Monotube Javelin

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TriangleTom
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Re: Monotube Javelin

Post by TriangleTom » Mon Aug 23, 2021 5:14 pm

Beautiful work!

I don't know why but I always love seeing hulls converted to run on steam.
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Re: Monotube Javelin

Post by cyberbadger » Fri Oct 01, 2021 5:16 pm

fredrosse wrote:
Mon Jul 26, 2021 5:07 pm
Very crowded arrangement under the forward deck, containing Generating Coil, 120VAC Oil Burner, 12VDC-120VAC inverter, fuel supply and return hose, with large filter, letdown heat exchanger coil, (40 feet of tubing), burner pressure switch, letdown overboard discharge valves, separator thermodynamic steam trap to backup letdown flow, feedwater flow lines,one direct into generating coil, other thru the letdown heat exchanger, stainless flex connection from generating coil to separator pressure vessel. Small electric diaphragm pump, with manifold allowing lake water boost into feedwater pumps, or alternately can be valved as a bulge pump. Crowded but still easier to work on than the engine compartment of a modern automobile.
Do you have a piping and instrumentation diagram (P&ID) or process flow diagram (PFD) for Javelin's steam plant?

For example, how letdown coil, generating coil, separator, steam trap, etc work together.

What are the mechanisms that affect the control, or is it all manual valves?

-CB
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fredrosse
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Re: Monotube Javelin

Post by fredrosse » Sun Oct 17, 2021 6:14 pm

Monotube named Mara, sorted out fairly well for the October Meet.
Made 7 MPH with the oil burner nozzle of 1.5 US Gallons per hour, 150 PSIG Steam.
Next step, increase to 3 GPH, up the pressure to 250 PSIG
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fredrosse
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Re: Monotube Javelin

Post by fredrosse » Sun Oct 17, 2021 6:23 pm

Coming in for lunch
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RNoe
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Re: Monotube Javelin

Post by RNoe » Mon Oct 18, 2021 2:44 am

Sure looks good.
And makes me anxious to get my Steam Thistle on the waters again. She's not yet fully "sorted out."

Until my wife regains some mobility I am home-care bound.
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fredrosse
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Re: Monotube Javelin

Post by fredrosse » Mon Oct 18, 2021 3:38 am

A brief (and approximate) description of the system. Please note that this is a basic description of the cycle with several design features left with no details, to avoid over complicating within this thread. Controls, interlocks, and safety features are also not detailed here. This is just a description of the basics.

Steam flow is 100 pounds per hour, (PPH) this is the design basis.

1. Feedwater pump (electric driven) delivers 200 PPH cold feed (lake water) to the letdown counterflow heat exchanger.
2. Feedwater is heated to about 200F in this letdown heat exchanger.
3. The heated feedwater then enters generating coils (oil fired) where 100 PPH of the water is turned into steam, 360F, and this two phase mixture (50% steam 50% liquid water) exits the oil fired coil.
4. A large fraction of liquid water provides protection of the coil from overheating, which is often the downfall of monotube steam generators. This is because the heat transfer coefficient of boiling water far far exceeds the rather low heat transfer coefficient of superheated steam, by a factor of over 100:1 in this case. The liquid water keeps the coil metal temperature close to the boiling temperature, peak tube metal temperature is around 370F.
5. The two-phase mixture then enters the separator vessel, saturated steam flows upward and enters the main steam pipe, flows thru the engine and produces power, then exhausts to atmosphere.
6. The separated water falls to the bottom of the separator, where it flows thru the "letdown" outlet. This 360F hot water then flows thru the counterflow heat exchanger, and heats the incoming pumped feedwater. The letdown flow is cooled to about 120F, and discharged overboard. The letdown flow is manually controlled.
7. A thermodynamic steam trap is also connected to the separator vessel, slightly higher than the letdown connection. This assures that the separator vessel will not become flooded if letdown flow is not enough.

The steam/water mixture enters the separator at about 100 MPH, and that level of turbulence can significantly impede proper separation of the steam and water. This requires separator internals that can properly quell the violent turbulence here, keep water out of the steam outlet pipe, withstand the pressure spikes, resist the significant forces involved, and assure a reasonable maintenance of a water level in the bottom of the separator vessel for the letdown and trap connections.

Additional features are required to provide a safe and reliable system, and proper engineering is required for several aspects of the design. Therefore, it is recommended that attempts to cobble together a similar system not be attempted unless proper detailed engineering, as well as operating procedures, are provided.
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Re: Monotube Javelin

Post by cyberbadger » Mon Oct 18, 2021 2:06 pm

Fred,

Thanks for all the info!
fredrosse wrote:
Mon Oct 18, 2021 3:38 am
4. A large fraction of liquid water provides protection of the coil from overheating, which is often the downfall of monotube steam generators. This is because the heat transfer coefficient of boiling water far far exceeds the rather low heat transfer coefficient of superheated steam, by a factor of over 100:1 in this case. The liquid water keeps the coil metal temperature close to the boiling temperature, peak tube metal temperature is around 370F.
I have seen more then a few people attempt a steam plant with a monotube on youtube.
They often seem to think monotube = boiler, but it's really only one part of steam plant which requires just a few more parts... :D

From what I've seen the resulting steam mixture is very wet at best with just a monotube.

Your launch is several leagues above those kind of attempts with the fancy separator and quite a few more parts to really separate out the water.

When you do a cursory google search on "letdown heat exchanger" most of the results are about very large and complicated nuclear reactors.

-CB
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fredrosse
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Re: Monotube Javelin

Post by fredrosse » Tue Oct 19, 2021 3:46 pm

"...........about very large and complicated nuclear reactors."

That is where I spent most of my engineering work from the late 1960s till a few years ago, I guess some of it rubbed off.
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Re: Monotube Javelin

Post by cyberbadger » Tue Oct 19, 2021 10:59 pm

fredrosse wrote:
Tue Oct 19, 2021 3:46 pm
"...........about very large and complicated nuclear reactors."

That is where I spent most of my engineering work from the late 1960s till a few years ago, I guess some of it rubbed off.
I have asked others jokingly that I just need a plutonium insert for my boiler.

I have learned that what I want would be a "small" nuclear pilot light.

Such things apparently exist, albeit obviously heavily regulated, a point heat source that would completely cover the BTU requirements of my 6HP plant

I could just drop it down into the lake when not in use. :)

-CB
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fredrosse
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Re: Monotube Javelin

Post by fredrosse » Wed Oct 20, 2021 2:42 am

Early satellites used SNAP generators were sent into space to generate electricity with a thermopile generator. Same as the thermopile generators that control typical gas fired pilot lights in a water heater. No moving parts, just a bunch of series connected thermocouples.

In the water heater, the heat source is the pilot light, in the SNAP generators Plutonium heat source was used.

You are correct, your chunk of Plutonium would give off nearly constant heat power (fairly long "half life"), and Plutonium only gives off Alpha radiation, which can be stopped by ordinary paper. None of those troublesome gamma rays that are so penetrating of thick lead shielding that nobody could get close to a gamma source.

However Plutonium is considered one of the most deadly poisons in existence, and if you didn't keep it continuously cooled, it will melt, then vaporize, then get inhaled by living organisms, with dire consequences. If not reliably encapsulated, some of it will diffuse into the environment without melting, but it is only dangerous for around 100,000 years, so why worry? (Not). Fortunately you are not allowed to have any of the stuff. Unfortunately, several governments can make the stuff, and think that they can adequately safeguard against its dangers.

The SNAP generators produced power only in the several Watt range. It is my understanding that the space shuttle uses Hydrogen/Oxygen fuel cells to produce much more power, and efficient power, available at a cost of only $600,000 per kilowatt for the fuel cell.
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