TSS desalination Model

HadiBadger · March 29, 2015, 13:58

Hi all,

I have a Tubular Solar Still (TSS) desalination model which needs to be simulated in ANSYS cfx.
In the beginning I imported the evaporation_drop CCL file and assigned the Glass cover as a Vapor domain and the Steel tray as water domain.
The Vapor domain contains the Mixture (Air ideal gas + H2O) as continuous fluid, the Water domain contains H2Ol as Particle Transport Fluid.
The Thermal Radiation is activated in the Fluid Models tab and the Heat Transfer is set to Fluid Dependent.

Do I have to create subdomain?
Does my model need a Domain Interface between both phases? and which walls should be assigned if yes?
Do I have to write a continuity equation for the Gas phase?
Do I have to write an energy equation for the water phase?

cheers
Hadi

ghorrocks · March 30, 2015, 18:38

You need a subdomain if there is a sub-region you want to apply something to.

You need a domain interface if you want to couple two domains together. And if you have multiple domains then you will want to couple them somehow. But I cannot see why this would be multiple domains. Why do you think this is a multiple domain simulation?

You don't need to write continuity or energy equations for anything, it is built into CFX. You activate the appropriate models and CFX sets up the equations required to model it.

HadiBadger · April 2, 2015, 00:16

I really don't think it's multiple domain, I was just wondering if it's necessary in my model or not (am somehow new with CFX ).

I have a very silly problem which is: How can I apply a temperature range to a surface (bottom) for example: I want to start with 40C and reach 60C with 2C step? is it an expression problem? or I can apply it with some CFX features?

HadiBadger · April 3, 2015, 14:17

I tired to make an Interface between the two Domains (Water & Gas) but Run stops with this message:

2 isolated fluid regions were found in the following set of
coupled domains:

Vapor Domain
Water Domain

If the isolated regions do not have the pressure level set either
by the boundary conditions or using a reference pressure equation,
you may encounter severe robustness problems.

This situation may have arisen because a domain interface was not
properly defined during problem setup. Please carefully check
the setup.

The solver will stop now and write a results file. The isolated
regions can be visualised in CFX Post by making plots of the
variable "Isolated Volumes".

If you are sure that the pressure level is set in each isolated
fluid region then you can force the solver to turn off this check
by setting the expert parameter "check isolated regions = f".

ghorrocks · April 6, 2015, 20:32

Hang on - before you implement models without any idea of what is going on, let's understand what is happening and select the appropriate models for what you are trying to do.

Let's answer some basic questions:
What are you trying to do? Why are you doing this model? What do you hope to learn?

What are the important physics? What moves and what is stationary? What is adiabatic and what has important heat transfer?

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March 30, 2015, 18:38		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,872 Rep Power: 144	You need a subdomain if there is a sub-region you want to apply something to. You need a domain interface if you want to couple two domains together. And if you have multiple domains then you will want to couple them somehow. But I cannot see why this would be multiple domains. Why do you think this is a multiple domain simulation? You don't need to write continuity or energy equations for anything, it is built into CFX. You activate the appropriate models and CFX sets up the equations required to model it.

April 2, 2015, 00:16		#3
HadiBadger New Member Abdelhady Join Date: Mar 2015 Location: Germany, Kiel Posts: 5 Rep Power: 11	I really don't think it's multiple domain, I was just wondering if it's necessary in my model or not (am somehow new with CFX ). I have a very silly problem which is: How can I apply a temperature range to a surface (bottom) for example: I want to start with 40C and reach 60C with 2C step? is it an expression problem? or I can apply it with some CFX features?

April 3, 2015, 14:17		#4
HadiBadger New Member Abdelhady Join Date: Mar 2015 Location: Germany, Kiel Posts: 5 Rep Power: 11	I tired to make an Interface between the two Domains (Water & Gas) but Run stops with this message: 2 isolated fluid regions were found in the following set of coupled domains: Vapor Domain Water Domain If the isolated regions do not have the pressure level set either by the boundary conditions or using a reference pressure equation, you may encounter severe robustness problems. This situation may have arisen because a domain interface was not properly defined during problem setup. Please carefully check the setup. The solver will stop now and write a results file. The isolated regions can be visualised in CFX Post by making plots of the variable "Isolated Volumes". If you are sure that the pressure level is set in each isolated fluid region then you can force the solver to turn off this check by setting the expert parameter "check isolated regions = f".

April 6, 2015, 20:32		#5
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,872 Rep Power: 144	Hang on - before you implement models without any idea of what is going on, let's understand what is happening and select the appropriate models for what you are trying to do. Let's answer some basic questions: What are you trying to do? Why are you doing this model? What do you hope to learn? What are the important physics? What moves and what is stationary? What is adiabatic and what has important heat transfer?