2. VAPL CHILLER SPECIFICATION
TOTAL NUMBER OF UNITS = 02
MAKE :- DAIKIN
MODEL NUMBER :- PFS1101-5103DARY
TYPE :- SINGLE SCREW WATER COOLED CHILLER
CAPACITY :- 500 TR (+5 to +10 Deg. C.)
CONNECTED LOAD :- 374.2KW
REFRIGRENT :- R134a
10. SINGLE SCREW COMPRESSOR
The Compressor consist of two cast iron casting which are bolted together . Stator
rotor
The First casting which is main casting of the compressor comprises of three rotating
parts a main rotor with helically screw threads and two identical toothed wheels . The two
wheels owing to their shapes are known as star rotors.
They are locked in a single phase diametrically opposite each other side of the main screw
rotor , with their axes at right angles to the main rotor axis .
The star rotor shafts are supported at each end by taper roller bearings.
The main screw rotor driven by a 3 phase 2 pole motor ( enclosed in the second casting )
imparts a freely rotating motion to the star rotors as it rotates . Together perform the
compression function .
The single semi hermatic screw compressor uses the suction gas coming from the evaporator
to cool the motor the gas flows through the electric motor , cooling the windings before
entering the suction ports .
11. COMPRESSION PROCESS
SUCTION
PROCESS 1
SUCTION
PROCESS 2
COMPRESSION DISCHARGE
Suction process 1
In this view clearly showing ,
as flute a assumes the position
Of flutes b and c its volume increases ,
inducing suction vapor to enter the flute.
Suction process 2
This coincides with each other flute being
progressively sealed by the main rotor .
Once the flute volume is closed off from
suction chamber, the suction stage
of the compression cycle is complete
COMPRESSION
As the main rotor turns , the
volume of gas trapped within
the flute Is reduced as the
length of the flute shortens
and compression occurs .
DISCHARGE
As the star rotor teeth approaches the
end of a flute, the pressure of the Trapped
vapor a maximum value occurring when
the leading edge of the Flute begins to
overlap the triangular shaped discharge port
12. REFRIGERATION CYCLE OPERATION
Low temperature and pressure vapor refrigerant coming from the evaporator first cools the compressor motor winding as it
enters the compressor .During the compression process, the suction vapor refrigerant is mixed with the oil that helps to seal
and lubricate the compressor rotors.
The high pressure refrigerant and oil mixture then passes through the oil separator where the mixture will be separated. Once
separated, oil is returned to the compressor and the high pressure and temperature gas refrigerant is discharged into the
condenser.
Inside the condenser, the discharged gas is distributed across tubes surface. Crossing the condenser’s tubes, the vapor
refrigerant DE superheats and condenses. The heat is rejected to the condenser water and the high pressure sub-cooled liquid
refrigerant then flows through the expansion valve and changes into a low pressure, low temperature, and liquid refrigerant.
The expansion valve measures the correct amount of refrigerant that enters the evaporator and is equally distributed along
the tube controls in the evaporator. The evaporator water is chilled as heat is transferred to the liquid refrigerant. During this
heat exchange process, the liquid refrigerant is changed into a low pressure superheated vapor. The low pressure superheated
vapor then returns to the compressor and going through a new refrigeration cycle.
13. EVAPORATOR
EVAPORATOR IS MAIN PART OF CHILLER , EVAPORATION OF REFRIGRENT OCCUR IN
EVAPORATOR .
EVAPORATOR REFRIGRENT LIQUID ENTER AND DISTRIBUTED IN EVAPORATOR TUBES
AND IT COOLS THE WATER FLOOWING IN EVAPORATOR TUBES . THE EVAPORATOR IS SHELL
AND TUBE TYPE WITH THE REFRIGRANT IN THE SHELL AND THE WATER INSIDE THE TUBE .
THE REFRIGRENT VAPOUR GENRATED IN THE EVAPORATOR FLOW TO THE SUCTION
END OF THE COMPRESSOR AND THAT REFRIGRENT ALSO PROVIDE COOLING TO
COMPRESSOR MOTOR .
14. CONDENSER
COMPRESSED REFRIGRENT VAOUR DISTRIBUTED IN CONDENSE
ACROSS TUBES .
COOLING TOWER WATER CIRCULATING IN CONDENSER TUBES ,
ABSORB HEAT FROM THIS REFRIGRENT AND CONDENSE IT . THE EVAPORATOR IS
SHELL AND TUBE TYPE WITH THE REFRIGRANT IN THE SHELL AND THE WATER INSIDE
THE TUBE .
CONDENSER USED TO REMOVE HEAT FROM REFRIGRENT , IT IS REMOVE FEFRIGENT HEAT
THROUGH COOLING TOWER CIRCULATING WATER .
15. Each screw compressor is connected to a tank (oil separator) that separates and
collects the oil carried by the discharge gas.
OIL SYSTEM CONTROL
The discharge gas pressure pushes the oil into the compressor where, after
passing through a high capacity filter, is conveyed to the main injection port
for compression sealing and lubrication of all moving parts
During the compression, the oil mixes with the discharge gas before being
conveyed again into the oil separator to re-start the cycle
The oil flow is granted by the pressure difference created between the condenser and the
evaporator. This difference depends on the cooling water and evaporator water temperatures.
During the start-up it is vital to establish the appropriate temperature difference quickly by
checking the right cooling water temperature.
16. HEATING ELEMENT
The compressor and the oil separator are provided with resistances for heating the
compressor and the oil in the separator in order to prevent the migration and the
condensation of the refrigerant during unit shutdown.
The auxiliary circuit should be energized for at least 12 hours prior to starting the
compressor. The compressor and oil temperatures should be sufficiently high before
starting the system, to minimize lubrication problems and liquid blow risk.
The microprocessor monitors the oil temperature directly and inhibits the compressor
starting if the oil temperature is not 5°C higher, at least, than the evaporating saturation
temperature.
In that condition the compressor status will be: “Off: Oil Heating”. For granting the good
operation of the heating resistances, regularly verify their power input.
17. CAPACITY SENSOR
The Capacity sensor spring loaded piston sense the movement of the capacity modulation
Slide piston of the compressor .
The Capacity sensor piston inserted into position A .
As the Capacity Modulation moves , it changes the displacement of capacity sensor
spring piston .
The Amount Of displacement made by the spring piston is converted into a
electrical signal and sent to chiller microprocessor .
Signal Output To
PLC Chiller
Spring Piston
(Connected to Compressor
capacity valve )
18. OIL SEPRATOR
WHEN OIL INJECTED INTO COMPRESSOR ROTOR AND IT MIXES WITH
COMPRESSED REFRIGRENT AND THAT DISCHARGE DIRECTLY TO OIL
SEPRATOR .
OIL AND REFRIGRENT MIXTURE DISCHARGE INTO THE OILSEPRATOR
BY CNTRIFUGAL FOCRE AND COLLECT ON THE WALL OF THE CYLINDER
DRAIN TO THE BOTTOM OF THE OIL SEPRATOR CYLINDER .
THE ACCUMULATED OIL AND DRAIN OUT OF THE CYLINDER AND
COLLECTED IN THE OIL SUMP AND GAS INTO THE CONDENSER .
19. Compressor Load Unload Valve
Two valves used in compressor Load and unload valves.
Compressed vapor flowing in to and out of the cylinder governs
piston movement, and is controlled by the load and unload
solenoid valves.
Load , Unload solenoid valve base on cooling system requirement .
For loading the compressor load valve should be open.
For unloading the compressor unload valve should be open .
The pressurized vapor flow then enters the cylinder and,
with the help of the lower suction pressure acting on the face of the
unloader valve, moves the slide valve over the rotors
toward the suction end of the compressor.
25. EXPANSION VALVE
Expansion Valve directly controlled by a refrigerant level sensor placed on
the condenser .
This system control the refrigerant liquid level , to grant adequate
operation of the expansion valve completely flooding the integrated sub
cooling section of the shell and tube condenser .
Rise pressure across the servo and PMFH opens allowing more refrigerant
flow and vice versa as the liquid level in the float drops .
When chiller under high pressure EVM closes to override the operations
of the PMFH to prevent more refrigerant from flowing into the
evaporator , to lover the evaporator pressure .