Source: https://guthlabs.ai/docs/instruments/steam-table-property-lookup/mechanism/

instrument mechanism / verified-clean

# Steam Table Property Lookup mechanism

The inspectable method record for Steam Table Property Lookup, kept separate from implementation and qualification.

Status: **VERIFIED_CLEAN**Lifecycle: **verified-clean**

## Model scope

The core method is standard, but the empty honest_label and unspecified interpolation/phase/cp conventions require review before catalog approval. The label should state the supported pressure-temperature range, whether results are exact IF97 evaluations or interpolated table estimates, the allowed quality range, and that cp at two-phase or saturation states is undefined or path-dependent unless a specific derivative convention is supplied.

- IAPWS-IF97 is a valid standard formulation for water and steam properties, but the specification does not define the region-selection logic, saturation-boundary handling, or validity limits.

- P and T alone do not uniquely define a two-phase state; quality x or an equivalent phase specification is required when the state lies in the saturation dome.

- Table interpolation is not a uniquely defined algorithm. The specification must state the interpolation variables, interpolation order, independent-variable grid, and whether interpolation is permitted across phase or IF97-region boundaries.

- cp is not normally supplied as a basic saturated-water/steam table property. At saturation, cp is path-dependent or undefined as a single two-phase equilibrium property; IF97 cp should be explicitly defined as the isobaric derivative for a single-phase state.

- The instrument claims to compute h, s, v, u, and cp, but the specification does not state the reference state and unit conventions expected for h, u, and s.

## Units and conventions

- Pressure is entered and reported in kPa unless explicitly labeled otherwise; 1 kPa·m^3/kg = 1 kJ/kg for the Pv term.

- Temperature is in degrees Celsius for table lookup; IF97 internally requires absolute temperature in kelvin.

- Specific enthalpy h and internal energy u are in kJ/kg.

- Specific entropy s and heat capacity cp are in kJ/(kg·K).

- Specific volume v is in m^3/kg.

- Quality x is dimensionless, with x=0 saturated liquid and x=1 saturated vapor.

## Inspectable vector

One of 4 source-bound review vectors:

````
{
  "inputs": {
    "pressure_kPa": 101.325,
    "temperature_C": 100,
    "quality": 0,
    "state_specification": "saturated liquid"
  },
  "expected_outputs": {
    "h_kJ_per_kg": 419.04,
    "s_kJ_per_kg_K": 1.3072,
    "v_m3_per_kg": 0.001043,
    "u_kJ_per_kg": 418.9343,
    "cp_kJ_per_kg_K": 4.216,
    "phase_region": "saturation boundary, saturated liquid"
  },
  "reference_data": {
    "pressure_kPa": {
      "value": 101.325,
      "source_convention": "widely tabulated standard value; water saturation pressure at 100 C"
    },
    "temperature_C": {
      "value": 100,
      "source_convention": "widely tabulated standard value; normal boiling point of water at 101.325 kPa"
    },
    "hf_kJ_per_kg": {
      "value": 419.04,
      "source_convention": "IAPWS/IF97 standard steam-table value"
    },
    "sf_kJ_per_kg_K": {
      "value": 1.3072,
      "source_convention": "IAPWS/IF97 standard steam-table value"
    },
    "vf_m3_per_kg": {
      "value": 0.001043,
      "source_convention": "IAPWS/IF97 standard steam-table value"
    },
    "cp_liquid_kJ_per_kg_K": {
      "value": 4.216,
      "source_convention": "widely tabulated standard value near 100 C"
    }
  },
  "working": "At 100 C and 101.325 kPa, x=0 selects saturated liquid. h = hf = 419.04 kJ/kg. s = sf = 1.3072 kJ/(kg K). v = vf = 0.001043 m^3/kg. u = h - Pv = 419.04 - (101.325)(0.001043) = 419.04 - 0.105682 = 418.9343 kJ/kg. cp is reported from the liquid-property table as 4.216 kJ/(kg K). This is an exact normal-boiling-point table entry and an edge case at x=0."
}
````

## Failure boundary

**BREAK_CLAIMED** · SELF_FLAGGED

The specification exposes two hard hazards: P=0 produces an undefined result and must be rejected, while the permitted P/T input does not define pressure units, absolute-versus-gauge convention, or quality at saturation. Consequently the same displayed input can select different regions or fail to determine unique h, s, v, u, and cp values.

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/steam-table-property-lookup/>)[03**Implementation**](<https://guthlabs.ai/docs/instruments/steam-table-property-lookup/implementation/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/steam-table-property-lookup/qualification/>)

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json`

- `evidence-tranche7/tranche7-results.json`

- `BOUNDARY_HAZARD_CATALOG.json`