The present study is concerned with the phase change during rapid depressurization of fluids: the role of vapor bubbles nucleation and growth and the effect on the system fluid dynamics were modeled and experimental measurements were made. Following a control-volume approach, averaged equations governing the motion of a one-dimensional, homogeneous, no-slip two-phase flow were used considering both thermal equilibrium (equal temperature) and non-equilibrium (non-equal temperature) between the liquid and vapor phases. In the non-equilibrium model, the heat transfer from the liquid to the vapor and the corresponding mass transfer velocity were modeled. Model results were compared with experimental data for a loss-of-coolant accident in nuclear power plants: the comparison of numerical vs. experimental data showed the role of nucleation velocity during the earliest phase of rapid depressurization. The experimental study of two-phase flow in a diesel engine injection system has been carried out using a rotative pump which is operated by using a purpose-developed test-bench; pressure measurements inside the system pipes were performed using pressure transducers; moreover, an ultrasonic technique was employed to study phase change phenomena. Several measurements were performed comparing the results obtained by different experimental techniques with the model outputs.
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