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1-Visitor
April 21, 2014
Solved

More PDEsolve help!

  • April 21, 2014
  • 1 reply
  • 993 views

My previous question was solved, but now I'm having another issue with the same mathcade file. The first 8 equations in the solve block are correct, so the error lies within my Temperature equation, I believe. The error I'm getting right now states 'the number of functions must be equal to the number of equations.'

Best answer by AlanStevens

You had two mistakes in the expression for Temp.t: a missing bracket at the end, and an incorrect expression involving the H2O term in the top line. These are fixed in the attached.

However, I have to say that you have chosen a ridiculous way to construct Temp.t! It's no wonder there were some mistakes. Break this sort of expression into smaller, bite-size chunks, using more function definitions before the solve block, so that it is easier to see what is happening and easier to debug.

Alan

Found a third error (in the denominator of Temp.t). Corrected file attached.

Version c is a simplified (though still pretty complicated!) version that is equivalent to version b, but is easier to debug (I think).

However, I think there must be something wrong with your basic equations for dTemp/dt, as it produces some silly temperatures.

Sometimes when I run either of these worksheets I get a "repeated singularity" error, but simply re-calculating the worksheet usually gets rid of it!!!

1 reply

19-Tanzanite
April 21, 2014

You had two mistakes in the expression for Temp.t: a missing bracket at the end, and an incorrect expression involving the H2O term in the top line. These are fixed in the attached.

However, I have to say that you have chosen a ridiculous way to construct Temp.t! It's no wonder there were some mistakes. Break this sort of expression into smaller, bite-size chunks, using more function definitions before the solve block, so that it is easier to see what is happening and easier to debug.

Alan

Found a third error (in the denominator of Temp.t). Corrected file attached.

Version c is a simplified (though still pretty complicated!) version that is equivalent to version b, but is easier to debug (I think).

However, I think there must be something wrong with your basic equations for dTemp/dt, as it produces some silly temperatures.

Sometimes when I run either of these worksheets I get a "repeated singularity" error, but simply re-calculating the worksheet usually gets rid of it!!!