If a heat exchanger is designed to heat heavy fuel oil using steam as a heating medium, what statement is true?

Correct Answer: Option A — The heavy fuel oil gains sensible heat, and the steam loses latent heat.

When heating heavy fuel oil with steam, the oil gains sensible heat to reduce its viscosity. Simultaneously, the steam undergoes a phase change from vapor to liquid, releasing its latent heat of vaporization. This efficient energy transfer is standard practice for preparing fuel for injection in marine diesel engines.