Hello everyone! I would like to bring again the topic of the compressor head:
Generally, it is stated that the the head developed by a centrifugal compressor is the same regardless of the nature of the gas being compressed. This sentence is referring to what we called actual head? Please confirm if you agree. This actual head depends on the compressor characteristics (impeller, etc.). This actual head is the ratio of the polytropic head divided the polytropic efficiency.
The next topic is the polytropic head, which definitely depends on the molecular weight, and generally the characteristics of the gas, which is going to be compressed. The gas inlet conditions affect the volumetric flow, which results in a different polytropic head.
If we think in terms of centrifugal pump, then there are two basics equations for head:
See attachment 1 (equation 1)
See attachment 2 (equation 2)
The 2nd equation can explain the very true statement that head does not depend on the liquid characteristics.
If we try to find an analogy between compressors and pumps, then
the meaning of polytropic head (compressor) is similar to the equation 1 for the pump.
the meaning of the actual head (Compressor) is similar to the equation 2 for the pump.
After this long post, my main questions are:
1) Where I can find in the books, literature explanation about the meaning of the actual head. Is the actual head what we call the head produced by compressor?
2) The derivation of the equation 1 for the pump is based on the Bernoulli's equation, simply looking at the inlet and outlet of the pump without applying the Bernoulli equation for the entire system of suction and discharge lines? If we apply the Bernoulli for the entire system then we calculate what we call the system curve.
Please share your opinion on this topic.
Thank you in advance for your time.
Kind regards,
Panos