Below is a conversation by personal message. The other participant agreed to place it in a new thread. This can only been done by copy and paste, that's why all the posts appear to be posted by me. Peter, global moderator
I'm new on this forum.
Here the issue concerning a bread baking oven that we are finalizing.
We have a system based on heat riser diameter 200 mm.
Concerning the air supply there is a particular design request from the baker to have external air supply.
This results in two particular solutions:
-primary air through an opening of 20% of CSA close to the wood feeding door
-secondary air supply from the same side wall with arrival of air at half height of the port (throat). In other words the P-channel is turned 90 degrees clockwise.
All dimensions of P-channel (cross section, overhang... ) would be according the ratio indicated by Peters calculation sheet.
I came to the conclusion that it should work as good as the classical solution. For our working environment it would be a big ergonomic advantage to apply this solution.
What is the opinion of the experiences forum members?
Thank you for your reply.
I can add photos (once I learned how to do)
Pasquale Angione from France
Last Edit: Dec 3, 2019 7:41:32 GMT -8 by peterberg
Although... you've sent me a personal message instead of opening a new thread, so other people can't read it now. What I could do is open a new thread and place your message as first post, if that is what you want?
As I understand it, you are planning an outside air provision close to but not in the heater itself. The right term for this is make-up air, in my mind the only way that won't influence the combustion process too much. The place is a professional bakery as I understand it, the bakery need to have quite a lot of a lot of fresh air. An outside air supply is in this respect an over-hyped facility, it won't add anything positive to the combustion process, and somethimes even negative, depending on how the outside part of the supply is configured.
Turning the floor channel 90 degrees in the horizontal plane will work but not to the same extend as the combined air inlet. The reason for this is that during the burn (in a combined inlet) the secondary inlet is gobbling progressively more air at the cost of the primary air. This is exactly what one would want, at the height of the burn there's proportionally more secondary air available. Taking these functions apart it would yield unpredictable results. And then, a quaranteed working system is offered with all the specs and measurements, why on earth would you do other things just because you think it would work?
Just follow the recipe, the cake will taste delicious, quaranteed.
Thank you Peter for your reply.You can open a new threadas you proposed ...this allows that all interested people can share. Your technical explanation about the gradual replacement of primary by secondary air is clear. But I think that my explanation of the technical solution was not clear. The solution I tried to explain would be very similar to the P-channel solution but instead that the air is injected from the top of the port it will be injected in the middle of the port by rectangular tube coming from the side wall.I will post two photos in order to show you what the solution looks like.
Anyway yesterday morning I found a layout solution how to keep the secondary air supply with the classical floor channel. I preferred this solution solution since the beginning because, as you explained, preheating of the secondary is included in this configuration.
The heating box will be 10 cm longer and a hole in the ground with the area 25%..30%CSA will supply combustion air from an "air box".Dimension of the 'tight'air box: Depth and width of the heating box; height 5 cm. (Volume approx. 5cmx50cmx70cm)This box will be connected to outside air.With this configuration the baker is happy an will have outside air and the proven design principles of batchbox rocket will be applied.Thank you for your help.Pasquale
I have to second Dan here, it won't work te same. Maybe even not at all. The vertical part (stub) of the secondary channel isn't there, so heating up of the steel won't accelerate the air velocity in the air duct. Moreover, air is supplied on one side only. What I learned the hard way during the years is that for best results the air provsion need to be symmetrical in the same way as placement of the port relative to the riser.
My advise: stick to the normal floor channel configuration in the sense of a combined inlet for both air streams. Whether or not this inlet get its air from inside or outside the building is largely irrelevant.
Last Edit: Dec 5, 2019 1:57:17 GMT -8 by peterberg
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