3 replies to this topic

[panoskagiou]

Hallo everyone!

I would like someone to explain me/remind me why the definition of isentropic efficiency for the turbine and the compressor is different.

 

Please see the attached document.

 

Thank you in advance!

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[breizh]

Hi,

Consider this resource to support your query : http://processengine...damentals.html#

note : let you use your favorite search engine .

It's also good to use a H-S diagram to visualize the work !

Good luck

Breizh 

Edited by breizh, 16 February 2020 - 06:09 AM.

[panoskagiou]

Thank you so much for the valuable documents!!!

The answer is hidden in heat engine and heat pump. 

Am I right?

[breizh]

hi ,

You need to perform a heat balance for 2 conditions : isentropic and real .

1= initial state

2 = final state

 

m*(h2-h1) = W+Q with  Q# 0 adiabatic

W :work 

Q :heat 

m : mass flow rate kg/s

hi :specific enthalpy 

 

Compression : h2 isentropic is smaller than h2 real  ; RC  = (h2 is-h1)/(h2 real -h1) <1

turbine means expansion :  h2 real is bigger than h2 isentropic ; RD = -Wreal /-W is  =( h1-h2real )/(h1-h2is) <1

 

Again use a diagram H-S where you plot h1, h2  isentropic and h2 real at P1 and P2 .

 

https://thermodynami...and-compressor/

 

My view

Breizh

Edited by breizh, 19 February 2020 - 02:17 AM.