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Scroll vs Rotary Compressor in HVAC

Views: 736     Author: Site Editor     Publish Time: 2023-12-27      Origin: Site


The comparison of scroll vs rotary compressor has long been discussed. Both compressors are designed for use across a wide range of applications, including residential and commercial domains. However, each of them have a unique structure, mechanism, and working principle, which impacts their efficiency.


Similar to the reciprocating compressor vs rotary compressor debate, scroll compressors are also popular and are often recommended by professionals. But should you choose them over rotary compressors?


Scroll vs Rotary Compressor



In this article, we will discuss extensively on both compressors, enlightening you on which is best.


What is a Scroll Compressor?


A scroll compressor is a type of positive displacement compressor used in various applications, notably HVAC (heating, ventilation, and air conditioning) systems. It features two interleaving spiral-shaped components: a stationary scroll and an orbiting scroll.


Scroll Compressor



Scroll compressors have a continuous, smooth compression process, which enhances their output rate. They are commonly known for their energy efficiency, consistent operation, and relatively simple design.


What is a Rotary Compressor?


Rotary compressor, which is sometimes referred to as “rotary screw compressor,” is also a positive displacement compressor widely used for HVAC systems across residential and some industrial settings. It features a shaft that houses two blades that rotate with close clearances next to each other.


Rotary Compressor



Rotary compressors are valued for their compact size, high capacity, and smooth operation. Hence, they are ideal for applications with limited space and continuous air demand.


Scroll vs Rotary Compressor: Working Principle


Despite performing the same function, scroll and rotary compressors have different working principles. Below is a comparison of how scroll compressors work against how rotary compressors work.


How Does Scroll Compressor Work?


The scroll compressor features two interlocking spiral-shaped scrolls. One is called “stationary scroll” while the other is called “orbiting scroll.” These scrolls are generally made of high-strength materials like stainless steel or aluminum. The interlocking scrolls create a continuous seal, canceling the need for piston. This tight design also minimizes internal leakage and energy loss.


Its working principle involves the orbiting scroll moving round the stationary scroll, thereby creating a series of air pockets between them.


The compression process starts when the orbiting scroll begins to rotate, causing air to be drawn into the chamber. As the orbiting scroll continues its eccentric movement, the air is gradually compressed to the scroll set center. As the volume of the air reduces, there is an increase in pressure. Then, the compressed air is forced out through an outlet port at the center of the scrolls.


How Does a Rotary Compressor Work?


The rotary compressor features a pair of helical screws (known as rotors) that rotates within a compression chamber. The screws are machined with helical lobes that intermesh with each other, resulting in a series of compression pockets. As the screws rotate, the pockets volume reduces, thus compressing the air trapped inside.


Its working process starts when atmospheric air enters the compressor through an inlet port. Then, the rotors draw in the air, which gets progressively compressed as it moves across the rotating screws. As this is going on, the air pressure and temperature increases. The rotors intermeshing lobes ensure a tight seal, making sure there is no opening for backflow. Once the compressed air gets to the end of the rotors, it leaves the chamber through a discharge port.


The rotors require precise alignment and reduced friction to guarantee compression efficiency. This is done by using high-quality bearings and a reliable lubrication system. The lubricant not only ensures close tolerance between the rotors but also helps spread the compressed air, facilitating the overall performance and longevity of the compressor.


Structural Difference between Scroll and Rotary Compressor


Scroll and rotary compressors are designed differently, which is why their working principles are unique. A large part of the scroll compressor vs rotary compressor can be traced to their mechanical structure and design. For instance, a scroll compressor’s compression chamber is at the top, but the rotary’s compressor’s compression chamber is located at the bottom.


Also, aside from the stationary and orbiting scroll, a scroll compressor has many smaller subcomponents, including a motor, a thermal protector, an internal pressure relief, bypass valves, a discharge check valve, an overload protector, and many more. Components like thermal protector, discharge check valve, and overload protector help to protect the compressor from damage.


On the other hand, a rotary screw compressor features a motor, a cylinder, an accumulator, a crankshaft, a roller, a main bearing and a sub-bearing, as well as a vane.


Look closely, you will observe that a scroll compressor and a rotary compressor don’t share similar components except for the motor. Hence, why they operate differently.


Scroll Compressor vs Rotary Compressor Mechanism


Because of the different components used in each compressor’s design, their operation mechanism differs.


These are the notable differences in mechanism:

  • In a scroll compressor, the compression process happens inside the scroll wrap with the help of the scrolls. Whereas, in a rotary compressor, the compression process takes place inside its compression chamber with the help of the roller’s rotational movement and the vane’s vertical motion.


  • A scroll compressor compresses air continuously, but rotary compressor only compresses air on the completion of one rotation.


  • A scroll compressor offers lower noise and vibration because it compresses air continuously and has a torque fluctuation of 50%.


  • A scroll compressor compresses air using the circular movement of the scroll, but the rotary compressor compresses air by changing the air volume through a rotational movement of the roller.




Scroll Compressor vs Rotary Compressor Pros and Cons


Scroll compressor vs rotary compressor can also be differentiated based on their advantages and disadvantages.


Scroll Compressor


Pros


  • High Efficiency: Scroll compressors are appreciated for their excellent energy efficiency due to continuous compression without pulsation, resulting in optimal performance and reduced energy consumption. This helps with saving costs in the long run.


  • Low Noise: Scroll compressors have a quiet operation system, making them ideal for noise-sensitive environments, such as residential buildings or offices.


  • Compact Design: These compressors are designed to be compact and lightweight, allowing for easy installations in tight spaces. The small size makes them perfect in situations where setup area is limited.


  • Lesser Maintenance Requirements: In addition to having a compact design, scroll compressors have fewer moving parts, resulting in lesser maintenance requirements. Also, the compression process is smooth, offering reduced wear and tear.


Cons


  • Limited Capacity: Scroll compressors are most ideal for low to medium capacity applications; they are not suitable for high capacity applications. Multiple scroll compressors will be required for efficiency in high applications. This will increase the initial investment and make the system complex.


  • Sensitivity to Contaminants: These compressors are prone to contaminants like dust, dirt, debris, and moisture. Adequate filtration and maintenance are important for their longevity and optimal performance.


  • High Initial Cost: Scroll compressors have a high initial cost, which makes them expensive for people on a tight budget. However, in the long run, their reliability and energy efficiency offsets the initial cost.


Rotary Compressor


Pros


  • Wide Capacity Range: Rotary compressors can handle higher capacity requirements, making them suitable for larger HVAC systems and high-demand applications. These compressors are available in various types, such as rotary vane or rotary screw, thus offering versatility for different applications, including high or low temp heat pump.


  • Compact Design: Rotary compressors are compact in size with a very simple design structure. This makes them simple to set up and maintain, thereby minimizing operational costs and downtime.


  • Continuous Operation: These compressors offer a steady supply of compressed air, making them ideal for industrial operations that require substantial airflow.


  • Cost-effective: Rotary compressors have a more cost-friendly initial cost compared to scroll compressors. Hence, they are affordable to individuals on a budget.


Cons


  • Noise Level: Depending on the type, rotary compressors can produce more noise during operation.


  • Maintenance Requirements: Rotary compressors have more moving parts when compared to scroll compressors, hence their higher maintenance requirements.


Rotary vs Scroll Compressor on Performance

There are many differences associated with rotary compressor vs scroll compressor regarding performance. Below, we will discuss the key factors to consider when comparing these two compressors:


• Efficiency


Rotary compressors, because of their positive displacement design, offer high efficiency across a broad range of operating conditions. This guarantees optimal performance in numerous applications, resulting in reduced energy consumption and lower running costs.


Scroll compressors, on the other hand, have a unique scroll construction that offers great efficiency at lower capacities. They are great for maintaining stable air pressure, making them perfect for applications where steady and precise airflow is essential. Their extensive modulation range makes them capable of changing air output according to the required airflow needed. This helps to save energy by avoiding excessive energy consumption during low demand periods.


• Stability & Durability


Both rotary and scroll compressors are strong, stable, and reliable. However, rotary compressors are often preferred for tedious applications. Their robust construction makes them capable of withstanding high applications like industrial settings where continuous and demanding applications are norms of the day. Rotary compressors are more stable and reliable under heavy workloads.


Scroll compressors, on the other hand, perform excellently for applications that require consistent and low-to-medium airflow. Their design features fewer moving parts, minimizing the chances of mechanical failures and making them reliable for low-to-medium applications.


• Noise


In this section of the scroll vs rotary compressor debate, scroll compressors have the upper hand. They have a simple design, involving few moving parts and a smooth operation system. This results in low noise and vibration. Hence, they can be trusted in silent areas like residential homes, offices, and hospitals.


Rotary compressors tend to produce more noise and vibration during operation. Depending on the industry, the noise might not be an issue. For example, manufacturing industry workers are accustomed to other machines making noise during operation. However, some dependable heat pump or HVAC manufacturers would use soundproof cotton to reduce the noise when equipping the rotary compressor in the machine, since the performance of the rotary compressor is the best.


• Continuous Operation


Another factor worth considering in the HVAC scroll compressor and rotary compressor debate is their operation system.


Compared to rotary compressor, scroll compressor is not the best for when continuous flow of compressed air is needed. Their working mechanism involves an intermittent compression process, which causes slight fluctuations in airflow. Thus, why they are better used for applications that don’t necessitate continuous and uninterrupted air output.


On the other hand, you can trust rotary compressors for applications where continuous flow of air is paramount. These compressors’ design ensures uninterrupted and steady airflow, making them a better option for industries that rely on consistent compressed air delivery.


• Application


The choice between scroll compressor vs rotary compressor largely depends on the intended application.


Scroll compressors are prevalent in residential and light commercial HVAC systems. They are used in applications that require precise and stable airflow such as electronics, food and beverage, clean rooms, and laboratories.


On the other hand, rotary compressors, particularly the rotary screw and rotary vane types, are usually used in larger HVAC systems, such as commercial and industrial air conditioning applications. However, it also played a great advantage in the residential heat pump. They are suitable for heavy-duty industrial applications that demand a continuous and reliable compressed air source. These applications include manufacturing processes, construction sites, and automotive workshops.


• Suitable Refrigerant


Rotary compressors are compatible with different types of refrigerants. They can handle a wide range of refrigerants, including common ones like R-410A and newer environmentally friendly options like R-32 and R290, the flammable and explosive refrigerant. Their versatility in working with various refrigerants makes them adaptable to evolving industry standards.


Scroll compressors, on the other hand, are best-suited for newer environmentally friendly refrigerants like R-410A, a common option used in modern HVAC systems because of their eco-friendly nature. While some scroll compressors can be paired with other refrigerants, they are not generally compatible with multiple refrigerants like rotary compressors.


• Costs


The total costs, including the initial investment cost and the operational cost, are crucial to the preferred option to choose between rotary compressor vs scroll compressor.


Rotary compressors have a higher initial cost than scroll compressors mainly because of their larger size, design complexity, and capacity to handle heavier workloads. With high efficiency and ability to perform heavy operations, rotary compressors help save energy consumption, thereby reducing operational costs over time.


Scroll compressors, on the other hand, are often more compact in size, simpler in design, with lower initial investment cost. They are commonly used for operations with lower air volume demands where cost savings is a priority. Their capacity to modulate air output according to the required demand helps reduce energy wastage when there is low airglow demand.


• Maintenance


Regarding maintenance, both rotary and scroll compressors require regular servicing and upkeep. But, rotary compressors require more frequent maintenance because of their design complexity and heavy workload capacity. Usage across high industrial applications can weaken the compressor, making it less efficient. Hence, why it’s important to carry out frequent servicing and upkeep.


Rotary or Scroll Compressor: Which One is better for Heat Pump or HVAC


From our discussion above, both rotary and scroll compressors have their benefits and drawbacks and can be used for different applications. Now, you are to consider which is best for you. The best way to do this is to prioritize your needs and environment. It’s always a good idea to seek the assistance of an air compressor professional to guide you on the right path.


SPRSUN is one of the prominent and largest heat pump manufacturers with vast knowledge and experience in air compressors since the compressor is the essential component of heat pumps and HVAC. And in terms of heating and cooling performance, SPRSUN uses a Panasonic rotary compressor to equip the heat pump. You don't need to worry about the quality.


Do you still need further guidance on choosing the best option between scroll vs rotary compressor? You can contact us; we are always ready to help.


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