Low charge R290-subcooler to improve the performance of R744-refrigeration systems

At high ambient temperatures (above about 27°C), R744 refrigeration systems operate in transcritical mode, resulting in a significant increase in flash gas production during throttling. This results in a decrease in R744 cooling capacity and efficiency, as well as system oversizing to ensure that the cooling demand can be met at high ambient temperatures. To improve the performance of R744 refrigeration systems in transcritical operation, mechanical subcooling using R290 refrigeration cycle(s) (“module(s)”) is a promising solution. In order to comply with current standards, a maximum refrigerant charge of 150 g in a R290 module should not be exceeded. Within the project “SEPCOO” a commercial R744 refrigeration system with a capacity of approximately 50 kW was equipped with three charge-minimized R290 modules. This contribution presents the main findings of the analysis of the interaction between the R290 modules and the R744 system, based simulation and experimental data.