Simulation Of The Trans-critical Carbon Dioxide Refrigeration System With Semi-theoretical Models And Performance Analysis Of The Gas Cooler

Carbon dioxide (R744), as a natural work fluid, is regarded as an important substitute of refrigerant with many unique advantages. Many researchers focus their attentions on the trans-critical carbon dioxide refrigeration system.The semi-theoretical models of components in the trans-critical carbon dioxide refrigeration system based on experimental data in the open published literature were developed. The simulation program of the refrigeration system was developed based on this semi-theoretical model. Later, we studied the case in the literature and compared the simulation data and the experimental data and the results showed that the semi-theoretical model was feasible. This semi-theoretical model can be used to determine the state points of the trans-critical carbon dioxide refrigeration system and to analysis the performance of the system under variable working conditions.The analysis of the trans-critical carbon dioxide refrigeration system with the second thermal-dynamic law shows that the gas cooler is an important component in the system with substantial irreversible loss. So, to improve the performance,to decrease the irreversible loss of the gas cooler will greatly improve the performance of the whole system.The simulation model for the fin-and-tube gas cooler used in the trans-critical carbon dioxide refrigeration system was developed and the typical fin-and-tube gas cooler was studied both with lumped parameter method and distributed parameter method. The simulation data agreed well with the experimental data, which showed the validity of the model developed. We also analyzed how the changes of input parameters influenced the changes of thermo-physical properties of carbon dioxide along the flow direction and the changes of the whole performance of the gas cooler. Furthermore, with lumped parameter method, the micro-channel gas cooler was studied with two different carbon dioxide heat transfer coefficient models. An evaluation of the performance of the two carbon dioxide heat transfer coefficient models was made based on the comparison between the simulation data and the experimental data respectivelyFinally, the primary design of the multi-functional experimental platform for trans-critical carbon dioxide refrigeration system was finished. The function,the construction,the refrigeration system design,the system control method of the platform as well as the switch method among different experiments and the modulation method of parameters was also described. This has prepared for the experimental researches systemically later. This can also provide reference to the design of similar experimental platform.