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Pressure drop over a perforated plate

Question asked by Dom Enico on Sep 23, 2014
Latest reply on Sep 30, 2014 by Jared Conway

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Hi,

I am a student who is fairly new to CFD so forgive my ignorance on the subject at hand.

I have designed a duct with many slots that will be used to provide cooling in a cabinet. Essentially, I feel this is a perforated plate and I would like to know the pressure drop over it to be able to select a fan.

I've set up a 'virtual wind tunnel' in Solidworks as discussed in this thread https://forum.solidworks.com/thread/21433?q=Pressure%20drop%20throu . I've made the wind tunnel 1m long with a volumetric flow rate of 0.2m3/s at one end and environmental pressure at the other. I then set up surface pressure goals at each end and then found the difference between them to determine pressure drop. Here is a diagram:

Here is the 'perforated plate': It is 1320 x 1360 mm and the slots are 200x10mm and the thickness is 1mm. Free area is 8.5

I've set up a local initial mesh for the plate with a mesh size of 1mm.

My problem is that I am only getting a pressure drop of about 2 Pa. I initially set up the study with one quarter of the plate (and one quarter flow rate) and got similar results as expected.

I feel this is quite small and wondering if there is an issue in my model.

Are there any suggestions?

Thanks

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Jared Conway Sep 23, 2014 7:47 PM

how do you know it is too small? do you have something with known results that you can check?

second, do you know your part is getting meshed properly? if not, it could just be that things are being skipped.

what is the pressure drop without any plate at all? that is a good gauge

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Mark Keown Sep 24, 2014 4:15 AM

Just because you have an expensive CFD software dose not mean that it is the best tool for solving all problems.

For flow through plates use: I.E. Idelchick, Flow Resistance: A Design Guide for Engineers. This reference (or equal) has the flow resistance calculations derived from lab test. Use the simplest tool that will give you the most accurate results - in this instance it is not CFD. With the plate resistance known then go back and use CFD to solve your system problem.

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Pressure drop coefficients for thin perforated plates.docx268.8 KB

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Dom Enico Sep 25, 2014 9:53 AM

Thank you both for the replies. I found some online calculators for pressure drops and was getting similar results. However these were not accompanied by the relevant theory but many thanks to Mark for pointing me in the right direction. While I do not have access to that book, using your notes and others (found here http://www.design1st.com/Design-Resource-Library/engineering_data/AirFlowResistanceofPerforatedPlates.pdf ) I was obtaining some consistent results.

Thanks for your help!

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Jared Conway @ Dom Enico on Sep 29, 2014 5:36 PM

so the software was right in the first place?

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Dom Enico @ Jared Conway on Sep 30, 2014 7:48 AM

Its definitely within the range of the values I have been getting with formula.

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Jared Conway @ Dom Enico on Sep 30, 2014 8:14 PM

this is why it is important to have an idea of what type of result you're expecting. good job finding a way to check your solution.

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6 Replies

Jared Conway Sep 23, 2014 7:47 PM
Mark Correct
Correct Answer
how do you know it is too small? do you have something with known results that you can check?

second, do you know your part is getting meshed properly? if not, it could just be that things are being skipped.

what is the pressure drop without any plate at all? that is a good gauge
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Mark Keown Sep 24, 2014 4:15 AM
Mark Correct
Correct Answer
Just because you have an expensive CFD software dose not mean that it is the best tool for solving all problems.
For flow through plates use: I.E. Idelchick, Flow Resistance: A Design Guide for Engineers. This reference (or equal) has the flow resistance calculations derived from lab test. Use the simplest tool that will give you the most accurate results - in this instance it is not CFD. With the plate resistance known then go back and use CFD to solve your system problem.
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- Pressure drop coefficients for thin perforated plates.docx268.8 KB
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Dom Enico Sep 25, 2014 9:53 AM
Mark Correct
Correct Answer
Thank you both for the replies. I found some online calculators for pressure drops and was getting similar results. However these were not accompanied by the relevant theory but many thanks to Mark for pointing me in the right direction. While I do not have access to that book, using your notes and others (found here http://www.design1st.com/Design-Resource-Library/engineering_data/AirFlowResistanceofPerforatedPlates.pdf ) I was obtaining some consistent results.

Thanks for your help!
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- Jared Conway @ Dom Enico on Sep 29, 2014 5:36 PM
  Mark Correct
  Correct Answer
  so the software was right in the first place?
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  - Dom Enico @ Jared Conway on Sep 30, 2014 7:48 AM
    Mark Correct
    Correct Answer
    Its definitely within the range of the values I have been getting with formula.
    Like • Show 1 Like1
    Actions
    - Jared Conway @ Dom Enico on Sep 30, 2014 8:14 PM
      Mark Correct
      Correct Answer
      this is why it is important to have an idea of what type of result you're expecting. good job finding a way to check your solution.
      Like • Show 0 Likes0
      Actions

Pressure drop over a perforated plate

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