Air Velocity Calculator

Detailed Description

This calculator estimates compressed air velocity for each supported nominal pipe size using free-air flow, line pressure, atmospheric pressure, and the internal area table documented in Compressed Air Pipe Data. All formulas use U.S. customary units.

Main headers and branches are typically designed near 20 ft/s and should not exceed 30 ft/s. Line drops and feed lines are commonly limited to 30 ft/s with an upper limit of 50 ft/s.

Velocity By Pipe Size

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Compressed air velocity for one nominal pipe size.

The free-air flow rate is first scaled to line pressure using the ratio of atmospheric pressure to absolute line pressure. The result is divided by each pipe's internal area. The factor 144 converts square feet to square inches, and the factor 60 converts minutes to seconds.

\begin{equation}\label{eq:air-velocity} v_i = Q \cdot \frac{P_{atm}}{P_{line} + P_{atm}} \cdot \frac{k_{144}}{A_i} \cdot \frac{1}{k_{60}} \end{equation}

Symbols

\(v_i\)	Compressed air velocity for nominal pipe size i \([\unit{ \foot\per\second}]\)
\(Q\)	Volumetric free-air flow rate \([\unit{ \standardCubicFeetPerMinute}]\)
\(P_{atm}\)	Atmospheric absolute pressure \([\unit{ \psia}]\)
\(P_{line}\)	Pipe gauge pressure \([\unit{ \psig}]\)
\(k_{144}\)	Square inches per square foot (144) \([\unit{ \inch\squared\per\squareFoot}]\)
\(A_i\)	Internal area for nominal pipe size i \([\unit{ \inch\squared}]\)
\(k_{60}\)	Seconds per minute (60) \([\unit{ \second\per\minute}]\)

Note

The internal areas used by this calculation are in square inches. This matches the formula's 144 in2/ft2 conversion and the implementation table in Compressed Air Pipe Data.

Modules
	Air Velocity Formula
	Compressed air velocity for one nominal pipe size.

Files
file	air_velocity.h
	Declarations for compressed air velocity calculations.

Namespaces
namespace	air_velocity
	Compressed air velocity calculator.

Classes
struct	air_velocity::Input
	Input parameters for the air velocity calculation. More...