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Post by dustinmattison on May 3, 2015 4:22:24 GMT -8
Hello, I would like to find more information on how to build the tubes inside the bench using clay and/or bricks. I don't have access to 8 inch metal tubing. I saw in your book that you can use adobe bricks to create the air flow passages through the bench. How is this done in detail? Can I use regular bricks sealed with cement or cob? What size does the square tube need to be inside the bench? 8x8inches?
Thank You
Dustin Sichuan, China
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Post by shilo on May 3, 2015 19:42:02 GMT -8
8x8 at least.
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Post by shilo on May 3, 2015 19:43:25 GMT -8
ask an air-conditioners man
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Post by peterberg on May 4, 2015 1:14:27 GMT -8
Hi Dustin, welcome to the boards.
Building the channels out of bricks can be done. This should be 8"x8" in an 8" system. The channels could be wider too, this will slow velocity down and extract more heat per linear foot.
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Post by Robert on May 4, 2015 10:17:36 GMT -8
Hi Dustin, welcome to the boards. Building the channels out of bricks can be done. This should be 8"x8" in an 8" system. The channels could be wider too, this will slow velocity down and extract more heat per linear foot. Dear Peter. I am wondering about this more extraction... When the velocity is lower, we do not have that much of a friction... And i do not understand this yet so much but the heat transfer depends on a friction as well, or dont? Why i am asking is that i have design a some kind of a contraflow heater... i have two downstream channels which i made quite big... and now i am thinking is it would not be better to narrow them a bit... What do you think?
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Post by satamax on May 4, 2015 11:27:46 GMT -8
Robert, i don't know about friction helping heat transfer, but heat transfer is all in the T for time, the more time gases, spend in contact with a colder material, the more heat they will give to that colder material.
If your channel is bigger than CSA of the system, it will have more volume needing to be filled by hot gases. Imagine the J tube as a restriction, then you have the bigger tube. And a chimney afterwards. The volume will affect the speed the hot gases travel through it. So the bigger it is, the more time it takes. Up to a certain point, when flue changes to bell. But still, that would be also valid for a bell.
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Post by patamos on May 5, 2015 22:24:18 GMT -8
I'm with Sata on this.
The temperature between any adjacent materials/mediums is always working to equilibrate. Earth is a slow conductor, so the longer the flue gas is in contact with it the more heat will transfer. If we put a given volume of hot gas in a flue run or bell chamber with similar ISAs, and closed off both ends… the temperatures of the earthen material and gas would eventually balance out.
Dustin, i would also recommend widening the flue volume where the flue changes direction - particularly 180 turns. The idea here is to compensate for the tendency of gasses to accelerate in curves.
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