Axial vs Centrifugal Fans — Airflow vs Pressure Comparison
Axial fans prioritize airflow (CFM) — ideal for low-resistance, straight-through cooling. Centrifugal fans prioritize static pressure (Pa) — essential for filtered enclosures, ducts, and dense systems. The choice depends entirely on system resistance.
| Feature | Axial Fan | Centrifugal Fan |
|---|---|---|
| Airflow Direction | Straight through (parallel to shaft) | 90° turn (inlet axial, outlet radial) |
| Max Static Pressure | 30-200 Pa | 100-1000+ Pa |
| Max Airflow | Very high (5000+ CFM possible) | Moderate (typically 500-2000 CFM) |
| Efficiency | 70-85% | 60-85% (backward curved highest) |
| Noise Character | Broadband, wind-dominant | Tonal, blade-pass frequency |
| Size for Same CFM | Smaller diameter, thicker | Larger housing, more depth |
| Cost | $ (Lower) | $$ (Higher) |
| Best For | Open chassis, low resistance | Filters, ducts, high resistance |
🏆 Verdict
If your system has <50 Pa resistance: axial. 50-100 Pa: either (compare efficiency). >100 Pa: centrifugal. When in doubt, measure the pressure drop across your system.
❓ FAQ
Can I use an axial fan with a filter?
Yes, but derate airflow by 40-60%. A 100 CFM axial fan behind a standard filter may only deliver 40-60 CFM. If your filtered CFM requirement is met, axial is fine. Otherwise, switch to centrifugal.
Why do servers use axial fans?
Server chassis have very low airflow resistance (open front-to-back path). Axial fans provide maximum CFM per unit volume, which is exactly what dense server layouts need. The trade-off is noise — server fans run at high RPM.