William LeMieux wrote:
Satamax Antone wrote:Hot gases tend to rise so in the downdraft leg you would be pushing hot gases down. Not sure the riser can push this. It already strugles with a barrel without chimney.
But isn't the same thing happening with a bell system?
Hot gases tend to stagnate up top, and as these are cooling, they go down, and exit through the chimney. But because the volume of the bell is far bigger than heat riser and flue, the bell acts as a faster cooler than a downdraft channel, Reducing the hot plug effect. A updraft/downdraft channel acts as a siphon, more or less, where the bell having more surface doesn't do this effect as much. Gases, in the updraft/downdraft channel, have far less contact surface to cool down, hence stay hotter for a longer time, forming that hot plug, which doesn't happen in a bell. Theoretically this could happen in a bell, when all gases, and surrounding mass reach a steady state, being all at the same temp. But this can't happen as easily, as the bell's temperature exchange surface is bigger, and it's outer radiating surface is even bigger.