Chilled Water Piping Design

[verdemachina]

I am new to central plant design and need some tips on reference materials to learn about designing chilled water piping runs. Specifically, I am trying to figure out the longest practical pipe run from a central plant that I should consider. If anyone has a good reference or tips I would apreciate it. I am not looking for alot of specific design help, but published references (book,articles,etc.) that may be useful.

Thanks,

Brad

 

[Cooky]

A really good & practical guide is the Carrier Design Manual, this includes information on pipe design.

You may also find my pipe sizing program usefull.

http://pressure_drop2.mysite.freeserve.com/

Cooky

 

[verdemachina]

Thanks for the information Cookie - I apreciate the help!

 

[GBAILEY]

Try:

http://www.bellgossett.com

You will have to register with them to gain access to their "TEH Manuals" but there is everyting you need to get started. As I am new to the HVAC field also they have helped me understand the process and to ask the right follow on questions that come up in practice. Good Luck!

 

[lilliput1]

The limit would be 150 psig for standard steel pipe. Do not configure piping such that this pressure would be exceeded in piping. Note allow say 15% for corrosion so design limit should be .85x150 = 127.5 say 125 psig. Pump head and pipe elevation difference (highest to lowest) and expansion tank pressure at maximum operating temperature should not exceed 125 psig or 289 ft wg head.

 

[VEEKRISH]

The CARRIER System Design Manual is a great starting point. But the longest practical run would be decided by the system needs. You can run your chilled water pipe for miles, long as you've got your Pump Selection right it should not be a problem. In case you really have long lengths, then be sure to factor in the temperature rise from the chiller to the usage point. Insulation of the lines will then need to be designed to ensure minimal gains.

 

[friartuck]

Hi

Drapes here from the UK

You need either the ASHRAE Guide (fundamentals) or the CIBSE Guide book C. These have tabulated flow rate through various types of pipework with x-y coordinates of pipe size, flow rate, pressure drop, velocity. These use the D'Arcy and Colebrook and White equations.

In the UK we dont tend to have the large chilled water distribution systems that you might have in for instance the USA, however there will be practical limits based on for instance standard available pipe size. In the UK we can get hold of 150 and 200mm dia pipe. Any larger and its special order. A 150mm pipe could carry 36l/sec of water at a pressure drop of 250Pa/m. This would equate to about 900kW of cooling with a 6 degree celcius temp drop.(i.e. 6-12 flow and return.)

Financial restraints would possibly limit the size of chiller plant, pipework and insulation costs. We don't have many systems above this sort of capability, and probably we would tend to de-centralise to control the practicalities of such systems.

In the UK with the advent of VRV(variable refrigerant volume inverter driven compresser systems), we would decentralise and make use of the ability of the systems to provide heat recovery from areas requiring cooling to those requiring heating. I believe these systems are scarce in the USA probably due to the much warmer climate and reduced need for heating???

See DAIKIN or MITSUBISHI air conditioning foe more info on this type of system.

 

[imok2]

Brad, this may give you more insight

http://www.semiconductorfabtech.com/journals/edition.09/download/ft09-03_03.pdf

 

[lilliput1]

Note velocity limits also. In occupied areas, limit velocity to 6 FPS to avoid noise. For operating hours of 2000 per year, limit velocity to about 11.6 FPS. For operating hours of 5000 per year, limit velocity to 8.6 FPS to minimize pipe erossion. Maximum velocity at pump suction should be 8 FPS.