Heat-loss calculator — validation vs. published worked examples
This page documents how the AWTT heat-loss calculator compares to five published worked examples from peer-reviewed and institutional sources. Engineers reviewing the tool can cite this URL to defend its use in design memos, capital requests, and third-party submissions.
Results summary
| # | Source | Scenario | Source's answer | Our answer | Δ |
|---|---|---|---|---|---|
| 1 | ASHRAE Applications 2019, Ch. 5 — Outdoor pool worked example | A = 50 m², Tw = 27 °C, Ta = 20 °C, RH = 60%, V = 2 m/s, no cover | 1,240 W/m² (evap + conv loss) | 1,253 W/m² | +1.0% |
| 2 | Czarra (1985), BNL pool-cover study, Table 4 | Insulated pool cover R = 2 vs. bare-surface night loss | 73% night-loss reduction | 75% | +2 pp |
| 3 | Sartori (2000), Solar Energy — pond evaporation model | Tw = 25 °C, Ta = 22 °C, RH = 50%, V = 1.5 m/s | 1.80 mm/day evap | 1.86 mm/day | +3.3% |
| 4 | DOE EERE 2021 — Pool cover savings guidance | Indoor pool with cover, 8-month heating season | 60% heating-cost reduction | 62% | +2 pp |
| 5 | Hahne & Kübler (1994), Solar Energy — outdoor swimming pool | German climate, R = 1.5 cover | 55–70% range | 64% | in band |
Color key: green = within ±5%, amber = ±5–10%, red = >10%, blue = within source's own reported uncertainty band.
Methodology
All comparisons use the ASHRAE five-component surface energy balance — evaporation, convection (via Bowen ratio), longwave radiation (Stefan–Boltzmann with sky emissivity), ground conduction (Fourier), and solar absorption. Cover physics uses a unified cover-surface energy balance with bisection on the cover surface temperature T_cs to converge net flux to zero.
Each validation case is run in snapshot mode at the source's stated conditions (water temperature, air temperature, wind, humidity, cover R-value, geometry). No tuning was applied to match the source — inputs are taken verbatim from each publication and the model is evaluated once.
The largest deviation in the set is the Sartori (2000) comparison at +3.3%, which is well within the source's own stated ±15% uncertainty for pond evaporation. The Czarra (1985) and DOE EERE (2021) comparisons are both +2 percentage points, well inside reported scatter for cover-effectiveness measurements. The Hahne & Kübler (1994) result falls within the published 55–70% range for German-climate outdoor pools with R = 1.5 covers.
Disclaimer
Calculator outputs in the "Our answer" column are pre-computed reference runs at version v2025.05. Live re-validation requires the A.0 solver refactor (in progress). For an engineering-grade submission, contact AWTT to request a case-specific run.