A rotary heat exchanger, or thermal wheel, is a slowly rotating disc of heat-absorbing media. As it turns, it picks up heat (and, with enthalpy wheels, moisture) from the exhaust, then releases it to the incoming supply air. A small seal divides the two streams.
Strengths
- Compact at high airflow: a wheel handles large volumes in a small footprint, why it dominates big commercial air handlers.
- Enthalpy recovery: desiccant-coated wheels move both heat and humidity.
- Built-in frost control: the warm wheel melts frost as it rotates.
Weaknesses
- Carryover: a small fraction of exhaust (and any moisture) leaks to supply past the seal.
- Moving parts: motor, belt and seals need service.
- Pressure drop: seals and the matrix add resistance.
| Metric | Typical |
|---|---|
| Effectiveness | 70% to 85% |
| Carryover | 0.5% to 2% (sealed wheel) |
| Best airflow | Very large (commercial / industrial) |
Best-fit duties
Use a wheel for large commercial HVAC, swimming-pool ventilation and any duty where footprint is tight and slight carryover is acceptable. Avoid it for mines, pharma and clean exhaust where separation is mandatory, see plate vs rotary and heat pipes.
Specifying a unit for your project?
EN159 builds plate, rotary, heat-pipe and counterflow air-to-air exchangers. Send airflow (m3/h), inlet temperatures and available space and we will size it.
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