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    Flash and Unit Operations

Flash

The flash options in PVTsim comprise:

  • PT (Pressure - Temperature)
    • PT non-aqueous
    • PT aqueous
    • PT multi phase
  • PH (Pressure - Enthalpy)
  • PS (Pressure - Entropy)
  • VT (Volume - Temperature)
  • UV (Internal Energy - Volume)
  • HS (Enthalpy - Entropy)
  • K-factor (Equilbrium factors for each component)
  • Split-factor (Split factors for each component)
  • P-Beta (Pressure - Vapor mole fraction of non-aqueous phases)
  • T-Beta (Temperature - Vapor mole fraction of non-aqueous phases)
  • Saturate with water (Saturate the current fluid with water at given pressure and temperature)

The PT non-aqueous, K-factor, and Split-factor flash options consider only non-aqueous components. The PT multi phase option considers up to four fluid phases. The remaining flash options consider gas, oil and aqueous phases.

Simulation results are presented in spreadsheet form. The data may be manipulated and plotted using built-in functions, or they may be exported to Excel or other Windows software for further manipulation.

The output from a flash includes:

  • Phase amounts (mole%, weight%, and volume%) and compositions
  • Molar volume, density, and Z-factor
  • Enthalpy, entropy, Cp and Cv
  • J-T coefficient and velocity of sound
  • Viscosity, thermal conductivity, and surface tension

Volumetric properties are derived from the selected equation of state. The thermal properties are derived from a combination of special ideal gas models and the selected equation of state. The viscosity and thermal conductivity are calculated using either a corresponding states model (Pedersen modification) or the Lohrenz-Bray-Clark correlation. Phase compositions from a flash may be saved in the database and used in new simulations.

Phase envelope

The phase envelope option may be applied to locate dew and bubble point lines as well as inner quality lines. The latter being e.g. corresponding P,T values with a user specified vapor mol or vapor volume fraction. The user may choose between P-, T-, H-, S-, V-, and U-values on either axis.

The phase envelope option may also search for 3-phase regions (one gas and two liquids) inside the outer phase envelope. Three phases may be found if the mixture contains heavy aromatic compounds, or it may simply be the results of a heavy regression. If the mixture contains water or fluid hydrate inhibitors the phase envelope option will locate the water dew point like in addition to the hydrocarbon phase envelope.