Formula
Imperial Units:
$$\text{CFM} = 4005 \times \sqrt{\Delta P} \times A$$
Where:
- CFM is the airflow in cubic feet per minute (ft³/min)
- ΔP is the differential pressure in inches of water column (W.C.)
- A is the cross-sectional area in square feet (ft²)
Metric Units:
$$\text{CMM} = 195.5 \times \sqrt{\Delta P} \times A$$
Where:
- CMM is the airflow in cubic meters per minute (m³/min)
- ΔP is the differential pressure in Pascals (Pa)
- A is the cross-sectional area in square meters (m²)
Example Calculation
Given:
- Differential Pressure: 0.75 W.C.
- Cross-Sectional Area: 3.2 ft²
Calculation:
$$\text{CFM} = 4005 \times \sqrt{0.75} \times 3.2$$
$$\text{CFM} = 4005 \times 0.866 \times 3.2$$
$$\text{CFM} \approx 11{,}098.46$$
Result: The airflow is approximately 11,098 ft³/min.