Author Topic: Monotube Boiler  (Read 34629 times)

Offline mattinker

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Re: Monotube Boiler
« Reply #50 on: August 06, 2014, 02:14:39 AM »
A copper tube with water in it cannot heat to red heat. Have you ever tried to braze a copper plumbing installation with even the slightest amount of water in it? You just can't do it. It must be empty.

Regards, Matthew.

Offline vtsteam

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Re: Monotube Boiler
« Reply #51 on: August 06, 2014, 07:40:08 AM »
I'm not sure what you mean Matt by the "slightest bit of water in it". Flash boiler tubes routinely carry both water at the inlet and steam at the outlet, and may glow red along the superheated steam portion. This is commonly reported in operation.

My question was, whether there was circulation in this copper coil or something closer to vapor lock, and therefore poor circulation. I believe, but will have to check again, that only part of the coil was glowing. Which would suggest circulation and flashing into steam along its length. If all coils in the flame were red, I'd suspect a lock.

Yes I have soldered pipes before and pipes do need to be dry near the joint. I built and plumbed my house, and complete hydronic heating system including a wood furnace with copper heat exchangers and copper piping throughout.
I love it when a Plan B comes together!
Steve
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Offline mattinker

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Re: Monotube Boiler
« Reply #52 on: August 06, 2014, 04:14:02 PM »
Hi Steve,

 Well I was kinda thinking out loud this morning going out the door on my way to a job. I was pretty sure that you'd experienced the amount of energy to needed to keep a copper pipe dry whilst you braze it, it's enormous, red heat being of the order of 750C is a huge amount of energy. In a small circuit, mostly filled with water, the pressure rise would be very fast, I would have thought that if it was circulating, the pressure would have gone up rapidly above 20 psi, I may well be wrong, (probably!) but I would have though you had a vaper lock!

Regards, Matthew

Offline vtsteam

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Re: Monotube Boiler
« Reply #53 on: August 06, 2014, 06:39:52 PM »
I lean toward that too, Matt, though thinking about it, it seems like even then it would have to "refresh" itself since it's below the main body and steam would be leaving it up through the body.

It couldn't drop in pressure too low before at least a little water re-entered it to build it back up. But maybe not a steady flow.

I'd like to work with it and see how good a flow can be achieved. And try different shapes. That's easy to do because the coil attaches with two flare nuts, so I can just change it out for another. This is kind of a nice design for experimenting with -- everything is screwed together and replaceable.

This has a classic helical horizontal coil of 4 turns (I believe), per the magazine article plans. I'm wondering if a straight pipe might not work better because of increased circulation, even though it has less area. I wouldn't be surprised if that were true.

 I've seen them  angle down gradually from the attach point at one end, and then sweep back up rapidly at the other. Probably what I'll try next.
I love it when a Plan B comes together!
Steve
www.sredmond.com

Offline mcflin

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Re: Monotube Boiler
« Reply #54 on: September 29, 2014, 04:29:36 PM »
This is the project I have been working on for many years ,a mono-tube boiler running on LPG and reaches 120 psi in 30 odd seconds,it still has bugs to iron out,but learning so much. ( hope the picture comes through )
« Last Edit: September 29, 2014, 09:42:58 PM by dsquire »

Offline S. Heslop

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Re: Monotube Boiler
« Reply #55 on: September 29, 2014, 04:53:37 PM »
This is the project I have been working on for many years ,a mono-tube boiler running on LPG and reaches 120 psi in 30 odd seconds,it still has bugs to iron out,but learning so much. ( hope the picture comes through )

That's fantastic! Got any more details?

A steam powered bike has been a pipe dream of mine for a while. Seems like it'd be a real challenge.

Offline tom osselton

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Re: Monotube Boiler
« Reply #56 on: September 29, 2014, 05:41:34 PM »
A steam powered bike would be cool!

Offline doubleboost

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Re: Monotube Boiler
« Reply #57 on: September 29, 2014, 05:42:34 PM »
You have my attention

Offline mcflin

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Re: Monotube Boiler
« Reply #58 on: September 29, 2014, 05:56:08 PM »
Here is a YouTube of some test runs

     


Its 1 1/2'' bore.a microprocessor measures and controls the water,which is pumped in from a coffee machine pump at up to 180 psi.But over the next 2 weeks am redesigning the burner and boiler.is all very difficult as there is no one in NZ to ask advice as not many people get to control a mono-tube boiler satisfactory
regards lyn

« Last Edit: September 29, 2014, 09:32:18 PM by dsquire »

Offline S. Heslop

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Re: Monotube Boiler
« Reply #59 on: September 29, 2014, 06:27:39 PM »
Great video. I feel like i've already trawled everything the internet had to offer on steam bikes, so it's great to see more.

You'll probably get sick of hearing this question, but I have to ask; what kind of range do you get/ expect to get with it?

Offline mcflin

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Re: Monotube Boiler
« Reply #60 on: September 30, 2014, 05:03:47 AM »
In the video the exhaust steam goes to atmosphere.where as it is normanly fed back to the water tank through a internal condenser .this gives more water to use,the tank is approx 6 lts and this determined the range.but the whole project is just a folly anyway .I just use it on our local cycleways of which we have 186 km of of road cycle paths in our area.

Offline awemawson

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Re: Monotube Boiler
« Reply #61 on: September 30, 2014, 07:09:07 AM »
"The whole project is just a folly"


No - I love it - superb style and I bet it was great fun getting it to the stage that you have. Inundate us with details please  :ddb:
Andrew Mawson
East Sussex

Offline Arbalist

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Re: Monotube Boiler
« Reply #62 on: September 30, 2014, 10:50:34 AM »
That is completely bonkers Lynn, I love it!   :clap: let's see some more when you've done the mods, and welcome to the forum!

Offline JohnHaine

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Re: Monotube Boiler
« Reply #63 on: September 30, 2014, 06:34:50 PM »
There is useful information on design and control of monotube boilers in the SBA magazine Funnel.  It may be accessible on the web, do a search in google on Funnel monotube and there are a couple of links.  I have a fairly complete set but they are a bit inaccessible.  If you are interested and can't find them on line I could have a hunt...