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
Stack gases should not be cooled to the dew point
Approach temperature should be as low as possible

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Steam Boilers, Engines, Nozzles and Turbines
Boiler H.P. is defined as the

Work done in evaporating 1 kg of steam per hour from and at 100°C into dry saturated steam
Work done by 1 kg of steam at saturation condition
The evaporation of 15.65 kg of water per hour from and at 100°C into dry saturated steam
Steam evaporation rate per kg of fuel fired

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