Spinning around angles/turns will create this turbulence, call it an effect like what happens with the weather with warm/cold fronts.

Having high pressure hot steam may create a microcosm of this effect.

Mr. Day,

You are far too kind to me and the work that we do. Thank you for your comments. We will be sharing more photos as time goes on. The firebox was completed today and will be installed in the first boiler by the end of the week.

In respect to turbulence. In discussions like this I enjoy placing myself in the shoes of the designers, in say, 1920. In this case, man is hardly flying, to say nothing about flying well. Turbulence was not even studied as a real thing until about 1940 (as far as I can tell). So to think that a team of designers sat in a room and talked about a word that they knew nothing about, nor was even studied at the time is unrealistic.

What is realistic and what was discussed was $$$$$, tons pulled, hours spent to maintain and the most gain for $$$$ spent. When you consider this, you can imagine the designers in a room saying to themselves; "How do we cut $50 more dollars out of this locomotive, but still make it pull _____ Tons of freight?" A hand raises in the back....."ummm.....sir, if we cut out two feet of superheater units, the end result would be a loss of ______ degrees of superheat, but would be a savings of $50.00 in material alone." The boss replies; "Great job, Chap....with that it is lunch time. Better yet, let's all go home for the day!"

I believe that the reality is: Volume of steam in must be equal to volume of steam out. Any increase in Temperature not exceeding the limits of the lubrication.......WINNER. It is really that easy. Thus again, I tend to lean toward Mr. Day as what he is saying accomplishes both and possibly produces a longer lasting unit, which is less money to maintain, which is that $50.00 that we are all looking for anyway.

I suggest that if one wants to use modern technology/terms to determine what designers did in 1920...they should study first if the technology even existed at that time before suggesting that it was a consideration of the designers. I think we just ruled out turbulence as a considered point for the times.

Last, I believe that the only consideration in return bend design was length of life alone! The more material you place in a return bend end cap wall....potentially the longer the life......maybe?

Kindly,

I'm so glad I'm following this thread the mod-recommended way:

http://spoluzaci.im.cz/document/243/243627-f0c.mp3

John Rimmash wrote,

”I believe that the reality is: Volume of steam in must be equal to volume of steam out. Any increase in Temperature not exceeding the limits of the lubrication.......WINNER.”
I have to ask did you consider Charles Law or Boyles Law when you wrote this? I realize steam has some non ideal properties due to its polar molecule but it follows the basic principles of gases particularly when it is superheated.

When I was at GCR I took a picture of the cylinder chest back pressure gauge on 4960 reading 180 psi cylinder chest and 10 psi back pressure. The throttle was wide open and we were holding 40 mph. The boiler pressure was between 195 and 200 psi. The pressure loss was not due to a leak but due to the flow rate out of the boiler and the usage rate of the steam by the running gear. If a locomotive is stationary the full boiler pressure can be exerted on the locomotive pistons because the pressures will equalize but if motion begins to occur, there is a constant gas flow due to the motion of the valves and pistons. A pressure gradient will develop and there will be both a pressure drop and volumetric expansion in the superheater that can be measured by the relative velocities of the steam into and out of the superheater.

In my sophomore level transport class Dr. Fisher stated that most flow problems were turbulent. And it is amazing the number of things in human history that he could not explain in the ways we are able to today but we used the same basic technique both then and now. John it may surprise you but in many parts of the world behavior of materials were taken advantage of even if they were not understood.


The probable reason for the short superheater unit is the fastest way to repair a leak is to take it out if you do not have replacement material. Many people did not have the resources many American and Canadian railroads did. In the end you improvise because you have to not because your making money but because you have no other choice than to improvise.

Robby Peartree

BTW if you take a super heater unit out of the top row and one out of the bottom row and put the header connection next to each other the other ends will not be next to one another.

Consider the watchmakers of yesteryear with all the intricate gears and parts.
Superheaters is an invention, early engines did not have them.
The persue to push the power of the steam engine kept on peaked after the WW2.
It was certainly thought of, tried and tested. Having helped on 765, you also have to
know these huge engines are designed down to clockwork precision, thousandths of an inch measures. That seal in the cylinders better be good or leaked steam kills power.

cheers.

Ummmmmmmm.........OK, leaving that last bit of semiliterate drivel out of it, the whole picture of power VS consumption of volumes of steam is far more complex (and apparently easily misunderstood than I had imagined). Volumetric changes of steam also vary the pressure and temperature - or, all affect each other reciprocally to be more precise. So, the same volume into the cylinders as out......well, then no work would have been done, would there? Unless you were talking about the superheater elements themselves, not the cylinders, in which no useful work is designed to be done. Of course, you can academically play with density by maintaining the volume while removing the heat until it reaches critical energy and collapses into itself as condensation, but not in a real engine, thank you. We get enough accidental condensation as it is.

The small portion of the heat of the fire that actually performs useful work at the wheel on rail is also just a small portion of the technical whole, in its complex and myriad construction. It isn't enlightening to consider only a part of it without the entirety of what it is as a system - for instance, Nigel and his dead-on viewpoint about the critical limiting factor in useful heat transfer in the superheaters being the lubricant. Steam flow can be choked in the throttle, drypipe, superheater elements, cored passages in the steam chest / cylinder castings, and in the exhaust system. Greater flow in the superheater means nothing if there's an exhaust choke at the other end of the motion. Neither matter if the throttle chokes the superheater to begin with. DESIGN IT AS A WHOLE SYSTEM!

Look at EVERYTHING and how it works together as a whole if you want to understand any piece of it seperately - otherwise you will find yourself obsessing about useless trivia and learning a lot of facts but no wisdom.

dave

You talk of turbulence from the return bends, just think of driving a twisting narrow mountain road in a convoy. Its the last thing you want. The Renolds number Mr Austin talks about shows that even the smallest uneven surface has a major efect to create turbulence for heat exchangers. More a bit later but the principles of hot rodding an internal combustion engine apply to steam locos.

I belive that although the efects of boundry layer and Renold numbers where first understood in the 19th century they where never applied to the steam locomitve properly right up to the comercial end of steam. Even today the art of airo dynamics is still being mastered. Material technology is the same, almost as soon as its written down its out of date! Move on, let the steam locomotive catch up with the world.

I loved my time with the big GCR locos and some moments stand out as awesome. I watched with Mr Lanter when Mr Hadder did a standing start with 4960. It was wonderful watching it take off very rapidly sitting back on its drivers with a crisp beet and masively improved breathing. This was the efect of removing the turbulence from the blast pipe with the use of De Lavel nozzles in the Lempor. Back pressure had fallen down to 4 to 6 psi in the conditions Mr Peartree talks off and a maximum of 12Psi. Turbulence for the sake of it? You lose more than you gain. No there are better ways.

There is one thing that I have never hidden about myself. When I make a mistake, I will take 100% credit for it. I am no more perfect than anybody else. Thank you all for the PM's and other kind notes on this thread. Too often, we take what is written and we strive to over interpret what is being said or suggested. Often times, less if more:

Turbulence:

My Library has mostly been copied and placed on discs that I use to study questions and or us to help customers or others with questions. When I type the word Turbulence into a search in the records that I have scanned and recorded, I do not find the word ever mentioned nor even considered. It has been rubbed in my face that indeed, the study of turbulence pre-dates superheater units. I am very sorry for the oversight! At the same time, I guess I could have been more clear in the fact that my library does not contain mention of it......more so, there is no mention of it in respect to superheater units.

Volume:

What I trying to suggest in my "comment" on volume could have been put better. Here is my second try: If volume OUT is anything less than volume IN, then we would have an issue. When considering the heat/pressure increase in a superheater unit, indeed, the total volume out would be more than the total volume of heat/pressure going in. As such, indeed, if we have a number of units that were plugged or had failed for any given reason, we could still have a total exit volume GREATER than that going INTO the units. It is my hope that this clarifies my comment and again, I am sorry for not being more clear on my stated opinion.

It has been suggested to me that reading comments on a thread is best done and best understood only after any comment is read three times. In fact, it was a good friend of mine that suggested that until you have read anything more than three times, you have failed to understand the real meaning. I so appreciate the comments on these threads and I am sorry if I have miss-read, miss-commented, or miss-understood any of the posts above. Rather than picking on "words said", I strive to understand the general meaning and intention of the poster, understanding that the written word can often be easily miss-understood.

May the conversation continue in peace.

Always yours,

JohnE.

Dear Mr. Day

I hate to disappoint you but running 12 psi back pressure on GCR 4960 was pretty rare. Most times at MP 48 where we were at our slowest going up the climb to Apex/Imbleau locomotive 4960 with near maximum tonnage usually slugged out 10psi back pressure with a wide open throttle holding 8 to 10 mph. GCR 18 would push 12 psi back pressure with the same speed range near tonnage. Remember the power reverse on a locomotive sometimes does not give you the exact ratio you want and you have to get as close as you can given the current conditions you face. It is true the back pressure has changed with the Lempor but it should be noted that 4960 has always been a slippery locomotive due to its low factor of adhesion. The trip southbound I spent running ahead of 4960 with the sand scoop for sanding flues and used it to carry sand to sand the rails between MP 11.5 and 11 and then back into the cab for another scoop full because we were slipping wildly and were afraid of stopping I will never forget! We figured if we had stopped we would never have gotten restarted.

On the subject of turbulence the reason for the Lempor to reach supersonic speeds is for the turbulence created. When steam is flowing through the super heaters the steam flow is already turbulent due to many factors including flow rate and header design but I will argue that this is good for heat transfer as the steam is mixed allowing better heat transfer in this situation.

Materials are not changing as fast as you would like. Many steam locomotives are not using out of date material technology it is just that manufacturing is make what the industries of today want.

Robby Peartree

I have found one of the relivent articals on super heaters and have posted it here.

Page2

We're hear to learn and get it right and to teach, all in all a good thing.

as a note, 765's steam pick is not at the steam dome but way up near the firebox, where the steam, water is hotter.

The main problem with this talk of laminar vs. turbulent flow, Reynolds numbers and the like is summed up right here:

"The nature of flow in pipe, by the work of Osborne Reynolds, is depending on the pipe diameter, the density and viscosity of the flowing fluid and the velocity of the flow."

For any given design, the flow may be laminar, transient, or turbulent, depending on the velocity of the steam. To the good fortune of the early steam designers, the harder an engine works, the more likely the flow is to be turbulent, with it's greater capacity for heat transfer.. To actually try to design for turbulent flow, however, one would need to change things that are not particularly easy to change, such as the diameter of the tube used as the superheater unit. Changing this, however, is likely to have more effect due to the change in heating surface than the characteristic of the flow.

At this stage in the game, superheaters are what they are. If you need maximum steam production, make the units longer, and live with the increased maintenance costs. If maintenance costs are the problem, make them shorter, and live with the reduced superheat.

Or, going back to the discussion last month, train the crews to drift with the throttle open, so they don't burn the ends off the units.