Coolant temperature a loop settles at, the fan speed a target temperature needs, and optionally the noise at that speed.
A radiator moves heat in proportion to the difference between coolant and incoming air:
Q = q · (Tcoolant − Tair). Solving for the coolant gives the
equilibrium. q is the dissipation in W/K.
q depends on the air actually passing through the core, not on fan rpm as such.
Airflow per fan is CFMmax · derate · rpm/rpmmax with the radiator
derate from the airflow tool (0.62, or 0.72 for pressure-optimized blades, ×1.12 push-pull, less for
thicker cores). Per 120 mm segment at 27 mm: q = 8.5 W/K · (airflow / 45 CFM)0.6.
Heat transfer over fins scales with roughly the 0.6 power of velocity.
| Core | Airflow factor | Fin area factor | Net at same rpm |
|---|---|---|---|
| 22 mm | 1.06 | 0.93 | 0.96 |
| 27 mm | 1.00 | 1.00 | 1.00 |
| 38 mm | 0.90 | 1.15 | 1.08 |
| 45 mm | 0.84 | 1.22 | 1.10 |
| 60 mm | 0.76 | 1.30 | 1.10 |
Thick cores gain fin area but lose airflow; at low rpm the net is close to zero. With fans off, natural convection is taken as 1 W/K per segment.
The band is ±15 % on q: fin density, coolant flow and preheated case air.
Pump speed matters little above roughly 1 l/min.
Die temperatures sit above the coolant by the block and TIM delta, typically 25 to 45 K under load.
Noise, if a dB(A) rating is given: Lmax + 50 · log₁₀(rpm/rpmmax) added on an
energy basis to a 6 dB(A) motor and bearing floor, plus 10 · log₁₀(fan count). Same model as the noise tool.