Estimate the core area you need from one stream's airflow, a target effectiveness, face velocity and overall heat-transfer coefficient. Works for counterflow plate cores (Cr ≈ 1).
m³/h
m/s (1.5–3.5 typical)
%
W/m²K (plate ~20–35)
Required core area
0 m²
Face area
0 m²
Approx. core depth
0 m
NTU
0
The sizing chain
For counterflow with equal streams, NTU = ε / (1 − ε). Then NTU = UA / Cmin, so core area A = NTU × Cmin / U. Cmin = (airflow in m³/s) × 1.2 kg/m³ × 1005 J/kgK. Face area = volume flow / face velocity, and depth ≈ A / face area. Crossflow needs a larger area for the same effectiveness — add ~10–20%.
Frequently asked questions
Why does face velocity matter?
Higher velocity shrinks the unit but raises pressure drop and fan energy, and slightly lowers effectiveness. 2–3 m/s is the usual sweet spot for plate cores.
Should I use this for rotary wheels?
The same NTU logic applies, but wheels also have carryover and moisture migration. Treat the result as a first estimate and confirm with the supplier's selection software.