condensation

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A phase-change process in which vapor converts into liquid when the temperature of the vapor is reduced below the saturation temperature corresponding to the pressure in the vapor. For a pure vapor this pressure is the total pressure, whereas in a mixture of a vapor and a noncondensable gas it is the partial pressure of the vapor. Sustaining the process of condensation on a cold surface in a steady state requires cooling of the surface by external means. Condensation is an efficient heat transfer process and is utilized in various industrial applications. Condensation of vapor on a cold surface can be classified as filmwise or dropwise. Direct-contact condensation refers to condensation of vapor (bubbles or a vapor stream) in a liquid or condensation on liquid droplets entrained in the vapor. If vapor temperature falls below its saturation temperature, condensation can occur in the bulk vapor. This phenomenon is called homogeneous condensation (formation of fog) and is facilitated by foreign particles such as dust. See also Gas; Heat transfer.

In film condensation, a thin film of liquid forms upon condensation of vapor on a cold surface that is well wetted by the condensate. The liquid film flows downward as a result of gravity.

In dropwise condensation, on surfaces that are not well wetted, vapor may condense in the form of droplets (see illustration). The droplets form on imperfections such as cavities, dents, and cracks on the surface. The droplets of 10–100 μm diameter contribute most to the heat transfer rate. As a droplet grows to a size that can roll down the surface because of gravity, it wipes the surface of the droplets in its path. In the wake behind the large droplet, numerous smaller droplets form and the process repeats. The heat transfer coefficients with dropwise condensation can be one to two orders of magnitude greater then that for film condensation.

Steam at atmospheric pressure condensing on a vertical copper surface. Film condensation is visible on the right side, and dropwise condensation in the presence of a promoter is visible on the left side. The horizontal tube is a thermocouple. (J. F. Welch and J. W. Westwater, Department of Chemical Engineering, University of Illinois, Urbana)

Direct-condensation involves condensation of vapor bubbles in a host liquid and condensation on droplets entrained in vapor. Both are also very efficient heat transfer processes, especially when the vapor-liquid interface oscillates.

noun

A short summary or version prepared by cutting down a larger work: abridgment, abstract, brief, epitome, synopsis. See words.

Definition: abridgment
Antonyms: unabridgment

n

Definition: water buildup
Antonyms: dryness

The change of a vapour or gas into liquid form. This change of state is accompanied by the release of latent heat, which alters the adiabatic temperature change in rising air. Condensation in meteorology can be caused by: the cooling of a constant volume of air to dew point, the expansion of a parcel of air without heat input, the evaporation of extra moisture into the air, the fall in the moisture-holding capacity of the air due to changes in both volume and temperature, and contact with a colder material or air mass.

The likelihood of water vapour condensing will depend on the saturation vapour pressures of water and ice at any given temperature, and/or the presence of condensation nuclei, since water vapour can be cooled to well below 0 °C before condensation occurs. see condensation nuclei, Bergeron-Findeisen theory.

1. In a refrigeration system, the process of changing the refrigerant into liquid by the extraction of heat.
2. See surface condensation.

Condensation, along with displacement, is an essential process in dream work and more generally in primary-process thinking. We tend to view it as a way of attributing, to a person or representative object, characteristics and properties that, from the point of view of latent thoughts, belong to other persons or objects. In reality, if we go by Freud's text in The Interpretation of Dreams (1900a), condensation, like displacement, does not proceed directly by modifying the content of a representation. All dreams are made up of latent dream thoughts, each of which corresponds to one or several chains of associations, with each link being initially charged with a psychic intensity. Dream work consists in changing the location of these fragmentary intensities without either increasing or reducing their global value.

In displacement, one assigns to link A in a chain of associations the intensity initially associated with link B. Condensation, in contrast, operates by bringing intensities together. When two chains of association intersect, it assigns to the common link the sum of the intensities of the two intersecting chains. This nevertheless indirectly alters the representation because, in the manifest content of the dream, a link will not figure if it does not retain an intensity. By displacing the intensities of several chains to their common link, condensation makes it possible to represent all of the chains by a single link. Hence, there is an economy of means that contributes to censorship. As a result, when one link takes the place of several chains, this makes it more difficult to read through to the wish corresponding to those chains.

Condensation thus has an indirect effect on the figural content of representations. It does not create chimeras that bring together in one element the attributes of others. Nor does it engage in metonymy, in which one of the links represents one or several chains of association. It is a process that operates by displacing intensity, but when the intensity of several chains is brought to bear on their common link, condensation seeks to represent them all.

When explaining the effect of condensation, Freud used the metaphor of italics. A representative link whose intensity has been reinforced by condensation has a status comparable to that of a word in italics in a text. This metaphor calls for two remarks. First, the intensity added to a fragment of a representation through condensation makes it possible, like italics, to stress the importance of the representation. This added intensity indicates at the manifest level that the representation stands for the different latent chains intersecting at the link. Second, typographical emphasis warps the texture of a text and invites us to look for links other than those offered by successive statements. Typographical emphasis is an invitation to abandon linearity and search for the dreamer's associations.

The notion of intensity is complex. The term indicates the psychic interest of a particular idea. But we may well ask whether this interest should not be extended to the affect associated with each chain of associations or the instinct that determines each association.

Although Freud studied condensation particularly in relation to dreams, especially in The Interpretation of Dreams, he also describes the effect of this process in other manifestations of primary-process thinking, such as jokes, forgetting names, slips of the tongue, and symptoms. In these latter domains, however, it is sometimes quite difficult to distinguish between condensation and overdetermination. In both cases, as the result of a transformation, a representation substitutes for more elaborate thought content. Both processes seem to proceed by increasing intensity, that is, by economic modification, and this results in the reorganization of the thought content. But whereas condensation can be viewed as a sum of intensities relative to forces acting in the same direction, overdetermination appears more as an appropriation of content by heterogeneous if not antagonistic forces. In fact, the content of an overdetermined representation acts as a fulcrum for opposing logics and conflicting systems (such as the preconscious and the unconscious). A thought content (or representation) resulting from the interaction of forces pushing for the fulfillment of an unconscious wish and forces opposing it (the censor) is a good example of overdetermination but not of condensation, since the censor is not part of the latent dream thoughts. However, as soon as the signifying element begins to represent conflict (as in the case of a symptom), the difference between condensation and overdetermination is more difficult to establish.

Bibliography

Freud, Sigmund. (1900a). The interpretation of dreams. SE, 4: 1-338; 5: 339-625.

——. (1905c). Jokes and their relation to the unconscious. SE, 8: 1-236.

——. (1916-1917a [1915-17]). Introductory lectures on psycho-analysis. SE, 15: 9-239; 16: 243-463.

—LAURENT DANON-BOILEAU

The notion that dreams provide an avenue for the expression of normally repressed desires while simultaneously disguising and censoring our real urges was systematically formulated by Sigmund Freud, the father of psychoanalysis. In Freud's view, the purpose of dreams is to allow us to satisfy in fantasies the instinctual urges that society judges to be unacceptable in some way, such as the urge to seduce or to kill. If, however, we were to dream about an actual seduction or an actual assault, the emotions evoked by the dream would awaken us. So that our sleep is not continually disturbed by such dreams, the mind modifies and disguises their content so that strong emotions are not evoked. Freud referred to the process of censoring and transforming dream contents into less disturbing images as the dreamwork, and explicitly identified five processes through which dreams are censored: displacement, condensation, symbolization, projection, and secondary revision.

Condensation, as the word implies, is a process that disguises a particular thought, urge, or emotion by contracting it into a brief dream event or image, the deeper meaning of which is not readily evident. Condensation also refers to the tendency of the dreamwork to bring together two or more different experiences or concerns into a single dream narrative or image. In Freud's words,

From every element in a dream's content associative threads branch out in two or more directions; every situation in a dream seems to be put together out of two or more impressions or experiences.

The overlap of two or more distinct sets of associations in one dream situation effectively disguises the true meaning of the dream.

1. the act or process of condensing; the state of being condensed.
2. the product of condensing; a condensed mass.
3. any (usually stepwise) chemical reaction in which two or more identical or nonidentical molecular entities, or two parts of one entity, combine with the elimination of a molecule of water, ammonia, ethanol, hydrogen sulfide, or other simple substance. The combining entities or parts each (formally) contribute a moiety to the molecule eliminated.

1. the act of rendering, or the process of becoming, more compact.
2. the process of passing from a gaseous to a liquid or solid phase. In animal housing this is a matter of great importance because of the need for a dry environment as a prevention against the spread of infection, especially those spread by inhalation.

A commonly used term for the insertion and compression or compaction of dental materials into a prepared cavity. Compaction is a more accurate term than condensation. See also compaction.

• Heat - condensation: change of state from gas to liquid
• Physical Properties and Changes - condensation: change from vapor phase to liquid phase

For other uses, see Condensation (disambiguation).

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Water vapor condenses into a liquid after making contact with the surface of a cold bottle.

Condensation forming over the wing of an aircraft in a low pressure zone

Condensation is the change of the physical state of matter from gaseous phase into liquid phase, and is the reverse of vaporization.^[1] When the transition happens from the gaseous phase into the solid phase directly, the change is called deposition.

Condensation is initiated by the formation of atomic/molecular clusters of that species within its gaseous volume—like rain drop or snow-flake formation within clouds—or at the contact between such gaseous phase and a (solvent) liquid or solid surface.

A few distinct reversibility scenarios emerge here with respect to the nature of the surface.

• absorption into the surface of a liquid (either of the same species or one of its solvents)—is reversible as evaporation.^[1]
• adsorption (as dew droplets) onto solid surface at pressures and temperatures higher than the specie's triple point—also reversible as evaporation.
• adsorption onto solid surface (as supplemental layers of solid) at pressures and temperatures lower than the specie's triple point—is reversible as sublimation.

Condensation commonly occurs when a vapor is cooled and/or compressed to its saturation limit when the molecular density in the gas phase reaches its maximal threshold. Vapor cooling and compressing equipment that collects condensed liquids is called "condenser".

Psychrometry measures the rates of condensation from and evaporation into the air moisture at various atmospheric pressures and temperatures. Water is the product of its vapor condensation—condensation is the process of such phase conversion.

Contents 1 Applications of condensation 2 Biological adaptation 3 Condensation in building construction 4 See also 5 Notes 6 References

Applications of condensation

Condensation is a crucial component of distillation, an important laboratory and industrial chemistry application.

Because condensation is a naturally occurring phenomenon, it can often be used to generate water in large quantities for human use. Many structures are made solely for the purpose of collecting water from condensation, such as air wells and fog fences. Such systems can often be used to retain soil moisture in areas where active desertification is occurring—so much so that some organizations educate people living in affected areas about water condensers to help them deal effectively with the situation.^[2]

It is also a crucial process in forming particle tracks in a Cloud Chamber. In this case, ions produced by an incident particle act as nucleation centres for the vapour to condense on.

Biological adaptation

Numerous living organisms use water made accessible by condensation. A few examples are the Australian Thorny Devil, Darkling beetles on the Namibian coast and Coast Redwoods on the west coast of the United States.

Condensation in building construction

Condensation on a window during a rain shower.

Condensation in building construction is an unwanted phenomenon as it may cause dampness, mold health issues, wood rot, corrosion and energy loss due to increased heat transfer.

Interstructure condensation may be caused by thermal bridges, insufficient or lacking damp proofing or insulated glazing.^[3]

See also

• Air well (condenser)
• Bose–Einstein condensate
• Condenser (heat transfer)
• DNA condensation
• Kelvin equation
• Phase diagram
• Phase transition
• Retrograde condensation
• Surface condenser

Notes

1. ^ ^{a b} Nic, M.; Jirat, J.; Kosata, B., eds. (2006–). "condensation in atmospheric chemistry". IUPAC Compendium of Chemical Terminology (Online ed.). doi:10.1351/goldbook.C01235. ISBN 0-9678550-9-8. http://goldbook.iupac.org/C01235.html. 
2. ^ FogQuest - Fog Collection / Water Harvesting Projects - Welcome
3. ^ diydata.com

References

• "Condensation principles (Picture)". http://www.ces.purdue.edu/pork/images/jones/condense.jpg. 

v t e States of matter Solid Liquid Gas / Vapor Plasma Low energy Bose–Einstein condensate · Fermionic condensate · Quantum Hall · Rydberg matter · Strange matter · Superfluid · Supersolid High energy Degenerate matter · QCD matter · Quark–gluon plasma  · Supercritical fluid Other states Colloid · Glass · Liquid crystal · Magnetically ordered (Antiferromagnet, Ferrimagnet, Ferromagnet) · String-net liquid · Superglass Transitions Boiling · Boiling point · Condensation · Critical line · Critical point · Crystallization · Deionization · Deposition · Evaporation · Flash evaporation · Freezing · Ionization · Lambda point · Melting · Melting point · Regelation · Saturated fluid · Sublimation · Supercooling · Triple point · Vaporization Quantities Enthalpy of fusion · Enthalpy of sublimation · Enthalpy of vaporization · Latent heat · Latent internal energy · Trouton's ratio · Volatility Concepts Binodal · Compressed fluid · Cooling curve · Equation of state · Leidenfrost effect · Mpemba effect · Order and disorder (physics) · Spinodal · Superconductivity · Superheated vapor · Superheating · Thermo-dielectric effect

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Dansk (Danish)
n. - fortætning, nedslag, forkortelse, sammentrængning

Nederlands (Dutch)
condensatie, verkorte versie

Français (French)
n. - condensation, buée, (Chim) condensation, version condensée

Deutsch (German)
n. - Kondensation, Verflüssigung, Kurzfassung

Ελληνική (Greek)
n. - συμπύκνωση, υγροποίηση, εξίδρωση

Italiano (Italian)
condensazione

Português (Portuguese)
n. - condensação (f)

Русский (Russian)
конденсация

Español (Spanish)
n. - condensación

Svenska (Swedish)
n. - kondensering, förtätning, imma, hopgyttring, sammanträngning, nedskärning

中文（简体）(Chinese (Simplified))
压缩, 液化, 凝缩

中文（繁體）(Chinese (Traditional))
n. - 壓縮, 液化, 凝縮

한국어 (Korean)
n. - 응축, 액화, 요약

日本語 (Japanese)
n. - 凝縮, 凝結, 濃縮, 凝縮されたもの, 水滴, 簡約, 要約

العربيه (Arabic)
‏(الاسم) تكثف, رطوبه, تلخيص‏

עברית (Hebrew)
n. - ‮עיבוי, טיפות, ריכוז, קיצור, אדים‬

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