AGA Fully Turbulent Flow

Introduction

This is one of the most recommended and used equations for this type of flow, being able to estimate with high precision flow and pressure drop values if pipe roughness is known with correctness. It has been used for comparison among the different flow equations as a reference basis because it is fundamental to the definition of the corresponding application ranges and errors.

Similar to the Colebrook Equation, the AGA Equation uses a slightly modified transmission factor in order to obtain a value for the pressure drop using the General Flow Equation. The transmission value for the AGA equation is the following: F=4\log_{10}\biggr(\frac{3.7D}{k}\biggr)

F=4\log_{10}\biggr(\frac{3.7D}{k}\biggr)

This equation is also known as the Von Karman equation for rough pipe flow.
𝐹 − Transmission Factor
𝑘 − Pipe Roughness
𝐷 − Internal Diameter (in)

Q=C_Q(4\log_{10}3.7D-4\log_{10}k )(\frac{T_b}{P_b})D^{2.67}\biggr[ \frac{P_1^2-e^sP_2^2}{GT_fL_eZ} \biggr]^{0.5}

Q=C_Q(4\log_{10}3.7D-4\log_{10}k   )(\frac{T_b}{P_b})D^{2.67}\biggr[    \frac{P_1^2-e^sP_2^2}{GT_fL_eZ}    \biggr]^{0.5}

𝑄 − Flow Rate (FT³/day)
𝐶_𝑄 − 38.774
𝑇_𝑏 −Temperature Base (°R)
𝑃_𝑏 − Pressure Base (psia)
𝑇_𝑓 − Gas Flowing Temperature (°R)
𝐷 − Internal Diameter (in)
𝑘 − Pipe Roughness
𝑃₁ − Upstream Pressure (psig)
𝑃₂ − Downstream Pressure (psig)
𝐺 − Gas Specific Gravity
𝑍 − Compressibility Factor
L_e − Pipe Segment Length including Expansion (mi)
𝑇_𝑓 − Gas Flowing Temperature (°R)

s=\frac{C_S\triangle HG}{T_fZ}

s=\frac{C_S\triangle HG}{T_fZ}

𝑠 − Elevation adjustment parameter
𝐶_𝑆 − 0.0375
𝑍 − Compressibility Factor
𝑇_𝑓 − Gas Flowing Temperature (°R)
∆𝐻𝐺 − Change in Elevation (ft)

L_e=\frac{(e^s-1)}{s}

L_e=\frac{(e^s-1)}{s}

𝐿_𝑒 − Pipe Segment Length including Expansion (mi)
𝑠 − Elevation adjustment parameter

V=0.75\frac{Q_h}{D^2P_{avg}}

V=0.75\frac{Q_h}{D^2P_{avg}}

𝑉 − Velocity (ft/sec)
𝑄_ℎ − Volumetric flow rate (scf/hr)
𝐷 − Internal Diameter (in)
𝑃_𝑎𝑣𝑔 − Average Pipeline Pressure (psia)

For Small Pressure Drop P2 > 0.8 P1:

P_{avg}=\frac{(P_1-P_2)}{2}

P_{avg}=\frac{(P_1-P_2)}{2}

For Large Pressure Drop:

P_{avg}=\frac{2}{3}\biggr[ P_1+P_2-\frac{P_1P_1}{P_1+P_2} \biggr]

P_{avg}=\frac{2}{3}\biggr[  P_1+P_2-\frac{P_1P_1}{P_1+P_2}    \biggr]

Case Guide

Part 1: Create Case

Input Parameters

• Temperature base(°F)
• Pressure base(psia)
• Gas Flowing Temperature(°F)
• Gas Specific Gravity
• Compressibility Factor
• Pipeline Efficiency Factor
• Upstream Pressure(psig)
• Downstream Pressure(psig)
• Flow Rate(MSCFH)
• Internal Pipe Diameter(in)
• Length of Pipeline(mi)
• Upstream Elevation(ft)
• Downstream Elevation(ft)

Downstream Pressure

Flow Rate

Internal Pipe Diameter

Upstream Pressure

Part 2: Outputs/Reports

Results

• Downstream Pressure(psig)
• Flow Rate(ft/sec.)
• Internal Pipe Diameter(in)
• Upstream Pressure(psig)
• Transmission Factor
• Velocity(ft/sec.)
• Erosional Velocity(ft/sec.)
• Sonic Velocity(ft/sec.)

Downstream Pressure

Flow Rate

Internal Pipe Diameter

Upstream Pressure

References

• McAllister, E. W., “Pipeline Rules of Thumb” Gulf Professional Publishing, Seventh Edition
• Menon, Shahi E., “Gas Pipeline Hydraulics”, Systek Technologies, Inc.
• Carroll, Landon and Hudkins, Weston R., “Advanced Pipeline Design”
• American Gas Association (AGA), “Reference: Eq-17-18, Section 17, GPSA”, Engineering Data Book, Eleventh Edition

FAQ