FLOTHERM V3.1 Introductory Course TUTORIAL - COMMAND CENTER Introduction This tutorial covers the basic operation of the Command Center Application Window (CC) by walking the user through the main steps required to: Starting the Command Center Building parametric scenario projects Processing the scenario projects and monitoring the solutions Analysing the results Managing your global processing resources Our tutorial model is a 19 -rack. CPU + Heatsink Rack1 Rack2 Thermal design work Where is the best position for the CPU-board in the upper rack? How big is the influence of a smaller hole diameter on the CPU temperature and fan performance? Command Center issues Basic operation and post processing Simple parametric variations
Part A) Simple parametric variations Start FLOTHERM. Load the Flomerics project OptionalTutorial4 from the FLOTHERM Project Manager Application Window. Click on the CC icon in the FLOTHERM lefthand side button bar to launch the Application Window. NOTE: By default, the CC automatically goes to the Input Variables panel. All variables are displayed in a tree diagram, similar to the project manager in FLOTHERM. Notice that each type of input item has a distinctive symbol. Your Command Center Window should appear as follows. NOTE: You may resize the Command Center window to your needs.
Selection of the Input Variables In the Input Variables panel, find the Root Assembly called Rack in the tree diagram. (Use the vertical scroll bar or resize the window.) Double-click on the name or click on its + sign to expand the first level of the Project Hierarchy. Find the 19 inch Subracks assembly and expand the branch. After this do the same for the Rack1 assembly. Expand the CPU Board assembly. Double-click on the symbol for Absolute Location directly below the symbol for the CPU Board assembly. NOTE: The symbol changes to when the input variable is selected. The character string Z location is highlighted in blue: Double-click on Z-location to activate the Zlocation input variable. In the right corner of the panel, the actual value of the CPU-board s z-location appears: The value for the Z-location of the CPU-Board is shown in absolute coordinates. NOTE: An alternative way of selecting variables is to click the input variable check box in the panel.
We aim to find the best position of the CPU Board -assembly. To achieve this, we will shift CPU board to the left and to the right and determine the temperatures. The step-size in z- direction will be 100 mm. The test-positions of the CPU-board are denoted in the picture below as red dashed lines. In the right panel check the Linear check box. Enter these values in the respective text fields below and Press the Apply Variation button. Step Size: 100 Number of positive Steps: 2 Number of negative Steps: 1 NOTE: You can manually edit each value by double clicking on the value, or you can manually cut and paste values. When Apply is pressed a linear variation of the selected base project value will be created. Selection of the Output Variables This is the second stage: Selection of the output variables chosen to monitor for comparison of different scenarios. Go to the Output Variables tab. NOTE: The Output Variables panel is quite similar to the Input Variables one: all the output variables are displayed under a tree diagram with a distinctive symbol. Any variable calculated in Flotherm can be selected, for example: There are several types of output variables: - thermal properties -flow properties -variables on monitor points etc
Find the Rack Assembly in the tree diagram and expand it. Then Expand the 19 inch subrack assembly followed by Rack1 assembly and then CPU board assembly. Expand the Board smart part and the CPU object branch. Select the output variable Mean solid temperature. Find the Fan tray assembly branch under Rack assembly and expand it as shown to the right. Double click on Static Pressure The selected output variable allow us to monitor temperature of the CPU. It s over! This stage is fast, but crucial for results. Display the Scenario Projects and Solve This third stage is very important: we have created variations for some selected input variables, and now we are going to see how all these variations will be solved as scenarios. Click on the Scenario Table tab at the lower side of the window. There are three areas in the scenario panel: Blue: The selected input variables and their variations. Click and selecting or double clicking on a certain blue field will change the value of the input variable individually. Click and selecting the left column field will deselect an input variable. White: Control parameter settings. Some fields are editable. Pink: These output variables are the computational results displayed when the scenario projects are processed. No fields are editable. NOTE: Base projects input variables are not editable. The window displays the base and scenario projects. Each scenario project is numbered automatically in the top line of the window. NOTE: Instead of a number, a scenario can be named. This is achieved by double-clicking on the top line and editing the field.
Click in the white area (arrow) in the left column in the Store s? field. The line is highlighted black. Select (right click) and choose None from the drop down menu. NOTE: History Only in the selected setting to the right (Store s?) requires the smallest amount of disk space. It will store the profile plot data and the monitor point values only. Should you need to store the complete solution (i.e. the results for each grid cell of each scenario) Full can be toggled. This option requires a large amount of disk space. Click in the white area in the left column in the Initialize from field and select. Select All from Base Project from the drop down menu. Before solving we must check the Solver configuration. Go to the menu Edit/Solver Configuration in the top menu bar. Enter 1 in the Run... Solvers at a time field. Depending on the number of solver licenses available and on the performance of the computer more than 1 solvers can be run simultaneously. If a FLOVOLUNTEER is active, the check box Remote machine could be checked. In this case all but the base project could be solved on another computer in the local area network. Most scenarios differ from the Base project or the previous Scenario by a small deviation. In these cases it is advisable to initialize from the Base project or the previous Scenario. This saves calculation time since the existing solution does not differ substantially from the new solution and convergence can be achieved faster. Sometimes the option All from Previous is advisable, (i.e. if a parametric variation does not affect the geometry, like a linear variation of a power value, conductivity or emissivity). By shifting the board 100 mm a significant change in the system geometry has been made. In this case All from Base Project is a more reasonable approach.
Solving and Solution Monitoring Click Scenario on the top bar of the CC window. Select Solve All in the drop down menu. The CC is automatically processing the base project and scenario projects. NOTE: The shortcut icon is. When a solution is ongoing the Stop icon is seen. If the Base project is not solved yet, the solution sequence always starts solving the Base project in FLOTHERM. This can be monitored in the standard Profiles AW. After the Base project is solved the Scenarios are solved subsequently. During the processing, the status of each solution is displayed into the Control Parameters Area. This is a summary of all the status message you can read : Unsolved The CC has not begun the processing of the scenario projects queue Solving(MachineName) The scenario project is been processing on the machine indicated Queuing(ProcessingOrder) The scenario project is queuing Pending Initialization The processing is pending until the initialization solution is available Interrupted The processing of the scenario project has been interrupted by the user Solved-Unconverged The outer iteration number has been reached without convergence of the solution Solved-Converged The solution has converged During the processing, click on the Solution Monitoring tab at the lower side of the window. Highlight one after the other the scenario project rows at the left side of the window. You will see more or less the following window: When the CC is processing the scenario projects, the convergence of each one may be monitored in real time!
When the CC has processed a scenario project, go back into the Scenario Table panel to see the results attached with the selected output variable. Now, you just have to wait for the end of the processing; it can take several minutes, so may be it s time to have a cup of coffee! Analyzing the s The results calculated for the output variables may be quickly displayed and compared in charts. You can also export any selected scenario project into the main projects directory to further post process the solution. At the end of the solution process determine the scenario with the lowest temperatures for the CPU. You can save this scenario by clicking on the appropriate Scenario number in the top line. When the column is highlighted black select and choose Save As from the drop down menu. Accept the default name or enter a name of your choice. Press Ok. /Comments
To create a diagram of the results go to the chart menu. Then Create. /Comments The comparison chart window appears. This is the integrated post processing utility to create plots of the results obtained in the Command Center. Leave the first tab Chart type at default XY line. Go to tab Data Source. In the selection-field X-Axis Variable select the value CPU Board: z-location. Select CPU: Mean Solid Temperature in the field Y-Axis Variables and press the button to load the values in the chart. Enter a title in the Title -field, e.g. T vs. Z- position of CPU Board. Hit the Enter key. This is the temperature on the CPU as a function of the board s position in the rack. Obviously the lowest temperature is obtained by placing the board at Z=94 mm, which is the right slot. This may be due to the thermal properties of the lower rack. NOTE: After creating the chart you can print the chart or export the scenario window as csv-file. This can be done using the menu item Scenario/Export Scenario Table in the top menu bar. Analysis of smaller inlet and outlet holes and fan performance The results calculated for the output variables may be quickly displayed and compared in charts. Next we define a parametric variation of the inlet and outlet openings open area ratio.
EMC issues are always in favor of smaller inlet and outlet holes. In contrast to this thermal design is always in favor of wider openings. So far we determined an optimum for the CPU-boards position in the upper rack. We can go on from this point and do further optimization on the previously saved project with optimized CPU-position. Go to the Project Manager. Load the CCTutorial_A. If the Changes made to project-save? dialogue appears, press Yes. Open the Command Center. Go to the Input Variables tab. Find the Resistance Properties icon and expand it. Double click on the resistance attribute Grid: 70% open Saving the project will store all Command Center settings. Go to the right panel. In the field Library Selection expand the Flomerics Resistance Library. Double click in the following order on these resistance attributes: 60 % 50 % 40 % 30 % Not only parameters can be selected as Input Variable but also Object Variables (Fan, Heat sink, PCB) and Object Attributes (Resistance Attribute, Ambient etc).
We defined a new variation. Attached to inlet and outlet opening in the rack is the resistance attribute Grid: 70% open. This attribute will be changed to 60%, 50%... in the Scenarios. Output variables for fan performance Go to the Output Variables tab. Repeat the steps outlined in the previous section to define the same set of output variables. /Comments Click on the Save icon bar. in the top menu
Solving the Scenarios and post processing Click in the Initialize from field and select. Choose All from Previous from the Drop Down menu. Go to the Scenario Table and select the menu Scenario/Solve All When all Scenarios are solved, create a new chart. Every scenario will be initialized from the previous one. The Base Project is not solved, so the solution sequence starts with solving the Base project in FLOTHERM. This chart shows the CPU temperature s dependency of the mass flow rate through the rack: Define a new plot: x-axis variable: Fan Mass Flow y-axis variable: CPU temperature Title: T vs. Mass Flow. Hit the Enter key. Define another plot: Title: Mass Flow vs. Static pressure. Hit Enter. x-axis: Fan: Static Pressure y-axis: Fan: Mass Flow This chart represents the fan curve: NOTE: You can save / print your plots and export the scenario table as csv-file. Close the Command Center and FLOTHERM Given a temperature limit of 75 C it would be reasonable to suggest a grid of open area ratio of 0.5.