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-   -   what is wrong with this Evaporation modeling? (http://www.cfd-online.com/Forums/fluent-multiphase/133032-what-wrong-evaporation-modeling.html)

karimnejad April 9, 2014 08:46

what is wrong with this Evaporation modeling?
 
Hello.

I have faced a problem which I'm not sure wether the way I'm trying to model it is right or not.
I should say, as it is part of something bigger and I have not enough information about what really happens the modeling just got complicated.

here is an image of geometry.
http://www.4shared.com/photo/7zkJOINJce/Untitled.html
as the hot gas comes form gas inlet in 700 K and 2.13 MPa, water comes from water inlets in 300 k and pressure of 35 Mpa.

the experiments shows that in there should be an acceptable evaporation. but my modelling does not.

this is my modeling:
--------------------------------------------------------
pressure based-steady

multiphase model : mixture-3 phase
viscous model : k-epsilon Realizable
energy eq : On

materials: air,water liquid,water vapor
air: ideal gas
water liquid and vapor: default

primery phase: air
secondary phase: second=water liquid , third=water vapor
interaction: mass-> Mechanisem:evaporation-condensation-> saturation temperature= piecewise-linear- 2 point

B.C

gas inlet: pressure inlet
water inlet: pressure inlet
outlet: pressure outlet

presure-velocity coupling: SIMPLE
under relaxation factors are grater than 0.1 and smaller than 0.2
spatial discritizations are all first order.
-------------------------------------------------
I should say I have changed under relaxation factors or spatial discretization methods and also pressure velocity coupling methods but nothing have changed significantly.

I doubt more about my 1-multiphase model 2-steady 3-the phenomena which water comes out. because I don't know when the water comes out it sprayed or not. the liquid water phase in results is a simple continuous trace.but it should not be like this I think...
I don't know really. can anybody help me?

anything comes to your mind will be appreciated.
thanks. Ali


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