6 Replies Latest reply on Jan 3, 2013 7:36 AM by Cnu Vasu

    How to define wall temp in SW Flow Simln?

    Cnu Vasu

      i have an hollow cylindet of 3mm,where the internal and outer walls are constantly aT 400K AND 300K  respectively and water it flowing throgh this cylinder at 100gr/sec.how can i solve this in flow simulation,my intrest is to see the temparature distribution through the wall.

      please suggest me how can i solve this problem,if possible please suggest me this kind of examples where can i get it?

        • Re: How to define wall temp in SW Flow Simln?
          Delphine Genouvrier

          Hello

          To simulate this, you just need to define an internal water flow with heat into the solids. Define your outer walls temperature at 300K. Use the wizard to define these settings

          Then you define the inlet condition; mass flow rate of 100 gr/s

          Outlet; Pressure at the ambient pressure.

          Apply a temperature on your inner wall = 400 K (see below please)

          1 data is missing in your post is the temperature of the water at the inlet (define when you define the inlet condition)

          Another missing data is the material type of your cylinder.

          You might want to use mesh refinement on your cylinder to get a more accurate prediction of the temperature distribution inside the walls.

           

           

          I have a question for you; you say that the inner wall is constanstly at 400 K so the water flow does not impact the wall temperature...Are you sure about this assumption or is your inner wall at 400 K at the beginning of the simulation?

          I hope this helps

            • Re: How to define wall temp in SW Flow Simln?
              Cnu Vasu

              Thank you Delphine 

              how to define the inner wall temp, do i need to define these in the Real wall condition, isn't it?

              this wall is intially at 400K and the water entering the cylinder at room temperature.

              cylinder material is aluminium

              moreover i cant see the wall  temp boundary condition in the heat sources,surface heat generation rate,volume heat generation and volume temp are available in this section.

              What is the correct command to define this internal wall temp?

                • Re: How to define wall temp in SW Flow Simln?
                  Delphine Genouvrier

                  Hello

                   

                  If you want to apply a fixed temperature on a wall, yes you use the Real wall condition.

                  But I do not think this is what you want to simulate. Indeed, in your case, the inner wall temperature is at 400 K at the first step but does not stay at this temperature as this will change according to the fluid flow.

                  When you do a steady state analysis, you get the results at the equilibrium.

                  In the wizard, define the initial solid temperature at 400 K. Do not define a bounday conditions as this is not a fixed temperature.

                  Define your inlet flow with the ambiant temperature and your mass flow rate.

                   

                  I hope this helps

                    • Re: How to define wall temp in SW Flow Simln?
                      Cnu Vasu

                      Capture.PNG

                      Thank you,

                      yes,the one your predicting is the right,my inner wall is initially at 400K and Outer wall is at 300K.

                      if i mention the solid temp in the project wizard its going to consider the whole pipe is at 400K,isn't it?

                      while fluid flowing through the pipe it has to pick up the temp of this wall and the outer wall shoul be maintained at the room temp 300K.

                        • Re: How to define wall temp in SW Flow Simln?
                          Chris Michalski

                          Cnu -

                           

                          it depends on what you actually control:

                           

                          if the pipe is initially at 400K in a 300K room, in the initial settings set solids to 400K and ambient (air) to 300K.

                           

                          If you do not actively ensure that the outside of the pipe remains 300K, then you should use an external flow so that Flow solves for the convection on the outside of the pipe to the room air. 

                           

                          It sounds like you know: initial tube temperature, ambient air  temperature, inlet water flow rate, inlet water temperature.  The outlet  is likely a pressure opening.

                           

                          The biggest source of error in simulations is usually not in the model itself, but in accurately telling the computer what constraints are known.  The software will almost always give you the right answer - the problem is, the question that you think you asked it to solve is often different from what you actually asked it to solve.

                            • Re: How to define wall temp in SW Flow Simln?
                              Cnu Vasu

                              Thanks alot Chris Michalski..

                              I have tried as per your suggestion but i dont see any change ...

                              as per you intial temp temp of solids to be set to 400K..i.e., all the solids whatever are present in the model will be set to 400K isn't it?

                              but in my case only the the inner wall of the pipe will be at 400K and remaings are at room temp.i.e.300K

                              if we control the outer wall temp in the general settings wall condition ..the heat transfer is just because of condution.i dont observe any loss due to the inlet air flow into the pipe.

                              please refer to the above shown image.