No Header, No Equalizer, No Problem!

Love the videos and the empirical experimentation approach to answering questions. I'm still not sure how one tells the difference between say 3% vs 5% water content steam without expensive direct measurements of the steam or a very controlled measurement of total condensate return. Perhaps it doesn't matter but that is another question.

Just to throw a minor spanner in the works… from the thermodynamic point of view… it is worth remembering in all of this that we are dealing with saturated steam. Among other things, that means that if we consider a packet of steam wandering around in a pipe and look at it, anything — anything! — which removes energy from it will cause some of the vapour phase to condense to the liquid phase. This results in very small droplets of liquid phase water in the steam. This is not wet steam, just saturated. Does our friendly packet of steam have less ability to deliver heat now than it did when it started? Yes — since some of the heat energy has been lost to whatever removed the heat from the packet. Is this a problem? No, not really — althugh naturally one wants to reduce those losses.

Now if there are macro size water droplets in there, or enough condensation has occurred along the way so that the micro droplets have started to coalesce to the point where they drop out of the stream, that might be regarded as "wet" steam.. Will those macro droplets cause a problem? Again, not really unless they finally get big enough to fall out of suspension — and even then not really unless they make a puddle or otherwise obstruct flow (unless we are looking at steam turbines, where they cause blade erosion — but that's another matter)(or there is enough to cause hydrolocking in a piston engine!).

None of this is the same as carryover…

Not sure if any of it is relevant, either. Back to your cave, old man.

I see something in that sight glass that cries out wet steam rather than normal condensation, especially at the high velocity of 39.4 fps (28 MPH), and a mixture of steam and liquid droplets is still defined as Saturated Steam so we have to differ there. There is an internal mistiness or fogginess that can only be entrained fine water droplets. What we see on the interior of the glass (much lower thermal conductivity than steel or iron in typical fittings neglecting thickness) is some of these micro droplets impinging on the surface and coalescing. The ones that are small enough will be propelled upwards along the surface due to the high velocity. The ones that manage to coalesce into a large enough droplet will succumb to gravity and fall downwards on the surface even with that high velocity. Condensation would be very minimal at this high velocity and with the lower thermal conductivity of glass and the low dwell time and the high internal temperature of the glass. If you want to see what that looks like, then look at ethicalpaul's other videos where the velocity is extremely low at 9.2 fps (6.3 MPH) with his Peerless 63-03L boiler (their smallest) and overbuilt double takeoff with drop header. That would have much lower dwell time and lower internal temperature of the glass, which would be even more condensation and you see very little. The velocity trumps the higher heating ability of, say 100% dryness fraction vs 95% dryness fraction, due to the effect of the convective heat transfer coefficient (h in Heat Transfer textbooks). Sorry, this started out simpler than this, and got excessively detailed. None of this is simple is it? As you say often…..oh well…..

Lets keep the drama out of this ok? Just man to man polite discussion. PM's should be private. I'm not sure what the forum rules are on something like this. I actually said that I initially thought you must be yanking all of our chains but I'm almost 100% certain that isn't the case now but that I have been advised by others who have tried before me that I was wasting my time. I can respond to Jamie's post can't I?

By all means let what you have said stand and I will do the same. That's keeping things civil and we are just discussing the physics of steam and it isn't something to get upset about, right?

Just curious

@ethicalpaul

@Jamie Hall

@Captain Who

May I ask what you do for a living? I seem to recall Jamie being a mechanical engineer, and I think Paul is a programmer but I do not recall what type?

With his 1.25" (pretty sure that is what he said in the video) pipe wouldn't the riser velocity be 52ft/s with a 233sqft boiler rating? Still within manufacturers guidelines for some of the bigger boilers.

OK so there appears to be a disconnect between engineering and field language on wet steam and dry steam. That is fair to want to finesse from a communication standpoint. But I think what @ethicalpaul is calling carryover is what I have, perhaps carelessly from a technical standpoint, referred to as wet steam.

now some of these sightglass experiments have demonstrated this slugging relative to water quality and this slugging is the single most significant problem I have faced over the years. and the one thing I will say about header design vs. water quality (limiting it to those two variables pro-tem) is that what we all would prefer is not a header that handles the slugging/carryover but no slugging/carryover.

So when I commissioned a Williamson GSA-125 this year, I skimmed multiple times. The thing purred along making a half pound, looked great after couple hours. I go home and in the morning get the call that the boiler went off on low water and they refilled and one of the air valves had bad threads and when he touched it it fell off and water was pouring out of the radiator and the gauge was showing 3 to 4 pounds. (pressuretrols seem basically useless to me, I had it set for 2 which was effectively its low end, i'm forever trying to find controls that work in vapor region but with the exception of the old mercury ones haven't been successful . . .). But what I realized is I don't really want the boiler to go up to 1 or 2 lbs or even 1/2 pound and then shutoff for a while and then do it again. And why was a boiler that I left humming happily at l/2 lbs. running up like that and then it would carry water.

This boiler had only one 3" tapping for outlet and although the system main was 2" I didn't bush down right away, trying to keep the velocity at the boiler exit lower. And after coming 2 feet up from the boiler i reduced to 2" and continued the rise higher than the main and then created a drop to an existing tee on the vertical under the main which is where the boiler piping from the previous boiler had been connected and the bottom of the vertical tee was a 1 and 1/4 drain/return/equalizer which i piped with two elbows to the low boiler connection (no hartford loop because there was no wet return). Think you can see this in the picture. In what is presented as ideal drop header design, the tee run would have been run on the flat and continued horizontally to the drop but otherwise I thought I pretty much conformed to the spirit of the drop header and the tee was existing and where I ended my new piping. But, as described, I was plagued by slugging no matter how much skimming, soaking with tsp draining and new water i did.

In either scenario, this is principally a counterflow main and once the system is full of steam it does have to handle all the condensation from all rads and that will drop through the tee while steam is flowing the other way. This seems to me a no brainer case for a parallel flow main design which i tend to see in larger buildings or more well thought out smaller ones; but telling someone to redo all their feed piping is a lot different than suggesting improved near boiler piping. I'm always dealing, as most of us, with mains and rads installed by the deadmen–be they magicians or madmen–and so taking that part of the system as a given not subject to much change.

While I could imagine this counterflow being a bit of a problem creating a turbulent interface between steam and condensate, it still did not explain to me why pressure was increasing and slugging was transpiring. I would have loved for a good deal of the piping to be transparent so I could watch what was happening but one bit of the artistry of steam is you kind of have to infer that stuff although i have made experiments like @ethicalpaul adding transparent portions to steam systems; but i haven't figured out how to make a transparent piping system through the entirety of the relevant near boiler and main entries. maybe someone will make polycarbonate threaded fittings or something that could actually sustain this use, at least for a term of testing and design.

as others have noted, this seems to be especially problematic with new boilers and when i asked why the manufacturers can't just clean the oil out after tapping and threading, etc. the answer I got was a preference for some oil coating that kept rust down on the interior surfaces while the boiler was awaiting distribution and installation. forgetting that i'm not really sure that there is any careful universal dispersion of these oils in boiler to give uniform anticorrosive protection, I'm busy being careful not to get assembly fluids and pastes into the system but its going to come with its own built in headaches. I don't imagine that any relevant amount of rust other than aesthetic is at issue but maybe I'm wrong. wouldn't be the first time and won't be the last. and it does occur to me that rust loose in the water could have some impact on these water carrying phenomenon. maybe this is back to water treatments that can precipitate or dissolve or encapsulate whatever the various contaminants are and then they can be drained away?

As those following this saga in my other novellas in various threads you'll find that my answer wasn't water quality beyond the TSP cleaning and skimming, it was firing rate. I lowered the firing rate to where it effectively balanced the condensing rate (slow pickup obviously) and the thing has been running perfectly. So that is another variable on operational stability and boiler water carryover that i would enter into the mix besides header design and water quality. to the extent that lower firing rate makes less steam in a given period of time I think that has to lower velocity.

finally, on the contentions that seem to be one predominate thread of debate here over where the btus go and thus efficiency implications of careful header construction that i thought was more aimed at preventing water carryover into the mains (which the test here leaves me unsure how much is actually being carried. certainly no apparent slugs rich in liquid water although enough moving w steam to knock it off on low water–not surprising with today's small boilers where the low water control almost becomes a regular operational control in addition to safety, and gets me very nervous about the idea of automatic feed for small boilers). I don't disagree with the basic premise that if the same btus are absorbed by the water in the boiler that they go into the house although there is the question of where in the house: near the boiler, boiler piping, rads? Also I would think you would need to monitor combustion efficiency, esp. thinking stack temperature, to the extent that any phenomenon associated with piping may limit btu transfer, e.g. lower boiler water line while operating or manner of boiling phenomenon may mean less heat transfer? Also there is some question in my mind of kinetic energy involved in pushing water and whether that phenomenon actually consumes btus in some manner although i would accept in general the logic that they went somewhere so maybe overthinking it.

@ethicalpaul — I quite agree with what you are saying (or what I think you are saying) — high velocity doesn't "suck" water out of the boiler. However, we do find people complaining about steam velocity making a difference and creating "wet" steam. Ah… well… go back and lok around somewhere in the murk I wrote up there. To get the velocity — and move the steam at all — you need to reduce the pressure. But — when you reduce the pressure in saturated steam you get condensation to microdrops. Reduce it enough you get coalescence to macrodrops. Splurk…

Paul's pressure was low as evidenced by his in. of H20 pressure gauge. What higher velocity does is it allows entrained water droplets that have coalesced in a range of sizes up to a larger size to be propelled from the close proximity of the exit and sustaining that movement up a vertical pipe without gravity being able to defeat that.

PS: And I should add that therefore the higher the velocity, the more visible and more foggy in appearance these potentially larger entrained droplets will be (and the wetter the steam) even through a narrower sight glass makes the width of the column of two phase mixture that you are "looking through" less.

Ah — but the condensation which occurs and makes the microdrops form itself means that that much latent heat energy is no longer available to appear when the remaining water vapour condenses where you want it!

I should add that the droplets to which I refer are way too small to see with the naked eye — but they will appear as a slight increase in the opacity ("fogginess") of the steam — which with a path length of only a few inches you are not going to notice.

Go out to an airport on a very high humidity day. Very high. And watch something of size take off — a 777 or C-17, for instance. As soon as they rotate and the wings start to lift, you will see a definite cloud form on the top of the wing, and if yuo are really lucky you will see it in the vortices at the wingtips. That's from the condensation of the watervapour in the air with the velocity and pressure changes as the wing makes llift.

Any steam leaving a boiler at 39 fps is too wet to be efficiently operating a low pressure steam heating system. If I specified government work like that, I wouldn't be paid — or licensed.

Short answer is that every extra minute that the boiler has to run to satisfy the thermostat in the living space, the more energy is lost up the flue and through the jacket and pipes to the basement (slab, walls, windows, etc.). Dan mentioned in his article that wetter steam has less energy due to less latent heat being available with the liquid water portion only having sensible heat, which is far far less than latent heat. I think people are just bored with this being questioned still to be honest with you, and no matter how many times it is answered there is still someone who will claim that no BTUs are lost. They can pay the gas or oil bill then.

I didn't need to quote Dan, although I like to 🤣. It's known that "dry" steam has a higher enthalpy than "wet" steam and the more wet it is the less the enthalpy. Also, wet steam has a higher pressure drop across the main, which Dan mentioned in his article also. All this means that the heat transferred to the room through the radiator will be less per unit time. Boiler runs longer to satisfy thermostat.