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Different HVAC Compressor Types

Views: 954     Author: Site Editor     Publish Time: 2024-01-25      Origin: Site


There are many types of HVAC (Heat, Ventilation, and Air Conditioning) compressors, but you can only choose one for your system. Making the right choice from the beginning is 

important because once your HVAC system is completely set up, it is best that you stick to the compressor type you started with.


Even if you have an existing system and would like to change the compressor, it’s advisable that you know the various air compressor types before making a decision.


Different Types of Air Conditioning Compressors



In this post, we will help you navigate the world of compressors, highlighting the different types, their working principles, pros, cons, and additional information that can help you make an informed decision.


What is an Air Conditioner Compressor?


An air conditioner compressor is the most vital component of the system because it facilitates the cooling cycle by circulating the refrigerant to all other parts of the system. Basically, it compresses the refrigerant as it enters into the cooling or heating system to increase its overall temperature. Once the system is heated, the gas leaves the compressor to the condenser, which is the place where the cooling process begins.


The compressor works the most; it’s the heart of the whole system. In fact, when other parts of the HVAC system are faulty, the compressor works harder to compensate for their functions, which unfortunately reduces its lifespan. But this doesn’t work the other way. When the compressor is damaged, the whole HVAC system stops working.


Thankfully, compressors manufactured nowadays are highly reliable and easy to service. With a routine maintenance schedule by a professional, you can expect your compressor to perform efficiently for longer years.


Different HVAC Types of Compressors


While there are different types of HVAC compressors, they perform the same function but have varying working principles. Let’s take a look at the common types, highlighting the distinctions between them:


Reciprocating Compressor


This is the most popular air conditioner compressor type. It was one of the first compressors invented; however, the design constantly improves as better technology and materials are discovered.


Reciprocating compressor is a positive displacement machine with intermittent airflow, meaning that it’s best used for applications that don’t require a continuous flow of air. However, this can be remedied by using a receiver tank that stores air for when continuous airflow is needed.


This compressor works on the principle of Boyle’s law, which states that “the absolute pressure released by a given mass of an ideal gas is inversely proportional to the volume it occupies if the temperature and gas remain the same within a closed system.”


This compressor typically consists of 3 parts: the piston, crankshaft, and cylinder.


The piston is connected to the crankshaft by a rod, and as the crankshaft makes rotational movement, the piston is pushed back and forth inside the cylinder. This rotational motion allows the refrigerant to be absorbed into the cylinder, compressed, and discharged out of the cylinder. During this process, two sub-components, the suction valve and the discharge valve, help prevent the refrigerant from escaping the cylinder.


When the compressor is drawing in air, the piston escapes from the discharge valve and creates a vacuum effect, which reduces the pressure in the cylinder to be lesser than the suction pressure.


During the compression stroke, the piston goes back to the discharge valve, compressing the refrigerant and increasing the pressure in the cylinder. When the pressure in the cylinder is above the suction pressure, the suction valve will forcefully close, caging the refrigerant inside the cylinder.


On the other hand, when the pressure in the cylinder increases above the discharge pressure, the discharge valve is forcefully opened, giving room for the compressed air to leave the cylinder.

Reciprocating Compressor


Pros

● Great for intermittent airflow operations

● Very efficient in low to moderate compression ratio applications

● Lower initial cost compared to other compressors like rotary compressor

● Has a simple construction, which makes maintenance straightforward

● Can be used in any environment, including clean and dirty


Cons

● Produces significant noise and vibration during operation

● Not efficient for handling high-demanding applications

● Requires a receiver tank for continuous airflow

● Requires downtime to cool because of heat caused by friction

● Shorter lifespan



Rotary Compressor


The rotary compressor is the next type of compressor you will most likely find in air conditioners and heat pump types. It’s portable and quiet, making it a preferred choice for locations without noise pollution, such as offices, residential homes, and hospitality buildings. Unlike reciprocating compressors, rotary compressors supply continuous air, thereby reducing the additional cost of buying and setting up a receiver tank.


This compressor is sometimes referred to as “helical screw compressor.” This is because it comes with two meshing helical screws (also known as rotors) that run in opposite directions to compress the refrigerant. The rotors are configured to have grooves, which allows air to move freely through the compressor.


Also, the rotors are meshed and fitted into the compressor chamber with very close tolerances. The space between the rotors is sealed with oil or specialized materials, preventing air from escaping through the mating surfaces. When the rotors begin to spin, air is forced through the chambers and trapped into a smaller space. As the rotors continue to rotate, the air is continuously compressed.


The rotary compressor can be oil-injected or oil-free. The former uses oil for lubricating and cooling the rotors, which helps reduce friction and elongates the compressor's lifespan. Whereas the latter operates without oil in the compression chamber. Instead, it uses specialized materials and coatings to ensure proper sealing and minimize friction.


Rotary Compressor


Pros

● Perfect for continuous airflow operation

● Suitable for environments that demand quietness

● Don’t need air receiver tank

● Great for industrial and high-demanding applications

● Longer lifespan


Cons

● Higher initial cost

● Can only be repaired by a skilled and experienced professional

● Must be used in a clean environment


Scroll Compressor

Also known as a scroll vacuum pump, this compressor is a positive displacement type that only produces intermittent air. There is often a debate about scroll compressor vs reciprocating compressor, especially since both are only suitable for applications requiring intermittent air supply.


One of the reasons why people prefer scroll compressors is their simple design structure, as they feature two interleaving spiral-shaped parts: a fixed scroll and an orbiting scroll. It’s also beneficial when a compact and low-noise compressor is needed.


The fixed and orbiting scrolls are identical and work together. While the fixed scroll is joined to the compressor housing, the orbiting scroll is attached to the crankshaft, then both are locked together.


As the orbiting scroll receives power from the crankshaft, it moves, thereby forming a pocket of space between the two scrolls. As the orbiting scroll continues to move at higher speed, the size of the pocket reduces, resulting in the compression of air trapped inside.


This whole process is continuous, smooth, and produces lesser torque variation, making the operation very quiet. Hence, even though scroll compressor is a newer compressor, it is fast gaining popularity.


Scroll compressors usually come in two kinds: radially scroll compressors and axially compliant scroll compressors. In the former, the scrolls move outwardly from the center, creating varying-sized pockets to trap and compress air. In the latter, the scrolls move linearly, compressing the gas by reducing the size of the pockets formed.



Scroll Compressor


Pros

● Scroll compressor has a simple design that helps reduce energy consumption

● Higher energy efficiency

● Doesn’t have many moving parts, making it last longer

● Can operate without oil, which helps to eliminate oil contamination in compressed air

● Low Noise and Vibration

● Requires little to no maintenance


Cons

● Higher initial costs

● Repairs are more challenging, requiring specialized knowledge and tools

● Not suitable for extreme operating conditions


Screw Compressor

This is one of the different types of AC compressors used in large buildings where continuous cooling is required. Over the years, it has gained popularity for its reliability, low maintenance, and efficiency in handling large volumes of air.


A screw compressor comes with two helical rotors (male and female) that are meshed closely without touching each other. These rotors are quite large, making them capable of moving a large volume of air from one end to the other. As the rotors revolve, the space between them shrink, making the air to be compressed.


This air conditioner compressor type can be designed to be oil-injected or oil-free, making it suitable for a wide range of applications, including sectors where oil contamination is taboo, such as the pharmaceutical industry.


Both rotors must be in good shape for the compressor to work efficiently. As they rotate, the screw compressor draws in air through the inlet. Continued rotation reduces the space between them, causing the air to be compressed within the chamber. Then, the air is moved toward the center of the rotors before exiting the compressor through the central discharge port located at the end of the rotors.


For the oil-injected screw compressors, lubricating oil is applied to the compression chamber not just to prevent friction but to seal and cool the compressed air.


Screw Compressor



Pros


● Wide capacity range. Can handle both small and large air volume.

● Higher energy efficiency, especially when handling large air volume

● Affordable for individuals on a tight budget

● Provides continuous and smooth air delivery with less pulsation

● Perfect for various applications, including commercial and industrial purposes


Cons


● Loud noise and vibration

● Design complexity with many intricate parts

● Increased maintenance requirements


Centrifugal Compressor


The centrifugal compressor stands out among the various HVAC types of compressors. It is greatly beneficial for extra-large HVAC systems. In fact, it’s most perfect for industrial applications.


Centrifugal compressor is designed to function efficiently at high speed. Thus, the higher the speed, the better the pumping efficiency. Another differential element about this compressor is that it has fewer moving parts (no valves, pistons, or cylinders). The only wearing parts that require frequent care and maintenance are the main bearings.


Its working principle involves using the principle of dynamic compression, which has to do with converting energy from one form to another in increasing the pressure and temperature of refrigerant. The major component of this compressor is the impeller (or a disk with radial blades), which spins the absorbed air.


Basically, it uses centrifugal forces to draw in air, then spins the air quickly using an impeller in the compression chamber. The air gains velocity in the chamber and is compressed as it gets to terminal velocity at the outside edge of the impeller. After this, the compressed air goes to the condenser.



Centrifugal Compressor


Pros

● Well-suited for extra-large HVAC systems

● Higher energy efficiency

● Has fewer moving parts, meaning lower maintenance requirements

● Oil-free operation

● Provides continuous and smooth airflow


Cons

● High initial costs

● Very complex design

● Requires specialized knowledge for maintenance and repairs


Piston Compressor

This is one of the different types of air conditioning compressors that use the reciprocating operation mechanism. In other words, it works on the principle of reciprocating motion.


A piston compressor can be constructed in single-stage or double-stage piston. For the single-stage piston, the air is compressed in a single stroke. Whereas, in the double-stage piston, air is compressed in two strokes. Firstly, it’s compressed to a medium pressure, then to a higher pressure. The double-stage piston provides better efficiency and higher output.


Typically, piston compressors have three major components which are the cylinder, piston, and crankshaft. The cylinder is made of metal, opened at one end but closed at the other. The piston is a metal disc inserted to fit into the open end of the cylinder. The crankshaft is connected to the piston, controlling it back and forth.


When the crankshaft pulls the piston forward, it results in a vacuum in the cylinder and absorbs air through an intake valve. On the other hand, anytime the piston is pulled backward, it compresses the air and then forcefully pushes it out through a discharge valve. This process happens one after the other, thereby resulting in an intermittent airflow.


Piston Compressor


Pros

● Suitable for individuals on a low budget

● Simple and compact design

● Not difficult to maintain

● Can handle varying demand levels


Cons

● Not good for applications that require consistent airflow

● High noise level

● Requires frequent maintenance

● High oil contamination


Vane Compressor


This is one of the most efficient air compressor types. It offers high power with great cooling capacity, which is necessary for applications with large cooling requirements. The Vane compressor operates on the principle of rotary motion, with the major component being a rotor with multiple vanes mounted eccentrically inside a stator.


As the rotor spins, centrifugal force pushes the vanes outward against the stator wall, creating individual chambers between the vanes and the stator. Following the rotors' continual rotation, the chambers' volume is reduced, resulting in the compression of the air trapped inside. When done, the compressed air is discharged through the outlet ports to cool the building.


There are various kinds of vane compressors. While some are designed to use oil for lubrication to reduce friction and wear between the few moving parts, others are designed to be oil-free. Meanwhile, some other kinds are constructed with variable inlet guide vanes that help improve efficiency by adjusting the absorbed air.


Vane compressors have fewer moving parts and are quieter than some other compressors, such as reciprocating and piston compressors. This makes them less prone to failure, especially as they don’t have delicate parts that can break easily. They are also ideal for environments where sound is an issue, such as hospitals and offices.


Vane Compressor


Pros


● Low noise and vibration

● Compact design with fewer moving parts

● Less prone to failure

● Continuous operation without pulsation

● Higher energy efficiency


Cons

● Can be expensive

● Certain designs require specialized professional attention

● Some kinds of vane compressor are only suitable for specific applications


Open Compressor

This is another common compressor used in heat pumps wholesale production. The open compressor is driven by an external power source, an electric motor, an engine, or even a turbine. It has a shaft that protrudes through the compressor housing. Therefore, a seal is used to stop the air from escaping through the housing.


Open compressor is popularly characterized among different types of HVAC compressors by its simple design and straightforward operation. Typically, it features components similar to those of the reciprocating compressor. Air is drawn in via an inlet valve, compressed through the movement of the piston, and discharged through an outlet valve.



Open Compressor


Pros

● Simple and straightforward design

● Very cost-effective

● Easy to maintain

● Ideal for intermittent airflow demands


Cons

● Lower efficiency compared to advanced types of HVAC compressors, such as rotary and centrifugal compressors

● High noise and vibration

● Only suitable for low-demanding applications


Hermetic Compressor


The hermetic compressor has the same working principle as the open compressor, but their structure is quite different. With the hermetic compressor, the shaft couplings and external shaft are precisely designed to be contained in the compressor properly.


Typically, a hermetic compressor functions efficiently by maintaining a fully sealed system. All the HVAC parts, including the motor and compressor, are enclosed in a single housing to stop air leakage. This design enables a continuous and reliable operation without the need for external maintenance.



Hermetic Compressor


Pros

● Integrates the motor and compressor into a single unit

● The outer shell protects the system and ensures a complete seal

● Minimized vibration and noise

● Maintenance-free

● Some kinds of hermetic compressors are designed with internal cooling systems for temperature regulation


Cons

● The enclosed design makes repair very challenging

● The design limits the availability of external cooling options

● High initial and repair costs



Semi-hermetic Compressor


The semi-hermetic compressor is a reliable option recommended by air conditioner and heat pump manufacturers for customers having difficulty choosing between open and hermetic compressors. It strikes a balance between both compressors, as the sealed housing is designed to be opened to repair or complete overhaul.


Typically, the semi-hermetic compressor operates with a degree of sealing, combining the characteristics of both open and hermetic compressors. This all-in-one compressor allows for limited access and potential serviceability.

Semi-hermetic Compressor

Pros

● Can be opened for maintenance or repairs

● The enclosed motor and compressor allows for a compact design structure

● Reduced noise and vibration

● Better energy efficiency compared to hermetic compressors



Cons

● Doesn’t allow for same level of reparability as open compressor

● More expensive



Which Type of Compressor is the Best for HVAC?

Deciding which is the best among the different HVAC types of compressors largely depends on the production process, features, and benefits. The best heat pump and air conditioner compressor type is designed with quality raw materials and advanced production processes, with strict compliance with industry standards. It’s advisable that you buy from reliable heat pump manufacturers in China like SPRSUN, which uses Panasonic DC Inverter Compressor and DC Inverter Fan Motor to manufacture HVAC.


SPRSUN produces various types of HVAC systems, including R290 air to water heat pump, which is professionally configured to meet stringent eco-friendliness, efficiency, stability, and quietness requirements. The HVAC systems are also equipped with brushless fans and sound insulation measures for the reduction of noise and vibration, making them suitable across all environments.


How to Choose the Types of Compressor for HVAC System

Choosing the right type of compressor for your HVAC system is influential to its efficiency and overall performance. Here are some vital points to help you choose rightly:


● Understand Your System Requirements: Evaluate the specific requirements of your HVAC system and compare it with the capacity of compressors available. Factors to consider include the cooling capacity, load variations, and operating conditions.


● Size: Be sure of the size of the compressor. It’s best that you check your HVAC system for the accurate size of the compressor that will fit in. Oversized or undersized compressors can lead to inefficiencies and increased energy consumption.


● Application: While discussing the different types of HVAC compressors above, we highlighted that some are ideal for low-demanding applications while others are best suited for high-demanding purposes. Therefore, choose a compressor that suits your application, either residential, commercial, or industrial.


● Energy Efficiency: The best compressors have high Energy Efficiency Ratios (EER) and Seasonal Energy Efficiency Ratios (SEER) ratings. These types of HVAC compressors offer better performance.


● Maintenance: Consider the difficulty of maintaining and repairing the compressor. Air compressor types like scroll, piston, and open compressors are easy to maintain, but others like screw and centrifugal compressors are challenging to maintain and repair.


● Noise Level: Check the level of noise and vibration the compressors generate when working. More attention should be given to this if you intend to use the compressor in an environment that demands optimal decorum.


● Costs: Compare the initial costs vs potential long-term energy savings and maintenance costs. Energy-efficient compressors are the best. Although they may have higher upfront costs, they help save money over time.


Conclusion

Great strides have been made to satisfy the varying needs of customers regarding the most suitable HVAC compressor. The result is the availability of different types of HVAC compressors, allowing users to find an option that fulfills their requirements. With each compressor’s working principle, pros, and cons, there is uniqueness, making it easier to make an informed buying decision.


Ultimately, the decision on which is the best among the various air compressor types is dependent on how clear you are in what you want, as well as the requirements you are ready to compromise.


Reference:

https://en.wikipedia.org/wiki/Rotary-screw_compressor

https://www.sciencedirect.com/topics/engineering/rotary-compressors

https://www.britannica.com/science/Boyles-law



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