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Author Topic: My Heater  (Read 5355 times)

jbartlett323

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My Heater
« on: February 27, 2015, 03:41:04 pm »
Been lurking here for a couple of seasons, thought I'd add my info and help this community grow!  ;)

3 seasons ago, my step-dad and I built a MEN style Heater out of a stubby 30 gal (I think) electric water heater and other various parts laying around.  It has gone through many iterations and is still evolving, but more on that later!

This guy lives in my shop, and puts out massive heat!  One of my major goals with this was to have a system that was completely functional without any outside stimuli, AKA electricity.  So we opted for a basic drip system with gravity feed.  This has worked well, although it does present some other issues.  But, if the power is ever out for extended periods, as long as I got fuel, I'm warm!
It runs on both Motor Oil and Veggie Oil, depending what valve I open.  I have a small oven thermometer on the outside that registers a max of 500F, and its trivial to make the needle go totally buried!  8)

So after dealing with what looks to be basic issues with this guy, I have learned a lot, but haven't figured it all out.  Of course fuel delivery remains one of the biggest issues.  One of my other big issues that I have solved: the Soot and the Cleaning!
Before one of the more recent evolutions, we would have black snow flakes most of the time we were burning.  We knew this was because the fuel wasn't burning completely, but based on the system, we were doing everything right.  We would try to adjust our fuel, and it would cool too much (it really likes to keep temps up.  If we are not at Full Operating Temperature, it isn't happy), so we try to adjust the air in various ways, but could never get a good burn that way.
We took a step back.  Thinking harder, we decided that our biggest problem was the style of manifold.  We had built a Sanders-style manifold, but without buying the book or using any plans.  Basically, looking at pictures and making one.  It worked, and it worked as advertised.  Including the issues, such as hard startup, massive soot, constant cleaning, and regular clogging.
Most manifolds I have seen for non-forced-air systems rely on one of 2 methods: 1. Create a pool of fuel, heat and burn (basic plate method) or 2. Hit top plate, run/gas to small combustion chamber (middle), heat and burn.  We took both these principles into account in design, and added the idea that the more hot metal it hits, the more spread out it will be, therefor heating, gassing and burning faster and more thoroughly.  By taking 1/2" re-bar and forming grid-layers of triangles, enclosing a couple of the larger spaces to create a small combustion chamber, we created a manifold with lots of surface area yet enough space for the oil to spread and gas.  Looks a little odd but....
It has worked out perfectly!  We now have little to no soot, I haven't cleaned it in 5+ burns, its still clean every time I look at it, so its burning EVERYTHING.  Start-up literally requires dumping ~1 cup kerosene down the intake and dropping a match down it (actually, I use kerosene soaked q-tips, cause I have a ton).  Takes a bout 20-30min to get to FOT, even at 5F ambient.  It burns consistent every time I use it (not so with old manifold). 

I still have 1 big issue I haven't worked out yet though, and that's fuel efficiency.  When we built this, we were under the impression that it should burn ~1qt/hr.  Our reality is almost 1gal/hr.  Seems a bit steep to me, but that's one of the reason I'm here, to ask what kind of rates everyone else gets, and if anyone has any idea why it eats that much.

The pics below are kinda old, I need to take some fresh ones.  We have re-arranged the fuel lines, and found a better air-cone location since these were taken, so excuse the bit of soot left on the manifold as these were taken right before one of the last times it was cleaned.  I will take some new ones soon and get em posted.

Russ

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Re: My Heater
« Reply #1 on: March 03, 2015, 05:49:14 pm »
Welcome jbartlett323!

Good to hear that you went from a lurker to a member.  Thanks for sharing your experiences.  There is a lot of interest in the MEN heater so hopefully someone can help you out on the fuel consumption.  My siphon system burns about one gallon per hour, but that much in a MEN style heater seems like quite a bit.  I am sure it puts out lots of heat!

Keep up the good work.  Enjoy the forum!

Oilburner

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Re: My Heater
« Reply #2 on: March 09, 2015, 07:29:49 pm »
I have noe experience with this type heater ( I struggle to understand how they get the oil hot enough to vaporise and work) but as to your fuel consumption, If you are not getting smoke ( or much of it) out of the stack, Then that's about all the efficency you will get.

These things aren't like car engines, They are pretty straight out that the more fuel you burn, the more heat you get. 
At the moment you are getting somewhere around 30-35Kw.  If you get the consumption you want, you would only be getting 8-9 at best.  Is 1/4 of the heat you are getting now going to be enough?

The efficency factor is in the heat transfer not the fuel burn, given that the thing isn't smoking like a steam train up a mountain pass.  After that, it's really a matter of how much heat from the combustion you get into the space you want to heat.

One thing I see all the time and don't understand is when people pipe the Chimney straight out the wall or ceiling in the shortest possible time.  There is a LOT of heat going out that chimney.  The smart thing to do would be to put the stove as far from the outlet as possible and run the flue inside the structure so there is max surface area for the heat in the flue to radiate out.
I have seen some clever designs where people encapsulated the flue and blew air along the pipe and then ducted that to another part of the house or building or just welded bits of metal to the flue to increase the surface area.  You could also run pipes through the burner itself. Some people put a fan behind this hich make a big difference or just angle the tubes so the heat can convect.

The heater you have is pretty big and to run that on under a litre of fuel an hour I don't think is feasible.  You have too much thermal mass and convection area and will find as you seem to have the thing over cools and goes out.
People ask me all the time, " how much oil does it burn?" I say as much as you want depending on the amount of heat you need.  And thats really what it comes down to. 
Oil burnt = heat output.                 

jbartlett323

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Re: My Heater
« Reply #3 on: March 12, 2015, 02:28:39 pm »
I see what your saying, but have a few points:

A.  They are like a car engine, the better stoichiometric ratio you get, the better (or more efficient) your fuel burns, therefore the more heat is output.  Thats why car manu's are always trying to make the same fuel burn better. You are correct on the idea that fuel only has a max possible heat output, assuming a perfect stoichiometric ratio.  As such, the real question is what kind of consumption does a Manufactured unit output, since in theory they are made to burn at optimal ratio?  I should be able to output (assuming max possible ratio) the same amount of heat-per-unit as they do, and possibly I do, its really hard to measure..

B. Just because I'm not pumping soot, does not mean that the un-burnt hydrocarbons are not being released on microscopic level, much like your car does.  Therefor, it is possible I'm not hitting the correct ratio.  But, yeah, I really think your prolly right still, and may be hitting the best possible ratio for my stove.

C. Burn efficiency and Heat efficiency are 2 totally different things.  Yes, my heat efficiency could be improved, however...
You saw my exhaust is piped straight out the wall.  You are correct that I may be losing a lot of heat there, hence the fan that blows on the entire body (not pictured) and therefore carries heat all over the shop.  But it is this way by design.  The way these heaters work, because there is no forced air input, is to create a Convection vacuum.  Basically, because my stove pipe is always at an up hill run, and the majority of pipe is sticking straight up outside, convection accelerates the air leaving the pipe, therefore pulling more air in the intake.  More heat means more air.  More air means better stoichiometric ratio, meaning better burn.  Basically why most of these systems end up as forced-air units as its easier to get the amount of air you want.  If I was to run a horizontal pipe across my structure, not only would it be a fire hazard, but it would also slow down my air speed to such a point as to make the stove non-functional.  Also, any attempt to cool the pipe (aka blow air across it to carry elsewhere) will result in lower pipe temps, lower convection, and therefore lower air speed.
We are considering attaching finned Heatsinks to the exterior of the body to act as a heat-exchanger and improve Heat efficiency.

D.  I would Love (Love, Love) to run at or just above 1Liter/hr.  Alas, I am running 1Gallon/hr, or 3.75Liters/hr.  1L/hr where I was lead to believe I should be running. 

Yes, the more fuel I burn, the warmer it is.  This is truth beyond truth.  And since the fuel is the only way I really have to control my fire, its doubly true.  But when I crank it to 11, I feel like I should be getting more.  Maybe not more heat, got plenty of that to go around, but same heat at less fuel.



to add:
These burners vaporize fuel in a couple of different methods: 
First, the room-temp oil is delivered to a red-hot manifold, therefore instantly gassing upon contact allowing combustion.
or
The oil is pre-heated in the fuel line (copper only for this) and is delivered to the manifold first as a liquid until FOT is reached, then gassing as it exits the fuel line.  This method can be slightly scary without a fire check-valve, because of the idea that fire could potentially follow the fuel back to the reservoir, although very unlikely.  When we reach this point, our efficiency goes through the roof!  If we could maintain this temp, 1l/hr would be a non-issue.  But maintaining it is extremely difficult without the ability to meter to fuel or air...
There are of course all sorts of variations on this, but as far as I know they all work on the same basic principles.  Most rely on the first method, possibly adding a top and bottom plate to form a kind of "combustion chamber" and aid in the mixing of air/fuel as in the original Sanders Style burner.


Oilburner

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Re: My Heater
« Reply #4 on: March 12, 2015, 03:52:23 pm »

I wasn't trying to criticise, only suggest.

At the end of the day, you are now burning 40Kw worth of fuel and saying you want to get the same heat out of 10Kw worth.
I don't think your efficiency, heat or burn, is that far off nor are you going to come close to the heating you want without a major change in the basic burner design.

jbartlett323

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Re: My Heater
« Reply #5 on: March 13, 2015, 09:20:50 am »
Hey, no worries!  Didn't think you were trying to do anything but converse!  sorry if I came off a little defensive, I have a bad habit of that on forums.  I think its because sarcasm and inflection just don't carry well in text, and I use a lot of both!

Anyway, you have certainly given me some food for thought.  Basically, the way I understand what your saying, is my Burn efficiency is just fine, and I need to harvest more heat from my burner.  So that's prolly gonna be the way I progress.  I can certainly turn the body of the unit into some sort of heat exchanger.  I think if I siphon heat directly off the fire, I should still be able to maintain overall temps and continue a clean burn. 
But what gets me is that others that have the exact same body as mine, have reported much lower fuel consumption, so I'm not sure the body is the deciding factor.  If I burn much lower, it doesn't always burn clean.  So I have to maintain consumption just to maintain burn... So IDK, I still think I'm missing something....

Oilburner

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Re: My Heater
« Reply #6 on: March 13, 2015, 05:25:17 pm »
I think you are basically being mislead.

Unless others have posted a way to repeatably measure heat output, you really don't know what they are getting. Their space could be smaller than your, better insulated, in a warmer climate, they could have a different opinion of heat output or warmth to you...... and so it goes.

Of course there is also exaggeration or error. Are they really getting the heat they say or burning the amount of fuel they reckon? All I'm saying is as far as I can see, there is no definable and measurable way to know anyones specific heat output.  All we can go on at best is consumption.

As far as routing the flue, it dosent have to be horizontal, it can be at 45o.  I didn't notice where you had it routed  but if it is straight out or up, putting it horizontal wouldn't matter anyway because its the height of the opening at the other end at counts , not the length or angle.  If you look at the Swedish fireplace and other thermal mass designs, they have long horizontal and zig zagging  flues to extract the heat from the fire and store it in the stone thermal mass. This means they only light a small fire and the heat is retained in the masonry and is given off gently for many hours.

Without doubt, your greatest potential efficiency gains lie in the Flue and the heat you can harvest from that.

As for the heater body, are there any internal baffles to putsh the flame onto the sides of the thing? If not you could be sending an awful lot of heat straight out that short flue.  You could weld a pipe or several through the heater body and have a small fan blowing through those or a fan on the heater body itself. The cooler you make it on the outside the more heat will want to transfer where there is the greater difference. Heat always seeks out cold.

I made a stove/heater which is on one of my recent vids where I located the flue at the bottom of the body of the heater rather than at the top. The difference in the efficiency of the radiated heat was absoloutley unmistakeable.  A couple of my viewers have already tried his and reported that they found they were getting tons more heat as well.  I believe it would work well in this design because it would keep everything in the burner section a lot hotter and therefore allow lower burn rates.

While I haven't played with this particular design, I'm not unfamiliar with draft burners.  I would suggest on this downdraft design, if you can't get the burn rate down reliably, you are over cooling the thing. Restrict the inlet a bit to reduce the air in line with the reduced fuel and it should run hotter and more reliably.  Too much incoming air will over cool the burner and cause it to have trouble at lower outputs.

I also notice you have the fuel line looped around the flue to heat he oil. That's basically a fallacy in it doing anything. If the fuel flows well enough to get that far down the line, it will flow straight in through the shorter pipe.  Having the fuel pre warmed does nothing for the burner efficiency.  I don' know how this idea came about or why people perpetuate it but it's a complete waste of time and has more potential drawbacks by far than possible advantages.

At the end of he day, I wouldn't worry a lot about consumption, it's free fuel after all!