Thermodynamic analysis of CO2 booster refrigeration systems of supermarket applications for Türkiye

Refrigeration systems account for nearly half of the electricity consumed by supermarkets, which are essential in developed societies. In order to reduce the electricity consumption of these systems as well as their contribution to global warming, CO2 booster refrigeration cycles have been developed. This thesis discusses three different CO2 booster refrigeration cycles that stand out for their high energy efficiency, economic feasibility, and environmental friendliness. These cycles are the CO2 standard booster cycle (BSÇ), the booster refrigeration cycle with the flooded evaporator (BSÇ-YAS), and the booster refrigeration cycle with the flooded evaporator and parallel compressor (BSÇ-YAS-PAR). Mathematical models of the cycles were generated, and energy analyzes were performed using Engineering Equation Solver (EES) software. The power consumption and coefficient of performance (COP) values of the cycles were calculated for different environmental conditions and the results were compared. Additionally, annual energy consumption, installation and operating costs, and CO2 emission amounts of the cycles are calculated for 12 selected cities in Türkiye. The results were compared with the reference refrigeration system using R404A refrigerant, which is commonly used in supermarkets. It was determined that the COP of the CO2 refrigeration booster systems decreased as the ambient temperature increased under the investigated operating conditions. BSÇ-YAS-PAR has the highest COP (up to 15.1% according to BSÇ, 11.2% according to BSÇ-YAS, 66.7% according to the R404A reference refrigeration system) up to 30 °C ambient temperature. Above this temperature, it has been found that the R404A reference refrigeration system has the highest COP value (up to 29.1% according to BSÇ, 19.6% according to BSÇ-YAS, 8.5% according to BSÇ-YAS-PAR). When the annual energy consumption values of CO2 booster refrigeration cycles are compared, it was determined that BSÇ has the highest energy consumption, while BSÇ-YAS-PAR has the lowest energy consumption. BSÇ-YAS-PAR was the cycle with the highest saving (2.2%-19.4%) as compared to the R404A reference refrigeration system in all cities considered. It was determined that the investigated CO2 booster refrigeration cycles have lower emission values between 23.4% and 52.2% than the R404A reference refrigeration system.