Development of Rectifying Circuit with Mixed Refrigerants

Yuji Yoshida shigeo suzuki Yuji Mukai Kazuo Nakatani Katsuhiko Fujiwara* Matsushita Electric Industrial Co., Ltd. Central Research Laboratory 3 15 Yagumo-Nakamachi Moriguchi, Osaka 570, JAPAN *Air-conditioner Division The use of mixed refrigerants for heat-pump cycles h ave attracted the attention of the International Energy Agency as an important subject of heat-pump technology and its re search and developments have been promoted all over the world. We have tried to apply mixed refrigerants to air-conditioners and developed an epoch-making technology for efficiently separating a nd varying the mixing ratio of the refrigerants inside the refriger ating circuit. computing programs for evaluating the thermodynamic properties of mixed refrigerants from those of the pure compon ents was developed in our laboratory and thermodynamic diagra ms such as VLE diagram, pressure-enthalpy diagram, etc., became ea sily available for our work. The mixed fluorinated refrigerants o f R22 R13B1 were proved experimentally to be promising for heatpump application in cold districts. The change of working fluid from pure R22 to the mixed refrigerants enhances the effects of an inver ter-driven compressor. The technique of estimating the compos ition of mixed refrigerants operating in our rectifying circuit we re developed too, and the calculated values almost coincide with the e xperimental values. We also developed a small rectifier with new coiled packings. Effects of shapes of packings and diameters of colum n were examined by an experimental rectifier alone. The separation characteristics of the packed rectifier, 15 o in diameter and 210 mm in height, cooled at the top by 60 kcaljh, was about six times as much as the equilibrium separation characteristics. In case of Rl3B1 R22, this result corresponds to 70% versus 5% separation of Rl3Bl. In our original refrigerating circuit of air-to-air heat-pump, the bottom of the rectifier, which is in the middle -pressure, is connected with high-pressure (condenser) and low-pr essure (evaporator) heat exchangers respectively by capilla ry tubes in parallel with the expansion device. When the expan sion device is open, it operates with charged mixed refrigerants, r esulting in larger heating capacity. When expansion device is s hut off, mixed refrigerants flow into the rectifier and rectificati on starts by vapors generated in capillary tube without heating d evices. The separated lower boiling-point refrigerant is cooled by its own refrigerating circuit and liquefied and stored in a reservoir connected to the top of the rectifier. Separation c haracteristics of the rectifier in the air-to-air heat-pump almost coincide with the results of the preliminary test of the rectifier alone. Then the heating capacity, the input wattage and the flui d pressure of the air-to-air heat-pump operating with the separate d refrigerants are decreased to a lower level and its energy effici ency is improved. We named our refrigerating circuit with "the rectifie r the "Auto Mixed Freon" method. The newly developed rectifier for commercial models is so small that it is easily installed in th e conventional outdoor unit. "Auto Mixed Freon" air conditioner CS -223GR came into the market in Japan in 1986 November for the first t ime.