[Stoves] Water heating fuel efficiency formula

[ajheggie at gmail.com]

>> It's associated with any water that leaves the stove as vapour, it's
>> the amount of energy that was necessary to turn the liquid water in
>> the wood chemistry or water associated as free water in the wood into
>> a vapour. In fact this enthalpy of vaporisation varies with
>> temperature but it's around 2260kJ/kg. plus of course you have to add
>> the necessary amount of heat to lift it from local boiling point to
>> the exhaust temperature, I use 2.7MJ (.75kW) as a rule of thumb.


I made a significant mistake in the above, it's one I have corrected
in others' posts in the past. I meant 2.7MJ is equivalent to 0.75kWh,
the point being 1 kWh is a measure of energy and 1 kW is a rate of
expending that energy for one hour.

I tend to use kWh as it means more to people that have electricity and
pay for it by the kWh.

AJH