Fig. 7.6 Structure of scroll compressor for R410A
The lubricating performance among the sliding parts in the compressor optimized for R410A is more important than in the R22 compressor, because the loads among these sliding parts in the former compressor are larger than in the latter. Seven properties of the lubricating oil, such as compatibility with R410A, lubricity, thermal and chemical stability, were evaluated to select it. The POE (polyall ester) oil and the PVE (polyvinyl ether) oil was selected. They were tested in the actual refrigerating machine. As a result, both the oils had good compatibility with R410A and stability. The POE oil has better lubricity than the PVE oil and the current alkyl benzene oil. The POE oil was selected as the lubricating oil for the new compressor.
As mentioned above, this new scroll compressor for R410A with low vibration and low noise has been developed.
(2) TOSHIBA Corporation has developed two models of the room air conditioner using R410A, “RAS-405BD” (4kW type) and “RAS-506BD” (5kW type). These models have used R410A as the refrigerant, because they have higher performance and efficiency than the current R22 refrigerator. The following is the reason of selecting the R410A. The R410A is a mixed refrigerant but has the azeotropic characteristics. It is a refrigerant easy to handle. The pressure in use of the R410A is 1.6 times higher than the R22. These models can be designed technically to be pressure-proof against the high pressure. Also, the R410A has zero of the Ozone Depleting Potential and 1730 of the Global Warming Potential (GWP). The GWP is almost same as the R22. Let's think the Total Equivalent Warming Impact (TEWI) of it. The TEWI means the index to evaluate the green house effect delivered totally by the air conditioning machinery. It consists of the direct effect and the indirect; the former effect is caused when the refrigerant filled in the machine is discharged in air, the latter is caused by the warming effect gases of CO2 etc. produced to get the total energy of the electric energy etc., that is necessary to operate the machine during the life. The improvement of the efficiency of each structure machine is very important on the air conditioning equipment because the indirect effect occupies about 90 per cent of the TEWI of it. Therefore, the compressor is a new one improved for R410A based on the high efficiency twin rotaries' compressor for R22. The POE (polyall ester) oil that has good compatibility with R410A and hydrolysis stability is selected as the lubricating oil of the new compressor. The compressor achieves higher efficiency than one for R22. Also the new inverter controller is developed originally to control the DC brushless motor driving the compressor. This inverter controller achieves high power factor of 99% and high efficiency by using the PAM (Pulse Amplitude Modulation) & PWM (Pulse Width Modulation) hybrid control technology.
By the other many improvements, these two models can use R410A in AC 100V/20A, and become the high efficient and high reliable air conditioners.
7.6 Development of Ultra-Low Temperature Stirling Refrigeration Unit7)
SANYO Electric Co., Ltd, has succeeded in developing the Stirling refrigerator using helium as the refrigerant, and produced “the Ultra-Low Temperature Stirling Refrigeration Unit” with the cold head for -180℃ 〜 -50℃. The construction of the cooling system is shown in Fig. 7.7. This unit consists of the Stirling cooler, the circuit for the secondary heat transfer fluid and the radiator to reject heat from the Stirling cooler. Both of the ODP (Ozone Depleting Potential) and the GWP (Global Warming Potential) of the helium as the refrigerant are zero. The helium is a non-flammable, non toxic and gentle refrigerant for the environment of the earth. Using it as the refrigerant, the refrigerator can become one without the FRON completely.
As shown in Fig. 7.8, the Stirling cooler consists of an expansion (low temperature) cylinder, a heat absorber, a regenerator, a heat rejecter, a compression (high temperature) cylinder and a driving mechanism for the pistons in the cylinders.
