topic Re: Results in mathcad prime 9 not as expected in Mathcad

Results in mathcad prime 9 not as expected

MP_10403367 — Tue, 20 Jun 2023 17:48:58 GMT

A=Q/U*T should give m^2 , where Q= heat capacity in kW, U heat transfer coefficient W/m^2*K, T is temperature difference in K.

The area I am getting is in Kg^2. Why?

Re: Results in mathcad prime 9 not as expected

Werner_E — Tue, 20 Jun 2023 18:18:15 GMT

If we have to assume invisible pairs of parentheses around U*T and also around m^2 * K, then you are right, the result should be and actually IS an area.

But without seeing what you actually had done (not, what you think you had done) its not possible to tell you what went wrong.

So attach your sheet!

Re: Results in mathcad prime 9 not as expected

MP_10403367 — Tue, 20 Jun 2023 18:23:40 GMT

Re: Results in mathcad prime 9 not as expected

Werner_E — Tue, 20 Jun 2023 19:59:56 GMT

Pls attach the worksheet, not just a picture.

Its hard to impossible to debug a picture, but I noticed that the "m" in the evaluation of U is not labelled as unit.

So my best guess is that you had defined a mass variable (of approx. 3.5 kilo tonne) somewhere in the sheet and called it "m". This would perfectly explain the result in kg^2.

Re: Results in mathcad prime 9 not as expected

MP_10403367 — Tue, 20 Jun 2023 20:13:15 GMT

I attached the file to email but it kicked back saying not allowed. How can I post in the forum?

Prakash Mokkarala, Ph.D., P.E. | Sr. Civil/Structural Engineer | Tarsco

25000 Pitkin Road | Spring, TX 77386

Full Service Provider for Storage Tanks and Terminals

www.tfwarren.com

Re: Results in mathcad prime 9 not as expected

Werner_E — Tue, 20 Jun 2023 20:07:01 GMT

I don't use email to post in this forum, so I don't know if attachments are allowed when posting this way and how you would deal with 'em..

In the browser you simply drag the file to the area below of the edit window or click there to browse for the file.

Have you also noticed that I had edited my last answer and explained the result with a mass variable you may have defined?

Re: Results in mathcad prime 9 not as expected

MP_10403367 — Tue, 20 Jun 2023 20:10:17 GMT

here is the file

Re: Results in mathcad prime 9 not as expected

MP_10403367 — Tue, 20 Jun 2023 20:15:16 GMT

m was used as meter in SI units. I was going back and forth between SI and US units.

Re: Results in mathcad prime 9 not as expected

Werner_E — Tue, 20 Jun 2023 20:23:24 GMT

@MP_10403367 wrote:

here is the file

And here is the culprit:

Whenever you typed "m" below of this definition, Prime assumed that you mean it to be that very mass variable, while you assumed it to be the unit meter.

When you defined

you actually wanted m to be the mass variable you defined, but when you defined

you intended m to be the unit meter while Prime still assumed the mass variable and this caused the problem

Two ways to solve that problem:

1) Manually re-label ever occurrence of "m" which should be interpreted as meter manually as "unit"

2) Chose another name for that mass variable and don't forget to use that very name in later calculations where the mass is meant to be used.

I would go for option 2)

Re: Results in mathcad prime 9 not as expected

MP_10403367 — Tue, 20 Jun 2023 20:20:10 GMT

Thanks. That was my mistake. Appreciate your help.