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  1. #1
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    Jul 2007
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    Sizing chiller piping

    I have a company that wants to cool a 16' x 30" x 40" tank of water to 90degF. The engineer came up with 30 tons of cooling necessary to do this and wants a 40 ton chiller.
    My question is how do I size the length of piping that is going to be needed to pick up 40 tons of heat.
    60 GPM
    2 1/2" pipe
    44 SWT
    Are there manuals for this or is there a calculation that I need.
    I tried some different math for this but it keeps giving me different numbers.
    The piping is going to come out of the chiller and lay in the tank but chiller water and process water will be separate.
    Thanks
    If at first you don't succeed; charge, charge, charge again.

  2. #2
    Join Date
    Jan 2005
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    Area 51
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    984
    http://www.stanref.com/custom.htm

    Could you use a heat exchanger to chill the water and just put a supply and return from the heat exchanger into the tank, otherwise you would have to try and find out the heat tranfer rate per foot of the type of pipe you are using. Standard Refrigeration could help you with this custom design problem.
    "Paddle faster, I hear banjo music"

  3. #3
    Join Date
    Feb 2004
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    New Mexico
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    5,455
    I'd ask the engineer. It's his design why stick your neck out. He's the guy with numbers.
    Tracers work both ways.

  4. #4
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    Apparently I am the engineer.
    I am going with the heat exchanger idea.
    I called standard refrigeration but I must have talked to the wrong person because he was not helpful and unwilling to work with me at all. So I called Armstrong pumps and they helped me out.

    Just because the tank is open and lying on the ground doesn't mean I have to use a positive displacement pump does it? I think of sump pumps. The guy from Armstrong mentioned it.
    If at first you don't succeed; charge, charge, charge again.

  5. #5
    Join Date
    Jul 2008
    Location
    Washington, DC
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    Quote Originally Posted by mech_head View Post
    Just because the tank is open and lying on the ground doesn't mean I have to use a positive displacement pump does it? I think of sump pumps. The guy from Armstrong mentioned it.
    If you are installing a closed loop that runs through the tank you will need to have your compresion tank, releief valve and make up system, etc. I don't see why a centrifagul pump won't work in this case.
    Last edited by Pneuma; 08-08-2008 at 01:02 PM. Reason: misread original post

  6. #6
    Join Date
    Mar 2003
    Posts
    7,321
    I do goofy projects similair to this a lot for industrial applications. you need to figure your heat transfer coeficient for what ever pipe you are using. You need to figure your delta t for the process loop and your flow rate to size the piping and the pump. Dont really see why you would need positive displacement though. The only issue I have is that piping does not transfer heat as well as say a plate and frame exchanger. You may be able to foffer a better solution with smaller piping by adding a second pump and heat exchanger. Imagine just how much piping you would need to submerse in the vessel to geive up that many BTUh's

  7. #7
    Join Date
    Oct 2006
    Location
    Emerald Coast, FL 30.1N 85.8W
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    681

    wrong site

    as a licensed PE and HVACR contractor, asking that question in a technician forum is like asking a monkey to do the breaststroke.

    Technicians aren't qualified to answer the question.

    For ambitious techs, that piping question can be answered researching ASHRAE Fundamentals, Applications, & Refrigeration manuals.

  8. #8
    Join Date
    Feb 2008
    Posts
    24
    Quote Originally Posted by emcoasthvacr View Post
    as a licensed PE and HVACR contractor, asking that question in a technician forum is like asking a monkey to do the breaststroke.

    Technicians aren't qualified to answer the question.

    For ambitious techs, that piping question can be answered researching ASHRAE Fundamentals, Applications, & Refrigeration manuals.
    This was a rather rude response.
    A talented technician may have a good idea to share to help the OP.
    Besides, the OP didn't direct the question only to technicians, engineers are members too.

  9. #9
    Join Date
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    Western Wa
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    1,817
    I'm reminded of the story of an engineer in a baloon...
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  10. #10
    Join Date
    May 2001
    Location
    Western Wa
    Posts
    1,817
    Google "plate frame heat exchanger calculator"

    There's some out there that let you plug your data in and play around to get a ballpark idea of how much you would need to run through both sides of the heat exchanger. Like with a variable speed pump.
    God Bless our Veterans

    God Bless the USA

  11. #11
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    Ontario Canada
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    Quote Originally Posted by Pneuma View Post
    If you are installing a closed loop that runs through the tank you will need to have your compresion tank, releief valve and make up system, etc. I don't see why a centrifagul pump won't work in this case.

    Sorry, I must have not made myself clear enough. I am going to go with the heat exchanger idea. THe chilled water will go through one side and the process water the other. There will be minimal if any piping in the process tank which will be open to atmosphere. That is why the question about the centrifugal pump came up. Hope this clears things up.
    If at first you don't succeed; charge, charge, charge again.

  12. #12
    Join Date
    Mar 2006
    Location
    Pasadena, California
    Posts
    114

    chiller piping

    The question is, You need to cool 133.33 cubic ft of water from 90 f to 44 f.
    Delta T 46 f
    To determine the tonnage ,
    heat required to raise 1lb of water 1 degree f = 1 btu.
    1 cubic ft = 7.481 gallons
    1 gal = 8.345 lbs

    133.33 x 7.481 X 8.345 x 46 T = 382887.95 btu/12000 = 31.9 tons.

    Now, if you want the chilled and process loop separated you need a plate heat exchanger . Also keep in mind the minium loop volume on the chilled water line. 6 gallon x 40 = 240 gal. If the loop is a short run use a buffer tank. Follow the chiller manufactures max/min flow rates.( Average 3 gpm/ton) and piping requirements. ( Carrier, York , Mc Quay, Trane )

    Primary loop - Chiller, pump, 240Gal buffer tank, expansion tank and heat exchanger
    Process loop- Pump, heat exchanger , 3 way mixing valve and controls.

    If you want 44 f on the process loop you may need to go lower on the chilled water loop. Might need to run brine .

  13. #13
    Join Date
    Mar 2003
    Posts
    7,321
    depending upon pump placement you may or may not be able to use a centrif. Determine your flow requirements, and look at location of pump suction piping. Will this location allow you enough NPSH to operate the pump correctly? Szinig the heat exchanger is also not a big deal as already stated, but to get to your desired temp you must consider two things, run a lower chilled water temp, or use a larger plate and frame to get to a lower approach of say two degrees. Each has its own advantage.

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