Thermal Conflict

Structural question — how does temperature change one assembly’s behaviour over time?

A warm assembly and a cool one are not two designs. They are the same design at two points on a curve. This week measures the curve.

The cooling boundary#

Heat moves from the warmer region to the cooler one until the difference is gone. An assembly that leaves the bench warm therefore carries a gradient — warmest at the interior layer that supplied the heat, coolest at the outer surface losing it to the room. There is no single temperature to record, only a temperature and the place it was taken.

The gradient matters because it moves water. Vapour driven out of a warm layer travels outwards, meets a surface below its dew point — usually the inner face of the outer layer, or the inside of a wrapper — and condenses there as liquid. This is moisture arriving at the boundary from inside the assembly, which is a different arrival from the migration Week 4 records, and it is invisible from outside.

Time then does the rest. The gradient collapses within minutes; the liquid it deposited does not leave. A specimen measured at equilibrium reads as unremarkable while carrying the whole thermal history of the twenty minutes before it. The course treats the assembly as three lumped thermal zones rather than a continuous field — a teaching simplification, not a claim about how heat actually distributes.

Investigation#

At the thermal timeline station, one specimen condition is observed at three fixed time points: on assembly, at ten minutes, and at twenty. Nothing is observed between them. At each point, record a temperature and the location it was taken from, the condition of the inner face of the outer layer, and where liquid is visible.

Run an ambient control alongside. Without it you cannot separate what temperature did from what twenty minutes would have done anyway.

Failure condition#

The inner face of the outer layer is wet while its outer face is still dry. The boundary has been loaded from inside, and the specimen looks intact until it is opened.

What leaves the session#

A Thermal Comparison: three timed observations of one condition against an ambient control, each with its measurement location, and a statement of which change you attribute to temperature rather than to elapsed time. The Failure Autopsy reasons from sequences, and this is the first artefact that hands it one with times on it.