High pressure drop between distribution pump and heat exchanger
High pressure drop between distribution pump and heat exchanger
(OP)
Good day,
Im having a problem on a chilled water distribution line going to a air handling unit cooling coil.
Data is this
Distribution pump capacity is 120m3/h and head of 85m and with a distribution pipe of 100mm
Chilled Water Pressure/Temperature in distribution pump is 9barg abd 3degC respectively
The two air handling unit has chilled water distribution and return pipe of 50mm
The two air handling unit is approx 12 meters above the distribution pump
Total length of distribution pipe is 100meter approx
Scenario:
IF return isolation valve of chilled water out of Air Handling Unit cooling coil, pressure is about 8 barg
IF return isolation valve of chilled water out of Air Handling Unit cooling coil, pressure is about 1.5 barg only
Does this effect the flow rate, heat transfer and velocity of chilled water passing thru the air handling unit?
Im having a problem on a chilled water distribution line going to a air handling unit cooling coil.
Data is this
Distribution pump capacity is 120m3/h and head of 85m and with a distribution pipe of 100mm
Chilled Water Pressure/Temperature in distribution pump is 9barg abd 3degC respectively
The two air handling unit has chilled water distribution and return pipe of 50mm
The two air handling unit is approx 12 meters above the distribution pump
Total length of distribution pipe is 100meter approx
Scenario:
IF return isolation valve of chilled water out of Air Handling Unit cooling coil, pressure is about 8 barg
IF return isolation valve of chilled water out of Air Handling Unit cooling coil, pressure is about 1.5 barg only
Does this effect the flow rate, heat transfer and velocity of chilled water passing thru the air handling unit?





RE: High pressure drop between distribution pump and heat exchanger
Is this homework?
RE: High pressure drop between distribution pump and heat exchanger
I know that pressure and flow are related, and i know that flow and heat transfer are related. What I want to validate is why there is a large pressure drop between distribution pump and cooling coil of AHU? is this possible because pressure is dropped from 9barg to 1.5barg?
Additional info, chilled water buffer tank is an open tank.
RE: High pressure drop between distribution pump and heat exchanger
Where are these pressures measured? - Note you say the same IF thing twice identically - did you mean to put an "open" or "Closed" in those sentences?
There will be a large pressure drop because your pump is probably capable of supplying much more than 120m3/hr because the system design will let it do so.
If you supply 10% of the information anyone else needs to understand your system you will only get 10% of the answer...
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: High pressure drop between distribution pump and heat exchanger
Sorry, i will re-phrase my data
Data is this
Distribution pump capacity is 120m3/h and head of 85m and with a distribution pipe of 100mm
Chilled Water Pressure/Temperature in distribution pump is 9barg abd 3degC respectively
The two air handling unit has chilled water distribution and return pipe of 50mm tapped to 100mm distribution pipe header
The two air handling unit is approx 12 meters above the distribution pump
Total length of distribution pipe is 100meter approx
Scenario:
IF return isolation valve of chilled water out of Air Handling Unit cooling coil closed, pressure is about 8 barg read by gauge installed in in and out of AHU cooling coil
IF return isolation valve of chilled water out of Air Handling Unit cooling coil opened, pressure is about 1.5 barg only read by gauge installed in in and out of AHU cooling coil
Pipe is 100mm ID (pipes are measured on their ID not on their OD)
Pipe is Schedule 40
Pipe is Carbon Steel (is there a relation between pressure drop and pipe material used)??
thanks
RE: High pressure drop between distribution pump and heat exchanger
TTFN

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RE: High pressure drop between distribution pump and heat exchanger
Hence I think you have a lot more chilled water running through our AHU's which means they can provide more cold air if the air fans can handle it or more likely they provide more or less the same amount of cold air, but your chilled water pump is consuming more power than it needs to and fluid velocities are too high.
BTW, steel pipes are normally sized as a nominal OD (100 or 4" in this case) as this doesn't change, but wall thickness and ID do for the same Nominal size pipe. Also PE and other plastic pipes are much smoother and have lower resistance to flow hence why I asked the question.
What exactly is your question??
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: High pressure drop between distribution pump and heat exchanger
Thats what i want to know, if that large pressure drop indicates a high flow of my chilled water into the cooling coil. We try to throttle the return valve of chilled water and inlet/outlet pressure begins to rise, from this throttling, do my flow rate increase versus from fully opened valve?
Thanks
RE: High pressure drop between distribution pump and heat exchanger
However if your flow rate is higher than the AHU can actually handle, there should be no difference in the amount of cooling as the limitation would be the area of the coils and the amount of air that the AHU fan can push past it.
Think of this like a conveyor belt where a person takes one orange every 10 seconds to pack into a bag. He can't take any more any faster. If you speed up the conveyor belt so that there are 2 oranges going past him every 10 seconds, he can still only take one and the speeding up of the conveyor belt is not helping you and wasting a lot of oranges. Similarly a higher flow through your AHU than the AHU can handle has no impact on the cooling, but may be damaging your pump and also using more power to move more water for no benefit.
If you actually measure flows in these lines with a UT meter or some other device, you will then have some data to compare it to, but otherwise this is all conjecture and guesswork, enjoyable as it is.
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: High pressure drop between distribution pump and heat exchanger
TTFN

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Need help writing a question or understanding a reply? forum1529: Translation Assistance for Engineers
RE: High pressure drop between distribution pump and heat exchanger
RE: High pressure drop between distribution pump and heat exchanger
You need to take a course in thermodynamics and fluid mechanics.
RE: High pressure drop between distribution pump and heat exchanger
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: High pressure drop between distribution pump and heat exchanger
RE: High pressure drop between distribution pump and heat exchanger
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: High pressure drop between distribution pump and heat exchanger
Just a tad high...
RE: High pressure drop between distribution pump and heat exchanger
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way