5 Replies Latest reply on Mar 24, 2014 2:27 PM by Jared Conway

    Toggle surface source

    Bill Clark

      I am working on a time dependent study of heat flow in solids and fluids (air).  I have an assembly of various materials and I am simulating a thermal electric cooler as a heat source (1.4W).  I have a location for a thermistor in the assembly and a surface goal of 338K at that location.  I would like to switch off the TEC when that surface reaches 338K.  I cant quite figure out the F(goal) - Table dependency type.  I have the dependent on goal set to the SG Min Temperature (solid) 1 which is my surface of interest. Then there are 4 options...

       

      Switch ON when goal > control value;

      Switch OFF when goal > control value;

      Switch ON when goal < control value;

      Switch OFF when goal < control value.

       

      no matter what I do, it seems like the TEC never comes on and for some reason the temp at that surface drops to 0K.

       

      My control value is 340K

      And I am not sure if the dead band is supposed to be a value or a differential.  The chart in the help section implies it should be a differential but I have tried it as 1K and 339K.

       

      Ambient and all solids start at 293K

       

      For the record, I am getting beleivable results in a steady state, The temp just goes to high.

       

      Does anyone know how to use these switches?

        • Re: Toggle surface source
          Jared Conway

          can you post some screenshots of your goal definition and your dependancy settings and your TEC settings?

           

          i tried something like this recently and it was confirmed as a limitation from the developers. just want to make sure we're talking apples to apples.

           

          also for the TEC going too high of temp, that may be a setup issue.

            • Re: Toggle surface source
              Bill Clark

              Sure, thanks for getting back to me...

               

              Here is the suface goal

              Capture2.PNG

              Capture1.PNG

               

              Here is the tec (surface source) with the dependency box

              Capture3.PNG

              Again, I don't know how to interpret the control value vs the goal and the dead band.  My tec just does not come on.  (I have been messing around so there may not be any logic left in the settings ;-)

                • Re: Toggle surface source
                  Jared Conway

                  version/service pack?

                   

                  the dead band is explained pretty well in the help

                   

                  in your case you're telling the software when your goal is greater than the temperature, turn it off. but don't do it until it has gone above your control value plus the dead band. normally the dead band is a slightly larger value so that the control isn't turned on and off all the time.

                   

                  are you sure that a turning off strategy is what you want?

                   

                  (also thanks for the screenshots, i thought you were actualy using a TEC)

                    • Re: Toggle surface source
                      Bill Clark

                      "version/service pack?"

                              Solidworks 2014 SP1.0

                              Flow 2014 SP1.0 Build 2573

                       

                      "the dead band is explained pretty well in the help"

                              I agree that there is good explanation in the help files but when I can't get something to work, I start questioning everything.  The image shows it as a differential value but I wasn't sure if it was specified as such or if it was generated by the software based on an actual temperature that the user entered.

                      Capture6.PNG

                      (Also I didn't know that the explanation of the 4 toggle modes was hidden under some type of click-expand dohickey)

                       

                      "in your case you're telling the software when your goal is greater than the temperature, turn it off. but don't do it until it has gone above your control value plus the dead band. normally the dead band is a slightly larger value so that the control isn't turned on and off all the time."

                      This is what i want, correct?  You say plus the dead band... this is because I have the temperature of my goal set as "minimum value"?

                       

                      "are you sure that a turning off strategy is what you want?"

                      I just spoke with my electrical engineer and he corrected my thining on this... I thought the TEC shut off but it actually switches polarity and starts a cooling cycle and flip flops back and forth.  So no, I am not sure that is what I want to do.

                       

                      "i thought you were actualy using a TEC"

                      I don't know how to create a TEC and cant find any tutorials for it.  When I say create a tec I mean model the actual TEC we are using and the "engineering database" is extremely lacking unless you shell out the cash to by the electronics add on.  If you want to start another thread on TEC modeling I would be a very willing subscriber.

                       

                       

                       

                       

                      SO.... If I have it set to come on until it reaches the goal plus dead band, why doesn't it come on?

                        • Re: Toggle surface source
                          Jared Conway

                          build a really simple example that you can post. if you can't make it work in a simple model that you can control how it should come on and off, i'd submit to your reseller. haven't had a chance to build my own and check but i did have a problem with them not coming on/off a few versions back. maybe that problem has come back.