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อัปเดต 2026-09-07
Compressible gas
real-gas momentum
Compressible-gas mode: density varies with pressure via a real-gas EOS, solved on the gas-momentum path with choked-flow limits.
เมื่อไรจึงใช้
- Gas headers, letdown lines, vent/relief gas, compressible pipe flow with meaningful ΔP/P.
ค่าที่ต้องกรอก
| ค่า | คำอธิบาย |
|---|---|
| Gas name | Selects properties from the gas database (or a blended composition, ideal mixing). |
| Conditions | Inlet pressure/temperature; JT cooling is evaluated where thermo is available. |
คำนวณอย่างไร
Density follows a real-gas equation of state (compressibility Z), re-evaluated at each link’s local pressure. The isothermal compressible-flow momentum balance relates the squared end pressures to the mass flow and friction; the Mach number is capped at choke and flagged.
สมการ
Real-gas density
Z = compressibility from a PR / GERG EOS, R_s = specific gas constant. Z→1 recovers the ideal gas.
Isothermal pipe flow
The squared-pressure form for isothermal compressible flow; the ln term is the kinetic (line-pack) contribution.
Mach number
γ = ratio of specific heats. M → 1 is choke — the engine caps and flags it rather than reporting past it.
ข้อควรระวัง
noteVery high pressure (≥70 bar) PR-Z or a gas node that flashes non-vapour raises a loud honesty note (A28/A30).
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