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What is the Best AC Compressor: Rotary or Reciprocating? 

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The compressor is the heart of the air conditioning unit that plays a vital role in the cooling process. Furthermore, it ensures the effective and continuous working of the device.

These AC compressors are of different types and have unique functioning.

In this article, we specially curated all the information related to the types of AC compressors, and their advantages and disadvantages.

By the end of this write-up, you shall be able to assess and choose the best AC compressor for you.

Let us get started with the discussion.

What Is A Compressor?

A compressor is a crucial component of the AC located in the outdoor unit of the device. It is responsible for maintaining the optimum and continuous flow of refrigerant in the evaporator and condenser coils.

How Does An AC Work?

Several components of an air conditioner assist in the functioning of the unit. They are refrigerant, evaporator coil, compressor, condenser, expansion valve.

Let us now try to understand the working mechanism of an AC unit:

The refrigerant is responsible for the air conditioning process in the unit. Also known as a coolant, this cooling agent absorbs the heat from the interior and transfers it to the outer environment through the coils. These coils direct the refrigerant from inside your room to the outdoors and then back inside again. It is a cycle that keeps repeating as long as your device is in operating mode.

Below is a picture that depicts the functioning of an air conditioner:

As shown in the above picture, the moment you switch on the device, it draws hot air from inside the room and allows it to pass through the evaporator coils. The refrigerant in the coils absorbs this heat and vents it outside through the compressor coils in the condenser.

The whole process takes in three steps:

  • Evaporation
  • Compression
  • Condensation

Evaporation

The refrigerant in its liquid state circulates through the evaporator coils. While passing, it absorbs the heat and becomes a low-pressure gas. In this way, it removes the heat from the inside air by allowing it to pass through the evaporator coils. During this process, the fans present in the main indoor air conditioning unit blow or discharge cool air into your room.

Compression

The AC compressor draws the cool refrigerant from the evaporator coils in its gas state. The compressor plays its role here by compressing the low-pressure refrigerant gas while increasing the temperature. As a result, it becomes a high-pressure gas.

Condensation

This high-pressure refrigerant gas now passes through the condenser. The outdoor component fan comes into play here. It converts the refrigerant in its gas form to a liquid and allows it to flow back through the system. During this process, the condenser exhausts the hot air outside. The condensed refrigerant in its liquid form, i.e., high-pressure fluid flows through the expansion valve. Here, it again gets converted into a low-pressure liquid. It has now come back to its original state to how it was when the process first started. This completes a cycle.

This entire cycle repeats multiple times for continuous refrigeration in the air condition unit. As a result, cool air keeps flowing continuously into the room.

What Are The Different types Of Compressors Of Air Conditioners?

AC compressors are of different types, and each type has a set of benefits and drawbacks to it. Let me take you through each type and help you understand them along with their uses.

Reciprocating (Piston) Compressor

The reciprocating compressors contain two crucial parts – piston and cylinder. This is how a piston works. It moves downwards in the cylinder and reduces the pressure inside, further creating a vacuum. This process makes the cylinder force open the door and lets the gas inside.

When the gas enters, it increases the pressure inside the cylinder and allows the piston to go upwards. The piston now again moves downwards forcing the pressure to come out of the cylinder. This up-and-down motion in the cylinder is called a reciprocating motion.

These compressors are exclusively for sporadic use, i.e., for only a smaller amount of air. These are most suitable for homeowners and workshops, and other small business entities.

How Does A Reciprocating Compressor Work?

The pistons, cylinders, and valves play a crucial role in the reciprocating compressor. Here is the working mechanism of the compressor:

The piston moves upwards and downwards in the cylinder, creating a reciprocating motion. This happens when the compressor starts running. When the piston moves downwards, it increases the vacuum, further allowing the refrigerant inside.

As the piston continues to move downward, it forces the suction gas into the compression chamber. This process will keep going until the piston stops pressing downwards.

The moment the piston reaches the lowest point, i.e., touches the bottom center of the cylinder, it is where the suction part of the cycle ends.

The compressor does not stop here but it will continue to function, allowing the piston to move upwards in the cylinder. This upward motion pushes the suction valve and closes it, thereby trapping the refrigerant inside.

As the piston continues to move upward, it reduces the vacuum in the cylinder and increases the refrigerant’s pressure. This compression process will continue to a point where the cylinder pressure is slightly higher than the refrigerant’s discharge pressure.

When this happens, it pushes the discharge valve to force open, further pushing out the high-pressure refrigerant gas out of the cylinder. As the piston keeps moving upwards, the refrigerant gas continues to discharge out into the discharge line. This process will keep going until the gas comes out.

The moment the piston reaches the top center of the cylinder, the discharge valve closes. The piston starts moving again by pushing downwards. This is a cycle that keeps repeating multiple times.

Let us now try to learn about the benefits and drawbacks of reciprocating compressors.

Advantages Of Reciprocating Compressor

  • The piston and the shafts inside the compressor are easy to maintain and care for.
  • The compressor and its components are cost-effective and also easily available in the market.
  • The other advantage of a reciprocating compressor is that can comfortably work at very high pressure.

Disadvantages Of Reciprocating Compressor

  • During the process that takes place in the compressor, very high-temperature air gest released from it.
  • When the compressor operates, it vibrates a lot and also makes a loud noise, which can be irritating to many.

Rotary Compressors

What are rotary compressors? These are those compressors that use rollers and usually sit slightly to the side in a shaft, touching the wall always.

These rollers function by rotating in the opposite direction in the compressor. When this happens, the gas passes through the rollers and emerges as a higher-pressure gas while passing.

These compressors are best suitable for commercial and industrial users who require a constant flow of air. The best part of using these compressors is that they are not only durable, but also very reliable, too. And the best thing is that they can work exceptionally well in situations that require a lot of demand.

How Does A Rotary Compressor Work?

Let us try to understand the working mechanism of rotary compressors. These are usually cylindrical in shape with a discharge line present at the top of the compressor. These compressors use rollers that come directly connected to the motor’s shaft. The roller and the motor keep rotating at a similar speed.

When rotating, the roller rubs against the wall of the compression chamber. As a result, it forms an area inside that traps the refrigerant gas.

There is a movable vane inside that creates a seal with the roller because of the spring pressure. As the roller keeps rotating, it pushes the vane upside constantly against the roller. This vane acts as a separating membrane between the discharge side and the suction side of the cylinder. Just like the reciprocating compressor, the refrigerant enters and exits the compressor through the suction line and discharge line, respectively.

To help you understand the compression process better, let us discuss each step in detail here. Let us assume that the roller is blocking the discharge port. At this point, the refrigerant tries to enter the cylinder via the suction port. When it enters inside, the roller keeps rotating and seals the input from where the refrigerant entered the cylinder. When this happens, the cooling agent cannot come inside.

The roller does not stop but keeps turning inside, leaving less space for the refrigerant. While the coolant gets compressed, it increases the pressure and temperature.

As the roller rotates continuously, the refrigerant pressure keeps increasing more than the discharge lines pressure. Eventually, it allows the discharge valve to force open. As a result, the high-temperature refrigerant vapor escapes the compressor via the discharge line.

To simply put, the suction valve opens when the refrigerant gest compressed. Since the roller does not block this valve when rotating, more refrigerant keeps entering into the cylinder. This results in creating a continuous flow of compression.

Let us now try to learn about the pros and cons of rotary compressors.

Advantages Of Rotary Compressor

  • A rotary compressor is best suitable for places that require cooling on large scale like factories, offices, industries, etc.
  • It is relatively less noisy when compared to the reciprocating compressor.
  • The hot air coming out of the rotary compressor is not very hot as the reciprocating compressor.
  • The energy and oil consumed by a rotary compressor are less. However, the mechanical efficiency can go up to 90%.

Disadvantages Of Rotary Compressor

  • The rotary compressors are very expensive when comparative to reciprocating compressors.
  • You can leave your AC units without operating for a long period. You should use them for a certain period of time every day/week. Hence, they are most suitable for industries, offices, etc.

Apart from the compressors as mentioned above, there are other types, as well. They are screw compressors, centrifugal compressors and, scroll compressors. However, these are not as popular as the former ones.

Which is the best? Rotary Compressor or Reciprocating Compressor?

Both reciprocating and rotary compressors have their merits and demerits to them. If you want to know which one is the best, you need to consider certain parameters like usage, durability, etc.

If you want to purchase an air conditioning unit for your home or your office with a small space, then a reciprocating compressor is a perfect choice. If you want to have an AC unit that works for longer hours and cools a larger space, AC with a rotary compressor is all you need.

Why do you need to use the rotary compressors for a minimum amount of time?

The reason you need to use the compressor for a minimum period of time is this. The condensate water may get formed inside if you fail to use it for a stipulated time. As a result, it can cause corrosion of the metals, eventually damaging the motors.

Conclusion

To sum up, choosing an AC with the right type of compressor is entirely dependent on the usage of the unit. In this article, we discussed everything that you will ever need to select the right option.

The differences between the reciprocating and the rotary compressors, and their advantages and disadvantages, should give you sound knowledge on this topic. I am sure this article helps you to choose which one suits you the best.

If you are still sceptical about the decision-making process or need more information on this topic, write to us in the comments section below. Feel free to let us know if you have any inputs to add. Post your questions in the comments, if you have any, and tell us if this article gave you all the information you need.

We would love to hear and learn from you.

Stay home, wear a mask and stay safe!!!

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