Both coolers at the same heat load: what each dissipates, the coolant temperature over fan speed, and the fan speed and noise each needs for the same temperature. Calculated from radiator size, core thickness and the stock fans' datasheets, not measured.
| be quiet! Pure Loop 3 | 280mm | Fractal Design Lumen S28 v2 | |
|---|---|---|
| Radiator | 280 mm | 280 mm |
| Core thickness | 52 mm | 27 mm |
| Stock fans | 2 × Pure Wings 3 140mm PWM high-speed | 2 × Aspect 14 PWM |
| Fan rpm, datasheet | ? – 1800 | 500 – 1700 |
| Pump | 5500 rpm max | 4000 rpm max |
| Tubing | 400 mm | 400 mm |
| Dissipation at max rpm | 21.6 W/K | 22.6 W/K |
| Coolant, 250 W, 30 °C intake | 41.6 °C | 41.1 °C |
| Noise at max rpm, all fans | 33.5 dB(A) | 38.5 dB(A) |
| K above intake | Pure Loop 3 | 280mm rpm | dB(A) | Lumen S28 v2 rpm | dB(A) | Quieter |
|---|---|---|---|---|---|
| 10.0 | not reachable | – | not reachable | – | |
| 12.5 | 1584 | 30.8 | 1385 | 34.1 | Pure Loop 3 | 280mm by 3.3 dB |
| 15.0 | 1169 | 24.3 | 1022 | 27.5 | Pure Loop 3 | 280mm by 3.3 dB |
| 17.5 | 904 | 19.0 | 790 | 22.1 | Pure Loop 3 | 280mm by 3.1 dB |
| 20.0 | 724 | <15 | 633 | 17.7 | Pure Loop 3 | 280mm by 2.7 dB |
| 25.0 | 499 | <15 | 500 min | <15 | both inaudible |
The Lumen S28 v2 dissipates 22.6 W/K against 21.6 W/K at max fan rpm. Across the range both can hold, the Pure Loop 3 | 280mm is quieter by about 3.1 dB at the same coolant temperature. That is outside the ±3 dB cross-brand uncertainty and should be audible. A cooler pinned at its fan's minimum rpm runs colder than the row asks; the comparison is then not at equal temperature.
A radiator moves heat in proportion to the difference between coolant and incoming air: Q = q · (Tcoolant − Tair).
q depends on the air actually passing through the core. Airflow per fan is CFMmax · derate · rpm/rpmmax
with the radiator derate (0.62, or 0.72 for pressure-optimized blades) times the core-thickness factor. 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 |
|---|---|---|
| 27 mm | 1.00 | 1.00 |
| 30 mm | 0.97 | 1.09 |
| 38 mm | 0.90 | 1.15 |
| 45 mm | 0.84 | 1.22 |
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.
Noise is the stock fan's curve plus 10 · log₁₀(fan count).
Air entering the radiator is case air, usually 5 to 10 K above room. Die temperatures sit above the coolant by the block and TIM delta, typically 25 to 45 K under load. Nothing here is measured; the same model runs in RadiatorTemp.