cross posting to sci.engr.mech
Dear Pete Mills:
I'm sorry if this is more of a chemistry question than a physics question
> but wondered if someone in this group may be able to shed some light for me.
This is physical chemistry, more than just chemistry.
During the combustion process in a domestic boiler, for arguments sake, the
> dew point of the hot products of combustion can be altered by different
> factors. The type of fuel used and the excess air in relation to
> stoichiometric combustion are two of these.
>
> Could anyone tell me exactly how these two factors work and what effect they
> have on the water vapour within the products of combustion?
I'm not sure why the type of fuel, other than a slight change in the amount of water produced per kilogram of fuel burnt. Hopefully you'll get some better answers here...
As to the excess air, the resulting mix of excess air plus combustion products, has a lower relative humidity (which is lower percent water at the temperature considered), and hence a lower dewpoint. Of course the excess air itself is going to lower the bulk temperature somewhat...
David A. Smith