Version 0.4.0

Version 0.4.0#

Version 0.4.0 brings a major internal rework of how performance points are computed, new conversion and serialization capabilities, and important robustness fixes for dense fluids and REFPROP.

Highlights#

  • Point is now built by a constraint-propagation solver, accepting any sufficient combination of inputs instead of a fixed list of argument combinations.

  • New Gaussian-process surrogate method for Impeller.convert_from, robust for dense CO₂-rich conditions where the similarity method could fail.

  • Point, Curve and Impeller objects can now be saved to and loaded from JSON and TOML files.

  • Compatibility with CoolProp 8.

New features#

  • Constraint-propagation point solver (#138) — the ~46 _calc_from_<args> methods that previously resolved a Point from its keyword arguments were replaced by a set of small thermodynamic relations and a fixpoint engine (ccp/point_solver.py) that keeps applying them until the point is fully defined. Any sufficient combination of inputs now works, including combinations that previously had no dedicated method.

  • Gaussian-process surrogate conversion (#144) — a new data-driven conversion method:

    converted = ccp.Impeller.convert_from(
    [imp_case_a, imp_case_b, imp_case_c],
    suc=target_suc,
    method="gp_surrogate",
)

    It fits ψ, η = f(φ, M_tip) over the points of all supplied measured maps and re-dimensionalizes the prediction at the target suction. Unlike method="similarity", it pools multiple maps and avoids the dense-fluid flash, so it stays robust for dense / supercritical CO₂-rich suctions.

  • Save/load to JSON and TOML (#145, #148) — Point, Curve, Impeller, StraightThrough and BackToBack can be saved to .json or .toml files, with the file extension selecting the format (point.save("point.json")). Public to_dict() / from_dict() methods provide an in-memory representation, and pathlib.Path objects are accepted as file names.

  • Improved extrapolation for curve conversion (#136) — speed extrapolation is now based on fan-law similarity (constant head coefficient ψ) referenced to the closest available speed curve. This makes it possible to convert maps that contain a single curve (fixed-speed compressors).

  • disch_p curve type in impeller loaders (#142) — Impeller.load_from_engauge_csv and Impeller.load_from_dict now accept discharge-pressure curves directly (disch_p_curves, disch_p_units), so a map can be loaded from measured discharge pressure and temperature without first converting to a pressure ratio.

  • ccp.REFPROP_AVAILABLE (#151) — a new flag indicating whether REFPROP was successfully loaded, useful to assert the intended backend is active instead of silently falling back to CoolProp’s HEOS.

Bug fixes#

  • Forced phase is preserved through Point and Impeller (#140) — a phase forced on a State (e.g. State(..., phase="gas")) was silently dropped when the state entered a Point or Impeller (copies and pickling lost phase and EOS). The forced phase now propagates end-to-end, including through conversion and save/load.

  • Robust convert_from for dense fluids (#141) — converting maps to dense, CO₂-rich, near-critical suction conditions frequently failed with ValueError: Could not calculate point. The isentropic discharge seed no longer converges to a spurious liquid-like (rho, s) flash root, and the efficiency solve was made robust for these conditions.

  • REFPROP concurrency fixes (#150) — intermittent “state cannot be generated” failures, deadlocks and process crashes during curve conversion were traced to concurrent entry into the REFPROP Fortran DLL (GIL-releasing ctypes calls, fork-based multiprocessing pools). Direct REFPROP calls now hold the GIL, fallbacks are coherent, and multiprocessing pools no longer use fork.

  • numpy 2.4 / CoolProp 7.2 compatibility (#146) — Impeller.curve no longer passes 1-element arrays into CoolProp scalar inputs (a hard TypeError under numpy 2.4), and Evaluation handles CoolProp 7.2 raising on NaN pressures for rows with sensor dropouts.

  • CoolProp 8 compatibility (#152) — fluid-name resolution handles the exception type changed in CoolProp 8, and ccp now works with both CoolProp 7 and 8.

API changes#

  • Point, Curve and Impeller save/load no longer take a file_type argument — the format is determined by the file extension, and an unsupported or missing extension raises a ValueError (#148).

  • The private _dict_to_save / _dict_from_load methods were replaced by public to_dict() / from_dict() (#148).

  • The private Point._calc_from_<args> methods were removed in favor of the point solver (#138).

Infrastructure and testing#

  • GitHub Actions CI runs the full test suite with a private REFPROP build (#151).

  • The test suite was reorganized with a slow marker for heavy integration modules and pytest-xdist parallelization, cutting the full run from about 1 h to about 7 min and adding a ~40 s fast tier for development (#147).

  • Expected test values were re-baselined after the interpolation and dependency changes (#137, #143, #146).