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10-17-2020
03:44 AM

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10-17-2020
03:44 AM

Heat capacity unit error - ODE function

Hello everyone,

This is my first time ever using MathCAD. I have no ideas but watching some video help me to create this sheet. I got the error unit of Cp (heat capacity) = BTU/lb*F. MathCAD error is value should be scalar or matrix.

I also set up the ODE function. Would you please help me to take a look this and guide me where I was wrong?

Thank you so much for your help. I attached the file in this post

Solved! Go to Solution.

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10-17-2020
08:39 AM

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10-17-2020
08:39 AM

As Valery pointed out you used F (Farad) instead of °F (Degree Fahrenheit).

Furthermore you have to be aware, the working with temperatures can be quite tricky! Prime converts all temperature values to K (Kelvin) and does the calculations in K. Because the conversion between K and °F is not homogenous (its not a simple factor) this quickly can create confusion and this is the reason why Prime offers °F AND Delta°F. Look at the picture below.

Another error in your sheet is that in the solve block you wrote the IC in two separate regions (one with "T(0 min)" and the other with "..=120°F".

Hope the attached sheet helps. Instead of "Delta°F" you may also use "R" (Rankine) as Valery had suggested.

4 REPLIES 4

10-17-2020
06:32 AM

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10-17-2020
06:32 AM

10-17-2020
09:30 AM

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10-17-2020
09:30 AM

Thank you so much! I really appreciated your help. Thank you so much again

10-17-2020
08:39 AM

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10-17-2020
08:39 AM

As Valery pointed out you used F (Farad) instead of °F (Degree Fahrenheit).

Furthermore you have to be aware, the working with temperatures can be quite tricky! Prime converts all temperature values to K (Kelvin) and does the calculations in K. Because the conversion between K and °F is not homogenous (its not a simple factor) this quickly can create confusion and this is the reason why Prime offers °F AND Delta°F. Look at the picture below.

Another error in your sheet is that in the solve block you wrote the IC in two separate regions (one with "T(0 min)" and the other with "..=120°F".

Hope the attached sheet helps. Instead of "Delta°F" you may also use "R" (Rankine) as Valery had suggested.

10-17-2020
09:31 AM

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10-17-2020
09:31 AM

Thank you so much for the attached file. I have better ideas. Have a good day!