10 replies to this topic

[ramsingh_mech]

Dear all,

 

Anybody share a method to findout the power required to drive the compressor Pls...

 

I heard the thumb rule - for 1 M3/min capacity compressor the power required is about 7.5kW.and i tried to match with my project compressors(Air Compressors only) also , Its really working.

 

But pls guide me a actual concept and calculation method for this.

 

Regards

RAM

Mechanical Engineer.

[thorium90]

Branan's Rules of Thumb for Chemical Engineers (Fifth Edition) has a nice part on it. Steve Hall could tell you more, he wrote the book...

[ramsingh_mech]

Thanks thorium.....

[thorium90]

And,

http://www.cheresour...n-calculations/

[paulhorth]

Ram,

Don't you think it likely that the power of a compressor could depend on the pressure ratio, not just the suction volume? Don't you think it's possible that the type of gas might make a difference, too? Why should you expect your rule of thumb to work for every case?

 

There is a sandard equation for compressor power which includes these factors, readily available in any textbook on the subject. You could try looking in the GPSA Data Book for a start.

 

Paul

[ramsingh_mech]

Dear Paul,

 

You might be missed the word.

 

I can think,  that is the reason i have mentioned (Air Compressors Only). i know this do not applicable for all types of gas.and regarding pressure ratio , Normally in evrery industry compressed air pressure is around 7-8 Barg for utility purpose. I raised this topic with these considerations.sorry,i would have come with much detailed to avoid the confusion.

 

I am also not comfortable with thumbrules paul, thanks for your suggestion.

 

Regards

RAM.

Edited by ramsingh_mech, 21 March 2013 - 05:54 AM.

[ramsingh_mech]

Dear thorium,

 

Thanks for the link, i am using this right now........

 

Regards

RAM

[paulhorth]

Ram,

 

I have worked on a number of projects where the instrument air compressors were at 12 or 13 barg, not 7 to 8 barg. Your rule of thumb would not work for that pressure would it?

Why use a rule of thumb, with its hidden assumptions etc, when it is just as easy, and more accurate, to do the job properly?

 

Paul

[Art Montemayor]

First - and foremost - WHAT type of compressor are we discussing here?

 

It makes a big difference - as you will find out from Steve Hall.  You have to be specific if you want a specific answer - even a "Rule of Thumb".  Additionally, no one can make a relation between a volumetric capacity and the power requirements without stating the compression ratio involved.  In other words, you can't calculate the work required without first stating the "head" (or the "distance") to be covered by the volume of air.  It can't be done.

[ramsingh_mech]

Paul,

 

Its true , using concpet and formulaes always better than using thumbrules. But thumbrules are some times interesting when comparing with our resolved calculations. yes there may be 12-13 barg Compressed air pressures. But what i have given is for 7-8 barg (Centrifugal Compresssor).

 

Finally , i have gone through GPSA data book as suggested by you , i feel really good, its a must handbook for everyEngineer.

 

Thanks .

 

Regards

RAM.

[ramsingh_mech]

Art,

 

Raised thumbrule topic is for Centrifugal type air compressor , Pressure 7-8 Barg range.

 

Reagrs

RAM