This calculation mode allows the user to simulate, at a specified temperature, a vessel that releases gas while maintaining the initial volume over a desired pressure range.
This feature is typically used for oil and gas systems. The system must contain some vapor at its initial conditions
(Temperature = reference temperature and Pressure = reference pressure). If this condition is not met, PRO/II will not execute the calculations.
PRO/II ends the CVD calculations when the lowest pressure (End Pressure) has been reached. However, PRO/II terminates calculations sooner if the system cannot produce any more vapor by depletion at a given pressure within the specified range. Select your reference and end conditions carefully to avoid these situations.
PRO/II produces tabular results and plots giving pressure versus the standard volume of released gas, the cumulative standard volume of released gas, the MW of the released gas, and the actual volume of the liquid left in the vessel.
Reference Temperature
Reference Pressure
These specify the reference conditions (pressure and temperature) for the computation.
Reference temperature defaults to the merged feed stream temperature.
In DROPOUT mode, the reference pressure defaults to the dew point pressure. In this mode, users often specify reference pressure as the reservoir pressure. During calculations, if the specified value is lower than the dew point pressure, PRO/II uses the dew point pressure instead of the supplied value. The user-specified value of reference pressure is not changed internally, but a warning message is issued to alert the user.
End Presssure
Specifies the lowest pressure for the DROPOUT calculations.
Number of Points or Pressure Increment
Specifies which pressure values PRO/II will use for the computation. The user may define either the number of points (N, where N <100) or a specific step size between consecutive pressure values (pressure increment). In this (CVD) mode, PRO/II determines the pressure values between the reference pressure (or perhaps the dew point pressure) and End Pressure.