using two vent pipes for bell in bench....thoughts?????

I'm still in the design phase for a vertical, batch rocket mass heater with a single bench off to the side. I can't return the vent pipe in the bench because it needs to exit on the opposite side. I would like to have a bell setup to get as much heat into the bench as possible. I was looking at 6" vent pipe last night and came up with this idea using tee's and 90's and straits to form two parallel paths for the gases. I would love to get some feed back. Basically to pipes running in parallel one on top of the other. A tee connecting them in the middle so cold gases can drop down. As second 90 bend at the end for more cooler gases to drop.

Please excuse the crudity of the picture. I was using a touch pad to draw it.



-Mike

It might work, but I don't know if it's the breast solution available. Could you provide a little more info?

-CK

Basically picture a narrow bench with two 6" vent pipes. Both running in parallel with one ontop of the other. They would be connected with two 90 bends and 1 tee in the middle. See photo.

The idea is the warmer gases would stay in the top pipe moving more heat into the bench. Lower temp gases would exit out of the bottom pipe. Your basic bell principle.

An alternative would have the gases coming in at the top pipe instead of the lower pipe.

I think the main question would be, what is the width of your proposed bench? If it will be only 18" wide, your idea might be the only practical way. If 24" or more, you can make an actual bell easily, probably be more effective, and possibly cheaper depending on what you have for building the bell space.

Glenn Herbert wrote:I think the main question would be, what is the width of your proposed bench? If it will be only 18" wide, your idea might be the only practical way. If 24" or more, you can make an actual bell easily, probably be more effective, and possibly cheaper depending on what you have for building the bell space.

I'm still working on dimensions for the bench. I'm going to be working with COB for the mass surrounding the vent pipe. The bench will have an insulated cement base with Rockwool or EPS insulation imbeded in the bottom of it. It will have a stone face for the front and a cement "GFRC" bench top that will match the kitchen countertops. The cement countertop seat will cover the cob for heat transfer but will be supported by a steel frame.

Mike

Just wondering, what is the purpose of a steel frame to hold the bench top? Cob is a very sturdy base and would hold the top perfectly well by itself.

Thats is why, concern of the strength of the cob. If cob is strong enough and the cement top can be layed ontop while the cob it is wet (so it can be flattened out really well) I guess that would work fine. Just need to make sure it is nice and flat so the top doesn't get cracks.

Yes, the cob will support the top fine as long as it is 6" or so thick. It will work best if most of the cob is stiff; then you can add the last inch or two of cob and set the cap in place and wiggle it to settle it firmly. A rubber mallet to tap might help.