The selective inverted sink or SIS is a device used by

farmer A farmer is a person engaged in agriculture, raising living organisms for food or raw materials. The term usually applies to people who do some combination of raising field crops, orchards, vineyards, poultry, or other livestock. A farmer m ...

s to protect plants from frost, developed by

Uruguay Uruguay (; ), officially the Oriental Republic of Uruguay ( es, República Oriental del Uruguay), is a country in South America. It shares borders with Argentina to its west and southwest and Brazil to its north and northeast; while bordering ...

an Rafael Guarga in the late 1990s. The sink is actually a large fan housed in a chimney-like structure, and works by defeating surface temperature inversion. Cold air is denser than warm air, and will pool at ground level during calm weather. This lowers the surface temperature, even if the

ambient temperature Colloquially, "room temperature" is a range of air temperatures that most people prefer for indoor settings. It feels comfortable to a person when they are wearing typical indoor clothing. Human comfort can extend beyond this range depending on ...

is higher. Vents near the base of the chimney allow cold surface air to be pulled up through the chimney, creating a suction effect that draws warmer air down to surface level. The SIS is more efficient than typical ground-heaters, and is widely used to combat frost.

References

To blow up or down? Inverted sink fans offer alternative form of frost protection
by Paul Franson

US Patent 7654035 * ttps://web.archive.org/web/20111015231204/http://www.produccionnacional.com.uy/ciclos-tv/2011/frost-protection/ ''Su mercado es el mundo'' {{Tech-stub Uruguayan inventions Farming tools