As a refrigerant used for a refrigeration cycle, carbon dioxide (CO_2) is regarded. In the case that CO_2 is used as a refrigerant, a gas-liquid two-phase flow ejector is very important. The gas-liquid two-phase flow ejector consists of a driving flow nozzle, a suction chamber, a mixing section and a diffuser. It is important for optimally designing the driving flow nozzle of the two-phase flow ejector to make clear the acceleration characteristics of the high speed gas-liquid two-phase flow. However, there is only a few study examples to evaluate the acceleration performance reasonably. Therefore, the purpose of this study is to measure the acceleration characteristics and temperature distribution in the CO_2 gas-liquid two-phase flow nozzle of the CO_2 two-phase flow ejector by experiment. In the experiment, CO_2 is blown down through the convergent-divergent nozzle and is discharged into the atmosphere. Visualization of the nozzle flow has been carried out by Particle Image Velocimetry (PIV). Temperature measurement has been carried out by thermocouples. Obtained velocity distribution of gas-liquid two-phase flow nozzle have been considered as the droplets velocity. By the experiment, these velocity distributions in parts of the nozzle and these temperature distributions in the nozzle are obtained. Therefore, the flow acceleration in the nozzle divergent part is clarified by the experimental work.
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