What is a Scroll Compressor? - SPRSUN®| Heat Pump Manufacturer

Scroll compressors are essential in the HVAC (Heating, Ventilation, and Air Conditioning) system because they affect the efficiency and general performance of the systems. It can be classified as a type of positive displacement device that has varied applications in HVAC systems. It comprises two intermeshing scrolls - one fixed and another that is orbiting, leading to a series of compression pockets.

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Its movement is in an orbital manner, thus pulling in the gas or refrigerant for compression before discharging it.

Scroll compressors are poised for uniqueness starting from their continuous and efficient compression. It gets better. The compression is through interleaved spiral scrolls. That means it eliminates the need for valves and pistons.

Such is the design that bolsters their reliability and durability. Get this: there are no plenty of moving parts. This limits the chances of wear. Compression is thus smoother in every application.

Parts of Scroll Compressors and Working Principle

Now, you got a clue about AC scroll-type compressors, so how about we break it down into parts and figure out how each works?

1. Scroll Housing: The housing encloses two types of scroll compressor components. That is the fixed and orbiting scrolls. Besides containing the scrolls, it optimizes the compression process by creating a sealed chamber.

2. Fixed scroll:  This is an immovable part fastened to the compressor frame. But it has a spiral shape designed to match the orbiting scroll. The mechanism here entails the fixed scroll interaction with the orbiting scroll to create chambers. These chambers will change in size to allow expansion and then compression, depending on the movement of the orbiting scroll. Such synchrony brings about compression, but continuously and reliably.

3. Orbiting Scroll: The orbiting scroll is linked to the motor and moves around in an orbital direction relative to the stationary scroll. It also has a spiral wrap, but its movement allows a continuous reduction and expansion of chamber volumes. As a result, this movement leads to suction that draws in refrigerant gas from the evaporator.

4. Motor and Drive Mechanism: The motor provides power for driving the orbiting scroll in its circular path. As for the drive mechanism, it's relevant when it pertains to changing the motor's rotary motion into the desired orbiting motion of the scroll. In particular, this mechanism ensures that both scrolls move together to maintain an effective compression process.

5. Suction and Discharge Ports: The scroll compressor’s suction and discharge ports allow refrigerants to enter and leave compression chambers. It is through this port that low-pressure refrigerating gases are sucked into the compressor, whereas high-pressure ones are expelled.

6. Oil System: Scroll compressors require lubrication for lower friction and smooth running. An oil system within the compressor delivers lubrication oil throughout moving parts. These pumps normally store oil at their bottom-most part. That is what is referred to as the sump component.

7. Cooling Mechanism: The scroll compressor may have a cooling mechanism that prevents overheating during continuous operation. Generally, it involves the circulation of refrigerant or oil to dissipate heat generated by the compression process.

How It Works?

The heat pump scroll compressor works by continuously sucking and compressing refrigerant gas. As it moves in a circular path, the orbiting scroll expands and compresses the refrigerant in chambers formed between the fixed and moving scrolls. Consequently, this compression increases the gas's pressure and temperature, promoting its conversion into high energy and temperature.

Then, the hot and highly pressurized refrigerant is discharged from the compressor and passed through a condenser. Therein, it will release its heat to the surrounding environment. Now, as highly pressurized liquid, the refrigerant will continue its movement through the heat pump cycle. The rationale is to get it to transfer heat between indoor and outdoor environments.

What is a Scroll Compressor Used For?

Let's discuss the application of scroll compressors.

HVAC Systems

A major role of scroll AC compressors in HVAC systems is to compress refrigerant gas efficiently. Normally, a dynamic compression mechanism will be created by the fixed and orbiting scrolls. The refrigerant will go in through the suction port into the dynamic setup, where it shall experience an increase in pressure and temperature once it is interlocked between the scrolls. Upon compression, the refrigerant leaves through the outlet port to begin another cycle of HVAC.

Use in Residential HVAC Systems

In residential HVACs, scroll AC compressors, including heat pumps and air conditioners, are widely used. Their petite design and quiet operation mode make them suitable for home settings. Moreover, their efficient cooling and heating abilities that provide maximum homeowner comfort depend on compressor efficiency alone.

Additionally, since they have a long lifespan with minimal maintenance requirements, scroll compressors become more reliable when applied in resident applications.

Application in Commercial HVAC application

The Scroll type of compressor applications in commercial HAVC and refrigeration systems are indispensable, as the compact design for installation in shopping centers, office complexes or industrial facilities is tabled.

The scroll refrigeration compressor is utilized for these purposes since it guarantees high quality and durable performance even after long usage. They can handle varying load demands and still maintain efficiency in highly demanding environments. Simply put, their use in commercial climate control cannot be overstated.

What Does a Scroll Compressor Do in HVAC?

The work of the scroll HVAC compressor in the HVAC refrigeration cycle, to reiterate, is to compress the refrigerant gas by raising its temperature and pressure. This allows the possibility for the energy, pressure and temperature, a phenomenon required by the heat exchanger such that heat gets released when it decompresses the refrigerant gas. The process results in cooling.

It would then flow through the system to the expansion valve, being expanded and cooled some more. This newly cooled gas would then be ready to take on heat from its surroundings in whatever application given, resulting in cooling in HVAC systems.

Pros of HVAC Scroll Compressor

The advantages of the Scroll type compressor offered are described below, which makes them desirable for the HVAC application:

Increased Efficiency: The continuous compression process of the Scroll compressors helps increase heat pump efficiency ratings. The design engages in a stable continuous compression cycle with both a stationary and a moving scroll cooperatively. The compressors of this scroll differ from conventional type compressors. They do not engage in lapping processes of compression or, in some instances, discontinuous cycles. Rather, their uninterrupted operation leads to lower energy consumption, optimizing the efficiency of heat pumps.

Reliability and Durability: The simplicity of the scroll compressors’ design makes them reliable and long-lasting. Fewer movable parts like pistons and valves reduce the possibility of mechanical breakdown. The orbital motion of the scrolls results in a reliable compression mechanism with minimal wear. Such a compact design extends the service life of the compressor, thereby offering robust and dependable answers to HVAC systems.

Quiet Operation: One strength of HVAC Scroll Compressors is that they operate quietly, an important quality in homes. Their silent compression is attributed to the smooth, continuous movement of scrolls and negligible vibrations, unlike other compressor types. This feature makes scroll compressors a preferred option in environments that require low noise levels. It also ensures that residents can have peaceful interiors without any disruption from an intruding HVAC system.

Compact and Light Weight compressors: The compact design of scrolls reduces volume and weight compared to conventional compressors, eliminating large components. This compression process carried out by scrolls has enabled them to be built more efficiently, thus saving space. Scroll compressors were designed with these dimensions so as to enable the compressor to fit into narrow spaces and make it easier to mount. In addition, the lightweight nature of scroll compressors gives them the advantage of being easily mounted or handled during installation and maintenance.

SPRSUN Uses Panasonic Scroll Compressor in Heat Pumps

SPRSUN, a respected heat pump manufacturer, is now concentrating on its equipment's quality to ensure enhanced functionality and energy efficiency. One of the main components used by SPRSUN is the Panasonic HVAC Scroll Compressor. It makes consistent performance and exceptional comfort for individuals possible in case SPRSUN integrates this technology into their products.

SPRSUN is committed to environmental consciousness and energy-saving efforts. Consequently, they have introduced R290 heat pumps in their product line. The refrigerant used in the R290 heat pump has low global warming potential, which means that it has minimal effect on the environment while contributing.

Conclusion

HVAC scroll compressors are integral to any HVAC system since they provide efficient and uninterrupted gas or refrigerant compression. Their benefits, such as better efficiency, reliability, silent operations, and compactness, make them the most preferred options in residential and commercial applications.

As a big player in the China heat pump market, SPRSUN knows the essence of quality parts and has decided to consider Panasonic Scroll Compressors for their heat pump systems. SPRSUN emphasizes sustainability and energy saving and thus uses R290 heat pumps that have less environmental impact but, at the same time, deliver excellent comfort and dependable performance.

In conclusion, scroll compressors are important players in the HVAC industry because of their positive impacts on the functionality and efficiency of HVAC systems. The future of HVAC systems seems bright with SPRSUN’s innovative spirit and use of quality components, among other things.

Scroll to the bottom to watch the YouTube tutorial.

Scroll compressors look something like this. They come in many shapes and sizes depending on their capacity and also the technology used inside. They convert electrical energy into mechanical energy.

We call them scroll compressors because inside we find two metal spiral shaped scrolls which causes the compression.

We can find them used in equipment like air compressors, but we will be focusing on the refrigeration versions for this video. We commonly find them used in air conditioning systems, heat pumps, rooftop units, CRAC units, walk in coolers, and we also find them grouped together for larger commercial cooling applications.

Compressors are the heart of the refrigeration system, pushing the refrigerant between all the components. The refrigerant is a special fluid which can easily change between a liquid and gas.

The compressor pushes this around the entire refrigeration system, through the condenser, expansion valve and evaporator and then back to the compressor.

Compressors simply trap a quantity of refrigerant and then compact this into a smaller volume to increase the pressure. The molecules are tightly packed together so they collide more, the pressure and temperature increases.

We send this high temperature, high pressure (superheated vapour) refrigerant outside to the condenser, which is a simple heat exchanger. The hot refrigerant flows through the tube while cooler ambient air is blown over the outside of this tube. The refrigerant is a much higher temperature so the heat flows from the refrigerant, through the tube wall and into the air.

The removal of heat causes the refrigerant to condense into a liquid. It leaves the condenser as a high pressure, medium temperature, liquid and flows to the expansion valve. These are either mechanical or electronic design. You can watch our detailed videos on how they work.

But they basically use a sensor to monitor the superheat at the exit of the evaporator. Then open and close the valve in small amounts to control how much refrigerant can flow through the evaporator, which controls the superheat value.

Superheat basically means the refrigerant has been boiled to a point where it is completely gas, no liquid can exist at that point.

The nozzle of the expansion valve holds back the liquid refrigerant, as it passes through it will expand into the empty.

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Just like a spray bottle, we force liquid through a nozzle which vaporises it, and it expands into a liquid vapour mixture.

With more space, we have a drop in pressure, the molecules can move around more so the temperature drops.

This then flows into the evaporator which is another heat exchanger inside the property.

The refrigerant again flows through the tube, with the air of the room flowing over the tube,

But this time the thermal energy of the air is going to flow through the tube wall and into the low pressure refrigerant.

 The low pressure allows the refrigerant to boil very easily.

Just like this vessel filled with low pressure refrigerant. My hand has enough thermal energy to cause it to boil.

The heat of the room is enough to boil the refrigerant, because it has a very low boiling point.

The refrigerant turns into a gas and carries the unwanted heat of the room away. 

It exits as a low pressure, low temperature slightly superheated vapour. The refrigerant is then sucked into the compressor.

When we look at the compressor we have the main protective shell, we also find the low-pressure suction inlet and the high-pressure discharge outlet. There is also an electrical connection for the power supply and controls.

This is hermetically sealed, meaning all the components are sealed inside, so we can’t access them but dirt also can’t enter and the refrigerant can’t escape . 

When we remove the shell, we see there is a mechanical section and an electrical section.

At the bottom we usually find some type of support with a bearing built into this. The shaft will sit within this bearing and rises up through the compressor. Connected to the shaft is the rotor.

Surrounding the rotor is the motor stator. There is a small gap between the stator and rotor. The stator remains stationary but the rotor rotates. The stator has a number of coils of wire, these are energised and create an electromagnetic field. The magnetic field interacts with the rotor, causing it to rotate. The rotor is attached to the shaft, so this also rotates.

Attached to the coils is a temperature sensor, typically this is a PTC type sensor. As the coil temperature increases, the PTC resistance increases. At a certain temperature the sensor will cut the power to protect the motor. Otherwise the heat of the coil will melt the enamel insulation causing a short circuit and the stator would burn out.

Coming back to the shaft. We can notice the top of the shaft is offset from the centre. The scroll will attach to this. But because the scroll is offset, we have an imbalance on the shaft, so we find some counterweights attached at the top and bottom of the rotor to correct this.

At the top of the shaft we find the compressor housing. We usually find a bearing within this to support the shaft during rotation.

The housing has some grooves cut into it. Another component, called the Oldham ring, has some ridges which will sit within these grooves, allowing it to slide back and forth. The orbiting scroll also has some grooves cut into it, these will interlock with the ridges on top of the Oldham ring, allowing the scroll to slide back and forth perpendicular to the housing and Oldham ring.

The offset of the shaft, combined with the restrictions of the oldham ring, allows the scroll to orbit without rotating on its axis.

The orbiting scroll will sit within a fixed scroll. This is connected to the shell and also the housing, so it is locked into position. When the shaft rotates, the orbiting scroll will now move within the fixed scroll. This causes compression, we will see how that works in just a moment.

The compressed refrigerant is then ejected from the centre. We typically then find a non-return valve here, this design is a simple disc valve that is pushed open to vent the refrigerant, and it drops down when the compressor turns off to stop backflow. We might also find reed valves used, these are basically thin sheets which bend to open and vent the refrigerant but will also drop down when the compressor turns off. Above this we usually find a heat shield. The refrigerant leaving the compression chamber is high temperature, so this helps prevent heat transfer back into the compression chamber.

Notice there is a void between the heat shield and  the shell, this stores some refrigerant. The refrigerant will exit the compression chamber in pulses and so this storage chamber removes these pulses allowing a constant stream to exit the compressor.

Some compressors will have a check valve at the compressor outlet instead of the compression chamber. But It works in a similar way. 

We might also find some sort of pressure relief valve built into the housing. if the discharge temperature exceeds the design limit, it will discharge the hot refrigerant gas down into the casing, the motor winding temperature sensor will detect this rapid increase in temperature and cut power to the motor.

In the bottom of the housing we find a reservoir of oil and residual liquid refrigerant. Some compressors will have a sight glass where you can inspect the oil level. Inside the shaft there is a small channel with various exits points and an opening at the lower section. As the shaft rotates, oil is sucked into this opening and the centrifugal force causes it to rise up the channel. It will exit at various points to lubricate the bearings and surfaces.

The refrigerant is sucked into the shell from the evaporator. It will typically hit some sort of shield plate because the refrigerant will be a mixture of liquid and gas. The liquid will then drop down to the reservoir while the gas can continue to flow.

The refrigerant will then flow inside the casing, through and around the motor. It seems strange, but remember the motor is sealed within the shell. A standard electrical motor uses a fan to blow ambient air over its casing and remove the unwanted heat from the stator. Electrical motors produce a lot of heat which needs to be removed or it will destroy the motor.

So, we use the refrigerant to collect and remove the heat. The refrigerant will then flow upwards and into an opening on the side of the fixed scroll.

As the scroll orbits, the walls will separate and a gap opens to allow some refrigerant inside. The scrolls then continue to orbit and the gap closes, a pocket of refrigerant is now trapped inside. The walls will continue to orbit and this forces the refrigerant to move deeper into the compression chamber towards the centre, gradually the volume decreases which increases the pressure.

Eventually the refrigerant will reach the centre where it has reached maximum compression, the scrolls then separate at the very centre allowing the refrigerant to escape, the scroll continues to orbit and the central gap closes which forces any remaining refrigerant to exit and it then collects in the dome at the top.

During compression, several pockets of refrigerant will be compressed simultaneously. Which gives a continuous output.

Scroll compressors can handle small amounts of liquid. It will pass through without damaging the scroll plates.

The refrigerant exits the compression chamber as a high pressure, high temperature superheated vapour and flows to the condenser. A crankcase heater is sometimes fitted, this keeps the shell warm in cold climates to prevent the refrigerant condensing inside, prevents backflow and also stops the lubricating oil from diluting.

Traditionally scroll compressors would just be turned on and off to control the cooling capacity. The system is either completely on or completely off, no in-between.

On larger systems with a group of compressors, they would simply be turned on or off at different stages to try and meet the cooling demand. This gives some modulation of capacity but it isn’t perfect.

Turning the system on and off causes pressure surges, bad thermal control and also causes electrical surges.

The electrical motor has a fixed speed so the only way to modulate the cooling capacity was to turn it on and off.

The diameter of the scroll, the height of the scroll wall and the motors rotational speed controls the capacity. These were all fixed properties of the design.

One method developed, known as a hot gas bypass, which uses a solenoid valve to recirculate some hot refrigerant back into the evaporator, . This creates a false cooling load on the system. It’s very inefficient but it keeps the compressor running.

Another common design is the digital compressor. A solenoid valve recirculates refrigerant back into the suction. The fixed scroll can move up and down. The pressure within the dome holds it down. But a solenoid can open to release this pressure back into the suction line. The scrolls disengage a tiny amount, so no refrigerant is compressed in this time but the motor keeps running, the valve then closes, pressure forces the scroll down and compression continues. We control this in 15 second intervals so If you need 50% capacity, then the scroll will engage for 7.5 seconds and disengage for 7.5 seconds.

Newer designs use a variable frequency drive to control the speed of the motor, so that the volume of refrigerant flowing around the system changes to match the current cooling demand. This uses an electronic expansion valve to achieve precise control. Giving us great energy efficiency and also optimal thermal control.

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