The natural gas velocity can be calculated by dividing the volumetric flow rate by the cross-sectional area of the pipe or conduit through which the gas is flowing.
Here's a breakdown of the calculation:
Formula:
V = Q / A
Where:
- V = Gas Velocity (typically in ft/sec or m/s)
- Q = Volumetric Flow Rate (typically in ft³/sec or m³/s)
- A = Cross-sectional Area of the pipe (typically in ft² or m²)
Steps:
-
Determine the Volumetric Flow Rate (Q): This value represents the volume of natural gas passing a given point per unit of time. It is often provided in standard cubic feet per second (ft³/sec) or cubic meters per second (m³/s). Make sure your units are consistent.
-
Calculate the Cross-sectional Area (A): The cross-sectional area of a circular pipe is calculated using the following formula:
A = πD²/4
Where:
- π (pi) ≈ 3.14159
- D = Diameter of the pipe (typically in feet or meters)
-
Calculate Velocity (V): Substitute the values of Q and A into the formula V = Q / A to determine the gas velocity.
Example:
Let's say you have a natural gas flow rate of 60 ft³/sec through a pipe with a diameter of 1 foot.
- Q = 60 ft³/sec
- D = 1 ft
Calculate the area:
A = πD²/4 = π(1 ft)²/4 ≈ 3.14159 / 4 ≈ 0.785 ft²
Now, calculate the velocity:
V = Q / A = 60 ft³/sec / 0.785 ft² ≈ 76.4 ft/sec
Important Considerations:
- Units: Ensure all units are consistent before performing calculations. If the flow rate is given in cubic feet per hour (CFH), convert it to cubic feet per second by dividing by 3600 (seconds/hour). Likewise, if the diameter is given in inches, convert it to feet by dividing by 12.
- Pipe Schedule: The pipe schedule affects the actual inner diameter of the pipe. Ensure you use the correct inner diameter when calculating the cross-sectional area.
- Gas Composition and Conditions: While this calculation focuses on volumetric flow, understanding the gas composition, temperature, and pressure is crucial for more advanced analyses, such as calculating the Reynolds number to determine flow regime (laminar or turbulent).
- Reynolds Number: As demonstrated in the reference material, the Reynolds Number (Re) can be used to determine if the flow is turbulent. Re = (D V ρ) / μ, where ρ is the density and μ is the dynamic viscosity of the gas. If Re > 4000, the flow is typically considered turbulent.
