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-   -   Variable physical properties of fluids/solids (http://www.cfd-online.com/Forums/fluent/31453-variable-physical-properties-fluids-solids.html)

rosco May 11, 2003 08:23

Variable physical properties of fluids/solids
 
Hi, is Fluent include all the change of physical properties in materials? For example density, Cp, viscosity change with temperature. I don't want Constant physical values for a fluid but all of them.

I have to enter manually the polynomial equation (piecewise linear or polynomial) to relate these facts or is it already included?? Thx a lot.

ap May 11, 2003 11:35

Re: Variable physical properties of fluids/solids
 
You have to manually insert polynoms coefficients in the Materials dialog box.

ap

rosco May 11, 2003 11:46

Re: Variable physical properties of fluids/solids
 
Oki thx ap :) They should be put these data in fluent directly, it's a loss of time for us.

ap May 11, 2003 15:37

Re: Variable physical properties of fluids/solids
 
Polyomial expressions are not valid in all ranges of their parameters, so a complete database should contain different expressions for the same datum in different ranges. And for a single datum, the solver should decide which expression is valid.

I think it's better to leave the user decide which expression is better to use, even if this is time consuming :)

However, you can find a complete database integrated in Aspen.

Hi

ap

rosco May 11, 2003 15:56

Re: Variable physical properties of fluids/solids
 
My temperature range is quite small [20C to 50-60C] and only for water. I must verify but I think I have all values for density, Cp, k at each temperature so it's not a problem. I'll do probably a piecewise-polynomial because more easy than calculate the polynomial regression.. And I'll save it in propdb.scm to avoid re-type it again and again :D

I don't know what is ASPEN , I'll do a search on Google :)

Thx

rosco May 11, 2003 16:06

Re: Variable physical properties of fluids/solids
 
piecewise-linear I want to say not polynomial :)

ap May 11, 2003 16:10

Re: Variable physical properties of fluids/solids
 
If you don't want to calculate expressions by yourself, try to look for them in the Perry's Chemical Engineers' Handbook (McGraw Hill).

Hi

ap


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