Air flows around a pipe containing hot steam, as shown: Air 293 K

Transcription

1 Problem description Air flows around a pipe containing hot steam, as shown: x y z Air 293 K Fan: P Q Steel Steam (ASME) 101 KPa 430 K The air inlet boundary condition is given as a function of pressure drop vs flow rate. The steel is modeled as a solid element group within ADINA FD. In this problem solution, we will demonstrate the following topics that have not been presented in previous problems: Defining a material using ASME steam tables Defining a fan boundary condition Using the multigrid solver hecking the mesh for incompatibilities Defining face-links between bodies ontrolling the meshing across thin sections hanging the colors of element groups Obtaining the average temperature over a boundary defined by an element face-set efore you begin Please refer to the Icon Locator Tables chapter of the Primer for the locations of all of the AUI icons. Please refer to the Hints chapter of the Primer for useful hints. Note that you must have an ADINA-M/PS license to do this problem. In addition, you need to be able to allocate at least 220 M to ADINA FD. This problem cannot be solved with the 900 nodes version of the ADINA System because there are too many nodes in the model. ADINA R & D, Inc. 38-1

2 Much of the input for this problem is stored in files prob38_1.in, prob38_2.in and prob38_3.in. ou need to copy file prob38_1.in, prob38_2.in, prob38_3.in from the folder samples\primer into a working directory or folder before beginning this analysis. Invoke the AUI and set the Program Module drop-down list to ADINA FD. hoose Edit Memory Usage and make sure that the ADINA/AUI memory is at least 80 Mytes. Defining model control data, geometry, subdivision data, boundary conditions and materials We have prepared a batch file (prob38_1.in) that performs the following operations: Defines the geometry bodies. Defines analysis control parameters, such as the automatic time-stepping Defines the material properties for the air and steel. Plots the model hoose File Open atch, navigate to the working directory or folder, select the file prob38_1.in and click Open. The graphics window should look something like this: 38-2 ADINA Primer

3 Selecting the multigrid solver hoose ontrol Solution Process, set the Equation Solver to Multigrid and click OK. Defining the material for the steam lick the Manage Materials icon and click the ASME Steam button. In the Define ASME Steam Material dialog box, add material 3, set the Reference Temperature to 400.0, verify that the onstant Pressure is , set the onstant Temperature to 0.0 and click OK. lick lose to close the Manage Materials dialog box. Defining boundary conditions We have prepared a batch file (prob38_2.in) that performs the following operations: Defines a wall boundary condition Defines temperature loads and applies them to the air and steam inlet Defines a normal-traction load and applies it to the steam inlet Replots the model hoose File Open atch, navigate to the working directory or folder, select the file prob38_2.in and click Open. The graphics window should look something like this: PRESRIED TEMPERATURE PRESRIED NORMAL_TRATION 2.500E-06 V V V WAL 1 P ADINA R & D, Inc. 38-3

4 We still need to add the fan boundary condition. lick the Special oundary onditions icon, add condition number 2 and set the Type to Fan. Set 0 to 1.0E-2, 1 to 0, 2 to -1.0E-4, M1 to 1 and M2 to 2 (note, you do not need to change 1 and M1). Set the Type of Fan to Intake and set the Time Function # to 4. Now set the Face # and ody # to 9, 3 in the first row of the table, then click OK. When you click the Redraw icon window should look something like this:, the graphics PRESRIED TEMPERATURE PRESRIED NORMAL_TRATION 2.500E-06 V V V P WAL FAN Defining element groups, subdivision data, meshing We have prepared a batch file (prob38_3.in) that performs the following operations: Defines the element groups Subdivides the geometry Meshes the geometry Regenerates the graphics hoose File Open atch, navigate to the working directory or folder, select the file prob38_3.in and click Open. The graphics window should look something like the top figure on the next page ADINA Primer

5 ADINA R & D, Inc D D D D D D D D D D D DDD V 1 V 2 V 3 P D WAL FAN D 1 2 PRESRIED NORMAL_TRATION 2.500E-06 PRESRIED TEMPERATURE hecking the meshing for incompatibilities: efore we continue, we want to check the meshing for incompatibilities. lick the lear icon, the Mesh Plot icon, the Show Geometry icon (to hide the geometry), the Shading icon and the No Mesh Lines icon. The graphics window should look something like this:

6 Now click the ull Front Faces icon. This icon removes all of the front faces from the plot. The graphics window should look something like this: Incompatibilities here ou are actually looking through the model. There are some interior surfaces in the model. These interior surfaces result from incompatibilities in the model. The incompatibilities are present because we forgot to facelink the bodies of the geometry model (we forgot to do this deliberately so that we can demonstrate how to check the mesh for incompatibilities). Use the Pick icon and the mouse to rotate the graphics out-of-plane, to observe the interior surfaces from different angles. The model is invalid, so we have to delete the mesh and remesh. Deleting the mesh: lick the lear icon and the Mesh Plot icon. lick the Delete Mesh/Elements icon, set the Delete Elements field to On odies, enter 1, 2, 3 in the first three rows of the table, then click OK ADINA Primer

7 reating face-links: hoose Geometry Faces Face Link, add face link 1, set the Type to Links for All Faces/Surfaces and click OK. The AUI displays the warning messages Face 2 of body 1 and face 3 of body 2 cannot be linked. Face 3 of body 1 and face 4 of body 2 cannot be linked. These messages are OK since the indicated faces are not adjacent to each other. lick OK to clear the warning message box. Remeshing: lick the Mesh odies icon, make sure that the Element Group is 3, set the ody # to 1 in the first row of the table and click Apply. Now set the Element Group to 2, set the ody # to 2 in the first row of the table and click Apply. Now set the Element Group to 1, click the Advanced tab, set the oundary Meth. to Delaunay, click the Tetrahedral tab, set the Min. # of Element Layers to 5, set the ody # to 3 in the first row of the table and click OK. lick OK to clear the sliver tetrahedra warning message, if necessary. The graphics window should look something like this: Number of elements across thickness increased using Min. Layer of Elements. Note that we used the Min. Layer of Elements field to increase the number of elements through the thickness of body 3, as indicated in the plot. hecking the meshing for incompatibilities: Let s check the new mesh for incompatibilities. lick the Show Geometry icon (to hide the geometry), the Shading icon, the No Mesh Lines icon and the ull Front Faces icon. The graphics window should look something like the figure on the next page. ADINA R & D, Inc. 38-7

8 Now there are no interior surfaces in the plot. This shows that there are no incompatibilities between the elements. Use the Pick icon and the mouse to rotate the graphics out-of-plane. The Pick icon seems to work in reverse. This is an illusion caused by the fact that you are looking at the back faces on the model. Generating the ADINA FD data file, running ADINA FD, loading the porthole file lick the Save icon and save the database to file prob38. lick the Data File/Solution icon, set the file name to prob38, make sure that the Run Solution button is checked, make sure that the Max Memory for Solution is set to at least 220 M and click Save. ADINA FD runs for 3 solution steps. When ADINA FD is finished, close all open dialog boxes. Set the Program Module drop-down list to Post-Processing (you can discard all changes), click the Open icon and open porthole file prob ADINA Primer

9 Post-processing Plotting the element groups in different colors: lick the olor Element Groups icon. The air is plotted in green, the steel is plotted in red and the steam is plotted in magenta (between red and blue). The red and magenta are hard to tell apart. In the Model Tree, expand the one entry, right-click on 4. EG3, choose olor, select a cyan color from the palette, then click OK. Now the steam is plotted in cyan. The graphics window should look something like this: Plotting the velocities: lick the Shading icon, the No Mesh Lines icon and the Quick Vector Plot icon. Only the velocity vectors on the outside of the model are plotted. lick the ull Front Faces icon. Now you can see the velocity vectors within the model. ut it is difficult to see the vectors because they have the same colors as the element groups. lick the olor Element Groups icon to make all of the element groups the same color, then click the Modify Mesh Plot icon, click the Element Depiction button, and, in the Define Element Depiction dialog box, set the Appearance for Deformed Mesh color to GRA, then click OK twice to close both dialog boxes. The graphics window should look something like the figure on the next page. ADINA R & D, Inc. 38-9

10 VELOIT Use the Pick icon and the mouse to examine the model from different viewpoints. our solution may be slightly different than ours because free meshing produces different meshes on different platforms. Temperatures: lick the lear icon and the Mesh Plot icon. Now click the ut Surface icon, set the Type to utting Plane, set the Defined by field to -Plane and click OK. Now click the Model Outline icon, click the reate and Plot icon, set the and Plot Variable to (Temperature: TEMPERATURE) and click OK. The graphics window should look something like the top figure on the next page. Let s just plot the temperatures in the air. Press the F8 key, uncheck the display of element groups 2 and 3 and click OK. The graphics window should look something like the bottom figure on the next page ADINA Primer

11 TEMPERATURE MAIMUM NODE 685 MINIMUM NODE (284.3) TEMPERATURE MAIMUM NODE 3686 MINIMUM NODE (284.3) ADINA R & D, Inc

12 Only the temperatures on the cutting surface intersection are plotted. lick the ut Surface icon, set the Mesh Display elow the utplane to Display as Usual and click OK. Now the temperatures are plotted on the mesh below the cutting surface intersection. Notice that the plot still shows some unsightly extra lines on the mesh below the cutting surface intersection. To remove these lines, click the Modify Mesh Plot icon, click the Rendering button, set the Element Face Angle to 50 and click OK twice to close both dialog boxes. The graphics window should look something like this: TEMPERATURE MAIMUM NODE 3686 MINIMUM NODE (284.3) Average outlet temperature: lick the lear icon and the Mesh Plot icon. We need to select just the element faces on the outlet. Rotate the model until the outlet is visible, then click the Element Face Set icon, add Element Face Set Number 1, set the Method to Auto-hain Element Faces, double-click in the Face {p} column of the table, then select one or more of the faces on the outlet, then press the Esc key. lick Save to create the face-set. Move the dialog box out of the way of the mesh plot. The element faces on the outlet should be highlighted. lick OK to close the dialog box. To plot the face-set by itself, click the Modify Mesh Plot icon, set the Element Face Set to 1 and click OK. lick the reate and Plot icon, set the and Plot Variable to (Temperature: TEMPERATURE) and click OK. The graphics window should look something like the figure on the next page ADINA Primer

13 TEMPERATURE MAIMUM NODE 5262 MINIMUM NODE 5251 hoose Definitions Model Point (Special) Mesh Integration, add point name OUTLET, set the Integration Type to Averaged and click OK. Now choose List Value List Model Point, set Variable 1 to (Temperature: TEMPERATURE) and click Apply. The temperature at time 3.0 is E+02 (degrees K). (our result may be slightly different because free meshing produces different meshes on different platforms.) Exiting the AUI: hoose File Exit (you can discard all changes). Notes The air velocity in this problem is relatively low. This means that the air particles remain in the heat exchanger for a relatively long time, and also means that the air heats up significantly. The multigrid solver is much more efficient than the sparse solver for this problem. ADINA R & D, Inc

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