An air-to-air heat recovery device transfers heat or enthalpy between two air streams, resulting in energy savings from reduced heating (or cooling) requirements.
A thermosiphon tube exchanger is a sealed system air-to-air heat recovery device that consist of an evaporator, a condenser, interconnecting piping, and an intermediate working fluid that is present in both liquid and vapor phases where the evaporator and the condenser are usually at opposite ends of a bundle of straight, individual thermosiphon tubes and the exhaust and supply ducts are adjacent to each other.