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

Handling and maintenance should be easier
Heat transfer area should be optimum
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
In a reaction turbine

The expansion of steam takes place partly in the fixed blades and partly in the moving blades
The pressure and temperature of steam remains constant
The steam is expanded from a high pressure to a condenser pressure in one or more nozzles
The steam is allowed to expand in the nozzle, where it gives a high velocity before it enters the moving blades

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