Heat and Mass Transfer
A heat exchanger with heat transfer surface area A and overall heat transfer coefficient U handles two fluids of heat capacities Cmax and Cmin. The number of transfer units (NTU) used in the analysis of heat exchanger is specified as

U/A.Cmin
U/Cmin
U.Cmin
Cmin/U

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Heat and Mass Transfer
Which of the following would lead to a reduction in thermal resistance?

All of these
In convection, stirring of the fluid and cleaning the heating surface.
In radiation, increasing the temperature and reducing the emissivity.
In conduction, reduction in the thickness of the material and an increase in thermal conductivity.

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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 the final temperature to be measured
Determined by the time taken to reach 100°C from 0°C
The time taken to attain 50% of the value of initial temperature difference

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