Compressed Air Flow Rate Calculation

Orifice Flow Equation:

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

Discharge Coefficient (C_d):

unitless

Area (A):

m²

Pressure Difference (ΔP):

Density (ρ):

kg/m³

Flow Rate (Q):

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1. What is the Orifice Flow Equation?

The orifice flow equation calculates the volumetric flow rate of a fluid through an orifice plate. It is widely used in engineering applications for measuring flow rates in pipes and ducts, particularly for compressed air systems.

2. How Does the Calculator Work?

The calculator uses the orifice flow equation:

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

Where:

\( Q \) — Volumetric flow rate (m³/s)
\( C_d \) — Discharge coefficient (unitless)
\( A \) — Cross-sectional area of orifice (m²)
\( \Delta P \) — Pressure difference across orifice (Pa)
\( \rho \) — Fluid density (kg/m³)

Explanation: The equation relates flow rate to the square root of pressure difference, accounting for energy losses through the discharge coefficient.

3. Importance of Flow Rate Calculation

Details: Accurate flow rate calculation is essential for system design, performance evaluation, energy efficiency optimization, and proper sizing of compressed air equipment.

4. Using the Calculator

Tips: Enter discharge coefficient (typically 0.6-0.9 for orifice plates), orifice area in square meters, pressure difference in Pascals, and fluid density in kg/m³. All values must be positive.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical discharge coefficient value?
A: For sharp-edged orifice plates, C_d typically ranges from 0.6 to 0.65. The exact value depends on orifice geometry and Reynolds number.

Q2: How do I calculate orifice area?
A: Area = π × (d/2)² where d is the orifice diameter in meters.

Q3: What density should I use for compressed air?
A: Use ideal gas law: ρ = P / (R × T) where P is absolute pressure, R = 287 J/(kg·K) for air, and T is absolute temperature in Kelvin.

Q4: What are the limitations of this equation?
A: Assumes incompressible flow, which may not be accurate for high-pressure compressed air systems. Also requires turbulent flow conditions.

Q5: How accurate is this calculation?
A: Accuracy depends on correct C_d value and measurement precision. For precise applications, consider using calibrated flow meters.