Easily determine the Flow Coefficient (Cv) for air and various gases in non-critical pressure drop scenarios. This online tool is vital for accurate valve sizing, fluid dynamics analysis, and optimizing HVAC and industrial process systems. Understand how flow rate, pressure, temperature, and specific gravity influence gas Cv for efficient design and operation.
Formula:
The Flow Coefficient (Cv) for gases under non-critical pressure drop is calculated using a widely accepted engineering formula:
Cv = Q / (1360 × P1 × Y × √((P1 - P2) / (G × Tabs)))
Where the Expansion Factor Y is approximated as:
Y ≈ 1 - (P1 - P2) / (3 × P1)
- Q = Volumetric Flow Rate (Standard Cubic Feet per Hour, SCFH)
- G = Specific Gravity of Gas (dimensionless, Air = 1)
- Tabs = Absolute Inlet Temperature (Rankine, °R)
- P1 = Absolute Inlet Pressure (Pounds per Square Inch Absolute, psia)
- P2 = Absolute Outlet Pressure (Pounds per Square Inch Absolute, psia)
- Y = Expansion Factor (dimensionless)
Note: This calculation is valid for non-critical flow where P2 > 0.52 × P1 (for gases with k=1.4 like air). If P2 ≤ 0.52 × P1, the flow is considered critical (choked), and a different formula applies.