نحوه کارکرد دستگاه سانتریفیوژ
نحوه کارکرد دستگاه سانتریفیوژ
از دوستان اگه مقاله ای زیبا و جالب در مورد دستگاه سانتریفیوژ و نحوه کارکرد آن و همچنین قوانین فیزیکی کاربردی در آن (یعنی معادلات و فرمول های ریاضی در ساخت و راه اندازی، قوانین گشتاور و ... ) اگه دارن برام بزارن. هم به صورت pdf و هم به صورت word. بشتابید خیلی خیلی ضروریه و عجله دارم تا ساعت 8.
Re: نحوه کارکرد دستگاه سانتریفیوژ
الله اکبر، کسی پیدا نکرد؟؟؟؟؟!!!!!!
فروش دامنه ی Hupaa.ir.برای تماس به وبسایت Hupaa.ir بایید.
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AliHagigat
عضویت : شنبه ۱۳۸۷/۹/۹ - ۱۰:۵۹
پست: 505-
سپاس: 6
Re: نحوه کارکرد دستگاه سانتریفیوژ
اگر فهمیدید ممکنه لطفاً خلاصهٔ کار دستگاه رو شرح بدین؟ ذرات رو چه جوری جدا میکنه؟
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4Duniverse
عضویت : جمعه ۱۳۸۶/۶/۲ - ۲۱:۰۷
پست: 1412-
سپاس: 6
Re: نحوه کارکرد دستگاه سانتریفیوژ
سانتریفوژ یا دستگاه مرکزگریز دستگاهی است که در آن با استفاده از نیروی گریز از مرکز مواد را از یکدیگر جدا می‌کنند. در این دستگاه محفظه‌ای که مواد جداشدنی در آن قراردارد معمولاً به کمک یک موتور به سرعت حول یک محور می‌چرخد.
سانتریفوژ دستگاهی است که از آن برای چرخاندن مواد با سرعت بالا استفاده می‌شود. دانشمندان معمولاً دستگاه سانتریفوژ را برای جدا کردن ذرات جامد از یک مایع یا تقسیم مخلوط مایعات به اجزای مختلف آن به کار می‌گیرند. مخلوط را درون لوله‌ای قرار می‌دهند که طوری قرار داده شده‌است که با چرخش دستگاه، به سمت خارج از مرکز حرکت میکند و به حالت افقی قرار می‌گیرند. در این حالت، نیروی گریز از مرکز می‌خواهد که مخلوط را برخلاف مرکز سانتریفوژ براندو از این نقطه دور کند و ذرات یا مایع سنگین تر بیش تر به سمت بیرون (یا ته مخلوط) رانده می‌شوند. وقتی سانتریفوژ از حرکت باز می‌ایستد، مواد به همین حالت غیر مخلوط می‌مانند. خون و سایر نمونه‌های بیولوژیکی را معمولاً به وسیله دستگاه سانتریفوژ جدا می‌کنند. سریع ترین سانتریفوژ با نام «فرامرکز گریز» با سرعت ۲۰۰۰۰۰ دور در دقیقه می‌چرخد. از دستگاههای گریز از مرکز بزرگ برای انجام آزمایش بر روی خلبانان نظامی و فضانوردان استفاده می‌شود تا میزان مقاومت آنان در شتاب‌های بالا معلوم شود.
انواع دستگاههای مرکز گریز برای مصارف گوناگون ساخته شده‌است. نمونه‌های خانگی این دستگاه برای جداکردن آب از سبزی‌ها مثل کاهو و غیره بکار می‌رود. در نمونه‌های آزمایشگاهی برای جداکردن گلوبول‌های خون از پلاسما استفاده می‌شود. دستگاههای صنعتی با موتورهای قوی و در ابعاد بزرگ برای جدا کردن مواد بکار می‌رود. در کار غنی‌سازی اورانیوم نیز از دستگاههای مرکزگریز گازی استفاده می‌شود.
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سانتریفوژ دستگاهی است که از آن برای چرخاندن مواد با سرعت بالا استفاده می‌شود. دانشمندان معمولاً دستگاه سانتریفوژ را برای جدا کردن ذرات جامد از یک مایع یا تقسیم مخلوط مایعات به اجزای مختلف آن به کار می‌گیرند. مخلوط را درون لوله‌ای قرار می‌دهند که طوری قرار داده شده‌است که با چرخش دستگاه، به سمت خارج از مرکز حرکت میکند و به حالت افقی قرار می‌گیرند. در این حالت، نیروی گریز از مرکز می‌خواهد که مخلوط را برخلاف مرکز سانتریفوژ براندو از این نقطه دور کند و ذرات یا مایع سنگین تر بیش تر به سمت بیرون (یا ته مخلوط) رانده می‌شوند. وقتی سانتریفوژ از حرکت باز می‌ایستد، مواد به همین حالت غیر مخلوط می‌مانند. خون و سایر نمونه‌های بیولوژیکی را معمولاً به وسیله دستگاه سانتریفوژ جدا می‌کنند. سریع ترین سانتریفوژ با نام «فرامرکز گریز» با سرعت ۲۰۰۰۰۰ دور در دقیقه می‌چرخد. از دستگاههای گریز از مرکز بزرگ برای انجام آزمایش بر روی خلبانان نظامی و فضانوردان استفاده می‌شود تا میزان مقاومت آنان در شتاب‌های بالا معلوم شود.
انواع دستگاههای مرکز گریز برای مصارف گوناگون ساخته شده‌است. نمونه‌های خانگی این دستگاه برای جداکردن آب از سبزی‌ها مثل کاهو و غیره بکار می‌رود. در نمونه‌های آزمایشگاهی برای جداکردن گلوبول‌های خون از پلاسما استفاده می‌شود. دستگاههای صنعتی با موتورهای قوی و در ابعاد بزرگ برای جدا کردن مواد بکار می‌رود. در کار غنی‌سازی اورانیوم نیز از دستگاههای مرکزگریز گازی استفاده می‌شود.
یک دستگاه سانتریفوژ مایع آزمایشگاهی
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A centrifuge is a piece of equipment, generally driven by a motor, that puts an object in rotation around a fixed axis, applying a force perpendicular to the axis. The centrifuge works using the sedimentation principle, where the centripetal acceleration is used to evenly distribute substances (usually present in a solution for small scale applications) of greater and lesser density. There are many different kinds of centrifuges, including those for very specialized purposes. It can be used for viable counts, when shaking the culture e.g. yeast, out of suspension.
Theory
Protocols for centrifugation typically specify the amount of acceleration to be applied to the sample, rather than specifying a rotational speed such as revolutions per minute. The acceleration is often quoted in multiples of g, the standard acceleration due to gravity at the Earth's surface. This distinction is important because two rotors with different diameters running at the same rotational speed will subject samples to different accelerations.
The acceleration can be calculated as the product of the radius and the square of the angular velocity.
History and predecessors
English military engineer Benjamin Robins (1707-1751) invented a whirling arm apparatus to determine drag. In 1864, Antonin Prandtl invented the first dairy centrifuge in order to separate cream from milk. In 1879, Gustaf de Laval demonstrated the first continuous centrifugal separator, making its commercial application feasible.
Types
There are at least five types of centrifuge:
preparative centrifuge
analytical centrifuge
angle fixed centrifuge
swing head centrifuge
haemacrotic centrifuge]]
Industrial centrifuges may otherwise be classified according to the type of separation of the high density fraction from the low density one :
Screen centrifuges, where the centrifugal acceleration allows the liquid to pass through a screen of some sort, through which the solids cannot go (due to granulometry larger than the screen gap or due to agglomeration). Common types are :
Pusher centrifuges
Peeler centrifuges
Decanter centrifuges, in which there is no physical separation between the solid and liquid phase, rather an accelerated settling due to centrifugal acceleration. Common types are :
Solid bowl centrifuges
Conical plate centrifuges
Uses
Isolating suspensions
Simple centrifuges are used in chemistry, biology, and biochemistry for isolating and separating suspensions. They vary widely in speed and capacity. They usually comprise a rotor containing two, four, six, or many more numbered wells within which the samples containing centrifuge tips may be placed.
Isotope separation
Other centrifuges, the first being the Zippe-type centrifuge, separate isotopes, and these kinds of centrifuges are in use in nuclear power and nuclear weapon programs.
Gas centrifuges are used in uranium enrichment. The heavier isotope of uranium (uranium-238) in the uranium hexafluoride gas tend to concentrate at the walls of the centrifuge as it spins, while the desired uranium-235 isotope is extracted and concentrated with a scoop selectively placed inside the centrifuge. It takes many thousands of centrifuges to enrich uranium enough for use in a nuclear reactor (around 3.5% enrichment), and many thousands more to enrich it to weapons-grade (around 90% enrichment) for use in nuclear weapons.
Aeronautics and astronautics
Human centrifuges are exceptionally large centrifuges that test the reactions and tolerance of pilots and astronauts to acceleration above those experienced in the Earth's gravity.
The US Air Force at Holloman Air Force Base, NM operates a human centrifuge. The centrifuge at Holloman AFB is operated by the aerospace physiology department for the purpose of training and evaluating prospective fighter pilots for high-g flight in Air Force fighter aircraft. It is important to note that the centrifuge at Holloman AFB is unrealistic in that it is far more difficult for a pilot to tolerate the high-g environment in the centrifuge than in a real fighter aircraft. This well-known fact is based on countless accounts from experienced operational fighter pilots.[citation needed]
The use of large centrifuges to simulate a feeling of gravity has been proposed for future long-duration space missions. Exposure to this simulated gravity would prevent or reduce the bone decalcification and muscle atrophy that affect individuals exposed to long periods of freefall. An example of this can be seen in the film 2001: A Space Odyssey, while the James Bond film Moonraker shows an astronaut-training centrifuge in action on earth (albeit sabotaged with murderous intent).
Earthquake and blast simulation
The geotechnical centrifuge is used for simulating blasts and earthquake phenomena.[1] For a discussion of their design, see Geotechnical Centrifuges by Philip Turner
Commercial applications
Standalone centrifuges for drying (hand-washed) clothes - usually with a water outlet.
Centrifuges are used in the attraction Mission: SPACE, located at Epcot in Walt Disney World, which propels riders using a combination of a centrifuge and a motion simulator to simulate the feeling of going into space.
In soil mechanics, centrifuges utilize centrifugal acceleration to match soil stresses in a scale model to those found in reality.
Large industrial centrifuges are commonly used in water and wastewater treatment to dry sludges. The resulting dry product is often termed cake, and the water leaving a centrifuge after most of the solids have been removed is called centrate.
Large industrial centrifuges are also used in the oil industry to remove solids from the drilling fluid.
Disc-stack centrifuges used by some companies in Oil Sands industry to separate small amounts of water and solids from bitumen before it's sent to Upgrading.
Calculating relative centrifugal force (RCF)
Relative centrifugal force is the measurement of the force applied to a sample within a centrifuge. This can be calculated from the speed (RPM) and the rotational radius (cm) using the following calculation.
where
g = Relative centrifuge force
r = rotational radius (centimetres, cm)
N = rotating speed (revolutions per minute, r/min)
Theory
Protocols for centrifugation typically specify the amount of acceleration to be applied to the sample, rather than specifying a rotational speed such as revolutions per minute. The acceleration is often quoted in multiples of g, the standard acceleration due to gravity at the Earth's surface. This distinction is important because two rotors with different diameters running at the same rotational speed will subject samples to different accelerations.
The acceleration can be calculated as the product of the radius and the square of the angular velocity.
History and predecessors
English military engineer Benjamin Robins (1707-1751) invented a whirling arm apparatus to determine drag. In 1864, Antonin Prandtl invented the first dairy centrifuge in order to separate cream from milk. In 1879, Gustaf de Laval demonstrated the first continuous centrifugal separator, making its commercial application feasible.
Types
There are at least five types of centrifuge:
preparative centrifuge
analytical centrifuge
angle fixed centrifuge
swing head centrifuge
haemacrotic centrifuge]]
Industrial centrifuges may otherwise be classified according to the type of separation of the high density fraction from the low density one :
Screen centrifuges, where the centrifugal acceleration allows the liquid to pass through a screen of some sort, through which the solids cannot go (due to granulometry larger than the screen gap or due to agglomeration). Common types are :
Pusher centrifuges
Peeler centrifuges
Decanter centrifuges, in which there is no physical separation between the solid and liquid phase, rather an accelerated settling due to centrifugal acceleration. Common types are :
Solid bowl centrifuges
Conical plate centrifuges
Uses
Isolating suspensions
Simple centrifuges are used in chemistry, biology, and biochemistry for isolating and separating suspensions. They vary widely in speed and capacity. They usually comprise a rotor containing two, four, six, or many more numbered wells within which the samples containing centrifuge tips may be placed.
Isotope separation
Other centrifuges, the first being the Zippe-type centrifuge, separate isotopes, and these kinds of centrifuges are in use in nuclear power and nuclear weapon programs.
Gas centrifuges are used in uranium enrichment. The heavier isotope of uranium (uranium-238) in the uranium hexafluoride gas tend to concentrate at the walls of the centrifuge as it spins, while the desired uranium-235 isotope is extracted and concentrated with a scoop selectively placed inside the centrifuge. It takes many thousands of centrifuges to enrich uranium enough for use in a nuclear reactor (around 3.5% enrichment), and many thousands more to enrich it to weapons-grade (around 90% enrichment) for use in nuclear weapons.
Aeronautics and astronautics
Human centrifuges are exceptionally large centrifuges that test the reactions and tolerance of pilots and astronauts to acceleration above those experienced in the Earth's gravity.
The US Air Force at Holloman Air Force Base, NM operates a human centrifuge. The centrifuge at Holloman AFB is operated by the aerospace physiology department for the purpose of training and evaluating prospective fighter pilots for high-g flight in Air Force fighter aircraft. It is important to note that the centrifuge at Holloman AFB is unrealistic in that it is far more difficult for a pilot to tolerate the high-g environment in the centrifuge than in a real fighter aircraft. This well-known fact is based on countless accounts from experienced operational fighter pilots.[citation needed]
The use of large centrifuges to simulate a feeling of gravity has been proposed for future long-duration space missions. Exposure to this simulated gravity would prevent or reduce the bone decalcification and muscle atrophy that affect individuals exposed to long periods of freefall. An example of this can be seen in the film 2001: A Space Odyssey, while the James Bond film Moonraker shows an astronaut-training centrifuge in action on earth (albeit sabotaged with murderous intent).
Earthquake and blast simulation
The geotechnical centrifuge is used for simulating blasts and earthquake phenomena.[1] For a discussion of their design, see Geotechnical Centrifuges by Philip Turner
Commercial applications
Standalone centrifuges for drying (hand-washed) clothes - usually with a water outlet.
Centrifuges are used in the attraction Mission: SPACE, located at Epcot in Walt Disney World, which propels riders using a combination of a centrifuge and a motion simulator to simulate the feeling of going into space.
In soil mechanics, centrifuges utilize centrifugal acceleration to match soil stresses in a scale model to those found in reality.
Large industrial centrifuges are commonly used in water and wastewater treatment to dry sludges. The resulting dry product is often termed cake, and the water leaving a centrifuge after most of the solids have been removed is called centrate.
Large industrial centrifuges are also used in the oil industry to remove solids from the drilling fluid.
Disc-stack centrifuges used by some companies in Oil Sands industry to separate small amounts of water and solids from bitumen before it's sent to Upgrading.
Calculating relative centrifugal force (RCF)
Relative centrifugal force is the measurement of the force applied to a sample within a centrifuge. This can be calculated from the speed (RPM) and the rotational radius (cm) using the following calculation.
where
g = Relative centrifuge force
r = rotational radius (centimetres, cm)
N = rotating speed (revolutions per minute, r/min)
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Uranium is an element that is similar to iron. Like iron, you dig uranium ore out of the ground and then process it to extract the pure uranium from the ore. When you finish processing uranium ore, what you have is uranium oxide. Uranium oxide contains two types (or isotopes) of uranium: U-235 and U-238. U-235 is what you need if you want to make a bomb or fuel a nuclear power plant. But the uranium oxide from the mine is about 99 percent U-238. So you need to somehow separate the U-235 from the U-238 and increase the amount of U-235. The process of concentrating the U-235 is called enrichment, and centrifuges are a central part of the process.
Uranium centrifuge cascades
-235 weighs slightly less than U-238. By exploiting this weight difference, you can separate the U-235 and the U-238. The first step is to react the uranium with hydrofluoric acid, an extremely powerful acid. After several steps, you create the gas uranium hexafluoride.
Now that the uranium is in a gaseous form, it is easier to work with. You can put the gas into a centrifuge and spin it up. The centrifuge creates a force thousands of times more powerful than the force of gravity. Because the U-238 atoms are slightly heavier than the U-235 atoms, they tend to move out toward the walls of the centrifuge. The U-235 atoms tend to stay more toward the center of the centrifuge.
Although it is only a slight difference in concentrations, when you extract the gas from the center of the centrifuge, it has slightly more U-235 than it did before. You place this slightly concentrated gas in another centrifuge and do the same thing. If you do this thousands of times, you can create a gas that is highly enriched in U-235. At a uranium enrichment plant, thousands of centrifuges are chained together in long cascades.
At the end of a long chain of centrifuges, you have uranium hexafluoride gas containing a high concentration of U-235 atoms.
The creation of the centrifuges is a huge technological challenge. The centrifuges must spin very quickly -- in the range of 100,000 rpm. To spin this fast, the centrifuges must have:
very light, yet strong, rotors
well-balanced rotors
high-speed bearings, usually magnetic to reduce friction
Meeting all three of these requirements has been out of reach for most countries. The recent development of inexpensive, high-precision computer-controlled machining equipment has made things somewhat easier. This is why more countries are learning to enrich uranium in recent years.
Now you need to turn the uranium hexafluoride gas back into uranium metal. You do this by adding calcium. The calcium reacts with the fluoride to create a salt, and the pure uranium metal is left behind. With this highly concentrated U-235 metal, you can either make a nuclear bomb or power a nuclear reactor.
Now that the uranium is in a gaseous form, it is easier to work with. You can put the gas into a centrifuge and spin it up. The centrifuge creates a force thousands of times more powerful than the force of gravity. Because the U-238 atoms are slightly heavier than the U-235 atoms, they tend to move out toward the walls of the centrifuge. The U-235 atoms tend to stay more toward the center of the centrifuge.
Although it is only a slight difference in concentrations, when you extract the gas from the center of the centrifuge, it has slightly more U-235 than it did before. You place this slightly concentrated gas in another centrifuge and do the same thing. If you do this thousands of times, you can create a gas that is highly enriched in U-235. At a uranium enrichment plant, thousands of centrifuges are chained together in long cascades.
At the end of a long chain of centrifuges, you have uranium hexafluoride gas containing a high concentration of U-235 atoms.
The creation of the centrifuges is a huge technological challenge. The centrifuges must spin very quickly -- in the range of 100,000 rpm. To spin this fast, the centrifuges must have:
very light, yet strong, rotors
well-balanced rotors
high-speed bearings, usually magnetic to reduce friction
Meeting all three of these requirements has been out of reach for most countries. The recent development of inexpensive, high-precision computer-controlled machining equipment has made things somewhat easier. This is why more countries are learning to enrich uranium in recent years.
Now you need to turn the uranium hexafluoride gas back into uranium metal. You do this by adding calcium. The calcium reacts with the fluoride to create a salt, and the pure uranium metal is left behind. With this highly concentrated U-235 metal, you can either make a nuclear bomb or power a nuclear reactor.
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Centrifuges are very useful tools in today’s world. You might not know it, but almost everyone has a centrifuge at home – clothes washing machine. When you visit the doctor and take a blood test, a centrifuge is used to determine the results at a lab. Other uses of centrifuges are during the rides in an amusement park, and testing equipment for astronauts to test gravitational forces on the human body. Centrifuges are even used in nuclear and experimental research by scientists in large institutions and research centers.
The Concept
The concept behind how a centrifuge works is pretty simple. A centrifuge includes a compartment which spins around an axis. The compartment is usually driven by a motor and can travel very quickly, revolving hundreds to thousands of times around the axis in a minute. The speed of a centrifuge is measured by RPMs (revolutions per minute). While small centrifuges have extremely high RPMs, larger centrifuges like those used by astronauts to test g-forces have much slower RPMs due to the distance they must travel around an axis per minute.
An Example
Going back to our home centrifuge found in a household washing machine – this centrifuge works when we put wet clothes in an inner tube with perforated holes that spins around a center axis. Besides an inner tube, there is also an outer tube located inside our washing machine. When wet clothes spin, the centrifugal force (force created by the centrifuge revolving around an axis very quickly) pushes the clothes against the inner tub with the holes, and the water carrying dirt flows through these holes to the outer tub which leads the water to the drain. You have probably noticed your washing machines has a spin cycle, this is the cycle in which centrifuge not only removes dirty water form your clothes, but helps removes moisture as well. Most washing machines have a motor along with a belt to turn the inner tub extremely fast. While not as fast as most lab centrifuges, your washing machine includes a centrifuge nonetheless.
Use of Centrifugal Force
Centrifugal force forces a body whether solid, liquid or gas, to be pushed away from the center of rotation. This force is used in many technologies such as blood testing, where separate substances of greater and lesser densities are separated easily to be evaluated. In fact, the first centrifuges were made to separate cream from milk and help make butter.
The Concept
The concept behind how a centrifuge works is pretty simple. A centrifuge includes a compartment which spins around an axis. The compartment is usually driven by a motor and can travel very quickly, revolving hundreds to thousands of times around the axis in a minute. The speed of a centrifuge is measured by RPMs (revolutions per minute). While small centrifuges have extremely high RPMs, larger centrifuges like those used by astronauts to test g-forces have much slower RPMs due to the distance they must travel around an axis per minute.
An Example
Going back to our home centrifuge found in a household washing machine – this centrifuge works when we put wet clothes in an inner tube with perforated holes that spins around a center axis. Besides an inner tube, there is also an outer tube located inside our washing machine. When wet clothes spin, the centrifugal force (force created by the centrifuge revolving around an axis very quickly) pushes the clothes against the inner tub with the holes, and the water carrying dirt flows through these holes to the outer tub which leads the water to the drain. You have probably noticed your washing machines has a spin cycle, this is the cycle in which centrifuge not only removes dirty water form your clothes, but helps removes moisture as well. Most washing machines have a motor along with a belt to turn the inner tub extremely fast. While not as fast as most lab centrifuges, your washing machine includes a centrifuge nonetheless.
Use of Centrifugal Force
Centrifugal force forces a body whether solid, liquid or gas, to be pushed away from the center of rotation. This force is used in many technologies such as blood testing, where separate substances of greater and lesser densities are separated easily to be evaluated. In fact, the first centrifuges were made to separate cream from milk and help make butter.
refrences :
Wikipedia
sciencehowstuffwork
monsterguide.net
Wikipedia
sciencehowstuffwork
monsterguide.net
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-
AliHagigat
عضویت : شنبه ۱۳۸۷/۹/۹ - ۱۰:۵۹
پست: 505-
سپاس: 6
Re: نحوه کارکرد دستگاه سانتریفیوژ
داخل دستگاه سانتریفیوژ مواد سنگین تر به جداره می چسبند یا به ته ظرف میروند؟ اگر جاذبهٔ زمین نباشد باز هم مواد جدا می شوند؟ چه نیروهائی به مواد داخل دستگاه اثر میکند؟
اگر ظرف دستگاه می چرخد آیا مواد داخلش هم الزاماً می چرخند و چرا؟
اگر ظرف دستگاه می چرخد آیا مواد داخلش هم الزاماً می چرخند و چرا؟