Air Hose CFM Calculator (Flow in Cubic Feet Per Minute)

Air Flow Formula (Hagen-Poiseuille Equation):

\[ Q = \frac{π \times r^4 \times ΔP}{8 \times μ \times L} \times \text{conversion to cfm} \]

Hose Radius:

feet

Pressure Difference (ΔP):

psf

Air Viscosity (μ):

lb·s/ft²

Hose Length:

feet

Air Flow Rate (CFM):

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1. What is an Air Hose CFM Calculator?

Definition: This calculator estimates the volumetric flow rate of air through a hose in cubic feet per minute (CFM) using the Hagen-Poiseuille equation.

Purpose: It helps engineers, technicians, and HVAC professionals determine air flow rates for pneumatic systems, ventilation, and compressed air applications.

2. How Does the Calculator Work?

The calculator uses the Hagen-Poiseuille equation:

\[ Q = \frac{π \times r^4 \times ΔP}{8 \times μ \times L} \times 60 \]

Where:

\( Q \) — Air flow rate (cubic feet per minute)
\( r \) — Hose radius (feet)
\( ΔP \) — Pressure difference (pounds per square foot)
\( μ \) — Dynamic viscosity of air (lb·s/ft²)
\( L \) — Length of hose (feet)

Explanation: The equation calculates laminar flow through a cylindrical pipe, with the result converted from ft³/s to CFM (ft³/min).

3. Importance of Air Flow Calculation

Details: Proper air flow estimation ensures efficient system operation, adequate ventilation, and correct sizing of pneumatic components.

4. Using the Calculator

Tips: Enter hose radius (convert diameter by dividing by 2), pressure difference (1 psi = 144 psf), viscosity (default for air at 68°F), and hose length. All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What's the typical viscosity of air?
A: At 68°F (20°C), air viscosity is approximately 3.73×10⁻⁷ lb·s/ft² (default value).

Q2: Does this work for any gas?
A: Yes, but you must use the correct viscosity value for the specific gas and temperature.

Q3: Is this only for laminar flow?
A: Yes, the Hagen-Poiseuille equation applies only to laminar flow (Re < 2300). For turbulent flow, use the Darcy-Weisbach equation.

Q4: How do I convert PSI to PSF?
A: Multiply PSI by 144 (1 psi = 144 psf).

Q5: What if my hose isn't circular?
A: This calculator assumes perfect circular cross-section. For non-circular ducts, use hydraulic diameter calculations.