Which statement accurately defines a heat exchanger?

• A. Any piece of equipment that transfers heat from one material to another.
• B. A device that stores heat indefinitely.
• C. A pump that circulates coolant without exchanging heat.
• D. An instrument that measures heat flux.

Answer: (A)

A heat exchanger is defined by its function: it moves thermal energy from one stream to another while keeping the streams separate. This transfer typically happens through a solid barrier so the two materials don’t mix, and it occurs in devices like radiators, condensers, and evaporators where hot fluid gives up heat to a cooler one. That core idea—that heat moves from a hotter medium to a cooler one, across a barrier—is what makes the first statement the best fit. It's not about storing heat, circulating without heat transfer, or measuring heat flux, which describe different equipment.