CO_2冷凍サイクルを対象とした冷房成績係数および蒸発器の交換熱量に関する実験的検討 Experimental Investigation of Cooling Coefficient of Performance and Cooling Capacity in a Refrigerant System with Carbon Dioxide

本論文では，CO2冷凍サイクルを実験的に検討した．具体的には CO2質量流量，高圧側圧力および冷媒量が，冷房成績係数，蒸発器の交換熱量および圧縮機所要動力に及ぼす影響の検討を行った．その結果，CO2質量流量が増加するほど冷房成績係数は減少し，蒸発器の交換熱量は増加することを確認した．また，圧縮機回転数によらず，冷却器出口圧力が8.3 MPa近傍で冷房成績係数は極大を示した．冷却器出口圧力を測定することで冷房成績係数を向上させることが可能である．さらに，冷媒量によらず圧縮機所要動力は冷却器出口圧力に対して単調増加することがわかった．冷媒量の増加に対して冷房成績係数および蒸発器の交換熱量は増加した．

The performance of a refrigeration cycle with carbon dioxide was experimentally investigated. The effects of mass flow rate of carbon dioxide, higher side pressure and refrigerant mass on the cooling coefficient of performance, cooling capacity and compressor work were examined. Then cooling coefficient of performance decreased and cooling capacity increased with an increase in mass flow rate of carbon dioxide. The cooling coefficient of performance had maximum value at a gas cooler outlet pressure of around 8.3 MPa regardless of compressor speed. A higher cooling coefficient of performance will be obtained by controlling gas cooler outlet pressure. Furthermore, compressor work increased with an increase in gas cooler outlet pressure regardless of refrigerant mass. The cooling coefficient of performance and cooling capacity increased with an increase in refrigerant mass.