[valentin.geamanu]

Hello.

I have to make a termohydraulic study for a nuclear fuel channel. This channel consist in 12 bundles of 495.3 mm each other that are inside of a pressure tube . At the both ends of the tube i let 1 m more space for flow stabilization.

Usually for this type of nuclear fuel channel,we have an inlet flow rate is 24 kg/s with 266 degrees Celsius and at the outlet we have a pressure of 100 bar.

The 12 bundles produce heat, therefore the water temperature increases until reaches saturation (311 degrees celsius for 100 bar).

I have question even from choice of materials. As i read i have to make a Homogeneous binary mixtures between water liquid and water vapour.

Is it enough to choose, for example water at 100 degrees celsius and water vapour at 100 degrees celsius, and the properties will be automatic calculated for my case or i need to define new materials? If I need to define new materials, must i put properties for both of water liquid and vapour for my saturation temperature?

I read that i have to define water liquid as continuous phase and vapour as dispersed phase. But for the dispersed phase they want me to put mean diameter and i dont know how to define it.

Can you help me with more details about how to manage this model.
I struggled for two months with different settings and i had always different errors like overflow, that one with 0 divide or something like this, a wall has been placed at portions of an outlet, or heat partitioning algorithm failed to fix upper bound of bisection.

I have to finish this study until the end of august so i can to present it as my final dissertation project and to have finally a master degree in nuclear engineering.

Thank you!

[-Maxim-]

First of all: If it's time sensitive: Ask Ansys support. Or in your case: your supervisors and professors. It's their job.

Have you read the FAQ about the overflow problem for example? https://www.cfd-online.com/Wiki/Ansy...do_about_it.3F

If you want our help: Please post pictures (screenshots) of your setups (maybe start with your most promising setup), your ccl/out files including the complete error messages.

[valentin.geamanu]

Hello.

Here is my attempt to solve this problem.
Setup for the mesh: http://imgur.com/a/d5PGK

CFX-Pre:

I used as materials Water Vapor at 100 degrees Celsius and Water at 100 degrees Celsius. I read that the program take care automatically about the properties of water for my case (at 100 bar with 311 degrees celsius - saturation temperature) are calculated automatically. I defined a Homogeneous Binary Mixture and i set as Value 100 bar pressure with a saturation pressure of 311 degrees celsius. http://imgur.com/a/l3u1D

For Mean Diameter of bubble i searched on google and i found somewhere an expression like this: (where 581.15 is the saturation temperature in Kelvin).http://imgur.com/a/cFHsJ ("apa" means water and "vapori" means steam).

The other settings: http://imgur.com/a/gG3nc

Boundary Conditions:

For inlet i set fluid values: 1 for water and 0 for steam: http://imgur.com/a/s6IuX

For the walls: http://imgur.com/a/GcZpL

These are the walls without heat source. So i put heat transfer adiabatic..

Heat source comes from the sheaths of each fuel bundle. Each fuel bundle has one central sheath, first ring has 6 sheaths, the second has 12 and the tird 18. In total 37. So each ring has a specific heat flux.
Here is an example for the first fuel bundle. For the others is similar (only the heat flux value is changed).
At Fluid Values i set for Water - No slip wall and for Steam - Free Slip wall.

http://imgur.com/a/m8t4v

Here are the results:

http://imgur.com/a/rUU4G

The error came at iteration 79: Overflow.

Here is a link with output file: http://docdro.id/koqYjH9

Thank you!