ASME PTC 10 Explained — Compressor Shaft Power, Isentropic Efficiency & Discharge Temperature (ideal-gas calculator)
ASME PTC 10 — Performance Test Code on Compressors and Exhausters
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ASME PTC 10-1997 (Performance Test Code on Compressors and Exhausters) is one of the ASME Performance Test Codes — a separate ASME code family from the Boiler & Pressure Vessel Code — and defines the accepted method for MEASURING and reducing the thermodynamic performance of continuous-flow compressors and exhausters, i.e. centrifugal and axial machines. Displacement machines (reciprocating, screw) are covered by ASME PTC 9, not PTC 10. It establishes the governing definitions of isentropic and polytropic specific work, isentropic efficiency, the temperature and pressure measurement conventions for acceptance testing, and the allowable test gas substitution rules when the specified process gas cannot be used during the performance test. PTC 10 is the standard vendors and operators cite when a compressor is contracted with a power or efficiency guarantee.
MechanixCalc does NOT perform a PTC 10 test evaluation: its compressor calculator applies textbook ideal-gas compression thermodynamics with an isentropic efficiency, using PTC 10 terminology. Enter the suction and discharge conditions, the gas, the number of stages and the isentropic efficiency, and the tool returns shaft power, actual discharge temperature, overall isentropic efficiency, volumetric flow rate and motor drive sizing in one pass. Multi-stage configurations with intercooling resolve the per-stage temperatures, pressures and work split automatically. A P-V and T-s thermodynamic diagram, a reciprocating P-V indicator loop and a centrifugal surge/choke operating map provide the visual context that vendors and reviewers expect.
Related calculators — ASME PTC 10 itself is not implemented
What ASME PTC 10 covers
- Isentropic (adiabatic) specific work and shaft power — derived from the steady-flow energy equation for a reversible adiabatic process using the inlet temperature, the overall pressure ratio and the gas ratio of specific heats γ
- Isentropic efficiency — the ratio of ideal isentropic work to actual shaft work; the tool compares them on a like-for-like (stage-sum) basis of its own so an intercooled machine cannot read η > 100 %
- Actual discharge temperature — isentropic temperature rise scaled by the isentropic efficiency, giving the true exit state of the gas
- NOT in ASME PTC 10: multi-stage compression with intercooling (an intercooler approach; 0 K = perfect intercooling), including the equal-stage-pressure-ratio result for minimum total work, the per-stage T/P/work breakdown and intercooler duty. That is classical compression thermodynamics — a DESIGN calculation, where PTC 10 is a test procedure. ⚠️ Note also that PTC 10's primary performance basis is POLYTROPIC head and efficiency; the isentropic route above is the one the MechanixCalc tool implements
- NOT in ASME PTC 10 (which covers continuous-flow machines only — reciprocating compressors are ASME PTC 9): the reciprocating P-V indicator loop, with polytropic compression and re-expansion curves, clearance-volume volumetric efficiency and indicated work per cycle on the induced rather than swept volume
- Centrifugal compressor surge margin and choke margin with operating-point map (engineering-estimate panel, marked with EstimateBadge; verify against manufacturer's test data)
Governing formulas
W_is = (γ / (γ − 1)) · R · T₁ · ( (P₂/P₁)^((γ−1)/γ) − 1 )where W_is = isentropic specific work (kJ/kg); γ = ratio of specific heats Cp/Cv (dimensionless); R = specific gas constant (kJ/kg·K); T₁ = absolute inlet temperature (K); P₂/P₁ = overall pressure ratio (dimensionless). Shaft power P_shaft = ṁ · W_is / η_is, where ṁ = mass flow rate (kg/s) and η_is = isentropic efficiency (dimensionless)
T₂ = T₁ + (T₂ₛ − T₁) / η_is where T₂ₛ = T₁ · (P₂/P₁)^((γ−1)/γ)where T₂ = actual discharge temperature (K); T₂ₛ = isentropic discharge temperature (K); T₁ = absolute inlet temperature (K); P₂/P₁ = pressure ratio; γ = ratio of specific heats; η_is = isentropic efficiency (dimensionless, 0–1)
η_v = 1 − c · ( (P₂/P₁)^(1/n) − 1 )where η_v = volumetric efficiency (dimensionless); c = clearance ratio = V_clearance / V_displacement (dimensionless); P₂/P₁ = pressure ratio; n = polytropic index (dimensionless). The indicated work per cycle equals the enclosed area of the P-V loop computed on the induced volume (BDC − end of re-expansion), which excludes the shuttle work of the clearance gas
Frequently asked questions
What is ASME PTC 10 used for?
ASME PTC 10 (Performance Test Code on Compressors and Exhausters) defines the accepted engineering method for measuring and verifying the thermodynamic performance of compressors. It establishes how the measured head, efficiency and shaft power are defined and reduced (its primary basis is polytropic), and it specifies the test procedures — including allowable substitute gas rules — used when a compressor is contracted with a power or efficiency guarantee. It applies to continuous-flow (centrifugal and axial) machines; displacement compressors are covered by ASME PTC 9 and ISO 1217.
What is the difference between ASME PTC 10 and ISO 1217?
ASME PTC 10 covers continuous-flow compressors (centrifugal and axial) and is a performance-test code — it governs how a factory or field test is conducted and the acceptance criteria applied to a contract guarantee. ISO 1217 applies to displacement compressors (reciprocating and screw) and focuses on acceptance-test measurement methods and tolerances for that class. MechanixCalc implements neither test procedure: its calculator is textbook ideal-gas thermodynamics that uses their terminology.
Does MechanixCalc implement the full ASME PTC 10 method?
No. PTC 10 is a test code with a polytropic primary basis, real-gas corrections (the Schultz factor) and test-to-guarantee similarity rules; none of that is implemented. The compressor analysis calculator uses the textbook ideal-gas isentropic specific-work formula, computes shaft power as ṁ·W_is/η_is, derives the actual discharge temperature from the isentropic temperature rise, and reports overall isentropic efficiency on the correct like-for-like basis (avoiding the η > 100 % artefact that arises in intercooled machines if the single-stage isentropic ideal is compared against the intercooled actual work). The method is shown in the generated PDF report.
How does multi-stage intercooling affect compressor power?
Compression work is proportional to the absolute inlet temperature (classical thermodynamics — not a PTC 10 subject). Cooling the gas between stages lets each later stage start from a low inlet temperature; perfect intercooling back to the suction temperature minimises the total work, and a real intercooler's approach (outlet above suction) raises it — the calculator takes that approach as an input. The equal-stage-pressure-ratio split (r_stage = (P₂/P₁)^(1/N)) is the thermodynamically optimal arrangement for minimum total shaft power. The MechanixCalc compressor calculator shows the per-stage power breakdown and the total saving relative to single-stage compression for up to four stages.
Is the ASME PTC 10 compressor calculator free?
You can use it during a free 30-minute preview with no sign-up required, and a free 14-day account trial unlocks every MechanixCalc calculator with no credit card. The branded PDF engineering report and saved calculations are included in the free 14-day trial and in every paid plan.
Related standards
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