The absolute pressure maintained in the shell of the salt water feed heater on most flash evaporators used on steam propelled vessels is __________.

Correct Answer: Option B — slightly less than the absolute pressure of the L.P. extraction

Flash evaporators utilize low-pressure extraction steam to heat the feed water. The shell pressure of the feed heater must be maintained slightly below the absolute pressure of the L.P. extraction steam to ensure a continuous flow of heat energy into the feed water for effective flashing.