If a heat exchanger is designed to cool lubricating oil using sea water as a cooling medium, what statement is true?

Correct Answer: Option B — The lubricating oil loses sensible heat, and the sea water gains sensible heat.

In a lube oil cooler, the oil loses sensible heat as its temperature drops, while the cooling sea water gains sensible heat as its temperature rises. No phase change occurs in either fluid; therefore, the energy transfer is strictly limited to sensible heat exchange between the two liquid mediums.