Formula
$$P_{\text{static}} = P_{\text{total}} - \left(\frac{Q}{A \times 4005}\right)^{2}$$
Where:
- P_static is the static pressure
- P_total is the total pressure
- Q is the airflow in CFM
- A is the cross-sectional area
- 4005 is the conversion factor for imperial units (1524.038 for metric)
Example
Given:
- Total Pressure = 250 lbf/ft²
- CFM = 80
- Area = 5 ft²
Calculation:
$$P_{\text{static}} = 250 - \left(\frac{80}{5 \times 4005}\right)^{2}$$
$$P_{\text{static}} = 250 - \left(\frac{80}{20025}\right)^{2}$$
$$P_{\text{static}} = 250 - (0.003996)^{2}$$
$$P_{\text{static}} \approx 249.999984 \text{ lbf/ft}^{2}$$
The static pressure is approximately 249.999984 lbf/ft².