Thursday, July 03, 2014

Word of the Day -- Smudge Pot

A smudge pot (also known as a choofa or orchard heater) is an oil-burning device used to prevent frost on fruit trees. Usually a smudge pot has a large round base with a chimney coming out of the middle of the base. The smudge pot is placed between trees in an orchard. The burning oil creates (Low clouds can have a similar "infrared blanket" effect, which is why cloudy nights tend to be warmer than clear-sky nights.) some heat, but more importantly, a large amount of smoke, particulates, carbon dioxide, and water vapor. This artificial smog forms a "blanket" that blocks infrared light, thereby preventing radiative cooling that would otherwise cause or worsen frost.

Smudge pots were developed after a disastrous freeze in Southern California in January 1913 wiped out a whole crop.

Smudge pots were used in Redlands, California groves continued into the 1970s, but fell out of favor as oil prices rose and environmental concerns increased. Pots came in two major styles: a single stack above a fuel oil-filled base, and a slightly taller version that featured a cambered neck and a re-breather feed pipe out of the side of the chimney that siphoned stack gas back into the burn chamber and produced more complete combustion. Filler caps have a three- or four-hole flue control. The stem into the pot usually has a piece of oil-soaked wood secured inside the neck to aid in lighting the pot. Pots are ignited when the air temperature reaches 29 degrees Fahrenheit (-2 Celsius), and for each additional degree of drop, another hole is opened on the control cap. Below 25 degrees, nothing more can be done to enhance the heating effects.

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