For HVAC practitioners, refrigeration technicians and procurement staff, refrigeration compressor is the core of the refrigeration system, the selection directly affects the energy efficiency, reliability and life of the equipment. In the face of a variety of models, selection is easy to confuse, this article will dismantle the six common types, to help quickly select the type.
Piston Refrigeration Compressor
Principle of operation
The core operation of piston refrigeration compressor relies on the crankshaft connecting rod mechanism, the piston in the cylinder to do reciprocating motion, so as to complete the cycle of suction, compression and exhaust.
When the piston moves downward, the suction valve opens and the low-pressure refrigerant gas is sucked into the cylinder; when the piston moves upward, the suction valve closes and the gas is compressed into a high-temperature and high-pressure state, and ultimately enters into the condenser through the exhaust valve.
Key Features
- Wide range of adaptable temperature, can meet the low temperature, ultra-low temperature to high temperature refrigeration needs of the whole scene;
- Simple structural design, high technical maturity, and convenient maintenance;
- Excellent abrasion resistance of core components, service life is usually up to 8-10 years, and the market utilization rate in the industrial refrigeration field is over 40%.
The noise and vibration caused by the reciprocating piston is relatively obvious; piston ring, valve plate and other parts need to be replaced regularly, the maintenance frequency is higher than other types of compressors.
Main applications
- Daily scene: widely used in household air conditioners, various types of commercial air conditioners and small and medium-sized commercial refrigeration equipment (such as convenience store refrigerated cabinets, catering kitchen freezers, etc.), by virtue of its mature and reliable performance, to meet the basic needs of daily refrigeration;
- Industrial field: the core application is used in the frozen processing and cold storage of food processing, low-temperature cold storage in the pharmaceutical industry (for constant temperature storage of drugs and vaccines), and low-temperature laboratories in the field of scientific research (adapting to the needs of a wide range of temperatures), and it can accurately match the requirements of various refrigeration parameters in the industrial scenarios;
- Cold chain logistics: it is the core refrigeration power component of refrigerated trucks and refrigerated containers, adapting to the complex working conditions in long-distance transportation, and guaranteeing the temperature stability of fresh food, medicines and other materials in the process of inter-regional transportation by virtue of high durability, and supporting the whole cold chain closed loop.
Rotary Refrigeration Compressor
Working Principle
Rotary refrigeration compressor relies on the eccentric rotation of the rotor in the stator to compress the refrigerant, which is mainly divided into two types: vane type and rolling rotor type.
The vane type forms multiple compression chambers by sliding the sliding blades in the rotor groove, while the rolling rotor type gradually completes gas compression by utilizing the tiny gap between the eccentric rotor and the stator.
Key Features
- Compact and lightweight, suitable for refrigeration equipment with limited installation space;
- Small operation vibration and low noise;
- Adapted to frequency conversion control, fast response speed;
- Excellent energy efficiency performance under partial load.
However, its cooling capacity has limitations, can only meet the needs of small and medium-sized equipment, can not be adapted to super-large refrigeration system.
Main Applications
- Domestic and small commercial air-conditioning field: as a mainstream choice, it is widely adapted to wall-mounted domestic air-conditioners, small cabinet air-conditioners, as well as embedded commercial air-conditioners in convenience stores, small offices and other places. With compact and lightweight body can be flexibly adapted to the limited installation space, low noise and low vibration characteristics to ensure the comfort of the use of the environment.
- Automotive air conditioning system: a wide range of adaptable, covering the daily sedan, large capacity buses and long-distance running trains and other types of vehicles. The advantage of its inverter response quickly, can quickly adapt to the temperature changes in the vehicle driving, providing stable cooling effect for the driver and passengers.
- Small refrigeration equipment field: indispensable in household refrigerators, embedded freezers, small commercial freezers (such as milk tea store raw materials freezer, community fresh food store small refrigerated cabinets) and other equipment. Compact structure can be perfectly suited to the internal layout of the equipment, efficient part-load performance can be balanced between refrigeration needs and energy-saving effect.
Scroll Refrigeration Compressor
Principle of Operation
The core component of the scroll type refrigeration compressor is a pair of scroll disk assemblies with involute line design, which are tightly meshed together to form a hermetically sealed compression chamber. One of the scroll disk is fixedly installed in the body, known as the static scroll disk; the other is driven by the drive mechanism to do eccentric orbit rotary motion, known as the dynamic scroll disk, and the dynamic scroll disk only orbit motion, not rotating around its own axis.
During operation, low-pressure refrigerant enters the crescent-shaped closed chamber from the suction port of the outer ring; with the eccentric rotation of the dynamic scroll disk, the chamber moves to the center and the volume is reduced, the refrigerant is compressed step by step, the pressure rises, and finally discharged from the center of the high-pressure exhaust port to complete the compression.
Key features
- Compact structure, high energy efficiency ratio;
- Smooth and quiet operation, suitable for high-end air conditioning and precision cooling needs;
- Valve-less design, fewer moving parts, less wear and tear;
- Maintenance costs are significantly reduced;
- Adapted to variable frequency control, with excellent part-load performance.
However, it is less adaptable than piston compressors in extreme working conditions due to its stringent requirements on manufacturing precision.
Main Applications
- Commercial air conditioning and heat pump systems: with high efficiency, quiet, smooth operation and excellent frequency conversion adaptability, accurately meet the dual demand for comfort and energy saving in commercial premises, the market share continues to rise, and has become the preferred equipment for air-conditioning systems in shopping malls, office buildings and other large commercial spaces.
- In the field of cold chain transportation: due to its compact structure and strong reliability, it is widely used in long-distance trunk refrigerated trucks, trans-oceanic marine refrigeration containers and other equipments, which can be stably adapted to the complex working conditions during transportation, and guarantee the constant-temperature storage of fresh food, medicines and other materials.
- In the field of household and specific commercial units: it is the mainstream core component of household central air-conditioning systems, as well as 7-25HP commercial multi-connected units and modular units. Its efficient part-load performance can accurately match the dynamic refrigeration needs of different scenarios, and its compact structure can also be adapted to various types of unit installation layouts, taking into account the refrigeration effect and space utilization.
Screw Refrigeration Compressor
Principle of Operation
Screw refrigeration compressor relies on a pair of intermeshing rotor and rotor rotation, based on the principle of volumetric change, the refrigerant in the closed space composed of the rotor, the body and the end cover, along with the rotor rotating cyclic volume changes, and thus complete the whole process of suction, compression and exhaust.
Key Features
- Applicable to large cooling capacity, outstanding performance in the field of industrial refrigeration; the double rotor structure can cover dozens to thousands of cold tons of cooling capacity, without the need for multiple parallel connection to meet the demand for large loads, and improve the efficiency of system integration;
- Continuous compression runs smoothly with little vibration (vibration value <5mm/s); it can reduce the operation noise, minimize the wear and tear of piping and other components, extend the service life of the refrigeration system and enhance the environmental comfort;
- Few moving parts, no wearable valves, low maintenance requirements; the core components are only the rotor and bearings, daily maintenance is simple, no need to change wearing parts frequently, cost reduction and downtime;
- Long service life (≥15 years), suitable for all-weather operation; strong resistance to working conditions, can work stably from -20℃ to 40℃, suitable for industrial continuous refrigeration scenarios.
However, it is relatively noisy and usually requires additional sound insulation treatment, and relies on oil injection for sealing and cooling, which requires high quality of lubricating oil.
Main Applications
- Large central air-conditioning field: Adapt to the demand for large cooling capacity, for large commercial complexes, office buildings, transportation hubs and other places of the core refrigeration equipment, to meet the large area of centralized refrigeration, to ensure a comfortable and stable environment;
- Industrial cooling system field: suitable for petrochemical high-temperature and high-pressure process, metallurgy and electronic manufacturing equipment cooling and other complex working conditions, stable cooling to ensure continuous industrial production;
- In the field of food processing industry: matching the needs of large-scale cold storage, providing constant low temperature for the frozen processing and preservation of food ingredients, and contributing to food safety;
- Special Precision Scenario: Used in high and low temperature testing room, freeze drying equipment and other high precision demand scenarios, to ensure the smooth progress of testing and production.
Centrifugal Refrigeration Compressor
Working Principle
Centrifugal Refrigeration Compressor works by using the high speed rotation of the impeller. When the motor drives the impeller to rotate, the low-pressure refrigerant gas in the center of the impeller is sucked in, and thrown to the outer edge of the impeller along the direction of the blade, and the speed and kinetic energy are increased greatly.
Subsequently, the gas enters the diffuser, the speed is gradually reduced, and the kinetic energy is converted into pressure energy, and finally discharged in a high temperature and high pressure state, and enters the condenser to complete the cycle.
Key Features
- Excellent energy efficiency, relying on the principle of kinetic energy conversion by high-speed rotation of the impeller, low mechanical loss, suitable for ultra-large cooling systems of more than 1,000 cold tons, the energy efficiency of large-scale projects is 15%-20% higher than that of other types, significantly reducing the long-term energy consumption of large-scale refrigeration;
- Continuous operation ability is excellent, stability is outstanding; few moving parts, low wear and tear, can run all year round without interruption, no need for frequent maintenance, suitable for data centers and other scenes with high requirements for refrigeration continuity, to avoid refrigeration interruption loss.
Obvious shortcomings
- High initial investment cost;
- Complicated structure and relatively cumbersome maintenance process;
- Higher requirements for professional skills of operators.
- According to the data, in large-scale projects with cooling capacity of more than 1,000 cooling tons, the energy efficiency ratio of centrifugal refrigeration compressors is 15-20% higher than other types.
Main Applications
Centrifugal refrigeration compressors are widely used in mega central air-conditioning systems, suitable for high-rise buildings, airports, data centers and other scenarios, and are the core equipment for such large-scale refrigeration demand; meanwhile.
They can accurately match large-scale refrigeration demand in chemical industry, petroleum refining, and other industrial fields, and provide cold capacity guarantee for the stable operation of industrial production.
Magnetic Suspension Refrigeration Compressor
Working Principle
The core of the Maglev Refrigeration Compressor is the high-precision magnetic levitation bearing system, which is the key to ensure its high-efficiency and frictionless operation, and it is mainly composed of four major components, namely, the rotor, the high-precision displacement sensor, the intelligent controller and the electromagnetic actuator.
The displacement sensor monitors the radial and axial position of the rotor in real time with high precision, and transmits the signal to the intelligent controller in real time;
controller quickly analyzes and calculates, and then outputs precise control instructions to the electromagnetic actuator. Electromagnetic actuator integrated electromagnet and power amplifier, can be converted from weak electric command to strong electric signal drive to generate a stable magnetic field.
At the same time, permanent magnet synchronous motor to provide power for the rotor, under the action of the magnetic field rotor accurately suspended in the center of the stator, the whole process of no physical contact, to eliminate mechanical friction from the root.
Key Features
- Excellent noise control, almost “super quiet” level, the measured noise value is usually as low as 60 dB or less, far better than traditional compressors, can create a quiet application environment;
- Outstanding performance in energy consumption, relying on the core design of the magnetic levitation bearing without physical friction, significantly reducing mechanical friction energy consumption, compared with the traditional screw-type, piston compressors such as energy-saving efficiency of more than 40%, long-term operation can significantly reduce the cost of energy consumption;
- Nearly zero wear and tear, the rotor and other parts of the whole process without physical contact, completely eliminating the need for lubricating oil replacement, maintenance and replacement of wear parts and other routine maintenance work, maintenance costs have been significantly reduced;
- Significantly extended service life, generally up to 15-20 years, far more than the average service life of the traditional compressor 8-10 years, and can effectively avoid the wear and tear caused by the performance degradation problem.
However, the technical threshold is high, and the manufacturing precision of the magnetic levitation bearings and motors is stringent, so the initial procurement cost is relatively high.
Main Applications
The compressor is suitable for places with high requirements for noise and energy efficiency, such as office buildings, data centers, etc.; hospitals, laboratories and other scenarios that require precision cooling are also very suitable, and are widely used in high-end central air-conditioning and precision industrial cooling systems.
Conclusion
6 types of compressors have their own advantages: piston universal, rotary small, scroll efficient and quiet, screw type suitable for large-scale needs, centrifugal specializing in ultra-large systems, magnetic levitation energy-saving and low-consumption. Selection needs to be combined with the cooling capacity, installation space, working conditions and budget comprehensive judgment.
Selection of the first clear core requirements, screening against the characteristics or consult a professional service provider. Select the right compressor to ensure the long-term efficient and stable operation of the equipment.
