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Old   June 2, 2009, 22:27
Default multiphase multicomponent physics
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George
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I have a Eulerian-Eulerian multiphase multicomponent physics model setup (plasma furnace) which consists of three fluids and dispersed solids (particulates). two of the fluids are molten material in which the phase change from liquid to solid is defined by ccl. the third fluid is a variable gas composition with reactions. buoyancy is activated. to imagine the problem think of the furnace as a cylinder with two ducts in parallel that are tangential to the cylinder sides. the molten stuff is at the bottom of the furnace and the gas with the dispersed solid enters the furnace from one duct and leaves the via the other duct.

I was just wondering if there is a way in CFX (11sp1) to plot the bulk temperature in the domain in a multiphase setup? (At the moment I'm calculating an average temperature by ccl expressions with a simple energy balance relation)

there are other variables that I'm interested for example a bulk wall heat flux variable for the whole domain for plotting however only the variables for each fluids are available - for example gas.wall heat flux as you'd expect in multiphase apart of the pressure and density variables.

so, is there an easy way to force the solver to output these "bulk" variables for multiphase if its possible? I believe that at least a bulk temperature should be calculated once you define an energy model. could I do the above for example by editing the variables file?

failing that, any ideas for calculating a bulk wall heat flux for the domain? I was thinking to simply add the heat fluxes of each fluids multiplying each one with its volume fractions but ideally I wanted to ask if there is any more direct/different approach

for example for heat loss
qlosstot=qloss1+qloss2+qloss3+qloss4
qlosstot = areaInt(gas.Wall Heat Flux)@furnace lower sides * gas.vf + ....

any comments/suggestions would be appreciated?

Last edited by ckleanth; June 4, 2009 at 04:53.
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Old   June 4, 2009, 04:54
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Anyone .... ?
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Old   June 4, 2009, 18:57
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Hi,

I don't see what you are asking. If you want to total wall heat flux then just sum up the fluxes per phase as you suggest. If you want a bulk averaged temperature then do a mass averaged temperature as you suggest. These can be easily generated in CEL and sent to monitor points or CFD-Post.

So what are you actually asking? (Sorry in advance if I have misread your question)

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Old   June 4, 2009, 20:15
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Hi Glenn. basicaly I was just asking if thre is a particular reason why in multiphase we need to write the equations for the bulk variables and why this is not done automaticaly in cfx once we chose the physics that we want to model.

I was kinda curious whenether these bulk values are calculated within the solver. I think at least the bulk temperature is calculated because I searched the variables file and it contains the following scalars T, averaged temperature and Ttot and the flag is enabled to for them to be as output to postprocessor - however they are not there. thus I was also wondering if I am right and if so how to enable these variables.

as for my next question I just wanted confirmation of what I was calculating made sence and if anyone has a better way of doing this. i'm having some problems in plotting a nice and uniform heat loss and heat flux plot on the surface of the furnace.

qflux679 = (gas.Heat Flux * gas.vf + Slag VM.Heat Flux * Slag VM.vf +Copper VM.Heat Flux * Copper VM.vf)

qloss679 = (areaInt(gas.Heat Flux)@anode * gas.vf +areaInt(Slag VM.Heat Flux)@anode * Slag VM.vf + areaInt(Copper VM.Heat Flux)@anode * Copper VM.vf + the same for all my external surfaces
I'm ploting this functions at the external surface of interest

the calculation for average Temperature and wall temperatures is fine. the heat flux in the gas space is somewhat similar to experimental data but I dont believe the heat flux at the bottom part of the furnace with the molten metals. I realise this might be because of the volume fractions in the equation and I have doubts for the heat loss equation. I think there is something wrong in my calculations but I'm unsure and I wanted to ask someone with a bit more experience for sugestions.

George


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