Source: https://guthlabs.ai/docs/instruments/overall-heat-transfer-coefficient-u-calculator/implementation/

instrument implementation / implementation-contract

# Overall Heat Transfer Coefficient (U) Calculator implementation

A source-bound implementation contract for Overall Heat Transfer Coefficient (U) Calculator; deployment and executable qualification remain separate.

Status: **VERIFIED_WITH_ERRATA**Lifecycle: **implementation-contract**

## Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

**Record owner**: Guth Instruments

**Lifecycle**: verified-with-binding-errata

**Evidence ID**: t4-192

**Effect**: Computation or source lookup only

## Input and validation requirements

The calculator should reject k=0 because the wall-resistance term divides by zero. The convention probe also exposes a substantial unit and radius-versus-diameter interpretation hazard if geometry metadata are not enforced.

## Required corrections

````
[
  {
    "vector": 2,
    "field": "UA/Ui/Uo",
    "wrong": "UA 14.033, Ui 44.668, Uo 37.224",
    "correct": "UA 13.113, Ui 41.740, Uo 34.783",
    "cause": "the specified Rfouling=0.005 K/W omitted from her own resistance sum (removal reproduces her numbers exactly)"
  }
]
````

## Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

````
{
  "inputs": {
    "hi": 1000,
    "ho": 50,
    "k": 16,
    "ri": 0.01,
    "ro": 0.012,
    "L": 1,
    "Rfouling": 0,
    "units": "hi,ho W/(m²·K); k W/(m·K); dimensions m; Rfouling K/W"
  },
  "expected_outputs": {
    "UA_W_per_K": 3.534,
    "Ui_W_per_m2K": 56.241,
    "Uo_W_per_m2K": 46.868
  },
  "working": "Ai=2π(0.01)(1)=0.0628319 m²; Ao=2π(0.012)(1)=0.0753982 m². Ri=1/(1000×0.0628319)=0.0159155 K/W. Rwall=ln(0.012/0.01)/(2π×16×1)=ln(1.2)/100.531=0.0018136 K/W. Ro=1/(50×0.0753982)=0.2652582 K/W. Rtotal=0.0159155+0+0.0018136+0.2652582=0.2829873 K/W. UA=1/0.2829873=3.5337 W/K. Ui=3.5337/0.0628319=56.241 W/(m²·K). Uo=3.5337/0.0753982=46.868 W/(m²·K)."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/overall-heat-transfer-coefficient-u-calculator/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/overall-heat-transfer-coefficient-u-calculator/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/overall-heat-transfer-coefficient-u-calculator/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-tranche4/tranche4-results.json`

- `tranche errata record`