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Isentropic Efficiency And Ambient Temperature


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#1 SadiqChemy

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Posted 08 October 2014 - 12:19 PM

I know that thermal efficiency of the gas turbine cycle will be effected by the ambient temperature but does the isentropic efficiency of compressor and turbine will be effected by the ambient temperature as well  ??? 


Edited by SadiqChemy, 08 October 2014 - 12:20 PM.


#2 Bobby Strain

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Posted 08 October 2014 - 01:22 PM

You didn't spend any time learning about turbines, did you?

 

Bobby



#3 SadiqChemy

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Posted 08 October 2014 - 01:31 PM

Hi Mr Bobby .

 

Of course , I spent a lot of time reading about gas turbine . I read a lot researches but still I have many doubts .Basically, I am working  for academic project that study the effect of the ambient temperature on gas turbine performance that drive refrigerant compressor ( propane refrigerant cycle ) which is used for cooling feed gas and lean oil in an existing  LNG plant before entering absorber . On hot climate , the  cooling capacity is decreased which will effect the recovery of C3 in absorber . I have some doubts :

 

 

  • What is the most element do you think that will effect the cooling capacity of the refrigerant in summer : gas turbine thermal efficiency - air cooler ( condenser ) - feed gas temperature . 

Edited by SadiqChemy, 08 October 2014 - 01:38 PM.


#4 Bobby Strain

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Posted 08 October 2014 - 03:46 PM

In your reading, you should have learned that compressor power is directly proportional to inlet temperature. And the mass flow is inversly proportional to the inlet temperature. So the amount of power achieved via the expander turbine is adversly affected by the temperature2

The efficiency is not necessarily temperature dependent, but is more related to air compressor/turbine wear and/or deposits. Turbine selection is based on the highest ambient temperature for which full power is required, not necessarily the maximum ambient.

 

And you led us to believe that you are a practicing engineer. You should have entered your query as a student.

 

Bobby


Edited by Bobby Strain, 08 October 2014 - 03:47 PM.


#5 PingPong

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Posted 09 October 2014 - 03:49 AM

does the isentropic efficiency of compressor and turbine will be effected by the ambient temperature as well

Efficiency of compressor will be slightly affected by inlet density, which is a function of ambient T and P and humidity. Turbine efficiency is affected by what flows through it, so turbine inlet flowrate, density, T and P.

Biggest impact on efficiency of compressor and turbine is however their actual volumetric flowrate. So you would need to know the actual flowrates, as well as have manufacturer curves to determine actual efficiency of compressor and turbine. But, as Bobby indicated, fouling and wear&tear will result in lower efficiencies than the curves indicate, as the machine gets older.

 

What is the most element do you think that will effect the cooling capacity of the refrigerant in summer : gas turbine thermal efficiency - air cooler ( condenser ) - feed gas temperature .

I don't know what you mean by feed gas temperature in this case, but I expect that in summer the aircooled condensor of the refrigerant is limiting your refrig cooling capacity.


Edited by PingPong, 09 October 2014 - 03:55 AM.


#6 SadiqChemy

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Posted 09 October 2014 - 04:41 AM

Ok how I apply this to hysys .I mean , when I change every time the inlet (suction ) temperature , I want  hysys automatically calculate the adiabatic ( isentropic ) efficiency !!!



#7 PingPong

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Posted 09 October 2014 - 06:18 AM

You can only let Hysys "calculate" the efficiency of compressor and turbine if you enter the vendor curves that show relation of efficiency versus actual flowrate.

If you do not have those curves, you can only use a typical efficiency of say 85 % as I already wrote in your other topic.






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