Ekmekçi, İsmail2019-08-232019-08-232016https://hdl.handle.net/11467/2916Natural refrigerants are the most significant alternatives in refrigeration systems nowadays. The CO2 presents an effective solution regarding with environmental effects and CO2 has been widely used in the developing stages of the cooling industry. However, it has been replaced by halocarbon refrigerants due to the drop in coefficient of performance that emerge due to heat transfer around and above the critical point, as well as high operating pressures. The harmful effects of halocarbon refrigerants on the environment have in turn led to a return to CO2 as an alternative, natural refrigerant. The current machine and exchanger technology, and system control elements have enabled CO2 to reach competitive levels in terms of efficiency particularly in northern countries through the transcritical cycle, and in the southern countries through the subcritical cascade cycle. Due to its low critical temperature and high critical pressure, R744 (CO2) has some additional technical requirements to other conventional refrigerants. In this study, thermophysical properties, required cycles, benefits and disadvantages of CO2 have been discussed.eninfo:eu-repo/semantics/openAccessConference Object