Post by matthewwalker on Nov 1, 2012 9:07:43 GMT -8
I built a heated seating area for a restaurant/bar in NYC. I used a standard heavy brick firebox for durability and my half barrel method for the mass. The idea was to have quick response in the bench so the staff could fire it early in the day before they opened to heat it up, and then fire it again later in the evening for the late night crowd. We hid the works behind a metal enclosure and the exhaust will be hidden in an insulated stack box as well. It was a LONG system, 11 half barrels and a bit more for a system that was just over 30' long. I buried the first barrels about 5" deep and at the end of the system it was only about 2" deep. Then the whole thing was covered in slate for a nice finish.
Post by matthewwalker on Nov 1, 2012 10:10:01 GMT -8
Thanks Pinhead. It's an 8" system, and certainly is getting close to the maximum length. It also was dry fill which I believe went a long way towards helping it get going. I definitely wouldn't go near that long for an indoor system as it does take a bit of warm up to start flowing well. Is your mass still wet? I've found that the barrels are so effective at transferring heat to the mass that the exhaust is cold no matter the bench length until the mass is dry. Once you get to the point where the mass is no longer drying and evaporative cooling is stopped, you should see higher exhaust temps and better flow.
Post by matthewwalker on Nov 1, 2012 10:22:13 GMT -8
Oh, also this was an inline flue system, with the firebox at one end and the exhaust flue at the other. If you did a bell type dead end mass you will have cold exhaust with a short mass run depending on the depth of your exhaust flue. In my temporary fire pit post you can see I had an in-line system and a bell system. The difference in flow and exhaust temps are huge, with the in-line system capable of much longer runs.
I haven't cobbed over the barrels yet so they're probably radiating more heat than they will when finished.
From my understanding of a bell, the outlet/exhaust should be close to or on the floor of the bell. This allows convection to occur within the bell, exhaling only the coldest exhaust.
I did this with my system and it definitely makes a big difference; the half-barrel right next to the outlet is warm and the exhaust pipe is cool.
Do you feel that the outlet/chimney on your bell bench is contributing to the overall flow of the stove once the bench is warmed up? How tall is your chimney and what is it's diameter? Is it insulated?
Post by matthewwalker on Nov 1, 2012 10:47:06 GMT -8
I think you will see better performance once the mass is over the barrels, dried off and warmed up. They radiate a lot of heat and cool the gases quickly for sure when uncovered.
I think you have it right on the bell system, and from my experiments I decided to make this one with the exhaust coupled high at the same level as the top of the barrels and at the end of the flue path. I did it that way rather than a bell due to the fact that the system is so long. In this configuration I believe it is not so much a bell as just large flue pipe. As you noted there is a big difference between the two types of setup. It's one thing I'm loving about the half barrel system is the ability to do either bell or flue pipe depending on the desired function and system.
I do feel that chimney is an important element to these systems. With the bell system the chimney temps are cooler for a long time, so a tall chimney can be a struggle. However, once warm it helps the system a lot in my opinion.
In this system the chimney is 8" diameter and about 12' tall. It wasn't insulated when I left but I instructed the owners to insulate the chimney when they built the surrounding box for it. I ran the system hard for three days before I left and it was hours before I could feel a temperature difference at the chimney, but once it was warm there the whole system ran much better. I feel that especially when trying to push the limits of length like in this system the chimney temp is a very important factor in how it performs. Ideally I would run the chimney back next to the barrel if at all possible to help it heat up and draw.
May i ask what you mean by "dry fill" ? Was it insulating like vermiculite to maintain stack temp. Or was it sand? I have thought of a similar design. A stone bench that was hollow with channels, (i love the half barrels) but filled with a loose mass like sand. I was concerned of all the air spaces in sand though.
Post by matthewwalker on Nov 4, 2012 11:06:34 GMT -8
Thank you. It went well, people were very receptive to the idea and excited about it generally. I was a bit concerned about building it in the city, but materials were no problem to source and it ran cleanly pretty much right away, so no worries.
Sand makes for poor mass in my opinion. As you stated, it has a lot of air space and makes a better insulator when dry. By "dry fill" I meant that I took the clay rich soil I would have made into cob and just kinda packed it in there since I had a rigid form to work with. It wasn't exactly dry, more like damp fill. It packed well and transferred heat well right away, which should improve as it dries out, hopefully.
Post by matthewwalker on Feb 25, 2013 21:41:09 GMT -8
Thanks for the compliment! Feel free to PM me regarding location. I'm sure they'd love to show off the heater.
As for the wood, well, the burn works are surrounded by 4" or so of perlite, then the unpacked loose fill, which was around 1' or so if i recall correctly. I felt good about it at the time. I may be back out there this spring, so I'll re-visit that detail.
Post by matthewwalker on Aug 2, 2013 9:04:50 GMT -8
Thanks Adiel. I didn't do a batch loader on this one for a couple reasons. One was the system length, but mostly it was cost, durability, and simplicity. I was only there for a short time to build the system, so I wanted to be sure when I left that it would run smoothly and hold up to a lot of abuse. At the time my batch burners were still pretty early in development, and I wanted to leave them with something I had 100% confidence in. It also was fairly inexpensive, simple, and quick to build, which suited the project.
kkp: Mercedes: Benches don't get real hot. In fact, they are rather cool compared to other areas. You shouldn't need a mix like you described
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vesuvius: High Temperature Glass options,
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