Difference Between Positive Displacement and Dynamic Compressors

In this article, I will share with you the difference between a positive displacement and a dynamic compressor.

Generally, compressors are of two types; the positive displacement type and the dynamic one.

The positive displacement types are further into reciprocating and rotary types of compressors.

You might like this: Reciprocating Air Compressor: Components, Types And Working Principle

The differences that I will share with you in this article will be based on the following things;

Difference between a positive displacement and dynamic compressors (comparison table).

Based on	Positive Displacement compressors	Dynamic compressors
Mode of operation	Linear motion.	Angular motion.
The capacity of the compressors	They handle a small volume of air compression.	They are suited for high-volume applications.
Areas of application	They are used in liquid petroleum gas plants, refrigerators, chemical plants etc	They are used in ventilation systems and any area that requires a constant compressed air supply.
Operation principles of the compressor.	They operate by displacing the volume in the compressor.	Use impellers that change the velocity of air into pressure energy with the help of volutes or diffuse.
Examples of the compressors	Diaphragm. Helical screw. Liquid ring. Scroll. Lobe. Sliding vane compressor.	Centrifugal. Axial flow centrifugal compressor.
Performance of the compressors.	They offer a low mass flow rate but provide a higher pressure ratio.	They offer a high mass flow rate but provide a low-pressure ratio

Difference Between Positive Displacement And Dynamic Compressors;

These are the detailed difference between a positive displacement and dynamic compressors;

Positive displacement compressors stores a quantity of air or gas in a compression chamber which compresses it thus reducing its volume and it lead to the increase of its pressure while dynamic compressors use impellers that change the velocity of air into pressure energy with the help of volutes or diffusers.
In positive displacement compressors, the air taken into the compressor is held within a compression chamber while in dynamic compressors the air is constantly rotated with the impellers to increase its kinetic energy.

The positive displacement compressors handle small volumes of air while dynamic compressors handle a large volume of air.
The positive displacement compressors offer a higher pressure ratio since they handle small volumes of air while dynamic compressors provide a lower pressure ratio since they continuously handle air in large volumes.
The positive displacement compressor operates at lower speeds while dynamic compressors are super fast.

In a positive displacement compressor, the pressure discharge of the air doesn’t depend on the shape of the plunger as long as the plunger does its work correctly while in dynamic compressors the pressure head of the discharged air depends on the shape of the impeller blades.
The positive displacement compressors are intermittent when it comes to the air supply while dynamic compressors are continuous duty compressors.
In positive displacement compressors, a small change in compression ratio doesn’t have a very high significant change in the pressure discharge of the compressed air since they are intermittent types while in dynamic compressors a small change in compression ratio produces a marked change in compression output and efficiency since they are continuous duty compressors.

Thanks so much for reading, if you have any questions leave your comment.

See you in my next article.