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Storage and Units
Blocks of interest
As discussed in “Simulating discrete rate systems” on page 325, quantities of flow are located in one or more parts of a discrete rate model. During the simulation run, the flow moves from one location to another at the effective rate. In order for the flow to move, one or more of the model’s blocks need to have the capacity to hold flow as time advances.
The Convey Flow, Interchange, and Tank blocks are residence type blocks – they have capac- ity and can hold defined amounts of flow.
Flow units describe what is flowing from one Rate library block to another. Blocks that are connected together through flow connections and share the same flow unit are part of the same unit group. The Change Units block is used to create a new unit group. This causes the blocks downstream of the Change Units block to be in a unit group different from its upstream blocks.
This chapter discusses providing and storing flow and the use of flow units in a discrete rate model. It will cover:
• Defining a block’s flow capacity
• Indicators that provide information about a block’s level of flow
• Defining and selecting time, flow, and length units
• Using the Change Units blocks to create a different flow unit group
This chapter focuses on setting capacity for the Convey Flow, Interchange, and Tank blocks. Other aspects of those blocks are covered in different chapters:
• The Convey Flow block is most often used for delaying flow and will be discussed more fully on page page 413.
• TheInterchangeblockismainlyusedforinteractingwithitemsfromdiscreteeventportions of the model and will be discussed more completely starting on page 424.
• SettingmaximuminflowandoutflowratesfortheTankandInterchangeblocksisdescribed in page 378.
☞ The Tank Flow Unit model is located in the folder \Examples\Discrete Rate\Sources and Stor- age. The Yogurt Production model is located at \Examples\Tutorials\Discrete Rate.
Blocks of interest
The following blocks from the Rate library will be the main focus of this chapter.
Residence blocks for holding flow
Convey Flow
Delays the movement of flow from one point to another. Can accumulate flow to a maximum density, accumulate flow to fill empty sections, or act as a non-accumulat- ing conveyor.
Interchange
Represents a Tank that can interact with discrete event items. The block has two behaviors: the Tank only exists while an item is in it; the Tank is separate from the item.
Discrete Rate

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