Near saturation steam undergoing rapid expansion is numerically studied in a series of converging diverging nozzles with and without shocks. A detailed examination of the aerodynamic and thermodynamic losses are performed for thermodynamic non-equilibrium conditions. The calculations rely on a new numerical model, previously reported, for non-equilibrium phase change with droplet nucleation. In a systematic approach, the model results are first validated versus experimentally available data and then applied to more general flow situations to assess loss mechanisms. The results indicate that for weak normal shocks situated just downstream of the nozzles throat, the aerodynamic and thermodynamic losses are roughly equivalent. As the back pressure is reduced (i.e. shocks become stronger) the aerodynamic component rapidly becomes the predominant loss mechanism. The thermodynamic loss, associated with heat transfer between the phases, increases only gradually with shock strength. This gradual increase starts from a base level of loss originating with the initial nucleation of moisture, which has a strength and location independent of back pressure.

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