delta t and TD

[frank14]

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]

Hi Frank

Looking around the interweb I found this:

Delta (upper case Δ, lower case δ) is the 4th letter of the Greek alphabet. In the system of Greek numerals it has a value of 4.

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

• A macroscopic change in the value of a variable in mathematics or science.
• Any of the delta particles 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 in mathematics.
• The Dirac delta function in mathematics.
• A mark for deletion in proofreading. The usage is said to date back to classical times.

Letters that arose from Delta include the Roman D and the Cyrillic letter De .



Not sure of the origin of the use though.

[frank14]

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]

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]

Frank

thanks for the input

Unfortunately the hypothsesis of ergodicity and the Boltzmann constant did a slow Brownian motion way way past my brain.
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.

Regards

frank14