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frank14
12-10-2010, 02:03 PM
Good day all

I know its accepted practice in our industry to use delta t when refering to the same media, eg air in / air out and TD when refering to two different media, refrig temp and air/water temp.

Could one of the boffins on the site provide some reference for this

Regards

frank14

frank
12-10-2010, 03:16 PM
Hi Frank

Looking around the interweb I found this:

Delta (upper case Δ, lower case δ) is the 4th letter of the Greek alphabet (http://www.economicexpert.com/a/Greek:alphabet.htm). In the system of Greek numerals (http://www.economicexpert.com/a/Greek:numerals.htm) it has a value of 4.

The upper-case letter Δ is used as the symbol for:


A macroscopic change (http://www.economicexpert.com/a/Derivative.htm) in the value of a variable in mathematics or science.
Any of the delta particles (http://www.economicexpert.com/a/Baryon.htm) in particle physics.

The lower-case letter δ is used as the symbol for:


A microscopic change in the value of a variable in mathematics or science.
The Kronecker delta (http://www.economicexpert.com/a/Kronecker:delta.htm) in mathematics.
The Dirac delta function (http://www.economicexpert.com/a/Dirac:delta:function.htm) in mathematics.
A mark for deletion in proofreading (http://www.economicexpert.com/a/Proofreading.htm). The usage is said to date back to classical times.

Letters that arose from Delta include the Roman D (http://www.economicexpert.com/a/Character:D.htm) and the Cyrillic letter De .



Not sure of the origin of the use though.

frank14
14-10-2010, 09:56 AM
Frank
Hi, Thanks for the reply.
I'm looking for a reference to show they have different applications and are not interchangeable when used in our industry

Regards

frank14

frank
14-10-2010, 07:19 PM
Did you follow the link to the Macroscopic Change, which details the explanation you are looking for?
dt = a 'change' whereas
TD = a temperature difference

Also, this makes interesting reading http://en.wikipedia.org/wiki/Temperature

frank14
18-10-2010, 08:45 AM
Frank

thanks for the input

Unfortunately the hypothsesis of ergodicity and the Boltzmann constant did a slow Brownian motion way way past my brain.:D
Not sure if it was just my eyes playing up, but I still did not see a reference that says delta t refers to same media or TD refers to two different media.:cool:

Regards

frank14