EBSILON®Professional Online Documentation
The "Simulation" button or the "Simulation" menu item in the main menu "Calculation" is used to perform the simulated for a selected profile, e.g. for the "Design" profile, followed by the sub profiles.
EBSILON®Professional uses a matrix solution process. This requires the linearisation of all dependencies. To consider influences resulting from non-linearities, a Newton iteration is performed afterwards. This iteration is considered completed, if the deviation from the previous iteration step is smaller than the specified precision value for all matrix cells.
The functionalities described below apply to both simulation and validation calculations.
This dialogue is displayed if the "Show simulation progress" setting is selected under "Show message box during/after calculation" in the General Options -->Calculation --> General.
A simulation can take several minutes for larger models with poor convergence properties or when using calculation time-intensive material value tables. The calculation can be interrupted by pressing the "Escape" button. The calculation is then cancelled after the simulation step that is currently running.
It is possible to have all or selected profiles calculated with one command and to obtain an overview of the success of the individual calculations.
This is done by means of the multi-simulation dialog that can be activated with Calculation/Multi-Simulation… or View/Toolbars/Multi-Simulation.
In the first line of the dialog on the left side it is possible to select the profiles that are to be considered in the dialog. By default, all profiles are selected here. The button “Start simulation” then serves to run the simulation for all selected profiles. For each calculated profile then the calculation status, the number of required iteration steps, the required computing time, and the number of errors, warnings, and comments is displayed in the table.
Then in the button “Options” it is possible
By double-clicking on a line of the table you can directly change to the corresponding profile. By double-clicking on a column headline, the table is first sorted in ascending and
then in descending order according to the respective entry.
In the multi-simulations dialog only the number of errors, warnings, and comments is displayed. Which ones they are is shown in the error dialog, which has been expanded
by a column “Profile” on the left. Via a button you can select whether you only want to see the error messages of the latest calculated, of the current, or of all profiles.
For a fast calculation of the profiles, all message and dialog boxes are suppressed during the calculation. Therefore, it is not possible to confirm the transfer of reference values
for global and local design calculations, even if “show dialog box” is selected in the calculation section of the global options. If it is desired to transfer reference values automatically
during the execution of a multi-simulation, you have to switch the global options to “Yes” and “Write local design data to active profile” or “Write local design data to
root profile”.
Error Messages
Errors in components 1 or 33
Component 1 and 33 can be used to specify the value triplet P/T/H. The pressure P must be defined within the component or at another place within the system. If P is known from another place, no value need be specified within the component. If P is known, either the temperature T can be derived from the enthalpy H or H from T. If T is to be derived from H, H must be specified within the component under consideration, and T must be set to 0 (zero). If H is to be derived from T, T must be specified within the component under consideration, and H must be set to 0 (zero). Zero indicates in this context that the quantity must be calculated within the component 1 or 33. An error is indicated if T is specified as well as H. This is an over-determination.
Missing Start Value
Essentially, there are three reasons for a missing start value.
Reason 1: In the design mode, the final state of the steam turbine expansion must be specified. All intermediate pressure stages are defined within the separate steam turbine sections by defining the corresponding inlet pressures. The final state of expansion must be defined directly before the turbine condenser with a component of type 33 on the exhaust steam pipeline by specifying the final pressure.
Reason 2: A controller component (12 or 39 or 69) needs a starting value for the quantity to be corrected, at the position where the controlling correction is to be done. This can be achieved either by using a component of type 33 or by declaring a specification value within the controller component.
Reason 3: A steam drum (component type 20) needs a starting value for the expected steam production. The estimated value can be fairly rough and may differ by a factor of 10 from the correct value. The definition of the estimated value is performed either by a component of type 33 on the condensate inlet (Economizer after the drum) or by defining the corresponding specification value within the drum component itself.
Missing mass flow
In many cases, a whole chain of lines is coloured owing to a missing mass flow information. To correct this, a component of type 33 with a mass flow specification can be placed on a suitable line. It is principally insignificant where the component of type 33 is placed within a chain of coloured lines, but plausible places should be preferred (e.g. feed water inlet to the boiler, live steam behind the boiler and others).
Missing pressure
To correct this, a component of type 33 with a pressure specification can be placed on a suitable line.
Missing enthalpy
To correct this, a component of type 33 can be placed on a suitable line, which then specifies either the enthalpy (T must be set to 0) or the temperature (H must be set to 0).
Over-determination in mass flow
This error appears, if there are mass flow definitions at two different places of the cycle, although one definition would be sufficient. The difference between these two (or more) definitions is indicated. If this difference is not 0, it is becomes necessary to eliminate this error. This may be difficult in some situations, because the error analysis may detect consequences at places far away from their real reason. However, because of mathematical reasons there is always one "Double Mass Flow” entry with difference zero within a closed system. You can ignore this message.
Over-determination in pressure
This error appears, if there are pressure definitions at two different places within the system, although one definition would be sufficient. The difference between these two pressures is indicated. If this difference is not 0, it becomes necessary to eliminate this error. This may be difficult, because the error analysis may detect consequences at places far away from their real reason.
Over-determination in enthalpy
This error appears, if there are enthalpy definitions at two different places within the system, although one definition would be sufficient. The difference between these two enthalpies is indicated. If this difference is not 0, it becomes necessary to eliminate this error. This may be difficult, because the error analysis may detect consequences at places far away from their real reason.
Negative mass flow
It is essential to eliminate this error. The reason might be the request for more outlets then inlets within a splitter. Mass balancing then sets one of the outlets to a negative value.
Negative pressure
A negative pressure can be the result of a very high pressure drop within a component, which does not fit to the absolute pressure level. EBSILON®Professional cannot process pressures less than 0.01 bar.
Negative enthalpy
EBSILON®Professionalcannot process negative enthalpies, if they deviate from those defined by the lower limits of the steam table or other material tables. The lower limit of water/steam is 0 °C, of air and flue gas is 30°C.
Component comments
These messages are not errors. They occur when limits or restrictions have been reached, which could be intercepted by the software without affecting the results.
Component warnings
These messages are not errors too, but you should try to find out the reasons and decide whether to accept them or not.
Component errors
These messages indicate errors. You have to find out the reason of each error and correct it. Mostly these messages result from modeling errors or carelessness in process technology.
Measuring points for composition
Compositions can be specified on inlet lines or behind a physical properties separator. When compositions were specified on other lines, these were tacitly overwritten by other components. As this is no longer ensured in Release 10 in connection with the parallelization, there may be an error message. In this case, the user has to switch off the measuring points manually (FFU=0).