Reference State Properitues

Cafard · July 21, 2014, 03:41

Hi all,
I have some questions with Reference State Properitues.
When I read CFX-Pre Guide I found the fpllowing paragraph:

"When defining specific heat capacity, you must set a reference temperature and reference pressure.
These quantities are used only to define a reference level from which some derived quantities, such as
a change in enthalpy or entropy, are calculated. The defaults for these values are 1 atm and 25°C.
However, you should set these values to values that are representative of the average temperature and
pressure that will occur in your model. You should also consider table limits as well in that it is better
to choose reference values that fall in the valid range for table property generation. "

The original setting is 297.15 K & 1 atm.
If my working fluid doesn't reach the refernce state,
should I change the setting?

ghorrocks · July 21, 2014, 07:01

The reference pressure should be set to a typical pressure present in your simulation. Likewise the reference temperature should be a typical temperature.

Cafard · July 21, 2014, 07:24

excuse me
what's the typical state??

If my working pressure at 1 Mpa~ 2 Mpa,the typical pressure is still 1 atm??

ghorrocks · July 21, 2014, 07:54

No. Then your reference pressure should be something in the range 1MPa-2MPa.

July 21, 2014, 03:41	Reference State Properitues	#1
Cafard New Member Cafard Join Date: Jun 2014 Posts: 29 Rep Power: 12	Hi all, I have some questions with Reference State Properitues. When I read CFX-Pre Guide I found the fpllowing paragraph: "When defining specific heat capacity, you must set a reference temperature and reference pressure. These quantities are used only to define a reference level from which some derived quantities, such as a change in enthalpy or entropy, are calculated. The defaults for these values are 1 atm and 25°C. However, you should set these values to values that are representative of the average temperature and pressure that will occur in your model. You should also consider table limits as well in that it is better to choose reference values that fall in the valid range for table property generation. " The original setting is 297.15 K & 1 atm. If my working fluid doesn't reach the refernce state, should I change the setting?

July 21, 2014, 07:54		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,872 Rep Power: 144	No. Then your reference pressure should be something in the range 1MPa-2MPa. Cafard likes this.

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July 21, 2014, 07:01		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,872 Rep Power: 144	The reference pressure should be set to a typical pressure present in your simulation. Likewise the reference temperature should be a typical temperature.

July 21, 2014, 07:24		#3
Cafard New Member Cafard Join Date: Jun 2014 Posts: 29 Rep Power: 12	excuse me what's the typical state?? If my working pressure at 1 Mpa~ 2 Mpa,the typical pressure is still 1 atm??