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Scroll Compressor vs Reciprocating Compressor in HVAC

Views: 102     Author: Site Editor     Publish Time: 2024-01-25      Origin: Site


Scroll compressor and reciprocating compressors are two main compressor types used for HVAC (Heating, Ventilation, and Air Conditioning) systems. They are both positive displacement compressors, as they vacuum air into a chamber before compressing it.


Despite their unavoidable similarity, they have their differences. Depending on your requirements, these differences are capable of influencing your thoughts on which is better.



Scroll Compressor vs Reciprocating Compressor


In this article, we will dive deeper into the uniqueness and differences between scroll compressor vs reciprocating compressors, helping you decide which is best for your HVAC needs.


What is a Scroll Compressor?

The first scroll compressor was developed in 1905, but due to the lower standard of the metal casting technology, further advancement wasn’t made until after World War 2. Scroll compressor construction requires a very tight tolerance, which quality materials and advanced technological procedures can best achieve.


However, after the events of World War 2, these compressors began to be produced commercially in large quantities as refrigeration compressors. Scroll compressors are commonly referred to as a newbies in the HVAC industry because reciprocating compressor vs rotary compressor has often been up for comparison.


Scroll Compressor


Scroll compressors have a unique design, as the inside holds two interleaving spiral-shaped parts that function in unison for air compression. The two scrolls don’t come in contact, hence there is no friction or wear and tear. Because of this, scroll compressors don’t use oil lubricants and they last longer, which is one of the reasons why they are popularly valued.


Furthermore, they have a very simple design, with fewer moving parts, resulting in lesser maintenance requirements. These compressors are revered for their reliability and application where efficient and low-noise compressors are required.


What is a Reciprocating Compressor?


A reciprocating compressor is sometimes referred to as “piston compressor.” This is basically because the piston is the most important component in the compressor construction. It typically regulates the intake, compression, and discharge of air.


This compressor is one of the oldest types developed. Its origin can be traced as far back as the mid-1600s. But following advancement in technology and access to quality materials, its structure and working mechanism was changed during the industrial revolution in the late 1800s.


Reciprocating Compressor



A reciprocating compressor consists of 3 major parts: the piston, crankshaft, and cylinder. These components are connected with one another, resulting in friction and frequent maintenance.


One exceeding characteristic of this compressor that makes it popularly revered is its capacity to operate below its highest efficiency without adverse effects. This simply means that you can purchase a larger machine and grow into it. For instance, if you project that your home, clinic, office, or shop may need more air in the future as you expand, the reciprocating compressor is a great option. It will serve you effectively while you are still small and function optimally when you expand.


Scroll Compressor vs Reciprocating Compressor: Working Principle

Even though they are for intermittent air operation, their working principle differs. Here is a comparison of scroll compressor vs reciprocating compressor regarding how they work:


How does a Scroll Compressor Work?


A scroll compressor comes with two interleaving spiral-shaped parts: a fixed scroll and an orbiting scroll. While the fixed scroll is connected to the compressor housing, the orbiting scroll is attached to the crankshaft. Then, the two scrolls are locked together. Both scrolls are identical and operate in unison.


Its working principle begins when the orbiting scroll receives power from the crankshaft. It rotates in a circular motion, forming a moving pocket of space between itself and the fixed scroll. As the circular movement continues, the pocket size gradually reduces, resulting in the compression of the air trapped in between.


The compression process is simple and produces minimal noise and vibration, ensuring a very quiet operation.


How does a Reciprocating Compressor Work?


Unlike the scroll compressor, a reciprocating compressor comes with three major parts: a piston, cylinder, and crankshaft. The cylinder has an opened end and a closed end. The piston is a metal disc fitted snugly into the open end of the cylinder, while the crankshaft is connected to the piston to control it upward and downward.


When the piston goes downward, it creates a vacuum in the cylinder, allowing air to be absorbed through an intake valve. As the piston goes upward, the air is compressed and forcefully pushed out of the cylinder through a discharge valve.


This process continues, resulting in the supply of intermittent flow of compressed air. However, the upward and downward movement of the piston produces loud noise, which is not ideal for environments where silence is paramount.


Structural Design Difference between Reciprocating and Scroll Compressor


Scroll and reciprocating compressors are designed differently, which is why their working principle differs. In fact, a chunk of reciprocating compressor vs scroll compressor differences can be traced to their unique structural design.


Basically, scroll compressor structural design involves 2 major parts i.e., the two interleaving spiral-shaped scrolls: fixed scroll and orbiting scroll. They look identical and function in unison. But rather than moving together, the fixed scroll is stationary whereas the orbiting scroll continues moving till the compression process is completed.


Other parts of the scroll compressor include: the inlet, outlet, and compression chamber.


Scroll Compressor Structure



On the other hand, a reciprocating compressor structural design involves 3 major parts i.e., the piston, crankshaft, and cylinder. As the piston moves upward and downward, it controls the absorption of air and compression of the air.


Other parts of the reciprocating compressor include: the suction valve, suction pipe, discharge valve, discharge pipe, and connection rod.


Reciprocating Compressor Structure


Scroll Compressor vs Reciprocating Compressor Pros and Cons


Scroll air compressor vs reciprocating air compressor are also differentiated based on their advantages and disadvantages.


Scroll Compressor

Pros

● High energy efficiency

● Lower noise and vibration

● Compact structure with fewer moving parts

● Easy and inexpensive to maintain

● Longer service life


Cons

● Don’t scale well for large volume demands

● Sensitive to contaminants

● Higher initial cost


Reciprocating Compressor

Pros

● Lower initial cost

● Double-stage models are super-efficient

● Can adapt to both low and high demanding operations

● Can be used for a variety of gases


Cons

● Loud noise and vibration

● Requires downtime to cool because of heat caused by friction

● Shorter lifespan

● More wearing parts, leading to higher maintenance cost


Scroll Compressor vs Reciprocating Compressor on Performance

There are many differences associated with scroll compressor vs reciprocating compressor regarding performance. Understanding the individual characteristics of these HVAC types of compressors will help you make an informed decision on the one to choose.


● Energy Efficiency

In comparing the energy efficiency of scroll air compressor vs reciprocating air compressor, the former have a better edge. This is solely attributed to its design structure and working principle.


Scroll compressors have fewer moving parts; in fact, the orbiting scroll is the major part that moves during compression. These compressors construction offers increased efficiency at lower capacities. They have an extensive modulation range that supports the change of air output according to the volume of air needed. This prevents excessive energy consumption during low demand periods.


Scroll Compressor



On the other hand, reciprocating compressors have a more complex design than scroll compressors, as the piston, cylinder, and crankshaft need to work together for air to compress. They have more moving components, making them less energy-efficient as friction often exhausts great energy.


● Stability & Durability

Wholesale heat pump and air conditioning systems can be expensive, therefore it’s important that you consider the internal features, especially the compressor which is the heart of the system. Check for the stability and durability of the compressor before making a purchase.


Scroll compressors, because of their working mechanism, minimize the chances of mechanical failures. These compressors are manufactured to support applications that require low-to-medium airflow. Because scroll compressors have fewer active parts during the compression process, they don’t wear easily, making them last longer.


Reciprocating compressors, on the other hand, have a complicated working mechanism that requires the piston to move up and down through the compression process. This causes friction, results in wear over time, and damages the compressor's stability and durability.


● Cooling Capacity and Coefficient of Performance

It’s imperative to check both compressors' cooling capacity and coefficient of performance to know which is more reliable.


Thanks to their continuous compression mechanism, scroll compressors generally offer consistent cooling more efficiently. They also provide a higher coefficient of performance compared to reciprocating compressors. This contributes to better energy efficiency.


While reciprocating compressors are dependable for applications with varying loads, they have slight fluctuations in cooling consistency due to intermittent compression. They offer lower coefficient of performance when compared to scroll compressors, resulting in relatively lower energy efficiency.


● Discharge Temperature

A salient factor considered when examining scroll compressor vs reciprocating compressor is their discharge temperature.


Scroll compressors have lower discharge temperatures because of their continuous compression process and less heat generation during operation. This reduces the risk of overheating, leading to improved reliability and extended lifespan of the compressor.


On the other hand, a reciprocating compressor reacts to more causes of high discharge temperatures, particularly during high compression ratios and continuous operation. They require additional measures, such as the installation of cooling mechanisms to regulate the hot temperature for optimal performance and durability.


Charge Performance

Reciprocating Compressor


When comparing scroll air compressor vs reciprocating air compressor, ensure you look into their charge performance.


Scroll compressors have more capability to withstand refrigerant charge variations. They can operate efficiently over a wide range of refrigerant charge levels, offering flexibility and ease of maintenance.


Reciprocating compressors, on the other hand, react quickly to changes in refrigerant charge levels. Hence, it’s essential to pay keen attention to the refrigerant charge in order to maintain optimal performance.


Noise and Vibration

Another notable difference in the reciprocating compressor vs scroll compressor debate is the noise and vibration generated during operation. This is very important depending on the environment where the HVAC system will be used, especially for areas where noise pollution is not allowed.


Again, reciprocating compressors have more moving parts during operation, resulting in louder noise and vibration. Usually, the noise level ranges from 80-90 d(B)A. Thus, they shouldn’t be used in environments that demand decorum.


Meanwhile, scroll compressors generate less noise thanks to the smooth, continuous movement of the orbiting scroll. Usually, the noise level ranges from 50-70 d(B)A. This makes them more perfect in areas where noise is not allowed, such as offices, hospitals, etc.


Initial vs. Lifetime Costs

Total costs (initial and lifetime costs) are crucial factors to evaluate when considering two equipment, especially scroll compressor vs reciprocating compressor.


Scroll compressors require lesser initial investment cost because they have a simple design, constructed to be small, and feature fewer components. In the long run, their lifetime cost is low because they don’t experience much mechanical failure that could require huge expenses. They are often used for applications with lower air volume demand where cost savings are a priority.


Reciprocating compressors require higher initial investment costs because of their design complexity. Also, they experience frequent mechanical failure due to friction from the moving components. This requires additional expenses that impact the lifetime cost.


● Repair and Maintenance

You need to make detailed inquiries about both compressors' repair and maintenance requirements before deciding on the better option. Usually, this boils down again to the design construction and working mechanism of the compressors.


Scroll compressors are easy to repair and maintain because of their simple design and straightforward working mechanism. Additionally, they don’t use lubricants yet the components are tightly secure for better efficiency.


As mentioned severally in this post, reciprocating compressors have more moving components, hence, experience more wear and tear from friction. This requires frequent repairs and maintenance to ensure they continue to function efficiently. The good thing is there are some maintenance solutions you can do yourself, such as changing oil and filters or replacing valves and piston rings.


Application

The last but definitely not the least factor to consider when comparing the performance of scroll compressor vs reciprocating compressor is their suitable applications.


Scroll compressors are most ideal for applications with constant loads and demand for high energy efficiency, such as residential and commercial settings. They are also the best option for smaller-scale applications that involve quieter operation and effective performance.


Reciprocating compressors are versatile and most ideal for applications with variation of load requirements, such as commercial and industrial settings. Thanks to their adaptability to low, medium, and high demanding operations, they are the best option for handling larger-scale industrial applications.


Scroll vs Reciprocating Compressor in AC: Which One is better

Both scroll and reciprocating compressors are great options if you are looking for an air compressor for your HVAC system. Following the comparison made above, as much as it seems the scroll compressor is a better option, it’s worth noting that the reciprocating compressor has its own peculiar advantages.


For example, if you own a growing business and you need a compressor you can grow into i.e., a compressor that will still be 100% efficient when you expand, a reciprocating compressor is the perfect choice. But if you need a less noisy, inexpensive compressor with a longer lifespan for HVAC, you should go for a scroll compressor.


SPRSUN is one of the leading air source heat pump suppliers with a broad scope of knowledge and experience about air compressors, since the compressor is an essential component in heat pump equipment. Do you seek further guidance on which to choose between scroll compressor vs reciprocating compressor? You can contact us. We have experts readily available to help.


Reference:

https://en.wikipedia.org/wiki/Reciprocating_compressor

https://www.history.com/topics/industrial-revolution/industrial-revolution

https://www.achrnews.com/articles/


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