Correctly sizing an air-to-air heat exchanger is mostly about matching airflow, recovery target and pressure drop to the space you have. Here is a field-tested workflow.
Step 1 — Fix the airflows
Start from the design ventilation or process airflow in m³/h (or CFM). For HVAC, this is the outdoor-air rate; for industry, the exhaust stream. Note both supply and exhaust rates—recovery is best when they are balanced.
Step 2 — Set the effectiveness target
Pick the effectiveness you need from the energy saving goal. Typical targets: 70% for general HVAC, 75%–85% for cold climates, 60%–70% for crossflow process duties. Higher effectiveness needs more core area (bigger unit, more fan power).
Step 3 — Choose flow arrangement & type
- Counterflow plate for highest effectiveness in separated streams.
- Crossflow plate when packaging is tight and ~65% is enough.
- Rotary wheel for very large airflows or enthalpy recovery.
- Heat pipe / run-around when streams are remote or contamination-sensitive.
See plate vs rotary and the industrial recovery guide for duty fit.
Step 4 — Estimate face velocity & pressure drop
Face velocity (m/s) sets both recovery and fan energy. A common band is 1.5–2.5 m/s for plates. Too fast → low recovery and high fan cost; too slow → oversized core. Confirm the resulting pressure drop fits the available fan head.
Step 5 — Handle frost & fouling
If exhaust can freeze, add preheat, by-pass or a wheel. If the air is dusty, specify filters and a cleanable core. Both protect effectiveness over time.
Quick checklist
- Airflow (supply = exhaust as close as possible)
- Target effectiveness & ΔT
- Type & arrangement chosen
- Face velocity & pressure drop within fan budget
- Frost strategy (cold climates)
- Access for cleaning
Send us the duty and we will size it
Share airflow (m³/h), inlet temperatures, climate and available dimensions. EN159 returns a sized plate, rotary or heat-pipe proposal with effectiveness and pressure drop.
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