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Reply with quote  #21 
DUH, nobody noticed my arithmetical error [redface]

1000 x 0.018 = ... 18 and not 180 !

So 400 BTU would give a temperature rise of 400 / 18 = 22 degrees Fahrenheit...

(This is in static perfect conditions, as stated in the question).

Even under these perfect conditions, and as Dan rightly says (and which I overlooked...), the milk jugs would not give up all of their 400 BTU, because as they lose heat, the room gains heat, therefore there will at some point be temperature balance ("equilibrium").

This means, a situation where no more heat is being transferred between the two bodies.

So this point would be "somewhere" between the room starting temp of 70°F, and the milk-jug starting temp of 100°F.

So the room gains heat as the jugs lose heat.

But the room would still heat up...
... under perfect conditions still...

But as Gary says also, the question in empirical terms, is one of losing heat to the outside, as you could not get a room insulated perfectly...

Whence the need to calculate for a room's heating requirement in real terms, i.e. how much heat does the room require, to stay at the same temperature, in order to remain at (some semblance of...) thermal equilibrium with the outside since it will be losing heat all the time anyhow...

(I did this cacluation for my own bedroom, and it is 300 watts) (that is less than my halogen lamp...).

(and has been confirmed by 7 years of occupation where we have NO heating in the bedroom...)

So I would give this milk-jug thing a try anhyow !
(but not until I had run the Room Heating Calculator first...)


(1)  "Heat goes from hot to cold, there is no directional bias"
(2) It's wrote, "voilà" unless talking musical instruments...

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