6) Materials used in the refrigeration system: For the standard conditions of say, -15 degree C in the evaporator, the condenser and the evaporator pressures are 2.37 bar and 11.67 bar respectively, which are quite moderate. Since the pressures are not very high, lightweight materials can be used for the construction of the equipment. The pressure in the evaporator is quite high so it is not necessary to expand the gas to very low pressure. This also enables high suction pressure for the compressor and lower compression ratio.
7) High discharge temperature of ammonia gas: The discharge temperature of the ammonia refrigerant from the compressor is high, hence water cooling of the cylinder heads and the cylinders of the compressor is very important. If high discharge pressure is required, it is advisable to use the multi-cylinder compressors instead of the single cylinder compressor to avoid overheating of the compressor.
8) Corrosive nature of ammonia: Anhydrous ammonia is non-corrosive in nature, however, in presence of moisture it tends to become corrosive to copper, brass and other non-ferrous materials. Thus while in halocarbon systems, copper is used predominantly in the refrigeration equipment, its use should be avoided in the ammonia refrigeration systems.
9) Miscibility with oil: Ammonia refrigerant is non-miscible with oil so it does not mix with the oil in the crankcase of the compressor. The ammonia refrigerant leaving the compressor picks up oil particles and carries them to the condenser and then the evaporator. Here these oil particles tend to reduce the heat transfer efficiency from the refrigerant. The oil separator should be installed in the evaporator to remove the oil and return it back to the crankcase.
10) Leak testing of ammonia: The leak testing of ammonia from the refrigeration system can be done either by using sulfur sticks or soap solution. When ammonia reacts with sulfur, a dense smoke is formed. To detect the leakage of ammonia from the refrigeration system, the stick is dipped into sulfur and moved around in the whole plant. The location where the dense smoke is formed can be further traced to find exact point of leakage of the refrigerant. The leak testing can also be done by applying the soap solution at the various joints of the pipeline. At the point of leakage bubbles are formed in the solution.
11) Ammonia is cheap and available readily: Ammonia is available almost everywhere and is the cheapest of all the commonly used refrigerants. These coupled with the chemical stability of ammonia, its high refrigerant effect, and non-miscibility make it ideal refrigerant for the applications and places where toxicity is not a major factor.