4
7425MUM651
Model: QBS
- Use and Maintenance Manual
Rev. 02
2
O
PERATION
A
ND
M
AIN
C
OMPONENTS
2.1
R
EFRIGERANT CIRCUIT
QBS chillers use a vapour-compression cycle in a refrigerant circuit that essentially consists of the
following components: evaporator, compressor, condenser, lamination device (capillary tube).
Evaporator:
heat exchanger (tube and fins) to enable heat exchange between the water and the
refrigerant liquid without them coming into contact with each other. The water is cooled when it
passes through the evaporator.
Compressor:
compresses the steam from the evaporator to send it to the condenser at a higher
pressure.
Condenser:
tube and fins exchanger to enable heat exchange between the refrigerant and the air; it
creates refrigerant gas condensation transferring the gas refrigerant condensation heat to the air
(which flows externally); high pressure refrigerant liquid is thus produced.
Lamination device:
reduces the pressure of the liquid refrigerant coming from the condenser, which
is then sent to the evaporator.
Thanks to these components,
the vapour-compression cycle
works as follows: the refrigerant liquid
evaporates in the evaporator, chilling the water; the refrigerant vapours are then aspirated from the
compressor, which compresses them and sends them to the condenser under high pressure; here,
thanks to a flow of forced air from the fans, the high-pressure refrigerant gas is cooled, making it
condensed and undercooled.
The flow of refrigerant liquid then passes through the lamination valve (thermostatic expansion
valve), which drastically reduces its pressure: the refrigerant liquid returns to the evaporator at a
reduced pressure where it again evaporates, taking heat from the water.
The refrigerant circuit also includes a
water pump
, which ensures the flow of water to be chilled by
evaporation, and the
fan
which ensures the condenser is cooled.
2.2
W
ATER CIRCUIT
The water circuit mainly consists of a pump, evaporator, tank.
The water flows into the evaporator first where it is cooled, then into the tank, and is then suctioned
by the pump which sends it to the system (see
Water diagram
section 11).
All QBS units have an open circuit with a tank at atmospheric pressure.
See chapter
11 Water diagram
.
2.3
F
AN
The fan forces air through the condenser fins to remove the refrigerant gas condensation heat,
therefore limiting the pressure inside the condenser.
QBS chillers are equipped with axial fans and have internal heat protection for the motor windings.
2.4
C
ONDENSATION CONTROL
When the ambient air temperature decreases, air flow cooling capacity increases slightly, causing a
reduction in pressure inside the condenser; to limit this decrease in condensation pressure from falling
below acceptable limits for good cooling circuit operation the fan stops temporarily.
