{"id":345402,"date":"2024-01-18T15:14:50","date_gmt":"2024-01-18T15:14:50","guid":{"rendered":"\/forum\/forums\/topic\/joule-thomson-effect\/"},"modified":"2024-01-18T15:14:50","modified_gmt":"2024-01-18T15:14:50","slug":"joule-thomson-effect","status":"closed","type":"topic","link":"https:\/\/innovationspace.ansys.com\/forum\/forums\/topic\/joule-thomson-effect\/","title":{"rendered":"Joule-Thomson effect"},"content":{"rendered":"

Hi,<\/span><\/p>\n

 <\/span><\/p>\n

I’m currently working on simulating the joule-thomson effect for cryo cooling with real gas CO2. Unfortunately my simulations don’t converge. Here’s a short overview of my setup:<\/span><\/p>\n

 <\/span><\/p>\n

 <\/span><\/p>\n

    \n
  1. Geometry
    My geometry has a very small diameter compared to its length. Fist there is a long upstream pipe, then the gas is throttled through a small orifice into a bigger expansion part followed by a downstream pipe. <\/span>Here’s a sketch:
     <\/span><\/li>\n<\/ol>\n

     <\/span><\/p>\n

      \n
    1. Mesh
      I used the Watertight Geometry Workflow and a poyhedra mesh for the Mesh generating. <\/span>My Mesh Quality is:<\/span><\/li>\n<\/ol>\n\n\n\n\n
      \n

      Mesh Size<\/span><\/p>\n<\/td>\n

      		\n

      786574 Cells, 3878491 Faces, 2542058 Nodes<\/span><\/p>\n<\/td>\n<\/tr>\n

      \n

      Cell Quality<\/span><\/p>\n<\/td>\n

      		\n\n\n\n\n\n\n
      \n

      Orthogonal<\/span><\/p>\n<\/td>\n

      		\n

      Minimum = 0.2, Average = 0.97<\/span><\/p>\n<\/td>\n<\/tr>\n

      \n

      Skewness<\/span><\/p>\n<\/td>\n

      		\n

      Maximum = 0.8, Average = 0.023<\/span><\/p>\n<\/td>\n<\/tr>\n

      \n

      Aspect Ratio<\/span><\/p>\n<\/td>\n

      		\n

      Maximum = 13.6, Average = 4.2<\/span><\/p>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/td>\n<\/tr>\n

      \n

      Surface Quality<\/span><\/p>\n<\/td>\n

      		\n

      Skewness: Maximum = 0.56, Average 0.002<\/span><\/p>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

        According to the recommendations the mesh quality should be okay.<\/ol>\n
          \n
        1. Physics Setup<\/span><\/li>\n<\/ol>\n\n\n\n\n\n\n\n
          \n

          Inlet<\/span><\/p>\n<\/td>\n

          		\n

          Pressure-inlet with 3.5 MPa, 293.15K<\/span><\/p>\n<\/td>\n<\/tr>\n

          \n

          Outlet<\/span><\/p>\n<\/td>\n

          		\n

          Pressure-outlet with 0.6 MPa<\/span><\/p>\n<\/td>\n<\/tr>\n

          \n

          Walls<\/span><\/p>\n<\/td>\n

          		\n

          Thickness of 0.0001m, no heat flux<\/span><\/p>\n<\/td>\n<\/tr>\n

          \n

          Material<\/span><\/p>\n<\/td>\n

          		\n

          C02, real-gas-nist model<\/span><\/p>\n<\/td>\n<\/tr>\n

          \n

          Model<\/span><\/p>\n<\/td>\n

          		\n

          SST k-omega (2equn), with viscous heating<\/span><\/p>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

          I limited the temperature to 216.65K so that the gas doesn’t desublimate or respectively because the real-gas data from the NIST databank for CO2 is only defined in the temperature range from 216.592 K on.<\/span><\/p>\n

           <\/span><\/p>\n

            \n
          1. Solver
            I’ve tried different solver settings (pressure-based, density-based, solution-steering) for steady-state. I also tried to reduce the under-relaxation factors and the courant number. I tried hybrid initialization or hybrid +FMG initialization. Especially the energy residual remains constant and doesn’t decrease at all. I also tried to start without energy, then enabling energy with first order discretization and moving on to second order. <\/span>But the simulations never converged. My longest simulation was 2000 Iterations. <\/span>I often get the warning that the temperature limit is reached at some cells (mostly between 5 and 200 cells).<\/li>\n<\/ol>\n

             <\/span><\/p>\n

            Does someone dealt with the Joule-Thomson effect before or know good settings to reach convergence for a compressible real gas problem? Or am I doing something wrong? Should I simplify my geometry? I would be grateful for any help!<\/span><\/p>\n

             <\/span><\/p>\n

            I look forward to your answers!<\/span><\/p>\n

             <\/span><\/p>\n

            Kind regards,<\/span><\/p>\n

            Mona<\/span><\/p>\n","protected":false},"template":"","class_list":["post-345402","topic","type-topic","status-closed","hentry"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t