---
name: ferret-physics-heat
description: Use for temperature in Ferret: HeatNetwork parts with conduction, convection and radiation, phase change with latent heat, thermal expansion and stress, friction heat, and steel that loses strength when hot. Boiling pots, beams in a fire, hot walls, cooling.
---

# Heat

## When to use
Anything that warms, cools, melts, boils or weakens: pots, beams, walls, brakes, tanks.

## The model
A `HeatNetwork` of **parts** (mass, material, temperature `T`, optional `power`, `area`, `h`) joined by links. Phase change **holds the temperature** (273.15 K, 373.15 K) until the latent heat is paid. `strengthFactor(material, T)` gives what is left of the cold strength (about 40 % at 873 K for steel). There is no pressure model here: use `GasVolume` and a link.

## Steps
1. `net.addPart({ name, mass, material, T, power?, area?, h? })`; materials from `HeatLibrary`.
2. Join parts (`net.join`, `wallConductance`); give `area` and `h` for loss to the ambient.
3. `net.step(dt)` (2–10 Hz is enough for steel parts).
4. React to `heat:phase`, `heat:over`, `heat:ignite`.
5. Heat from friction: attach a part to a body (`attach`); more in `ferret-physics-links`.

## Check afterwards
Boiling 1 kg on 2 kW takes about 170 s to the boil and 1130 s to boil off; energy closes unless you set `T` by hand.

## What usually goes wrong
- Temperature never changes: no source, no link, no `area` and `h`.
- Phase never changes: the material has no `melt` or `boil`, or the plateau is still being paid.
- Energy does not close: `setTemperature` by hand, or a held part exchanging with the boundary.
- A held bar never breaks: no `sigmaMax`, or the rise is below `σ/(E α)`.

## Files

- `reference/heat.md` — Temperature of parts, conduction, convection and radiation, phase change with latent heat, thermal expansion and stress, heat from friction, and strength that falls as steel gets hot.
- `reference/api-physics-heat.md` — every export of `@ferret/physics-heat` with signature and doc comment
- `reference/commands.md` — 7 commands of these packages with their arguments
- `recipes/fire-and-heat.md` — Eight recipes: boil a pot, a beam in a fire, a pressure cooker, a kettle on a breaker, a cold pack, thermal runaway, an overloaded wire, a glowing brake disc.
- `recipes/boiler-house.md` — A fire heats a boiler, steam drives an engine, a generator on the shaft lights a lamp. Four capabilities, three links, one energy account that must add up.