A Stirling engine is a heat engine that operates by cyclic compression and expansion of air or other gas, the working fluid, at different temperature levels such that there is a net conversion of heat energy to mechanical work.
The engine is like a steam engine in that all of the engine's heat flows in and out through the engine wall. This is traditionally known as an external combustion engine in contrast to an internal combustion engine where the heat input is by combustion of a fuel within the body of the working fluid. Unlike the steam engine's use of water in both its liquid and gaseous phases as the working fluid, the Stirling engine encloses a fixed quantity of permanently gaseous fluid such as air or helium. As in all heat engines, the general cycle consists of compressing cool gas, heating the gas, expanding the hot gas, and finally cooling the gas before repeating the cycle.
Originally conceived in 1816 as an industrial prime mover to rival the steam engine, its practical use was largely confined to low-power domestic applications for over a century.The Stirling engine is noted for its high efficiency, quiet operation, and the ease with which it can utilize almost any heat source. This compatibility with alternative and renewable energy sources has become increasingly significant as the price of conventional fuels rises, and also in light of concerns such as peak oil and climate change. This engine is currently exciting interest as the core component of micro combined heat and power (CHP) units, in which it is more efficient and safer than a comparable steam engine. Widespread adoption of CHP could have a significant effect upon worldwide energy utilization
Wednesday, September 9, 2009
Inclined plane
This article is about the physical structure. For other uses, see Inclined plane (disambiguation).
Roman soldiers constructed an inclined plane out of earth to lay siege to the Masada during the First Jewish-Roman War in 73 CE
The inclined plane is one of the original six simple machines; as the name suggests, it is a flat surface whose endpoints are at different heights. By moving an object up an inclined plane rather than completely vertical, the amount of force required is reduced, at the expense of increasing the distance the object must travel. The mechanical advantage of an inclined plane is the ratio of the length of the sloped surface to the height it spans; this may also be expressed as the cosecant of the angle between the plane and the horizontal. Note that due to the conservation of energy, the same amount of mechanical energy is required to lift a given object by a given distance, except for losses from friction, but the inclined plane allows the same work to be done with a smaller force exerted over a greater distance.
Roman soldiers constructed an inclined plane out of earth to lay siege to the Masada during the First Jewish-Roman War in 73 CE
The inclined plane is one of the original six simple machines; as the name suggests, it is a flat surface whose endpoints are at different heights. By moving an object up an inclined plane rather than completely vertical, the amount of force required is reduced, at the expense of increasing the distance the object must travel. The mechanical advantage of an inclined plane is the ratio of the length of the sloped surface to the height it spans; this may also be expressed as the cosecant of the angle between the plane and the horizontal. Note that due to the conservation of energy, the same amount of mechanical energy is required to lift a given object by a given distance, except for losses from friction, but the inclined plane allows the same work to be done with a smaller force exerted over a greater distance.
Vacuum pump
A vacuum pump is a device that removes gas molecules from a sealed volume in order to leave behind a partial vacuum. The vacuum pump was invented in 1650 by Otto von Guericke.
Wing
A wing is a surface used to produce lift for flight through the air or another gaseous or fluid medium. The wing shape is usually an airfoil. The word originally referred only to the foremost limbs of birds, but has been extended to include the wings of insects (see insect wing), bats, pterosaurs, and aircraft.
A wing's aerodynamic quality is expressed as a Lift-to-drag ratio. The lift generated by a wing at a given speed and angle of attack can be 1-2 orders of magnitude greater than the drag. This means that a significantly smaller thrust force can be applied to propel the wing through the air in order to obtain a specified lift.
A wing's aerodynamic quality is expressed as a Lift-to-drag ratio. The lift generated by a wing at a given speed and angle of attack can be 1-2 orders of magnitude greater than the drag. This means that a significantly smaller thrust force can be applied to propel the wing through the air in order to obtain a specified lift.
checkweigher
A checkweigher is an automatic machine for checking the weight of packaged commodities. It is normally found at the offgoing end of a production process and is used to ensure that the weight of a pack of the commodity is within specified limits. Any packs that are outside the tolerance are taken out of line automatically.
A checkweigher can weigh in excess of 500 items per minute. ( depending on carton size and accuracy requirements)
Checkweighers often incorporate additional checking devices such as metal detectors and X-ray machines to enable other attributes of the pack to be checked and acted upon accordingly.
A checkweigher can weigh in excess of 500 items per minute. ( depending on carton size and accuracy requirements)
Checkweighers often incorporate additional checking devices such as metal detectors and X-ray machines to enable other attributes of the pack to be checked and acted upon accordingly.
VENDING MACHINE
A vending machine provides snacks, beverages, and other products to consumers without a cashier. Items sold via these machines vary by country and region.
In some countries, merchants may sell alcoholic beverages such as beer through vending machines, while other countries do not allow this practice (usually because of dram shop laws).
In some countries, merchants may sell alcoholic beverages such as beer through vending machines, while other countries do not allow this practice (usually because of dram shop laws).
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