An ejector expansion transcritical CO2 refrigeration cycle is proposed to improve the COP of the basic transcritical CO2 cycle by reducing the expansion process losses. A constant pressure mixing model for the ejector was established to perform the thermodynamic analysis of the ejector expansion transcritical CO2 cycle. The effect of the entrainment ratio and the pressure drop in the receiving ...

The relative low COP of transcritical CO2 systems caused by the throttle valve limited the further development. The replacement of a throttle valve with a turboexpander, an ejector or a vortex tube is leading to the way for improving the COP of a transcritical CO2 system. In this paper, a transcritical carbon dioxide refrigeration cycle with different expansion devices was analyzed theoreticall...

the purpose of this research is to investigate thermoeconomic optimization and exergy analysis of transcritical co2 refrigeration cycle with an ejector. after modeling thermodynamic equations of elements and considering optimization parameters of emerging temperature of gas of cooler (tgc) , emerging pressure of cooler's gas (pgc) , and evaporative temperature (tevp) , optimization of targ...

With the increasing of the environmental concerns, carbon dioxide (CO2) as an alternative refrigerant has been investigated intensively. In this study, the heating performance of a transcritical CO2 heat pump system with a twinrotary compressor was investigated. The transcritical CO2 heat pump with gas injection was tested by varying gas injection ratio and outdoor temperature at the optimum re...

The use of carbon dioxide (CO2) as a refrigerant is recently considered for an increasing number of various applications including low capacity transcritical processes. Due to the fluid properties of CO2, the pressure ratio of the refrigeration process is rather low compared to common refrigeration processes while the pressure difference is high. Furthermore, the volumetric capacity of CO2 is h...

As one of the earliest natural refrigerants, CO2 has a lot of unique advantages, such as zero ODP, negligible GWP, excellent heat transfer coefficient, high volumetric capacity, non-toxicity, non-flammability, and cost effectiveness. Since it was proposed to applying in the mobile air-conditioning, the transcritical CO2 cycle has been attracting great attentions to replace CFC and HCFC refriger...

Due to the transcritical nature, some of the test methods used in the conventional subcritical refrigeration cycle, such as the liquid refrigerant flow metering method and the water-cooled condenser metering method, are no longer appropriate for evaluating the transcritical carbon dioxide (CO2) compressor performances. This paper introduces a performance test facility taken into account both th...

The use of carbon dioxide (CO2) as a refrigerant is considered for an increasing number of various applications including low capacity transcritical processes. Due to the fluid properties of CO2, the pressure ratio of the refrigeration process is rather low compared to common refrigeration processes while the pressure difference is high. Furthermore, the volumetric capacity of CO2 is higher tha...

This paper presents the analysis of a two phase flow ejector for the transcritical CO2 cycle. A detailed simulation model of a two phase flow ejector was developed. A controllable ejector expansion device was designed, constructed, and installed in a transcritical CO2 experimental air conditioning system. System-level experimental results were obtained at different operation conditions and vari...

The interest in energy storage is currently increasing, especially from the perspectives of matching intermittent sources of renewable energy with customer demand and storing excess nuclear or thermal power during the daily cycle. Technologies to be considered for load leveling for large-scale energy systems, typically in the range of hours to days of discharge time, include pumped-storage hydr...