Heat and Mass Transfer Thermal diffusivity is A physical property of the material Function of temperature A dimensionless parameter Used as mathematical model A physical property of the material Function of temperature A dimensionless parameter Used as mathematical model 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 = loge (Δt1 - Δt2)/ Δt1/Δt2 tm = tm = (Δt1 - Δt2) loge (Δt1/Δt2) tm = loge (Δt1/Δt2)/ (Δt1 - Δt2) tm = (Δt1 - Δt2)/ loge (Δt1/Δt2) tm = loge (Δt1 - Δt2)/ Δt1/Δt2 tm = tm = (Δt1 - Δt2) loge (Δt1/Δt2) ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer Fourier's law of heat conduction is valid for Two dimensional cases only Regular surfaces having non-uniform temperature gradients One dimensional cases only Three dimensional cases only Two dimensional cases only Regular surfaces having non-uniform temperature gradients One dimensional cases only Three dimensional cases only ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer The thermal diffusivities for solids are generally Less than those for liquids More or less same as for liquids and gases More than those for liquids and gases Less than those for gases Less than those for liquids More or less same as for liquids and gases More than those for liquids and gases Less than those for gases 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 25 mm 160 mm 800 mm 40 mm 25 mm 160 mm ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer The time constant of a thermocouple is The time taken to attain 50% of the value of initial temperature difference The time taken to attain 63.2% of the value of initial temperature difference Determined by the time taken to reach 100°C from 0°C The time taken to attain the final temperature to be measured The time taken to attain 50% of the value of initial temperature difference The time taken to attain 63.2% of the value of initial temperature difference Determined by the time taken to reach 100°C from 0°C The time taken to attain the final temperature to be measured ANSWER DOWNLOAD EXAMIANS APP
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