Page 443 - ExtendSim User Guide
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Delaying Flow 417
Convey Flow block
You must specify in the table not
only the number of sensors
desired but also the location of
each one. (Use the +/- button in
the table’s lower right corner to
specify the number of sensors.)
The example table shown here
indicates that four sensors have
been placed along a ten foot section of the conveyor.
Sensor tab table
☞ The S connectors should be used judiciously. Extra events are used to update them at the proper time and the calculation is computationally intensive.
As discussed in “Accumulation point” on page 416, the accumulation point indicates the point beyond which no more flow can accumulate. You might want an indication when the accumu- lation point is within a particular segment of the Convey Flow block.
The Indicators tab on a Convey Flow block is used to define segments to indicate where the accumulation point is along its length. Each segment is assigned a name, a defined range, and an ID number. The ID number is used to update the block’s I (indicator) output connector as the accumulation point moves from one segment to the next.
See “Indicators” on page 351 for complete information about creating and using indicators.
☞ The I connectors should be used judiciously. Extra events are used to update them at the proper time and the calculation is computationally intensive.
When to avoid using the Convey Flow block
A Convey Flow block should be used only if the system you are modeling requires very pre- cise tracking of flow movement and position. While the block is very precise, it is also very time consuming, so use it with caution. Following are some usage guidelines:
• The travel time has to be long enough to justify using the Convey Flow block. If the impact on the result of the simulation is small, it is a good strategy to ignore any travel time delays. For instance, the amount of time required for product to traverse a pipe separating two tanks is often insignificant and should usually be ignored.
• ThedistributionofflowalongtheConveyFlowblockshouldimpacttherestofthemodelin some significant way. If the effective inflow rate varies significantly during the simulation and/or if the speed changes, the product may be unevenly distributed across the length of the conveyor. This discontinuity impacts the rate at which flow is able to exit the block over time. The greater this variation in availability, the greater the potential impact on the rest of the model and the greater the block's use can be justified.
One alternative would be to use a combination of Tank and Valve blocks to mimic a Convey Flow block. This is far less computationally intensive than the Convey Flow block by itself. While some configurations may not be as precise, you can use a combination of one Tank fol- lowed by one Valve block in such a way that the behavior is identical or almost identical to the results when using a Convey Flow block.
Another alternative is shown in the Tank and Valve to Convey model. In this example, the bot- tom flow stream behaves almost identically to the upper stream without using a Convey Flow
Discrete Rate

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