Engineering Analysis with Ansys Software Episode 2 Part 7 docx

Ch06-H6875.tex 24/11/2006 17: 48 page 304 304 Chapter 6 Application of ANSYS to thermo mechanics Figure 6.70, click [A] Pick All in order to bring the frame shown in Figure 6.71. As before, activate both [A] All DOF and TEMP and input [B] TEMP value =232 ◦ C. Clicking [C] OK applies temperature constraints on nodes at the bottom of the tank. Now, it is necessary to rotate the WP to the pipe axis. From Utility Menu select WorkPlane →Offset WP by Increments. Figure 6.73 shows the resulting frame. A Figure 6.73 Offset WP by Increments. Ch06-H6875.tex 24/11/2006 17: 48 page 305 6.3 Steady-state thermal analysis of a pipe intersection 305 In degrees box input [A] XY =0 and YZ =−90 as shown. Having WP rotated to the pipe axis, a local cylindrical coordinate system has to be defined at the origin of the WP. From Utility Menu select WorkPlane → Local Coordinate Systems → Create local CS →At WP Origin. The resulting frame is shown in Figure 6.74. A B Figure 6.74 Create Local CS. A B C D Figure 6.75 Select Entities. From the pull down menu select [A] Cylin- drical 1 and click [B] OK button to imple- ment the selection. The analysis involves nodes located on inner surface of the pipe. In order to include this subset of nodes, from Utility Menu select Select → Entities. Figure 6.75 shows the resulting frame. From the first pull down menu select [A] Nodes, from the second pull down menu select [B] By Location. Also, activate [C] Xcoor- dinates button and [D] enter Min,Max =0.4 (inside radius of the pipe). All the four required steps are shown in Figure 6.75. From ANSYS Main Menu select Solution → Define Load → Apply →Thermal →Convection →On nodes. In the resulting frame (shown in Figure 6.67), press [A] Pick All and the next frame, shown in Figure 6.76, appears. Input [A] Film coefficient =−2 and [B] Bulk temperature =38 as shown in Figure 6.76. Pressing [C] OK button implements the selec- tions. The values inputted are taken from Table 6.1. The final action is to select all enti- ties involved with a single command. Therefore, from Utility Menu select Select → Everything. For the loads to be applied to tank and pipe surfaces in the form of arrows from Utility Menu Ch06-H6875.tex 24/11/2006 17: 48 page 306 306 Chapter 6 Application of ANSYS to thermo mechanics A B C Figure 6.76 Apply CONV on Nodes. select PlotCtrls →Symbols. The frame in Figure 6.77 shows the required selection: [A] Arrows. From Utility Menu selecting Plot →Nodes results in Figure 6.78 where surface loads at nodes as shown as arrows. From Utility Menu select WorkPlane → Change Active CS to → Specified Coord Sys in order to activate previously defined coordinate system. The frame shown in Figure 6.79 appears. Input [A] KCN (coordinate system number) =0 to return to Cartesian system. Additionally from ANSYS Main Menu select Solution → Analysis Type → Sol’n Controls. As a result, the frame shown in Figure 6.80 appears. Input the following [A] Automation time stepping =On and [B] Number of substeps =50 as shown in Figure 6.80. Finally, from ANSYS Main Menu select Solve → Current LS and in the appearing dialog box click OK button to start the solution process. 6.3.5 Postprocessing stage When the solution is done, the next stage is to display results in a form required to answer questions posed by the formulation of the problem. Ch06-H6875.tex 24/11/2006 17: 48 page 307 6.3 Steady-state thermal analysis of a pipe intersection 307 A Figure 6.77 Symbols. Ch06-H6875.tex 24/11/2006 17: 48 page 308 308 Chapter 6 Application of ANSYS to thermo mechanics Figure 6.78 Convection surface loads displayed as arrows. A Figure 6.79 Change Active CS to Specified CS. From Utility Menu select PlotCtrls →Style →Edge Options. Figure 6.81 shows the resulting frame. Select [A] All/Edge only and [B] press OK button to implement the selection which will result in the display of the “edge” of the object only. Next, graphic controls ought to be returned to default setting. This is done by selecting from Utility Menu PlotCtrls → Symbols. The resulting frame, as shown in Figure 6.82, contains all default settings. Ch06-H6875.tex 24/11/2006 17: 48 page 309 6.3 Steady-state thermal analysis of a pipe intersection 309 A B Figure 6.80 Solution Controls. A B Figure 6.81 Edge Options. The first plot is to show temperature distribution as continuous contours. From ANSYS Main Menu select General Postproc → Plot Results → Contour Plot → Nodal Solu. The resulting frame is shown in Figure 6.83. Select [A] Temperature and press [B] OK button as shown in Figure 6.83. The resulting temperature map is shown in Figure 6.84. Ch06-H6875.tex 24/11/2006 17: 48 page 310 310 Chapter 6 Application of ANSYS to thermo mechanics Figure 6.82 Symbols. Ch06-H6875.tex 24/11/2006 17: 48 page 311 6.3 Steady-state thermal analysis of a pipe intersection 311 A B Figure 6.83 Contour Nodal Solution Data. Figure 6.84 Temperature map on inner surfaces of the tank and the pipe. Ch06-H6875.tex 24/11/2006 17: 48 page 312 312 Chapter 6 Application of ANSYS to thermo mechanics The next display of results concerns thermal flux at the intersection between the tank and the pipe. From ANSYS Main Menu select General Postproc → Plot Results →Vector Plot →Predefined. The resulting frame is shown in Figure 6.85. A B C Figure 6.85 Vector Plot Selection. In Figure 6.85, select [A] Thermal flux TF and [B] Raster Mode. Pressing [C] OK button implements selections and produces thermal flux as vectors. This is shown in Figure 6.86. 6.4 Heat dissipation through ribbed surface 6.4.1 Problem description Ribbed or developed surfaces, also called fins, are frequently used to dissipate heat. There are many examples of their use in practical engineering applications such as computers, electronic systems, radiators, just to mention a few of them. Figure 6.87shows a typical configuration and geometry of a fin made of aluminum with thermal conductivity coefficient k =170 W/m K. Ch06-H6875.tex 24/11/2006 17: 48 page 313 6.4 Heat dissipation through ribbed surface 313 Figure 6.86 Distribution of thermal flux vectors at the intersection between the tank and the pipe. 330 20 20 20 10 100 85 85 40 25 50 Figure 6.87 Cross-section of the fin. The bottom surface of the fin is exposed to a constant heat flux of q =1000W/m. Air flows over the developed surface keeping the surrounding temperature at 293 K. Heat transfer coefficient between the fin and the surrounding atmosphere is h =40W/m 2 K. Determine the temperature distribution within the developed surface. 6.4.2 Construction of the model From ANSYS Main Menu select Preferences to call up a frame shown in Figure 6.88. [...]... coordinates X2 = −55; [C] Y1 = 25 ; [D] Y2 = 100 to create area A2 Next input: [A] X1 = −45; [B] X2 = −35; [C] Y1 = 25 ; [D] Y2 = 100 to create area A3 Appropriate inputs should be made to create areas, to be cut out later, on the right-hand side of the fin Thus inputs: [A] X1 = 85; [B] X2 = 75 ; [C] Y1 = 25 ; [D] Y2 = 100 create area A4 Inputs: [A] X1 = 65; [B] X2 = 55; [C] Y1 = 25 ; [D] Y2 = 100 create area A5... construction of the model make the following inputs to the frame shown in Figure 6. 97 to create area A1: [A] X1 = 25 ; [B] X2 = −15; [C] Y1 = 50; [D] Y2 = 100 Inputs: [A] X1 = −5; [B] X2 = 5; [C] Y1 = 50; [D] Y2 = 100 create area A2 Finally input [A] X1 = 15; [B] X2 = 25 ; [C] Y1 = 50; [D] Y2 = 100 to create area A3 Again from ANSYS Main Menu select Preprocessor → Modelling → Operate → Booleans → Subtract... 6. 87 318 Chapter 6 Application of ANSYS to thermo mechanics A Figure 6.96 Subtract Areas From ANSYS Main Menu select Preprocessor → Modelling → Create → Areas → Rectangle → By Dimensions Figure 6. 97 shows the frame in which appropriate input should be made In order to create area A1 input: [A] X1 = −145; [B] X2 = − 125 ; [C] Y1 = 40; [D] Y2 = 85 In order to create area A2 input: [A] X1 = 125 ; [B] X2... areas A1, A2, A3, and A5 and click [A] OK button Area A6 with appropriate cut-outs is created It is shown in Figure 6.98 In order to finish construction of the fin’s model use the frame shown in Figure 6. 97 and make the following inputs: [A] X1 = −85; [B] X2 = 75 ; [C] Y1 = 25 ; [D] Y2 = 100 Area A1 is created Next input: [A] X1 = −65; [B] A C Figure 6. 97 B D Create rectangle by four coordinates X2 = −55;... were subtracted [A] X1 = 45; [B] X2 = 35; [C] Y1 = 25 ; [D] Y2 = 100 create area A7 Next, from ANSYS Main Menu select Preprocessor → Modelling → Operate → Booleans → Subtract → Areas The frame shown in Figure 6.96 appears Select first area A6 and click [A] OK button Then, select areas A1, A2, A3, A4, A5, and A7 Clicking [A] OK button implements the command and a new area A8 with appropriate cut-outs is created... − 125 ; [C] Y1 = 40; [D] Y2 = 85 In order to create area A2 input: [A] X1 = 125 ; [B] X2 = 145; [C] Y1 = 40; [D] Y2 = 85 In order to create area A3 input: [A] X1 = −105; [B] X2 = −95; [C] Y1 = 25 ; [D] Y2 = 100 In order to create area A5 input: [A] X1 = 95; [B] X2 = 105; [C] Y1 = 25 ; [D] Y2 = 100 From ANSYS Main Menu select Preprocessor → Modelling → Operate → Booleans → Subtract → Areas The frame shown in... Figure 6.95 B D Rectangle with specified dimensions Figure 6.95 shows inputs to create rectangle (A2) at the left-hand upper corner of the main rectangle (A1) They are: [A] X1 = −165; [B] X2 = −105; [C] Y1 = 85; [D] Y2 = 100 In order to create right-hand upper corner rectangles (A3) repeat the above procedure and input: [A] X1 = 105; [B] X2 = 165; [C] Y1 = 85; [D] Y2 = 100 Now, areas A2 and A3 have to be... From ANSYS Main Menu select Solution → Define Loads → Apply → Thermal → Convection → On Areas Figure 6.106 shows the resulting frame  322 Chapter 6 Application of ANSYS to thermo mechanics A Figure 6.103 Volume attributes with specified material and element type A Figure 6.104 Mesh Volumes 6.4 Heat dissipation through ribbed surface Figure 6.105 View of the fin with mesh network A Figure 6.106 323 Apply... be checked off From ANSYS Main Menu select Preprocessor → Meshing → Mesh Attributes → Picked Volumes The frame shown in Figure 6.1 02 is created 6.4 Heat dissipation through ribbed surface 321 A Figure 6.1 02 Volume Attributes Select [A] Pick All and the next frame, shown in Figure 6.103, appears Material Number 1 and element type SOLID 87 are as specified at the beginning of the analysis and in order... shows the resulting frame Input [A] X1 = −165; [B] X2 = 165; [C] Y1 = 0; [D] Y2 = 100 to create rectangular area (A1) within which the fin will be comprised Next create two rectangles 6.4 Heat dissipation through ribbed surface 3 17 A C Figure 6.94 B D Create Rectangle by Dimensions at left and right upper corner to be cut off from the main rectangle From ANSYS Main Menu select Preprocessor → Modelling → . problem. Ch06-H6 875 .tex 24 /11 /20 06 17: 48 page 3 07 6.3 Steady-state thermal analysis of a pipe intersection 3 07 A Figure 6 .77 Symbols. Ch06-H6 875 .tex 24 /11 /20 06 17: 48 page 308 308 Chapter 6 Application of ANSYS. 6.84. Ch06-H6 875 .tex 24 /11 /20 06 17: 48 page 310 310 Chapter 6 Application of ANSYS to thermo mechanics Figure 6. 82 Symbols. Ch06-H6 875 .tex 24 /11 /20 06 17: 48 page 311 6.3 Steady-state thermal analysis. inputs: [A] X1 =85; [B] X2 =75 ; [C] Y1 =25 ; [D] Y2 =100 create area A4. Inputs: [A] X1 =65; [B] X2 =55; [C] Y1 =25 ; [D] Y2 =100 create area A5. Inputs Ch06-H6 875 .tex 24 /11 /20 06 17: 48 page 319 6.4