After the innovative development of machine refrigeration in the nineteenth century, refrigerants used as working fluid in the refrigeration machine have changed in response to safety and environmental issues. And the refrigeration systems have also been designed to adapt the refrigerants. Currently used refrigerants called the third generation are facing regulations of production amount and usage methods because of global warming. In the Kigali amendment of the Montreal Protocol, the reduction of Hydrofluorocarbons which are the most widely used refrigerants is severely scheduled for developed countries, developing countries of groups 1 and 2, respectively. To satisfy the reduction schedule of the Kigali amendment is not so easy because there is very limited number of refrigerants that have low global warming potential (GWP) and safe properties such as no flammability and lower toxicity. And, each heat pump and refrigeration system demands suitable thermophysical properties for their operating conditions. Because the numerous number of operating conditions which are temperature, capacity and others exist, newly proposed pure refrigerants cannot cover all the systems. To fit the suitable thermophysical properties with acceptable GWP and safety properties, a lot of refrigerant mixtures with two to six components have been proposed and further searches are continuously carried out. Accurate estimation of thermophysical properties of new pure and mixture refrigerants is needed for the design and simulation of refrigeration systems. Therefore, measurements of the thermophysical properties are intensively being conducted. Drop-in tests of the new refrigerants are also being conducted. In this paper, the recent situation of next generation refrigerants and refrigeration systems are briefly reported.

Dr. Akio Miyara is a Professor in the Department of Mechanical Engineering, Saga University, Japan since 2003 and a Visiting Professor in the International Institute for Carbon-Neutral Energy Research, Kyushu University, Japan since 2016. Before that, he served as a Lecturer of Ocean Thermal Energy Conversion Laboratory, Saga University from 1989 to 1991, as an Associate Professor of Department of Mechanical Engineering, Saga University from 1991 to 2003. During this period from 1993 to 1994, he studied at Stuttgart University, Germany, as a Visiting Professor. He also served as a Chairman (three times) of the Department of Mechanical Engineering, Saga University. The focused research work of Prof. Miyara in the fields of Heat transfer and pressure drop of pure refrigerants and refrigerant mixtures, In-tube condensation and evaporation, Plate type heat exchangers, Thermophysical properties of refrigerants, Heat exchangers for ground source heat pump and Numerical simulations etc. He has published more than 100 peer reviewed papers in scholarly journals, 116 papers in various International conferences and 165 papers in various Japanese local conferences. He has supervised 18 Doctoral and 75 Master theses and a significant number of undergraduate dissertations. He contributed as an Invited Presenter & Keynote Speaker over 12 International scientific conference as well as the member of International advisory committee and technical board for many conferences. He has been the technical reviewer for over 15 scientific journals. He is the member of Japan Society of Mechanical Engineering (JSME), Japan Society of Refrigerating and Air Conditioning Engineers (JSRAE), The Heat Transfer Society of Japan, The Society of Chemical Engineers, Japan, Japan Society of Thermophysical Properties, International Institute of Refrigeration. He is also the Vice-President of Transection of JSRAE, Board member (Japan chapter) of American Society of Heating Refrigerating and Air-Conditioning Engineers (ASHRAE), Editorial Advisory Board member of Journal of Applied Thermal Engineering and Counselor of JSME. He has served as the President of ASHRAE Japan Chapter; Director and Chair of different committee of JSRAE, Branch chief of the Heat Transfer Society of Japan, Chair of JSME Saga chapter etc. He conducted around 16 research projects granted from different Japanese reputed organizations such as New Energy and Industrial Technology Development Organization of Japan, Japan Science and Technology Agency, Japan Society for the Promotion of Science, Saneyoshi Memorial Foundation, and Harada Memorial Foundation etc.