Delta T for Ahu, Chiller and district cooling systems

[mohsinrkhan86]

Hi all..Can anyone please explain me the concept of delta T & what delta T shall be considered for Chillers, Ahu & district cooling systems?
And how it shall be calculated and considered?

Regards

[Chris_Worthington]

Thread relocated to AOP

[mohsinrkhan86]

Thread relocated to AOP

What is AOP?

[beenthere]

What is AOP?

Ask Our Pros.

[Catherin]

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[mohsinrkhan86]

District cooling systems can replace any type of air conditioning system, but primarily compete with air-cooled reciprocating chiller systems serving large buildings which consume large amounts of electricity.

But what are delta T values for different systems to consider?

[Catherin]

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[mohsinrkhan86]

A delta-T is the change in temperature of a single substance or flow of substance. The evaporator delta-T is the temperature difference between the air entering the coil and the air leaving the coil.

Yeah i know what delta T is. But i heard that there are pre-specified values of delta T for different types of systems like ahu, chiller etc

[Catherin]

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[rscamaro]

Yeah i know what delta T is. But i heard that there are pre-specified values of delta T for different types of systems like ahu, chiller etc

Yes, there are specific Delta T parameters that are engineered into any given equipment.

I've seen reach in coolers designed for 5 degrees delta for a specific purpose. I've seen chillers run from 10 to 20 degrees delta T, as well as air handlers. you will have to research each individual piece of equipment to find what the design Delta T is soposed to be.

...Ron

[beenthere]

Catherin, this is the Ask Our Pro's forum, and only Pro members that have been vetted by the AOPC may post advise here. Please apply to the AOPC today, thank you.

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[mohsinrkhan86]

Yes, there are specific Delta T parameters that are engineered into any given equipment.

I've seen reach in coolers designed for 5 degrees delta for a specific purpose. I've seen chillers run from 10 to 20 degrees delta T, as well as air handlers. you will have to research each individual piece of equipment to find what the design Delta T is soposed to be.

...Ron

Thanx rscamaro for your response.
Another doubt, more the delta T value, better is the system. Is it true?

[jpsmith1cm]

Thanx rscamaro for your response.
Another doubt, more the delta T value, better is the system. Is it true?

Not necessarily.

[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.

[mohsinrkhan86]

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.

[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.

[duckman373]

oops

[mohsinrkhan86]

"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?

[toocoolforschool]

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