Air Flow Calculator from Differential Pressure

Air Flow Formula:

\[ Q = C \times A \times \sqrt{\frac{2 \times \Delta P}{\rho}} \]

Discharge Coefficient (C):

Orifice Area (A):

m²

Differential Pressure (ΔP):

Air Density (ρ):

kg/m³

Air Flow Rate (Q):

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1. What is an Air Flow Calculator from Differential Pressure?

Definition: This calculator estimates the volumetric flow rate of air through an orifice based on the measured pressure difference across the orifice.

Purpose: It helps engineers and technicians in HVAC systems, pneumatic controls, and industrial processes to determine air flow rates.

2. How Does the Calculator Work?

The calculator uses the orifice flow equation:

\[ Q = C \times A \times \sqrt{\frac{2 \times \Delta P}{\rho}} \]

Where:

\( Q \) — Volumetric flow rate (m³/s)
\( C \) — Discharge coefficient (dimensionless, typically 0.6-0.65)
\( A \) — Cross-sectional area of the orifice (m²)
\( \Delta P \) — Differential pressure across orifice (Pa)
\( \rho \) — Density of air (kg/m³, typically 1.225 at sea level)

Explanation: The flow rate is proportional to the square root of the pressure difference and inversely proportional to the square root of the air density.

3. Importance of Air Flow Calculation

Details: Accurate air flow measurement is critical for system design, energy efficiency, and process control in ventilation, compressed air systems, and industrial applications.

4. Using the Calculator

Tips:

Enter the discharge coefficient (default 0.62 for sharp-edged orifices)
Provide the orifice area in square meters
Input the measured pressure difference in Pascals
Specify air density (default 1.225 kg/m³ for standard conditions)

All values must be greater than 0.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical discharge coefficient value?
A: For sharp-edged orifices, 0.62 is common. For rounded orifices, it may approach 0.98.

Q2: How do I measure differential pressure?
A: Use a manometer or differential pressure transducer across the orifice plate.

Q3: Does temperature affect the calculation?
A: Yes, indirectly through air density (ρ). Warmer air is less dense, resulting in higher flow for the same ΔP.

Q4: Can I use this for liquids?
A: Yes, but ensure you use the correct density and that the liquid is incompressible.

Q5: How accurate is this calculation?
A: Accuracy depends on correct coefficient selection and proper installation. Typically ±2-5% with careful measurement.