Learning Forum

[CloudNine]

Hi guys,

I'm extremely new to Ansys and I'm trying to simulate a concentric double pipe heat exchanger.

I'm trying to figure out how to model the heat exchanger:

Should I create two double round pipes (like here: https://www.youtube.com/watch?v=mEvV8jsBOsI) or, as the problem is symmetric, can I stick to modeling the problem to simply flow between walls (cross section of a pipe)? like here:

 

When we solved problems of heat exchanger in heat transfer classes, we used to simplify the structure to flow between walls.

I'm just wondering about the benefits of simulating the "real deal" vs simulating a simplified version. Will the simplification somehow affect the quality of meshing, flow & heat transfer simulation that I will soon start doing? 

Thanks!

[peteroznewman]

 Hi CN,

I recommend starting with the simplest model that will give you some useful information. Maybe you will have to build a more elaborate model to get more detailed information, but even the model in the video was a simplification. They didn't show how the fluid flowed into the outer pipe. It had to come in from the side at some point, right?

Start with a 2D model, but not a slice through the whole pipe top to bottom, but a radial slice from the center axis up to the outer pipe. That will be an Axisymmetric model and much more accurate than the slice you show above because the equations actually account for the rotation about the axis to calculate accurate surface areas for heat transfer.  You have to draw the domains with the pipe axis on the X axis and only draw the radial slice in the positive Y coordinates.

Before you start the Geometry editor (DesignModeler or SpaceClaim), while you are in Workbench, RMB on the Geometry cell in the Fluent system to get Properties and on the Analysis Type change from 3D to 2D before you start creating Geometry and bring it into Meshing. You can't go back and do that after you have opened Meshing. You have to start over.

Regards,
Peter