Dr. G. Venkatarathnam is a Professor of Mechanical Engineering at the Indian Institute of Technology Madras in southern India. He holds Ph.D. and Masters degree in Cryogenic Engineering and has more than 20 years research experience in the area of Cryogenic refrigerators and liquefiers. He works in the broad areas of Refrigeration, Cryogenic Engineering and Compact heat exchangers. His research interests are in refrigerant mixtures and mixed refrigerant processes for heat pumps, refrigerators, cryocoolers (cryogenic refrigerators) and liquefiers, process simulation and optimization, and development of cryogenic heat exchangers, refrigerators and liquefiers. He has taught Cryogenic Engineering, Refrigeration and related subjects at the Indian Institutes of Technology at Kharagpur and Madras, and at the Universiti? t Karlsruhe, Germany. He also holds a few patents on refrigerant mixtures.