What Is The Difference Between Centrifugal Pump And Centrifugal Compressor?

By Zollent

What Is The Difference Between Centrifugal Pump And Centrifugal Compressor?

What is the difference between a centrifugal pump and a centrifugal compressor? If you are familiar with industrial processes and rotating machinery, then this might be a common concern. And this article will help you answer the question.

Centrifugal pumps and centrifugal compressors are both classified as rotating devices that impart kinetic energy to the fluid, resulting in pressure rise that helps move the fluid and other materials. So, what is the difference between a centrifugal pump and a centrifugal compressor?

Centrifugal Pump vs. Centrifugal Compressors

Centrifugal compressors and centrifugal pumps are both rotating devices that impart kinetic energy to develop pressure and move the fluid. The main difference between a centrifugal pump and compressor can be found in the properties of the fluid they act on. Both centrifugal compressors and pumps are classified under rotodynamic turbomachines. These are devices that transfer energy from rotating rotors kinetically.

A centrifugal compressor works on gaseous fluids (air), achieving significant volume reduction and energy storage. The compressed air can be stored or transferred from one point to another.

On the other hand, a centrifugal pump can work on both gases and liquids. The pump operates by developing pressure against a connected system to move a liquid medium from one point to another. The table below summarizes the differences between a centrifugal compressor and a pump.

	Centrifugal pump	Centrifugal compressor
Phase or process medium	Liquids and gases	gases
Volume compression	Relatively low volume of compression and heating	Relatively high compression volume and heating
Rotor speed	Direct motor-driven	Requires gears to increase speed
Corrosion and erosion	Material selection and consideration is important	A material consideration is not necessarily important
Cavitation	Can be a design issue but depends on the application	Not applicable
Pressure containment	The degree of importance depends on the pump type and application	Very important
Rotor sealing	Compression packing or mechanical seals	Oil and dry gas mechanical seals
Construction material	Depending on the pump type and application	Depending on the compressor type and application
Impeller stress and fatigue	Easily managed unless it is a very large pump	Is a limiting factor depending on design speed

What Are The Two Types of Centrifugal Compressor?

There are many types of centrifugal air compressors designed for specific applications. However, the two most popular ones are single-stage and multi-stage centrifugal compressors. Here is how they compare.

Single-stage centrifugal compressors

Single-stage compressors are the most popular centrifugal compressor types in the market. These compressors have a single impeller.

They also have a diffuser and guide vanes. They can be designed to offer a three to one compression ratio.

Single-stage centrifugal compressors can be integrally geared single-stage compressors or overhung single-stage compressors.

Multi-stage centrifugal compressors

Multi-stage centrifugal air compressors are designed to compress air through multiple stages. They are used in applications that require high pressure than what a single-stage compressor cannot handle.

Multiple-stage compressors have multiple impellers on the rotor.

Axial Compressor vs. Centrifugal Compressor

Axial flow compressors and centrifugal air compressors are dynamic compressor types. They all work by changing the gas velocity and converting kinetic energy to pressure. Below is a comparison between axial flow compressors and centrifugal compressors.

Axial flow compressors

Axial compressors are designed with a drum with attached blades.

These compressors require multiple axial stages to achieve significant pressure rise. This aspect makes axial compressors more complex and fragile. Modern axial compressor configurations can use up to 15 compression stages.

Axial flow compressors are highly efficient and can achieve high airflow rates. They are also designed to offer compact and lightweight compressor solutions. Lastly, axial flow compressors are relatively low-cost in terms of compression volume and cost per-flow rate.

Advantages of axial compressors

Axial flow compressors have high peak efficiency.
They have a small frontal area for airflow.
They have high ram efficiency.
They can achieve a high-pressure rise since they operate in many stages.
They have great efficiency over a narrow rotational speed range.

Disadvantages of axial flow compressors

They are complex and difficult to manufacture.
They are costly to acquire.
They are often heavyweight.
They require high starting power.
They are sensitive to disruptions in airflow.
Single-stage axial flow compressors are not as effective in increasing air pressure.

Applications of axial flow compressors

Axial flow compressors are used in different industries. Here are some of the applications of axial flow compressors.

Small-scale power stations
Gas turbines
Turbojet engines
Air separation plants
High-speed engines

Centrifugal Air Compressors

Centrifugal air compressors are another type of dynamic compressor. They are designed with a simple rotating element (impeller). The main components of a centrifugal air compressor include input, impeller, diffuser, and volute.

A centrifugal compressor sucks in air through the input and then raises the energy by the action of the rotating blades. The velocity air is raised before it is pushed to the diffuser. In the diffuser, kinetic energy is converted to pressure as the velocity reduces. The air is collected in the volute.

The capacity of a centrifugal compressor increases as the impeller speed reduces. Accordingly, centrifugal compressors can operate at high inlet pressure.

Advantages of centrifugal compressors

Centrifugal compressors are highly reliable and low maintenance.
They are easy to design and manufacture.
They are suitable for applications that require a continuous compressed air supply.
They have a high flow rate than positive displacement compressors.
They are oil-free.
They have fewer rubbing components.
They are relatively energy-efficient.
They operate on a wide rotational speed range.
They do not require a special foundation.

Disadvantages of centrifugal compressors

They have a large frontal area per-flow rate.
They are not suitable for applications that require high compression at limited pressure.
They are sensitive to gas composition changes.
They experience surging, stalling, and choking problems.
They need mounting that can handle vibrations

Applications of centrifugal compressors

Centrifugal air compressors are used in many industries and applications. Some of the most common applications of centrifugal air compressors include:

Refinery plants
Chemical and petrochemical plants
Large-scale refrigerators
Turbochargers
Superchargers
Oil and gas exploration
Food and beverage

The Bottom Line

On the surface, centrifugal compressors and centrifugal pumps may look similar and very hard to differentiate. They are both designed to move fluids in different applications. They work by converting kinetic energy into pressure energy. If you are stuck differentiating between centrifugal compressor and pump, use this article as a reference point.