# Thread: Delta T for Ahu, Chiller and district cooling systems

1. The question you have is incredibly complex. There is no "20 degree drop and it's good" type thing anymore. There's so much going into it from the design, flow requirements of chilled water, air volume, air temperature and humidity that unless you ask a very specific question with some other data/model numbers we aren't going to able to assist you.

2. Regular Guest
Join Date
Dec 2011
Posts
34
Originally Posted by ryan1088
The question you have is incredibly complex. There is no "20 degree drop and it's good" type thing anymore. There's so much going into it from the design, flow requirements of chilled water, air volume, air temperature and humidity that unless you ask a very specific question with some other data/model numbers we aren't going to able to assist you.
Ok thanx for yur helpful response.
I asked this question as i heard that delta T for district cooling system shall be around 14-16, whereas the value for chiller is 12.
How do we calculate delta T for a system. Formula for it?
I know a formula,
Gpm/Tr = 24/delta T
But then, how to calculate gpm for a system, cuz i knew Tr=2.4*gpm, but then i came across a system where the relation was Tr=1.8*gpm.
Please clarify if possible.

3. Professional Member*
Join Date
Aug 2009
Location
Prattville,Alabama
Posts
1,352
"Delta", as used here, simply means "difference", or "differential". So, "delta T" is simply the temperature difference. In this case, the temperature difference of a medium (water or air, for example) as it flows thru a heat exchanger. As you can see, delta T is measured rather than calculated. As far as what it should be, that is best learned by finding the design specifications of the system. Each component in a system was selected to perform a specific function, under specific conditions - or range of conditions. To best determine if those components are operating correctly you need to know the design conditions, then operate the system at those conditions, and measure all parameters while operating at those design conditions. Then compare the measurements with the design specifications.

4. oops

5. Regular Guest
Join Date
Dec 2011
Posts
34
Originally Posted by Nuclrchiller
"Delta", as used here, simply means "difference", or "differential". So, "delta T" is simply the temperature difference. In this case, the temperature difference of a medium (water or air, for example) as it flows thru a heat exchanger. As you can see, delta T is measured rather than calculated. As far as what it should be, that is best learned by finding the design specifications of the system. Each component in a system was selected to perform a specific function, under specific conditions - or range of conditions. To best determine if those components are operating correctly you need to know the design conditions, then operate the system at those conditions, and measure all parameters while operating at those design conditions. Then compare the measurements with the design specifications.
Who is going to select the design specifications?

6. The enginneering department which requires enginnering degrees (pun) which it sounds like you are headed. Sometimes too much info too soon can be dangerous.

Page 2 of 2 First 12

#### Posting Permissions

• You may not post new threads
• You may not post replies
• You may not post attachments
• You may not edit your posts
•

Used Equipment - Buy, Sell, Save!