[Stoves] [Methods] Error in the recommended Shell Foundation HEH Project Water Boiling Test http://ehs.sph.berkeley.edu/hem/hem/protocols/WBT_data-calculation_sheet.xls

[Crispin Pemberton-Pigott]

Dear Andrew

You numbers are fine though I do see that the formula with the /1000 does in
fact work. It is used to bring the 2.26 into line with the 4.2 because 4.2
is for per gm and 2.26 is x 1000 per gm.  That's all.  I think we discussed
this before.

As you show there is a large error when a high moisture level is reached. It
has now been corrected.

Thanks
Crispin

++++++++++++

So (N22-E17)*4.2+2260 is the heat needed to raise 1kg of water to
steam in KJoules

(if done in KJ then it is 4.2/1000 + 2.26, that's all) CPP

mc   dry wood   heat value  less steam available heat
10%  90%        16572.6     257.5      16315.1
20%  80%        14731.2     515        14216.2
30%  70%        12889.8     772.5      12117.3
40%  60%        11048.4     1030       10018.4
50%  50%        9207        1287.5     7919.5

>Moisture   Original    Corrected  Difference
>  0%        18414        18414        +0.00%
>10%        16749        16313        +2.61%
>20%        15345        14212        +7.96%
>30%        14164        12112        +16.94%
>40%        13152        10011        +31.37%
>50%        12275          7911        +55.17%

Ok so my figures better match yours but see the caveat that steam is
rejected at flue gas temperature not local boiling point to the effect
of moisture is worse than you predict, 10% in the case of 50% mc wood.

AJH