Sweating is an interface flux under feedback control. A thermal load raises core temperature until it clears the EDAR sweat-switch threshold; evaporative cooling then regulates temperature, dropping the temperature-versus-load slope from 2.0 to 0.77. Above the maximum sweat capacity the flux saturates and temperature runs away — the heat-stroke limit.
A thermal load raises core temperature until it crosses the EDAR sweat-switch threshold; the evaporative interface flux then regulates temperature, dropping the temperature–load slope from 2.0 to 0.77, until capacity saturates and temperature runs away.
Sweating is recruited, not always on
A thermal load raises core temperature. The sweat gland is governed by the EDAR switch and stays off until the thermal drive clears its threshold; in this run recruitment begins at a load of about 0.3. Below that the skin sheds heat only passively.
Once recruited, the gland secretes in proportion to the temperature error, and evaporative cooling carries heat away as an interface flux. This is a feedback controller engaging at a set-point, not a linear radiator.
The flux regulates — until it can’t
The regulation is visible in the slope of core temperature against thermal load. Before sweating it is about 2.00; once the evaporative flux engages it falls sharply to about 0.77, the controller actively flattening the temperature rise.
Above the maximum sweat capacity the flux saturates: it can remove no more heat, and the slope climbs back to about 2.00 as temperature runs away. That runaway above capacity is the substrate's picture of the heat-stroke limit.
Grades
The thresholded onset, the flux-regulated slope drop, and the runaway above capacity are simulation-verified shapes [V] Simulation-verified. The absolute set-point (37 °C) and the absolute sweat rate are cited/open [O] Open (obstacle stated): they need per-gland output and body heat capacity as inputs.