CO2 (R-744)
Carbon dioxide was widely used refrigerant from the end of XIX and XX century. Thanks to its complete harmlessness it was, as a rule, the preferred choice for use on Board ships, while ammonia more common in stationary applications. With the advent of the "Freon" and R-12, first of all, CO2 quickly refused, and she almost forgot during the last 40-50 years. The main reasons for this development were, of course, the rapid loss of power at high temperature of the cold water in the tropics, and, not least, the inability of producers to follow the latest trends in compressor design more compact and price effective high-speed species. The time for the revaluation of this refrigerant for use with the use of modern technologies.
CO2 is naturally present throughout the environment. Air contains about 0.35 ppm, a total of 300 billion tons for the whole atmosphere, and several hundred billion tons per year circulate in the life of the biosphere.
No complicated and time-consuming research is needed to make sure it is complete harmlessness.
One may object that CO2 is a greenhouse gas, and this, of course, correct, although its global warming potential is defined as 1, and GWP refrigerant indexed. But in reality, the gas will be used, which is already available as a waste in unlimited quantities from other activities. What we do is just postpone its release. This is, in principle, good for the environment as planting trees to bind carbon over a period of time.
As for my personal safety, CO2 (at least the best of the halocarbons. It is not toxic, incombustible, of course. About the release of liquid make up about half evaporates, and the rest hardens in the form of snow and can be removed with a broom and dustpan, or simply left to sublimate. Most people are already familiar with how "dry ice". In case of accidental loss of a large number of good ventilation system you want to avoid any risk of suffocation, in particular, in the spaces below ground level. In this respect, the situation is the same as for any large chladone plant.
Sometimes argued that high pressure CO2 can be especially dangerous in case of accidental rupture. Actually it is not so, because the amount is so small. The burst of energy similar to the product P x V, approximately the same for all systems, with the same capacity, regardless of the refrigerant. CO2 also has a number of additional advantages, such as the following:
- non-flammable, not explosive, non-toxic,
- low cost and good accessibility,
- having zero ODP and 1, as GWP,
- thermal stability,
- pressure close to the economically optimal level
- significantly reduced compression ratio compared to conventional refrigerants,
- full compatibility for normal lubricants and General machinery, construction materials,
- easy availability everywhere, regardless of any supplies of monopoly, and
- easy operation and maintenance, lack of "disposal" requires a very low price.
Its only a technical disadvantage is the high triple point temperature and low critical temperature. Thus, CO2, as a pure substance can not be alternative refrigerant.
CO2 as a refrigerant, the huge potential for the development of energy-efficient and cost-effective systems. Examples demonstrated that for some applications and related technologies for the other areas, we will be found. This substance is very close to the ideal refrigerant and a quick revival of this popularity for use in a wide field can be expected. CO2 now replaces the following:
- R-13, R-13B1, and R-503 in very low temperatures (modernization and new),
- R-13, R-13B1, and R-503 in the industrial process refrigeration (modernization and new), and
- R-11, R-12, R-113, R-114, R-115 in non-mechanical systems (modernization and new).
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Refrigerants