Dear Kiran Saikia . This question has been widely investigated in scientific literature over the last 1-2 decades. You will find a number of publications from a joint collaboration of HZDR (Helmholtz Center Dresden-Rossendorf) and ANSYS Germany on validation of Eulerian multiphase flow models for adiabatic MPF flows and in combination with wall-boiling models. You may want to search for the following authors and read there many publications on this topic: Eckhard Krepper , Thomas Höhne , Thomas Frank , @ Yury Egorov, @Conxita Lifante.

Or you may want to refer to this literature page:

http://www.drthfrank.de/literatur.html

As a result of all this research, over the years there has been established a thoroughly validated set of closure models for Eulerian multiphase flow predictions with RPI wall boiling model and its extensions. But you need to be aware, that once a model is named equally like a validated model in the literature, it not necessarily means, that this model has been thoroughly validated in all possible model combinations in ANSYS Fluent as well. It would be still a part of your own scientific work to run a reasonable amount of validation investigations with your finally selected set of models in comparison to a trusted set of experimental data.

Regards,

Dr. Th. Frank.

Thank you Dr Thomas Frank for your response. I have been trying to find the best possible model combination for my set-up.

Hi,

for wall boiling in vertical annulus one well suited set of interphase force closure models from my perspective could be:

* Grace drag (Ishii-Zuber almost equally suited)

* Favre Averaged drag (FAD) turbulent dispersion force model

* Tomiyama lift force

* Tomiyama wall lubrication force (or the formulation from my work, Frank model, which is close to Tomiyama's formulation, but being generalized and made independent from a pipe or hydraulic diameter)

It is a bit still a matter of debate, whether a wall lubrication force model should be used in case of wall boiling - in my own honest opinion, it should NOT be used, since the vapor in the situation of wall boiling is formed directly at the superheated wall. So it makes from my perspective no physical sense to use a wall lubrication force model, which is a model being developed with the intention to reproduce in an Eulerian MPF simulation the gas bubble-free gap close to the wall, which is usually present in an adiabatic MPF flow in vertical pipe or channel geometries. This is not the case in flows with strong wall boiling.

If ANSYS CFX is used for the simulation, than all relevant changes of thermodynamical parameters of the fluid and vapor is best taken into account by using IAPWS-IF97 material properties for water and steam or by using corresponding RGP tables, if the working fluid is something different than water/steam, e.g. if (wall) boiling of a refrigerant is studied.

Regards,

Dr. Th. Frank.