Biot Number / Lumped Capacitance Validity Check

Inspectable records

Ledger state

The current ledger marks this instrument verified clean within the source-bound verification corpus.

Area

Thermodynamics, Fluids & Aero

Tranche

tranche-4

Evidence ID

t4-204

Ledger rows

1

No ledger note is attached.

Review findings

Formula and threshold are conditionally standard, but the instrument needs an explicit definition or required input convention for Lc, preferably Lc = volume/surface area for the body under analysis. The honest label should state that PASS means Bi < 0.1 under the selected geometry and property assumptions, not that lumped capacitance is universally accurate.

Formula and scope findings

• Bi = hLc/k is the standard Biot-number formula when Lc is the appropriate characteristic length, commonly V/A for lumped-capacitance analysis.
• The validity rule is correctly stated as Bi < 0.1, but the specification does not define how Lc is obtained from body geometry; using a different length convention can change the result.
• The output flag should explicitly define that Bi = 0.1 is FAIL because the stated criterion is a strict inequality.

Unit assumptions

• h is in W/(m^2·K).
• Lc is in m.
• k is in W/(m·K).
• Temperature units cancel, so K and °C temperature differences are equivalent in this ratio.
• h, Lc, and k must describe the same physical body and operating temperature range.
• k must be positive; material thermal conductivity may vary with temperature.

Boundary hardening

BREAK_CLAIMED · SELF_FLAGGED

A zero thermal-conductivity input causes division by zero and an undefined Bi unless explicitly rejected. A separate convention ambiguity can also change the validity result from pass to fail.

Errata and corrections

No applied erratum is attached to this unique-name record.

Inspectable example

4 review vectors are recorded. One source-bound sample is shown below.

{
  "inputs": {
    "h": 25,
    "Lc": 0.01,
    "k": 0.5,
    "units": "h in W/(m^2·K), Lc in m, k in W/(m·K)"
  },
  "expected_outputs": {
    "Bi": 0.5,
    "valid": "FAIL"
  },
  "working": "Bi = hLc/k = (25 × 0.01) / 0.5 = 0.25 / 0.5 = 0.5. Since 0.5 is not less than 0.1, valid = FAIL."
}

Related workflows

Sources and evidence

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

• VERIFIED_LEDGER.json · VERIFIED_CLEAN
• evidence-tranche4/tranche4-results.json
• BOUNDARY_HAZARD_CATALOG.json