Refrigerants

In 1748, William Coolen, for the first time, refrigeration experiment was successfully carried out by creating partial vacuum over ethyl ether. This had happened in Glasgow University. Later Perkins, Gorrie and Linde during different occasions carried out extensive work in this field and some fruitful output emerged. Perkins used ether as refrigerant and developed a hand-operated vapour-compression machine. Ethyl chloride and ammonia succeeded ether and were in extensive use till 1875. During 1875-1885, sulfur dioxide, methyl chloride and carbon dioxide were tried as refrigerant and tested positive. After 30-40 years, many new refrigerants were experimented. Some examples are methane, ethylene, dichloromethane, dichloroethylene and monobromomethane. A great breakthrough occurred when fluorinated hydrocarbons (freons) were derived from hydrocarbons. Freons are never considered as ideal refrigerant materials since they are toxic and flammable. Another important aspect is the moisture- it should not be allowed to enter refrigerant systems at any cost. Taking into account all the parameters, ammonia is the best choice as refrigerant. Ammonia is the most inexpensive and environment-friendly refrigerant. Brines, glycols etc. are used as secondary refrigerants. They are used for carrying refrigerants from the plant room to the space of application. Brines are formed by dissolving salt in water. The advantage of glycol solution is that they are less corrosive.