[Stoves] the 150 gasifier in operation in Vietnam

[Crispin Pemberton-Pigott]

Dear Andrew

 

>The temperature will be at an equilibrium when the heat from the gas flame
equals the heat lost by the metal by radiation conduction and convection, 

 

Agree.

 

>...as it is in the flame we can assume the conduction and convection have
little effect. 

 

Wow. Well, I need to think about that one. From the things I have calculated
I estimate the convection to be a large fraction even for things that are
not very hot so I might need to go back to the spreadsheet to look at
something this hot. 14% comes to mind for some reason, for radiation. I
guess you could also say that the colour is a measure of the gas temperature
if the material is radiating poorly. The more efficiently it radiates, the
larger will be the difference between the gas temp and the material doing
the radiating, no? It is effectively a heat sink.

 

My point (sort of) is that yes it is radiating but not very efficiently in
the IR band, which makes it so loud in the visible. As the emissivity does
not change much with temperature (in spite of many opinions to the contrary)
a shiny silver part will not emit well in the infrared so the temp keeps
going up.

>The only conclusion I can see from this is that at equilibrium a poor
emitter will become hotter than a good emitter.

 

Exactly. And the worse, the closer it will get to the gas temp. Yes?

 

Regards

Crispin

 

 

 

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