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dinesh July 4, 2013 09:25

Stefan Problem
 
Hi Everyone
I am working on the project of heat transfer through phase change materials(PCMs). Earlier i was using fluent. can any body suggest which software is capable of giving good result. Although Fluent has solidification and melting solver but that i thk is not applicable for my case where the PCM(stored in a closed container) and Heat transfer fluid flows around it. Recently i came across meltFOAM. Though i am comfortanle in fluent but if any new CFD software can do it i will learn. Suggest me....

flotus1 July 5, 2013 03:39

Why do you think Fluent cant handle the problem? From you description, I dont see any reason.

dinesh July 6, 2013 01:53

Re:Stefan Problem
 
I was going through international papers but i could nt find any analysis done using fluent. Some says meltFOAM can do while some has done it on COMSOL. Would you suggest me which solver can do it in fluent? i would also appreciate if you could send me the link of some tutorial based on my problem.
Description of my problem: A hot fluid is coming and it passes over the container containing PCM(spherical/cylindrical shell having some thrmal conductivity). Now i want to know the amount or the fraction of phase change that has occured over a given period of time. and how much time it will take to completetly melttt the PCM. Also i want to see the reverse case i.e freezing of the melted PCM.

thanks

dinesh July 8, 2013 04:10

I was going through international papers but i could nt find any analysis done using fluent. Some says meltFOAM can do while some has done it on COMSOL. Would you suggest me which solver can do it in fluent? i would also appreciate if you could send me the link of some tutorial based on my problem.
Description of my problem: A hot fluid is coming and it passes over the container containing PCM(spherical/cylindrical shell having some thrmal conductivity). Now i want to know the amount or the fraction of phase change that has occured over a given period of time. and how much time it will take to completetly melttt the PCM. Also i want to see the reverse case i.e freezing of the melted PCM.

thanks

flotus1 July 9, 2013 02:31

I dont have access to any tutorials other than those in the fluent manual. But your setup doesnt seem too complicated. An external flow is heating a container in which the phase-change material is melting.
Tutorials "4: Modeling Periodic Flow and Heat Transfer" and 24 "Modeling Solidification" should cover most of the features involved in this simulation.

dinesh July 11, 2013 08:36

Quote:

Originally Posted by flotus1 (Post 438591)
I dont have access to any tutorials other than those in the fluent manual. But your setup doesnt seem too complicated. An external flow is heating a container in which the phase-change material is melting.
Tutorials "4: Modeling Periodic Flow and Heat Transfer" and 24 "Modeling Solidification" should cover most of the features involved in this simulation.


sir
do i need to activate species transport and multiphase. as i am interested in knowing the volume fraction of the melted PCM

flotus1 July 11, 2013 11:21

No to both of them.
If the PCM is sealed in the container, this is not a multiphase simulation.
The "liquid fraction" is one of the results generated when using the solidification and melting model in fluent.

dinesh July 11, 2013 12:10

Quote:

Originally Posted by flotus1 (Post 439207)
No to both of them.
If the PCM is sealed in the container, this is not a multiphase simulation.
The "liquid fraction" is one of the results generated when using the solidification and melting model in fluent.


thanks a lot for your valuable guidance, i will now work out on solidification model.

dinesh August 30, 2013 04:56

model for enthalpy porosity formulation
 
Quote:

Originally Posted by flotus1 (Post 439207)
No to both of them.
If the PCM is sealed in the container, this is not a multiphase simulation.
The "liquid fraction" is one of the results generated when using the solidification and melting model in fluent.


As per our discussion there is no need for both ie species transport and multiphase to activate for my problem
As per this paper "H. Shmueli et al. / International Journal of Heat and Mass Transfer 53 (2010) 40824091" page number 4089 right column says
"As for the pressure discretization, only PRESTO! and Body-Force-Weighted schemes are available for the VOF and mixture multiphase models." So I am totally confused about the model to be used in my case. Paper also keeps courant number to 0.5 which is available under Multiphase model.
Plz guide me
thanks

flotus1 August 30, 2013 09:17

Again: if the surrounding fluid and the PCM remain separated by the container, there is no need for a multiphase simulation.

dinesh September 4, 2013 13:16

Quote:

Originally Posted by flotus1 (Post 448913)
Again: if the surrounding fluid and the PCM remain separated by the container, there is no need for a multiphase simulation.

Sir i got struct at a point
I am doing this analysis with PISO/Body force weighted/2nd order. After running this simulation for some time say about 40s of result depending upon time step, it diverges. I am using the gravity field also and slowly increasing the value of g during the initial iterations(as suggested by some user). What are the things i should look at so that my solution does not diverges

flotus1 September 5, 2013 05:00

I have no idea how gravity affects the simulation you described so far.
You should first decide which physical effects you want to simulate and then start a simulation.

dinesh September 11, 2013 14:59

Quote:

Originally Posted by flotus1 (Post 450017)
I have no idea how gravity affects the simulation you described so far.
You should first decide which physical effects you want to simulate and then start a simulation.

Sir
i want to know about the additional source terms( like in momentum equation and energy equation) which needs to be added to normal cont., mom, energy eqns when we are modelling solidification." Ref paper By V R Voller and C prakash IJHT vol 30 No 8 pp 1709-1719, 1987". How these additional source terms are handled in fluent. As far i know Fluent has the option of adding these additional source terms through cell Zone conditions/zone name(in my case it is PCM)/edit/source terms/ which contains the tab to enter different source terms in mass, x mom y mom z mom energy, tur, etc and the number of source terms. So should i "check" these source terms box and if yes what values I have to give since these source terms have variables and PDE.
plz comment i hope i made it clear.


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