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

ANSWER DOWNLOAD EXAMIANS APP

Steam Boilers, Engines, Nozzles and Turbines
For water, at pressures below atmospheric;

Melting point drops slightly and boiling point drops slightly
Melting point drops slightly and boiling point drops markedly
Melting point rises markedly and boiling point drops markedly
Melting point rises slightly and boiling point drops markedly

ANSWER DOWNLOAD EXAMIANS APP