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R
rosa26791-Visitor
1-Visitor
April 22, 2018
Solved

MathCAD 15 solve block error

  • April 22, 2018
  • 2 replies
  • 3043 views

Hello,

I am working on creating a model to design an wastewater treatment process. I have set up the mass balances and but keep getting function errors dealing with the flow, which I am hoping to be able to change in further iterations to see how the system will handle it. I have checked and the guesses are within a reasonable range. I have reworked this many times and have been unable to get any answers. I am very new to mathCAD so I could be missing something relatively simple, I appreciate any help you all can give me!

Best answer by terryhendicott

Hi,

 

Some of the equations in the solve block are not consistent units.  These need to be fixed first.  I try some of the equations prior to the solve block to test they are unit consistent.  You need to check them all.

2 replies

T
terryhendicott21-Topaz IIAnswer
21-Topaz II
April 22, 2018

Hi,

 

Some of the equations in the solve block are not consistent units.  These need to be fixed first.  I try some of the equations prior to the solve block to test they are unit consistent.  You need to check them all.

R
rosa26791-VisitorAuthor
1-Visitor
April 25, 2018

Thank you all for you help! It was a problem with the units as suggested. I was able to fix the units issue by using L/mg wherever the unit less number was used and it started putting out the numbers I needed.

 

 

L
LucMeekes23-Emerald IV
23-Emerald IV
April 22, 2018

I see you're using Mathcad 15.

Apart from the fact that your equations must be unit-balanced, as Terry has pointed out:

I remember having read that Mathcad 15 cannot work with units in solve blocks. I hope I'm wrong.

 

Success!

Luc

T
terryhendicott21-Topaz II
21-Topaz II
April 22, 2018

Hi,

 

step one is to get the unit consistency in the equations.

step 2 is to get round the inability of the solve block to use units.

There is a workaround so don't be discouraged from solving the unit inconsistency in the equations first.

 

For instance i think the factor "Xrh" should be mg/L too?

 

Cheers

 

 

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