Learning Forum

[JonathanV]

Hello Everyone
I am new to Ansys and I must perform a simulation of a tube solar, when developing my project I reached the
setup section where I wanted to initialize my project and I had some warnings that affect my simulation,
my project consists of a solar tube that is composed in the outside of glass, inside this section there must
be a vacuum (which for the moment put air since I don't know how to place the vacuum section), inside this
section there is a copper pipe with the inside filled with water (you can observe in a better way in the
graphs), the objective is to observe the thermosiphon effect in the water inside the copper pipe.
Therefore I have some questions that I would greatly appreciate if you could help me and they are:
How can I solve these warnings?, since when simulating the sun's rays they do not heat my internal copper pipe
and therefore it does not heat my internal fluid( in my case water).
How to put vacuum instead of air in my middle section?
Attached images and simulation.
Thanks in advance for the help.

[Kishan Konannavar]

Hello
Could you please attach the necessary images in the post as Ansys employees are not allowed to download any file.
Thank you

Regards
Kishan

[Kishan Konannavar]

Hello
Meanwhile you could refer the following posts to get an idea about vacuum creation
Could anyone check if my radiation setup is correct? ÔÇö Ansys Learning Forum
Slip Boundary Formulation for Low-Pressure System ÔÇö Ansys Learning Forum

Regards
Kishan

[JonathanV]

Thanks for your answer Kishan I attach the images with the explanation:
I need to simulate the thermosiphon effect inside a vacuum solar tube similar to the one that can be seen in this figure:
The interior is water (where the thermosyphon effect should be observed) and as can be seen it is enclosed within the copper heatpipe, part of this copper heatpipe is enclosed by glass and between these two sections we have a vacuum, and it is in this section covered by glass where we have solar incidence, the sun's rays pass through the glass and heat the copper inside the glass, they are also reflected in the glass and returns some of its energy to the copper. As only a certain part of the copper is heated, this heats the water inside the copper heatpipe, producing the thermosiphon effect.
To develop the project, I create one of type Fluid Flow (Fluent), the geometry is seen in the figure:
Where I generated two volumes of fluid type, the first for the copper heatpipe and the water, the second for the glass and the vacuum.
Then generate a mesh as can be seen in the images of my previous post, labeling as copper the external face of the Fluid cylinder and the internal face of Fluid2, which is where there is contact between the fluids.
I set up the simulation as follows:
The same of wall-13 for wall-14, and when initialize appear these warnings and when simulating I only get a floating point error

[JonathanV]

Should I also use laminar flow and not turbulent flow for this application?

[sanasaid022]

I am working of evacuated tube solar collector, and most of the articles reaserchers work with laminar flow