Earth-to-air Heat Exchanger
This can be done by an earth warming pipe ("ground-coupled heat exchanger"), usually about 30 m to 40 m long and 20 cm in diameter, typically buried about 1.5 m below ground level. In Germany and Austria this is a common configuration for earth to air heat exchangers.
In high humidity areas where internal condensation could lead to fungal / mould growth in the tube leading to contamination of the air, several measures exist to prevent this.
- Ensuring the tube drains of water.
- Regular cleaning
- Tubes with an imbedded bactericide coating such as silver ions (non-toxic for humans)
- Air filters F7 / EU7 (>0,4 micrometres) to traps mould (of a size between 2 & 20 micrometres).
- UV air purification
- Use a earth to "water" heat exchanger, see below.
The pipes may be either corrugated/slotted to enhance heat transfer and provide condensate drainage or smooth/solid to prevent gas/liquid transfer.
Read more about this topic: Heat Recovery Ventilation
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