4 replies to this topic

[Ady]

reference to this topic http://www.cheresour...gal-compressor/

I want someone to help me clear this confusion:

Forum moderator Ankur stated in the above reference topic, Differential head ( i.e discharge pressure - suction pressure) is independent of gas characteristics (i.e MW of the gas).

As per my understanding, as the gas becomes lighter, it increases the polytropic head, which drives the compressor toward overcapacity condition, this ultimately increase the load on the driver, and if the driver is unable to provide that much horsepower, the speed of the compressor decreases, and ultimately the differential head across it would also got affected.

[Bobby Strain]

Ady,
You should consult reliable reference material and draw your own conclusions.
Bobby

[fallah]

Ady,

Differential pressure will raise with a raise in MW of the gas (or gas density), but feet of head and MW of the gas are not related; means the feet of head developed by a compressor cannot be changed by changing the MW of the gas to be compressed.

Fallah

Edited by fallah, 15 September 2012 - 01:51 AM.

[reena]

Ady,
There is a simple explanation. The problem is with "head" in Polytropic head ( or adiabatic head) which is actually the energy required for compression per unit mass which when multiplied by mass flow rate gives the power required for ideal Polytropic(or adiabatic) machine - which when further divided by polytropic( or adiabatic) efficiency gives the actual power required. Your explanation for increased power requirement is explained by this while the differential head is a matter of hydraulics of the system - if the driver cannot deliver enough power, the system reaches another operating point with lower power( and flow) requirement. It is the "HEAD" in polytropic( or adiabatic) head which has caused untold problems to generations of chemical engineers!!!

[sheiko]

Ady,

Read this: http://www.cheresour...sition-changes/

And let me know if you need further explanations.