Air Flow Through an Orifice Calculator CFM

Air Flow Formula:

\[ Q_{cfm} = C_d \times A \times \sqrt{\frac{2 \times \Delta P}{\rho_{air}}} \times 60 \]

Discharge Coefficient (C_d):

Orifice Area (A):

ft²

Pressure Difference (ΔP):

psi

Air Density (ρ_air):

lb/ft³

Air Flow (Q_cfm): ft³/min

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1. What is an Air Flow Through an Orifice Calculator?

Definition: This calculator determines the volumetric flow rate of air through an orifice based on the orifice characteristics and pressure difference.

Purpose: It helps engineers and technicians in HVAC, pneumatic systems, and fluid dynamics to estimate air flow rates for system design and analysis.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ Q_{cfm} = C_d \times A \times \sqrt{\frac{2 \times \Delta P}{\rho_{air}}} \times 60 \]

Where:

\( Q_{cfm} \) — Air flow rate (cubic feet per minute)
\( C_d \) — Discharge coefficient (dimensionless, typically 0.6-0.65)
\( A \) — Cross-sectional area of orifice (square feet)
\( \Delta P \) — Pressure difference across orifice (psi)
\( \rho_{air} \) — Air density (pounds per cubic foot)

Explanation: The formula calculates the theoretical flow rate adjusted by the discharge coefficient to account for real-world flow characteristics.

3. Importance of Air Flow Calculation

Details: Accurate air flow calculations are essential for proper system design, energy efficiency, and ensuring adequate ventilation or pneumatic operation.

4. Using the Calculator

Tips: Enter the discharge coefficient (default 0.62 for sharp-edged orifice), orifice area in square feet, pressure difference in psi, and air density (default 0.075 lb/ft³ for standard air). All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical discharge coefficient (C_d)?
A: For sharp-edged orifices, it's typically 0.62. For rounded orifices, it can approach 0.98.

Q2: How do I convert diameter to area for circular orifices?
A: Use \( A = \pi \times (d/2)^2 \), where d is diameter in feet.

Q3: What affects air density (ρ_air)?
A: Temperature, altitude, and humidity. Standard air is 0.075 lb/ft³ at 68°F and sea level.

Q4: Can this be used for other gases?
A: Yes, but you must use the correct density for the specific gas.

Q5: Why multiply by 60 in the formula?
A: The conversion from cubic feet per second to cubic feet per minute (CFM).