Controlled Heat Exchanger Temperature - GSC (English Units)

Summary

The objective of this example is to use the GSC module to vary a Three Way Valve percent open to divert heat exchanger flow to maintain a downstream temperature of 50 deg. C for a specified upstream supply temperature.

Note: This example can only be run if you have a license for the GSC module.

Topics Covered

• Using GSC to control flow splits

Required Knowledge

This example assumes the user has already worked through the Walk-Through Examples section, and has a level of knowledge consistent with the topics covered there. If this is not the case, please review the Walk-Through Examples, beginning with the Beginner: Three Reservoir Model example. You can also watch the AFT Fathom Quick Start Video Tutorial Series on the AFT website, as it covers the majority of the topics discussed in the Three-Reservoir Model example.

In addition the user should have worked through the Beginner: Heat Transfer in a Pipe - GSC example.

Model Files

This example uses the following files, which are installed in the Examples folder as part of the AFT Fathom installation:

• Metric - Controlled HX Temperature.fth

• Metric - Controlled HX Temperature - GSC.fth

• Controlled HX Temperature.dat

Step 1. Start AFT Fathom

From the Start Menu choose the AFT Fathom 12 folder and select AFT Fathom 12.

To ensure that your results are the same as those presented in this documentation, this example should be run using all default AFT Fathom settings, unless you are specifically instructed to do otherwise.

Step 2. Open the Model

Open the Metric - Controlled HX Temperature.fth example file and save it as a new file. The workspace should look like Figure 1 below:

Step 3. Define the Modules Group

Open Analysis Setup, which should bring you to the Modules panel. Check the box next to Activate GSC. The Use option should automatically be selected, making GSC enabled for use.

Step 4. Define the Goal Seek and Control Group

Specify the variables and goals for the model.

Variables Panel

Open the Variables panel in the Goal Seek and Control group. For this example, we will be adding a variable for the Three Way Valve % Open. Click New Variable and enter the following data:

1. Apply = Selected

2. Object Type = Junction

3. Junction Type = Three Way Valve

4. Junction Number and Name = J3 (Three Way Valve)

5. Variable Parameter = Open Percentage

6. Link To = (None)

7. Lower Bound = 0

8. Upper Bound = 100

Goals Panel

Open the Goals panel in the Goal Seek and Control group in Analysis Setup. Click New Goal for the downstream temperature and define it with the data below:

1. Apply = Selected

2. Goal Type = Point

3. Object Type = Branch

4. Goal Parameter = Temperature

5. Criteria = =

6. Goal Value = 50

7. Goal Units = deg. C

8. Object ID = J8 (Branch)

9. Object Location = Outlet

After entering the data, the Goals panel should appear as shown in Figure 3:

Step 5. Define the Cost Settings group

Cost Calculation is not needed for this example. Go to the Cost Settings panel and select Do Not Calculate in the Cost Calculation section.

Step 6. Run the Model

Click Run Model on the toolbar or from the Analysis menu. This will open the Solution Progress window. This window allows you to watch as the AFT Fathom solver converges on the answer. This model runs very quickly. Now view the results by clicking the Output button at the bottom of the Solution Progress window.

Step 7. Examine the Output

The results of the GSC module analysis are shown in the General Output section. The GSC Variables tab shows the final value for the variable parameter, as shown in Figure 4. The open percentage required for the Three Way Valve to achieve a temperature of 50 deg. C at Branch J8 is 79.24%. The GSC Goals tab shows the final value achieved for the goal, as shown in Figure 5. This shows the goal of 50 deg. C was achieved for the downstream temperature.