Ammonia (R-717)
It is the most widely used among classic alternative refrigerants. Two characteristics of R-717, saturation ratio between the pressure and the temperature and volume flow rate per unit of cooling capacity, quite similar to R-22 and R-502. On the other hand, R-717 has some advantages in comparison with R-22 and R-502, such as cost reduction, better efficiency of the cycle, higher heat transfer coefficients, above the critical temperature, the greater resolution in the case of a leak, reducing the costs of pumping liquid to liquid recirculation systems, more tolerance to water pollution, more favorable behavior of oil, zero ODP and GWP, and less refrigerant.
After 120 years, extensive use is immense practical experience exists with this refrigerant. There is no doubt of its excellent thermodynamic and transfer properties that far exceed the halocarbons, and its important practical advantages, such as tolerance to normal lubricating oils and limited water pollution, easy leak detection and low prices.
All these factors contribute to its stable popularity and widespread use, despite the often expressed doubts about its safety.
It is true that ammonia is toxic and can burn from the air, although it is quite difficult to ignite and hardly will support the flame itself. Risk strongly counteracts the fact that she has a very strong smell and that is much lighter than air. Leakage can be easily detected by smell in concentrations far below a dangerous level, and the mass Exodus of ammonia quickly disappears up in the atmosphere. Accidents so rarely.
Failed to find any reliable statistics on refrigeration accidents. Serious cases are reported from time to time, and the impression is that they are fairly evenly divided between ammonia and halocarbons plant (Lorentzen, 1993). In recent efforts to survey the situation in Norway brought to the attention of a significant number of incidents, some of them quite serious. Over a 20-year period, only four people were killed refrigerants, two for each of ammonia and R-22. Another died in nitrogen-cooled truck. With great care and the sound of professionalism is clearly needed in designing, installation and operation of large системы cooling regardless of the refrigerant.
Whenever there is a need to avoid any risk of ammonia smell, it can easily be arranged by the inclusion of the plant into the thick enough room or building, absorbing any pair in a spray of water or on the roof-in a safe place. A secondary refrigerant (brine) should be used for distribution outside of the housing. In this case, you can use this wonderful environment safe in almost all practical applications.
Ammonia has been used successfully for generations and have proved their reliability and superior thermodynamic and transport properties. It can be applied to advantage over practically the entire range of medium and large refrigeration systems, when necessary safety requirements taken care of with a simple and clear way. Total consumption for this will be only a tiny fraction of ammonia production for other purposes...
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Refrigerants