3 Replies Latest reply on Nov 26, 2015 8:08 AM by Andreas Klumpp

    Doubt regarding Solidworks Flow Simulation of  Heat Exchanger!

    Gerardo Perdomo

      Hi there, I am currently starting to use Solidworks Flow Simulation 2014 for some assignment on Heat exchangers and I have some questions about how it works. First I started with the Wizard, I specified the units, chose internal study with conduction in solids, chose the fluids (lets supose blood and water) and solid material, and decided to go with adiabatic wall. I left the level of the initial mesh in 3 and then started specifying the fluid domains and the boundary conditions.

       

      For my example I will be simulating the heating of blood using hot water circulating around the tube in which the blood flows. So here are my conditions:

       

      1. Volume Flow for the blood Inlet with 30 Celsius

      2. Environmental Pressure for the blood outlet

      3. Volume Flow of Hot water Inlet at 50 Celsius

      4. Static Pressure at the outlet

       

      So my doubts begins when choosing the goals. What I want to know is to estimate either the water volume flow at a same temperature, or estimate the temperature at a same vol flow in order to get a final blood temperature of 40C at the outlet.

       

      I have the option to choose diferent goals depending on what I want, but for the main purpose of this study I think on choosing a global goal of the temperature fluid,  global goal on temperature of solid and a surface goal at the lid on the blood outlet. I suppose that with those 3 goals it will be enough for this simulation, maybe an equation goal dividing the surface goal between 40. Any recommendations??

       

      But well, things are getting a little complicate for me when I have the option of choosing between min avg max or bulk avg values. I ran some simulations to see the differences between avg and max, for example, and they are way different. I have readed on other forums discusions about those values but I havent really understand, if maybe someone can explain the differences of min avg max and bulk using some examples it would be awesome for me. Especially because English is not my native language so I struggle sometimes.

       

      After specifying the goals and running the simulation I know there is a way to ''optimize'' or estimate values for a desire result with a Parametric Study. Since I only want to know the final temp of the blood I was thinking on using the Goal Optimization study and choosing as a parameter the temp of water or the volume flow of water with a range, and then for the outpout parameter I was planning on introducing equation goal to a target value of 1 (temp desired of blood/40=1)

       

      Maybe there is a simpler way for the optimization without using the Eq Goal.

       

      Thanks for any help,

       

      Gerardo

        • Re: Doubt regarding Solidworks Flow Simulation of  Heat Exchanger!
          Andreas Klumpp

          Hi Gerardo,

           

          based on what you want to achieve, 40°C at the outlet, I suggest you to define a surface goal average temperature at the blood outlet lid (blood temp outlet).

          Then you can define a parameter study as a goal optimization, there you can define the goal parameter (blood temp outlet) with a value 40°C and either the water inlet volume flow or the inlet water temperature as the variable parameter to get the desired values to achieve the 40°C at the outlet.

          Hope this helps.

           

          BR,

          Andi

            • Re: Doubt regarding Solidworks Flow Simulation of  Heat Exchanger!
              Gerardo Perdomo

              Hi Andreas,

               

              Thanks for answering. I really appreciatte it.

               

              Just to make sure if I understand what you said, it is better if I only specified avg surface goal on the blood outlet lid? Or it is ok if I insert the surface goal and keep the other two max global goal?

               

              Also, whats the difference between those min avg max and bulk avg values? Why do I get different results when using them?

               

              Best regards,

               

              Gerardo

               

              Andreas Klumpp

                • Re: Doubt regarding Solidworks Flow Simulation of  Heat Exchanger!
                  Andreas Klumpp

                  Hi,

                   

                  generally, goals are not like boundary conditions and therefore they does not have any influence on your calculation. You can keep as much goals as you like. Think about it like you would have measuring devices installed an a physical testing. As soon as these values does not change anymore - your results converged and you do have a steady state situation.

                  By default, all goals are used for converge control. Having some global goals does make sense.

                   

                  For surface goals, I think min and max values are clear, min is the minimum temp on this surface, max the maximum value on this surface. The average value is calculated over the surface. The bulk average values (or mass average value) takes the mass into account and is weighting the temperatures higher were more mass is flowing through. Therefore bulk average temperature might be the more accurate goal you are looking for.

                   

                  Here is another explanation I have found on the web:

                  SolidWorks Flow Simulation Tech Tip: Bulk-Average Temperature

                   

                  Hope this will make it clear (I am not a Native Speaker as well).

                   

                  -Andi