A mathematical model for metastable condition determination in highly flashing liquid flows through expansion devices

The determination of the metastability condition in fluid flows through singularities (expansion devices) when flashing occurs is the key to determine the mass flow rate going through devices when there is a great pressure difference between upstream and downstream. An application of the evaporation waves considered together with a maximizing condition for the pressure jump through the wave to determine the metastable state is presented. The model results are compared to several outflows reported in the literature indicating values within engineering standards for those flows in which fluids are highly superheated (highly expanded flashing liquid jets).

► A mathematical model to determine the metastable flow degree in expansions.
► This model is based on the evaporation wave theory and a pressure jump discontinuity condition.
► The proposed model is not appropriate in cases where is present a low intensity evaporation wave.