In this post, I want to share the approximate efficiencies of centrifugal compressors and axial-flow compressors. We may have already heard about these terms: polytropic efficiency and isentropic (adiabatic) efficiency. What are those?
Polytropic efficiency is frequently used in compressor evaluation. It is frequently referred to as small stage efficiency. The polytropic process is a modification of the adiabatic process, involving an efficiency to represent actual conditions more closely. The performance of centrifugal compressors is frequently compared using the polytropic compression method.
On the other hand, isentropic (adiabatic) efficiency compares actual compression to an ideal compression (adiabatic) in which no heat is exchanged with the environment and no losses are produced (no viscosity and reversible). It is isentropic because it is adiabatic and reversible. The adiabatic process that compresses with the least amount of work is hence the isentropic process.
Figure below shows approximate efficiencies of centrifugal compressors and axial-flow compressors as a function of suction volume in actual cubic feet per minute.
The relationship between polytropic efficiency and isentropic efficiency.
I hope you find this post useful.
I posted several topic related to compressor. Please check if you need them.
- Centrifugal compressor power calculation
- Application Range of Variety of Compressors and Compressor Selection
- The Importance of Determining Number of Stages in Reciprocating Compressor and Bonus Calculation Spreadsheet
- Branan, Carl, Rules of Thumbs for Chemical Engineers, Gulf Professional Publishing, 2005.
- Stewart, Maurice, Surface Production Operations – Pumps and Compressors, Gulf Professional Publishing, 2019.
- Polytropic Efficiency Explained