[Stoves] Two Stove System - typos corrected v1.1

[Frank Shields]

Dear Crispin,

and another question. what is being talked about for the other considerations about fuel that make a big difference regarding combustion? Like size distribution, shape, rate of adding fuel to the stove, bark covered, rounds or split, old dense wood or young saplings etc. etc. Is there a plan to use ‘like fuel’ to represent a specific area? Seems important to me. 

Thanks 

Frank




> On Nov 29, 2015, at 1:06 AM, Crispin Pemberton-Pigott <crispinpigott at outlook.com> wrote:
> 
> Dear Frank
>  
> >The problem I have is all the estimates for values that are being used. 
>  
> I try to avoid estimating anything. I am willing to estimate the heat loss by convection and radiation from a pot based on a description of it. The rest should be measured.
>  
> >… Also; if we are talking Fuel Efficiency for Task 1 then what we (the people) want to know is how much fuel will be used for completing a task. So I would say the joules is a proxy for the fuel and a proxy for the task - not the other way around.  
>  
> That is the vox populi version of performance. Because fuels vary from place to place, the ‘answer’ you are given is not correct save for the one fuel you have converted the energy into. That is not a good approach.
>  
> What matters is not the fuel consumption but the relative fuel consumption compared with some baseline. Does it save 50% of the fuel? You can give that answer but it is more scientific to determine the answer using the energy values. The result is expressed in energy terms, actually, not in fuel mass. You don’t say a stove ‘saves 3 kg of fuel’. That has no meaning. It should save ‘70% of the fuel compared with an open fire’. That has meaning.
>  
> >And if you do use LHV how do you plan to determine what that is? 
>  
> That is why we are talking to Hirendra about his method for estimating it. Determining the H2 is not cheap or convenient. If it can be estimated within 1% of the true value, that is close enough for government work.
>  
> >If you plan to guess with a typical value I suggest using HHV.
>  
> I agree and will work on that at the international level. The US is using HHV but Europe does not. Because condensing heat exchangers are going to start appearing soon, we should all move to HHV. This will change the energy efficiency numbers, performance targets and so on.
>  
> >Using HHV will eliminate a lot of lab work and expensive equipment. 
>  
> Yup. It will.
>  
> >…Suggest adjusting moisture to an agreed upon value and letting it do what it is going to do. 
>  
> We should just use the contextual fuels for the conditions into which the stove is going. There is a strong desire in some quarters to have a universal test rating but it has no predictive ability. That is a reality and must be faced, even if it is inconvenient. If you bought a pound of sugar and when you got home found it was only 0.8 pounds, you would be upset. Claims have to be backed up by facts.
>  
> >Use dry wt as your energy value. 
>  
> Well that is how the HHV would work. It is a valid approach and is used in the US for lots of things. It is easier and allows us to rate the performance of very high efficiency products like condensing furnaces. If rated using LHV the reported efficiency goes over 100% which is silly.
>  
> Regards
> Crispin
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