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 = (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) tm = loge (Δt1 - Δt2)/ Δt1/Δt2 tm = loge (Δt1/Δt2)/ (Δt1 - Δt2) tm = tm = (Δt1 - Δt2) loge (Δt1/Δt2) ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer Thermal conductivity of air with rise in temperature Remain constant Decreases Increases May increase or decrease depending on temperature Remain constant Decreases Increases May increase or decrease depending on temperature ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer Unit of thermal diffusivity is m²/hr m²/hr °C kcal/m. hr °C kcal/m² hr m²/hr m²/hr °C kcal/m. hr °C kcal/m² hr ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer The value of Prandtl number for air is about 0.3 0.1 0.7 1.7 0.3 0.1 0.7 1.7 ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer Planck’s law holds good for polished bodies black bodies all coloured bodies All of these polished bodies black bodies all coloured bodies All of these ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer Which of the following is a case of steady state heat transfer? None of these Air preheaters I.C. engine Heating of building in winter None of these Air preheaters I.C. engine Heating of building in winter ANSWER DOWNLOAD EXAMIANS APP
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