How do I estimate the system resistance for this Fan application? 3

[loanky]

I'm planning on designing a centrifugal fan that will blow air for combustion of charcoal which is contained in a cylindrical drum but I need to know how to estimate the system resistance (the static pressure) and the flow rate.

Please, I'm new to fan design and I don't know how to get my fans flow rate and corresponding static pressure too. I don't know if there is a table where I can get further information to help in the design process. I've attached the complete design image of my machine for more understanding of what I'm trying to achieve.

Thanks.

 

[chicopee]

My thinking is first, you should estimate a certain amount of CFM for the proper combustion of a certain amount of charcoal to be burned within a certain amount of time. Once estimated, your selection of a centrifugal fan will be trial and error, therefore, perhaps two or three fans (with varying fan characteristic curves and making sure that these curves encompass the estimated flow rate; these curves are provided by the supplier) will need to be mounted individually with manometers at the fan inlet and outlet so that measurements of static pressures are recorded. Once that you firmly believe that the stove is performing according to your satisfaction from one of the fans, you'll compare your static pressure result with your fan characteristic curve for the actual CFM for your answers.

 

[bimr]

You need to obtain and review the ASHRAE Handbook.

http://www.lorencook.com/PDFs/Catalogs/Cookbook_Catalog.pdf

https://www.cedengineering.com/userfiles/How to Size and Design Ducts.pdf

http://www.pdfdrive.net/ashrae-901-2010-e203032.html

 

[LittleInch]

I agree with Chicopee - this is not a "standard" fan system and the only way you're going to work it out is a bit of trial and error and seeing what other similar furnaces do.

Without knowing if you're blowing air over the top, from underneath, depth of charcoal etc I doubt you will be able to get a figure. Flowrate you can probably estimate based on over supply of air / oxygen, but a lot depends on what temperature you want to get to.

If you can find a small forge or smith where they heat horses shoes you might get an initial idea about flowrate and power.

search for it and you can find gems like this

https://www.bladesmithsforum.com/index.php?/topic/23920-air-flow/

https://www.iforgeiron.com/topic/47708-air-flow-for-charcoal-forge/

control over the air supply seems to be required so you start low then increase as temperature required goes up.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[loanky]

Thanks everyone and sorry for the late reply! This is what I decided to do after reading replies and I want correction if needed: I calculated the pressure offered by the charcoal height and used it as the static pressure resistance of the system. I had previously determined the quantity of air required to burn the total mass of charcoal of 27.78kg which is 236.3m^3. Then, I assumed that the quantity of air will combust the charcoal mass in 40mins. From there, I determined the flow rate required to achieve this which is 0.098m^3/s and I based my fan design on this two parameters.

For more details about the machine:

The machine is design for frying Gari. As described earlier it has a cylindrical compartment for storing charcoal. The Gari mash is held by a pan separating the combustion chamber from the fring chamber where frying takes place with the help of a mechanical stirer.

The image belows shows the outline of the heating system in simple diagram