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  1. #1
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    Calculating Pressure Drop on Copper Tube Cooling Coil



    Hello

    I am new to this forum and I have (as you can probably tell) no idea about refrigeration. My question is actually only remotely related as far as I can tell, but I thought you guys might have to calculate pressure drop on copper tubing cooling coils so I'll just try my luck and ask here.

    I am building a prototype tank filled with a fluid. This tank is cooled by a copper cooling coil filled with circulating water. They have done all the calculations, so basically I need to build it and make sure I don't run into a problem with my water pump, water cooling tower etc.

    I wouldn't be too worried if it's just one tank, but I am connecting a couple of them so I definitely need your help.

    What I know is:

    - 10mm copper tubing (seems to be about 3/4")
    - length of tube about 770mm
    - I plan to make a coil with a diameter of around 70mm, so basically I just wrap it around a 1 1/2" steel pipe
    - To get to the 770mm length, I need about 35 rounds
    - (in case that matters: I need a flow rate of about 5 liters/minute and water in temp of 35C)

    Any idea how I calculate the pressure drop for such a cooling coil?

    (Unfortunately I am at a location (in SE Asia) where I don't have any local specialists to talk to.

    Thanks for your help in advance!

    This is how it should look like:
    kuehler.jpg



  2. #2
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    Re: Calculating Pressure Drop on Copper Tube Cooling Coil

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  3. #3
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    Re: Calculating Pressure Drop on Copper Tube Cooling Coil

    Hi Brian,

    thanks for that link. I have read it before and I have read a couple of other pages about calculating pressure drop on copper tubes. But since I am more into electronics I am missing the fundamentals.

    I believe that I can calculate the pressure drop of "normal" copper tubing with the above link or other info I found on the Internet. But how about a coil?

    I do know the total length though. Could I use that? Or should I just use an estimation based on the equivalent length of appropriate 90 elbow fittings?

    PS: I understand that I would be in better hands with a consultant or specialist, but I really have no other choice here where I am. All I need is an estimation, since the coils are the only thing built by myself. The rest (small scale water tower, pump, tubing/distribution) comes from a company so they will need to know the pressure drop and what flow rate I need on my coils.

  4. #4
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    Re: Calculating Pressure Drop on Copper Tube Cooling Coil

    You can see your coil as a straight copper tube.
    It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.

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    Re: Calculating Pressure Drop on Copper Tube Cooling Coil

    Quote Originally Posted by alexhk View Post
    I do know the total length though. Could I use that? Or should I just use an estimation based on the equivalent length of appropriate 90 elbow fittings?
    .
    You would get an approximate loss by calculating the frictional loss by the standard methods and then add losses due to 'formed' bends. The equivelent number of 90 degree bends would be OK if you can find the correct K factor for the curve of your bend. May take a bit of searching to find it.

    Also as you bend it around a mandrill you should consider using the hydraulic diameter and not the preformed diameter as you will get some squashing of the pipe and a small increase in velocity. Even though it is small with the large number of bends it could be significant.

    You may also want to consider having some space between the coils to improve the heat transfer.

    Chef

  6. #6
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    Re: Calculating Pressure Drop on Copper Tube Cooling Coil

    Experimentally. Connect a pump (whose characteristics are known) in a line to your coil and measure (the rate of) the flow and the (pump) head. Compare/confirm the result with the pump diagram.

  7. #7
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    Re: Calculating Pressure Drop on Copper Tube Cooling Coil

    I don't think there's some method available to calculate the pressure drop. If have, the incorrect would be unacceptable. So I recommend you to try a experiment, if you have the necessary equipment, you would get a satisfied result easily.
    Quote Originally Posted by alexhk View Post
    Hello

    I am new to this forum and I have (as you can probably tell) no idea about refrigeration. My question is actually only remotely related as far as I can tell, but I thought you guys might have to calculate pressure drop on copper tubing cooling coils so I'll just try my luck and ask here.

    I am building a prototype tank filled with a fluid. This tank is cooled by a copper cooling coil filled with circulating water. They have done all the calculations, so basically I need to build it and make sure I don't run into a problem with my water pump, water cooling tower etc.

    I wouldn't be too worried if it's just one tank, but I am connecting a couple of them so I definitely need your help.

    What I know is:

    - 10mm copper tubing (seems to be about 3/4")
    - length of tube about 770mm
    - I plan to make a coil with a diameter of around 70mm, so basically I just wrap it around a 1 1/2" steel pipe
    - To get to the 770mm length, I need about 35 rounds
    - (in case that matters: I need a flow rate of about 5 liters/minute and water in temp of 35C)

    Any idea how I calculate the pressure drop for such a cooling coil?

    (Unfortunately I am at a location (in SE Asia) where I don't have any local specialists to talk to.

    Thanks for your help in advance!

    This is how it should look like:
    kuehler.jpg

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