AMMONIA AGAINST. HCFC-22
Will decide in the next few decades, designers and owners of industrial refrigeration plants in the choice of refrigerant, especially between ammonia and HCFC-22. The decision may be fast, if ammonia is not allowed the location or its inappropriate use. Codes of some cities and counties may restrict the type of the object on which the ammonia can be used. In General, its use is permitted in places separate from the premises to which the public has access. Even if no codes to legislate against it, placing a large ammonia system close to a school, a hospital, or similarly occupied the building would not be prudent. Progress in the development of packaged ammonia chillers liquids with low refrigerant charges that open opportunities for applications not previously considered, such as water chillers for air conditioning.
The first point of comparison will cost. Rates refrigerants vary and depends on the number of purchased but rough comparison on the basis of mass of ammonia, HCFC-22 and HFC-134a is shown in Fig. 1.9. Costs relative to HCFC-22 and show ammonia with the lowest cost and HFC-134a high.
Price comparison becomes a factor of plants containing tens of thousands of kilograms or pounds. The cost comparison is even more striking when he realized that to complete the plant, a certain amount (not mass) of the liquid must be granted. Since the density of the liquid ammonia, which is about half of halocarbons, only half the mass has to be purchased,
The flow volume that must be processed with the help of the compressor systems in the last three refrigerants are comparable, so there is no advantage for refrigerants. Mass flow for a given cooling capacity ammonia is 1/7, HCFC-22, and this comparison reveals itself in the pipe, the required dimensions and requirements for liquid recirculation systems. Only 1/7 of fluid must be pumped for a given cooling capacity, which means that the liquid pump can be much smaller and pumping power will be much less ammonia system.
Another factor is the case, but. The main criterion in selecting a pair of size, that decrease the saturation temperature. Compares the refrigerating capacity for pipes of various diameters and differences in the saturation temperature for HCFC-22 and ammonia. This advantage for ammonia particularly in the industrial facilities spread over a large area, where suction lines long. Or pipe size for ammonia may be less than the production of HCFC-22 or for a given size of the pipe pressure drop penalty will be less.
Ammonia is more tolerant of water that may inadvertently get into the system. Most Halocarbon systems, water is separated from the refrigerant and can freeze particularly after the expansion valve. With ammonia, however, the water remains in solution and pollution of less than 100 ppm, for example, cause no punishment for the system to work...