The science behind drying and climate control
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Everybody knows what is drying, but not everybody understands the physical process of drying and the lack of understanding of this process could lead to .

The physics behind drying and climate control

What is drying and what is the dew point?

Everybody knows what drying is, but not everybody understands the physical process of drying; failing to understand this process could result in the destruction of entire crops during the drying, curing and storing processes.

How do you dry hundreds of tonnes of onions, potatoes or other crops, and keep them dry during this kind of weather?

Barn in rain
A sad wet cow
Bare foot girl in the rain
A drenched field
Drenched horses
Soaking wet girls
Drenched and muddy fields
Very wet girl in the rain

Looking at these photos, it becomes clear that the processes of drying, curing and storing valuable crops require a good understanding of all these processes; it is not as simple as hanging clothes in the sun to dry.

Drying crops (onions, potatoes or other produce) is a process where the following parameters play a determining role:

  1. air temperature
  2. relative humidity of the air
  3. air pressure
  4. dew point
  5. temperature of produce to be dried
  6. amount of air that passes through the produce

The first four parameters are strictly related through the Laws of Physics.

The relations between these parameters are reflected in the MOLLIER DIAGRAM (an example shown at the bottom of this page).

In all these processes, the DEW POINT plays a determining role.

The complexity of all this is well reflected in the following statements that may all be true in certain circumstances:

Three confusing, but true, statements!

Which statement is true?


Ventilating something that is colder than the air:

Dries it under certain circumstances

Lady using a hair dryer

Think about a woman drying her hair with the warm air from her hair-dryer.

Makes it wet under certain circumstances.

Condensed cold bottle

Warm ambient air creating condensation on the soda bottle that just came out of the fridge.

Is this statement true?


Ventilating something that is warmer than the ventilated air:

Always dries !
With other words: colder ventilation air always dries!

Car window with condensation

With air conditioning (cooling the air), the condensation on the inside of the car windows is removed in a very efficient way.

Think about getting into your car, which has been drenched by a downpour. The car windows mist over, and to get rid of this layer of condensation, you put on the air conditioner You will notice that this does the job much faster than putting on the heating.

The dew point.

Now you realize that warm air sometimes dries and sometimes makes things wet.

Not understanding the reason behind this phenomenon could cost you your entire stored crop.

To understand this phenomenon, you have to understand what the DEW POINT is.

Next up: DEW POINT explained

Images showing the dismal humid circumstances during which the crop must stay dry ..... during months on end !

It is raining and foggy, close to 100% relative humidity, and the ambient temperature is almost at the DEW POINT. However, if you know what the DEW POINT is, you will understand that even in these circumstances, it possible to keep your crop dry.

very humid circumstances to keep crop dry

Very humid circumstances to keep a crop dry

very humid circumstances to keep crop dry

Very humid circumstances to keep a crop dry

the destruction of entire crops during the drying, curing and storing processes.

To mechanise your post harvest processes:
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