MathCAD Math is wrong?

[ptc-5071035]

So I'm trying to do some simple math and it's not agreeing with my calculations. I'm doing some simple multiplication and division and it's giving me a negative result. I'm wondering if the unit conversions aren't quite right? I'm attaching the file so if anyone can offer some input, I would appreciate it. I have two equations side by side that show what MathCAD is giving me and what the simple multiplication and division SHOULD give me.

[ValeryOchkov]

[ValeryOchkov · Accepted solution]

or so

[ptc-5071035]

Thanks a ton! I'm still getting used to these units.

[ValeryOchkov]

I see in one NIST (National institute of standards and technology in Boulder - www.nist.gov) reference book so

I ask my friend - one of the authors of this book, why they are using the Rankine degree in the specific heat, but the degree Fahrenheit (equal to degree Rankine) in thermal conductivity.

The answer was - it's an American engineering tradition and we can not change it. We can change the U.S. Constitution rather than this tradition.

We can see the degree Celsius (equal to degree Kelvin) in thermal conductivity only in old Russian reference books.

[ELSID]

Valery,

The 10degree delta F that you crossed out is technically correct too! I revamp my constants (e.g. Cp) such thath the units are NOT degrees F but Delta degrees F. Works like a charm and my cohorts usually don't even "see" the delta during the reviews. It keeps things consistent for those of us in the US... goofy as it might be

[ValeryOchkov]

ELSID wrote:

Valery,

The 10degree delta F that you crossed out is technically correct too!

I use a lot of english reference book on power engineering but I never seen delta F degree for temperature.

Only in Mathcad

[ValeryOchkov]

We can use delta m and delta feet for same problem for example (from my old book "Unts in Mathcad and Maple" - http://twt.mpei.ac.ru/ochkov/work2_eng.htm😞

"We can see another engineering error associated not with the units but with a relative scales of units. One dridge was built (without Mathcad ) across the Rhine river. Germans dit from one coast, and the other Swiss. When the bridge spans were connected in the middle of the river, it was found that the difference in their altitudes was almost half a meter. The reason for the error was that in Germany the construction standard of zero level was North Sea, and in Switzerland Mediterranean."

The common standart must be... the center of Earth (Kevin or Rankine) but not North See (Fahremheit) or Mediterranean (Celsius)

Try please to calculate in Mathcad this task with delta meters!