Nitrogen Flow Rate Calculator
Unit: PSIG (Gauge Pressure)
Unit: PSIG (Must be lower than Inlet)
Unit: Inches (Actual ID, not Nominal)
Unit: Feet
Unit: Degrees Fahrenheit (°F)
0.015 (Smooth Steel)
0.018 (Average Steel)
0.022 (Corroded/Old)
Dimensionless
Volumetric Flow Rate (Standard):
0 SCFM
Volumetric Flow Rate (Actual Outlet):
0 ACFM
Mass Flow Rate:
0 lb/hr
Gas Velocity (at Outlet):
0 ft/sec
Pressure Drop:
0 PSI
Calculating Nitrogen Flow Rate Through Piping
Designing nitrogen gas systems requires accurate calculation of flow rates based on pressure differentials and pipe geometry. Nitrogen (N2) is a widely used industrial gas for purging, blanketing, and pneumatic actuation. Unlike liquids, nitrogen is compressible, which means the calculation involves thermodynamic variables including temperature and absolute pressure ratios.
Engineering Insight: Small changes in pipe diameter have a massive impact on flow capacity. Doubling the pipe diameter can increase the flow rate by a factor of approximately 32 (2 to the power of 5), assuming other variables remain constant.
Input Parameters Explained
- Inlet Pressure (P1): The gauge pressure at the start of the pipe section.
- Outlet Pressure (P2): The gauge pressure at the end of the pipe section. The difference between P1 and P2 drives the flow.
- Pipe Inner Diameter (ID): The actual internal measurement of the pipe. For Schedule 40 steel pipe, a "2-inch" pipe actually has an ID of approximately 2.067 inches.
- Pipe Length: The equivalent length of the piping run, including straight pipe and equivalent lengths for fittings and valves.
- Temperature: The operating temperature of the gas, which affects its density and viscosity.
The Calculation Logic
This calculator utilizes the General Fundamental Flow Equation for compressible fluids. It is derived from the Darcy-Weisbach equation but adapted for gas flow where density changes along the pipe. The core formula used is:
Q = K × √[ (P1² – P2²) × D⁵ / (Sg × T × L × f) ]
Where:
- Q: Flow rate in Standard Cubic Feet per Minute (SCFM)
- P1, P2: Absolute pressures (psia)
- D: Inner diameter (inches)
- Sg: Specific Gravity of Nitrogen (approx 0.967)
- T: Absolute Temperature (Rankine)
- L: Length (feet)
- f: Friction factor
Standard vs. Actual Flow (SCFM vs ACFM)
SCFM (Standard Cubic Feet per Minute) measures the mass of gas flowing per minute corrected to "standard" conditions (usually 14.7 psia and 60°F). This is the value most used for billing and sizing compressors.
ACFM (Actual Cubic Feet per Minute) is the volume the gas occupies at the actual pressure and temperature at the outlet. This is critical for determining velocity inside the pipe to prevent erosion or noise issues.