Heat and Mass Transfer The ratio of the thickness of thermal boundary layer to the thickness of hydrodynamic boundary layer is equal to (Prandtl number) n, where n is equal to -1 =-1/3 =-2/3 1 -1 =-1/3 =-2/3 1 ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer Total heat is the heat required to Change vapour into liquid Convert water into steam and superheat it Change liquid into vapour Increase the temperature of a liquid or vapour Change vapour into liquid Convert water into steam and superheat it Change liquid into vapour Increase the temperature of a liquid or vapour 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) (dT/dx) k. k. (dT/dx) k. (dx/dT) k. (dx/dT) (dT/dx) k. k. (dT/dx) k. (dx/dT) k. (dx/dT) ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer The time constant of a thermocouple is The time taken to attain 63.2% of the value of initial temperature difference The time taken to attain 50% of the value of initial temperature difference The time taken to attain the final temperature to be measured Determined by the time taken to reach 100°C from 0°C The time taken to attain 63.2% of the value of initial temperature difference The time taken to attain 50% of the value of initial temperature difference The time taken to attain the final temperature to be measured Determined by the time taken to reach 100°C from 0°C ANSWER DOWNLOAD EXAMIANS APP
Heat and Mass Transfer The value of the wave length for maximum emissive power is given by Wine’s law Stefan’s law Planck’s law Kirchhoff’s law Wine’s law Stefan’s law Planck’s law Kirchhoff’s law 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 Four Two Three One Four Two Three One ANSWER DOWNLOAD EXAMIANS APP
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