Pressure drop answer compare to Darcy Weisbach

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seandclark
Posts: 3
Joined: Wed Sep 26, 2018 9:30 pm

Pressure drop answer compare to Darcy Weisbach

Post by seandclark » Wed Sep 26, 2018 10:43 pm

I performed a pressure drop calculation in the flow calculator and compared the result to another spreadsheet that uses the Darcy-Weisbach equation for pressure drop - the results did not match. I double check the spreadsheet equation and calculations by hand and it appears to be correct.

The Darcy-Weisbach is simplified by assuming laminar flow and using viscosity ( delta p / L = (128 / pi) - uQ /D^4)

Since the parameters in the program indicated the flow regime was Laminar I expected the results to match. Can you let me know why the results would be different? What underlying equation are involved that cause the result to be different.

I am not sure how to include a screen shot from the program with parameters and results, so let me know if you need more information.

Regards,

Sean

admin
Site Admin
Posts: 365
Joined: Mon Feb 08, 2010 7:47 pm

Re: Pressure drop answer compare to Darcy Weisbach

Post by admin » Fri Sep 28, 2018 7:54 am

Hi,
Here is the equation used in the calculator:
https://www.pipeflowcalculations.com/pi ... cy-formula

You can press copy button in the calculator and your results will be in clipboard, and then paste here to check.

Zoran
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seandclark
Posts: 3
Joined: Wed Sep 26, 2018 9:30 pm

Re: Pressure drop answer compare to Darcy Weisbach

Post by seandclark » Fri Sep 28, 2018 2:41 pm

Thank you, I did see that already. Can you explain, in theory, why the answers would be different. It seems to me that the answers should match. Is there a reason why the equation you reference includes factors that are not in the Darcy-Weisbach equation for Laminar flow. the only explanation would be that the equation your reference includes something that is not accounted for in the other equation. What is it?

Regards,

Sean

seandclark
Posts: 3
Joined: Wed Sep 26, 2018 9:30 pm

Re: Pressure drop answer compare to Darcy Weisbach

Post by seandclark » Fri Sep 28, 2018 4:54 pm

Sorry, I think I found an error in the equation I was comparing to. The conversion factor for units was incorrect. Please retract my question.

Regards,

Sean

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