Which statement best describes a heat exchanger?

• A. It is equipment that transfers heat from one material to another
• B. It stores heat for later use
• C. It measures heat content
• D. It cools liquids only

Answer: (A)

A heat exchanger is a device whose function is to move energy as heat from one stream to another while keeping the two streams separate. The two materials exchange heat across a barrier, so they don’t mix. This lets one stream be heated while the other is cooled, or enables heat recovery from one stream to preheat another. It can involve liquids, gases, or combinations, and may handle phase changes, but the defining idea is transferring heat between materials, not storing it or measuring it, and not being limited to cooling liquids only. So the best description is that it is equipment that transfers heat from one material to another.