Condensation of Water Vapor

Condensation of Water Vapor


The condensation of water vapor in the atmosphere is the transition of water vapor in the air to the liquid state (droplets). In a more general sense, the term “condensation of water vapor” is applied to the transition of water vapor to both the liquid and the solid states. Sublimation is the meteorological term for the transition of water vapor to the solid state (crystals, snowflakes), while in physical science it describes the reverse process.

Water is always present in the atmosphere, where it can exist in the gaseous, liquid, and solid states simultaneously. Even though the lower atmospheric layers contain several hundred kg of water vapor per km3 of air (several thousand kg during the summer), the condensation of water vapor in the atmosphere is only possible when the vapor pressure e (or partial pressure) exceeds the saturation pressure E. The saturation pressure is primarily a function of temperature, decreasing with decreasing temperature; it is also dependent on the presence of dissolved impurities in the water as well as on the curvature of the droplet surface. For example, the smaller the water droplets, the greater the E. Usually e < E in the atmosphere, although sufficient cooling of air masses under specific conditions will cause e to exceed E. This occurs when (1) there is a drop in the temperature of air owing to adiabatic expansion during its rise, with E decreasing at the same time (most clouds are formed in this manner), (2) the air is cooled as a result of contact with a colder ground surface (fogs are often formed in this manner), and (3) water evaporates from a warmer ground surface, during which the water vapor pressure e increases to values exceeding E (evaporation mists are formed).

It is known that great supersaturation is required for the condensation of water vapor in absolutely pure air. However, the atmosphere always contains dust particles, sea salt droplets, products of partial combustion, and the like which act as condensation nuclei. These nuclei facilitate the condensation of water vapor during extremely negligible supersaturation (fractions of a percent). The direct condensation of water vapor on cloud crystals can play an important role at negative temperatures in clouds. E is considerably lower for crystals than for supercooled droplets at the same temperature; therefore, crystal growth and droplet evaporation occur in a mixed cloud composed of droplets and crystals. The condensation of water vapor on the earth’s surface and on objects on the earth results in the formation of dew, frost, rime, and the like.

The condensation of water vapor, ensuring the formation of clouds and precipitation, serves as an important link in the hydrological cycle of the earth. The heat removed from the earth’s surface during evaporation and liberated during the condensation of water vapor plays a major role in the heat transfer between the earth and the atmosphere.


References in periodicals archive ?
The above numerical model was applied to resolve the condensation of water vapor within a sponge block when the sponge block was shifted to a high temperature and humidity condition.
A fully heated assembly prevents condensation of water vapor and other heavier less volatile hydrocarbons.
The source of these vapor trails was said to be condensation of water vapor in aircraft engine exhausts.
Mission scientists at first suspected that the problem was temporary, caused by condensation of water vapor in the barrel of the 11.
The incident investigation team concluded that the leak was the result of localized internal pitting corrosion that occurred because of a combined result of: 1) The corrosive well effluent and subsequent condensation of water vapor accumulated in low areas because of low production volumes causing disruption of the normally naturally protective iron sulfide scale and inhibitor films on the pipeline surface; 2) The continuous chemical mitigation strategy failed to maintain a protective film in regions of severe stagnant water traps; and 3) The existing condition monitoring and inspection program failed to detect the presence of high-rate corrosion attack prior to the failure incident.
OSMO utilizes an innovative design and unique media to promote the condensation of water vapor from exhaled gas, transferring it to the atmosphere.
Both liquid and solid specks help clouds develop by encouraging the condensation of water vapor, which does not occur readily without an original seed particle of some sort in the air.
Prior methods and products have exclusively used condensation of water vapor from exhaled breath in attempts to develop practical clinical detection methods.
A demonstrative example of a reserve of heat losses reduction from boiler plants can be a representation of fuel combustion products cooling processes in hot water boilers without condensation of water vapors and with condensation of water vapors from gases on I-x diagram (see Fig.