Does it matter how far above the preeated draw tube a person locates the burn plate/area?
Third Question:
I have read that a 5:1 ratio of Preheated air to Ambient air is about a rule of thumb for correct combustion of all gasses and that this can only be back figured through the amount of gasses being emited through the flue. Is this correct or do I need to look at it differently?
Strictly heat for indoor use. Especially for work shops ect. It will be derived into a unit that will be used in the living area for two purposes, 1 Heat 2 light. At the moment my main customers for this unit is such they are not able to use electricity. Every aspect of this units working success is dependant upon its "Natural" use of physics.
BTU/HR = Mass Flow (lb/hr) * specific Heat * temperature change.
Not sure what you mean by the burning plate.
If I understand your 5:1 ratio it sounds like you are recirculating preheated air and reheating it - I would need more details however, 2 items come to mind - first what is the O2 content in the return or recirculated air and second what temperature is it?
Again without any details you will need a certain amount of air for the gas you are burning. Air contains 20.9% O2 so anything less would require more flow to meet proper mixtures.
Also increased temperature would require more flow - correction formula for temperature -
SCFM hot = scfm cold * (460 + Temperature F)/(460 + 60F)
If this is a small temperature difference then it will not require much more flow.
Cumbuster
I appreciate your reply to my post. "Burning PLate" is the plate my material falls onto and is supported above the preheated air to burn. This preheated air is air drawn forward from a rearward collection chamber the opening of this chamber is 3.75² These tubes bringing this air forward is Ø3.25 i.d. Then in the vacinity of where the fire is burning I allow ambient air in through two holes Ø.75. I know this is not quite 5:1 air ratio. If you would like I can send you a 3 pg technical study of how this thing is suppose to work. Interesting thing about that this idea comes from two working models I am trying to combine into one furnace including some of my improvements. The trick is with these two working products use the air flow exactly opposite of each other.
If you would like to correspond through email I would welcome that. My email is Norb_g@hotmail.com
I hope this cleared up some of the mud my original question has caused. I will look at your calculations gain an understanding and get back to you.
I am not an engineer but am asking engineering questions. I ask that you please identify the following terms you use more
m = ?
Cp = ?
dt = ?
mass flow is what?
A. The mass flow of air per pound of fuel burned (needed is 35lbs of air per 1 lb of fuel for a clean burn)
B. Flow of fuel burned per hour
scfm = ? ? cubic foot per minute (not sure what the "s" stands for)
I am also trying to grasp the reasons for the constant of 460 and is the Temperature = to the temp I desire?
and what is the sum of 460+60 represents.
I think the answer is here but it needs to be understood.
m = Mass flow (lb/hr) of media being heated
cp = Specific heat of media being heated
dt = the temperature increase of the media
For you example 35lb/hr air at cp = 0.24 and from Tinitial=60F to Tfinal = 150F (eg. dt = 150-60 = 90F I do not know your actual conditions)
35 * 0.24 * (150 - 60)F
One thing you need to understand that is very important !
You need 10 volumes of air for every volume of gas at a minimun and that is just for burning the gas if you do not have this you will creating an a potentially explosive condition. The example above is the air over and above what you need for combustion.
Thanks for making it clearer for my computations. I will take a day and digest this thru application and will let you know what I am finding. In my case I am trying to burn green sawdust. Ideally I know through trial and error confirming another companies claimes that my initial temp to create gas from this medium is roughly 575°F and then I want to maintain a operational burn temp of a min 1300°F with a max of 1700°F This will be accomplished with no electronical device for assistance due to customers requirements.
The other aspect of this equation is to get air to flow "thru" the fuel. currently I am using to fine of sawdust and need to do a mix of about 2:1 fine course dust to fine dust.
Well I found out some of my trouble with the furnace. I bought some kiln dried wood shavings mixed them 2:1 wet to dry, Fine/course ratio. What a difference this made. I was able to burn aprox 35 gallons of total fuel in about 4.5 hrs. I was at full open burn at the time and maintained about 800°-1100°f for this entire time. I am estimating at this time that the total weight of this mass of fuel was 50lbs. I am building a second unit now with better air controls. I am certain I will get closer to my goals.
