How Much Do You Know about a Rotary Compressor?

From Persian cooling towers to Multi V i VRF air conditioners, mankind has come a long way in terms of improvising cooling methods.

In the last newsletter, we discussed some of the most frequently asked questions about scroll compressors. This time, we have summed up some of the most commonly asked questions about rotary compressors.

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The invention of a rotary compressor was a new breakthrough in air-conditioning and refrigeration solutions, initiating the introduction of a new generation of air conditioners and refrigerators. Its wide application in modern-day ACs can be attributed to its compact size and energy efficiency.

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Let’s find out more in detail about these power-packed compressors.?

Q. What is a rotary compressor?

A rotary compressor —as the name suggests— uses a rotary-type positive-displacement mechanism. It is widely used for refrigerants commonly used in HVAC products for residential applications.

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Rotary compressors can be divided into a main body and an accumulator; the main body can be further divided into an electrical section with the motor and a mechanical part with a compression chamber.

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The diagram below explains the flow of the refrigerant inside a rotary compressor. The refrigerant from the evaporator enters the accumulator, from where it moves to the main body’s compression chamber for compression, and is then discharged through the discharge pipe.

Q. Why does a rotary compressor have an accumulator?

The biggest difference between a scroll compressor, which was covered in the previous newsletter, and a rotary compressor is the presence or absence of an accumulator. Unlike a scroll compressor, a rotary compressor has an accumulator.

Let’s understand the function of an accumulator in a rotary compressor.

The compressor compresses the low-temperature, low-pressure refrigerant gas that has passed through the evaporator into a high-temperature, high-pressure gas; meaning the refrigerant that passes through the evaporator is required to be in a low-temperature, low-pressure gaseous state, however, in some cases, the liquid refrigerant might flow in unevaporated and reach the compression chamber in a liquid state.

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It should be noted that liquids are almost incompressible. If the compressor tries to compress a liquid refrigerant, it might damage the body of the compressor.

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This is where an accumulator comes into play. The refrigerant from the evaporator is not directly sucked into the compression chamber; instead, it passes through the accumulator first to reach the compression chamber. The accumulator helps the liquid refrigerant evaporate before reaching the main body of the rotary compressor. In short, an accumulator prevents a rotary compressor from potential damage caused by the liquid refrigerant.

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Besides, the accumulator has a filter preventing foreign objects from entering the compression chamber. You can think of it as the strainer of the rotary compressor.

Q. How does a rotary compressor function?

Before moving on to the details of compression in a rotary compressor, let us learn about the sub-components that make up the compression chamber.

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The compression chamber of a rotary compressor consists of a cylinder, a main bearing and a sub-bearing that seal the cylinder, a crankshaft that transfers electrical energy from the motor to the compression chamber, a roller that rotates along the eccentric orbit of the shaft and changes the volume of the compression chamber, and a vane that separates the low-pressure chamber from the high-pressure chamber.

The compression chamber consists of a roller, a vane, a sub-bearing and a cylinder. The rollers and vane are distinct features of a rotary compressor.

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The rotary compressor compresses the refrigerant coming out of the evaporator through the eccentric rotation of the roller and the vertical movement of the vane located in the inner diameter of the cylinder. Low pressure and high pressure are divided into rollers and vanes, and the principle is to compress the refrigerant by changing its volume through eccentric rotation.

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Let's look at the pictures below to understand this. In the first picture, the two circles are concentric, whereas, in the second picture, the two circles are eccentric. In the first figure, even if the inner circle rotates, the volume of space A does not change. However, in the second picture, you can see that since the inner and outer circles are eccentric, the volume decreases from space A to space A’ and the pressure rises when the inner circle rotates.

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As we learned above, the refrigerant from the evaporator passes through the accumulator first. The accumulator helps the liquid refrigerant evaporate before being sucked into the compression chamber. All this process requires energy supplied by the motor.

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The motor of a rotary compressor consists of a stator and a rotor. It receives electrical energy from an outside source and converts it into kinetic energy required by the compression chamber of the compressor to compress the refrigerant.

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Q. Why use a rotary compressor?

Rotary compressors are compact, have a simplified structure and are pretty reliable. Moreover, they are inexpensive, lighter and provide more capacity. They function even in extreme weather conditions and consume less oil. These features make rotary compressors favorable for heat pumps or dryers.

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Conclusion

Today, we learned about the operation and body of a rotary compressor— its subcomponents, peculiarities, and why it is a popular choice for heating solutions. For information on LG Rotary Compressor, you can visit our website.

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We hope that this newsletter was helpful in understanding the functions of a rotary compressor.?Next time, we will be back with more useful information, till then stay tuned.