Learning Forum

[Arun Raj]

 I am dealing with a problem regarding Shell and Tube Heat Exchangers. The problem formulation is:

 

   (a) I have a shell and tube heat exchanger where the hot fluid flows through the tubes and cold fluid (air) flows through the shell. 

 

   (b) I want to study if the hot fluid will eventually solidify in the domain. 

 

   My query is:

 

   Can ANSYS FLUENT models: Energy + Turbulence (k-epsilon) + Solidification/melting model can handle this kind of problem? Because once the solidification starts there will be a change in pressure within the domain. 

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   Note: I am aware that there is a lot of work carried out when one of the materials is static (non-flowing) - like a PCM study.

[Rob]

If the solidification is on the cold walls you'll see a build up of solid material. If it's expected to form an emulsion then you need to look at the Eulerian granular model. Simply, the solidification model stops the solid-fluid flowing (it freezes the flow; I like bad puns), so things like floating icecubes can't be modelled with that approach. 

[Arun Raj]

Hello Rob, 

 Thank you for the reply. I got your point. 

 I was hoping to study how a following phase change material begins to solidify when following through the tubes in a shell and tube heat exchanger. 

 There isn't any constant temperature assigned on the tube walls.

  The cold air flowing over the tubes will remove the energy from the flowing PCM, thereby causing it to solidify when the temperature falls below the melting/solidus temperature. In this case, both cold air and PCM are in counterflow. 

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  So if I want to simulate such a scenario, when using the Eulerian model, I cannot use the solidification model or vice-versa. Is there any other work around?

 

  

[Rob]

Not without coding, and I can't go into any details as it's a public forum. However, if the set up is as you say won't the liquid freeze on the tube walls? Maybe talk to your Prof to better understand the physics?