Although it may be counter to our natural instincts, part of our job is to make a conscious effort to keep an open mind to new ideas that potentially could benefit a particular client. We have spent a lot of time over the past couple of years in this column analyzing the performance of the many different types of air-to-air heat recovery systems, including the runaround "rat race" coil, heat pipe, flat plate, and the desiccant rotary wheel. In this column, we'll take a look at a new (at least new to me) type of air-to-air heat recovery system. This is not a product endorsement, just an objective, general overview, and system comparison.
The manufacturer (bkm Engineered Interiors) refers to this system as a "reverse flow" system. Basically, the reverse flow system consists of two heat exchanger cassette banks and a two-position damper. The exhaust air and outside airstreams flow through the two individual cassettes. While the exhaust air is directed over one cassette, the other cassette is transferring energy to or from the incoming fresh air with the energy stored from the previous cycle. After a period of time (typically about a 70-sec cycle), the damper alternates and reverses the flow through the cassettes. Illustrations and schematics can be seen on the website at the end of this column.