Page 392 - ExtendSim User Guide
P. 392

Storage and Units
Changing the unit group
To define a block unit, in the Options tab of the Tank or Interchange block, select Define a flow unit for the group and a block unit for the block. In addition to providing fields for declaring a flow unit, this option displays a field for entering an internal block unit. It also has a field for entering the factor to convert between the flow unit and the block unit.
Tank Flow Units model
The Tank Flow Units
model is the same as
the model described on
page 338. However, the
newer model has pints,
rather than gallons, as
the block units in the
Yogurt Tank, causing
the process’s output to
be displayed in the
plotter as pints. Clicking the unit group selector button in its Options tab shows that this Tank is still part of the unit group that uses the flow unit “gallons”.
Time units
A popup menu in the Options tab allows a block’s time unit to be changed from the model default time unit to any local time unit.
If a local time unit is selected in a discrete rate block, that local time applies to the entire block but only to that block. Changing to a local time unit affects every parameter in the block, but it does not change the model’s global time unit or the time units used in any other block in the model. For more information, see “Time units” on page 604.
Changing the unit group
By default all the blocks connected to the same flow stream belong in the same unit group. However, the Change Units block has the ability to create a new unit group, causing connected blocks in a portion of the model to have a different flow unit.
Change Units block
Defining a block unit in the Tank
To change the flow units from
one part of a model to another,
use the Change Units block.
While changing a flow unit in
most blocks will change the
flow unit for the entire group,
adding a Change Units block to
the model causes a new unit
group to be created – the Change Units block’s inflow connector will be part of one unit group comprised of those blocks upstream of the Change Units block; its outflow connector will be part of another unit group comprised of those blocks downstream of the Change Units block.
The Change units from: popup menu defines the flow unit that is entering the block; the to: popup menu is for selecting or creating the new flow unit. The block has a field for entering the factor that converts the incoming flow unit into the outgoing unit, and a popup menu to select the direction the conversion should take. You can also change the time units for this block in its dialog.
Dialog of Change Units block
Discrete Rate

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