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February 3, 2010, 12:27 |
heat flux/phase change
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#1 |
New Member
Frank
Join Date: Feb 2010
Posts: 2
Rep Power: 0 |
hi friends,
i'm a student from spain, and i have this following problem: i have water-bearing pipe (100m) which gets an external heat flux (50000W*m-2), so after some meters the water inside the pipe is going to vaporize i dont know much neither about cfd nor about star-ccm+, so i tried solving using the user-guide and came to this solution: the models i use are - three dim. - stationary - steady - liquid - segregated flow - segregated fluid temp. - constant density - turbulent - reynolds-averaged navier-stokes - k-e-turbulence - realizable k-e two-layer - two-layer all y+ wall treatment - boiling the result i get is in the attachment so my questions are: - why is all the line linear? - why the line does not change after boiling (373K)? - or is there a general problem with my models? - and if so, could anybody help me? :-) thank you in advance saludos, frank |
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February 4, 2010, 02:12 |
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#2 |
Member
Kuan Tek Seang
Join Date: Mar 2009
Posts: 31
Rep Power: 17 |
you need to model/define two phases. otherwise, in a single phase, this is what you would expect to get. There is nothing to define phase change from water to vapor etc.
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February 4, 2010, 03:13 |
heatflux
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#3 |
Member
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you should specify multiphase mixture option instead of liquid option in starCCM+
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February 12, 2010, 09:46 |
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#4 |
New Member
Frank
Join Date: Feb 2010
Posts: 2
Rep Power: 0 |
First of all, thank you for your answers...so i´ve been reading the user guide again and there really is a capital about boiling and multiphase, so the new models i chose (due to the user guide) are:
- three dimensional - stationary - multiphase mixture - eulerian multiphase - water (liquid,h2O,constant density) - vapor (gas, h20, constant density) - volume of fluid - segregated flow - multiphase equation of state - implicit unsteady - turbulent - reynolds-averaged navier-stokes - k-e turbulence - realizable k-e two-layer - two-layer all y+ wall treatment - segregated multi-phase temperature - gravity - surface tension - boiling Gravity and surface tension i had to choose, because without them boiling was not available..so far so good, but now i have temperatures up to 5000 K... almost all of the properties are by default, only thing i changed is the volume fraction in the inlet to [1.0,0.0], to have only water in the inlet... i know it is hard to understand without seeing it, but anybody has an idea for me? by the way, there is a nod called "HTCxArea" within boiling under the models, it has by default a value of 5000000 W/m^3*K...it seems to me pretty high, does anybody know what this means? thanks in advance |
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