Page 367 - ExtendSim User Guide
P. 367

Tutorial for Discrete Rate Systems 341
A basic discrete rate model
The model should now look like the following:
Cooling phase represented by Convey Flow block
When you run this model, notice that there is no product flowing into the Yogurt tank for the first 20 minutes. This happens because it takes that long for the first containers to leave the refrigeration unit represented by the Convey Flow block. This causes starving in the down- stream portion of the model that follows the Convey Flow block. Because it takes longer to get the finished product, fewer containers get produced than in the previous model.
☞ Although it doesn’t happen in this model, if the Convey Flow block were full, it could slow down the upstream processes that feed into it. This is known as blocking.
☞ While the use of the Convey Flow block is appropriate for this model, be careful about placing too many Convey Flow blocks in a model as they are computationally intensive. The Convey Flow block should only be used if the system requires precise tracking of flow movement. A Valve and a Tank can often be used instead, with less impact on simulation speed. For more information, see “When to avoid using the Convey Flow block” on page 417.
Package the containers
The next step of the process involves packaging the yogurt containers into cartons. This is rep- resented using another Change Units block.
Delete the flow connection between the Cooling Cycle and the Yogurt tank. Add a second Change Units block to the model;
Connect it between the block labeled Cooling Cycle and the block labeled Yogurt.
In the block’s dia- log, do not change the first setting (Change units from: contain- ers).
Dialog of second Change Units block
Discrete Rate

   365   366   367   368   369