Different Types of Refrigeration Compressors and Their Applications, Brands

1. Common Faults

Figure 1: Refrigerator compressor.

The refrigeration compressor is the core and heart of the refrigeration system, and is an indispensable part of air conditioners, refrigerators, chillers, etc. The capabilities and characteristics of the compressor determine those of the refrigeration system.

The following introduces the common types and applications of refrigeration compressors. By reading the following, it can help you understand refrigeration compressors.

1. Refrigeration Compressor Classification

(1) According to the structure type/function principle: positive displacement compressor (volumetric compressor), dynamic compressor.

●Volumetric type ---- rotary type (including screw, sliding vane, scroll, and Roots compressors) and reciprocating compressor (including piston, diaphragm compressors)
●Dynamic compressor ---- centrifugal, axial, jet , and mixed flow compressors.

(2) According to the compressed media: air compressor, nitrogen compressor, oxygen compressor, hydrogen compressor, etc.
(3) According to exhaust pressure: low pressure (0.3-1.0MPa), medium pressure (1.0-10MPa), high pressure (10-100MPa), ultra-high pressure (>100MPa).

(4) According to the scope of application: low back pressure type, medium back pressure type and high back pressure type. High back pressure is actually a high compression ratio, and low back pressure is actually a low compression ratio.

●Low back pressure type (evaporating temperature -35 ~ -15 ℃), generally used in household refrigerators, food freezers, etc.
●Medium back pressure type (evaporating temperature -20 ~ 0 ℃), generally used in cold drink cabinets, milk refrigerators, etc.
●High back pressure type (evaporation temperature -5 ~ 15 ℃), generally used in room air conditioners, dehumidifiers, heat pumps, etc.

But in general, we usually classify refrigeration compressors by their working principles. As shown in the figure below, it is very easy to understand.

Table 1: Different types of refrigeration compressors.

2. Common Refrigeration Compressors

There are three types of common refrigeration compressors: reciprocating piston compressors, rotary compressors, and scroll compressors.

2.1 Reciprocating Piston Compressor

The reciprocating piston compressor is mainly composed of a cylinder, piston, crankshaft and connecting rod mechanism. The crankshaft is driven to rotate by the electric motor, and makes the piston reciprocate up and down in the cylinder through the connecting rod.

Each time the compressor completes one cycle, the crankshaft rotates a round, and performs the process of compression, exhaust, expansion and suction in sequence. The compressor runs continuously under the drive of the motor, and the piston reciprocates continuously in the cylinder to realize the refrigeration cycle.

Figure 2: Open type piston refrigeration compressor.

2.2 Screw Compressor

The screw compressor is a rotary positive displacement compressor. It utilizes the changes of the screw groove volume and position of the screw to complete the process of inhaling, compressing and exhausting gases.

Oil-free screw compressors were introduced in the 1930s and were mainly used to compress air. Later, the screw compressor with oil injection in the cylinder appeared, and its performance was improved. Oil-injected screw compressors are one of the main types of refrigeration compressors.

Screw compressors are divided into two categories: twin-screw and single-screw types.

Figure 3: Twin screw refrigeration compressor.

2.3 Scroll Compressor

The scroll compressor is mainly composed of a fixed scroll and an orbiting scroll. The unique design of the scroll compressor makes it an energy-saving compressor in today's world.

The main running part of the scroll compressor, scroll plate only has meshing and no wear and tear, so it has a longer life and is known as a maintenance-free compressor. Scroll compressors run smoothly with low vibration, and are also known as "super-static compressors".

The scroll compressor features precise structure, small size, low noise, light weight, low vibration, low energy consumption, long life, continuous and stable gas transmission, and reliable operation.

Figure 4: The fixed scroll and orbiting scroll.

3. Other Common Refrigeration Compressor Classifications

3.1 Variable Displacement Compressor

The variable displacement compressor can automatically adjust the power output according to the set temperature. The air-conditioning control system does not collect the temperature signal of the air outlet of the evaporator, but controls the compression ratio of the compressor according to the change signal of the pressure in the air-conditioning pipeline to automatically adjust the air outlet temperature.

In the whole process of refrigeration, the compressor is always working, and the adjustment of the refrigeration capacity is completely controlled by the pressure regulating valve installed inside the compressor.

When the pressure at the high-pressure end of the air-conditioning pipeline is too high, the pressure regulating valve shortens the piston stroke in the compressor to reduce the compression ratio, which will reduce the refrigeration capacity.

When the pressure at the high pressure end drops to a certain level and the pressure at the low pressure end rises to a certain level, the pressure regulating valve increases the piston stroke to improve the refrigeration capacity.

3.2 Fixed Displacement Compressor

The displacement of a fixed displacement compressor increases proportionally with the growth of the rotational speed of the engine (electric motor), and it cannot automatically change the power output according to the cooling demand.

Take the car air-conditioning compressor as an example, its control is generally realized by collecting the temperature signal of the air outlet of the evaporator.

When the temperature reaches the set temperature, the electromagnetic clutch of the compressor is released and the compressor stops working. When the temperature rises, the electromagnetic clutch is engaged and the compressor starts to work.

The fixed displacement compressor is also controlled by the pressure of the air conditioning system. When the pressure in the pipeline is too high, the compressor stops working.

3.3 Hermetic Compressor

The compressor and the motor of the hermetic compressor are installed together in a closed casing, and the upper and lower casings are welded. It features compact structure, good sealing performance and low noise. But it has small power and is difficult to maintain.

Its cooling capacity is less than 60KW, and it is mostly used in air conditioners and small refrigeration equipment.

Figure 5: Hermetic refrigerator compressor.

3.4 Semi-Hermetic Compressor

The crankcase body and the motor casing form a closed space together. It has stable operation and long service life, and has a large cooling capacity. It can be used in various working conditions and can be maintained, but the noise is slightly higher.

It is divided into single-stage compression type (conventional type, butterfly valve type, unloading type, connected type) and two-stage compression type. Its cooling capacity is 60-600KW, which can be used in various air-conditioning and refrigeration equipment.

Note: The difference between a hermetic compressor and a semi-hermetic compressor is whether the compressor is detachable or not.

The shell of a hermetic compressor is a fully enclosed space and is all welded without bolts. It cannot be disassembled for maintenance when damaged, while the semi-hermetic compressor is detachable and repairable.

Figure 6: BITZER semi-hermetic piston compressor.

3.5 Open Compressor

The compressor and the motor are two separate devices, which are connected externally. Its structure is complex and heavy, and the work is unstable. Its advantage is that it is easy to maintain.

4. Various Refrigeration Compressor Applications

Figure 7: Various refrigeration compressor applications diagram.

Usually the compressors of domestic refrigerators and air conditioners are positive displacement type, which can be divided into reciprocating and rotary types.

Hermetic piston compressors: Most of hermetic piston compressors have a cooling capacity of no more than 0.5KW and are mainly used in household refrigerators/freezers and small commercial refrigeration equipment.

Semi-hermetic piston compressor: The refrigeration capacity of a single unit is from 3kw to 100kw. At the same time, it can be used in parallel with multiple heads. It can be used in multiple working conditions and can be used for refrigeration working conditions, but also suitable for air conditioning conditions.

Open piston compressor: This refrigeration compressor is commonly used in cold storage, and is rarely used in chillers of air conditioning conditions.

Rolling rotor compressor (Rolling piston compressor): Its cooling capacity is 8 to 12KW, and it is mostly used in small air conditioners and refrigeration equipment. It is fully enclosed, with compact structure, good sealing performance and low noise. But its power is small and difficult to maintain.

Figure 8: Rolling piston compressor.

Scroll compressor: Its cooling capacity is 8~150KW, which can be used in various air-conditioning and refrigeration equipment. It is fully enclosed, with simple and compact structure, high performance, good sealing and low noise.

Screw compressor: Its cooling capacity is 100-1200KW, which can be used in large and medium-sized air-conditioning and refrigeration equipment. It features compact structure, high working performance, large cooling capacity and stepless adjustment, but its lubricating oil system is complicated and the noise is high.

Centrifugal, scroll and screw compressors are mostly used in commercial air conditioners.

Centrifugal compressor: Its maximum cooling capacity can reach 30000KW, and it is used in large air conditioners and refrigeration equipment. It features stable work, high performance, long life, large cooling capacity, and stepless adjustment.
Centrifugal compressors are divided into open, semi-hermetic and hermetic types according to their structure.

5. Major Brands of Refrigeration Compressors

Japanese compressor brands: Toshiba, Carrier, Mitsubishi Electric, Mitsubishi Heavy Industries, Panasonic, SANYO (Panasonic), Hitachi, Embraco (Nidec, originating in Brazil).
Korean compressor brands: Samsung and LG.
American compressor brands: Copeland.
Italian compressor brand: Zanussi (ZEL).
French compressor brand: Tecumseh.
China's holding compressor brands: Zhongshan Galanz, Shanghai Hitachi Highly (Hisense series), GMCC, Chunlan compressor.
Compressor brands in Taiwan, China: TECO.
Joint venture compressor brands: Panasonic Wanbao (Guangzhou).

5.1 Reciprocating Piston Compressor Brands

Common brands of hermetic reciprocating piston compressors:
France: TECUMSEH, MANEUROP; America: COPELAND, Denmark DANFOSS; Sweden: ELECTROLUX; Japan: HITACHI, NATIONAL, TOSHIBA, SANYO, MATSUSHITA, DAKIN; Korean: LG; China: Chunlan, etc.

Common brands of semi-hermetic reciprocating piston compressors:
America: COPELAND; Germany: BITZER, BOCK; Italy: FRASCOLD, REFCOMP, DORIN; Japan: MATSUSHITA, HITACHI, SANYO, etc.

5.2 Rotary Compressor Brands

Common brands of rolling piston compressors:
Japan: MATSUSHITA, HITACHI, NATIONAL, SANYO, TOSHIBA, etc.

Common brands of scroll compressors:
America: COPELAND; France: MANEUROP; Japan: HITACHI, NATIONAL, DAKIN, SANYO, etc.

Common brands of screw compressors:
Germany: BITZER, GRASSO; Italy: FRASCOLD, REFCOMP, DORIN; Japan: HITACHI, DAKIN, MITSUBISHI, KOBELCO, MYCOM; Taiwan: Fusheng, Hanbell, etc.

5.3 Common Brands of Centrifugal Compressors

American: TRANE, CARRIER, YORK and MCQUAY; Japan: MITSUBISHI, HITACHI and EBARA; Switzerland: SULZER, etc.

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