Source: https://guthlabs.ai/docs/instruments/radiation-heat-transfer-calculator/implementation/

instrument implementation / implementation-contract

# Radiation Heat Transfer Calculator implementation

A source-bound implementation contract for Radiation Heat Transfer 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**: t4-144

**Effect**: Computation or source lookup only

## Input and validation requirements

- Division by zero or nonphysical results occur if ε1 or ε2 is zero in the two-surface denominator.

- The denominator formula becomes invalid when the surfaces do not have equal area and mutual view factor one.

- Missing view-factor usage can cause large errors for partial visibility, separated surfaces, or enclosure geometries.

- Negative, zero, or non-absolute temperatures are invalid for this radiation formula; temperatures must be positive kelvin.

- Emissivities outside the interval 0 to 1 are nonphysical.

- The result can be negative when T1<T2; the interface must clearly label this as heat transfer from surface 2 toward surface 1.

- An emissivity table needs material, wavelength, temperature, and surface-condition assumptions; tabulated emissivity is not universally a single constant.

- The honest label is incomplete because it does not explicitly state the equal-area, F=1, diffuse-gray, opaque, isothermal assumptions behind the two-surface formula.

## Required corrections

````
[
  {
    "vector": 1,
    "field": "q_net_W",
    "wrong": 616.9367,
    "correct": 6169.395,
    "cause": "exactly 10x low; her v2/v4 verify with same sigma"
  }
]
````

## Inspectable interface fixture

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

````
{
  "inputs": {
    "formula": "q=εσA(T1^4−T2^4)",
    "epsilon": 1,
    "area_m2": 2,
    "T1_K": 500,
    "T2_K": 300,
    "view_factor": 1
  },
  "expected_outputs": {
    "q_net_W": 616.9367368
  },
  "working": "T1^4=500^4=62,500,000,000 K^4. T2^4=300^4=8,100,000,000 K^4. Difference=54,400,000,000 K^4. q=1×(5.670374419×10^-8)×2×54,400,000,000. q=616.9367368 W."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/radiation-heat-transfer-calculator/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/radiation-heat-transfer-calculator/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/radiation-heat-transfer-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`