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Old   March 30, 2012, 05:16
Red face question need answer, pls
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Safia
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Hi all
I'm using the idael gas material fro my simulation; and when I modify the air properties as function of temp., my results become the same if I used constant properties..(did not make sence)!!!
So what you think the wrong come from???
I'm looking to hear from you soon.

Please any input can help.
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Old   March 30, 2012, 05:35
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May be the temperature variation in your simulation is not significant enough to cause any change in results. So even when you use temperature dependent properties, the results are similar.
Also, I am assuming here that the properties you are referring to here are viscosity, conductivity etc and not density.
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Old   March 30, 2012, 05:45
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As Chander says, most people think "variable properties" is viscosity, conductivity, specific heat etc, and not density. Most people consider variable density as simply a compressible flow simulation.

And another point - in future can you use a thread name which describes the thread?
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Old   March 30, 2012, 07:35
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Have you set the "Heat Transfer" under "Fluid Models" to "Thermal Energy"??

If it is "Isothermal", all properties will remain constant.

Best regards
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Old   March 31, 2012, 00:01
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Quote:
Originally Posted by Chander View Post
May be the temperature variation in your simulation is not significant enough to cause any change in results. So even when you use temperature dependent properties, the results are similar.
Also, I am assuming here that the properties you are referring to here are viscosity, conductivity etc and not density.
yes, of course, I mean the viscosity, thermal conductivity and Cp.
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Old   March 31, 2012, 00:05
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Quote:
Originally Posted by lffabiani View Post
Have you set the "Heat Transfer" under "Fluid Models" to "Thermal Energy"??

If it is "Isothermal", all properties will remain constant.

Best regards
thanks for your input, I solve the thermal energy -I did not used the isothermal.
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Old   March 31, 2012, 00:08
Default Deltha T is large enough
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Quote:
Originally Posted by Chander View Post
May be the temperature variation in your simulation is not significant enough to cause any change in results. So even when you use temperature dependent properties, the results are similar.
Also, I am assuming here that the properties you are referring to here are viscosity, conductivity etc and not density.
the min. temp. is 25 C, and the max. temp. is 100 C. so I think that the devaition is large enough.

Thanks again
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