Explanatory dictionary of the Russian language. D.N. Ushakov

condensation

condensation, w. (specialist.). Action on verb. condense and condense. electricity condensation. Condensation of vapor (turning it into a liquid).

Explanatory dictionary of the Russian language. S.I. Ozhegov, N.Yu. Shvedova.

condensation

[de], -i, f. (specialist.).

The transfer of matter from gaseous state to liquid or crystalline. K. couple.

Figure 12: There are two types of clouds in this image. The delicate, clear "hair" in the upper right corner is a cirrus cloud, a pattern dictated by the wind. Irregular "buds" in parallel stripes form in the atmosphere below the clouds of cobblestones. When a strong wind blows over the relief of a variety of sculptures, obstacles on the surface of the Earth cause air to flow - not only horizontally, but also in an up-down mode. Places where the air moves upwards contribute to the formation of cloud clouds, the downward movement of space - on the contrary.

The resulting crests of circus clouds form perpendicular to the direction of the wind. Picture: Ngayor Small. Figure 13: This picture shows a cloud called its shape associated with the spine or rather the fish with dorsal dorsal spine. Its appearance in the sky signals the presence of a jet, which is a band of extremely strong winds high in the atmosphere. The wind blows along the "spine" of the clouds, and scattered parallel cloud bands are associated with vertical air movements.

Accumulation in some quantity. K. energy.

adj. condensation, -th, -th.

New explanatory and derivational dictionary of the Russian language, T. F. Efremova.

condensation

Accumulation of something in some quantity.

The transition of a substance from a gaseous state to a liquid or solid state due to cooling or compression.

High clouds are composed entirely of ice crystals, often with regular shapes. Figure 14: Clouds are another cloud of convection and wind. Unlike the grove, the streets lay along the direction of the wind. Their system implements a system of so-called conventional rolls - elongated vortices with horizontal axes. As usual, the cloud is created where the air rises. The photograph by Mik Petrov depicts exceptionally picturesque Australian clouds. Streets may not always have such a regular shape, they may be made up of smaller "cauliflowers".

Encyclopedic Dictionary, 1998

condensation

CONDENSATION (from late Latin condensatio - compaction, thickening) the transition of a substance from a gaseous state to a liquid or solid. Condensation is possible only at temperatures below the critical temperature.

Condensation

(Late Latin condensatio ≈ condensation, from the Latin condenso I condense, condense), the transition of a substance from a gaseous state to a liquid or solid due to its cooling or compression. K. steam is possible only at temperatures below the critical one for a given substance (see. Critical situation). K., like the reverse process ≈ evaporation, is an example phase transformations substances (phase transitions of the 1st kind). K. releases the same amount of heat that was expended on the evaporation of the condensed substance. Rain, snow, dew, frost - all these natural phenomena are the result of the condensation of water vapor in the atmosphere. C. is widely used in engineering: in the power industry (for example, in condensers of steam turbines), in chemical technology (for example, in the separation of substances by the method of fractionated condensation), in refrigeration and cryogenic technology, in desalination plants, etc. The liquid formed during K., is called condensate. In technology, k. is usually carried out on cooled surfaces. There are two known regimes of surface K.: film and drip. The first is observed during condensation on a wetted surface; it is characterized by the formation of a continuous film of condensate. On non-wetted surfaces, condensate forms as separate droplets. With drip condensate, the intensity of heat transfer is much higher than with film condensate, since a continuous film of condensate hinders heat transfer (see Boiling).

The higher the surface temperature, the lower the surface temperature compared to the saturation temperature of the vapor at a given pressure. The presence of another gas reduces the speed of surface cooling, since the gas makes it difficult for steam to reach the cooling surface. In the presence of non-condensable gases, cooling begins when the vapor at the cooling surface reaches the partial pressure and temperature corresponding to the state of saturation (dew point).

K. can also occur inside the volume of steam (vapor-gas mixture). To begin with, volumetric K. vapor must be noticeably supersaturated. The measure of supersaturation is the ratio of the vapor pressure p to the pressure saturated steam ps, which is in equilibrium with a liquid or solid phase having a flat surface. Steam is supersaturated if p/ps > 1, if p/ps = 1 the steam is saturated. The degree of supersaturation p/ps needed to start. K., depends on the content in the pair of the smallest dust particles (aerosols), which are ready-made centers, or nuclei, K. The purer the steam, the higher the initial degree of supersaturation should be. The centers of K. can also serve as electrically charged particles, in particular ionized atoms. Based on this, for example, the operation of a number of devices nuclear physics(see Wilson chamber).

Lit .: Kikoin I. K. and Kikoin A. K., Molecular physics, M., 1963; Isachenko V. P., Osipova V. A., Sukomel A. S., Heat transfer, 2nd ed., M., 1969; Kutateladze S. S., Heat transfer during condensation and boiling, 2nd ed., M.≈L., 1952.

D. A. Labuntsov.

Wikipedia

Condensation (disambiguation)

• Condensation.
• Condensation.
• Condensation.
• Condensation reaction
• Claisen condensation
• Knoevenagel condensation
• Bose-Einstein condensation
• Dodgson condensation

Condensation

thumb|Dew on a web thumb|Condensation on a bottle of cold water thumb|Condensation of water vapor in the air over a cup hot water Condensation vapor - the transition of a substance into a liquid or solid state from a gaseous state (the reverse of the latter process is called sublimation). The maximum temperature below which condensation occurs is called the critical temperature. The steam from which condensation can occur is either saturated or unsaturated.

Condensation (chemistry)

Condensation reaction- the reaction of the formation of large molecules from molecules with a lower molecular weight, proceeding with the elimination of atoms or atomic groups; for example, phenol-formaldehyde resins are the product of the condensation of phenol with formaldehyde.

Examples of the use of the word condensation in the literature.

Carl was leaning over the table, he was putting the record into the condenser oven for up to condensation, he was going to click the shutter and move away, after that Erwin had to focus the beam generator into the crucible of the furnace and turn on condensation.

The Englishman Wilson used a condensation chamber in such a way that in it the paths of the nuclei of atoms and other charged particles became visible to the human eye in the form of traces condensation.

Many times I drew for myself synthetic meat mushrooms, and pies stuffed with artificial cheeses, and fried fish fillets from our underground chemical plants, and fatty meat sausages, a product of multi-stage wood processing, and the freshest pink ham with tender fat, obtained as a result of condensation combustible gases, and juicy creamy cakes supplied by oil refineries, and even that unfortunate poor natural lamb skewers that Romero tried to treat us to.

When all these points were explained to the patient, he was strongly advised to use all three mechanisms: change in body sensations, body disorientation, dissociation, anesthesia, amnesia, and subjective condensation time.

As soon as its temperature reaches the point where steam turns into fog, this will be the level condensation, the lower edge of the cloud.

In dreams, Lacan, following Freud, distinguishes two fundamental processes within processes: condensation and substitution.

I heated metallic sodium in an iron spoon under a piece of white plaster, expecting that condensation vapor on a cold surface will give the required drop in density with distance.

Around 1900, Uncle Carl experimented with X-rays and radioactivity in condensation in a bubble chamber, a wooden cylinder filled with mist.

(from late Latin condensatio - seal,), the transition in the islands from a gaseous state to a liquid or solid at subcritical. parameters; phase transition of the first order. K. - exothermic. process in which heat is released phase transition- heat K. Condenser. phase can be formed in the volume of steam or on the surface solid body and liquids with more low temperature than the saturation temperature of steam at a given pressure (see). To. occurs at isothermal. compression, adiabatic expansion and cooling of steam or at the same time. lowering its pressure and t-ry, which leads to the fact that condensers. the phase becomes thermodynamically more stable than the gaseous phase. If at the same time the pressure and t-ra are higher than in triple point for a given v-va, a liquid (liquefaction) is formed, if lower - v-v goes into solid state, bypassing the liquid (desublimation). To. is widely applied in chemical. technologies for separating mixtures through fractional condensation, drying and cleaning in-in etc., in the energy sector, for example. in condensers of steam turbines, in refrigeration equipment for K. working fluid, in desalination. installations, etc. When K. vapors in the narrow pores of adsorbents, the latter can absorb significantly. quantity in-va from the gas phase (see). Consequence K. water vapor in the atmosphere - rain, snow, dew, hoarfrost. liquid condensation. In the case of K. in the volume of steam or gas-vapor mixture (homogeneous K.) condenser. the phase is formed in the form of small drops of liquid (fog) or small crystals. This requires the presence of K. centers, which can serve as very small droplets of liquid (germs) formed as a result of fluctuations in the density of the gas phase, dust particles and particles that carry an electric charge. charge (ions). In the absence of K. centers, steam can last for a long time. time to be in the so-called. metastable (supersaturated) state. Stable homog. K. begins with the so-called. critical supersaturation P kp \u003d p k / p n where p k is the equilibrium pressure corresponding to the critical. the diameter of the embryos, p n - saturation pressure. steam over a flat surface of a liquid (for example, for water vapor in air purified from solid particles or ions, P cr \u003d 5-8). Fog formation is observed both in nature and in technology. devices, for example. during cooling of the gas-vapor mixture due to radiation, mixing of wet gases. Condensation on the surface of a solid saturated or superheated steam occurs at a surface temperature that is less than the vapor saturation temperature at its equilibrium pressure above it. It is observed in many industries. devices, to-rye serve for K. target products, heating decomp. environments, separation of steam and vapor-gas mixtures, cooling of moist gases, etc. When liquefying steam on the surface of a solid body, which is well wetted by condensate, a continuous film of liquid (film K.) is formed; on a surface that is not wetted by condensate or partially wetted - separate drops (drip K.); on surfaces with heterogeneous properties (for example, on polished metal with oxidized contaminated areas) - zones covered with a film of condensate and drops (mixed K.). With film K. of pure vapors of non-metals, the coefficient. heat transfer is determined in the main. thermal the resistance of the condensate film, which depends on the mode of its flow. The latter in the case of a practically immobile vapor is determined by the Reynolds number of the film: Re pl \u003d wd / v k, where w, d - resp. cross-sectional speed and thickness of the condensate film, v k - kinematic. viscosity of the condensate. For K. on a vertical plate or pipe with Re pl less than 5-8, the film flow is purely laminar, if these values ​​are exceeded, Re pl is laminar-wave, and with Re pl>> 350-400 - turbulent. On vertical surfaces it means. heights, areas with dec. condensate film flow regimes. In laminar flow, an increase in Re pl with increasing film thickness leads to a decrease in the coefficient. heat transfer, with turbulent flow - to its increase. If the steam is overheated, K. is accompanied by convective heat transfer from steam to condensate, the surface temperature of which is practically equal to the saturation temperature at steam pressure. For in-in with a large heat of K. (for example, water, alcohols), the heat of overheating is usually insignificant in comparison with the heat of K., and it can be neglected. In the case of film condensate of a moving vapor, the shear stress on the phase interface, due to interfacial friction and momentum transfer by particles of condensed vapor, which are attached to the condensate film, causes an increase in speed and a decrease in film thickness with a downward steam flow, as a result of which the coefficient . heat transfer increases. At higher steam flow rates, its impact on the condensate film can lead not only to a change in its velocity and thickness, but also to flow disturbance (wave formation, turbulence), which intensifies heat transfer in the film. If the steam flow is directed upwards, the movement of the laminar condensate film is retarded, its thickness increases and the coefficient. heat transfer decreases as the steam velocity increases until the action of interfacial friction causes the so-called. reversed (upward) flow of the condensate film. When K. moving steam inside the pipe (channel) flow regimes and the nature of the interaction. vapor and liquid phases can vary significantly as a result of changes in the process of formation of condensate velocity of steam, tangential friction stress on the interfacial surface and Re pl. At high steam velocities (when the effect of gravity on the condensate film is negligible and its flow is determined mainly by friction), local and average coefficients along the length of the pipe. heat transfers do not depend on spaces. pipe orientation. If the forces of gravity and friction are commensurate, the conditions for friction are determined by the angle of inclination of the pipe and the mutual direction of motion of the phases. In the case of K. inside a horizontal pipe and a low steam velocity, an annular film of condensate is formed only on the top, part of the inner surface of the pipe. On the bottom part, a "stream" appears, in the zone of which, as a result of the relatively large thickness of the liquid layer, heat transfer is much less intense than in the rest of the area. In the case of K. on a bundle of horizontal pipes, the flow rate of the flowing condensate increases from top to bottom due to the leakage of condensate from the overlying pipes to the underlying ones, and the flow rate of steam along the path of its movement decreases. In a bundle with a constant or relatively slightly decreasing in height free cross section between the pipes, the rate of the downward steam flow gradually decreases, and the condensate flows from the top to the bottom pipes. Initially, this leads to a decrease in local coefficients. heat transfer (averaged over the perimeter of the pipes) with an increase in the number of the horizontal row of pipes counted from above. However, starting from a certain series, as a result of the leakage of condensate, the flow of the film is perturbed and its thermal. resistance is reduced. Thanks to this, the coefficient heat transfer can stabilize, and with an increasing effect of perturbation of the film flow on the lower. tubes - increase with increasing number of the row. Intensification of heat transfer with film K. can be achieved by profiling its surface (for example, using the so-called finely wavy surface), which helps to reduce the average thickness of the condensate film, creating on the surface of the arts, roughness, leading to tour -bulization of the film, exposure to it with a dielectric. liquid phase (eg, with K. freons) electrostatic. field, suction of condensate through a porous surface, etc. During the condensation of vapors of liquid metals, the thermal conductivity of the liquid phase is very high. Therefore, the share of thermal. resistance of the condensate film in the total resistance to heat transfer is negligible, and interfacial thermal is decisive. resistance due to molecular kinetic. effects at the interface. Sometimes film To. on a pov-sti is followed by homog. K. in the steam layer adjacent to the interface. If the formation of fog is undesirable (for example, in the production of H2SO4 by the nitrous method or when capturing volatile solvents), the process is carried out at max. supersaturation of steam below P cr. With drip K., the primary small drops formed on a dry vertical or inclined surface grow as a result of the continuation of the process, the merging of closely spaced and touching drops and the pulling of a thin film of condensate that arises between the drops and rapidly bursts. The droplets that have reached the "separation" diameter flow down, uniting (coalescing) with the underlying small drops, after which small drops form again on the freed surface, and the cycle repeats. The conditions that determine the spontaneous occurrence of drip To. are rarely observed. Usually, for the implementation of drip K., a thin layer of a lyophobizer is applied to a solid surface - in-va, which has a low surface tension and non-wettable with condensate (for example,). In the case of drip K. coefficient. heat transfer is much higher (5-10 times or more) than with film. However, maintenance under operating conditions prom. devices of steady drip To. it is difficult. Therefore, the condensate chemical devices. prom-sti, as a rule, work in film K. Condensation of vapor on the surface of a liquid of the same in-va occurs in technol. devices on the surface of dispersed steam supplied to the volume (for example, with the help of spray nozzles) jets or thin films of liquid flowing down the nozzle. or the distribution of the liquid on allows a strong development of the surface of the phase contact. In some cases, K. is observed when steam enters the liquid volume in the form of jets or bubbles (bubbling), as well as during the formation of steam bubbles in the liquid volume, for example. during cavitation. K. steam from a mixture of it with non-condensable gases (or vapors that are non-condensable at a given temperature) on the surface of a solid or liquid is less intense compared to K. pure steam. Since at K. from a vapor-gas mixture of t-ra and partial pressure(concentration) of steam in its main. mass is higher than on a solid surface, in the mixture layer adjacent to the last layer (when the mixture moves, in the boundary layer), a joint heat and mass transfer occurs. If the vapor is motionless, it doesn't even matter. the gas content in it leads to a sharp decrease in the intensity K. As the velocity (Reynolds number Re cm) of the gas-vapor mixture increases, the influence of the gas on the intensity of the process gradually weakens. In the case of vapor conversion from multicomponent mixtures (steam or steam-gas) in the gas phase, interconnected heat and mass transfer also occur. At the same time, the effective coefficient thermal conductivity of the mixture and effective coefficient. the diffusion of its individual components is determined by the nature and concentrations of the other components. In the case of homog. mixtures of condensates on the surface of a solid body, only film condensate occurs, in the case of a heterogeneous one, mixed condensate. For example, when K. a binary mixture of water vapor and org. in-va on a solid surface, a liquid film of this in-va is formed, covered with drops of moisture.
desublimation. In this process, the condensed (solid) phase cannot drain from the surface of the solid and the thickness of its layer continuously increases. Therefore, the process is non-stationary and its speed gradually decreases. When conducting K. in a deep vacuum (the mean free path of molecules is commensurate with the characteristic size of the apparatus), for example, when separating steam or purifying vapor-gas mixtures, it is necessary to take into account changes in the mechanism and patterns of heat and mass transfer. This leads to a change in the conditions for K. pure vapors and vapors containing impurities of non-condensable gases. See also , Heat transfer. Lit .: Kutateladze S. S., Heat transfer during condensation and boiling. 2nd ed., M. L., 1952; his own, Fundamentals of the theory of heat transfer, 5th ed., M. 1979; Amelin A. G., Theoretical foundations of fog formation during steam condensation, 3rd ed., M., 1972; Isachenko V.P., Heat transfer during condensation, M., 1977; Berman L. D., "Heat power engineering", 1979, No. 5, p. 16-20; his own, ibid., 1980, no. 4, p. 8 13; his own, ibid., 1981, no. 4, p. 22-29; Gorelik A. G., Amyatin A. V., Desublimation in the chemical industry, M., 1986. L. D. Berman.