Recently, industrial system using natural refrigerants have been researched. Among them, carbon dioxide has a small pressure ratio compared to existing refrigeration systems because it has a relatively high operating pressure. And the effect of pressure loss on the performance of the system is small compared to other systems. Also it is eco-friendly because the global warming potential is low.
The pressure control valve is used in all parts of refrigeration and air-conditioning cycle (when fluid state is gas, liquid and two-phase states.). However the analysis model of the pressure control valve for CO2 refrigerant, which was previously developed, has the disadvantage of being able to be analyzed only when it is in the gas state. Therefore, in this study, the analysis model of pressure control valve for CO2 refrigerant was developed considering phase change to supplement for the shortcomings of the analysis model developed previously.
This paper is composed of 5 chapters, and the summary of each chapter is as follows.
In Chapter 2, it was to describes refrigerant properties and the density equation, mass flow equation, etc. used in the analysis model considering phase change. The shape and structure of the pressure control valve, which is used in this study, are also shown through a sectional view. Also fluid flow and operating principles within the valve were described and mathematical modeling was performed to analyze the dynamic behavior.
In Chapter 3, the components inside the valve were shaped by considering the structure, flow path and shape of the pressure control valve described in Chapter 2, and the analysis model was developed setting considering operating principles the parameters of each component. In particular, this analysis model used the Helmholtz free energy equation to take into account the properties of the actual CO2. This analysis model was simulated to test whether phase change was considered. As the result, it was analyzed refrigerant properties and dynamic behavior.
In Chapter 4, experiments were conducted to verify simulation models developed in Chapter 3, and experiments were conducted with dry air using compressors. The test was conducted by adjusting the pressure on the inlet and outlet sides of the pressure control valve to the proportional pressure control valve. To compare the results of the experiment with the analysis model, simulations were conducted with the same experimental conditions. As a result, it was compared results of experiment and simulation.