AGA3 Flow (with optional AGA8 properties)

Returns base-condition volumetric flow via AGA3 detail method.

If gas_properties_given = False, gas properties (z_f, z_b, molar_mass, k) are computed from composition via AGA8.

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Python Version Used: 3.13.6

Function Summary

• Input: operating conditions, units, meter geometry/expansion data, optional gas composition, optional manual gas-property overrides
• Output: (volumetric_flow, z_f, z_b, k, molar_mass)
• Extras: Handles unit conversions (psi↔bar, °C↔°F, mbar↔inWC) and downstream-tap logic.

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Inputs

Operating & Units

• p (float) — Flowing gauge pressure in p_unit.
• t (float) — Flowing temperature in t_unit.
• d_p (float) — Orifice differential pressure in d_p_unit.
• p_atm (float) — Atmospheric pressure (absolute) in p_unit.
• p_b (float) — Base pressure (absolute) in p_unit.
• t_base (float) — Base temperature in t_unit.
• p_unit ('psi' | 'bar') — Unit for p, p_atm, p_b.
• t_unit ('C' | 'F') — Unit for t and t_base.
• d_p_unit ('mbar' | 'inwc') — Unit for d_p.
• pressure_tap ('Upstream' | 'Downstream') — If 'Downstream', upstream static is inferred as p + d_p (with proper unit conversion).

Meter Geometry & Thermal Expansion

• length_unit ('mm' | 'in') — Length unit for diameters.
• d0, D0 (float) — Orifice & pipe diameters at their reference temperatures (d0_tb, D0_tb, in t_unit).
• d0_tb, D0_tb (float) — Reference temperatures (match t_unit) for d0, D0.
• alpha_d, alpha_D (float) — Linear thermal expansion coefficients (1/°C).
• mu (float) — Gas viscosity at flowing conditions (Pa·s recommended).

Gas Composition (mol %)

Unspecified components default to 0:

N2, CO2, C1, C2, C3, iC4, nC4, iC5, nC5, nC6, nC7, nC8, nC9, nC10, H2, O2, CO, H2O, H2S, He, Ar

Manual Override for Gas Properties

• gas_properties_given (bool, default False) — If True, bypass AGA8 and use manual values.
• z_f_manual, z_b_manual (float) — Compressibility at flowing/base.
• molar_mass_manual (float, g/mol) — Mixture molar mass.
• k_manual (float) — Isentropic exponent (k = C_p/C_v).

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Outputs

Returns a 5-tuple:

1. volumetric_flow — Base-condition flow rate (unit per your aga3_calculate implementation).
2. z_f — Compressibility at flowing conditions.
3. z_b — Compressibility at base conditions.
4. k — Isentropic exponent at flowing conditions.
5. molar_mass — Mixture g/mol.

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Notes (Concise)

• Pressures

  • p is gauge pressure.
  • p_atm and p_b are absolute pressure.
  • If p_unit = 'bar', inputs are internally converted to psi as needed.

• Temperatures & Expansion

  • If t_unit = 'F', temperatures convert to °C internally.
  • alpha_d/alpha_D are assumed per °C/°F, according to chosen temperature unit; if inputs are in °F, coefficients are converted automatically.

• Tap Location

  • With pressure_tap = 'Downstream', the upstream static used for AGA8/AGA3 is p + d_p (after unit alignment).

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Disclaimer

This documentation and any associated calculations are provided as-is for engineering reference. Outputs are not guaranteed; validate results against official AGA3/AGA8 standards, calibrated instruments, and site-specific procedures before use in operations or billing.

Streamlit Demo App

A minimal Streamlit UI has been built on top of this calculate(...) function to help test inputs and visualize results.
You can wire your fields (pressure/temperature/DP/geometry/composition) to the function and display the returned tuple.

Live demo: aga3calculation.streamlit.app

Heads-up: On Streamlit Community Cloud the app may be sleeping after inactivity. The first load can take ~30–60 seconds to start.

Quick start:

pip install -r requirements.txt  # ensure streamlit and dependencies are installed
streamlit run web.py             # app.py calls calculate(...) under the hood

## Minimal Usage Sketch (Python)

```python
vol_flow, zf, zb, k, M = calculate(
    p=..., t=..., d_p=..., p_atm=..., p_b=...,
    p_unit='psi', t_unit='C', d_p_unit='mbar',
    t_base=..., pressure_tap='Upstream',
    length_unit='mm',
    d0=..., D0=..., d0_tb=..., D0_tb=...,
    alpha_d=..., alpha_D=...,
    mu=...,
    # Option A: auto AGA8 from composition
    N2=..., CO2=..., C1=..., C2=..., C3=..., iC4=..., nC4=...,  # etc.
    gas_properties_given=False
    # Option B: manual properties
    # gas_properties_given=True,
    # z_f_manual=..., z_b_manual=..., molar_mass_manual=..., k_manual=...
)