|
Post by jliebler on Dec 10, 2016 7:12:46 GMT -8
Well I;m back after a rather long absence. I'm still planning to use an 8" batch rocket with my adaptation of a "Walker" channel as the "fireplace", masonry heater (with heated bench), and wood fired white oven in my "dream house. I'll use 2 sliding plate dampers to "regulate oven temperature" and room heat. Well I changed the planned location, now the "fireplace is, diagonally, across one corner of the "living"room and the oven is n one of the rear walls, in the kitchen. These changes make an already big (ISA) way too big. I see three ways to make it "work". One is to carefully use the dampers. Two is to add interior insulation to reduce the "effective"ISA. Three is to add a "draft inducer" fan. For the interior insulation "solution" I need to calculate the "effective" (contribution to ISA) of the insulated areas using the thermal conductivity (at operating temperature) and thickness of the insulation. Is this correct? For the fan "solution" I'll need to power and control the fan and know the flow rate in addition to accommodate the condensation which will occur. What is the peak exaust flow rate of an 8" batch rocket? My inclination is to design with a combination of method 2 and 3, with a goal of never needing the fan but would probably use it for start up. Regards Jerry
|
|
|
Post by patamos on Dec 11, 2016 8:50:25 GMT -8
I'd be inclined to ensure you have a good start up bypass damper. And otherwise design the bell(s) so that you can access them to install extra features such as bricks or lighter weight non-combustibles.
So long as you have the functional bypass you can simply regulate the amount of hot gasses taking the straighter route to exit.
The bell's ISA is determined by functional average. Once the mass has heated up somewhat the potential ISA grows.
Another thought would be to make the bench 'blind'... with an inlet port but not purposeful flue path. This is common in some old masonry heater designs. Or perhaps use a smaller diameter flue run in the bench. Not much point in getting that surface too hot anyway…
my 2c
|
|
|
Post by pinhead on Dec 11, 2016 13:35:16 GMT -8
I'm a huge proponent of a start-up bypass. This allows you to run a larger/colder mass than you otherwise would be able to.
|
|
Ralf
New Member
Posts: 42
|
Post by Ralf on Dec 14, 2016 4:16:18 GMT -8
I agree with pinhead here, I fired my fully installed RMH with bell bench for the first time yesterday and without bypass it would have surely been a mess, I´m so glad I did install it. Highly recommended. Also useful for fine-tunig the draw of the stove and stack temperature later in the burn.
|
|
|
Post by jliebler on Dec 20, 2016 21:18:12 GMT -8
As I said initially I'll have bypass dampers. Also this has to meet US building codes so it will be "double" walled with ordinary brick on the exterior. But I also want to use insulation strategically. Insulating fire brick are almost the same price as dense fire brick, my thought is to make the upper half (or more) entirely of insulating fire brick and cap the bell with ceramic fiber boards under large insulating fire brick. I do believe that even insulating fire brick will extract some heat so their area should be considered in the ISA calculation but reduced by some fraction. The thermal conductivity of the insulated brick is about 1/5 that of dense fire brick. Is that a reasonable factor to use?
|
|