rocket mass heater: water as a thermal mass

   After sometime and a lot of reading. I have a design for my rocket stove. Please feel free to comment on my idea. As i wish for it to work well and not gas me.

For starters just like any ordinary rocket stove 8" insulated heat riser metal barrel ect. Now instead of duct work for the hot air I am going to line up fourteen 55 gallon steel drums and raise them up . The bottom of the water filled drums will be my flu. I will cob all of this with 3 inches of cob. Also Cash Acme® Temerature and Pressure Relief Valve (18822A-0150) on each barrel.

             thanks for the support

             

I guess I'm trying to figure out what your design is.  Did you intend to upload a picture?

it will be just like yours paul ,but it won't have round pipe buried in cob. in stead of pipe im going to use blocks to raise the barrels off the ground so the bottom of the barrels will be the top of the flu chase. ill try to make a picture

sorry so crude

So your thermal mass is barrels of water?

yes with pessure relief valves . and bottom of barrels will be exsposed to hot gasses

I've been toying with the idea of using water also... Your system might also have one side of the barrels exposed to the sun thru glazing (wud also have to have insulating covers to cover the glazing from  the outside- to hold in the heat). That way the rocket engine could 'charge' the barrels and then on sunny days the sun could recharge them.. You may be amazed at how long it will take to charge/heat that many barrels...

I can only speculate that you are having too many barrels...just a guess,  and also that maybe the hot exhaust might need to snake back through the barrels a second time.

I would not like to think about replacing the barrels though as they wud rust out. I wish i could get a hold of some stainless steel barrels that i saw.

Great idea, but you are in territory that is uncharted....keep us posted.

i wanted to use a 1000 gallon horse trough but im to poor

You mentioned blocks to hold up the barrels so i just wanted to say also that regular cement blocks get hard and brittle after being exposed to heat...with the weight of 450 ponds of water, cement blocks wud crumble.

maybe i can use washing machine instead of barrels . and fire brick. my  backup idea is to use ceramic tiles as the flu  stacked like this  i can test tile idea with drywall

Water does present some added problems - steel rusts  - stainless is expensive - galvanized can put off toxic fumes at high temps... the first barrel in line wud get HOT then the last barrel wud not get much heat.. open tops of water containers wud add a lot of moisture to the room. - Moisture can cause mold/mildew... structural damage...

Almost seems that the cob/rocks n stones wud be easier.

ronie wrote:
Water does present some added problems - steel rusts  - stainless is expensive - galvanized can put off toxic fumes at high temps... the first barrel in line wud get HOT then the last barrel wud not get much heat.. open tops of water containers wud add a lot of moisture to the room. - Moisture can cause mold/mildew... structural damage...

Almost seems that the cob/rocks n stones wud be easier.

i was going to seal barrels and add pressure relief valve vent it outside
if i was smarter i would seal barrels and figure out a way to cool hot barrels with other barrels. moving cold water at the end to the front and pushing hot water to the end

You could look into a thermal siphon - we used it in the 70's building solar hot water heaters... It circulates hot water to cold and cold moves towards the heat source.

The expense involved for 14 pressure relief valves - vented outside - and steel that rusts and clogs valves n pipes...and old barrels that must be replaced every few years.... ugh ...

It might be wise to consider a 100 gallon(ish )  system... with one water container instead of many...and cob to add mass .....

I see stainless steel tossed out all the time...they build something at a factory then toss out the old stainless and use something different when they remodel or something..

You might find a junker dude..(Has large trash containers all around town for businesses to throw their scrap metals into) - then ask him to be on the lookout for a 100ish gallon stainless steel tube/barrel/cylinder and maybe even trade him some scrap steel for the stainless..?

how long would a barrel last ?

I dont really know and i have tried to google it up looking under Trombe walls + 55 gallon barrels and i still havent found it. They made Trombe walls in the 70's and used some black 55 gal steel drums filled with water to collect solar energy for home or green house heating. Someone some where has an answer.

I built my house in 81 put in a new electric hot water heater and have replaced it 2 times so 2 tanks leaked over about 30 years... so my luck with hot water tanks is that they last about 15 years and then leak... now the hot water heaters are built out of thicker steel than a 55 gallon drum.. the 55 gal drum has been around doing other things b4 you get it... the water heater is new>>..??>.. so the used 55 gal thin steel drum could last 10 - 20 years is my guess... someone else  may have better guesses than i do... Some drums may have an inner coating to protect the steel and others may have bare steel inside... it may depend on what chemical was transported in the drum.

I am at the age that i want whatever i build to out last me and i dont  want to EVER have to  replace it... i wud rather go out of my way to find a stainless steel tank than get a free barrel and have to replace it every 10-20 years.  And if yer leaking barrel is the one on the end you are blessed but what if it is leaking somewhere around barrel  4-7 and you have to pull the whole thing apart? Might as well replace them all at the same time as after you replace barrel 6 - then it springs a leak somewhere between barrel 7 and barrel 10.

maybe im beter off just to build a roman bath house lol

You already brought up my primary concern:  rust. 

Here is my second concern:  KABOOM!  I remember Ernie and Erica making it super clear to not heat water without them to oversee the project because this is a recipe for explosions.  Do a search on this forum to see the previous discussion.  Yes - I see where you are talking about pressure relief valves - but isn't that gonna add a significant expense and take time to install properly?

Dirt is way easier than barrels of water.  And about 80% to 90% as good.

Per pound water stores 5 times more heat than rock (the density of
rock offsets this difference to some degree). One BTU will raise the
temperature of one pound of water one degree F. To raise the temperature
of rock or adobe requires only 1/5th of a BTU.
thats 80% less

Hypocaust

thats what i need to build

http://en.wikipedia.org/wiki/Hypocaust

maybe i could use a tile flu with sand or cob on top followed by this 2000 gallon tank on top  then insulate the sides http://images.craigslist.org/3n03mf3o85Q15Td5R49cbb776df9ea3e71564.jpg

i think i would have to put in  supports for the tank full with water thats 8 ton

charles johnson "carbonout" wrote:
Hypocaust

thats what i need to build

http://en.wikipedia.org/wiki/Hypocaust

Cool link!

(I changed the subject line so folks can get a better idea of what we're talking about)

you are going to need more surface area exposure to the flue gases. just running the pipe under wont do the trick you will not have enough contact.
but if you can bury the drums on one side and run a couple passes along the barrels it might work. if you are going to do a vertical stack you will want the flue gas temp to be no less than 90 degrees or it wont rise. you will want to test the system with all the mass in place out side if possible cause your going to have to fiddle with it a bit to get the right amount of mass for the installation. again please document it.

ernie have you ever used ceramic tile as the flu to increase surface area

If you could use stainless steel for all the metal parts (expensive, but a lot more durable), what about laying the barrels down end to end, and plumbing the flue through the middle of each of them?  In essence, the barrels would form a large diameter pipe, with the flue a smaller diameter pipe running through the large one.  You could probably figure out some way to use the system to heat your hot water as well as your house.


However, what happens if you have to be gone during the winter long enough for the house to freeze?

Kathleen

charles johnson "carbonout" wrote:
ernie have you ever used ceramic tile as the flu to increase surface area

yep it works but you have to be careful the tile is not the insulating kind.
(the first one i did kinda failed cause of this) The water is possible the best thermal mass you can get but you will have to duct it so you get as much contact as possible with the barrels. I am thinking you will want about three passes but your going to have to fiddle with it. when you make the duct from the tile you will need to make sure the area is the same as the burn tunnel till you get to the third pass then you can probably make it about half the burn tunnel area. as the exhaust cools it will get dense so it needs less area to flow through. this will also have the effect of slowing your stove down a little and that will help heat things up. please test it before you install the stove in your house. If you need real time help email me and we can give our phone number.

It will never work

The weight alone will crush your system if not when the barrels rust you will get a back flush of boiling water if you ever get them to heat that high

A simple copper pipe running down the exhaust system would be better with an external 12v water pump

i was hoping to slowly work the temp to 140- 180 on 1000 gallons or more doesn't have to be barrels i've got a place to put it just need the design

I think Cob is ugly, and I would never put it inside the house. When I do end up building my own house the plan was to build a concrete bench as a thermal battery, but I've had concern about thermal expansion busting it up. It occurs to me that a concrete trough could be built fairly inexpensively and filled with water, then a stout piece of chimney pipe could be run through that water to pull out the heat. If you covered the bench with something similar to a concrete counter top (you would have to seal the cement some how to prevent water pushing its way through it) and then all you would need would be an air layer with a vent (preferably to outside, with the humidity) to totally negate the possibility of an explosion.

Emerson White wrote:
I think Cob is ugly, and I would never put it inside the house. When I do end up building my own house the plan was to build a concrete bench as a thermal battery, but I've had concern about thermal expansion busting it up. It occurs to me that a concrete trough could be built fairly inexpensively and filled with water, then a stout piece of chimney pipe could be run through that water to pull out the heat. If you covered the bench with something similar to a concrete counter top (you would have to seal the cement some how to prevent water pushing its way through it) and then all you would need would be an air layer with a vent (preferably to outside, with the humidity) to totally negate the possibility of an explosion.

Hmm.  Some food for thought in this idea (although personally I like the look of cob better than concrete).  In our climate, the added humidity would usually be a plus.

Kathleen

A little sodium silicate (water glass) dissolved in the water, perhaps along with some soap, will help prevent rust. As long as the water isn't going to be used for anything other than thermal mass, you should be fine.

It also occurs to me that this could be pumped through a radiant floor system in order to provide radiant heating in another part of a house. Have your rocket boiler on the first floor and use it to heat bedrooms on the second, etc. Does anyone know off the top of their heads what temperature water is run through radiant flooring?

Emerson White wrote:
Does anyone know off the top of their heads what temperature water is run through radiant flooring?

I believe it can be as low as 85-90 Fahrenheit.

I ran across this at http://www.sustainablevillage.com/index.html :

[url=http://www.sustainablevillage.com/servlet/display/product/detail/41048]Sun-Lite Solar Storage Tubes

Looks like what you were planning on doing, only using solar energy.

Wanted to confirm, that water will not rust steel if it has the right ph. This is why re-bars do not rust in concrete. Perhaps a few kilos of cement put into the water can solve the issue?

We could insulate the bottom of the first 1-2 barrels so they don't heat much faster than the rest.

Also _IF_ one can make safe opening to atmospheric pressure, it should be preferred. This is much safer and cheaper. _Just don't close the barrels!_ You can put the a lid on them, as long as you do not seal it, or put weight on the top. It will be like a lid on a pot. Do _NOT_ make pressure cookers people! Also do not fill the barrels full.

If you are worried about rusted tanks look for sacrificial cathodic anode rods they are what are in most water heaters today.

needing a blow off valve? try looking at radiator caps. there cheap and last a good long time.

Soft copper tubing is your best bet for heating water, depending on how big of a system you want and how quickly you want to heat the water will determine how big you will go with it. simple facts takes 8.34 btu to heat a gallon of water 1 degree 60-180 is going to take you 1000.8 btu to heat it. You want to be thinking of what to use and where to put it to make every thing work as a unit and make it as efficient as possible. From what I have seen concentrated heating of water is the best way to go. take a little bit of water, heat it as hot and quick as you can and put it back into a insulated storage tank. Just my two cents but it makes common sense.

Think about this for a second, In stead of having a presser valve on all the tanks make a system out of cheap piping black iron pipe or what ever you want. have all the small holes on top facing the same direction plum it all up and have one for all of them.

Open to atmosphere... Why would you want to create a potential bomb by trying to keep this system under pressure? Watch the mythbusters episode on what happens if the valve fails and I think you will agree. If the tanks are all vented to atmosphere the system will be no more dangerous than an open pot of boiling water.

That would be the simplest