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In this paper, the new configuration of transcritical CO2 refrigeration cycle combined with a thermoelectric subcooler and an ejector (TES + EJE) is proposed. The thermoelectric subcooler is installed after the gas cooler in the transcritical CO2 refrigeration cycle with an ejector. Comparisons are carried out with the conventional transcritical CO2 refrigeration cycle (BASE), CO2 cycle with a thermoelectric subcooler (TES) and CO2 cycle with an ejector (EJE). Maximum cooling coefficient of performance (COPc) is obtained for the new TES + EJE cycle with a simultaneous optimization of subcooling temperature and discharge pressure. The improved new cycle exhibits higher COPc and lower discharge pressure compared with the other three cycles. Compared with the BASE cycle, the maximum COPc of the TES + EJE cycle is increased by 39.34% and the corresponding optimum discharge pressure is reduced by 8.01% under given operation conditions of 5 °C evaporation temperature and 40 °C gas cooler outlet temperature. The effects of the subcooling temperature, discharge pressure, gas cooler outlet temperature and evaporation temperature on the TES + EJE system performance are also discussed by energy and exergy analysis and results present here.

The new configuration of a transcritical CO2 ejector expansion refrigeration cycle combined with a dedicated mechanical subcooling cycle (EMS) is proposed. Three mass ratios of R32/R1234ze(Z) (0.4/0.6, 0.6/0.4, and 0.8/0.2) were selected as the refrigerants of the mechanical subcooling cycle (MS) to further explore the possibility of improving the EMS cycle&rsquo, s performance. The thermodynamic performances of the new cycle were evaluated using energetic and exergetic methods and compared with those of the transcritical CO2 ejector expansion cycle integrated with a thermoelectric subcooling system (ETS). The results showed that the proposed cycle presents significant advantages over the ETS cycle in terms of the ejector performance and the system energetic and exergetic performances. Taking the EMS cycle using R32/R1234ze(Z) (0.6/0.4) as the MS refrigerant as an example, the improvements in the coefficient of performance and system exergy efficiency were able to reach up to 10.27% and 15.56%, respectively, at an environmental temperature of 35 C and evaporation temperature of &minus, 5 C. Additionally, the advantages of the EMS cycle were more pronounced at higher environmental temperatures.

In this study, the performance of ice slurry production by scraped-surface method was experimentally investigated. Temperature change characteristics, ice packing fraction (IPF) of ice slurry, power consumption of scraping system and coefficient of performance (COP) were measured by varying the concentration of sodium chloride solution, scraping speed, and solution flow rate. The effect of nanosilica on efficiency of ice slurry production was also studied. The results showed that scraping power consumption accounted for only a small proportion (about 5%) of the total power consumption of the system. An increase in the concentration of sodium chloride caused a decrease in the IPF and a decrease in the COP of the system. With the solution flow rate at 1.3 m3/h and scraping speed at 13 rpm, the maximum COP (2.43) was obtained. Furthermore, the addition of nanosilica had a significant effect on improving the system COP.