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Siemens Cycle
The Siemens cycle is a technique used to cool or liquefy gases. A gas is compressed, leading to an increase in its temperature due to the directly proportional relationship between temperature and pressure (as stated by Gay-Lussac's law). The compressed gas is then cooled by a heat exchanger and decompressed, resulting in a (possibly condensed) gas that is colder than the original at the same pressure. Carl Wilhelm Siemens patented the Siemens cycle in 1857. In the Siemens cycle the gas is: :1. Heated – by compressing the gas – adding external energy into the gas, to give it what is needed for running through the cycle :2. Cooled – by immersing the gas in a cooler environment, losing some of its heat (and energy) :3. Cooled through heat exchanger with returning gas from next (and last stage) :4. Cooled further by expanding the gas and doing work, removing heat (and energy) The gas which is now at its coolest in the current cycle, is recycled and sent back to be – :5. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Liquefaction Of Gases
Liquefaction of gases is physical conversion of a gas into a liquid state (condensation). The liquefaction of gases is a complicated process that uses various compressions and expansions to achieve high pressures and very low temperatures, using, for example, turboexpanders. Uses Liquefaction processes are used for scientific, industrial and commercial purposes. Many gases can be put into a liquid state at normal atmospheric pressure by simple cooling; a few, such as carbon dioxide, require pressurization as well. Liquefaction is used for analyzing the fundamental properties of gas molecules (intermolecular forces), or for the storage of gases, for example: LPG, and in refrigeration and air conditioning. There the gas is liquefied in the '' condenser'', where the heat of vaporization is released, and evaporated in the '' evaporator,'' where the heat of vaporization is absorbed. Ammonia was the first such refrigerant, and is still in widespread use in industrial refrigeration ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Temperature
Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measurement, measured with a thermometer. Thermometers are calibrated in various Conversion of units of temperature, temperature scales that historically have relied on various reference points and thermometric substances for definition. The most common scales are the Celsius scale with the unit symbol °C (formerly called ''centigrade''), the Fahrenheit scale (°F), and the Kelvin scale (K), the latter being used predominantly for scientific purposes. The kelvin is one of the seven base units in the International System of Units (SI). Absolute zero, i.e., zero kelvin or −273.15 °C, is the lowest point in the thermodynamic temperature scale. Experimentally, it can be approached very closely but not actually reached, as recognized in the third law of thermodynamics. It would be impossible to extract energy as heat from a body at that temperature. Tem ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gay-Lussac's Law
Gay-Lussac's law usually refers to Joseph-Louis Gay-Lussac's law of combining volumes of gases, discovered in 1808 and published in 1809. It sometimes refers to the proportionality of the volume of a gas to its absolute temperature at constant pressure. This law was published by Gay-Lussac in 1802, and in the article in which he described his work he cited earlier unpublished work from the 1780s by Jacques Charles. Consequently, the volume-temperature proportionality is usually known as Charles's Law. Law of combining volumes The law of combining volumes states that, when gases react together they do so in volume which bears simple whole number ratio provided that the temperature and pressure of the reacting gases and their products remain constant The ratio between the volumes of the reactant gases and the gaseous products can be expressed in simple whole numbers. For example, Gay-Lussac found that two volumes of hydrogen and one volume of oxygen would react to form two vo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heat Exchanger
A heat exchanger is a system used to transfer heat between a source and a working fluid. Heat exchangers are used in both cooling and heating processes. The fluids may be separated by a solid wall to prevent mixing or they may be in direct contact. They are widely used in space heating, refrigeration, air conditioning, power stations, chemical plants, petrochemical plants, petroleum refineries, natural-gas processing, and sewage treatment. The classic example of a heat exchanger is found in an internal combustion engine in which a circulating fluid known as engine coolant flows through radiator coils and air flows past the coils, which cools the coolant and heats the incoming air. Another example is the heat sink, which is a passive heat exchanger that transfers the heat generated by an electronic or a mechanical device to a fluid medium, often air or a liquid coolant. Flow arrangement Image:Heat_exc_1-1.svg, Fig. 1: Shell and tube heat exchanger, single pass (1 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carl Wilhelm Siemens
Sir Carl Wilhelm Siemens (4 April 1823 – 19 November 1883), anglicised to Charles William Siemens, was a German-British electrical engineer and businessman. Biography Siemens was born in the village of Lenthe, today part of Gehrden, near Hanover where his father, Christian Ferdinand Siemens (31 July 1787 – 16 January 1840), a tenant farmer, farmed an estate belonging to the Crown. The Siemens family is an old family of Goslar which has been documented since 1384. His mother was Eleonore Deichmann (1792–8 July 1839), and William, or Carl Wilhelm, was the fourth son of a family of fourteen children. Of his siblings, Ernst Werner Siemens, the fourth child, became a famous electrician and was associated with William in many of his inventions. He was also the brother of Carl Heinrich von Siemens and a cousin of Alexander Siemens. On 23 July 1859, Siemens was married at St James's, Paddington, to Anne Gordon—the youngest daughter of Mr Joseph Gordon, Writer to the Signe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Adiabatic Process
In thermodynamics, an adiabatic process (Greek: ''adiábatos'', "impassable") is a type of thermodynamic process that occurs without transferring heat or mass between the thermodynamic system and its environment. Unlike an isothermal process, an adiabatic process transfers energy to the surroundings only as work.. A translation may be founhere. Also a mostly reliabltranslation is to be foundin As a key concept in thermodynamics, the adiabatic process supports the theory that explains the first law of thermodynamics. Some chemical and physical processes occur too rapidly for energy to enter or leave the system as heat, allowing a convenient "adiabatic approximation".Bailyn, M. (1994), pp. 52–53. For example, the adiabatic flame temperature uses this approximation to calculate the upper limit of flame temperature by assuming combustion loses no heat to its surroundings. In meteorology and oceanography, adiabatic cooling produces condensation of moisture or salinity, o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gas Compressor
A compressor is a mechanical device that increases the pressure of a gas by reducing its volume. An air compressor is a specific type of gas compressor. Compressors are similar to pumps: both increase the pressure on a fluid and both can transport the fluid through a pipe. The main distinction is that the focus of a compressor is to change the density or volume of the fluid, which is mostly only achievable on gases. Gases are compressible, while liquids are relatively incompressible, so compressors are rarely used for liquids. The main action of a pump is to pressurize and transport liquids. Many compressors can be staged, that is, the fluid is compressed several times in steps or stages, to increase discharge pressure. Often, the second stage is physically smaller than the primary stage, to accommodate the already compressed gas without reducing its pressure. Each stage further compresses the gas and increases its pressure and also temperature (if inter cooling between stages ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hampson–Linde Cycle
The Hampson–Linde cycle is a process for the liquefaction of gases, especially for air separation. William Hampson and Carl von Linde independently filed for patents of the cycle in 1895: Hampson on 23 May 1895 and Linde on 5 June 1895. The Hampson–Linde cycle introduced regenerative cooling, a positive-feedback cooling system. The heat exchanger arrangement permits an absolute temperature difference (e.g. J–T cooling for air) to go beyond a single stage of cooling and can reach the low temperatures required to liquefy "fixed" gases. The Hampson–Linde cycle differs from the Siemens cycle only in the expansion step. Whereas the Siemens cycle has the gas do external work to reduce its temperature, the Hampson–Linde cycle relies solely on the Joule–Thomson effect In thermodynamics, the Joule–Thomson effect (also known as the Joule–Kelvin effect or Kelvin–Joule effect) describes the temperature change of a ''real'' gas or liquid (as differentiated from an ide ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Regenerative Cooling
Regenerative cooling is a method of cooling gases in which compressed gas is cooled by allowing it to expand and thereby take heat from the surroundings. The cooled expanded gas then passes through a heat exchanger where it cools the incoming compressed gas. Regenerative cycles *Stirling cycle * Gifford–McMahon cycle * Vuilleumier cycle *Pulse tube refrigerator History In 1857, Siemens introduced the regenerative cooling concept with the Siemens cycle. In 1895, William Hampson in England and Carl von Linde in Germany independently developed and patented the Hampson–Linde cycle to liquefy air using the Joule–Thomson expansion process and regenerative cooling. On 10 May 1898, James Dewar used regenerative cooling to become the first to statically liquefy hydrogen. See also *Cryocooler *Displacer *Fluid mechanics *Regenerative cooling (rocket) *Regenerative heat exchanger *Thermodynamic cycle A thermodynamic cycle consists of a linked sequence of thermodynamic processes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Timeline Of Low-temperature Technology
The following is a timeline of low-temperature technology and cryogenic technology (refrigeration down to –273.15 °C, –459.67 °F or 0 K). It also lists important milestones in thermometry, thermodynamics, statistical physics and calorimetry, that were crucial in development of low temperature systems. Prior to the 19th century * – Zimri-Lim, ruler of Mari in Syria commanded the construction of one of the first ice houses near the Euphrates. * – The yakhchal (meaning "ice pit" in Persian) is an ancient Persian type of refrigerator. The structure was formed from a mortar resistant to heat transmission, in the shape of a dome. Snow and ice was stored beneath the ground, effectively allowing access to ice even in hot months and allowing for prolonged food preservation. Often a badgir was coupled with the yakhchal in order to slow the heat loss. Modern refrigerators are still called yakhchal in Persian. * - Hero of Alexandria knew of the principle that cer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermodynamic Cycles
A thermodynamic cycle consists of a linked sequence of thermodynamic processes that involve transfer of heat and work into and out of the system, while varying pressure, temperature, and other state variables within the system, and that eventually returns the system to its initial state. In the process of passing through a cycle, the working fluid (system) may convert heat from a warm source into useful work, and dispose of the remaining heat to a cold sink, thereby acting as a heat engine. Conversely, the cycle may be reversed and use work to move heat from a cold source and transfer it to a warm sink thereby acting as a heat pump. If at every point in the cycle the system is in thermodynamic equilibrium, the cycle is reversible. Whether carried out reversible or irreversibly, the net entropy change of the system is zero, as entropy is a state function. During a closed cycle, the system returns to its original thermodynamic state of temperature and pressure. Process quantiti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1857 In Science
The year 1857 in science and technology involved some significant events, listed below. Astronomy * Peter Andreas Hansen's ''Tables of the Moon'' are published in London. Biology * Rev. M. J. Berkeley publishes ''Introduction to Cryptogamic Botany''. Chemistry * Robert Bunsen invents apparatus for measuring effusion. * August Kekulé proposes that carbon is tetravalent, or forms exactly four chemical bonds. * Carl Wilhelm Siemens patents the Siemens cycle. Earth sciences * January 9 – The 7.9 Fort Tejon earthquake shakes Central and Southern California with a maximum Mercalli intensity of IX (''Violent''). The event, which involves slip on the southern segment of the San Andreas Fault, leaves two people dead. * Friedrich Albert Fallou publishes ''Anfangsgründe der Bodenkunde'' irst Principles of Soil Science laying the foundations for the modern study of soil science. Exploration * May 16 – The British North American Exploring Expedition, led by Irish geographer Ca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
