4 Replies Latest reply on Jun 7, 2016 8:45 AM by Petar Arabadzhiev

    Heat transfer and local rotation region

    Petar Arabadzhiev

      Good evening , i currently working on project which involve heat transfer and agitation. I was able to successfully set up a model whit free convection heat transfer from which i can see the temperature distribution in the whole volume of the vessel. Backward i can calculate the overall heat transfer coef. , etc.

      I did try to set up the a model whit a agitator and a local rotation region. I receive a strange results after a coupe of iterations (note the attached images). My question is: is it possible to do this study whit SW flow simulation ? Is there some recommendation of setting up this study?

       

      Basically the model is a cylinder whit heat exchange coil on the outside wall and a agitator made of inclined straight bars. The model run quite well without the heat transfer. But when i add the heat transfer , i get a very low temperature in the region around the agitator. This happens when i set up a inlet volume flow rate at one side of the coil , and a pressure outlet on the other side. When i set up a surface heat source on the inner wall of the coil and disable the heat conduct in solids the result seems quite normal.

      The goal of the study is to obtain the K (w/m2k) values with different type of agitator.

       

      Please excuse my English , it's not my primary language.

        • Re: Heat transfer and local rotation region
          Amit Katz

          Your temperature plot shows a range of 0.5C, it doesn't seem like there is any heat transfer going on. What are you boundary conditions? Is the coil for heating or cooling purposes? Where is the heat coming from and where is it exiting the system?

            • Re: Heat transfer and local rotation region
              Petar Arabadzhiev

              The plot are just to show what is the case. The plot is on the second iteration , it is normal not to show heat going through this small time step. The point is that even in the first iteration the region around the agitator is with low temperature and the other part of the volume is with starting (set up ) temperature (30°C). The study is set up like this : on the one side of the coil i set up a inlet volume flow rate with 4°C , on the other side of the coil is environment pressure outlet. All inner faces of the vessel and the shaft and the bars of agitator i set a initial condition 30°C. I set up two different volume subdomains for the coil and the vessel. For the vessel temp is 30°C , for the coil is 4°C.

              When i exclude the heat conduct in solid and i add the surface heat source on the inner wall of the vessel , the plot is different. The plot show the temperature in whole volume is 30°C.

              I hope i did described the problem enough understandable.

            • Re: Heat transfer and local rotation region
              Petar Arabadzhiev

              Yes i did. In the coil is ethanol , in the vessel is water. On the first question i did leave the calculation going on , but the results don't seems to me to be real. It is impossible to have a 1m3 volume of 30°C and after 10 sec. let say 10% of the volume to be with 10-15°C (the zone around the agitator) . And the zone around the coil to have a temperature like 29.5°C ( this looks more reasonable). I will say it again - When i exclude the heat conduct in solid and i add the surface heat source on the inner wall of the vessel , the whole volume is 30°C and the zone around the coil is begging to drop the temperature. This strange results are appear when the heat conduct in solids is enabled. I need this to be enabled , so the program can calculate some volume goals and the heat flux through the wall between the vessel and the coil.