[Stoves] Amount of charcoal for simmering

[Paul Anderson]

Stovers,     (this will also be a "post" at my  www.drtlud.com website, 
BUT all replies and discussions should be directed via the Stoves 
Listserv.   Dr TLUD does NOT carry on separate discussions via comments 
to his website.)

I am looking for a calculated answer that could give guidelines about 
the sizes of charcoal-burning stoves, referring to how much charcoal 
must be consumed for the cooking tasks.

Question:   How much charcoal  is needed (per minute, or per hour, or 
??) to maintain a pot (5 liters?) of already-boiling water at the simmer 
temperature of about 96 deg C?

So many variables, but the replies can state whatever "givens" or 
assumptions you wish to make, such as:

1.  Heat transfer efficiency of the stove-pot configuration:    Is 30% 
about typical?   And does that vary between clay-mud charcoal stoves vs 
metal charcoal stoves?  Please specify, if your response takes that into 
account.

Reference:   See Experimental study for improving energy *efficiency* of 
*charcoal stove* 
<http://search.mywebsearch.com/mywebsearch/redirect.jhtml?searchfor=heat+transfer+efficiency+charcoal+stoves&cb=XQ&p2=%5EXQ%5Exdm002%5ES03729%5Eus&qid=499b92ca6697461da7047b820086bd7d&n=77DE8857&ptb=F7EBB78D-F7A7-4077-B858-0D10F0C7CB0E&si=COjP4cCp0rMCFao7MgodRQUALQ&pg=GGmain&action=pick&ss=sub&pn=1&st=hp&qs=&pr=GG&tpr=hpsb&redirect=mPWsrdz9heamc8iHEhldEVRIIbml7k2%2FvmB8U5crkZmbOTdLROAzdl%2F4ZQYYskvUwjkty6%2BVZ%2BNQiIr863cMN8jdRHpxuJvwsN2u6HPpdnPNB%2BBymTTjJMbwcgCi5H8Q&ord=1&ct=AR&> 

http://nopr.niscair.res.in/bitstream/123456789/3794/1/JSIR%2068(5)%20412-416.pdf
with reported efficiencies between 21% and 62%.

2.  Still air, no wind.

3.  Comments on types of pots (Stainless vs aluminum vs other).

4.  Lid or no lid.   Probably no lid because so much testing is done 
with no lid on pot.

5.  Ambient temperature:   probably 22 to 27 deg C.

6.  Any other variables.?

Comments:   The question arises because the TLUD stoves  (and any other 
charcoal producing stoves) can be a convenient and low cost source of 
charcoal for a household.   That household has some cooking needs for 
LOW heat (simmer-type), and a charcoal-burning stove.

Example from the world of stove testing:  a pot with 5 liters brought to 
boil can be placed onto a charcoal stove for the remaining 45 minutes of 
the standard water boiling test (WBT).   The charcoal could be already 
red-hot, having been placed in the charcoal stove directly from the TLUD 
stove that made the charcoal.   How much charcoal is needed for that 
simmering task?

When we know the amount of charcoal, we can calculate backwards to 
determine how much raw fuel was needed to make that charcoal. (That 
amount of raw fuel is approximately 5 X of the charcoal weight.)   
Example:   100 g of char is produced from 500 g of woody biomass.

Therefore, about 70% of the energy content of the raw fuel would be 
available for INITIALLY putting heat into the pot.  I think we should 
assume better than 40% heat transfer efficiency because that is the 
target for Tier 4 stoves and can be achieved by gas-burning stoves.    
40% of 70% is 28%, so round it to 30%.    And 30% of the energy content 
of the raw fuel is how much?     1 kg of wood has 16 MJ, so 500 g has 8 
MJ, and 30% would be 2.4 MJ.

Somebody please complete the calculations:

A.     2.4 MJ will raise 5 liters (5000 g or ml) of water how many degrees?

B.      How many g or ml of water can be brought to 100 C if starting 
temp of water is 20 C?

In the end, I hope we have some understanding about the amount of raw 
fuel and resultant charcoal needed to accomplish the WBT with minimal waste.

Paul

-- 
Doc  /  Dr TLUD  /  Prof. Paul S. Anderson, PhD
Email:  psanders at ilstu.edu
Skype: paultlud      Phone: +1-309-452-7072
Website:  www.drtlud.com

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