## Hydronic calculations in a system that has a closed supply loop and a closed return loop

## Hydronic calculations in a system that has a closed supply loop and a closed return loop

(OP)

I know the title of this tread is confusing but i can't think of a better way to describe it. I have an existing chilled water system where the piping has been completely looped around an area - both supply and return. The best analogy I can think of is how many compressed air systems come out of the compressor and connect to a rectangular loop as opposed to just teeing off in different directions.

I have a chilled water loop that does the same thing. The supply pipe connects to a rectangular loop, and so does the return line. I still don't think i am explaining it well. Please see attached. There are little supply and return take-offs valves all around the loop for future connection.

My question is how to do the hydronic calculations on this when everything is looped? If the pipes were not looped, I would essentially have 2 parallel branches where the 6" pipes first tee off. Everything is 6" by the way except all the little future valves.

Can I treat it as 2 parallel branches?

I have a chilled water loop that does the same thing. The supply pipe connects to a rectangular loop, and so does the return line. I still don't think i am explaining it well. Please see attached. There are little supply and return take-offs valves all around the loop for future connection.

My question is how to do the hydronic calculations on this when everything is looped? If the pipes were not looped, I would essentially have 2 parallel branches where the 6" pipes first tee off. Everything is 6" by the way except all the little future valves.

Can I treat it as 2 parallel branches?

## RE: Hydronic calculations in a system that has a closed supply loop and a closed return loop

## RE: Hydronic calculations in a system that has a closed supply loop and a closed return loop

That has nothing to do with compressed air network, which is not closed loop system.

## RE: Hydronic calculations in a system that has a closed supply loop and a closed return loop

## RE: Hydronic calculations in a system that has a closed supply loop and a closed return loop

If all AHU chilled water flow control valve are two way, provide a differential pressure control valve between supply and return to pass the minimum allowable flow when the set DP is reached.

You have to make sure you can provide enough gpm for future taps and also allow for the actual delta T across each AHU coil which may not match the chiller delta T. However the net mixed delta T of all should match the chiller delta T.

You can use 2 parallel branch but make sure you get the worst case by trial and error. Make sure you use the worst case branch to AHU pressure drop including coil, control valve, balance valve, isolation valves, strainer, fittings, pipe lengths.

Locate DP sensor to control speed of pump and determine set point.

## RE: Hydronic calculations in a system that has a closed supply loop and a closed return loop

That has nothing to do with compressed air network, which is not closed loop system.

It turns out that it can be done. I never said it was easy though. It requires 69 non-linear equations, plus 26 linear equations for a total of 95 simultaneous equations. You would need a math program like TK Solver or MatLab to do it. Large municipal water and gas utilities do this regularly.

## RE: Hydronic calculations in a system that has a closed supply loop and a closed return loop

using that logic in close-loop system makes no sense at all. not only that it cannot be predicted which path flow will take in different terminal units opening scenarios, but even reverse flow cannot be predicted. that is mess which does not belong to engineering practice.

## RE: Hydronic calculations in a system that has a closed supply loop and a closed return loop

It's not simple.

## RE: Hydronic calculations in a system that has a closed supply loop and a closed return loop