Scott Weinberg

I am hoping one of the many that support this idea can give the rest of us a report.

Simply take a steel container, a 20-30 gal oil drum seems like it will work for this test.  if your in north east Iowa, I would give you a barrel or three.

Please pick out a location for your resistance wires/rod/element, what ever you want to call it. And please do tell where you put them  in your mass,  And then fill the barrel up with sand.

At this point, plug into your solar panel and let it start charging, (passing voltage to the element)  or if you want, you buy a 110 volt water heating resistant element as many of you stated these are only 10-15 dollars.  Plug it in and let it rip. Make sure you record temp of sand at bottom, middle and top,  And if you like, let us know of which method you used. What size you used and what the dry sand weighs, that way we can easily figure out how many BTUs your bank is storing

Let us know the results after one day, then two days and so on.  Make it scientific, your test could help create world peace.. So this will require nice dry sand as wet sand might be not safe and possibly a bit variable due to temp variations,  sand grade or size would also be nice, so others can duplicate when it works well for you.

And at the end of next week, you should be able to post the results.  I would think sand weight, sand height, and volume will also help.  Keeping it simple as stated on this forume,   would be is very important. No need for switchs, just let the mass storage begin and then report NOT what is thought should happen  but what it really did happen.  

We will wait for the results. and please let us know.

Benjamin Dinkel wrote:I do think Scott has a point here.
Sand is cheap, available and easy to work with.
But it’s also somewhat of an insulator. So apart from the heat capacity (1200 kJ/(m3*K) in sand vs 4200 kJ/(m3*K) in water)the question of how to heat it up is an important one.
I don’t know how the fins took care of that. Maybe pressing air through the sand?
There’s a reason a lot of heat storage happens with water. Not the best conduction either, but when you heat some it rises so your heater can continue heating cooler water. And it has a big capacity.
Is water an option for your case?

Or is your question rather whether anyone ever installed an electric heat source in their RMH mass?

Thanks Benjamin, if I may, I will explain a bit more, where I feel projects go from basics to complex, and maybe I am missing something, but in general, this is often how it goes.

if we consider our base heating system being used  in of the latest stove designs, which heats our mass in as effecient method as we possibly can, and we have proven all over the world that we can do this with NO mechanical means.

From this, we as rocket designers-users-even dreamers, start looking at additional storage methods, thus the name of this thread. Very quickly we note IT CAN BE DONE, but just as quickly find in most cases that it involves, a vast addition of mechanical means.  I bring this up, for one reason only, that being, I was not trying to say it can't be done, but rather if it is attempted, beaware that it can easily approach a level of no return on investment.

All great ideas start somewhere,  I just wish some of these ideas go down the practical path first, then get cleaned up,  Rather than proposing a dream, and spending years to convince others that it just maybe, quite possibly, with greatest of hopes, can work.

Sorta like spending $10K to save $1K, we often see in many simple ideas that have grown into complex ones. Another proof of this is the very often "showed on the internet" technolgies that promise great things, just as soon as they get
1) funding
2) figure out a way to make it work for the masses,
3) more funding,
4) and get technology to let them do what they proposed.  
     This of course is not true in all cases, but is generally par for the course.

Best of success!

Dry sand has proven to be a pretty good insulator, and pretty poor at heat storage,(getting it uniformally heated up) vs brick/stone and other solid material.  Although It can be transportaed and placed fairly easily. that does not make it that versistal for heat storage.  And of wet sand works great up to the boiling point of the "wetness" But that is a whole different can of worms.

Pebble banks, for much of the same reasons. Both have similar claim in that they are easy to build with.

Eugene Howard wrote:So a few observations and perhaps clarifications......



1. Hotter stack temps.......don't stall the engine with too much load?
2. Less stack height? Can recall issues when folks put rockets in basements and ran flues up 2 or 3 stories and they didn't work? So short stacks to chimney top vs tall? Then there would be issues with inside chimney stacks vs. outside?
3. Does it matter if chimney flue pipe is single or double wall?

Seems like there are a lot of engineering variables to consider.......and perhaps some guildelines set forth as something to consider and follow?

I probably sound like a broken engine to those that have followed my comments in the past, but will repeat a few here.

1)  Never have a seen a fire getting to big for the design, basically meaning every design has the "proven dimensions"   for the size of the flue. With that in mind, I would answer, that NO, sized right, you will not stall the engine with to much heat,

2)  Are you calling the flue a "stack" or are  you referring to something else, my flue/chimmeny or maybe what you call stack is 35' plus tall.  So not sure what is meant by something  not working because stack height.  I will put forth that restrictions, will be first and formost the problem with flues.

3) would seem to best study what you need to know about keeping warm air rising.

Again proven ways have been just that, proven!

Peter van den Berg wrote:
But... there is a certain effect that is firmly based on physics, the kind that won't be influenced by faith. That effect is mostly referred to as "chimney stall". About +/- 20 minutes into the burn, the exhaust gases into the chimney need to be warmer than 60 ºC (140 ºF), otherwise the chimney draw will cease to exist and all smoke will stream into the house. What I mean with temperature measurement, is done in the very center of the chimney pipe, where the stream has its highest temperature and velocity.

I would like to praise Peter for his explanation here,  as most of you know, I am blessed  to have tremendous draft 97% of the time, It literally can suck a newspaper crumpled  up right out of my hand and do so even without a fire lit, but a warm stove. I attribute this to Peters well designed batch box that I built a couple years back.

Anyway, if I get in a hurry and rush a cold start, exactly as Peter described can happen. But oh so- I dare say- fixable, with gentle adjustments on the bypass, and in my case, you can hear when it is going well. I never experience the need or requirement when my stove is warm

Well done Peter

Scott

Twice  smoked bone in Ham with pineapple and maraschino cherries.  Ham the way it used to be.

kees ijpelaar wrote:

The book roacket mass heaters do state that the tunnel is the smallest part, also with square or round rizers.

C is the burntunnel in the book see attachment need smaller then the rest.

I go just test all, if nabure is quite but I have trouble with her who is heavy anti woodfires.

I think I would toss what ever book your referring to, and use the well published and PROVEN numbers on this site.  The J-tube with the right numbers simply works well if your able to keep feeding it. Pretty hard to get around that fact, if you want something that works on the first go,  it would seem relavent to go with proven numbers.

kees ijpelaar wrote:HI James andBenjamin.


I have pick a piece of tekst here from a book rocket mass heaters II

C is the cross-sectional area of the horizontal
 The size of the cross-sectional areas of
all parts of the stove’s internal ducts should never
decrease below that of C. In other words, the crosssectional areas of F, G, H, J, and k should all be
greater than that of C.


Wel I do now now why it does not work well, the cros sectional space in tunnel is 225 cm3  and the rizer
is 176 cm3.

I went back thrugh your post, and did not find anywhere that you explained what these crossectional areas of F, G, H, J and K are So I am thinking your leaving a lot to us for our imagination.  This is hard to suggest anything, not knowing the details.

And you list cross sectional  space as  cm3,  Where you actually in your calculations needing a description of cm2  Where yours would be listing volume, and other area of opening.  Again, I am just trying to guess what your trying to tell us.  if everyone else has it figured out, great.  

Best of success.

[quote=Peter van den Berg

Glenn Littman wrote:Once the system is fully dry it will be interesting to know the firing cycles to get it up to temperature and maintain it considering the enormous mass. It will also be interesting to see how it retains the heat over the 35-40 hours that the store is closed and the external temperature when they reopen on Monday.

At the moment, they use the clever thermostat of the gas heater as temperature gauge. It is able to show the temperature over each 24-hour period, hour by hour. So they'll know what temperature decline is going on during closed hours.

The beauty of recording devices today, depending on what you want to spend, is that everything can be recorded and saved. As the stoves don't get really get sofisticated, the how to's and why for's really get interesting.   In my case, going into the third year, we are comparing heating up the mass 25 degrees warmer than in the past, having it cool down about the same % as always, but then with next day firing, get to the warmer level with about the same amount of wood,  while I don't have solid numbers yet, it would appear that we are "feeling more heat" with the same amount of wood, after day 2.  Part of the equation if you love the math, is that the exit flue temp went up 14 degrees on average vs the mass increase of 25 degrees..  Fun working the numbers.

Please read-  This is only my experince, I am not suggesting or implying your results will be the same.  But without gages, recording, and study, it would only be a great working warm stove.  now it is a on going experiment daily.