|
Atkinson Resistance
Atkinson resistance is commonly used in mine ventilation to characterise the resistance to airflow of a duct of irregular size and shape, such as a mine roadway. It has the symbol R and is used in the square law for pressure drop, :\Delta P = \fracRQ^2 where (in English units) * \Delta P is pressure drop (pounds per square foot), * \rho_ is the air density in the duct (pounds per cubic foot), * \rho_ is the standard air density (0.075 pound per cubic foot), * R is the resistance (atkinsons), * Q is the rate of flow of air (thousands of cubic feet per second). One atkinson is defined as the resistance of an airway which, when air flows along it at a rate of 1,000 cubic feet per second, causes a pressure drop of one pound-force per square foot. The unit is named after J J Atkinson, who published one of the earliest comprehensive mathematical treatments of mine ventilation. Atkinson based his expressions for airflow resistance on the more general work of Chézy and Dar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Underground Mine Ventilation
Underground mine ventilation provides a flow of air to the underground workings of a mine of sufficient volume to dilute and remove dust and noxious gases (typically NOx, SO2, methane, CO2 and CO) and to regulate temperature. The source of these gases are equipment that runs on diesel engines, blasting with explosives, and the orebody itself. The largest component of the operating cost for mine ventilation is electricity to power the ventilation fans, which may account for one third of a typical underground mine's entire electrical power cost. Types of ventilation Flow-through ventilation is the main ventilation circuit for the mine. Air enters the mine from surface via a shaft, ventilation raise or adit. The air is distributed through the mine via internal ventilation raises and ramps, and flows are controlled by regulators and permanently mounted ventilation fans. An auxiliary ventilation system takes air from the flow-through system and distributes it to the mine w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
English Units
English units are the units of measurement used in England up to 1826 (when they were replaced by Imperial units), which evolved as a combination of the Anglo-Saxon and Roman systems of units. Various standards have applied to English units at different times, in different places, and for different applications. Use of the term "English units" can be ambiguous, as, in addition to the meaning used in this article, it is sometimes used to refer to the units of the descendent Imperial system as well to those of the descendant system of United States customary units. The two main sets of English units were the Winchester Units, used from 1495 to 1587, as affirmed by King Henry VII, and the Exchequer Standards, in use from 1588 to 1825, as defined by Queen Elizabeth I. In England (and the British Empire), English units were replaced by Imperial units in 1824 (effective 1 January 1826) by a Weights and Measures Act, which retained many though not all of the unit names and redefin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Air Density
The density of air or atmospheric density, denoted '' ρ'', is the mass per unit volume of Earth's atmosphere. Air density, like air pressure, decreases with increasing altitude. It also changes with variation in atmospheric pressure, temperature and humidity. At 101.325 kPa (abs) and 20 °C (68 °F), air has a density of approximately , according to the International Standard Atmosphere (ISA). At 101.325kPa (abs) and , air has a density of approximately , which is about that of water, according to the International Standard Atmosphere (ISA). Pure liquid water is . Air density is a property used in many branches of science, engineering, and industry, including aeronautics;Olson, Wayne M. (2000) AFFTC-TIH-99-01, Aircraft Performance FlightICAO, Manual of the ICAO Standard Atmosphere (extended to 80 kilometres (262 500 feet)), Doc 7488-CD, Third Edition, 1993, .Grigorie, T.L., Dinca, L., Corcau J-I. and Grigorie, O. (2010) Aircrafts' Altitude Measurement Using Pressure Information:Ba ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pound-force
The pound of force or pound-force (symbol: lbf, sometimes lbf,) is a unit of force used in some systems of measurement, including English Engineering units and the foot–pound–second system. Pound-force should not be confused with pound-mass (lb), often simply called ''pound'', which is a unit of mass, nor should these be confused with foot-pound (ft⋅lbf), a unit of energy, or pound-foot (lbf⋅ft), a unit of torque. Definitions The pound-force is equal to the gravitational force exerted on a mass of one avoirdupois pound on the surface of Earth. Since the 18th century, the unit has been used in low-precision measurements, for which small changes in Earth's gravity (which varies from equator to pole by up to half a percent) can safely be neglected. The 20th century, however, brought the need for a more precise definition, requiring a standardized value for acceleration due to gravity. Product of avoirdupois pound and standard gravity The pound-force is the product ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antoine De Chézy
Antoine de Chézy (September 1, 1718 – October 5, 1798), also called Antoine Chézy, was a French physicist and hydraulics engineer who contributed greatly to the study of fluid mechanics and designed a canal for the Paris water supply. He is known for developing a similarity parameter for predicting the flow characteristics of one channel based on the measurements of another, known today as the Chézy Formula or the Chézy Equation. The Chézy Equation is a pioneering formula in the field of fluid mechanics, and was expanded and modified by Irish engineer Robert Manning in 1889 as the Manning formula. The Chézy Formula concerns the velocity of water flowing through conduits and is widely celebrated for its use in open channel flow calculations. By the definition of open channel, the Chézy formula also applies to partially-full pipe flow. Chézy was born September 1, 1718 in Châlons-en-Champagne, France. Chézy graduated with honors from the Ecole des Ponts et Chaussé ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Henry Darcy
Henry Philibert Gaspard Darcy (, 10 June 1803 – 3 January 1858) was a French engineer who made several important contributions to hydraulics, including Darcy’s law for flow in porous media. Early life Darcy was born in Dijon, France, on June 10, 1803. His first given name is ''Henry''; although the French spelling ''Henri'' appears in multiple sources such as necrological notices, Darcy used the Anglicized spelling. Despite his father's death in 1817 when he was 14, his mother was able to borrow money to pay for his tutors. In 1821 he enrolled at the ''École Polytechnique'' (Polytechnic School) in Paris, and transferred two years later to the School of Bridges and Roads, which led to employment in the Corps of Bridges and Roads. Darcy met an English woman, Henriette Carey, whose family had been living in Dijon, and married her in 1828. Engineering career As a member of the Corps, he built an adequate pressurized water distribution system in Dijon following the failur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fanning Friction Factor
The Fanning friction factor, named after John Thomas Fanning, is a dimensionless number used as a local parameter in continuum mechanics calculations. It is defined as the ratio between the local shear stress and the local flow kinetic energy density: : f = \frac where: *f is the local Fanning friction factor (dimensionless) *\tau is the local shear stress (unit in \frac or \frac or Pa) *u is the bulk flow velocity (unit in \frac or \frac) *\rho is the density of the fluid (unit in \frac or \frac) In particular the shear stress at the wall can, in turn, be related to the pressure loss by multiplying the wall shear stress by the wall area ( 2 \pi R L for a pipe with circular cross section) and dividing by the cross-sectional flow area ( \pi R^2 for a pipe with circular cross section). Thus \Delta P = f \frac \rho u^2 Fanning friction factor formula This friction factor is one-fourth of the Darcy friction factor, so attention must be paid to note which one of these is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Watt
The watt (symbol: W) is the unit of power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m2⋅s−3. It is used to quantify the rate of energy transfer. The watt is named after James Watt (1736–1819), an 18th-century Scottish inventor, mechanical engineer, and chemist who improved the Newcomen engine with his own steam engine in 1776. Watt's invention was fundamental for the Industrial Revolution. Overview When an object's velocity is held constant at one metre per second against a constant opposing force of one newton, the rate at which work is done is one watt. : \mathrm In terms of electromagnetism, one watt is the rate at which electrical work is performed when a current of one ampere (A) flows across an electrical potential difference of one volt (V), meaning the watt is equivalent to the volt-ampere (the latter unit, however, is used for a different quantity from the real power of an electrical circuit). : ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Manning Formula
The Manning formula or Manning's equation is an empirical formula estimating the average velocity of a liquid flowing in a conduit that does not completely enclose the liquid, i.e., open channel flow. However, this equation is also used for calculation of flow variables in case of flow in partially full conduits, as they also possess a free surface like that of open channel flow. All flow in so-called open channels is driven by gravity. It was first presented by the French engineer in 1867, and later re-developed by the Irish engineer Robert Manning in 1890. Thus, the formula is also known in Europe as the Gauckler–Manning formula or Gauckler–Manning–Strickler formula (after ). The Gauckler–Manning formula is used to estimate the average velocity of water flowing in an open channel in locations where it is not practical to construct a weir or flume to measure flow with greater accuracy. Manning's equation is also commonly used as part of a numerical step method, such as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydraulic Diameter
The hydraulic diameter, , is a commonly used term when handling flow in non-circular tubes and channels. Using this term, one can calculate many things in the same way as for a round tube. When the cross-section is uniform along the tube or channel length, it is defined as : D_\text = \frac, where : is the cross-sectional area of the flow, : is the wetted perimeter of the cross-section. More intuitively, the hydraulic diameter can be understood as a function of the hydraulic radius , which is defined as the cross-sectional area of the channel divided by the wetted perimeter. Here, the wetted perimeter includes all surfaces acted upon by shear stress from the fluid. : R_\text = \frac, : D_\text = 4R_\text, Note that for the case of a circular pipe, : D_\text =\frac=2R The need for the hydraulic diameter arises due to the use of a single dimension in case of dimensionless quantity such as Reynolds number, which prefer a single variable for flow analysis rather than the set of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Darcy Friction Factor
Darcy, Darci or Darcey may refer to: Science * Darcy's law, which describes the flow of a fluid through porous material * Darcy (unit), a unit of permeability of fluids in porous material * Darcy friction factor in the field of fluid mechanics * Darcy–Weisbach equation used in hydraulics for calculation of the head loss due to friction People * Darcy (surname), a surname (including a list of people with the name) Men * Darcy Blake (born 1988), Welsh footballer * Darcy Dallas (born 1972), Canadian ice hockey defenceman * Darcy Daniher (born 1989), Australian rules footballer * Darci Frigo, Brazilian activist * Darcy Furber, Canadian politician * Darcy Gardiner (born 1995), Australian rules footballer * Darcy Hordichuk (born 1980), professional ice hockey player * Darcy Kuemper (born 1990), professional ice hockey player * Darcy Lang (born 1995), Australian rules footballer * Darcy Lear (1898–1967), Australian rules footballer * Darcy Lussick (born 1989), Australian rugby ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atkinson Friction Factor
Atkinson friction factor is a measure of the resistance to airflow of a duct. It is widely used in the mine ventilation industry but is rarely referred to outside of it. Atkinson friction factor is represented by the symbol k and has the same units as air density (kilograms per cubic metre in SI units, lbfmin^2/ft^4 in Imperial units). It is related to the more widespread Fanning friction factor by k = \frac\rho f, in which \rho is the density of air in the shaft or roadway under consideration and f is Fanning friction factor (dimensionless). It is related to the Darcy friction factor by k = \frac\rho \frac{4}, in which \lambda is the Darcy friction factor (dimensionless). It was introduced by John J Atkinson in an early mathematical treatment of mine ventilation (1862) and has been known under his name ever since. See also * Atkinson resistance Atkinson resistance is commonly used in mine ventilation to characterise the resistance to airflow of a duct of ir ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
