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How to use Enthalpy function for modelling solidification melts and correct represent solidification in the wide mushy zone for alloys ?
Posted 27.01.2023, 07:17 GMT-5 Fluid & Heat, Computational Fluid Dynamics (CFD), Heat Transfer Version 6.1 3 Replies
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Dear Colleauges, Great thanks for you perfect work ! Comsol is really have all chances be better than Ansys today.
I have a big expirience for modelling casting process in other softaware (like Ansys and Procast) and in this year I started usefull (tested) Comsol. COMSOL I think will be most universal package at nearest time but i have a some troubles for correct modelling alloys with wide solidification range, for example Al-Zn alloy with 7-9% of Zn where is solidification temperature range ~ 70 C. For this case not possible to use Hidden melting heat for jump during 1 degree of Celsius as for pure Aluminum and I need to define precise function for Enthalpy or Capacity for all temperatures for solidification range. Best way for that - use Enthalpy function directly, and which we can define by Function (Interpolation) from txt file obtain by Calcosoft Procast for alloy. But, I not uderstand possible or not to use Enthalpy formulation for heat mass transfer in COMSOL, or only Heat Capacity formulation is available? I tried to import enthalpy curve from txt file as Function(interpolation) with name “Enth” and after that make a new function which is a differentiation of Enth by temperature. In the field Expression of new analytic function I define the d(Enth,T) and argument T in the bottom field. But it does not working, Comsol not understand the name of function “Enth”. Is possible to use d(f,x) for differentiation the functions? Or I must to prepare txt file with Heat Capacity curve by another packages which will give me the differentiation of Enthalpy curve? As well I have additional question Is possible to define temperature interval (by function or another) in the field Phase Change interface – Phase change temperature and Latent Heat in neighbor field?
I hope you very clearly understand that for alloys with wide solidification range should be correct representation for crystallization in the mixed (solid+liquid) mushy zone.
May be would be better to use Multiphase model for Alloy. What is your reccomendation for type of multiphase model?
Best regards and my respect to your titanic works ) Evgeny
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Hi, Evgeny!
Enthalpy formulation for heat mass transfer in COMSOL, or only Heat Capacity formulation is available...
In the Heat Transfer interfaces (Heat Transfer in Solids or Heat Transfer in Fluids) the energy conservation equation is written for temperature, not for enthalpy. If you want to implement energy equation for enthalpy, you can formulate and solve it with PDE interfaces.
Is possible to use d(f,x) for differentiation the functions?
Sure. To demostrate this I've created Interpolation function func1(T) (see Screenshot_1.png) and Analytic function func2(T) = d(func1(T),T) (see Screenshot_2.png). As you can see the diffirentiation operator works.
Is possible to define temperature interval (by function or another) in the field Phase Change interface...
Yes. Also you can define several (up to 5) successive phase transformations with its own temperatures and latent heats. And another option is to define your own Phase transition function that describes how the transition from phase j to phase j+1 occurs. You can read about Phase Change Material feature here: https://doc.comsol.com/6.1/docserver/#!/com.comsol.help.heat/heat_ug_ht_features.09.033.html
If you have any issues with your models please contact Technical Support. You can do it here: https://www.comsol.com/support/case
-------------------Best regards,
Dmitry Lazarev
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A lot of thank Dmitry
1.I have cheked the d(Enth(T),T) on your manner, but can't to recive normal derivative function. Please see the my prinscreens, the results is negative for both cases - when i input the unit dimensions - J, K for Argument and Function fields and without it (similar to your example). Please check, maybe i have a too much points in initial Enthalpy .txt file and remove for this first 5 row.
- Yes I know about Phase transition interfphase, but is not clear for me how I can approximate the thick mashy zone of big slab by steps of Phase interphase. I will prepare the my model for technical support analysis and we can have discussion later. Please see the my paper about my technology which is patented at US, EU,CN and Russia. I want to compare existing results calculated by Ansys and checked by measurings on the existing slabs and new results obtain with Comsol. I hope that COMSOL will be more flexible and better for my futher works.
Best regards, Evgeny
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Hello Dmitry
After upgrading from Win7 to Win10 the operator d(Enth(T),T) stared working. Can i use integrate operator for function Cap (T) = d(Enth(T),T) for cheking and compare with initial function Enth (T) ? Can i define this analytical function in global definition? I tried the function integrate(Cap(T),T) but it is not working at Global Definition and Point Eveluation in Results.
Best regards, Evgeny