CFX SCO2 turbine temperature

Cafard · August 6, 2014, 09:06

Hi all,
I try to simulate a SCO2 radial turbine,and the condition are:
1.)Inlet:1MPa(static),reference pressure:12MPa,500K(static)
2.)Outlet:0.01 kg/s (1passage [total:11])
3.)Material>reference state property>
reference temperature:500K
reference pressure:12MPa
4.)time scale:2.5e-4
5.)model size

=60mm H=30mm
6.)mesh:1.2e5 nodes(quality good)

The simulate result was finish at timesteps 5000,residuals was 1e-6 and no vibration.
The boundary condition:
a.)Outlet pressure : 0.86MPa
b.)Outlet temperature : 499K
c.)max. velocity(inlet) : 40 m/s

My question is why the outlet temperature still near 500k,temperature shuld decrease.I have read the Ansys FAQ,but still not solve the question.

By the way,is the reference state property right?

ghorrocks · August 6, 2014, 09:19

Then you have not modelled the heat transfer correctly. What wall boundary conditions are you using? What temperature are you expecting at the outlet? Why are you expecting it?

Opaque · August 6, 2014, 10:30

May I ask why are you using Static Temperature inlet condition ?

Similarly, why static pressure and not Total Pressure ? I assume you meant 1MPa gauge pressure since you are using a reference pressure of 12MPa, correct ?

Not sure what exact material you are using (incompressible, or compressible ?). An incompressible fluid will pass through the turbine and the temperature rise will be minimal (if any).

Have you tried running the "Axial Turbine" tutorial provided in the installation ?

Cafard · August 6, 2014, 12:02

the wall condition is adibadic

because I want to simulate supercritical CO2,so I use real gas material which is compressible gas.

by the reference paper (SCO2 brayton cycle),after the turbine the outlet temperature should decrease,but not just decrease 1K

the static state condition just I set,by the way,could I solve my question by set total state condition ?

August 6, 2014, 09:06	CFX SCO2 turbine temperature	#1
Cafard New Member Cafard Join Date: Jun 2014 Posts: 29 Rep Power: 12	Hi all, I try to simulate a SCO2 radial turbine,and the condition are: 1.)Inlet:1MPa(static),reference pressure:12MPa,500K(static) 2.)Outlet:0.01 kg/s (1passage [total:11]) 3.)Material>reference state property> reference temperature:500K reference pressure:12MPa 4.)time scale:2.5e-4 5.)model size=60mm H=30mm 6.)mesh:1.2e5 nodes(quality good) The simulate result was finish at timesteps 5000,residuals was 1e-6 and no vibration. The boundary condition: a.)Outlet pressure : 0.86MPa b.)Outlet temperature : 499K c.)max. velocity(inlet) : 40 m/s My question is why the outlet temperature still near 500k,temperature shuld decrease.I have read the Ansys FAQ,but still not solve the question. By the way,is the reference state property right?

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August 6, 2014, 09:19		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,854 Rep Power: 144	Then you have not modelled the heat transfer correctly. What wall boundary conditions are you using? What temperature are you expecting at the outlet? Why are you expecting it?

August 6, 2014, 10:30		#3
Opaque Senior Member Join Date: Jun 2009 Posts: 1,873 Rep Power: 33	May I ask why are you using Static Temperature inlet condition ? Similarly, why static pressure and not Total Pressure ? I assume you meant 1MPa gauge pressure since you are using a reference pressure of 12MPa, correct ? Not sure what exact material you are using (incompressible, or compressible ?). An incompressible fluid will pass through the turbine and the temperature rise will be minimal (if any). Have you tried running the "Axial Turbine" tutorial provided in the installation ?

August 6, 2014, 12:02		#4
Cafard New Member Cafard Join Date: Jun 2014 Posts: 29 Rep Power: 12	the wall condition is adibadic because I want to simulate supercritical CO2,so I use real gas material which is compressible gas. by the reference paper (SCO2 brayton cycle),after the turbine the outlet temperature should decrease,but not just decrease 1K the static state condition just I set,by the way,could I solve my question by set total state condition ?