Depressuring Calculation Options Window
This window allows you to input various information about the time step sizes, tolerances used for convergence, and error handling in the depressuring unit.
Volume Tolerance per Time Step
The default value for the volume tolerance per time step is 0.0001. You can enter a different value for the volume tolerance.
Maximum Number of Time Steps
The default value for the maximum number of steps allowed in the depressuring simulation is 100. You can enter a different value for the maximum number of time steps.
Time Step
The default value for the time step size is displayed. You may enter a different value for the time step size. The default value for the time step size is calculated using default values for the time step parameters. You may specify whether the default time step is calculated from the total fluid mass fraction, the vapor holdup fraction, or the smaller of the two, by clicking on the highlighted text. The default selection for time step size basis is to perform the calculations based on the total fluid mass fraction. The default value for the total fluid mass fraction is 0.04, and the default value for the vapor holdup fraction is 0.50. You may enter different values for these fractions. If a vessel contains only liquid or dense phase, the default value of time step is 0.1.
Accept Maximum Time Steps as solved
On selecting this option, the depressurizer will be shown as Solved, even if it does not reach the final depressuring condition after maximum number of time steps are reached.
If this option is not selected, then depressurizer will fail, if it does not reach the final depressuring condition after the maximum number of time steps are reached.
Isentropic Efficiency of Expansion
The isentropic efficiency is used in the blowdown calculations. You may select either the default isentropic efficiency of expansion or a user-supplied value. For all Heat Input models except for blowdown, the default value for the isentropic efficiency of expansion is 0.0. The default value for the isentropic efficiency of expansion for the blowdown models is 1.0.
Action when Errors are Detected
By default, the simulation will stop whenever current pressure exceeds relief pressure by a factor of 1.5 or if the vessel pressure begins to rise after falling. Clicking on the highlighted text will allow the simulation to continue even if pressure profile errors are detected.
Solid CO2/H2S/C6H6 Prediction
By default, the simulation will not predict the formation of Solid CO2/H2S/C6H6. Selecting this option will predict Solid CO2/H2S/C6H6 formation at all time steps. This option also prints and predicts the density of solids formed.
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