Fluids

Fluids

CHT problem between porous media and solid wall

    • ASDzxc
      Subscriber

      Hello there,

      I’m currently trying to simulate a case where a porous media is adjacent to a solid wall using Fluent. The goal is to predict the wall temperature profile. With non-isothermal flow passing through the porous media, there is heat transfer between the porous media and the wall.

       

    • Rob
      Ansys Employee
      Augmentation factor is generally used to mimic rough surfaces where the area is higher than the flat or smooth face modelled. I'm not aware of any studies, but also haven't looked into it:the term is covered in the Fluent documentation.n
    • ASDzxc
      Subscriber
      Thanks for your reply, sir. n(It is strange that very few studies have mentioned this factor.)n
    • Karthik R
      Administrator
      Have a look at section 7.4.15.3.6 - Augmented Heat Transfer. nThanks.nKarthikn
    • ASDzxc
      Subscriber
      Hi Karthik,nI've check the section 7.4.15.3.6. the CAF is written in functionnqid = cid[0] + caf_fac*(cid[1]*C_T(c0,t0) - cid[2]*F_T(f,t)) - cid[3]*pow(F_T(f,t),4)nwhere cid[] is the fluid-side diffusive heat transfer coefficients. nIf I use this CAF, how should I write my boundary condition at interface (fluid/solid interface)? Like this: CAF*Kf_eff*dTf/dn=Kw*dTw/dn ?n
    • Karthik R
      Administrator
      Yes, that is how I would write the condition. But, I have a question for you. If you are solving the flow and heat transfer in the porous media in Fluent, could I ask you what is your purpose for writing this condition between the solid / porous wall?nThanks.nKarthikn
    • ASDzxc
      Subscriber
      Hello Karthik,nActually, it is between porous media and solid wall (not porous wall). nAs you know, to enhance the heat transfer between fluid and pipe wall, you can use rough surfaces where the area is higher than the flat or smooth face (like Rob mentioned). I guess this is reason of CAF exist in Fluent. My tutor would like to see whether porous media will have the same type of enhancement. Is it better to use a rough surface or porous media in order to augmented the heat transfer? That's why I'm asking about the interface condition. n(TBH, I perfer rough surface. Using rough surface seems much easier and straight forward. Otherwise you have to deal with the flow problem, heat transfer problem in porous media, interface condition, blablabla.....)n
    • Rob
      Ansys Employee
      They're different, porous media may mimic a mesh on the surface and augmentation a rough (corrugated) surface. Both will have an effect but best may not just be down to the heat transfer. n
    • ASDzxc
      Subscriber
      Hi RobnYou are right. Now I understand better. Heat transfer is only one aspect of the whole problem.n
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