C
HAPTER
4
DESCRIPTION
4 . 1
O p e r a t i n g p r i n c i p l e
In the dryers described in this manual a refrigerant circuit cools the aluminium surface of an evaporator through which the
humid compressed air to be dried flows. The air cools, condensing the water vapour it contains, which is then separated and
discharged.
Before leaving the plant, the cold compressed air passes through an air/air exchanger in which it heats up while cooling the
humid compressed air entering the dryer.
If the cooling output generated by the unit is greater than that required, a solenoid valve is activated, located on intake to the
compressor and equipped with an additional calibrated hole: closure of the solenoid valve forces the refrigerant to pass
through the additional calibrated hole, reducing the flow rate of the refrigerant processed by the compressor. This enables a
reduction in cooling output and electrical consumption.
On units with capacity step control, if the cooling output is still too high, the cooling compressor will be shut down, to
exploit the thermal mass of the aluminium heat exchanger.
4 . 2
O v e r a l l d i m e n s i o n s
For the drawings, consult the annexes to the manual.
4 . 3
M i n i m u m d i s t a n c e s f r o m t h e w a l l s o f t h e i n s t a l l a t i o n
r o o m
For the drawings, consult the annexes to the manual.
4 . 4
A i r a n d r e f r i g e r a n t c i r c u i t s
For the drawings, consult the annexes to the manual.
4.4.1
Air circuit
The air/air heat exchangers and the evaporator are of compact type in aluminium.
The warm and moist compressed air enters the dryer through the air/air exchanger; here, the air is precooled by the cold dry
compressed air at the outlet of the air/refrigerant exchanger or evaporator. The precooled air then enters the evaporator,
where it is cooled further, transferring heat to the refrigerant, which consequently evaporates.
At the point, the compressed air is in a saturated condition and it entrains the condensate resulting from the cooling process.
The condensate is separated from the air flow by a metal mesh (AISI304) demister and it falls due to gravity onto the bottom
of the thermal module, from where it is collected and expelled.
The dry cold air flows a second time through the air/air exchanger where it warms up and cools the humid air entering the
dryer.
This air/air exchanger both reduces the amount of energy required to dry a given flow of air and also has the benefit of
reducing the relative humidity thereby avoiding the risk of the formation of condensate at the dryer outlet.
4.4.2
Refrigerant circuit
The refrigerant gas is forced by the compressor into the condenser, where it changes from the gaseous to the liquid phase.
The condenser is a finned core heat exchanger and it is cooled by an air flow produced by a fan unit.
Downstream from the condenser, the liquid refrigerant flows through a lamination device that reduces its pressure.
The refrigerant then enters the evaporator where it cools the compressed air; when it flows out of the evaporator it is in the
form of a saturated vapour that entrains a small quantity of liquid.
The refrigerant is then sucked into the compressor again and the cycle is repeated.
If the cooling capacity produced by the unit is greater than the required cooling capacity, a solenoid valve trips to reduce the
capacity of the circuit. This capacity control reduces the cooling capacity of the unit and also reduces energy consumption.
If the cooling capacity remains too high even with capacity control active, the refrigerant compressor will be stopped and the
thermal mass of the aluminium exchanger will be utilized for cooling purposes.
4 . 5
E l e c t r i c a l c i r c u i t
The drawings are given in the annexes to the manual.
