Mineral Oil vs Air: Thermal Conductivity & Cooling Performance Comparison
1. Thermal Conductivity (W/m·K)
| Medium | Thermal Conductivity | Meaning |
|---|---|---|
| Air | ~0.024 | Very low heat transfer |
| Mineral Oil | ~0.12–0.15 | About 5–6× better than air |
Conclusion:
Mineral oil transfers heat better than air through direct conduction.
2. Heat Capacity (kJ/kg·K)
| Medium | Heat Capacity | Meaning |
|---|---|---|
| Air | ~1.0 | Low heat storage |
| Mineral Oil | ~1.6–2.0 | Can absorb more heat per unit mass |
Conclusion:
Mineral oil absorbs more heat before increasing temperature.
3. Convection (Cooling by Moving Fluid)
Air
- Very low viscosity → moves easily
- Natural convection is strong
- Fans blow heat away efficiently
Air = Good for passive cooling
Mineral Oil
- High viscosity → moves slowly
- Natural convection is weak
- If not pumped, heat accumulates near the chip
Oil = Poor natural convection unless circulated
4. Real-World Cooling Performance
With active flow (fan/pump)
Mineral Oil > Air
- Lower operating temperature
- Used in oil-cooled servers & transformers
With no movement (sealed container)
Mineral Oil < Air
- Heat gets trapped around components
- Components overheat in small electronics
- Can cause long-term damage to chips & capacitors
5. Final Conclusions
For passive cooling:
Air cools better because it convects well.For active cooling (oil pump or circulation):
Mineral oil cools better due to superior conduction & heat absorption.For small electronics in still oil:
Mineral oil can cause overheating, because heat cannot escape from the local area.
cool
Can a Normal Computer Fan Run in Mineral Oil?
✅ 1. Yes, a standard PC fan can operate in mineral oil
- Mineral oil is non-conductive → does not short-circuit electronics.
- Many hobbyists run oil-submerged PCs with normal fans.
- Brushless DC fans generally continue spinning fine in oil.
⚠️ 2. BUT: The fan's speed will decrease a lot
Reason:
- Oil is ~800× denser than air.
- The blades have to "push" thick oil → heavy resistance.
Typical results:
- A 120 mm fan normally spins at 1200–2000 RPM in air.
- In mineral oil, it may drop to 100–300 RPM (or even stall).
So it moves oil, but slowly.
⚠️ 3. Fan lifespan will be shorter
Problems you may encounter:
- Motor works harder → more heat.
- Oil may seep into bearings → increase friction.
- Rubber seals may swell over time.
It may still last months to years, but not as long as in air.
⚠️ 4. The fan moves OIL, not AIR
In oil:
- No airflow.
- Instead you get liquid circulation, which is good for cooling.
But:
- Movement is much slower.
- Large fans are more effective than small ones.