A phenomenological model is presented for predicting the thermodynamic conditions at the onset of flashing in liquid undergoing a static or flow depressurization transient. It is shown that at extremely high rates of decompression (pulse expansion), a liquid may reach the homogeneous nucleation limit of superheat before appreciable phase transition occurs. A criterion for pulse expansion is derived by an asymptotic solution of the mass and energy equations in conjunction with the equation for spontaneous bubble nucleation and growth near the flashing inception point. The effect of impurities and dissolved gases is considered by an empirically defined heterogeneous nucleation coefficient. The model predicts the minimum pressure at the flashing point with a probable error of less than 11 percent, using 83 experimental data points.

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