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: The Completely Buying Guide for Importer
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.
Screw Chiller
2. What is the difference between Screw Chillers and Piston 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 (Piston Type) 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 Rotary Screw chiller
Rotary compressors, on the other hand, use rollers.
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.
2.3 Advantages and Disadvantages of Screw Chillers compared to Piston Chillers
Advantages:
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.
Disadvantages:
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.
Air Cooled Screw Chiller Working Principle
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.
150Ton Air Cooled Screw Chiller
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 refrigerant gas exchanges heat with the cooling water in the condenser, transfers heat to the cooling water, and the refrigerant gas condenses into a high pressure liquid.
The high pressure liquid from the condenser is throttled and depressurized by the thermal expansion valve and then enters the evaporator.
In the evaporator, the low-pressure liquid refrigerant absorbs the heat of the chilled water and vaporizes, so that the chilled water is cooled and cooled to become the required low-temperature water.
The vaporized refrigerant gas is again sucked into the compressor for compression, and is discharged into the condenser.
So that it is continuously circulated and continuously circulated, thereby achieving cooling of the chilled water.
Water cooled screw chiller must go along with a cooling tower, water pump, insulation water tank, to make a complete water cooling system.
Water Cooled Screw Chiller Working Principle
Features of water cooled screw chiller:
Efficient semi-hermetic screw compressor, the screw chiller unit runs smoothly and the noise is low.
Inspiratory cooling results in low motor operating temperatures and long motor life.
With high-quality bearings, the bearing life is at least 40,000 hours. Built-in oil separator for smaller size and better results.
It can be safely implemented in the range of 0% to 100% or stepless energy regulation to maximize power conservation.
The condenser adopts high-efficiency shell-and-tube heat exchanger (optional stainless steel plate heat exchanger), built-in high-efficiency heat exchange tooth tube, reasonable design and good heat exchange effect;
The evaporator adopts high-efficiency shell-and-tube heat exchanger (optional stainless steel plate heat exchanger), built-in high-efficiency heat exchange tooth tube, reasonable design and good heat exchange effect;
Suitable for R22, R407c, R134a, R404A and other working fluids.
Less moving parts and low failure rate. An economizer can be selected to further increase compressor refrigeration capacity and efficiency.
A spray chiller can be selected to extend the range of applications for the compressor.
Oil cooling can be selected to increase compressor efficiency and compressor application.
120Ton Water Cooled Screw Chiller
Advantages of screw chillers
1. Simple structure, less moving parts, less wearing parts, only 1/10 of the piston type, low failure rate and long service life.
2. The circular motion is stable, there is no surge phenomenon during the low load operation, low noise and low vibration.
3. The compression ratio can be as high as 20 and the EER value is high.
4. Convenient adjustment, the stepless adjustment in the range of 10%~100%, high efficiency in partial load, and significant power saving.
5. Small size, lightweight, can be built as a fully enclosed large capacity screw chiller unit.
6. Not sensitive to wet strokes.
7. It is a positive pressure operation, and there is no problem of intrusion of outside air.
150Ton Screw Chiller in Kuwait
Screw chiller applications:
1. Industrial screw chiller
It can provide 5~15°C chilled water, or use ethylene glycol solution as the coolant. It can provide -5~+5°C process frozen aqueous solution, which can be used as ice storage, low temperature air supply, central air conditioning and other production processes.
At the same time, according to the requirements of the user, I can specially design the unit to provide a large temperature difference chiller (the temperature difference between the inlet and outlet water is 8~15°C). Or higher than the water temperature unit (outlet water temperature 15 ° C ~ 25 ° C). The cooling capacity is 94KW-3360KW.
75Ton air cooled chiller with screw compressor
2. medium temperature screw chiller
The outlet water temperature is -5 ° C ~ -45 ° C, using imported semi-closed screw compressor unit (with economizer); can provide -5 ° C ~ -45 ° C low temperature.
Ethylene glycol solution or brine solution, can be used as a cold source for chemical, pharmaceutical, cold storage, ice rink and other processes. The cooling capacity is 55KW-2000KW.
Water Cooled Screw Chiller
3, low temperature screw chiller
The effluent temperature is -45 ° C ~ -110 ° C, can provide -45 ° C ~ -110 ° C alcohol or calcium chloride aqueous solution chilled water; using a binary stack or ternary cascade screw refrigeration system. High energy efficiency ratio and stable operation.
At the same time, it can be designed according to the requirements of use, ultra-low temperature type, anti-corrosion type, explosion-proof type special industrial screw type chiller, which can meet the requirements of various industries for process cold source.
Nowadays, the use of screw chillers is seen in many industries. For this screw chiller, which different industries can be used in the application process, in order to allow users in different industries to choose more For more understanding.
let’s take a brief look at some of its scope of applications.
First, the construction industry
Screw chillers can be used in some construction industries.
There are many places used in the construction industry.
For example, it can supply chilled water to concrete, and it can change the molecular structure of concrete.
Screw Chiller for Concrete Cooling
In the process of construction, it is more suitable for the purpose of use, and its application can also invisibly play a role in the hardness and toughness of concrete, so it is now seen in many construction industries.
The development in this industry will also become larger and larger, and users who have processed in this industry can choose to use this equipment.
Second, the food industry
This type of chiller equipment can also be used in some food industries.
We all know that after many foods are processed, they need to be packaged, but the food heated by high temperature needs to be cooled when it is put into the package.
The screw chiller can play such a role, allowing the hot food to cool quickly and fit into the bag, so it is still used in this food industry.
Screw Chillers for Food Processing
Third, Big factory or central air conditioning of HVAC
The cooling capacity of screw chiller is higher than that of the scroll chiller.
So this screw chiller can be mainly used in chemical plants, ink printing plants, automobile manufacturers or central air conditioning systems or other large industrial refrigeration.
Screw Chiller for Air Conditioning and HVAC
The above is the application of screw chillers in the construction, food industries, air conditioning for big buildings.
Now with the development of various industries, the application of such screw chillers will gradually increase, and it will become a must in many industries in constant innovation.
Some tips for selecting a correct screw chiller
To select a suitable screw chiller for your industry is very important, there are some useful tips for your reference:
Screw Chiller
1. The main control parameters of the screw chiller are the refrigeration performance coefficient, rated cooling capacity, input power and refrigerant type.
2. The selection of the screw chiller should be considered according to the cooling load and use. For refrigeration systems with long periods of the low load operation, a multi-head piston compressor unit or a screw compressor unit should be used for easy adjustment and energy saving.
3. When selecting a screw chiller, priority is given to units with a higher coefficient of performance values. According to statistics, the average of screw chiller operating time under 100% load is about 1/4 of the total running time.
The operating time ratios of 100%, 75%, 50%, and 25% of the total operating time were approximately 2.3%, 41.5%, 46.1%, and 10.1%.
Therefore, when selecting a screw chiller, priority should be given to models with a flatter efficiency curve.
At the same time, the adjustment range of the screw chiller load should be considered when designing and selecting. The multi-head screw chiller has excellent partial load performance and can be selected according to actual conditions.
4. When selecting a screw chiller, pay attention to the conditions of the nominal working condition. The actual cooling capacity of a chiller is related to the following factors:
a) cold water effluent temperature and flow rate;
b) Inlet water temperature, flow rate and fouling coefficient of cooling water.
5. When selecting a screw chiller, pay attention to the normal working range of the unit, mainly because the current limit of the main motor is the current value of the shaft power under nominal conditions.
6. In the design selection, it should be noted that under nominal operating conditions, the outlet temperature of cold water should not exceed 15 °C, and the outdoor dry bulb temperature of air-cooled screw units should not exceed 43 °C.
If it is necessary to exceed the above range, it should be understood whether the range of use of the compressor is allowed, and whether the power of the main motor is sufficient.
Why are we a reliable screw chiller supplier?
TopChiller is a professional screw chiller manufacturer with decade years of experience. We have installed thousands of various screw chiller units in Singapore, Australia, Indonesia, Nigeria, Saudi Arabia, Kuwait for different industrial and commercial applications.
We also have an aftersales team can do installation and commission at screw chiller project site. After installation, our engineer will give your stuff a full detailed training of how to use the screw chiller and maintenance guide.
Screw Chiller Maintenance
Conclusion
As a leader in screw chiller manufacturing, TopChiller having 20 years experience in design and making screw chillers.
Both air cooled screw chiller and water cooled screw chiller are compact design and high cooling efficiency.
We are willing to provide technical support to all clients, we have both standard and custom designs in air screw chiller and water screw chiller.
Contact our refrigeration engineering to help you get suitable screw chiller design and solution.