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 heat, smoke, carbon dioxide, and water vapor. It was believed that this oil burning heater would help keep the orchard from cooling too much during the cold snaps.
In 1907, a young inventor, Willis Frederick Charles “W.C.” Scheu (Dec 1st, 1868 - April 11th, 1942), at that time in Grand Junction, Colorado, developed an oil-burning stack heater that was more effective than open fires in heating orchards and vineyards. [1] In 1911, he opened Scheu Manufacturing Company in Upland, California, and began producing a line of orchard heaters. [2] Scheu Steel is still in business, in 2021. [3] The use of smudge pots became widespread after a disastrous freeze in Southern California, January 4–8, 1913, wiped out a whole crop. [4] [5]
Smudge pots were commonly used for seven decades in areas such as California's numerous citrus groves and vineyards. The Redlands district had 462,000 orchard heaters for the winter of 1932–33, reported P. E. Simpson, of the supply department of the California Fruit Growers Exchange, requiring 3,693,000 gallons of oil for a single refilling, or about 330 tank car loads. To fill all of the smudge pots in Southern California one time required 2,000 car loads. [6]
Smudge pot use in Redlands, California groves continued into the 1970s, but fell out of favor as oil prices rose and environmental concerns increased. [7] Pots came in two major styles: a single louvered stack above a fuel oil-filled base, and a slightly taller version that featured a cambered, louvered, neck and a galvanized 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. The Return-Stack heater was developed by the University of California and became commercially available about 1940. [8] [9] Filler caps have a three- or four-hole flue control. The stem into the pot usually has a piece of oil-soaked wood ("down-draft tube and wick") [10] secured inside the neck to aid in lighting the pot. Pots are ignited when the air temperature reaches 29 degrees Fahrenheit (−2 degrees Celsius), and for each additional degree of drop, another hole is opened on the control cap ("draft regulator"). [10] Below 25 degrees, nothing more can be done to enhance the heating effects.
Some groves used natural gas pots on lines from a gas source, but these are not "smudge pots" in the usual sense, and they represented only a fraction of the smudging practice. Experiments using natural gas heaters were conducted in Rialto, California, in 1912. [11] Sometimes, large smudge pots are used for heating large open buildings, such as mechanics' workshops. In Australia they are called "choofers" because of the noise they make when lit: "choofa choofa choofa".
Lighting an Australian "choofer" is a tricky business. Because of the voluminous clouds of oily black smoke they produce when cold, they must be lit outside. This is accomplished by holding a burning rag next to the open damper on the fuel tank. The draught caused by the breeze passing through the chimney will draw air through the open damper into the fuel tank, where the surface of the fuel inside will light and burn instantly. Once the choofer is sufficiently warm, the damper may be closed until a steady rate of burning is attained, when the characteristic "choofa choofa choofa" noise is produced. If the damper is not closed, the choofa may choke itself with its own smoke, causing periodic "explosions" of unburnt gases in the chimney. Such explosions are not dangerous, but they are noisy and they produce a lot of smoke. Once the heater is burning hot enough, the smoke will disappear and the pot may be dragged slowly and carefully inside. They still produce dangerous gas, and must only be used in well-ventilated spaces.
Choofers will burn almost any combustible liquid fuel, including kerosene, diesel fuel, or used sump oil.
Prior to the development of battery-powered safety blinkers on saw-horses, many highway departments used small oil-burning safety pot markers to denote work zones, and many railroad systems still rely on oil-fired switch heaters, long tubs of fuel with a wick, that fits between the ties and keeps snow and ice from fouling the points of a switch. This is generally only used in yard applications. Mainline switches are usually heated by natural gas heaters.
The smudge pot was also used at construction sites and other cold places to take the chill out of buildings so workers would be comfortable, and for several decades (1920s–1970s) they were used as emergency night landing illumination at remote airfields without electric runway lights, acting as a series of small bonfires.
Smudge pots were used by the Germans, the Japanese, and the United States Navy during World War II, [12] and by the North Vietnamese in their invasions of Laos during the Vietnam War to protect valuable targets. [13] The oily black clouds of smoke produced from these smudge pots was intended to limit the ability to locate a target. In Vietnam, smoke from smudge pots was used as a defense against laser-guided bombs. Smoke would diffuse the laser beam and break the laser's connection with its intended target. [14]
Kerosene, or paraffin, is a combustible hydrocarbon liquid which is derived from petroleum. It is widely used as a fuel in aviation as well as households. Its name derives from Greek: κηρός (kērós) meaning "wax", and was registered as a trademark by Nova Scotia geologist and inventor Abraham Gesner in 1854 before evolving into a generic trademark. It is sometimes spelled kerosine in scientific and industrial usage.
A boiler is a closed vessel in which fluid is heated. The fluid does not necessarily boil. The heated or vaporized fluid exits the boiler for use in various processes or heating applications, including water heating, central heating, boiler-based power generation, cooking, and sanitation.
A kerosene lamp is a type of lighting device that uses kerosene as a fuel. Kerosene lamps have a wick or mantle as light source, protected by a glass chimney or globe; lamps may be used on a table, or hand-held lanterns may be used for portable lighting. Like oil lamps, they are useful for lighting without electricity, such as in regions without rural electrification, in electrified areas during power outages, at campsites, and on boats. There are three types of kerosene lamp: flat-wick, central-draft, and mantle lamp. Kerosene lanterns meant for portable use have a flat wick and are made in dead-flame, hot-blast, and cold-blast variants.
A furnace, referred to as a heater or boiler in British English, is an appliance used to generate heat for all or part of a building. Furnaces are mostly used as a major component of a central heating system. Furnaces are permanently installed to provide heat to an interior space through intermediary fluid movement, which may be air, steam, or hot water. Heating appliances that use steam or hot water as the fluid are normally referred to as a residential steam boilers or residential hot water boilers. The most common fuel source for modern furnaces in North America and much of Europe is natural gas; other common fuel sources include LPG, fuel oil, wood and in rare cases coal. In some areas electrical resistance heating is used, especially where the cost of electricity is low or the primary purpose is for air conditioning. Modern high-efficiency furnaces can be up to 98% efficient and operate without a chimney, with a typical gas furnace being about 80% efficient. Waste gas and heat are mechanically ventilated through either metal flue pipes or polyvinyl chloride (PVC) pipes that can be vented through the side or roof of the structure. Fuel efficiency in a gas furnace is measured in AFUE.
A chimney is an architectural ventilation structure made of masonry, clay or metal that isolates hot toxic exhaust gases or smoke produced by a boiler, stove, furnace, incinerator, or fireplace from human living areas. Chimneys are typically vertical, or as near as possible to vertical, to ensure that the gases flow smoothly, drawing air into the combustion in what is known as the stack, or chimney effect. The space inside a chimney is called the flue. Chimneys are adjacent to large industrial refineries, fossil fuel combustion facilities or part of buildings, steam locomotives and ships.
A thermostat is a regulating device component which senses the temperature of a physical system and performs actions so that the system's temperature is maintained near a desired setpoint.
A stove or range is a device that generates heat inside or on top of the device, for local heating or cooking. Stoves can be powered with many fuels, such as electricity, natural gas, gasoline, wood, and coal.
Wood fuel is a fuel such as firewood, charcoal, chips, sheets, pellets, and sawdust. The particular form used depends upon factors such as source, quantity, quality and application. In many areas, wood is the most easily available form of fuel, requiring no tools in the case of picking up dead wood, or few tools, although as in any industry, specialized tools, such as skidders and hydraulic wood splitters, have been developed to mechanize production. Sawmill waste and construction industry by-products also include various forms of lumber tailings.
A central heating system provides warmth to a number of spaces within a building from one main source of heat. It is a component of heating, ventilation, and air conditioning systems, which can both cool and warm interior spaces.
A fireplace or hearth is a structure made of brick, stone or metal designed to contain a fire. Fireplaces are used for the relaxing ambiance they create and for heating a room. Modern fireplaces vary in heat efficiency, depending on the design.
A flue is a duct, pipe, or opening in a chimney for conveying exhaust gases from a fireplace, furnace, water heater, boiler, or generator to the outdoors. Historically the term flue meant the chimney itself. In the United States, they are also known as vents for boilers and as breeching for water heaters and modern furnaces. They usually operate by buoyancy, also known as the stack effect, or the combustion products may be 'induced' via a blower. As combustion products contain carbon monoxide and other dangerous compounds, proper 'draft', and admission of replacement air is imperative. Building codes, and other standards, regulate their materials, design, and installation.
A pellet stove is a stove that burns compressed wood or biomass pellets to create a source of heat for residential and sometimes industrial spaces. By steadily feeding fuel from a storage container (hopper) into a burn pot area, it produces a constant flame that requires little to no physical adjustments. Today's central heating systems operated with wood pellets as a renewable energy source can reach an efficiency factor of more than 90%.
A masonry heater is a device for warming an interior space through radiant heating, by capturing the heat from periodic burning of fuel, and then radiating the heat at a fairly constant temperature for a long period. Masonry heaters covered in tile are called cocklestoves. The technology has existed in different forms, from back into the Neoglacial and Neolithic periods. Archaeological digs have revealed excavations of ancient inhabitants utilizing hot smoke from fires in their subterranean dwellings, to radiate into the living spaces. These early forms have evolved into modern systems.
A kerosene heater, also known as a paraffin heater, is typically a portable, unvented, kerosene-fueled, space heating device. In Japan and other countries, they are a primary source of home heat. In the United States and Australia, they are a supplemental heat or a source of emergency heat during a power outage. Most kerosene heaters produce between 3.3 and 6.8 kilowatts.
The stack effect or chimney effect is the movement of air into and out of buildings through unsealed openings, chimneys, flue-gas stacks, or other containers, resulting from air buoyancy. Buoyancy occurs due to a difference in indoor-to-outdoor air density resulting from temperature and moisture differences. The result is either a positive or negative buoyancy force. The greater the thermal difference and the height of the structure, the greater the buoyancy force, and thus the stack effect. The stack effect helps drive natural ventilation, air infiltration, and fires.
A convection heater is a type of heater that uses convection currents to heat and circulate air. These air currents flow throughout the body of the appliance and across its heating element. This process takes advantage of thermal conduction in order to heat the air, reducing its density relative to colder air and causing it to rise.
An oil heater, also known as an oil-filled heater, oil-filled radiator, or column heater, is a common form of convection heater used in domestic heating. Although filled with oil, it is electrically heated and does not involve burning any oil fuel; the oil is used as a heat reservoir (buffer).
A wood-burning stove is a heating or cooking appliance capable of burning wood fuel, often called solid fuel, and wood-derived biomass fuel, such as sawdust bricks. Generally the appliance consists of a solid metal closed firebox, often lined by fire brick, and one or more air controls. The first wood-burning stove was patented in Strasbourg in 1557. This was two centuries before the Industrial Revolution, so iron was still prohibitively expensive. The first wood-burning stoves were high-end consumer items and only gradually became used widely.
HVAC is a major sub discipline of mechanical engineering. The goal of HVAC design is to balance indoor environmental comfort with other factors such as installation cost, ease of maintenance, and energy efficiency. The discipline of HVAC includes a large number of specialized terms and acronyms, many of which are summarized in this glossary.