The Core Formula

Recovered power Q = m_dot x cp x DeltaT x effectiveness, where m_dot is mass flow (kg/s), cp for air is about 1.006 kJ/kg.K, and DeltaT is the temperature difference between streams.

Worked Example

For a 10,000 m3/h stream (density 1.2 kg/m3 -> 3.33 kg/s) at a 20 K difference with 70 percent effectiveness: Q = 3.33 x 1.006 x 20 x 0.70 is about 46 kW removed from the fresh-air heating load.

From Power to Size

• Choose target effectiveness from the device type
• Pick face velocity from the manufacturer's band
• Face area = airflow / face velocity; core volume follows from depth

Don't Forget

• Use part-load average airflow, not peak, for realistic savings
• Add the extra fan power from pressure drop to the energy balance
• Include frost-protection energy in cold climates

Tools

Use our sizing spreadsheet or an online calculator to vary inputs and watch payback change before you commit to a size.