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 Post subject: Re: Economizer tube material
PostPosted: Thu Dec 07, 2017 6:15 pm 
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From this paper https://www.s-k.com/technical-reference ... istics.pdf
we can see that the lbs of steam used per lb of water varies somewhere between 7 and 10.
Since it takes 970 btu/lb to vaporize water, if we assume 10:1 for ease of figuring, every
lb of feed water gets 97 btu just from the heat of vaporization... so we raise the temp.
of the feed water by at least 97 F. This means we're feeding the boiler with 160 F water
assuming feed water is 63 degrees.

<rough estimated calculations ahead>

For a feed water heater, assuming the exhaust steam is 200 F (this could be a lot higher
for single expansion engines w/ high cut-off), we see the effectiveness of the heater
(proportional to temp diff) (200-63)/(200-160) drop by a factor of 3.43. For an
economizer, the results are a bit different; we assume flue gas temps of 500 F:
(500-63)/(500-160) = 1.29, or a 30% drop in effectiveness due to lower delta T.

If efficiency is your goal (otherwise why bother w/ feedwater heaters, economizers, etc ?),
use a mechanical pump, feed water heater + economizer, and use the injector if you
have problems feeding water w/ the mechanical pump. Also, always include a manual
pump, if only to pump water in before getting up steam.

- Bart

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 Post subject: Re: Economizer tube material
PostPosted: Thu Dec 07, 2017 9:48 pm 
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barts wrote:
For an economizer, the results are a bit different; we assume flue gas temps of 500 F:
(500-63)/(500-160) = 1.29, or a 30% drop in effectiveness due to lower delta T.

Here you have calculated effectiveness, and then you proceed to talk about efficiency...

The dictionary says "Being effective is about doing the right things, while being efficient is about doing things right."

I am still absorbing this explanation of the difference and your effectiveness calculation.

barts wrote:
If efficiency is your goal (otherwise why bother w/ feedwater heaters, economizers, etc ?),
use a mechanical pump, feed water heater + economizer, and use the injector if you
have problems feeding water w/ the mechanical pump. Also, always include a manual
pump, if only to pump water in before getting up steam.

And you have just told me how you think a steamboat feedwater setup might be best setup for efficiency that would take a lot of work at this point to change Nyitra to.

I don't think efficiency is exactly my goal. At the end of this summer I was pretty happy with performance of Nyitra and the engine and boiler apart from my only roughly measured baseline of fuel consumption. It was 20lbs hardwood/mile for 14 miles - including fuel to warm up and get the boiler at a reasonable pressure to get underway.

I think Reciproca claims 1lb of hardwood/mile!

Well I know I have tons of heat exhausting up the stack unused, so I thought an economizer would be the way to capture some of that back.

I'd just try to get Nyitra's fuel consumption down, maybe with a goal of like 10-15lbs hardwood mile. That's my goal. I don't know what your folks consumption looks like. And I know there are a lot other factors - such as Nyitra is a much bigger heavier boat then Reciproca.

-CB


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 Post subject: Re: Economizer tube material
PostPosted: Thu Dec 07, 2017 10:14 pm 
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cyberbadger wrote:
barts wrote:
For an economizer, the results are a bit different; we assume flue gas temps of 500 F:
(500-63)/(500-160) = 1.29, or a 30% drop in effectiveness due to lower delta T.

Here you have calculated effectiveness, and then you proceed to talk about efficiency...

The dictionary says "Being effective is about doing the right things, while being efficient is about doing things right."

I am still absorbing this explanation of the difference and your effectiveness calculation.

barts wrote:
If efficiency is your goal (otherwise why bother w/ feedwater heaters, economizers, etc ?),
use a mechanical pump, feed water heater + economizer, and use the injector if you
have problems feeding water w/ the mechanical pump. Also, always include a manual
pump, if only to pump water in before getting up steam.

And you have just told me how you think a steamboat feedwater setup might be best setup for efficiency that would take a lot of work at this point to change Nyitra to.

I don't think efficiency is exactly my goal. At the end of this summer I was pretty happy with performance of Nyitra and the engine and boiler apart from my only roughly measured baseline of fuel consumption. It was 20lbs hardwood/mile for 14 miles - including fuel to warm up and get the boiler at a reasonable pressure to get underway.

I think Reciproca claims 1lb of hardwood/mile!

Well I know I have tons of heat exhausting up the stack unused, so I thought an economizer would be the way to capture some of that back.

I'd just try to get Nyitra's fuel consumption down, maybe with a goal of like 10-15lbs hardwood mile. That's my goal. I don't know what your folks consumption looks like. And I know there are a lot other factors - such as Nyitra is a much bigger heavier boat then Reciproca.

-CB


If you're trying to reduce fuel consumption w/o going slower or reducing weight, you're improving efficiency - making the same amount of power w/ less fuel. When I talk about effectiveness of the feedwater heater, it's all about improving efficiency - one doesn't add them for their looks.

Rainbow (compound, 26', ~4000+ lbs) consumes about 30 lbs/hr doing 5 knots. If I reduce speed, she goes further.

If you want to go the same speed on less fuel, you need to make the plant more efficient. Some suggestions to improve efficiency, in
order of suggested execution:

* add economizer.
* use a mechanical pump rather than injector for normal boiler feed.
* add feedwater heater.

I don't suggest using a feedwater heater w/ a injector; it just won't do much.

- Bart

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 Post subject: Re: Economizer tube material
PostPosted: Thu Dec 07, 2017 10:56 pm 
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In that list where would you put further insulation, I still think I have quite a bit of work doable here. The steamhose I have been using is going away, and it'll be a mix of rigid and the last bit the braided stainless. That hasn't been insulated at all. The engine hasn't been insulated at all either. There are still parts of the boiler that have no cover, or could use more cover. Don't have access to an IR camera, but I would like to see a thermal picture....

Also where would you put tubulators on that list?

-CB


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 Post subject: Re: Economizer tube material
PostPosted: Fri Dec 08, 2017 7:17 am 
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"This is a well thought out explanation, but then why is this configuration then mentioned in the penberthy literature?

Shouldn't the penberthy literature say, don't use an ecomizer it's uselss?"

I don't know, but I think Penberthy literature just might be trying to promote Penberthy injectors?? That would not be the first time that advertisements show strong bias toward their profit motives rather than logical thought. For example, some famous cigarette ads promoting smoking, as recommended by a DOCTOR, WTF!

CB, you have misinterpreted my statement, I never said "its useless" as you seem to imply in your post replying to my explanation here, please go back and read what I actually stated.


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 Post subject: Re: Economizer tube material
PostPosted: Fri Dec 08, 2017 8:21 am 
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Ok. I think I get that an economizer would be good, but not so much with an injector.

And since I'm still not really interested in a mechanical pump, I should just skip it until such time as I am willing to go for a mechanical pump.

I think this a way to think about it that makes sense to me.... With an injector you've already spent the energy to raise the temperature - and you can't undo that, so you've got a smaller differential temperature to gean efficiency.savings from. And in the process make the injector less likely to work in all scenarios.

-CB


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 Post subject: Re: Economizer tube material
PostPosted: Fri Dec 08, 2017 2:47 pm 
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It's your choice Mr C-B, but are you really worried about efficiency in your steam related activities? Yes of course you can get marginal efficiency improvements by doing all sorts of things, but even taken together, they're unlikely to push the thermal efficiency up by more than a few percent. it seems to me anything that increases the complexity of a steam plant also needs more time and money spent on care and maintenance, and indeed may make the plant less reliable. Simplicity has a real value, to some of us at least.


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 Post subject: Re: Economizer tube material
PostPosted: Fri Dec 08, 2017 3:10 pm 
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RGSP wrote:
It's your choice Mr C-B, but are you really worried about efficiency in your steam related activities?

Well the aquisition, processing, and transportation of solid fuel has become a big chore. 300lbs for 4 hrs voyage took me 2-3 hrs to process+ and get on the boat.

It has made me appreciate first hand why the world switched to liquid fuel.

I think your countrymen had a problem with this a few centuries ago running out of trees to chop down... :)

When I started this enterprise, I didn't know I would have to be a plumber/fitter. It's obvious, but I underestimated. Now I realize I have to be a lumberjack.

-CB


Last edited by cyberbadger on Fri Dec 08, 2017 3:30 pm, edited 1 time in total.

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 Post subject: Re: Economizer tube material
PostPosted: Fri Dec 08, 2017 3:29 pm 
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There comes a point where you might consider a long term plan for a more easily driven hull. I would venture a guess that your hull resistance at cruising speed (and thus your fuel consumption) is easily twice that of a typical launch design. Maybe more.

I understand well the needs of compromise and using what you have. My present hull is of startlingly poor materials and the workmanship is embarrassing. It's what came with the machinery. But it is easily driven and I have started a replacement for it. I've been avoiding club events because of the old one. It's hard to navigate with a paper bag over my head.

And I agree that efficiency isn't everything. I will, at some point, give space in my boat to a steam driven feed water pump even though it is of known inefficiency. But I love looking at them run.

Keep the idea of a simple engine driven feed water pump in the back of your mind though. A thing like a Hypro is a bolt on solution. Very high efficiency, No noise. With a hot well float you pretty much forget that it's there. Find someone who repairs coin operated car washes and they may well have a worn out unit that you can freshen up. Bart gave me mine because he was too lazy to rebuild it!

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 Post subject: Re: Economizer tube material
PostPosted: Fri Dec 08, 2017 4:32 pm 
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cyberbadger wrote:

I think your countrymen had a problem with this a few centuries ago running out of trees to chop down... :)

-CB


You should read Oliver Rackham on that topic (sadly, he's now permanently in the crypt of Corpus Christi chapel, as of two years ago). Oliver was a brilliant man in a quiet sort of way, and a superb ecologist, and he (quite rightly) had this thing about factoids.
He defined a factoid as something that somebody had claimed, then after 25 years it was quoted by an historian, and in another 25 years or whatever, a second historian quoted the first one. By that time the original "thing" was accepted by the unthinking majority as fact, regardless of whether it actually made sense when you investigated it thoroughly.

In fact England, Scotland and Wales (I don't know about Ireland) never ever ran out of firewood: the stuff was harvested from short rotation coppices, and iron foundries etc. had vast areas of these, run on an entirely sustainable basis. However, the harvesting and transporting of such wood was expensive (as CB well knows now with Nyitra) and coal was both cheaper and in many cases easier to use. The usage cost of wood was the driver for more coal mining, and the better energy density of coal. English woodlands were and are, almost entirely hardwoods, which in turn are almost impossible to kill by cutting them down - unlike most conifers - and cutting them just stimulates faster growth next year, though they do have to be protected from browsing animals for a year or maybe two.

The suggestion that England was running out of oak trees to build ships is also a factoid, very easily disproved, and it has the interesting sideline that the factoid was started by a very clever (and corrupt) man called John Evelyn in the 17th Century, who bought huge amounts of woodland, and then went to great lengths to talk the prices up. Transport costs on land (similarly to firewood) were the killer for timber costs, and indeed it was often cheaper to import big oak trunks and boards from what is now Poland, transporting by sea through the Baltic, and North Seas, and this is well recorded in the 12th Century for the roof timbers of Ely cathedral, where transporting them, what? 1000 miles? from Danzig (now Gdank) cost less than the horse transport from the quay at Ely, about a mile and 200' uphill.


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