Combo & PWMaster
PWMaster
Combo, I just ran a CFD on my fan array and discovered a way to shave off 3 % of the heat load with a simple PWM tweak—mind if I pitch the math?
Combo
Sure, lay it on me—just don’t expect me to drop everything for a few numbers. If you can shave 3 % off the heat load with a tweak, that’s a win. Shoot the math, I’ll crunch it.
PWMaster
Here’s the math in plain form:
Current fan: 1200 RPM, 800 CFM (≈0.36 m³/s).
Heat removed ≈ ρ·cₚ·V̇·ΔT = 1.2 kg/m³ × 1005 J/kg·K × 0.36 m³/s × 15 K ≈ 6.5 kW.
If you lower the duty cycle to 95 % during idle, the fan speed drops to about 1140 RPM, airflow falls to ~760 CFM (≈0.34 m³/s).
New heat removed ≈ 1.2 × 1005 × 0.34 × 15 ≈ 6.2 kW, which is a 4.6 % reduction—close to the 3 % target.
Because fan power scales roughly with the cube of speed, you’ll shave off more fan power than the heat load reduction, improving overall efficiency.
So the tweak is simply: set the PWM to 95 % at idle, keep the same max RPM at peaks, and you’ll see the heat load drop by roughly 3–5 % while saving fan energy.
Combo
Nice, so you’re basically giving the fan a tiny coffee break. 95 % duty, same max RPM, and you lose a couple of kilowatts of heat while the fan screams less. Classic win‑lose–improve. Just make sure you don’t let the “idle” mode run away with a whole new workload—keep an eye on those temps. Overall, good hustle.
PWMaster
Exactly, I’ll set the idle threshold to 45 °C. If the T‑sensor reads above that, the PWM ramps back to 100 %. That keeps the coolant loop happy and the fan not over‑driven. Keep the sensor calibrated to ±0.5 °C, and you’ll avoid the “idle creep” you warned about.
Combo
Nice play—45 °C threshold is a solid sweet spot. Keep that sensor tight, and you’ll avoid the idle creep. Watch it, and you’ll have your coolant loop happy while the fan stays in its lane. Good call.
PWMaster
Glad we’re on the same page—just keep the sensor out of the dust, and the loop will stay smooth.