Compressible

Overview

ax.set_ylim(0, 1.1)

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Python Libraries

These functions rely on the fluids library, which provides robust, vectorized implementations of gas dynamic relationships and pipeline standards. Using these validated libraries ensures accurate handling of compressibility effects, which are notoriously difficult to implement correctly using standard Excel formulas.

Gas Pipeline Transport

In industrial applications, compressible flow is dominant in natural gas transmission. Long-distance pipelines experience significant pressure drops, causing gas density to decrease and velocity to increase along the pipe.

Thermodynamic Processes

Calculation of work and efficiency in compressors and turbines relies on defining the path of the state change:

  • Isentropic: Adiabatic and reversible (ideal). ISENTROPIC_WORK calculates the theoretical work required for compression or expansion between two pressure states.
  • Polytropic: Real-world process with heat transfer and friction (PV^n = C). POLYTROPIC_EXP models the expansion process using a polytropic exponent n.
  • Isothermal: Constant temperature (idealized cooling). ISOTHERMAL_WORK calculates work for processes where heat is removed to maintain constant temperature.

Native Excel Capabilities

Excel has no native support for compressible flow. Users typically build manual models using the ideal gas law and standard thermodynamic formulas. While this works for simple cases, it fails to account for: - Real gas effects (compressibility factor Z) - Choked flow conditions in complex piping - Iterative solutions for pipeline sizing equations

The Python functions provided here handle these complexities automatically, allowing for more reliable engineering design directly within the spreadsheet environment.

Tools

Tool Description
FRITZSCHE_FLOW Calculate gas flow rate using the Fritzsche formula.
IGT_FLOW Calculate gas flow rate using the IGT (Institute of Gas Technology) formula.
IS_CHOKED_FLOW Determine if a flow is choked (critical) based on pressure ratio.
ISENTROPIC_EFF Convert between isentropic and polytropic efficiency for compression.
ISENTROPIC_T_RISE Calculate the temperature rise for isentropic compression or expansion.
ISENTROPIC_WORK Calculate work of compression or expansion for a gas in an isentropic process.
ISOTHERMAL_GAS Calculate mass flow rate for isothermal compressible gas flow in a pipe.
ISOTHERMAL_WORK Calculate work of compression or expansion for a gas in an isothermal process.
MULLER_FLOW Calculate gas flow rate using the Muller formula.
P_CRITICAL_FLOW Calculate critical flow pressure for a fluid at Mach 1.
P_STAGNATION Calculate stagnation pressure from static conditions.
PANHANDLE_A Calculate gas flow rate in a pipeline using the Panhandle A formula.
PANHANDLE_B Calculate gas flow rate in a pipeline using the Panhandle B formula.
POLYTROPIC_EXP Calculate polytropic exponent or polytropic efficiency for compression.
STAGNATION_ENERGY Calculate the increase in enthalpy due to fluid velocity.
T_CRITICAL_FLOW Calculate critical flow temperature for a fluid at Mach 1.
T_STAG_IDEAL Calculate ideal stagnation temperature from velocity and heat capacity.
T_STAGNATION Calculate stagnation temperature from pressure ratio.
WEYMOUTH_FLOW Calculate gas flow rate in a pipeline using the Weymouth formula.