Thanks Art,
By 'Mechanical', I meant Centrifugal compression.
I know thermal compressors as name suggest this is not MECHANICAL compression.
Few of us should understand that when we discuss some practical issue - its not necessarily from students or for academic purpose (Though we all r students as far as learning is concerned throughout our whole life).
I am discussing practical aspects, as mentioned in my first post very clearly....PRACTICAL & MECHANICAL COMPRESSION