Whatever Type of Screw Chiller,
TopChiller Can Fulfill the Chiller Solution for You.
- Over 20 years of screw chiller manufacturing experience: TopChiller specialized in screw chiller design and manufacturing over 20 years
- Up to 24 months warranty time: TopChiller promise standard 12 months warranty can extend to 24 months covered all screw chillers
- Famous brand spare parts: Each screw chiller from TopChiller using world first class refrigeration spare parts
- Technical support& Training service: TopChiller can provide screw chiller installation and on-site commission service
- 8 Hours troubleshooting: We promise 8 Hours quick response to solve screw water chiller if the case of any screw chiller error or alarm
- Free screw chiller solution: TopChiller give all clients screw chiller and central chiller solutions free of charge
Why TopChiller Can Be a Reliable Chiller Factory
Your Premier Screw Chiller Manufacturer
As a professional screw chiller manufacturer, all screw chillers from TopChiller including air cooled screw chiller or water cooled screw chiller is equipped with original Bitzer brand or Handbell brand screw type compressor.
This kind of semi-hermetic screw compressor with 4 steps (100%-75%-50%-25%) of cooling capacity for energy efficiency, alongside a touchscreen PCL control system. A different refrigerant such as R407c, R134a, R410a, and R404a are available depending on the working condition and ambient temperature.
Each screw chiller manufactured by TopChiller with fully protection devices including :
Compressor inner protection, over current protection, high/low-pressure protection, over temperature protection, water flow protection, phase sequence/missing protection, low coolant protection,anti-freezing protection, exhaust overheat protection.
These full protection devices can make sure all screw chiller working without any alarm or error.
All screw chillers are with SIEMENS PLC program control system, a smart computer interface with big LED touching screen, self-diagnosis for easy operation and supervision.
Compared with air cooled screw chiller, water cooled screw chiller need external cooling tower and cooling pump running together.
As a professional screw chiller manufacturer, TopChiller has exported many screw chillers to the Philippines, Australia, New Zealand, Malaysia, Singapore, Indonesia, Chile, Mexico, Costa Rica, Brazil, Argentina, Colombia, South Africa, Nigeria, Saudi Arabia, Dubai, Spain, Italy, etc.
If you are waiting for a professional screw chiller supplier, TopChiller is your best choice in refrigeration filed. If you have any screw chiller inquiry, please do not hesitate to contact TopChiller sales to get a good price.
TopChiller: Your Premier Screw Chiller Manufacturer
Screw chillers having air cooled screw chiller and water cooled screw chiller. Compared with scroll compressor chillers, screw chillers with large cooling capacity for some certain industrial or commercial usage.
Both types of these two screw chillers are widely used for various industries applications such as HAVC, big building&hotel air conditioning, central chilled water supply, chemical processing, die casting,food&beverage processing, pet food, Pharmaceutical, plastic processing, automotive, energy&power project, packing, and printing…
Screw chiller expertise is common in all major industries, it uses the screw compressor to get this name. The utility of screw chiller has the advantages of large power, compact structure, stable operation, simple operation and wide application range, and is suitable for large air conditioners such as hotels, hotels, factories, hospitals, etc., especially in high-rise buildings with less load, and can display its uniqueness superiority.
Screw Chiller: The Completely Buying Guide for Importer
- What is a Screw Chiller?
- What is the difference between Screw Chillers and Reciprocating Chillers?
- Screw chiller working principle and flow diagram
- Features of water cooled screw chiller:
- Advantages of screw chillers
- Screw chiller applications:
- Some tips for selecting a correct screw chiller
- Why the screw compressor need the refrigeration oil or lubrication oil?
- Why TopChiller can your reliable screw chiller supplier?
- Common fault analysis of screw chillers
- Selection points and troubleshooting of screw chillers
- Installation and commissioning of screw chiller
1. What is a Screw Chiller?
A screw chiller is an industrial chiller with screw type of compressor.
Like all chilling systems, screw chillers are composed of an evaporator, compressor, condenser, expansion valve. What sets it different from other types of chillers is its screw type compressor, which uses two helical rotors that propel and compress the refrigerant vapor.
Because of less number of moving parts and the rotary motion, screw chillers are more durable and quiet. They are smaller and lighter and are a popular choice by the users.
Screw chillers can be applied in a variety of cooling applications and are reliable for heavy-duty performance under harsh conditions and environment.
2. What is the difference between Screw Chillers and Reciprocating Chillers?
Regardless of which type of compressor, all of them have one common function-converting a source of power into stored energy in the form of compressed air.
Simply speaking, a compressor sucks in enough air and decreases its volume. As a result both the temperature and pressure rises. Most air compressors either are reciprocating piston type or rotary screw type.
2.1 Reciprocating Chiller
A reciprocating compressor has a piston move downwards, reducing pressure in its cylinder by creating a vacuum.
This difference in pressure forces the cylinder door to open and bring gas in. When the cylinder goes back up, it increases pressure, thus forcing the gas back out. The up-and-down motion is called reciprocating motion.
There are a lot of moving parts like piston, piston ring, crankshaft, connecting rod, valves, etc. that causes lesser reliability and more chance of breakdown.
The internal temperature at which the pistons operate is around 150 to 200 Deg C. This is because of the friction generated by the contact of piston rings against the cylinder walls.
The space required by the piston compressor is more. Separated compressor compartment is needed for its noise and vibration.
Small compressors are air cooled but large machines from 30HP and above are only water cooled.
2.2 Screw Chillers
For a study of screw chillers, we must know something about the screw compressors.
The screw refrigeration compressor is a kind of rotary refrigeration compressor, and has both piston type and power type (speed type).
Features of screw compressors:
- 1) Compared with reciprocating piston refrigeration compressors, screw refrigeration compressors have a series of advantages such as high speed, lightweight, small size, small footprint and low exhaust pulsation.
- 2) The screw refrigeration compressor has no reciprocating mass inertia force, good dynamic balance performance, stable operation, small vibration of the machine base, and the foundation can be made smaller.
- 3) The screw refrigeration compressor has a simple structure, a small number of parts, and no wearing parts such as a gas valve and a piston ring. Its main friction parts such as a rotor and a bearing have high strength and wear resistance, and are lubricated. The condition is good, so the machining amount is small, the material consumption is low, the operation cycle is long, the use is relatively reliable, the maintenance is simple, and the operation automation is facilitated.
- 4) Compared with the speed compressor, the screw compressor has the characteristics of forced air transmission, that is, the displacement is almost independent of the exhaust pressure, and the surge does not occur at a small displacement, and is broad. High efficiency can still be maintained within the working conditions.
- 5) using the slide valve adjustment, can achieve energy stepless adjustment.
- 6) The screw compressor is not sensitive to the liquid inlet and can be cooled by injection. Therefore, at the same pressure ratio, the discharge temperature is much lower than that of the piston type, so the single-stage pressure ratio is high.
- 7) there is no clearance volume in the screw compressor, so the volumetric efficiency is high.
Working principle of screw compressor:
1. Inhalation process:
The screw-type intake side suction port must be designed so that the compression chamber can fully inhale, and the screw type air compressor has no intake and exhaust valve groups, and the intake air is only adjusted by opening and closing of a regulating valve.
When the rotor rotates, the space of the groove of the main and auxiliary rotors is the largest when it is turned to the opening of the intake end wall.
At this time, the space of the groove of the rotor communicates with the free air of the intake port, because the groove of the air is exhausted.
The air is exhausted in its entirety. At the end of the exhaust, the groove is in a vacuum state. When it is turned to the intake port, the outside air is sucked and flows into the groove of the main and auxiliary rotors in the axial direction.
Screw air compressor maintenance reminds that when the air fills the entire tooth groove, the air intake side ends face of the rotor turns away from the air inlet of the casing, and the air between the tooth grooves is closed.
2. Closure and transportation process:
At the end of the inhalation, the main and auxiliary rotors will be closed with the casing and the casing will be closed.
At this time, the air is not closed in the groove, that is, [closed process].
The two rotors continue to rotate, and the tooth peaks coincide with the groove at the suction end, and the mating surface gradually moves toward the exhaust end.
3. Compression and injection process:
During the conveying process, the engaging surface gradually moves toward the exhaust end, that is, the gap between the engaging surface and the exhaust port gradually decreases, and the gas in the groove is gradually compressed, and the pressure is increased, which is [compression process].
At the same time, the lubricating oil is also injected into the compression chamber and mixed with the chamber gas due to the pressure difference.
4. Exhaust process:
When the meshing end face of the rotor in the maintenance of the screw air compressor is turned into communication with the exhaust of the casing, (the pressure of the compressed gas is the highest), the compressed gas starts to be discharged until the meshing surface of the tooth peak and the groove moves to the exhaust.
End face, at this time, the space between the two rotor meshing surfaces and the casing exhaust port is zero, that is, the completion (exhaust process), at the same time, the length of the groove between the rotor meshing surface and the casing air inlet reaches a long time, the inhalation process is going on.
5.Lubricating oil and capacity adjustment system for screw chiller
The main functions of lubricating oil in screw chiller compressors are lubrication, cooling and capacity adjustment.
The oil pressure in the piston cylinder pushes the piston and spool to move forward/backward in the compression chamber.
In particular, the differential pressure oil supply system in the Hanbell RC-2 series can eliminate the use of external oil pumps in piston compressors.
However, in some special applications, an external oil pump is still required to ensure the safe operation of the screw chiller.
The bearings in the RC-2 series Hanbell screw compressors only need to provide a small amount of oil for lubrication.
The oil injected into the compression chamber can form an oil film in the compression chamber to increase the efficiency of the compressor and absorb some of the heat generated in the above process.
In order to separate the lubricating oil mixed from the refrigerant gas, an oil separator is required to ensure that as little oil as possible is carried into the screw chiller refrigeration system.
Pay special attention to the temperature of the lubricant, which is an important factor affecting the life of the compressor bearing.
High lubricating oil temperature will reduce the viscosity of the oil, resulting in a decrease in the lubricating ability and heat absorption capacity of the lubricating oil. It is recommended to keep the viscosity of the lubricating oil above 10 mm2/s.
The oil temperature should be kept above the system condensation temperature to avoid migration of refrigerant into the system during the summer. When the ambient temperature is too low, the viscosity of the lubricating oil is high.
In this case, the pressure drop of the oil passage in the oil passage is too large to be properly loaded, resulting in a heavy load starting of the compressor. It is recommended to equip the oil heater to heat the oil to increase the oil temperature in a short time.
If the compressor is operating under extreme conditions, an external oil cooler is also required. Have Hanbell determine the amount of cooling required for the oil cooler and the oil flow.
It is recommended to use some lubricating oil with high viscosity under the conditions of severe working conditions.
At this time, the exhaust temperature is higher, which can lower the viscosity of the lubricating oil and ensure the proper viscosity of the lubricating oil.
In addition, there may be a phenomenon in which the amount of oil returned from the evaporator is insufficient, such as a flooded refrigeration system, etc., and oil return is difficult in these systems, resulting in loss of oil in the compressor.
If there is a problem of insufficient oil return in the system, it is recommended to install a secondary oil separator between the compressor venting condenser of the screw chiller to further reduce the oil entering the system.
1. It is recommended to install the optional oil level switch to avoid malfunction of the compressor oil level.
2. The screw compressor can withstand a certain short liquid attack with respect to the piston compressor, but the long-term liquid compression affects the viscosity of the lubricating oil, and the bearing lubrication is insufficient, which easily causes the compressor to be stuck.
Screw chiller four-stage capacity adjustment system load status sharing:
25% (33%) load
When the compressor of the screw chiller is started, the solenoid valve is activated and the piston is at the 25% (33%) load position.
In this state, the high-pressure oil coming from the fuel tank is continuously injected into the piston cylinder through the capillary tube, and the high-pressure oil in the piston cylinder is directly bypassed to the suction port. At this time, all the pistons remain in their initial positions.
Note: The 25% load condition is designed to shorten the start-up time only, avoiding the motor starting current being maintained for a long time and tripping protection.
Do not operate for a long time under the 25% load state after the start-up process. It should be directly loaded and operated (especially under large differential pressure/pressure ratio) to prevent damage to the rotor, bearings and other components due to excessive compressor discharge temperature will effect the screw chiller operation.
50% (66%) load
When the 50%/66% solenoid valve is activated by the temperature control, the power failure is turned off by 25%, and the high pressure oil coming from the fuel tank flows into the piston cylinder, pushing the piston to the right, when moving to 50%/66%.
Since the high-pressure oil is returned from the oil discharge hole through the 50%/66% to the suction port, the piston stops operating at this position, and the compressor of the screw chiller is kept at the load state of 50%/66%.
AdvantaWhen the screw chiller 75% solenoid valve is activated, the 50% solenoid valve is turned off when the power is turned off, and the high oil pressure pushes the piston to continue to move to the right.
When moving to 75%, the high pressure oil is returned from the oil discharge hole through 75% to The suction port, so the piston stops running at this position, and the compressor of the screw chiller is kept at 75% load.ge of semi-hermetic screw compressor.
When we turn off all the solenoid valves of the screw chiller, the high oil pressure continues to flow into the piston cylinder, gradually pushing the piston to the suction side.
When the slide valve contacts the dead center of the compression chamber, the piston also reaches. Its dead center position, at this time there is no phenomenon of bypassing the compressed gas. At this time, the compressor of the screw chiller reached full load operation.
Spray cooling motor, motor working temperature is low, long life; open compressor uses an air-cooling motor, motor working temperature is high, affecting motor life, machine room working environment is poor; using exhaust cooling motor, the motor working temperature is very high, The motor has a short life.
Generally, the external type of oil is large in volume, but the efficiency is high; the built-in oil is combined with the compressor, and the volume is small, so the effect is relatively poor.
The secondary oil splitting effect can reach 99.999%, and the compressor can be well lubricated under various working conditions.
They sit slightly off-center in a shaft, with one side always touching the wall.
As they move at high speeds, they accomplish the same goal as the reciprocating compressor-one part of the shaft is always at a different pressure than the other, so gas can come in at the low pressure point and exit at the high pressure point.
The screw compressor has a male and a female rotor. The male rotor drives the female rotor if it is an oil-injected screw compressor technology, and a timing gear drives both rotors in the oil-free compressor technology as both rotors will run harmonically with minimum calculated clearance between both elements.
The basic principle of a screw compressor is as the male and female rotors are rotating in the opposite direction, they draw air in between them.
As the air progresses along with the rotors the air is compressed as the volume space between the rotors decreases, hence creating compressed air that is displaced to the outlet.
2.3Advantages and Disadvantages of Screw Chillers compared to Piston Chillers
1)Less possibility to break down: As screw compressor has only two moving parts which are not in contact with each other, so there is no wear or tear, and hence it is less possible to break down.
2)Less noise: In a screw compressor, the screws rotate in one direction and thereby causing less noise, heat and vibration. Furthermore, screw compressor is skid mounted and therefore foundation is not required.
3)Suitable for continuous operation: For the above reasons, screw compressors are suitable for 24 hours of continuous operation.
4)Energy saving: More air flow at less power consumed. The difference is more beneficial viable at 20HP and above machines.
5)Compact in size: Screw compressors are smaller in size and lighter in weight, and can be installed in a sealed compartment.
6)Resistant to harsh conditions and environment: Taken care of in the right way, this compressor can last around 2 to 5 times longer than the piston compressor.
1)Higher Price: Compared to a piston compressor, screw compressors are pricey.
2)Higher lubricant consumption: It has a complicated lubricating system and thus consumes more lubricant.
3)High precision installation requirements: Installation required higher precision and techniques.
3. Screw chiller working principle and flow diagram
Generally there are 2 types of screw chillers: air cooled screw chiller and water cooled screw chiller
Let’s have a look at how these two types of screw chiller working and its flow diagram as below:
For air cooled screw chiller:
The air-cooled screw chiller having a key component as the semi-hermetic screw type compressor, and the air cooled screw chiller unit is out of the evaporator as a gas refrigerant;
After the screw compressor is adiabatically compressed, it becomes a high temperature and high pressure state.
The compressed gas refrigerant is condensed by isostatic cooling in a condenser, and after condensation, it is changed into a liquid refrigerant, and then expanded to a low pressure through a throttle valve to become a gas-liquid mixture.
The liquid refrigerant under low temperature and low pressure absorbs the heat of the cold matter in the evaporator and becomes a gaseous refrigerant again.
The gaseous refrigerant re-enters the compressor through the pipeline and begins a new cycle. This is the four processes of the refrigeration cycle.
This is also the main working principle of the air-cooled screw chiller.
The evaporator is one of the most important part in both air cooled screw chiller and water cooled screw chiller.
There are 3 types of evaporators or coolers for screw chillers.
1. Dry Shell and Tube Evaporator
The dry evaporator refrigerant passes through the heat exchanger tube, and the cold water runs outside the high efficiency heat exchange tube.
The heat exchange efficiency of such a heat exchanger is relatively low, and the heat transfer coefficient is only about twice the heat transfer coefficient of the light pipe.
But the advantage is that it is easy to return oil, and the control is relatively simple, and the charging amount of the refrigerant is about 1/2 to 1/3 of the filling amount of the full liquid type unit.
2. Flooded evaporator
The operation of the flooded evaporator and dry evaporator is exactly the opposite.
The cold water passes through the heat exchange tube, the refrigerant completely immerses the heat exchange tube, and absorbs heat and evaporates outside the heat exchange tube.
There are many needle-shaped holes on the surface of the heat transfer tube of the Flooded evaporator, and there are spiral protrusions on the inner surface of the tube to enhance the heat exchange on the cold waterside.
The high-efficiency heat transfer tube that simultaneously enhances the boiling outside the tube and the heat transfer inside the tube increases the heat transfer coefficient by about 5 times compared with the light tube.
3. Falling film evaporator
Falling film evaporators, also known as spray evaporators, are similar to full liquid evaporators, but they differ from full liquid evaporators.
The refrigerant of the evaporator is sprayed from the upper part of the heat exchanger to the heat exchange tube, and the refrigerant only forms a thin film of cold liquid on the heat exchange tube, so that the refrigerant is reduced in boiling evaporation.
The static liquid level pressure increases the heat exchange efficiency, and the heat exchange efficiency is increased by about 5 times compared with the full flooded screw chiller.
Falling film evaporation is flow boiling. Since the thickness of the liquid film on the outer surface of the tube is small, the boiling point without static pressure increases, and the heat transfer coefficient is high.
The bubbles generated by flooded evaporation (that is, immersed evaporation) tend to accumulate on the surface of the heat exchange tube, resulting in a decrease in heat exchange efficiency, and the heat transfer effect is not as good as that of falling film evaporation.
In general, falling film evaporation is a small temperature difference, but it is necessary to prevent fouling and affect heat transfer efficiency.
In summary: The Flooded type means that the refrigerant is between the copper tube and the shell tube, and the chilled water flows inside the copper tube.
The dry type evaporator is the opposite of the two. The refrigerant evaporates in the copper tube, and the water flows between the copper tube and the shell tube.
They are mainly used for the heat pump air conditioner. In industrial low temperature chillers, ordinary dry evaporators are generally used.
“Flooded” means that the “shell-and-tube evaporator” used in the unit adopts the “flooded evaporator”, which is a shell-and-tube evaporator that is different from “dry” and “falling-film”.
Its “shell process” takes the refrigerant cycle, and the “tube process” takes the chilled water cycle. From the cross-section, it is as if there is a large cylinder of refrigerant in the cylinder, and the water pipe bundle is immersed in the refrigerant.
It is just the opposite of the “dry evaporator”. The dry type is the “tube” refrigerant, and the “shell” water is like the refrigerant tube bundle soaked in the water.
The Flooded evaporator and the flooded screw chiller have higher heat transfer efficiency than the dry evaporator/dry screw chiller unit, and the temperature difference between the outlet water temperature and the evaporation temperature is small, and the resistance along the path is small.
which is suitable for units with large circulation ( For example, the centrifuge), the cooling effect is good. However, refrigerant charge requirements are large and a dedicated oil return system is required to help the compressor return oil.
Advantages and disadvantages of dry and flooded evaporators
The Flooded shell and tube evaporator runs water in the tube, and the refrigerant evaporates outside the tube cluster, so the heat transfer surface is basically in contact with the liquid refrigerant.
Generally, the amount of refrigerant charged in the casing is about 55% to 65% of the effective volume of the cylinder, and the refrigerant liquid is heated and vaporized and then returned to the compressor through the liquid separator at the top of the cylinder. Easy operation and management, high heat transfer coefficient.
The disadvantages are:
1 When the evaporation temperature of the refrigeration system is lower than 0 °C, the water in the pipe is easy to freeze and destroy the evaporation pipe.
2 The refrigerant is filled in a large amount
3 Influenced by the height of the refrigerant liquid column, the evaporation temperature at the bottom of the cylinder is high, which will reduce the heat transfer temperature difference
4 The lower part of the evaporator cylinder will accumulate oil, and there must be reliable oil return measures, otherwise it will affect the safe operation of the system.
The dry shell tube type, that is, the refrigerant of the non-full liquid evaporator flows in the tube, and the water flows outside the tube cluster.
There are usually several processes for refrigerant flow. Due to the gradual gasification of the refrigerant liquid, the higher the flow rate, the more the number of process tubes.
In order to increase the water side heat exchanger, a plurality of baffles are arranged on the outer side of the tube heat transfer tube, so that the water flows across the tube cluster multiple times.
The advantages are:
1 Lubricating oil enters the compressor with the refrigerant, there is generally no problem of oil accumulation
2 less refrigerant is filled, generally only about 1/3 of the full liquid type;
When 3t0 is around 0 °C, the water will not freeze.
However, the use of this evaporator must be noted:
1 There are multiple processes for the refrigerant. If the end cover is not well treated, it will produce effluent, which will make the liquid entering the next process unevenly distributed and affect the heat transfer effect
2 There is a leakage problem on the water side. Because there is a gap of 1~3mm between the outer edge of the baffle and the casing, and there is a gap of about 2mm between the heat transfer tube, water leakage will occur.
The practice has proved that water leakage will cause the water side heat transfer coefficient to decrease by 20% to 30%, and the total heat transfer coefficient by 5% to 15%.
4.Features of air cooled screw chiller:
1. Semi-hermeitc screw type high-efficiency compressor, with single-machine system and dual-machine series selection, the unit is compact in structure and convenient in maintenance; adopts the new 5:6 screw rotor design, stable operation, high efficiency and energy saving.
2. Advanced intelligent frosting method. Microcomputer control analyzes the temperature of each point at any time, optimizes the defrost cycle time, and ensures that the defrost does not affect the normal operation of the equipment in time.
3. Professional motor cooling unit. Meet the operating conditions of severe working conditions.
4. With a new generation of high-efficiency heat exchange tubes, the heat transfer coefficient can be increased by 5%.
The double-slot tube-plate design and advanced tube expansion technology make the structure more sealed and reliable, completely avoiding the possibility of mutual penetration.
For water cooled screw chiller：
When the water cooled screw chiller is working, the screw compressor draws the low-temperature and low-pressure refrigerant in the evaporator into the cylinder, and the compressor steam is compressed into high-temperature and high-pressure refrigerant, then enters the condenser through the exhaust pipe.
The high temperature and high pressure refri