Fluids

Fluids

Changing material in fluent has no effect on results

    • Ryan_Mitchell
      Subscriber

      Hi,

      I am trying to compare the outlet temperature achieved by using different fluids in a pipe that is subject to cooling airflow.

      I have set the mass flow rate of the fluid and the air as well as the temp at the inlets and to my knowledge everything else has been set up according to a tutorial that i have watched.

      Please could someone a

      dvise that when i change the material properties of the fluid the outlet temp does not change.

      For info each time i run the simulation I just change the material properties of water liquid in fluent. I have used surface integrals and average static temp at fluid outlet to get the outlet temp.

      I have tried to attach the file but it's too large. I have attached a photo where the boundary conditons import in a strange way from the meshing.

    • Keyur Kanade
      Ansys Employee
      You may be having multi body part. For that you will need to use share topology. nPlease check following videosnnDM Share
      Share
      make sure that you have changed material of fluid in cell zone condition panel. By default it is air. nRegards,nKeyurnHow to access Ansys Online Help DocumentnHow to show full resolution imagenGuidelines on the Student CommunitynHow to use Google to search within Ansys Student Communityn
    • Ryan_Mitchell
      Subscriber
      Hi,nThanks for the reccomendations. The time to run iterations for this model was very long, perhaps this is a result of the topology? So I changed to a 2d asymetric model as created in this video, in which outlet temperatures of nanofluid are compared (these are the fluids I am comparing). I get the same issue. Very minimal teperature change. I have ehthylene gylcol and water as a base fluid and when comparing the results from that with the same fluid plus 2.0% copper nanopartciles the increase in delta t is very small in a turbulent flow condition. I have calculated the reynolds number and change the velocity of the different fluids as a function of this due to the varying density and viscocity. Any thoughts as to the small change? n
    • Ryan_Mitchell
      Subscriber
    • Rob
      Ansys Employee
      Was the DPM run coupled, ie interacting with the flow? Is that 2% copper by mass or volume? n
    • Ryan_Mitchell
      Subscriber
      Sorry rob I am new to the software as you can probably tell. You?ll have to elaborate on the DPM run? The 2% copper is by volume. I use a set of equations to calculate the nano fluid properties of density, thermal conductivity, specific heat capacity and viscosity. These are then entered into the material data base when creating the new fluid. n
    • Rob
      Ansys Employee
      Did you include the copper particles or just change the fluid properties? n
    • Ryan_Mitchell
      Subscriber
      I just change the fluid properties as per my calculations for each different nano fluid I am using n
    • Rob
      Ansys Employee
      Can you confirm you've got the correct fluid (check Cell zones for fluid label). How much of a difference does the change make to the specific heat capacity? n
    • Ryan_Mitchell
      Subscriber
      Hi Rob, nYep I always check the cell zone to make sure it updates once I have updated the materials. Below is a summary of my Specific heat capacities. I will double check my calculations on excel. Formula below.nnn
    • Ryan_Mitchell
      Subscriber
      I have checked my results for the table above and they appear to be correct. n
    • Ryan_Mitchell
      Subscriber
      Just to update this post I have increased the volume % of nanoparticles to 5% and acheived a 0.79 degree kelvin difference in temp with copper as the particle material. Using q = mcdelta t this leads to a 15% increase in heat transfer over that which is achieved by the pure Ethylene glycol fluid in the same pipe with a constant wall temperature applied. This is more in line with what I would expect. n
    • Rob
      Ansys Employee
      With value changes like that make sure the mesh is refined and you're converging below the default criterion. nAlso check the temperature profile on the outlet: is heat transfer rate or cp what determines the outlet temperature? n
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