Publicité
Les langues disponibles
Les langues disponibles
How it works
In the ice makers the water used to make the ice
is kept constantly in circulation by a water pump
which primes it to the spray system nozzles from
where it is diverted on the inverted molds of the
evaporator (Fig. A).
A small quantity of the sprayed water freezes into
ice; the rest of it cascades by gravity into the
sump assembly below for recirculation.
FREEZING CYCLE (Fig. B)
The hot gas refrigerant discharged out from the
compressor reaches the condenser where, being
cooled down, condenses into liquid. Flowing into
the liquid line it passes through the drier/filter,
then it goes all the way through the capillary tube
where it looses its pressure.
Next the refrigerant enters into the evaporator
serpentine (which has a larger diameter then the
capillary tube) and starts to boil off; this reaction
is emphasized by the heat transferred by the
sprayed water.
The refrigerant then increases in volume and
changes entirely into vapor.
The vapor refrigerant then passes through the
suction accumulator (used to prevent that any
small amount of liquid refrigerant may reach the
compressor) and through the suction line. In
both the accumulator and the suction line it
exchanges heat with the refrigerant flowing into
the capillary tube (warmer), before to be sucked
in the compressor and to be recirculated as hot
compressed refrigerant gas.
The freezing cycle is controlled by the evaporator
thermostat which has its bulb in contact with the
evaporator serpentine.
The electrical components in operation during
the freezing cycle are:
COMPRESSOR
WATER PUMP
FAN MOTOR (in air cooled version)
The refrigerant head pressure is gradually
reduced from a value of approx. 9,5 bar at the
beginning of the freezing cycle with the unit at
21°C ambient temperature, to a minimun value
of approx. 6,5 bars just at the end of the freezing
cycle few seconds before the starting of the
defrost cycle.
The declining of the pressure is relied to the
reduction of the evaporating pressure, caused
by the progressive growth of the ice thickness on
the inverted molds and to the flow of air drown
through the air cooled condenser by the fan
motor.
PRINCIPLE OF OPERATION
The above values are in relation as well to the
ambient temperature of the ice maker site and
they are subject to rise with the increase of this
temperature.
At the start of the freezing cycle the refrigerant
suction or lo-pressure lowers rapidly to 1.0 bar
then it declines gradually - in relation
with the growing of the ice thickness - to reach,
at the end of the cycle, approx. 0,7 bar
with the cubes fully formed on the molds.
On the models water cooled version the hi-
pressure controls is used to intermittently
energize a water solenoid valve located on the
water supply line to the condenser.
DEFROST OR HARVEST CYCLE (Fig. D)
When the temperature of the evaporator
thermostat, in contact with the evaporator
serpentine, drops to a pre-set value it changes
its electrical contacts energizing the following
components:
COMPRESSOR
WATER INLET SOLENOID VALVE
HOT GAS SOLENOID VALVE
The incoming water, passing through the water
inlet valve and the flow control, runs over the
evaporator platen and then flows by gravity
through the interstices down into the sump/
reservoir (Fig. C).
The water filling the sump/reservoir forces part
of the surplus water from the previous freezing
cycle to go out to the waste through the overflow
pipe. This overflow limits the level of the sump
water which will be used to produce the next
batch of ice cubes.
Meanwhile the refrigerant, as hot gas discharged
from the compressor, flows through the hot gas
valve directly into the evaporator serpentine by-
passing the condenser.
The hot gas circulating into the serpentine of the
evaporator warms up the copper molds causing
the harvest of the ice cubes. The ice cubes,
released from the inveted molds, drop by gravity
onto a slanted cube chute, then through a
curtained opening they fall into the storage bin.
When the temperature of the evaporator
thermostat bulb reaches the value of +3 ÷4°C
their electrical contacts move back to the previous
position activating a new freezing cycle and
deenergizing both the hot gas and the water inlet
valves (closed).
NOTE. The length of the defrost/harvest
cycle (not adjustable) changes according
to the ambient temperature (shorter for hi
ambient temperature and longer for low
one).
8
Publicité
