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Heat pipe sizing

if I am running supply and return piping for something that requires 1” and it is tying into a boiler that only has 1/2” tappings, how can I still het the flow rate I need? I would think once you drop down to 1/2” you can only get however many GPM through that 1” pipe as you can get through the 1/2” pipe. Kind of like if you take a 4 lane highway, close it down to one lane, then open it back up to four lanes. You are only going to get as many cars through that can fit through the one lane section. I’m being told by an engineer to do something that seems to me like it can’t work. I know I’m probably wrong but I can’t understand how it can work.


  • pecmsgpecmsg Posts: 1,127Member
    What boiler only has 1/2" tapping's?
  • GrallertGrallert Posts: 386Member
    pecmsg said:

    What boiler only has 1/2" tapping's?

    That's a good question.
    What about primary secondary piping?
  • JBFBMechJBFBMech Posts: 20Member
    It’s not a boiler it’s a tank. I was just trying to simplify the question. I didn’t want to get it to explaining the whole job. I just want to know how it is possible to reduce the size of the pipe where it ties in and get any more flow through the pipe than you would the smaller pipe size. It seems like if you run a 1” pipe that is tied into a 1/2” tapping then why not just run 1/2” it’s going to get restricted at the 1/2” tie in anyway.
  • pecmsgpecmsg Posts: 1,127Member
    So you have a tank with 1/2" fittings.....

    Is this tank designed for the application AKA ASME Stamped?
  • ronron Posts: 141Member
    JBFBMech said:

    how can I still get the flow rate I need?

    just like with enough thrust pigs can fly, with enough pressure you can get the [mass] flow rate you need through any size pipe.

    taking a guess at your situation which u did not fully describe, doing 1/2" everywhere with the mindset there's at least one 1/2" somewhere which is the weakest link why not do 1/2" everywhere then... it depends on the system.

    greater total resistance to flow would result in needing more pumping pressure to get a given desired amount of flow in the system... with velocity being the thing that changes the most at various points (smaller diameter higher velocity, larger diameter lower velocity).

    You are only going to get as many cars through that can fit through the one lane section.

    not a good analogy since the cars don't behave exactly like a fluid although many people today drive that way (any opening take it). but there are some good animations on the web showing auto traffic jams and rubbernecking and the similarities to fluid mechanics and standing waves... you would get as many cars if velocity and density increases (which is doesn't because of relative speed limit and cars not colliding, water/gas/fluid will pressurize and heat up with density changing).

    doesn't take into acount increased [mass] flow but u can see the changes in velocity and density... apply this to any fluid in a pipe:

  • JBFBMechJBFBMech Posts: 20Member
    Thank you Ron.
  • mattmia2mattmia2 Posts: 847Member
    You stand a good chance of getting the flow rate in the 1/2" section in the area where noise and erosion become problems. You really should either increase your delta t so you an reduce your flow or find a tank with large enough tappings.
  • mattmia2mattmia2 Posts: 847Member
    Either that or the larger size was just to keep the head matched to the pump and short 1/2" sections might not be a problem. Isn't there an idronics that explains this.
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