General Equation of Energy, Compression Question 1

[MumtazDogan]

Hello,



I was working on the general energy equation for some thermodynamics calculations like of compressors and I found an article on web. I think it is taken from a book. I also downloaded it to the attachments section.

On equations 12-21 and 12-22, it says even for incompressible flows, the u2-u1 = qnet if there is no friction loss.

Yet, I could not understand how it is possible. For example if a compressor compresses a stream adiabatically, the internal energy will increase a lot and qnet will equal to 0.

So how it is possible ? Is the case article mentioned is only true for incompressible flows ?

Thank you.

 

[Snickster]

Only true for incompressible flow. Surely the internal energy will increase with compression work and no heat transfer for compressible flow. The entire chapter is dicussion on incomressible flow and bernouli equation. In 12.2 an attempt is made to show all energy terms but still as related to incompressible flow although a statement is made that the equation applies to both compessible and incompressible flow. But then immediately after they present equations 12-21, 12-22 but in relation to incompressible flow only.

 

[MumtazDogan]

Thank you a lot.