Box Potato Store Air Discharge Ducting

Square or Round - Which Works Best?

Farm Electronics has gained much experience over 30 years of the most effective air distribution in Box Potato Stores.

We choose to supply square galvanised air ducts in preference to the round "Spiral", off the shelf, HVAC ducting provided by the majority of our competitors.

There are two primary reasons for our choice.

Firstly Fan Efficiency.

Round ducting is mostly supplied at the same diameter as the fan it is fitted to. Over a typical length of around 4 to 5m of round ducting air friction resistance will reduce the fan motor running efficiency, and therefore increase the running costs of the fan.

Square ducting has a 65% greater cross sectional area, therefore reducing air friction and back pressure on the fan motor.

Example:

Secondly Airflow Direction.

When air leaves an axial fan it is in the form of a corkscrew air flow. This effect will cause the air to "Entrain" or veer, to the right, or the left of the Potato Store as it leaves the discharge duct dependant on the rotation direction of the fan motor. On standard round ducting this effect is very bad, as there is nothing to disrupt the corkscrewing of the air flow, due the smooth wall nature of the round ducting. Often on round duct systems the outlet bend will be set at an angle to throw the air to the side of the store. Unfortunately in practice this does little to counteract the air entrainment.

On square ducting the corkscrew air flow is naturally disrupted by the square corners and the fact the air has to occupy the larger duct area. In addition to this we fit "air straightener baffles" and adjustable air outlet "Guide Vanes" within our specially manufactured outlet hood to maximise the ability to get a straight air flow into the Potato Store.

Example: