About refrigeration system.Refrigeration is the branch of science, which deals with study of removing heat from space or substance whereas air-conditioning deals with study of maintaining the controlled condition of space. If the equipment is used only for human comfort or industrial air conditioning then it is known as air conditioning equipment. The word refrigeration carries the meaning of low temperature or very low temperature application, which can extend unto –60 degree Celsius or lower. One of the best refrigerant s for refrigeration application is undisputedly ammonia. It has very high latent heat, low specific volume and low cost. Ammonia can not be used with materials such as copper, cupronickel, bras etc and needs only materials such as steel or alluminium..The equipment sizes, weights and volumes are generally very high. One of the only outstanding disadvantages of ammonia is that it cannot be used in areas where a large number of people are present. Amminia is therefore restricted to industrial application, which is relatively away from residential areas. Apart from ammonia a lot of hfc’s can be used such as R 404a,R 407C,r410A etc. Refrigeration is broadly classified as vapor compression system and vapor absorption system. Vapor absorption system has low cop than vapor compression system. Vapor compression system is commonly used system for processes. In all field there is large application of refrigeration systems.