What is the function of item 'D' shown in the illustration? Illustration MO-0110

Correct Answer: Option A — It heats the entering feed water.

The feed water heater utilizes jacket water heat to raise the temperature of incoming seawater before it enters the flash chamber. This preheating is critical, as it ensures the feed water possesses sufficient thermal energy to flash into vapor immediately upon entering the lower-pressure environment of the flash chamber.