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A large number of new application in biology, biotechnology etc. requires preservation of cells, tissues etc. at temperature down to 173K. So there is a worldwide attention to develop the system to meet this temperature.Conventional cascade vapour compression refrigerators are normally used for providing refrigeration below 230K. Generally, two cascade stages are required for temperatures down to 200K and three stages for temperatures down to 173K. As the number of stages increase, the complexity of the system, number of heat exchangers and compressors, and ultimately cost increases. Alternatively, it is also possible to use single stage refrigeration system that operates with a mixture of refrigerants to provide refrigeration at low temperatures. Such systems are known as Mixed Refrigerant Cascade (MRC) systems, or Auto Refrigerant Cascade (ARC)system.The use of a single compressor (used in domestic refrigerators and air conditioners) in a MRC refrigeration system compared to multiple compressors in cascade vapour compression refrigerator results in reduction of cost and complexity, and increases reliability.

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Prof. Kamlesh Ratre working as Assistant Professor, Department of Mechanical Engineering at Vishwavidyalaya Engineering College,Ambikapur. He obtained his B.Tech. degree in Mechanical Engineering from NIT Raipur and M.Tech. degree in Thermal Engineering from IIT Madras. He has five years of industrial and teaching experience.

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