Compressors, HVAC

4 Types of HVAC Compressors

Heating, Ventilation, and Air Conditioning (HVAC) are vital in hotter regions like Dubai to survive the scorching heat of the summer. But HVAC units can’t function without the compressors. Compressors are the blood of HVAC compressors without which the system can’t start at all. The problem is that there are many types of compressors present in the market and it is important to know them to make an informed buying decision. This article will dive you through four major types of compressors that are used in different HVAC units ranging from smaller applications to larger applications. You will also get to know about the working of these compressors, and their pros and cons.

What are the four types of AC Compressors?

1- Reciprocating Compressors
2- Scroll Compressors
3- Screw Compressors
4- Centrifugal Compressors

1.Reciprocating Compressors:

One of the oldest and the most commonly used compressors are reciprocating compressors. These compressors are also known as piston compressors. Reciprocating compressors work on the principle of positive displacement. This principle is used in almost 80% of the compressors including screw and scroll compressors. Reciprocating compressors are reliable, efficient, and cost-saving.

Working of Reciprocating Compressors:

By utilizing a piston pump driven by a crankshaft, these compressors pressurize the refrigerant and reduce its volume. This makes the passing of larger amounts of air possible to pass through the small tube or pipe. The pistons inside the sealed present reciprocate back and forth continuously to pressurize gas. In the whole process, mechanical energy is converted into pressure energy.

Basically, when the piston moves downwards, it lets in a vapor of refrigerant in the created vacuum and when the piston moves upwards, the vapor of refrigerant is compressed and discharged into the condenser.

The continuous reciprocation process aids in maximizing energy efficiency by operating only in the needed moment. This reduces the excessive wear and tear of the system caused by continuous operation.

Pros:

  • It is widely available.
  • It is inexpensive.
  • It is suitable for small-medium sized applications.
  • It can be utilized in residential as well as commercial applications.
  • It is energy efficient and reliable.
  • It is effective in maintaining consistent temperatures.
  • It has good pressure-generating capacity.
  • Its maintenance is quite easy.

Cons:

  • It is prone to vibration and noise.
  • It is less efficient compared to other compressors.
  • It needs frequent maintenance sessions.
  • It has chances of recurrent breakdowns due to moving parts.

2.Scroll Compressors:

Scroll compressors also work on the principle of positive displacement which means the refrigerant vapor is first trapped in the vacuum, then compressed, and then discharged. Scroll Compressors are used in various applications including rooftop units, split systems, self-contained units, and small water chillers.

Working of a Scroll Compressor:

Scroll compressors utilize two interleaving spiral-shaped scrolls to compress refrigerant. One scroll remains stationary while the other orbits, trapping and compressing the refrigerant gas.

The scroll compressors go through three operating phases. The first phase is the Suction phase in which the vapor enters the compressor through the inlet port. it creates a gradually enlarging space between the two scrolls. This expansion causes the gas to be drawn into the scroll compressor.

The second phase is called the compression phase in which the size of gas pockets reduces while the orbiting scroll stays in motion. The reduced size of gas pockets results in the
increased pressure and temperature of the refrigerant.

The third and last phase is called the Discharge Phase in which the gas exits the compressor through the discharge port after passing through the center of the scrolls. After this phase, the gas is sent to the condenser for cooling and heat exchange.

Pros:

  • Increased operational efficiency and reliability.
  • Noise-free and Vibration free operation.
  • Functional for moderate to high-capacity HVAC systems.
  • Highly Reliable and Energy-efficient.
  • Less Power Consumption.
  • Less maintenance is needed.

Cons:

  • Expensive
  • Needs specialized technicians to do maintenance tasks due to the intricate system.

3.Screw Compressors:

Screw Compressors are also called Helical-Rotary Compressors. Similar to the two previously discussed compressors, this compressor also works on the principle of positive displacement. In the HVAC industry, screw compressors are most commonly used in water chillers ranging from 70-450 tons. These compressors work in uniform motion and the compression process takes place uniformly which prevents the system from working constantly at high speeds like other compressors.

Working of a Screw Compressor:

These compressors function by trapping and compressing air or gas between two rotating screws or rotors within a specially designed housing. Like the Scroll compressor, the screw compressor also goes through three phases to compress the gas which are air intake, compression, and discharge.

The two helical rotors that make up a screw compressor are referred to as the male and female rotors. The exact helical profiles of these rotors engage or gear closely but never contact with one another. Usually, a direct drive mechanism or timing gears are used to synchronize the rotors.

Pros:

  • Highly Efficient
  • Low Maintenance
  • Smooth Operation
  • Wide Capacity Range
  • Energy-Efficient
  • Easy Maintenance
  • Ideal for harsh weather
  • Compact Size
  • Low noise and vibration
  • Durable

Cons:

  • The initial Cost is High.
  • Complex structure therefore needs specialized technicians for maintenance of ac and compressors.

    4.Centrifugal Compressors:

    Utilizing centrifugal force, centrifugal compressors speed up refrigerant gas inside a revolving impeller. The gas receives kinetic energy from the high-speed rotation, which it then transforms into pressure energy when it leaves the impeller.

    Working of Centrifugal Compressors:

    Centrifugal compressors use an impeller which is their main component. The impeller consists of a series of curved blades that are arranged around a central hub. The gas is accelerated as it passes through the blades that are aerodynamically designed.

    Firstly, the gas enters the compressor through the inlet port and meets the rotating impeller. The rapid spinning of the blades accelerates the gas and produces kinetic energy in it. Because the blades are rotating, the gas experiences centrifugal force as it passes through the impeller. The gas gains velocity and moves radially outward, away from the impeller hub, as a result of this force. After this, the gas enters the diffuser which converts the kinetic energy of the gas into the pressure energy. This whole process compresses the gas and then the gas exits through the outlet port to the condenser for further cooling.

    Pros:

    • Ideal for large HVAC systems
    • Highly efficient and reliable.
    • Compact Size
    • Low noise and vibration
    • Durable

    Cons:

    • Very Expensive
    • High Maintenance Costs
    • Complex Design

    In conclusion, a thorough grasp of the benefits, drawbacks, and operational nuances of HVAC compressors is necessary to successfully navigate the wide range of available solutions. Through an exploration of the workings and features of reciprocating, scroll, screw, and centrifugal compressors, interested parties can make well-informed judgments that meet project objectives and performance standards.

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