Post
by lobsterman » Tue. Nov. 29, 2016 7:38 pm
ddahlgren wrote:lobsterman wrote:I would like to correct one common misconception about coal stoves. They do NOT heat primarily by radiation. You intuition may tell you that if the stove was placed in vacuum it would become very hot. Let us calculate that. The power per area radiated goes as the 4th power of the temperature on thevabsulute Kelvin scale. A typical stove puts out about 40,000 BTU per hour. (Thank you brits for these ugly units). You can look up the Stefan-Boltzmann constant. The temperature comes out to around 700 F. This is over every square inch of surface area. The stove is not that hot. Why? It is air cooled by convection. Radiation is only a rather small percentage of heat dissipation. The bass - heater design is a master convector. Air cooled. That is why it is efficient.
The fuel does not change anything and all things convect and radiate short of things like the sun heating the earth. A drum with a door and stack pipe will both radiate and convect heat. If BB single wall then works the same thermally as it can't change thermodynamics. If you want a convection stove it needs to be double wall and either rely on thermal differential to move air or a blower/fan. In my mind a convection stove is closer to a furnace and primary radiant more of a space heater.
Everything radiates. That does not mean that it it the dominant mechanism to shed energy. Stars excepted. It certainly does not depend on the fuel. Or the shape of the stove. Or any of the other BS floating around. It DOES depend on the fact that the stove is surrounded by moving air, fan or not. Put your stove in a small fully enclosed closet. Would it get very hot?
