Author Topic: Developing a Small Steam Plant  (Read 3776 times)

Offline gary.a.ayres

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Re: Developing a Small Steam Plant
« Reply #15 on: October 01, 2019, 10:19:08 PM »
 :cheers:

Offline steam guy willy

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Re: Developing a Small Steam Plant
« Reply #16 on: October 02, 2019, 02:19:47 AM »
Hi, A really interesting project .. :popcorn: :popcorn: :popcorn:

Offline gary.a.ayres

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Re: Developing a Small Steam Plant
« Reply #17 on: October 02, 2019, 10:22:17 AM »
Thank you  :ThumbsUp:

Offline gary.a.ayres

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Re: Developing a Small Steam Plant
« Reply #18 on: October 04, 2019, 09:26:55 PM »
A little bit of progress. Mounting block for pump - aluminium slab sawn and milled square enough and drilled and tapped M3 for the pump base:



And the underside drilled and tapped M6 for screws which will come up through the mounting board:



Steam separator/feedwater heater next...

Offline gary.a.ayres

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Re: Developing a Small Steam Plant
« Reply #19 on: October 05, 2019, 11:52:33 PM »
So... below is my CAD ('Clunky And Dodgy') diagram for the steam separator / feedwater preheater.



I hope it is more or less self-explanatory. Gratitude to MJM 460 for his technical advice, and to other sources found online. This is a bit of a synthesis, with hopefully a few touches of my own as it pans out.

Here are the some of the basic materials (based on 2" diameter copper pipe and fittings) which I acquired today:



All advice welcome. Please feel free to offer any ideas and changes you may have in mind - it's all part of the process...

 :)


Online MJM460

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Re: Developing a Small Steam Plant
« Reply #20 on: October 06, 2019, 10:54:07 AM »
Hi Gary, good to see that the good old back of the envelope still has itís place in modern CAD.

I would suggest that the steam outlet is moved to the top in the centre, with an internal projection down below the inlet.  The idea is that the wet exhaust steam has to start moving downwards, then has to turn back 180 degrees to the outlet.  This change of flow direction helps the separation of the more dense water droplets. 

It is also worth thinking about the detail of the lid.  If those bushes, plus the third one for the outlet are made longer and set in holes in the lid, it is easy to locate them when soldering.  The parts on the inside can be drilled for the ends of the internal tubes, and the outside can be threaded for your pipe connections.  Might need some nut and tail connections or flanges to make it possible to assemble.  You could even make it a flanged lid for maintainability.

How much heat you recover in the feedwater is limited by the exhaust temperature, probably very close to 100 C, and the area of tube in the coil, so wind as much as you can into the coil for more heat transfer area.  I suspect the smallest radius you can bend the tube to will determine how many coils you can fit.

Looking forward to see your interpretation and how it works in practice.

MJM460



The more I learn, the more I find that I still have to learn!

Offline gary.a.ayres

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Re: Developing a Small Steam Plant
« Reply #21 on: October 06, 2019, 10:22:07 PM »
Hi MJM -

Once again, thanks for your input.

Back-of-the-envelope is the future of design, you know.

Decent progress this evening.

I will move the steam outlet to the centre of the lid, as you suggest. I made the basic forms tonight, and had to drill a hole in the centre anyway in order to turn the form I had roughed out by chain drilling:



The hole will do nicely as the basis for the steam outlet. The bushes in my sketch above weren't really a complete idea. I still have to think the connections through, and I'm sure your thoughts above will help.

The main forms are shown here:



The stand will be carved from the aluminium tube, and there will be a layer of insulation between the cylindrical part of the copper vessel and the inside of the stand. The bottom of the stand will be cut away to reveal the cone, and a drain cock of some kind will be inserted into the blanking cap at the end of the right angle. The stand is taller than the separator so the bottom pipe and drain cock will be held above the 'ground'.

The cap has a circular locating groove which was milled into the underside on the rotary table. This will hold the top part of the separator in the correct position when I solder the cap on. The first joint down from the cap will be left as a tight push fit so that it can be taken apart for cleaning, etc. The cap is wider than both the separator and the stand so it will support the separator by sitting on the top of the stand. I reckon a nice little pitch circle of tiny screws fixing the cap to the thick wall of the stand will finish it off nicely at that point   :)

When I get to the preheater coil I'll bear your advice in mind.

So, a bit more drilling and some soldering next...

Cheers   :ThumbsUp:

gary

Offline gary.a.ayres

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Re: Developing a Small Steam Plant
« Reply #22 on: October 07, 2019, 11:07:58 PM »
Now, the cap, hand-fitted together at this point. Following MJM's suggestion, the steam outlet is now via a connector in the centre of the cap with a 1//4 " pipe, the end of which will be inside the separator lower down than the steam inlet, with the other end of the pipe going up the boiler chimney. The two outer connectors will bring water via 3/16" pipe from the pump into the coil and out to the boiler respectively.

The brass of the cap was thick enough to take a thread so I don't think any of these connectors will need to be soldered into the cap. I drilled the middle hole (for a turning mandrel - too big) before I knew I would be putting a pipe connector through it, hence the o-ring. Originally I was thinking of putting some kind of finial or knob on it to close the hole. Given the vessel is open to atmosphere I think the o-ring will be fine. If I get any steam leakage from the other two connectors I'm sure a twist of PTFE tape will fix it.





I can only avoid the torch for so long now...  :Mad:

Online MJM460

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Re: Developing a Small Steam Plant
« Reply #23 on: October 08, 2019, 12:30:29 AM »
Hi Gary, looking really good.

Remember, the vessel will be at atmospheric pressure, so sealing is no too difficult.  The only pressure is in the feedwater pipe, so the tube connections to the coil have to be sealed against the full feed water pressure.

MJM460

The more I learn, the more I find that I still have to learn!

Offline gary.a.ayres

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Re: Developing a Small Steam Plant
« Reply #24 on: October 08, 2019, 08:55:42 AM »
Thanks MJM.

Yes indeed - they will be.

gary

Offline gary.a.ayres

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Re: Developing a Small Steam Plant
« Reply #25 on: October 08, 2019, 09:14:53 AM »
... wind as much as you can into the coil for more heat transfer area.  I suspect the smallest radius you can bend the tube to will determine how many coils you can fit.


MJM - by this do you mean that the pipe should be bent into as many separate coils - parallel to each other,  'clover leaf' style - as will fit into the body of the separator?

I had just envisaged one single coil with as many turns as possible, but am open to ideas. What do you think?

Online MJM460

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Re: Developing a Small Steam Plant
« Reply #26 on: October 08, 2019, 11:02:18 AM »
Hi Gary, I am suggesting one long tube wound in a coil like a spring.  However, as the connections are side by side in the lid, instead of returning straight back to parallel to the inlet, you might be able to just continue winding more turns in a second layer so there is more of the tube wound into the coil to maximise heat transfer area.  Itís a matter of what is practical.

If you look in B and Rís book, you will see how their coils were arranged. 

I strongly recommend against parallel coils where the flow splits into parallel paths.  Even in full size with the greatest care to achieving symmetry of the coils, it is still difficult to get equal flow through each path.

MJM460
The more I learn, the more I find that I still have to learn!

Offline gary.a.ayres

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Re: Developing a Small Steam Plant
« Reply #27 on: October 08, 2019, 12:05:16 PM »
That's great, MJM.

Thank you again for your clear advice and for sharing your knowledge.

Offline doubletop

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Re: Developing a Small Steam Plant
« Reply #28 on: October 08, 2019, 08:58:27 PM »
Gary

I was lookng at your sketch and reflecting on 'dry steam to chimney'. If the condenser does its job there should not be much in the way of dry steam as its temperature will have dropped. It will then be converted to hot water coming out of the drain. That water will have oil in it but if you could work on an oil seperator you could then feed the hot water back to the water tank.

Just thinking.....

Pete
?To achieve anything in this game, you must be prepared to dabble on the boundary of disaster.? - Stirling Moss

Offline ChuckKey

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Re: Developing a Small Steam Plant
« Reply #29 on: October 08, 2019, 09:49:27 PM »
If you make the exhaust steam inlet tangential to the drum rather than radial, you will get something of a cyclone effect, as in Dyson vacuum cleaners, centrifuging out water droplets.