GPM design to maintain 2-4 feet per second

Rich_49

They are all nice additions to a heat exchanger , or other device meant to transfer heat energy Bob . None of them would ever probably be placed in supply and return piping though in my opinion .

hot_rod

My previous statement:
Low velocity will inhibit air removal especially in vertical down flowing lines. Under low flow conditions the water flowing down is not always sufficient to push the air along with it. Air rises up through the flow of water and traps in high points. Noise is also often associated with inadequate flow velocity in regards to air elimination.

Our testing shows below 2 fps the air is not always adequately entrained with the fluid stream. In vertical piping the air will rise and trap at high points. In the original question it was suggested 6 gpm in 1-1/2 steel piping may be possible. That could make air removal tough.

I suggest IF there is any high point in that piping add some float type air vents.

If air is trapped up top from the original fill it doesn't matter how good of a separator you have back at the boiler, the air ain't gonna get there.

Most quality hydronic manifolds have float air vents on the supply and return header knowing that they may be installed at the highest point in the building, maybe a upper floor closet. The float vents work in conjunction with a central air separator.

We test our seps at 4 fps in the lab and within 90 minutes you should have 90% plus of all the air removed that flows thru it.

Glycol may take much longer, a tough fluid to de-aerate

Gordy

Rich said:

There ya go , fluid / tube / fluid . Reynolds numbers apply . Let's not get lost though debating the same old stuff .. The Ops question was about slow flows in mains , not emitters . Let's also not forget that we got here talking about air removal , which can be done efficiently and effectively with lower flow rates in the portion of the system where we do not particularly want heat transfer .

i asked a question awhile back .

What entity wrote this ?

" ________ air separators continuously remove entrained air in hydronic systems with very high separation efficiency . the amount of air removed from a system varies depending on fluid velocity and temperature , as illustrated in the graph below , at 4. feet per second fluid velocity , all air artificially introduced into the circuit is eliminated by the ____________ air separator .

Any small amount which remains is then gradually eliminated during normal system operation . In conditions where the fluid velocity is SLOWER or the temperature of the fluid is higher , the amount of air separated is even GREATER "

Anybody care to take a stab at filling in the blanks or which entity made this statement ?

Caleffi

hot_rod

Rich said:

They are all nice additions to a heat exchanger , or other device meant to transfer heat energy Bob . None of them would ever probably be placed in supply and return piping though in my opinion .

I'm not sure anyone would put them in S&R piping?

Rich_49

Amazing Bob . I have been discussing the difference between S&R piping and mains along with the same for horizontal and vertical portions of systems . I have also been trying to make the point about eliminating air at different points in a system and maximizing air removal so it becomes a non issue and flows can be only what they need be .

Gordy .
Yes , it is Caleffi and the blanks would be filled in with Discal .

If systems get designed well , installed well , and purged properly at all pertinent points using high temp fluid unless there is a leak air becomes a non issue and fluid may be circulated throughout without issue increasing system efficiency not limited to fuel usage , electric usage . Comfort will be maximized also for the largest portion of the season . Not a theory , fact . Get rid of air and quit chasing things that will annoy and inhibit performance .

hot_rod

Sounds like we agree, I would add the systems should also be designed around the lowest possible supply temperatures, to get best efficiency.

Proper load calc and design, absolute air removal, lowest SWT, ECM technology, insulation on distribution piping in un-heated spaces, all contribute to top performing systems.

Mark Eatherton

When it comes to Reynolds numbers, I think back to the days of gravity flow, large open waterway cast iron radiators and boilers, and wonder to myself how the heck these things even worked.

Then, fast forward to today, and I look at the fire tube heat exchangers with their wide open water ways, and extremely low relative fluid velocity, and the tank within a tank design (Triangle Tube) DHW generators and again, wonder to myself how things work with low Reynolds numbers, and go "HMMmmmm..."

Me thinks the world is not solely dependent upon Reynolds numbers to work...

https://en.wikipedia.org/wiki/Reynolds_number

ME

HomerJSmith

Designing a system is like "love", it's complicated. So many factors need to be taken into consideration.

Manufacturers crunch the math and do the product testing. They hire plumbing engineers, those are guys who don't have girl friends and who enjoy that sort of thing.

The manufacturers put out a cook book and the installers in the field just follow the recipe. Some installers can't read very well, or worse, can't take direction and end up with a bad installation.
Understanding of sound piping principles and basic relational knowledge between components leads to a good installation.

Designing a system to be productive must follow the Economic principle of EROEI, Energy Returned On Energy Invested. This is intuitive. Judo, the Japanese art of grappling, has a motto, "Maximum efficiency, minimum effort". It is saying the same thing. The goal of system design is exactly that, maximizing the efficiency of the system while minimizing the operating cost over the life of the system.

EROEI, says that the installation costs + operating costs must be less than than the value of the heat produced. If not the project is abandoned and if produced is not produced again.

System design is complicated, balancing costs against return.

The comments are off topic, but reading your thoughts have been enjoyable. Damn, I gotta get a girlfriend.

jumper

It's well known that two way valves can close enough on chilled water systems so that flow becomes laminar and heat transfer decreases too much.

hot_rod

jumper said:

It's well known that two way valves can close enough on chilled water systems so that flow becomes laminar and heat transfer decreases too much.

Correct, chilled water systems are more flow sensitive. The mean water and mean air temperature are much closer than heating systems. A good application for pressure independent balance valves, along with ZV in the coil kits.

Paul48

It's easier to tell the boss...The flow is laminar, that's the problem. The reality is.....He's an idiot, and closed the valve too much. Baffling them with Bull.......

McSteamer22

Hey guys I have just read the entire post, sorry about the delay, after a few days I thought that’s all I would get. Everything is gold, the charts and perspective. Thanks for your time