head Loss Calculation

[Acro-Phobia]

I'm trying to pick a new pump for my system and the head loss calculator doesn't have what I need to ask. So here is the question.

I want to come off a main line with 3 outlets. Two in the main tank and one in the frag tank. Each vertical pipe will be about 4' high. When I do the head loss calculation, do I figure a 4' vertical component or do I have to add all three for a 12' vertical component?

 

[MplsMan]

here you go
http://reefcentral.com/calc/hlc2.php

 

[Acro-Phobia]

That's the calculator that doesn't answer the question. If you are pushing water up 3 four foot pipes that are all the same height, do you use a 4' vertical input or do you have to add them for a 12 foot vertical input.

 

[OliverM3]

This would be interesting to find out.

I would think it would be the total of all vertical pipes bringing you to 12'.

 

[AMENO]

it should be just the 4ft vertical. Because you are still pushing the same amount of volume thru your pump as you would if it were just one line. The volume and vilosity is also a consideration in head loss.

 

[AZDesertRat]

It would be one 4' vertical loss except you also need to consider the size of pipe and number of fittings. Its not quite black and white. For instance if you are using three 3/4" or 1" pipes it would not be equal to one 2" pipe so there would be a slight amount of loss. You will also have more fittings with three outlets so you need to figure in a slight amount of loss there to. I wouldn't think it would amount to more than another foot or two though.

 

[jmait769]

I’m no engineer but I believe you would add up all vertical pipes as one due to fluid friction in the pipe. You input pipe size not water volume in the calculator. I guess if you added up the pipe diameter then input that? So three 1” diameter pipes running vertical would be one 3” diameter pipe? Or I could be completely wrong!

Jay

 

[AZDesertRat]

Thats not quite true. It would take 10 one inch pipes to equal a single 3 inch pipe. The surface area of a 1" pipe is .785 square inches, the surface area of a 3" pipe is 7 square inches. A 2 inch pipe is equal to four 1 inch pipes.

 

[Acro-Phobia]

Thanks guys. I did find a link which provided all the formulas for figuring head loss across multiple inline outlets. My brain got tired just looking at it.

I think I agree with the 4' loss and also with the additional losses for downstream outlets due to pressure loss after each outlet. I think I'll end up going with the old tried and true. Get a Big A__ pump with more flow than I can possibly use and T vavle the exits to adjust the flow as required.

 

[AMENO]

thats true AZ it's not black and white there are a lot a factors, such as pipe sizes and turns. I was assuming his piping was staying in the rage needed for the volume he's running. It is a combination of water volume, pipe size and other restrictions that could be in the line, such as valves, elbows ect. An example lets say a 2" pump discharge. Normal you want to run around 7.5 feet per sec. on velosity. That would be around 80 GPM or 4800 GPH.
if you take that down to (3) 1" lines they would be running at around 20 GPM a total of 60 GPM, not big enough and would increase the head loss due to friction. Now if he's using 1.5" lines they could run 48 GPM at 7.5 FPS. which is a lot more then whats needed and not contribute to head loss.

 

[Acro-Phobia]

What I'm actually trying to do is run 2 tank return line and one line to a frag tank. The pump I want to use is a Sequence Barracuda with an output of 4600 gph (1.5" outlet). I want to run a 1.5" trunk line and tap off of it for the 3 output lines. The main tank lines will be 3/4" (AGA Megaflow outlets) each having to rise about 4' above the pump. One line will have a chiller in the line. The frag tank will be at the end of the trunk line and tapped off with a 1" riser, again about 4' above the pump height. I want to get at least 700 gph per line. Think I can do it with the Barracuda?

 

[AZDesertRat]

7.5 ft sec. is a pretty high velocity, I would try to keep it in the 3.5 ft sec. range like in a potable water system. Less resistance to flow due to C factor etc.

 

[AZDesertRat]

700 GPH is pushing it for a 3/4" line but you can probably come close. It will take a little balancing with ball or gate valves but once you have it dialed in it should work.

 

[AMENO]

The barracuda is a big bad pump I don't think you will have any problem getting a total of 2100 gph out of it. your 3/4" lines will run about 780 gph and your 1" will run around 1200 gph. The 1" is plenty big enough but with any restrictions such as elbows or tees you may be pushing it on the 3/4". If you could I would run all three at 1" and then if your chiller needs 3/4," reduce at the chiller, same for at the tank. You won't lose much flow that way. And if needed you can use valves to restrict the flows to were you want them.

 

[AMENO]

actually 7.5 FPS is a pretty standard flow for most applications. Thats what most industry standards shoot for in sizing pipe. The rate coming out of this barracuda is around 12.6 FPS.
Not trying to butt heads just what we always try to design around
I'm sure potable water systems have there own standards.

 

[Acro-Phobia]

I have to stay with the 3/4 inch lines because that's the size holes drilled for the megaflow overflows in an AGA 125 gal tank. The only big flow restriction area will be going to the chiller and back to the tank. I was running each of my tank lines with Mag 9.5's. When I put the chiller in that side it dropped it down to probably 250-300 gph. That, and adding the frag tank, is why I'm upgrading to one big pump.

 

[AMENO]

Ok, I was wondering what kind of restriction the chiller would have. I don't have one and not that familiar with them.
But what you might could do is run 1" to your tank and then add a bushing there at the tank bulkhead to bushing down to 3/4".
Same on the chiller, you will get a lot more volume that way.
Don't know if thats do able for your set up or not but it would make a big difference in flow.

 

[Acro-Phobia]

Humm, gives me an idea. I can run a 1" line off the main trunk line to the chiller and then a 3/4" line back to the main tank. That would help the flow for that line by staying as large as possible until I have to drop down to the 3/4" size.

It was explained to me that inside the chiller, your line is subdivided into many small lines so that heat exchange can be maximized thru many lines. Lots of little elbows and skinny lines inside the chiller takes it's toll on flow. The benefit, if there is one, is the slower the water flows thru the chiller, the more heat exchange you get unless you start flowing less than the minimum flow rate for the chiller. Then you're just wasting time.

 

[AMENO]

sounds right we deal with very large chillers and heat exchangers here and thats probably the sample principle that the smaller chillers work on. That would help to run 1" to the chiller, sounds like a good plan.:thumbsup: