Power savings in a gas compressor 1

[Suddo]

I was reading an article on compressors and came across the following statement : "A reduction in the delivery pressure by 1 bar in a compressor would reduce the power consumption by 6 – 10 %.
What are the underlying calculations and/or the principle behind this result?

 

[zeusfaber]

I guess there has to be a value of initial delivery pressure for which that is true - and that it could be determined empirically.

A.

 

[rotw]

It does not make sense or it is a statement taken out of context.

Required Power = Total Head (or Enthalpy differential) x Massflow [kJ/kg x kg/s which is analog to kJ/s or kW]

Enthalpy differential across compression path depends on several factors, including: initial and final (pressures and temperatures) and gas composition.


Life is not about waiting for the storm to pass. It's about learning dance in the rain.

 

[Suddo]

@rotw and @zeusfaber, this statement is considering the fact that all things remaining same,if somehow I am able to reduce the pressure requirement of the process and hence there is a decrease in the discharge pressure requirement, there is scope of power savings.

This was given as a general thumb rule.

Therefore I am looking for an equation relating Power consumed in a compressor to the Pressure (or P2/P1 maybe). Is there some relation of that sort?

Also, thank you both of you for trying to help me out, much appreciated.

 

[LittleInch]

Have you not heard of google?

search on shaft power calculation gas compressors and gems like this turn up

http://enginerng.blogspot.com/2015/04/compressor-power-calculation.html

https://www.enggcyclopedia.com/2011/11/compressor-power-efficiency-equations/

I'm sure there are many more.

The principle is that less work is being done by the machine to the gas and therefore power goes down for the same volumetric or mass flow.

The amount will depend on the relative pressures. I'm taking a guess that the pressures referred to in your OP were probably "standard" air pressures you see in plants of around 7 bar / 100 psi.

If you reduce this by 1 bar then you'll see a much bigger reduction in power than if you reduced a compressor running at 70 bar/ 1000 psi.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Suddo]

@LiitleInch, sorry I went into the wrong links earlier.
This was very helpful. Thank you.

 

[rotw]

some interesting online tools from OEM, useful for power and head calculations

http://yrsp.elliott-turbo.com/public/comp_perf/index.jsp

https://solarturbines.secure.force.com/GasCompCalculator

http://cirs.dresser-rand.com/turbocalc/

Life is not about waiting for the storm to pass. It's about learning dance in the rain.