Condensation

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Condensation forming in the low pressure zone above the wing of an aircraft due to adiabatic expansion Cloud over A340 wing.JPG
Condensation forming in the low pressure zone above the wing of an aircraft due to adiabatic expansion

Condensation is the change of the physical state of matter from the gas phase into the liquid phase, and is the reverse of vaporisation. The word most often refers to the water cycle. [1] It can also be defined as the change in the state of water vapour to liquid water when in contact with a liquid or solid surface or cloud condensation nuclei within the atmosphere. When the transition happens from the gaseous phase into the solid phase directly, the change is called deposition.

State of matter Distinct forms that different phases of matter take on

In physics, a state of matter is one of the distinct forms in which matter can exist. Four fundamental states of matter are observable in everyday life: solid, liquid, gas, and plasma. Many intermediate states are known to exist, such as glass or liquid crystal, and some states only exist under extreme conditions, such as Bose–Einstein condensates, neutron-degenerate matter, and quark-gluon plasma, which only occur, respectively, in situations of extreme cold, extreme density, and extremely high energy. For a complete list of all exotic states of matter, see the list of states of matter.

Gas One of the four fundamental states of matter

Gas is one of the four fundamental states of matter. A pure gas may be made up of individual atoms, elemental molecules made from one type of atom, or compound molecules made from a variety of atoms. A gas mixture, such as air, contains a variety of pure gases. What distinguishes a gas from liquids and solids is the vast separation of the individual gas particles. This separation usually makes a colorless gas invisible to the human observer. The interaction of gas particles in the presence of electric and gravitational fields are considered negligible, as indicated by the constant velocity vectors in the image.

Liquid liquid object

A liquid is a nearly incompressible fluid that conforms to the shape of its container but retains a (nearly) constant volume independent of pressure. As such, it is one of the four fundamental states of matter, and is the only state with a definite volume but no fixed shape. A liquid is made up of tiny vibrating particles of matter, such as atoms, held together by intermolecular bonds. Like a gas, a liquid is able to flow and take the shape of a container. Most liquids resist compression, although others can be compressed. Unlike a gas, a liquid does not disperse to fill every space of a container, and maintains a fairly constant density. A distinctive property of the liquid state is surface tension, leading to wetting phenomena. Water is, by far, the most common liquid on Earth.

Contents

Initiation

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 liquid or solid surface. In clouds, this can be catalyzed by water-nucleating proteins, produced by atmospheric microbes, which are capable of binding gaseous or liquid water molecules. [2]

Cloud Visible mass of liquid droplets or frozen crystals suspended in the atmosphere

In meteorology, a cloud is an aerosol consisting of a visible mass of minute liquid droplets, frozen crystals, or other particles suspended in the atmosphere of a planetary body or similar space. Water or various other chemicals may compose the droplets and crystals. On Earth, clouds are formed as a result of saturation of the air when it is cooled to its dew point, or when it gains sufficient moisture from an adjacent source to raise the dew point to the ambient temperature. They are seen in the Earth's homosphere. Nephology is the science of clouds, which is undertaken in the cloud physics branch of meteorology.

Bacterial ice-nucleation proteins is a family of proteins that enable Gram-negative bacteria to promote nucleation of ice at relatively high temperatures. These proteins are localised at the outer membrane surface and can cause frost damage to many plants. The primary structure of the proteins contains a highly repetitive domain that dominates the sequence. The domain comprises a number of 48-residue repeats, which themselves contain 3 blocks of 16 residues, the first 8 of which are identical. It is thought that the repetitive domain may be responsible for aligning water molecules in the seed crystal.

 [.........48.residues.repeated.domain..........]  / / | | \ \  AGYGSTxTagxxssli AGYGSTxTagxxsxlt AGYGSTxTaqxxsxlt  [16.residues...] [16.residues...] [16.residues...]

Reversibility scenarios

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

Evaporation Type of vaporization of a liquid that occurs from its surface; surface phenomenon

Evaporation is a type of vaporization that occurs on the surface of a liquid as it changes into the gas phase. The surrounding gas must not be saturated with the evaporating substance. When the molecules of the liquid collide, they transfer energy to each other based on how they collide with each other. When a molecule near the surface absorbs enough energy to overcome the vapor pressure, it will escape and enter the surrounding air as a gas. When evaporation occurs, the energy removed from the vaporized liquid will reduce the temperature of the liquid, resulting in evaporative cooling.

Adsorption adhesion of atoms, ions, or molecules from a substance to a surface

Adsorption is the adhesion of atoms, ions or molecules from a gas, liquid or dissolved solid to a surface. This process creates a film of the adsorbate on the surface of the adsorbent. This process differs from absorption, in which a fluid is dissolved by or permeates a liquid or solid, respectively. Adsorption is a surface phenomenon, while absorption involves the whole volume of the material. The term sorption encompasses both processes, while desorption is the reverse of it.

In thermodynamics, the triple point of a substance is the temperature and pressure at which the three phases of that substance coexist in thermodynamic equilibrium. It is that temperature and pressure at which the sublimation curve, fusion curve and the vaporisation curve meet. For example, the triple point of mercury occurs at a temperature of −38.83440 °C and a pressure of 0.2 mPa.

Most common scenarios

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 a "condenser".

Vapor A substance in the gas phase at a temperature lower than its critical point

In physics, a vapor or vapour is a substance in the gas phase at a temperature lower than its critical temperature, which means that the vapor can be condensed to a liquid by increasing the pressure on it without reducing the temperature. A vapor is different from an aerosol. An aerosol is a suspension of tiny particles of liquid, solid, or both within a gas.

Dew point temperature at which air becomes saturated with water vapor

The dew point is the temperature to which air must be cooled to become saturated with water vapor. When further cooled, the airborne water vapor will condense to form liquid water (dew). When air cools to its dew point through contact with a surface that is colder than the air, water will condense on the surface. When the temperature is below the freezing point of water, the dew point is called the frost point, as frost is formed rather than dew. The measurement of the dew point is related to humidity. A higher dew point means there will be more moisture in the air.

Condenser (heat transfer) device used to condense a substance from its gaseous to its liquid state

In systems involving heat transfer, a condenser is a device or unit used to condense a substance from its gaseous to its liquid state, by cooling it. In so doing, the latent heat is given up by the substance and transferred to the surrounding environment. Condensers can be made according to numerous designs, and come in many sizes ranging from rather small (hand-held) to very large. For example, a refrigerator uses a condenser to get rid of heat extracted from the interior of the unit to the outside air. Condensers are used in air conditioning, industrial chemical processes such as distillation, steam power plants and other heat-exchange systems. Use of cooling water or surrounding air as the coolant is common in many condensers.

How condensation is measured

Psychrometry measures the rates of condensation through 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.

Applications of condensation

In cloud chambers a liquid (sometimes water, but usually isopropanol) condenses upon contact with a particle of radiation thus producing an effect similar to contrails Effect similar to contrails created in a cloud chambers.jpg
In cloud chambers a liquid (sometimes water, but usually isopropanol) condenses upon contact with a particle of radiation thus producing an effect similar to contrails

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

Distillation method of separating mixtures based on differences in volatility of components in a boiling liquid mixture

Distillation is the process of separating the components or substances from a liquid mixture by using selective boiling and condensation. Distillation may result in essentially complete separation, or it may be a partial separation that increases the concentration of selected components in the mixture. In either case, the process exploits differences in the volatility of the mixture's components. In industrial chemistry, distillation is a unit operation of practically universal importance, but it is a physical separation process, not a chemical reaction.

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. [3]

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 centers for the condensation of the vapor producing the visible "cloud" trails.

Commercial applications of condensation, by consumers as well as industry, include power generation, water desalination, [4] thermal management, [5] refrigeration, [6] and air conditioning. [7]

Biological adaptation

Numerous living beings use water made accessible by condensation. A few examples of these are the Australian thorny devil, the darkling beetles of the Namibian coast, and the coast redwoods of the West Coast of the United States.

Condensation in building construction

Condensation on a window during a rain shower. Window in Ireland.jpg
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, weakening of mortar and masonry walls, and energy penalties due to increased heat transfer. To alleviate these issues, the indoor air humidity needs to be lowered, or air ventilation in the building needs to be improved. This can be done in a number of ways, for example opening windows, turning on extractor fans, using dehumidifiers, drying clothes outside and covering pots and pans whilst cooking. Air conditioning or ventilation systems can be installed that help remove moisture from the air, and move air throughout a building. [8] The amount of water vapour that can be stored in the air can be increased simply by increasing the temperature. [8] However, this can be a double edged sword as most condensation in the home occurs when warm, moisture heavy air comes into contact with a cool surface. As the air is cooled, it can no longer hold as much water vapour. This leads to deposition of water on the cool surface. This is very apparent when central heating is used in combination with single glazed windows in winter.

Interstructure condensation may be caused by thermal bridges, insufficient or lacking insulation, damp proofing or insulated glazing. [9]

See also

Phase transitions of matter ()
Four Fundamental States of Matter.pngTo
Solid Liquid Gas Plasma
FromSolid Melting Sublimation
Liquid Freezing Vaporization
Gas Deposition Condensation Ionization
Plasma Recombination

Related Research Articles

Water vapor gaseous phase of water; unlike other forms of water, water vapor is invisible

Water vapor, water vapour or aqueous vapor is the gaseous phase of water. It is one state of water within the hydrosphere. Water vapor can be produced from the evaporation or boiling of liquid water or from the sublimation of ice. Unlike other forms of water, water vapor is invisible. Under typical atmospheric conditions, water vapor is continuously generated by evaporation and removed by condensation. It is less dense than air and triggers convection currents that can lead to clouds.

Dehumidifier

A dehumidifier is an electrical appliance which reduces and maintains the level of humidity in the air, usually for health or comfort reasons, or to eliminate musty odor and to prevent the growth of mildew by extracting water from the air. It can be used for household, commercial, or industrial applications. Large dehumidifiers are used in commercial buildings such as indoor ice rinks and swimming pools, as well as manufacturing plants or storage warehouses.

Sublimation (phase transition) transition of a substance directly from the solid to the gas phase

Sublimation is the transition of a substance directly from the solid to the gas phase, without passing through the intermediate liquid phase. Sublimation is an endothermic process that occurs at temperatures and pressures below a substance's triple point in its phase diagram, which corresponds to the lowest pressure at which the substance can exist as a liquid. The reverse process of sublimation is deposition or desublimation, in which a substance passes directly from a gas to a solid phase. Sublimation has also been used as a generic term to describe a solid-to-gas transition (sublimation) followed by a gas-to-solid transition (deposition). While a transition from liquid to gas is described as evaporation if it occurs below the boiling point of the liquid, and as boiling if it occurs at the boiling point, there is no such distinction within the solid-to-gas transition, which is always described as sublimation.

Heat pipe

A heat pipe is a heat-transfer device that combines the principles of both thermal conductivity and phase transition to effectively transfer heat between two solid interfaces.

Cloud physics Study of the physical processes in atmospheric clouds

Cloud physics is the study of the physical processes that lead to the formation, growth and precipitation of atmospheric clouds. These aerosols are found in the troposphere, stratosphere, and mesosphere, which collectively make up the greatest part of the homosphere. Clouds consist of microscopic droplets of liquid water, tiny crystals of ice, or both. Cloud droplets initially form by the condensation of water vapor onto condensation nuclei when the supersaturation of air exceeds a critical value according to Köhler theory. Cloud condensation nuclei are necessary for cloud droplets formation because of the Kelvin effect, which describes the change in saturation vapor pressure due to a curved surface. At small radii, the amount of supersaturation needed for condensation to occur is so large, that it does not happen naturally. Raoult's law describes how the vapor pressure is dependent on the amount of solute in a solution. At high concentrations, when the cloud droplets are small, the supersaturation required is smaller than without the presence of a nucleus.

Absorption refrigerator Single pressure absorption refrigeration

An absorption refrigerator is a refrigerator that uses a heat source to provide the energy needed to drive the cooling process.

An atmospheric water generator (AWG) is a device that extracts water from humid ambient air. Water vapor in the air can be extracted by condensation - cooling the air below its dew point, exposing the air to desiccants, or pressurizing the air. Unlike a dehumidifier, an AWG is designed to render the water potable. AWGs are useful where pure drinking water is difficult or impossible to obtain, because there is almost always a small amount of water in the air that can be extracted. The two primary techniques in use are cooling and desiccants.

Vapor-compression refrigeration or vapor-compression refrigeration system (VCRS), in which the refrigerant undergoes phase changes, is one of the many refrigeration cycles and is the most widely used method for air-conditioning of buildings and automobiles. It is also used in domestic and commercial refrigerators, large-scale warehouses for chilled or frozen storage of foods and meats, refrigerated trucks and railroad cars, and a host of other commercial and industrial services. Oil refineries, petrochemical and chemical processing plants, and natural gas processing plants are among the many types of industrial plants that often utilize large vapor-compression refrigeration systems.

Moisture analysis covers a variety of methods for measuring moisture content in both high level and trace amounts in solids, liquids, or gases. Moisture in percentage amounts is monitored as a specification in commercial food production. There are many applications where trace moisture measurements are necessary for manufacturing and process quality assurance. Trace moisture in solids must be controlled for plastics, pharmaceuticals and heat treatment processes. Gas or liquid measurement applications include dry air, hydrocarbon processing, pure semiconductor gases, bulk pure gases, dielectric gases such as those in transformers and power plants, and natural gas pipeline transport.

An evaporator is a device in a process used to turn the liquid form of a chemical substance such as water into its gaseous-form/vapor. The liquid is evaporated, or vaporized, into a gas form of the targeted substance in that process.

Heat pump and refrigeration cycle Mathematical models of heat pumps and refrigeration

Thermodynamic heat pump cycles or refrigeration cycles are the conceptual and mathematical models for heat pumps and refrigerators. A heat pump is a machine or device that moves heat from one location at a lower temperature to another location at a higher temperature using mechanical work or a high-temperature heat source. Thus a heat pump may be thought of as a "heater" if the objective is to warm the heat sink, or a "refrigerator" if the objective is to cool the heat source. In either case, the operating principles are identical. Heat is moved from a cold place to a warm place.

Vapor-compression desalination (VC) refers to a distillation process where the evaporation of sea or saline water is obtained by the application of heat delivered by compressed vapor.

Pumpable ice technology

Pumpable ice (PI) technology is a technology to produce and use fluids or secondary refrigerants, also called coolants, with the viscosity of water or jelly and the cooling capacity of ice. Pumpable ice is typically a slurry of ice crystals or particles ranging from 5 to 10,000 micrometers (1 cm) in diameter and transported in brine, seawater, food liquid, or gas bubbles of air, ozone, or carbon dioxide.

Membrane distillation (MD) is a thermally driven separational program in which separation is enabled due to phase change. A hydrophobic membrane displays a barrier for the liquid phase, allowing the vapour phase to pass through the membrane's pores. The driving force of the process is given by a partial vapour pressure difference commonly triggered by a temperature difference.

Hygroscopic cycle

The Hygroscopic Cycle is a thermodynamic cycle converting thermal energy into mechanical power by the means of a steam turbine. It is similar to the Rankine cycle using water as the motive fluid but with the novelty of introducing salts and their hygroscopic properties for the condensation. The salts are desorbed in the boiler or steam generator, where clean steam is released and superheated in order to be expanded and generate power through the steam turbine. Boiler blowdown with the concentrated hygroscopic compounds is used thermally to pre-heat the steam turbine condensate, and as reflux in the steam-absorber.

Heat engines, refrigeration cycles and heat pumps usually involve a fluid to and from which heat is transferred while undergoing a thermodynamic cycle. This fluid is called the working fluid. Refrigeration and heat pump technologies often refer to working fluids as refrigerants. Most thermodynamic cycles make use of the latent heat of the working fluid. In case of other cycles the working fluid remains in gaseous phase while undergoing all the processes of the cycle. When it comes to heat engines, working fluid generally undergoes a combustion process as well, for example in internal combustion engines or gas turbines. There are also technologies in heat pump and refrigeration, where working fluid does not change phase, such as reverse Brayton or Stirling cycle.

References

  1. 1 2 IUPAC , Compendium of Chemical Terminology , 2nd ed. (the "Gold Book") (1997). Online corrected version:  (2006) " condensation in atmospheric chemistry ". doi : 10.1351/goldbook.C01235
  2. Schiermeier, Quirin (2008-02-28). "'Rain-making' bacteria found around the world". Nature. Retrieved 2018-06-21.
  3. FogQuest - Fog Collection / Water Harvesting Projects - Welcome Archived 2009-02-23 at the Wayback Machine
  4. Warsinger, David M.; Mistry, Karan H.; Nayar, Kishor G.; Chung, Hyung Won; Lienhard V, John H. (2015). "Entropy Generation of Desalination Powered by Variable Temperature Waste Heat". Entropy. 17 (11): 7530–7566. Bibcode:2015Entrp..17.7530W. doi:10.3390/e17117530.
  5. White, F.M. ‘Heat and Mass Transfer’ © 1988 Addison-Wesley Publishing Co. pp. 602–604
  6. Q&A: Microchannel air-cooled condenser; Heatcraft Worldwide Refrigeration; April 2011; "Archived copy" (PDF). Archived (PDF) from the original on 2012-04-17. Retrieved 2013-02-20.CS1 maint: Archived copy as title (link)
  7. Enright, Ryan (23 Jul 2014). "Dropwise Condensation on Micro- and Nanostructured Surfaces". Nanoscale and Microscale Thermophysical Engineering. 18 (3): 223–250. doi:10.1080/15567265.2013.862889.
  8. 1 2 "Condensation". Property Hive. Archived from the original on 2013-12-13.
  9. "Condensation around the house - what causes condensation". diydata.com. Archived from the original on 2008-01-13.
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