The role of the refrigeration dryer is to cool the compressed air in order to condense the water vapor it contains. At the coldest point of the system (which corresponds to the dew point temperature) the condensed water, i.e. liquid, is evacuated from the dryer by an automatic drain. The air is then heated by passing in counter-current through the air/air exchanger with the hot air entering the exchanger and is then distributed dry in the network. This thermodynamic system must balance the incoming heat (flow rate and temperature of the compressed air) with the cooling power of the dryer (cooling power and temperature of the condenser) in order to maintain the desired dew point.
The selection of the dryer should therefore take into account :
- a dew point of +3°C for a refrigeration dryer is a minimum with a certain safety margin. Below this value, the condensed water can freeze in the heat exchanger and cannot be drained off,
- the flow rate, pressure and maximum temperature of the compressed air to be treated
- the ambient temperature conditions of the place where it will be installed,
the maximum permissible dew point (ISO quality 8573-1) for the process and configuration of the client network.
How to determine the right dryer?
For each parameter a correction factor is applied. The nominal parameter has a factor of 1. Any deviation from this parameter results in a decrease or increase in the throughput capacity of the dryer.
► Let's take an example
An ACT EVO 1000 dryer has a treatment capacity of 1000 m3/h at nominal conditions (blue boxes in the tables below)
What would be its corrected capacity with the following parameters :
Compressed air pressure = 8 bar
Ambient air temperature = 30°C
Compressed air temperature = 40°C
Dew point = +5°C
Corrected flow rate = 1000 x 1.05 x 0.96 x 0.83 x 1.09 = 1000 x 0.91= 910 m3/h
On the other hand, if we want to select a dryer that can treat 1000 m3/h under these same conditions, we must then reduce this flow to the nominal conditions:
Equivalent nominal flow rate = 1000 / 0.91 = 1100 m3/h
Here the dryer to be selected will be the ACT EVO 1130 model
