Steam Boilers, Engines, Nozzles and Turbines
In designing air preheaters, the important design consideration is that

Heat transfer area should be optimum
Handling and maintenance should be easier
Approach temperature should be as low as possible
Stack gases should not be cooled to the dew point

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Steam Boilers, Engines, Nozzles and Turbines
The effect of friction on the flow of steam through a nozzle is to

Increase the exit temperature without any effect on mass flow rate
Decrease the mass flow rate and to decrease the wetness of steam
Decrease the mass flow rate and to increase the wetness of steam
Increase the mass flow rate and to increase the exit temperature

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