Rotary heat exchangers (heat wheels) are designed to provide either sensible or total energy exchange between two airstreams. Rotary heat exchangers are normally designed for counterflow application and operate on the principle of sensible heat transfer and latent energy transfer using desiccant material. The contruction of the rotor is like a honeycomb, with passages through which the air flows, either gaining energy from or losing energy to the mass of the matrix.

In the KyotoCooling situation, the heat wheel is “Plumbed Wrong” and therefore works as a cooling machine. The inside heat from the IT room is still removed via the heat wheel, but there is minimal air transfer between the ambient and the computer room. This system has all the benefits of Airside Economizing, without the exposures of airside economizing like contamination and humidity control.