CC BY
47
о
Аннотация. Хладагенты широко применялись в холодильных машинах как не угрожающие здоровью и окружающей среде, имеющие (I) отличные термодинамические свойства. В ходе исследований учеными было О установлено, что они способствуют повышению парникового эффекта и распаду озонового слоя. Создание искусственного парникового эффекта осуществляется благодаря содержанию в атмосфере Земли CO2 и хлорфторуглеродов. Содержание всех CFC во много раз меньше содержания CO2 в атмосфере, но их вред, оказываемый на окружающую среду в несколько тысяч раз больше, в связи с их долговременным пребыванием в атмосфере. Хладагенты, которые оказывали огромный вред окружающей среде, встречаются теперь крайне редко так как развитие холодильной техники не стоит на месте, а вместе с ним и безопасность окружающего нас мира становиться лучше.
Ключевые слова: атмосфера, охладитель, фреон, парниковый эффект, здоровье, хладагент.
Annotation. Coolants were widely used in refrigerators; they were characterized by excellent thermodynamic properties, which aren't menacing to health and environment. But then scientists announced that these coolants promote increase of greenhouse effect and disintegration of the ozone layer. Creation of artificial greenhouse effect is carried out thanks to the Earth atmosphere contents of CO2 and chlorine fluorine of carbons. The use of all CFC is less than the use of CO2 in the atmosphere, but its harm rendered on environment in many thousands times more in connection with their long-term disposal in the atmosphere. Refrigerants having rendered harm to environment are met now extremely seldom. This is due to the development of refrigerating equipment industry.
21
о
SCIENCE TIME
Key words: atmosphere, coolant, Freon, greenhouse effect, health, refrigerant.
Introduction
Records dating back to around 2000 B.C indicate that people knew of the preserving effects colder temperatures had on food. Naturally occurring ice was collected in the winter and stored in cold houses. Romans placed large amounts of snow into storage pits dug into the ground and insulated with wood and straw. This ice was typically only available for rich people.
The intermediate stage in the history of cooling foods was to add chemicals like sodium nitrate or potassium nitrate to water causing the temperature to fall. Cooling wine via this method was recorded in 1550. Cooling drinks came into vogue by 1600 in France.
By the end of the 17th century iced liquors and frozen juices were popular in French society. A lot of progresses were done on the understanding of temperature and heat between the 17th and the 19th century. The famous Sadi Carnot explains in a document published in 1824 the basis of "the second principle of thermodynamic". In 0 the 19th, the development of refrigeration system accelerates with James Prescott Joule, Julius von Mayer, Herman von Helmholtz, Rudolph Clausius, Ludwing Boltzmann and William Thomson. Other scientists in the 20th century worked on the development of what we call today "the compression systems".
A simple compression system includes four states: Evaporation, Compression, Condensation and Expansion. This cycle is largely used today in air conditioning and refrigeration applications. Each industry developed its compression systems according to specific constraints. In the market, we can find simple systems, double stage systems, cascade system, reversible systems, direct expansion system, indirect expansion system, air-air systems, air water system, water to water systems and so on. All these systems use natural or synthetic refrigerants. Today, the use of a given fluid is related to safety, cost, environmental and regulation constraints.
We can identify four types of compression systems.
For refrigeration [03] and air conditioning, the classification is a function of the evaporating temperature (Tev).
Low temperature systems - 40°C < Tev < -18°C
Medium temperature systems - 18°C < Tev < 0°C
High temperature systems 0 °C < Tev
For heating the classification is function of the condensing temperature (Tcond) Heat pump.
Refrigerants
A refrigerant is a compound used in a heat cycle that undergoes a phase change
22
о
SCIENCE TIME
from a gas to a liquid and back. During the phase change, it exchanges a positive or negative value of latent heat at the condenser or evaporator. The two main uses of refrigerants are in refrigerators/freezers and air conditioners. Historically, the first refrigerants used were the hydrocarbons, the CO2, SO2 and ammonia. The main problem with the hydrocarbons was their high flammability, and with SO2 or ammonia it was their toxicity. To solve safety issue, the industries developed the chlorofluorocarbons (CFCs). Non-flammable and non-toxic, they were used as refrigerants in commercial air conditioning and refrigeration systems. At the end of the seventies, it was shown by scientific community that these fluids were the main source of ozone layer depletion. To replace CFC, HCFC's were introduced as an intermediate solution. In 1989, 29 countries ratified the Montreal Protocol. CFCs and HCFCs were progressively phased-out and new generations of refrigerants, safe for the Ozone layer, namely the HFCs, were adopted. However, the HFC Global Warming Potentials (GWP) is not negligible and they contribute to greenhouse effects (<2%). In 1992, the Kyoto Protocol recommended to put in place measures to limit the emissions of global warming gases due to direct and indirect emissions. [4]
Refrigerant a very easy substance that play heat transmitter role at circulation in 0 the contour of a cooling system to take away warmth from parts with cold temperature and then to transfer it to hotter parts. H20, NH3 methyl and diethyl alcohol, etc. were the first refrigerants.
Freona (chlorofluorocarbons) is colourless liquid or gas; it is flavourless, and it is well soluble in organic solvents, in many lubricant oils and it is not soluble in water. Freon is a registered trade name of DuPont, which it uses for a number of halocarbon products. They are stable, nonflammable, moderately toxic gases or liquids which have typically been used as refrigerants and as aerosol propellants. These include the chlorofluorocarbons (CFCs) implicated in ozone depletion, but also include newer refrigerants which typically include fluorine instead of chlorine and do not deplete the ozone layer. Coolants (CFC or chlorofluorocarbons,) were widely used in refrigerators they were characterized by excellent thermodynamic properties which aren't menacing to health and environment, having. In 1980 scientists announced that these coolants promote increase of greenhouse effect and disintegration of the ozone layer. By means of greenhouse effect there is maintenance of a certain temperature of favorable activity of a man and all living on beings theEarth. The basis of the natural greenhouse effect is effect of H2O vapors on to the atmosphere of the Earth and on to the infrared radiation of our planet’s surface. If there were no greenhouse effect, temperature of our planet would be significantly lower, therefore, there wouldn't have been life. Deduction of infrared radiation is promoted not only vapors of water which is contained in air, but there are other gases, such as CO2 carbon dioxide and coolants of CFC group. Creation of artificial greenhouse effect is carried out thanks to the Earth atmosphere contents of CO2 and chlorine fluorine of carbons. The use of all CFC is
23
о
SCIENCE TIME
less than the use of CO2 in the atmosphere, but its harm rendered on environment in many thousands times more in connection with their long-term disposal in the atmosphere. Example R12 chlorofluorocarbons the 1st century or R115 having the volatilization period - 2.5 centuries are chlorine fluorine. For this reason it was decided to create a certain indicator - GWP which would test a refrigerant coolant among on degree of their environment pollution.
There are 2 groups of coolants according to the decomposing activity:
- Refrigerant coolant with high ozone the decomposing activity (ODP>1) -HFU: R11, R12, R13, R113, R114, R115, R502, R503, R12B1, R13B1, etc;
- Coolants with low ozone the decomposing activity (ODP<1 - the hydra chlorine fluorine carbons (HCFC): R21, R22, R141b, R123, R124, etc.
It was established that as the most polluting substance increasing greenhouse effect is carbon dioxide (55%). Next quantity is exposed by combustion of fuel oil, coal, gas. The collapse of the ozone layer occurs approximately, products of a coolant disappear in the atmosphere and their molecules reach the stratosphere with an interval from 1 up to 2 years, then under the influence of ultraviolet rays they break up and allocate atoms of chlorine which interact with ozone, thereby destroying this layer. The molecule of chlorine is capable to destroy to some thousands of molecules of ozone. Very strongly ozone breaks up in the lower layers of a stratosphere. It was accepted that the refrigerant coolants that aren't containing in the structure of atoms of chlorine are absolutely ozone safe. Lately "holes" in an ozone layer appeared in the northern regions they can lead to unpredictable consequences. The increase of ultraviolet raysactivity can cause harvest recession, damage to flora and fauna. In 1985 as a result of the international negotiations in Vienna theVienna convention on protection of an ozone layer of Earth was accepted. But concrete terms of this problem elimination of weren't established therefore and up to this day.Many countries try to solve this problem, they to save life on the Earth. In 1987 in Montreal the Protocol on the substances destroying an ozone layer was signed.
The influence of refrigerating agents
There is an allocation of toxically dangerous substances, such as molecules of fluorine and chlorides of hydrogen at action of big temperatures on coolants. These substances cause irritation of a mucous membrane of a nose and throat to a person, and also can cause burning in eyes. Big concentration of refrigerant vapors of the indoors can be his center near a floor surface thereby, having caused replacement of air and to cause suffocation in the person.
The R22 coolant is actual it replaced the forbidden (HFU) in 1996. It is not expensive and available and therefore it is the main refrigerating agent used in many refrigeration units.
Nowadays such coolants came to replacement to the R.V.U. as R134a, R32,
о
SCIENCE TIME
R124, etc. These mixes don't decompose the ozone layer, but they greenhouse gases. The parliament of Europe made the decision to forbid release of the refrigerators working at R22 Freon. A+ the end of the last century R134a and R12 coolants were replaced by natural gas isobutene in combination with mineral oils in Germany. This refrigerating agent got was called R600a. Its advantage is lack of any qualities having negative impact on to the ozone layer. Thereby we gained wide recognition in refrigerating equipment. Economic refrigerators of the A+ and A ++ class are still working with use of this coolant. Natural refrigerant coolant had no opportunity to be used in household refrigerators in connection with their high fire danger, however not so long ago scientists thought up the designs reducing to a minimum risk of ignition of substances by reduction of a dose of filling of the refrigerator with the coolant.
In Russia of R12 coolant was replaced by R134a.We suggests ecologically safe refrigerants of our own production, such as propane, isobutene, methyl air and their mixes: C1, CM1, and C2. C1 is similar on thermodynamic properties to R12 and it is a mix (R134/R600a/R218). All these refrigerants have neither color nor smell and they also have a high rate of fluidity. Thanks to the properties they are capable to get through micropores of usual cast iron.
There was conference of the UN In 1992 in Rio de Janeiro.And it was decided to proclaim global warming the most dangerous source causing a loss on an ecological condition of the planet. It was established that greenhouse gases such as: nitrogen oxides, the methane and other gases that have polyatomic structure. They are responsible for climate change. Participation of CFC in change of temperature on Earth for 10 last year’s makes 24%, and concedes only CO2 - 55%. The most dangerous greenhouse gases are to six fluoric it is gray, refrigerants on the basis of R218 and R318 fluorine.
Having analyzed this information, we come to the conclusion that refrigerants having rendered harm to environment are met now extremely seldom. This is due to the development of refrigerating equipment industry.
Literature:
1. Rukavishnikov A.M. Rekviem po hladagentu R22// Holodil'naja tehnika. 2012. №
6.
2. Sterling D. Morskoj transport i okruzhajushhaja sreda//JuNIDO v Rossii. 2011. №
3.
3. V.G. Bukin, A. Ju. Kuz'min. Holodil'nye mashiny, rabotajushhie na neazeotropnyh smesjah hladagentov.2003.№1.S.20-30.
4. W. Rached, J. Komornicki, C. Maldeme SAFE AND ENVIRONMENT FRIENDLY REFRIGERATION AND REFRIGERANTS [Electron resource]. - URL: http:// www.nedo.go.jp/co (date: 21.11.2015г.)
