Centrifugal Compressors Explained [Pricing, Uses & More]
Centrifugal compressors are the most common type of compressor used to power heat pumps and air conditioners. They’re also used in refrigerators, freezers, and other cooling devices.
The name comes from the fact that they use centrifugal force to compress gas into liquid form. This means they don’t need any moving parts inside them — just a cylinder with fins on it that spins fast.
What are centrifugal compressors used for?
Centrifugal compressors are one type of compressor that is used to pressurize gasses, liquids, and even air.
They are different from other types of compressors in that they use rotational energy to accelerate a fluid into a rotating impeller or drum. This causes the fluid to spin rapidly and increase its pressure.
To understand how a centrifugal compressor works, it’s important first to understand what makes up one of these machines: there is a rotating shaft that draws air into its cylinder during rotation (known as an impeller), followed by an exhaust valve that opens during this process to push out any residual gasses left in the cylinder after the rotation has finished (known as an expansion valve).
This process repeats itself over and over again.
Centrifugal compressors are used to:
- Cool down air or gasses. The most common application is to cool water and then convert it back into steam in a heat pump that heats your home.
- Create high-pressure air or gasses. This is necessary for many industrial processes such as making steel or crushing rocks into gravel.
- Compress gasses like natural gas or propane to high pressures so they can be shipped through pipelines.
- Compress air to start a fire (in combustion engines).
Advantages of Centrifugal Compressors
Centrifugal compressors are one of the most widely used types of air compressors. They have been a staple in the industry since the 1930s, and they continue to be used in many applications today. Some of their advantages are:
High-Speed Performance
Since centrifugal compressors operate at high speeds, they can provide high performance when compared to other types of compressors. A typical centrifugal compressor operates at speeds up to 10,000 rotations per minute (rpm).
This means that it can deliver a large amount of compressed air in a very short period. This makes them ideal for applications where there’s no time for waiting around for compressed air to be delivered from elsewhere.
Low-Efficiency Losses
Centrifugal compressors are typically more efficient than reciprocating compressors. This is because they have fewer moving parts than reciprocating compressors. Also, centrifugal compressors use one moving part (the rotor) instead of two (the rotor and the piston).
As a result, there are fewer losses caused by friction between moving parts and within bearings. This makes them ideal for small-scale applications where efficiency is critical.
Reliability
Centrifugal compressors are reliable because they use fewer moving parts than other types of compressors, making them less likely to break down or malfunction due to wear and tear over time.
Low Noise Levels
In addition to being fast and efficient, centrifugal compressors also have low noise levels when compared with other types of compressors such as a reciprocating piston. The main reason for this is that the compressor has fewer moving parts than a reciprocating piston compressor. This makes it possible to use a smaller motor while still achieving high efficiency.
Efficient Operation
The centrifugal design allows air to enter the center of the compressor at high speeds, increasing the pressure on the outside of the impeller.
The centrifugal action increases efficiency by forcing air through a smaller area than would be possible using other designs. The result is that there is less heat loss within the compressor as well as less energy required to operate it.
How Do Centrifugal Compressors Work?
A centrifugal compressor is made up of two main parts: a rotating impeller and a stationary diffuser. The impeller is connected to an electric motor that rotates the impeller at high speeds. The diffuser is connected to an oil-free pump that pumps oil through its passages when the impeller spins.
The spinning impeller creates a vacuum within the diffuser by pulling air through it from all directions. As this vacuum builds up in the diffuser tube, it begins pulling oil from the pump through its passages until the pressure in the diffuser reaches about 10 times atmospheric pressure (pounds per square inch).
This causes oil to flow out of the pump and into the diffuser tube where it mixes with compressed air as well as any moisture that may have been pulled into it from outside sources like rain or snow.
Once this mixture has reached optimum temperature, it flows out of an exit port at the end of the diffuser tube and into your home or business.
This generates a centrifugal force that pushes the compressed air outwards, through the diffuser. The diffuser then acts as a nozzle by reducing the velocity of the compressed air stream to approximately 50 feet per second (15 meters per second).
This slower-moving air is then pushed into your home or business via a series of pipes called a duct system.
Which Industries Use Centrifugal Compressors?
Compressors are mainly used in air conditioners, car engines, and power tools. On a larger scale, they may be used in factories as well.
The three Common Applications of centrifugal compressors are:
- Air conditioners – Compressors are one of the most important parts of an air conditioner because they help to heat and cool the air inside your home or office.
- Car engines – The engine in your car uses a compressor to create power. This is also known as turbocharging, which is when the compressor takes in high-pressure air from outside the engine and feeds it back into the intake manifold area. This increases horsepower by forcing more air into combustion chambers at top speeds.
- Power tools – A lot of power tools use small compressors that take in air from one side of the unit and pump it out on another side of the unit at higher pressures. This makes them able to operate faster than if they were using just normal air pressure from outside sources like an electrical outlet or battery pack.
- Aerospace – Centrifugal compressors are used to pressurize the liquid oxygen (LOX) and liquid hydrogen needed for rocket engines. They are also used to provide pressure for hydraulic systems on aircraft, space shuttles, and other vehicles that use hydraulic power steering.
- Agriculture – In agriculture, centrifugal compressors are used to provide air for agricultural pumps, sprayers, and various other equipment.
- Oil & Gas – In this industry, centrifugal compressors are used to send natural gas from oil wells to processing plants where it is separated from other liquids before being sent through pipelines to end users.
- Power Generation – Centrifugal compressors are used in power plants as part of the process of cooling steam down so it can be condensed back into the water again, which is then returned to the boiler for reuse.
- Chemical Industry – Compressors are used to pressurize liquids such as water and refrigerants that are used by chemical plants. These liquids are then transported via pipelines to other locations.
- Electronics Industry – Compressors are also commonly found in electronics manufacturing facilities as well as data centers where they are often used for cooling purposes.
3 Main Parts of A Centrifugal Compressor
The three components of any centrifugal compressor are the impeller, shaft, and bearings.
Impeller
The impeller is essentially a rotor attached to a shaft inside the compressor housing. It’s designed to spin at high speeds, usually between 10,000 and 15,000 RPM. As it turns out, this speed is just about right for producing suction on an intake port and pushing air through an outlet port.
Vanes
The vanes are what help direct the flow of air into the compressor housing. They’re typically shaped like a blade or paddle, but they don’t have any blades or paddles themselves. Instead, they use centrifugal force to direct airflow from one side of the vanes to another.
Impeller Housing: The impeller housing is actually just a cylindrical enclosure for the impeller and other components we’ve already discussed. It also helps keep dust and debris out of your compressor by keeping them contained within the unit itself.
Shaft
The shaft is the main part of the centrifugal compressor, which is responsible for transferring energy from one part of the machine to another. It connects the impeller with the housing and bearings within it.
The shaft is usually made from a strong and durable material such as steel or cast iron. Shafts are usually hollow to allow lubrication through them. This prevents wear on the bearings and allows for easy maintenance.
There are two types of shafts: single shafts and double shafts. A single-shaft centrifugal compressor has only one shaft, while a double-shaft centrifugal compressor has two separate shafts — one for each rotor.
Bearings
Bearings are what allow rotational movement between parts by reducing friction between them as they spin at high speeds.
Centrifugal compressors have ball bearings or sleeve bearings between the rotating shaft and stationary housing to help transfer energy from one part to another while keeping them aligned with each other during operation.
Bearings are typically made of steel or brass, although some older models may use bronze instead of steel due to its durability and ability to withstand high temperatures better than most other materials used in production today.
What are the two types of centrifugal compressors?
There are two basic types of centrifugal compressors:
- single-stage
- multistage compressors
A single-stage compressor uses one rotor and one stator to produce a single pressure level. The rotor is mounted on a shaft that turns at a high speed, while the compressor housing or casing encloses the rotor and contains working parts such as valves, gears, and bearings.
A multistage compressor has more than one stage — usually three for automotive applications and up to eight for industrial compressors. Each stage may have its own drive shaft (single-shaft) or be coupled to an intermediate shaft (double-shaft) between stages.
The main purpose of multiple stages is to increase the total output capacity while maintaining system efficiency by increasing pressure ratios with each additional stage added.
An advantage of using more stages is that it allows you to use smaller-diameter rotors that rotate at lower speeds so they can handle higher pressures without overloading them or losing efficiency due to friction losses in their bearings.
The difference between a reciprocating and centrifugal compressor
A reciprocating compressor and a centrifugal compressor both compress air, but they do it in very different ways.
Reciprocating Compressor
The reciprocating compressor works by having pistons move back and forth inside cylinders to compress the working fluid (gas). This type of compressor has been around since the early years of refrigeration and is still very common today.
Reciprocating compressors are often used in residential applications due to their relatively low cost and simple design. They can be designed for variable speed operation by adding an adjustable frequency drive (AFD) to control their speed.
Centrifugal Compressor
The centrifugal compressor uses rotating impellers (rotors) to compress gasses or liquids. The impelling force comes from the high-speed rotation of the rotor blades, which causes a high-pressure area on one side of the blade and a low-pressure area on the other side.
A number of small-diameter blades are positioned on a shaft within an enclosed housing that contains compressed gas or liquid at atmospheric pressure; this housing is called a volute casing because it resembles an inverted bell shape when viewed from above.
What is the efficiency of a centrifugal compressor?
The efficiency of a centrifugal compressor is the ratio of the power input to the power output.
This is a measure of how much energy the compressor uses to compress air. The higher the efficiency of a compressor, the less energy it uses to perform its task and thus, theoretically, the less energy it will consume.
The efficiency of a centrifugal compressor is typically expressed as a percentage, although it can also be expressed as an absolute value in kilowatts (or other units). For example, if you have a 100 kW centrifugal compressor with an efficiency rating of 80%, then it will consume 80 kW of electrical power and produce 20 kW of compressed air.
Typically, centrifugal compressors are very efficient — they can achieve efficiencies over 90%. However, there are some factors that can impact this figure and cause it to drop below 90%.
For example, if there is friction in your piping system or valves (which isn’t uncommon), this will increase your energy consumption because more energy will be needed to overcome this friction.
How Much Do Centrifugal Compressors Cost?
On average, a centrifugal compressor typically costs between $10,000 and $50,000.In general, you should expect to pay somewhere around $8000 for medium size unit to more than $1 million for a large industrial machine.
The cost of a centrifugal compressor will depend on the size of the unit, as well as what type of application or in what industry it will be used.
Small Centrifugal Compressors range from $500 to $5,000. Small centrifugal compressors, which are often used in home workshops and garages, typically have a capacity between 5 and 15 horsepower (HP).
The good news is that centrifugal compressor costs have fallen a fair bit in the last few years, mostly due to advancements in components and materials, specifically in efficiency.
Summary
Whether you’re looking to buy your own or just want to get an idea of how much maintenance would cost, you should now be armed with enough information to help make a decision!
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