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Automatic hatches play an important role in the modern garlic drying process. The garlic HVAC processor optimally dr drying by sucking up the driest (and cool) air; Outdoor mixed air – in door

Air mixing unit of automated hatches and shutters for operating the air flow outdoor / inside.

Extended roof creating a space on the side to suck the air.

The easiest way is to suck 100% via an aperture to outside. As long as the air from the product is more humid (higher AMC than the incoming air) drying takes place. a smaller difference (Delta-AMC) decreases the drying speed; less air is needed.

In the case of a small difference between the AMC outside and the AMC inside (smaller Delta-AMC), the supply of outdoor air has less effect on drying; the product becomes drier. It may also be that the moisture content of the outside air increases. It is then less economical to suck cold outdoor air and warm it up.

An automatic steering hatch can thus suck more and more air inside. It takes less energy to dispose of the last moisture content. It also prevents too humid outdoor air which makes the product moist again.

Mixing hatch which mixes 50% outdoor air with 50% inside air.

Suction hatches can be automatically opened and closed by an engine with an axle and tooth heugels.

Engine with axle to open or close the shutters automatically

The rotation of the axle causes the toothed bar to slide in or out

The toothed bar opens or closes the hatch.

It is practically not possible to continuously measure the incoming and outgoing T°, the RMC, the AMC and calculate the difference. By measuring the incoming and outgoing air with a combined T° and RMC sensor, a processor can determine the AMC and also the difference (Delta-AMC).

A desired Delta-AMC can be entered into the processor, determining what is most economical to suck and warm up 100% outdoor air.
Example Delta AMC=2g/kg
With a measured difference of 1 gram, the hatch is opened 50%
With a measured difference of 1.5 grams 75%
With a difference of 2 gr or more, the shutters are 100% open.

In addition to drying air, the temperature of the air sucked in is also important.
The incoming air must not exceed the T° you set.
When the outside temperature is too high, too hot air is blown through the product.
The hatch will then close gradually, with the maximum incoming T° not exceeded.
By then sucking cooler indoor air, the temperature of the mixed air becomes lower.
The moist product can then be dried with a limited amount of outdoor air.
When too much air is sucked within, only moist air is sucked back and no drying takes place anymore.
The drying process is then interrupted and can restart on a time clock after a set time.

  1. Wanneer de buitencondities gunstiger zijn geworden, wordt het droogproces weer gecontinueerd.
  2. If not, the drying stops after the minimum  set  turn  time.