Designing Cooling &
Heating Systems

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Displacement ventilation for improved working conditions and higher productivity

Everyone knows heat rises so why doesn’t every factory owner and operator buy into this phenomenon for ventilation or air-cooling? The air saving (in fan energy) can be 20% over traditional air mixing systems. The company we helped found they improved working conditions and productivity increased as a result.

FSL designed ventilation for a soft drinks plant in the north of England using the effect of rising heat or ‘displacement’ air ventilation.

The ventilation system delivered airflows into the lower ‘occupied zone’ from 1.5 to 2.0 meters above the floor. Above this height the hot air released from the bottling equipment rose vertically upward to the roof extractor fans; no one occupied this space so the temperature was of little or no consequence. Air terminals were strategically located near to the staff operating stations to provide maximum benefit.

The design handling unit and roof fans for the 24/7 filling operation included variable speed drives to control the airflow entering the building. The target was to maintain ambient plus 4-6 OC inside during most of the year.

Reductions in ambient temperatures increased the cooling effect of the air entering the to a point where the staff became uncomfortable and there was a risk of condensation inside on cold surfaces. To avoid either of these situations occurring, recirculation of the hottest air drawn from the top of the building was mixed with air supplied.

Controlling the speed of both supply and extract fans enabled a positive internal pressure to be maintained. When the air entering from outside was very cold the supply fan speed reduced to a minimum setting extract fans were switched off.

In addition FSL proposed a contingency to de-stratify the air with fans mounted between the roof purlins.

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