[Stoves] Re Alexis Belonio article

[Crispin Pemberton-Pigott]

Dear Simon

Sorry to be unclear.

What was trying to describe was that for any given volume of gas passing 
through a port beside a pot, transferring heat to the pot, the quantity of 
heat passed to the pot would be related to the specific heat capacity of the 
gas, thus if the steam were 50% of the gas volume and air+combustion 
products the other 50%, the heat capacity of the result would be about 1.5. 
If the volume passing were the same (unlikely) the heat transferred would be 
higher if the temperature was the same to start with.  Your point is that it 
would likely be lower.  I agree, however I was only talking about the theory 
side.

If we build the model step by step I am sure we can agree on all of it, and 
it will be really useful if it turns out the steam can lower emissions.

>I would imagine the 'heat transfer ability' of steam compared
>to air is probably less since for the same amount of energy
>absorbed by the gas the increase in temperature will
>be approximately half.

Agreed...but I was coming to that later on when we put numbers to the stove, 
or the model of the stove.  With the shortened flame and reduced side losses 
(compared with the picture shown without steam injected) it is possible that 
the temperature of the (shall I call it the 'steam and gases'?) might be 
similar to the gas without steam.  Still that was not my main point.  I 
wanted to understand the heat capacity of the while gas stream as the steam 
is added.

>So the flow of gas will be cooler than either air or CO2, reducing the heat 
>transfer.

Yes, on condition that the steam is not superheated.  If the temperature of 
the steam is high enough, _and_ it is helping to burn some of the spare 
carbon, the temperature of the steam+gases could be just the same as without 
steam injection.  This could be accomplished by winding a pipe around the 
inside of the boiler.  Heat to boil would still get through the coil to boil 
water, and the steam exit temperature could be 600 C or so.  Burning spare 
carbon and CO coule add another 100 deg and the result would be a larger 
volume of gas than before, with a higher specific heat content.

I am worried that unless the residence time of the gas against the pot is 
increased (by channels as discussed with Dale Andreatta) there would not be 
enough time to get the heat into the pot.  At a higher velocity it would 
cruise into the room past the pot.

What do you think??

Thanks a lot
Crispin