Fan air flow

Discussion in 'BigBox General Chat' started by Alex9779, May 25, 2016.

  1. Alex9779

    Alex9779 Moderator
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    Somehow I lost the previous results (SWx crashed, what a surprise!) and had to redo. Refined the parameters and calculation space...
     

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  2. Chase.Wichert

    Chase.Wichert Well-Known Member

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    I uploaded the file to dropbox. I'll now take a look at your results that you just posted
     
  3. R Design

    R Design Well-Known Member

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    Super interesting.

    1) Do we have a point of comparison? In order to understand the numbers it would be good to understand what 1 m/s "means" in terms of cooling. For example does 1m/s correspond to turning the v1 fan up to 55%?

    2) Is there a way to increase the "sensitivity" of the colour scale? We're most interested in the flow where it hits the print and yet, where it's coloured dark blue it could be anything down to 0 m/s. We need a couple more colours at the low end of the scale!
     
  4. Alex9779

    Alex9779 Moderator
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    I already set it finer. I am trying to do a bit more...
    The fan is set at full speed now...
     
  5. Alex9779

    Alex9779 Moderator
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    To 1) I could take that into account when I get further down. I can "heat" up the part. The air is at I think 20 C. Can change that too. Then I can calculate the temperature over time.
    But again we are at the point of assumptions we make to get closer to reality. How hot should the part be? And still there is the interpretation of the results.
    But my first goal was just to get an impression of how the air is distributed around the part. We see a great speed drop of the flow until it hits the part inside the duct...
     
  6. zauberertz

    zauberertz Member

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    I have created some screenshots for all that do not have the viewer:
    Fan_flow_plain.png Fan_flow_Cube.png
     
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  7. mike01hu

    mike01hu Well-Known Member

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    Yes, you have reached that point where the model size and shape, as well as temperatures and force of air delivery to the duct will have a substantial effect on the flow. I think any further effort on simulated models is not gong to be helpful. The first simulation showing the exit flow is the most informative and just enhancing the uniformity of that is the real target and it is fairly close.

    This kind of analysis in novel in 3D printing and shows how this tech can work towards a better defined science in the field. So once again thank you Alex!
     
  8. Alex9779

    Alex9779 Moderator
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    Yeah maybe. There would be too much and you can't really optimism for everything.

    Yep but what I also wanna take into account is the "close bed situation" when the air can't flow away but may go up between the nozzles. I see it on my UM2. The hole for the nozzle in the duct is pretty small. Maybe additional material around the hotend blocks can minimize the flow upwards and force it to the outsides and so prevent cooling the hotends too much when printing very flat models or near the bed...
     
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  9. mike01hu

    mike01hu Well-Known Member

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    Yes, there is also the effect of back pressure due to proximity to the bed but you still fall into the model shape and size scenario.
     
  10. Alex9779

    Alex9779 Moderator
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    Well I think I am going to define "some" cases that how I learned to do it :D
    Free/open flow, close to bed let's say 2mm above , that's 10 layers 0.2mm. I still have to figure out how to simulate different fan speeds...
    Interesting would be a time analysis with the bed moving down and the fans speeding up. Without a model but I have the fans at their desired max at about layer 10 or so...
     
  11. mike01hu

    mike01hu Well-Known Member

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    I'm looking forward to the results!
     
  12. R Design

    R Design Well-Known Member

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    We should have some idea whether the head on airspeed in Chase's design is any good or not.

    @Alex9779 maybe if you re-run your first simulation of the V1.1 fan duct using the same numbers for the power of fan that you used with Chase's design? That way we can compare the head-on air speeds, see if they are similar.
     
  13. Alex9779

    Alex9779 Moderator
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    Ya I will do this...
     
  14. Henry feldman

    Henry feldman Well-Known Member

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    Sort of amazing that in the chat community here we have an advanced CAD design with someone doing FEA on airflow through the ducting...
     
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  15. Miasmictruth

    Miasmictruth Well-Known Member

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    The BigBox has brought together people all over the world with quite the verity of experience and occupations :)
     
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  16. Alex9779

    Alex9779 Moderator
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    Results...
    Sorry have to zip, easm is not allowed...

    @Mike Kelly maybe you can allow eprt, easm and edrw as file extensions? The files are just as big as when I zip them...
     

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  17. Alex9779

    Alex9779 Moderator
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    But as I said, with the fan design you loose a lot of speed, the exit speed on the current hybrid fan shroud is higher for about 1m/s...
     
  18. mike01hu

    mike01hu Well-Known Member

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    Nice analysis Alex. I now wonder what effect the hotend heatsink fans will have as one of them is feeding the low pressure area of the cooling fan but the second one is drawing air from it. I wonder if the fan on that heatsink can be mounted in reverse so that it sucks air across the heatsink so also feeding the low pressure area of the coolig fan. It gets more complex!
     
  19. Chase.Wichert

    Chase.Wichert Well-Known Member

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    Actually you have a good point, now that I went to a bottom mount design I have more room in the base to expand front and back to house the belt track so I could move it to the rear or the front in or order to get a better fan mount and just more room for the fans in general to help with airflow. I'll look into that, I haven't look at Alex's results yet, I am feeding my son and trying to get him to sleep before I can get to my computer
     
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  20. mike01hu

    mike01hu Well-Known Member

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    Good luck with the lad! I'm heading to bed now:cool:
     

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