Source: https://guthlabs.ai/docs/instruments/cylindrical-spherical-conduction-resistance-calculator/implementation/

instrument implementation / implementation-contract

# Cylindrical/Spherical Conduction Resistance Calculator implementation

A source-bound implementation contract for Cylindrical/Spherical Conduction Resistance Calculator; deployment and executable qualification remain separate.

Status: **VERIFIED_CLEAN**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-clean

**Evidence ID**: t4-120

**Effect**: Computation or source lookup only

## Input and validation requirements

The specified formulas expose unhandled invalid-input hazards: equal radii produce zero resistance and an undefined heat-rate division, zero conductivity produces a division-by-zero resistance, and an unstated sign convention can reverse the heat-rate sign.

## Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

## Inspectable interface fixture

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

````
{
  "inputs": {
    "geometry": "cyl",
    "r1_m": 0.05,
    "r2_m": 0.06,
    "k_W_per_mK": 0.5,
    "L_m": 1,
    "deltaT_K": 100
  },
  "expected_outputs": {
    "R_total_K_per_W": 0.0580348,
    "q_W": 1723.1054
  },
  "working": "R=ln(0.06/0.05)/(2π·0.5·1)=ln(1.2)/π=0.1823215568/3.141592654=0.0580348 K/W. q=ΔT/R=100/0.0580348=1723.1054 W."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/cylindrical-spherical-conduction-resistance-calculator/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/cylindrical-spherical-conduction-resistance-calculator/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/cylindrical-spherical-conduction-resistance-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`