[Stoves] WBT (never ending)

[Frank Shields]

Dear Crispin,

 

It seems the WBT is now not just a WBT but also plans to include a lot of great info regarding the combustion process through the cycle. I go along with that but would separate them into two test packages and for now just concentrate on perfecting the WBT using all the bells and whistles us labs have. Remember we have been talking (in words) about just the fuel section and still have the water simmering and boiling measurement method to develop.  Then when we get to the point where the fuel quality (not quantity) is the limiting factor we can experiment with fine tuning the fuel for the stove (or other way around).

 

Also;

<big snip>

 

Crispin:

I would love to have the real times measurements as accurately as possible. The problem is the moisture in the middle – the end we can work out with patience. But if the boiling portion of a WBT is done using wood that dries out entirely and is half charred by the time boiling arrives, what is the energy applied? How do we know what the energy of the burning char/wood mix is during simmering? What are we really trying to find out? The mass of fuel consumed each time a new copy of the task is performed, or the heat transfer efficiency? Or the CO emitted per MJ at different power levels? You must decide up front what we are trying to measure then devise an experiment that determines it exactly. This is done routinely in academia and industry. There is nothing special about stoves that requires us to use vainly imagined metrics and methods. Just get on and do the job properly.

 

Frank:

We need to have one purpose for the test (as you mention). For now it is develop a test method the gives us the info we need to compute ‘energy from biomass per water task’. This is more than enough to work out now.  If this is the one purpose the moisture in the middle does not matter. The rate wood turns to char does not matter if we stipulate the type of fuel to use because it will be the same for all tests and labs. But with different quality of biomass as fuel it will matter and to be experimented with at a later time when we have such a test where fuel quality is the limiting factor. Not yet! We need to get the test working before going out looking at exotic measurements. When measuring just CO2 and CO in the out gas you are thinking that represents such a large percentage of the carbon from the wood (leakage, tars, soot are so small) that you can use those numbers? Perhaps, but I see with only slight adjustments (air flow, dilution etc.) as making big differences. And I think a good gravimetric and CHN analysis to verify results is still needed as a standalone test or to verify the gas analysis.  

 

 

Thanks

 

Frank

 

 

Frank Shields

Control Laboratories, Inc.

42 Hangar Way

Watsonville, CA  95076

(831) 724-5422 tel

(831) 724-3188 fax

 <http://www.biocharlab> www.biocharlab.com

 

 

 

 

 

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