How to Read a Heat Exchanger Datasheet

A datasheet is only useful if you read it at your conditions, not the vendor's favourite ones. Here is what each block means and where suppliers quietly hide the compromises.

1. Effectiveness curve (not the headline number)

The big percentage is almost always at the lowest face velocity. Effectiveness falls as face velocity rises, so read the curve at your actual airflow. If only a single number is given, ask for the curve — or estimate with the ε-NTU tool.

2. Face velocity and airflow

Given in m/s or m³/h (convert with our CFM tool). Confirm the rated velocity matches your fan's deliverable; a core rated at 1.5 m/s but run at 3 m/s will under-perform.

3. Pressure drop (ΔP)

Listed per stream, usually in Pa. This is what your fan must overcome — and fan energy scales with it. Compare ΔP at equal effectiveness, not equal size. See pressure drop & fan energy.

4. NTU or UA

Some datasheets state NTU or UA (W/K). NTU = UA/C_min is the honest size metric; two cores with the same effectiveness but different NTU simply run at different velocities. Our sizing tool works backwards from NTU to area.

5. Dimensions and weight

Core area, depth and weight set the casing and the installation envelope. Remember depth ≈ area / face area.

6. Material and cleanability

Aluminium, stainless, polymer or coated — each suits a different exhaust. Grease or corrosive streams need a washable or coated core (see materials).

7. Certification and test condition

AHRI/Eurovent/CE — and the exact temperature, humidity and velocity at which rated. Certified at 2 m/s but you run 3.5 m/s? De-rate accordingly. Our certifications guide explains the marks.

8. Operating limits

Max temperature, max pressure, frost limit, cleanable yes/no. The frost limit decides whether you need frost control — check it against your coldest exhaust with the frost tool.

Traps to avoid

• Single-point rating: always ask for the curve.
• Effectiveness without ΔP: a high number at huge fan cost is not a win.
• “Up to” language: “up to 90%” is the best case, not yours.
• Unstated humidity: enthalpy (ERV) ratings need the humidity condition spelled out.