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-   -   Honestly: Can drying be modelled with Phoenics? (http://www.cfd-online.com/Forums/phoenics/51937-honestly-can-drying-modelled-phoenics.html)

Alumna August 14, 2005 16:30

Honestly: Can drying be modelled with Phoenics?
 
I was resigned that in version 3.3. of Phonics modelling the drying of stuffs is impossible, but now I have the 3.5 version at my disposal, 3 weeks utill my thesis deadline, and a huge stress that I might do it, but I'm not sure of it!

SO! Let me ask you, folks: IS IT POSSIBLE?? Is it worth to loose all my time of writing the thesis to find the apropriate coding? I have some equations, but I really don't see how to implement them in Phoenics via Plant, Ground, In-Form, whatever!

The problem is this: I have a cube with an inlet and an outlet on 2 opposite faces. Inside i have a plate - the product to be dried. The air suppplied by the inlet is at 60 deg. Celsius. The product is heaten by the hot air stream, and then the drying occurs. That means HEAT & MASS transfer, in the same time [evaporative cooling].

I guess i have to define the product as a sink, a patch which has the CO=f(x direction velocity), a function that i have to put it somewhere [WHERE??] and VAL=high face of the product, which varies during the heating process. It needs something like a LOOP, to go look at the previous value...

If I do it till here, I would solve the heat transfer phenomenon! Which would be great!

I could only dare to dream to do the rest - the mass transfer, COUPLED with the heat trasfer! Because the hot stream of air, giving heat to the product, takes the water vapours. It has something to do with the partial pressures... How could I model this too?

DRYING! the most common phenomenon on Earth is soooo... difficult to model!?

mick August 16, 2005 12:18

Re: Honestly: Can drying be modelled with Phoenics
 
>>I was resigned that in version 3.3. of Phonics >>modelling the drying of stuffs is impossible, but >>now I have the 3.5 version at my disposal, 3 weeks >>utill my thesis deadline, and a huge stress that I >>might do it, but I'm not sure of it!

Its definitely not a standard model in PHOENICS, although I believe that it has been done before... but its not for beginners its very tricky done properly, (and I'm not sure exactly how without some thinking/research)

I was hoping that I could find a paper in the PHOENICS journal that was doing something similar and which would have the Q1 and ground coding...but I cant.

I will look further and report back, but I think 3 weeks is cutting it a bit fine from scratch.

Alumna August 16, 2005 16:09

Re: Honestly: Can drying be modelled with Phoenics
 
I've been working at this project for 2 years [more or less]. Most of the time with 3.3 version of PHOENICS. I read everything in the encyclopedia, tutorials, different library cases. I've seen many things CLOSE of what I needed, but not EXACTLY the thing i needed. I often had the feeling that only a small change somewhere would make the case to be just like the one i need, but I never understood which one.

I was hoping that 3.5 had fewer limitations, and that my case would be solvable.

I'm fully aware this is not easy work - it's quite complex [anyway - I don't look like a Nobel Prize winner! :) ], but I really want to finish my diploma thesis as soon as possible!

Thank you very much for your answer, and for the promise you would do some searching. Only this already made me feel more comfortable... :)

mick August 16, 2005 19:13

Re: Honestly: Can drying be modelled with Phoenics
 
Hi, (This isn't my final answer), and I cant promise a quick solution but I can try and help.

I am not sure this has anything to do with the versions or limitations of the versions. And no, I guess reading the encylopedia will not help you massively here.

What PHOENICS can provide is a means to solving a general equation(s) that we can manipulate into various shapes or forms. So it can provide the solvers for us.

I think in the mean time you could email me your equations and a more detailed description of whats going on, and any simplifications that we might make. For example can we assume that the water in this porous medium is everlasting and hence maybe grasp for a steady-state solution......obviously not true but an assumption that may make life easier..... maybe we can work something more easily in 1D.

Are there any simplifications we can get away with at least as a step towards a final solution?

I guess a diagram and equation list would be great, (with nonclemature).

I think that one of the problems may be that one might need to resolve the temperature on the boundary of the porous medium. This might come from a complex heat balance and may involve coding a newton-raphson or something to resolve Temp on the edge, as this may come from a non-linear heat balance expression for Temp

If you have been studying this for two years then fill in some of the gaps for me with a email, you no doubt know more about this process then me, perhaps the way to go is for me to guide you on how to implement what you know. Perhaps you could mention some of the library cases that are close to what you want, but not quite close enough and why.

I am on a promise to a paper tomorrow that might shed some light as to a solution approach.

But this is definitely not a turnkey type problem.

P.S. Why wait for the final countdown before posting, also have you anyone in your Dept who is an experienced PHOENICS user who may help translate any input/coding that might be suggested.


mick August 16, 2005 19:26

Re: Honestly: Can drying be modelled with Phoenics
 
do you have a recompilable version and if so if this 3.5.1 ?

Peter August 17, 2005 10:16

Re: Honestly: Can drying be modelled with Phoenics
 
Send in your Q1 file to me at CHAM and I will see what can be done to assist- email:pls@cham.co.uk

mick August 21, 2005 04:23

Re: An interim solution - simplifiction
 
Hi, I had a read through the paper that I mentioned previously and as suspected there is a heat balance applied at the surface boundary.

However I think that if an evaporation rate (or rate curve w.r.t temp) were assumed then it could be possible to knock up a model quite swiftly. As an interim step this simplification would not need the 'surface heat balance' and hence everything could be done through the Q1 input file.

A concentration equation would need to be solved for vapour mass (or vol) fraction and the resultant properties calculated through mixture mass fractions. But all of this can be activated through the menu.

Would this type of simplification be of any use?


mal@secomak.com September 26, 2005 11:23

Re: Honestly: Can drying be modelled with Phoenics
 
Have a look here Can Drying

Alumna September 26, 2005 12:03

Re: Honestly: Can drying be modelled with Phoenics
 
This Wednesday I have my final presentation. Wish me luck! :)


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