 P = 0, x = 0 and a = 1 X = 0, a + p = 0 P = 0, x = 1 and a = 0 P= 1, T = 0 and a = 0 ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer Film coefficient is defined as Inside diameter of tube Film coefficient × Inside diameter Thermal conductivity Thermal conductivity Equivalent thickness of film Specific heat × Viscosity Equivalent thickness of film Thermal conductivity Molecular diffusivity of momentum Thermal diffusivity Film coefficient × Inside diameter Thermal conductivity Thermal conductivity Equivalent thickness of film Specific heat × Viscosity Equivalent thickness of film Thermal conductivity Molecular diffusivity of momentum Thermal diffusivity 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
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