IMPROVEMENTS IN A CO2 TRANSCRITICAL PLANT WORKING WITH TWO DIFFERENT SUBCOOLING SYSTEMS

摘要

Natural refrigerant CO_2 is an “old-new refrigerant” that is being implanted as a green solution againstrnhigh-GWP greenhouse gases. Its particular low critical temperature makes carbon dioxide difficult to bernimplemented in warm countries where transcritical operating conditions are commonly achieved. In orderrnto be competitive over artificial refrigerants, transcritical cycles must improve its levels of COP andrncooling capacity by using different cycle configurations mainly focused in reducing the temperature atrnthe gas-cooler exit. In this work, two different subcooling systems based on the use of an IHX and arndedicated mechanical subcooling, are presented and experimentally tested at a -10℃ evaporating levelrnunder two different heat rejection temperatures at the gas-cooler (30 and 35℃).rnWorking with IHX, the results show a maximum improvement in cooling capacity and COP rangedrnbetween [1.9 ÷ 11.7]% and [0.8 ÷ 12.2]%, respectively, with an average increment in the dischargerntemperature of 11.6 K. The same tests performed with a dedicated mechanical subcooling using R600arnas working fluid, brings an improvement in cooling capacity and COP ranged between [27.2 ÷ 42.8]%rnand [5.1 ÷ 19.3]%, respectively, with a maximum increment in the power consumption of thernrefrigerating plant of 20.9%.