Plate heat exchangers (or recuperators)
These products comprise a heat exchanger with alternate channels for the supply and exhaust airflows that are separated by plates through which heat is conducted. They must not contain any moving parts. This category includes both cross-flow type, and counter-current flow type, plate heat exchangers. The product may be designed to recover only sensible heat, or it may incorporate a specialist material (such as treated paper or a polymeric membrane) to enable it to recover both latent and sensible heat.
Rotating heat exchangers (including thermal and desiccant heat wheels)
These products must consist of a circular heat transfer medium (or ‘wheel’) that is designed to slowly rotate within an airtight container, and to pass the exhaust air stream over one section of the wheel, and the supply air stream over the other section of the wheel in counter flow direction. The product may be designed to recover only sensible heat, or it may incorporate a desiccant material to enable it to recover both latent and sensible heat.More information (PDF)