Surprising temperature measurements inside my bells
Oct 2, 2023 5:22:03 GMT -8
hallinen, martyn, and 1 more like this
Post by fiedia on Oct 2, 2023 5:22:03 GMT -8
My last posts regarding temperature measurements raised some questions. Looks like it needs some complementary data. Below is a summary of measurements done inside three different bells.
The last measurements were done on a bell heated with a 200mm BBR. Inner CSA above the HR was 10 times bigger than the HR CSA. Both bells2 pipes were closed. The thermocouples metal housing sticks out by a few centimetres inside the bell or the HR. It measures a mix between skin and fumes temperature. For more details : donkey32.proboards.com/thread/3853/8-200mm-batchbox-detailed-drawings.
The second bell was heated by 25 mm BBR. Inner CSA above the HR is 16 times bigger than the HR CSA. Temperature probes are stuck on the inside wall surface. They measure the inner skin temperature. More info on : donkey32.proboards.com/thread/3630/5-batch-box-brick-bells.
The first measurements where done on a bell heated by an old wood stove. Bell CSA is 10 times bigger than the stove pipe CSA. Details on : donkey32.proboards.com/thread/3346/brick-prototype-improve-standard-efficiency.
Overview :
Bypass :
Some sensors where put directly in the middle of the bell. They measure fumes temperatures.
Other sensors were stuck to the bell wall, measuring inner skin temperatures. The -44cm sensor is very close to the hot fumes inlet.
I conclude from my measurements that mainly the top 50 cm of the bell is getting quite hot. Large and short bells should be more efficient than tall and narrow ones. Heat risers represent a drawback since they need to be quite tall. DSR2 and DSR3 should bring a real improvement.
Such temperatures will rely on bell geometry and material. For example, one could get higher bell temperatures below 50cm by insulating the top of the bell. It would also reduce outside skin temperature. The heat transfer to the room would then take longer. I choose to keep double skin uninsulated bells to get a higher and faster radiating heat.
Another conclusion is that exclusively one or two top rows and the ceiling of the bell require refractory bricks (if not insulated).
The last measurements were done on a bell heated with a 200mm BBR. Inner CSA above the HR was 10 times bigger than the HR CSA. Both bells2 pipes were closed. The thermocouples metal housing sticks out by a few centimetres inside the bell or the HR. It measures a mix between skin and fumes temperature. For more details : donkey32.proboards.com/thread/3853/8-200mm-batchbox-detailed-drawings.
The second bell was heated by 25 mm BBR. Inner CSA above the HR is 16 times bigger than the HR CSA. Temperature probes are stuck on the inside wall surface. They measure the inner skin temperature. More info on : donkey32.proboards.com/thread/3630/5-batch-box-brick-bells.
The first measurements where done on a bell heated by an old wood stove. Bell CSA is 10 times bigger than the stove pipe CSA. Details on : donkey32.proboards.com/thread/3346/brick-prototype-improve-standard-efficiency.
Overview :
Bypass :
Some sensors where put directly in the middle of the bell. They measure fumes temperatures.
Other sensors were stuck to the bell wall, measuring inner skin temperatures. The -44cm sensor is very close to the hot fumes inlet.
I conclude from my measurements that mainly the top 50 cm of the bell is getting quite hot. Large and short bells should be more efficient than tall and narrow ones. Heat risers represent a drawback since they need to be quite tall. DSR2 and DSR3 should bring a real improvement.
Such temperatures will rely on bell geometry and material. For example, one could get higher bell temperatures below 50cm by insulating the top of the bell. It would also reduce outside skin temperature. The heat transfer to the room would then take longer. I choose to keep double skin uninsulated bells to get a higher and faster radiating heat.
Another conclusion is that exclusively one or two top rows and the ceiling of the bell require refractory bricks (if not insulated).
