After a quick look...

propane:

latent heat of vaporisation = 185 btu/lb

heating value = 21,622 btu/lb

I *think* you'd subtract the latent heat of vaporisation from the
heating value...

so, theoretically, with 100% combustion, you could get 21,437 btu/lb
of propane.

I'm not sure of this calc. Can someone confirm?

alistair

On 8-Nov-10, at 5:22 PM, Edward Maglott wrote:

Wow, that is impressive Alistair.  I forgot all that chemistry years
ago but you make is look easy.  Can you calculate BTU produced in
there somewhere?  How many BTU is the little buddy rated?

Refilling propane cylinders: I have several that I refill.  I weigh
them empty and write the tare weight on them.  Freeze, refill,
re-weigh.  If you freeze them, you can get more propane into them.  I
have found by experimentation that filling from the 20# tank into the
frozen to 0 degrees F little tank, it will take just about the
correct amount.  I usually stop the filling process when I can't hear
fluid movement anymore.

Edward

At 04:39 PM 11/8/2010, Alistair Bell wrote:
> aha! its an opportunity, not to answer question, but to work out just
> how much water vapour is produced by burning the 1 lb bottle of
> propane.
>
> lets make assumption that no CO is produced, ie the heater is working
> perfectly, and that there are 16 oz to the lb, or 454 g.
>
> combustion equation:
>
> C3H8 + 5O2 ----->  3 CO2  + 4H2O
>
> so we see for every mole of propane burned, we get 4 moles of water.
>
> molecular weight of propane = 44 g/mol
>
> moles per 1 lb bottle = 454/44 = 10.3 moles
>
> therefore burning the entire bottle would produce 4(10.3) = 41.2
> moles of water
>
> molecular weight of water = 18 g/mole
>
> therefore 18(41.2) = 741.6 g of water produced.
>
> almost 3 cups of water into the van in 6 hrs.
>
>
> alistair
>
>
>
>
> On 8-Nov-10, at 12:16 PM, Courtney Hook wrote:
>
> Just hauled out my little Buddy Heater and it claims 6hrs on low with