The new system uses the HFC refrigerant R407C in both of the primary and secondary refrigerant circuits. The refrigerant R407C has 0 of the Ozone Depleting Potential. The reliability of all the system is also improved to a large degree.
The heat drive pump (HD pump) illustrated in Fig.7.2 is the pump which makes use of the relation ship between the saturation temperature and the saturation pressure of the refrigerant. As an example, the operating principle of the pump at cooling is explained as follows. When the vapor refrigerant in the heat drive tank B shown in the left side figure is cooled, it is decompressed and the tank B sucks in the liquid refrigerant from the room unit through the refrigerant / refrigerant heat exchanger. On the other hand, when the liquid refrigerant in the left side tank A shown in the same figure is heated, it is compressed and the tank A discharges the liquid refrigerant to the room unit. Before long, when the liquid level sensor detects the empty of the drive tank A and the fill-up of the drive tank B, all of open valves in the same figure are closed and all of closed valves are opened. As a result, the roles of the drive tank A and B trade places as shown in the right side figure. As mentioned above, the drive tank alternates suction and discharge automatically and this HD pump is able to transfer the refrigerant continuously.
The HD pump consists of the drive tanks, the heat exchangers, the check valves and the solenoid valves. It does not have any rotating parts such as the mechanical pumps. it does not need to be lubricated. It has a long life. Also cavitation does not occur. It has the high degree of freedom of the installation. It is expected that this system can be adapted to the air conditioning system using the new refrigerant for large vessels.
7.2 Development of Magnetic Refrigeration at Temperature of Hydrogen Liquefaction2)
Liquid hydrogen is being used not only as rocket fuel but as clean energy. When hydrogen demands increase, a major issue will be the reduction of liquefaction cost. In view of such needs. Mitsubishi Heavy Industries, Ltd. studied application of the magnetic refrigeration cycle to hydrogen liquefaction and conducted an experimental study of magnetic refrigeration operating in a Camot cycle. Consequently, they could indicate the possibility of practical hydrogen liquefaction by magnetic refrigeration.
