Overview of Scroll Compressor vs Screw Compressor

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The choice between scroll vs screw compressor holds a major ground in many industries. This single decision affects the heating and cooling system in various ways, such as energy consumption, efficiency, maintenance requirements, etc. Selecting the right air compressor can significantly influence long-term reliability and operational excellence.

Just like how there is a popular debate on which is better between scroll vs piston compressor, screw compressors are also big contenders in the air compressor market. But are they better than scroll compressors?

In this post, we will discuss which is better between scroll compressor and screw compressor by highlighting the various characteristics of both compressors, including their pros and cons, as well as their overall performance.

What is a Scroll Compressor?

The mechanism behind scroll compressor was ideated in , but the metal casting technology of that period wasn&#;t sufficient for their development. This is because scroll compressor design requires professional casting and tough tolerance. Development of these compressors started properly after World War 2. And in the 80s, they started being manufactured commercially as refrigerant compressors.

Till date, they are very much popular in the refrigeration industry. Especially in the last ten years, scroll compressors have become a major contender for air compression.

Typically, a scroll compressor is a type of positive displacement compressor that works via the interaction of two interleaving spiral-shaped scrolls. One scroll is stationary, while the other moves round it. The moving one doesn&#;t rotate around it, rather, it orbits. While this is happening, a series of air pockets is created. The continuous movement of the scroll gradually reduces the air pockets, giving room for compression.

Scroll compressors design offers high efficiency, smooth and quiet operation, and minimized maintenance requirements. They are often used in air conditioning, refrigeration, and some industrial applications.

What is a Screw Compressor?

The screw compressor has a rich history, dating back to when the first screw compressor was invented. However, it wasn&#;t until the s and s that technology advancement and access to quality materials allowed for practical and widespread application of screw compressors.

Originally used in refrigeration, screw compressors gained more popularity thanks to their reliability and efficiency. Their design consists of two helical rotors (male and female), which are mesh closely without touching each other. As the rotors rotate, they compress the air between them, offering continuous and pulsation-free compression.

Screw compressors are valued for their reliability, low maintenance requirements, and capacity to handle large volume of air. They are available in both oil-injected and oil-free designs, making them applicable in situations where oil-free compressed air is needed, such as electronics and pharmaceutical industries.

Screw compressors are extensively used across many industries, such as air conditioning, refrigeration, and other processes involving compressed air or gas.

Scroll vs Screw Compressor: Working Principle

Both scroll and screw compressors serve the same function of producing compressed air, but they have different working principle. This can be attributed to their mechanical design.

Below is how both compressor&#;s work, highlighting how different they are to each other.

How Does Scroll Compressor Work?

The working principle of a scroll compressor involves the interaction of two spiral-shaped scrolls: a stationary scroll and an orbiting scroll.

The stationary scroll is fixed in the compressor housing, while the orbiting scroll is connected to the crankshaft and moves around the stationary scroll. The scrolls are positioned systematically so that the pockets formed between them are open at the inlet. Then, air enters into these open spaces as a result of low pressure created by the expanding volume.

As the orbiting scroll moves, it reduces the volume of the air pockets. The reduction in volume causes the air to compress, which is then forced towards the center of the scrolls. The air exits the compression housing through a central discharge port located at the middle of the fixed scroll.

After this, the orbiting scroll continues its movement, creating a continuous compression process, and the scrolls remain in close contact, ensuring optimal efficiency and minimal leakage.

How Does a Screw Compressor Work?

The working principle of a screw compressor involves the use of two intermeshing helical rotors. These rotors are precisely machined and designed to mesh closely without touching each other. As they rotate, the compressor absorbs air through the inlet.

The rotors continue to rotate, causing the intermeshing helical screws to decrease the volume between them. As the space between the rotors reduces, the air is compressed within the chamber and the compressed air is forced toward the center of the rotors. It then exits the compressor through a central discharge port located at the end of the rotors.

In some screw compressors, particularly those with oil-injection, lubricating oil is introduced to the compression chamber. The oil doesn&#;t just serve as lubrication, it also helps seal and cool the compressed air.

After this, the rotors maintain continuous rotation, ensuring a consistent flow of compressed air. Screw compressors are loved for their efficiency, especially in handling large air volume.

Structural Difference between Scroll and Screw Compressor

The structural design of scroll and screw compressors are the primary factors that influence the differences between these two compressors.

Screw compressors consist of two helical rotors that intermesh closely but do not touch each other. The rotors are encapsulated within a cylindrical casing, with inlet and outlet ports for entry and exit of air. Generally, screw compressors appear as elongated cylindrical structures with helical rotors inside. They have a more visible oil system because of oil injection.

Scroll compressors typically consist of two interleaving spiral-shaped scrolls (stationary and orbiting). The scrolls are encapsulated within an outer shell casing, with ports on the casing for facilitating air entry and exit. Generally, scroll compressors exhibit a more compact design with visible spirals creating a scroll-like structure.

Screw Compressor vs Scroll Compressor Mechanism

Because of the differences in the design of both screw and scroll compressor, their operation mechanism differs.

These are the notable differences in mechanism:

• Screw compressors feature two intermeshing rotors that rotate in opposite directions, creating helical chambers. Whereas scroll compressors feature two interleaving spiral-shaped scrolls, one moving around the other in an orbiting motion.

• Some types of screw compressors feature an oil injection system for lubrication, sealing, and cooling. These compressors also contain an oil sump as part of the lubrication system. Scroll compressors, on the other hand, don&#;t use lubricants.

• Screw compressors are well-suited for applications requiring the compression of large volumes of air. In fact, some models offer variable capacity control for enhanced efficiency. Whereas, scroll compressors are not very reliable for handling high compression applications.

• Screw compressors have more moving parts compared to scroll compressors, contributing to their rigid maintenance requirements. Scroll compressors, on the other hand, generally have fewer moving parts, contributing to their simplicity and easy maintenance.

• Because of the many moving parts of screw compressors, they tend to make high noise and vibration. Scroll compressors, on the other hand, have fewer moving parts and a quiet operation mechanism that reduces noise and vibration.

Scroll Compressor vs Rotary Compressor Pros and Cons

Scroll compressor vs screw compressor can also be differentiated based on their pros and cons.

Scroll Compressor

Pros

• Energy Efficiency: Scroll compressors are designed with advanced technology, making them super-efficient. The technology automatically shuts down compressor pumps that are not in use and change the pressure settings to the most appropriate. This saves electricity by not generating unwanted air, which extends the lifespan of the machine.

• Ultra-quiet Operation: If you are looking for a compressor that is not just quiet, but ultra-quiet, scroll compressor is definitely your best option. They have lower noise levels, as low as 48 dBA, hence why they are suited for indoor settings and serene environments like offices, hospitals, and residential buildings.

• Compact Design: Scroll compressors have a small and compact design, which helps to save floor space that can be used for other purposes. In fact, many users keep their scroll compressors in the closet; there is no need to have a dedicated room for storage.

• Low Maintenance Requirements: Screw compressors have fewer moving parts, limiting friction between parts, which helps save on maintenance costs. Also, the compressor working system is smooth, and it automatically changes the pressure settings anytime a lower air volume is needed, thus reducing wear and tear.

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Cons

• 
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  High Initial Cost: Scroll compressors are associated with relatively higher upfront costs. This is due to the manufacturing precision required for the intricate spiral-shaped scrolls, as well as the technology used for smooth orbital motion.

• Not Suitable for Large Air Volume: These compressors are not the best choice for compressing large volumes of air. They are unreliable in applications that handle extensive air volumes demanded by larger industrial processes.

• Sensitivity to Contaminants: Screw compressors are susceptible to all kinds of impurities, including dirt, debris, and moisture. Proper filtration and maintenance is essential to their optimal performance and durability.

Screw Compressor

Pros

• Wide Capacity Range: Screw compressors exhibit a wide capacity range, making them versatile for various applications. Their design allows for efficient compression of both small and large air volumes. This flexibility in capacity makes them ideal for different industrial processes with varying demands.

• Energy-efficient: Modern screw compressors come with variable capacity control, which changes the compression ratio based on demand. This capability enhances energy efficiency, reducing operational costs and environmental impact.

• Cost-effectiveness: They are more cost-friendly compared to scroll compressors. Thus, individuals on a tight budget tend to afford them more.

• Continuous Operation: Their continuous operation without suction or a discharge valve allows uninterrupted compression. This is more beneficial in applications where a consistent and reliable compressed air source is needed.

Cons

• High Noise Level: Screw compressors make louder noise and vibration during operation because of the intermeshing helical rotors and continuous rotation. This is more common with larger capacity models. Due to the high noise level, screw compressors are not suitable for silent environments.

• Increased Maintenance Requirements: Screw compressor intermeshing rotors, especially in types with oil injection systems can introduce complexities that require regular maintenance. Monitoring and servicing the components like seals, bearings, and the lubrication system is essential for prolonged and reliable operation.

• Complex Design: Screw compressors relatively have a complex design. The intermeshing helical rotors, particularly in oil-injected models, require a more intricate design. This complexity can result in higher manufacturing costs and potential increase in certain types of mechanical issues that can only be repaired by skilled technicians.

Scroll vs Screw Compressor on Performance

There are many differences that influence the performance of screw compressor vs scroll compressor. Below, we will discuss the major factors to consider when comparing the performance of these two compressors.

&#; Efficiency

Scroll compressors and screw compressors are different in terms of efficiency and their specific design and application consideration typically determines this.

A scroll type compressor is highly efficient in small to medium-sized applications, especially for air conditioning and refrigeration systems. Its continuous compression process and high volumetric capacity make it perfect for these applications.

A screw type compressor, on the other hand, is valued for its efficiency when handling high workloads, such as large air volumes in industrial applications. Some models feature variable capacity control, which extends their capacity range, thus enhancing energy efficiency. While the initial efficiency may differ based on factors like capacity control methods and system design, screw compressors are generally capable of maintaining efficiency over a broad range of operating conditions.

&#; Stability & Durability

When considering scroll vs screw compressor in terms of stability and durability, scroll compressors are often the better option.

Scroll compressors have fewer moving parts, meaning they will have fewer points of potential failure. This makes them reliable for scenarios where stability is crucial. Also, thanks to their fewer moving parts, there is less friction, meaning the compressors will last for a long time without worries about frequent wear and tear.

Screw compressors, on the other hand, have more moving parts, meaning there is a higher chance of system downtime. Also, because of their continuous operation, they experience frequent wear and tear, which could impact the durability of the compressor. However, they can handle larger air volumes and maintain stability in demanding conditions.

&#; Noise and Vibration

When comparing noise and vibration levels of scroll compressor vs screw compressor, there are significant differences traceable to their respective designs.

Scroll compressors are known for their quiet operation and gentle vibration. The nature of the orbital motion around the stationary scroll gives a smooth compression process, resulting in reduced noise levels. This characteristic makes scroll compressors perfect for situations where noise control is paramount. Also, the simplicity of their design and fewer moving parts aids in reducing vibrations, thereby enhancing their appeal in noise-sensitive environments.

In contrast, screw compressors generate more noise and vibration during operation, which is majorly caused by the intermeshing helical rotors. However, technological advancement has propelled efforts to curb this drawback as some recent models are produced with features to reduce noise and vibration levels.

&#; Maintenance

Considering the maintenance requirements of screw compressor vs scroll compressor is crucial to their long-term performance and cost-effectiveness.

Screw compressors tend to have higher maintenance requirements due to their more complex design, especially in oil-injected models. Regular monitoring and servicing of parts like the seals, bearings, and lubrication system are crucial for the compressor&#;s optimal performance. While this complexity may contribute to increased maintenance demands, it is imperative to note that proper and timely maintenance can prolong the compressor lifespan and ensure consistent operation.

On the other hand, scroll compressors have lower maintenance requirements. Because of their design simplicity and fewer moving parts, there is a lesser demand for frequent maintenance compared to screw compressors. The basic maintenance tasks for screw compressors involve checking and replacing seals, lubricating bearings, and ensuring proper refrigerant levels.

&#; Continuous Operation

Scroll compressors are great for continuous operation. Their design, characterized by the non-stop and smooth orbital motion between the scrolls, allows for uninterrupted compression. These compressors don&#;t have suction and discharge valves, contributing to a simpler design that guarantees reliability. Thus, scroll compressors are particularly suitable for applications with a consistent and stable source of compressed air, such as DC inverter heat pump, air conditioner, and refrigeration systems.

Screw compressors are also designed for continuous operation. The intermeshing helical rotors enable a seamless and continuous compression process. However, it&#;s more reliable than scroll compressors in offering continuous operation, especially for high demanding applications.

&#;Capacity

Capacity, referring to the range of air volumes a compressor can handle, is a key factor to consider when selecting between scroll compressor vs screw compressor.

Scroll compressors are efficient in handling small to medium-sized capacities. They are often used in residential and small commercial air conditioning units, where the demand for compressed air is within their designed capacity range.

Whereas, screw compressors are designed with a wide capacity range, making them suitable for versatile situations. They are excellent in handling larger air volumes, making them ideal for industrial processes that require higher capacities. This versatility allows them to adapt to a broad range of industrial requirements, from small to large-scale applications. Some screw compressor models are equipped with variable capacity control, which makes them flexible to match output to users&#; specific demands.

&#; Cost

The cost consideration associated with screw compressor vs scroll compressor debate involves both initial investment and ongoing operational expenses.

Screw compressors have low initial investment, but the larger capacity models may have initial costs. But it is often justified by their high efficiency and performance in handling large air volumes. Also, screw compressors are cost-effective over their operational lifespan, which makes them economically advantageous and contribute to energy savings.

Scroll compressors, on the other hand, have a higher initial investment. This can be attributed to the precision required in manufacturing the intricate spiral scrolls, as well as the technology behind the smooth orbital movement. However, they are cost-effective in the long run.

&#; Application

Basically, if you need an air compressor for one or a few machines, a scroll compressor can be economical. But if you need an air compressor for your whole plant (could be 20 or 100 machines), a screw compressor is better because it provides better performance, consumes less power, and lasts longer.

Furthermore, scroll compressors are designed for simple applications. Their compact structure, quiet operation, and efficiency make them ideal for residential and light commercial applications. They are commonly used when noise control and non-stop operation are crucial.

Whereas, screw compressors are versatile and find applications across a broad spectrum, from small to large scale industrial processes. Their wide capacity range and ability to handle larger air volumes make them ideal for heavy-duty industrial applications, like manufacturing plants, refineries, and high demanding air compression systems.

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

Now that we&#;ve discussed the differences between scroll vs screw compressor, it&#;s time to choose which is better for your heat pump or HVAC (heating, ventilation, and air conditioning) system applications.

As a final recap, a scroll compressor is a perfect option for indoor settings like medical facilities, residential buildings, and corporate establishments where noise is a problem. Also, this compressor is best-suited for low to medium-level operations. The scroll compressor is not 100% efficient when used for heavy workloads.

On the contrary, a screw compressor is highly recommended for high demanding activities, hence its application in manufacturing and industrial processes industries, such as automotive, food processing, brewing, construction, and aerospace. In these industries, continuous air compression operation is needed, and this can only be offered by the screw compressor, as it supports non-stop operation without overheating.

Above is the total info about the scroll compressor and screw compressor differences. SPRSUN is a professional and reliable heat pump manufacturer with years of experience offering the best HVAC system solutions. Since the compressor is an essential part of the heating and cooling machine, SPRSUN has enough knowledge of different compressors so as to choose the best compressor for heat pumps.

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