It is very effective measures in promoting the saving energy to improve the efficiency of the refrigeration systems. We have been studying on the supersonic two-phase flow in the ejector, which can improve the efficiency of the carbon dioxide refrigeration cycle by converting the exhausted expansion energy into the useful compression energy. The performance of the ejector is affected by two fluid dynamical phenomena. One is the energy conversion efficiency of the nozzle and the other is the pressure recovery in the mixing section in the ejector. The later pressure recovery is performed by oblique shock waves to occur in the mixing section. In order to improve the efficiency of the ejector, it will be essential to elucidate oblique shock waves to occur in the two-phase flow. This paper deals with the characteristic of the oblique shock waves appeared in the supersonic two-phase flow nozzle by using the carbon dioxide gas refrigerant as the working fluid. The experimental and the analytical studies on these shock waves are carried out. In the experiment, we measured the pressure distributions of the oblique shock waves occurring at the inclined wall in divergent section of the nozzle. As the decompression pressure profiles upstream the oblique shock wave obey the isentropic theory, it is definite that the two-phase flow in the nozzle is in the equilibrium state and the supersonic condition. However, the pressure increases are measured at the flow field before and after the oblique shock waves. The analyses which assume the diameter of the droplets in the two-phase flow are 8 μm can predict the experimental results of the oblique shock waves. By comparing the experimental result of the shock wave angel with the analytical one, we conclude that the shock wave appeared at the inclined wall is in the strong branch of the oblique shock wave.

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