Also known as the stack effect, the tendency of heated
air or gas to rise in a duct or other vertical passage, as in a chimney,
small enclosure, or building, due to its lower density compared to the surrounding
air or gas.
The presence a chimney enhances the effect for several reasons:
- The lower effective section increases the air speed in the chimney;
this lowers the pressure in the chimney, creating a greater difference
in pressure with the rest of the interior space, thus accelerating the
air movement (Venturi effect).
- Being tall, the chimney increases the temperature difference between
the air intake and exhaust points, increasing the Venturi effect.
- Even a slight wind lowers the pressure at the chimney exhaust, and
consequently increases the efficiency of air extraction.
to fix a smoking stove or fireplace