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Three dimensional modeling system of heat exchange equipment parts based on AutoCAD platform (II)

4 three dimensional modeling example

tubesheet is one of the important parts of heat exchange equipment. Therefore, it is often necessary to conduct finite element analysis of temperature field and stress field for tubesheet. Therefore, it is necessary to establish a three-dimensional model of tubesheet, and continuously optimize and modify the model of tubesheet according to the analysis results. If you use manual modeling, it will inevitably increase the boring workload of design analysts and greatly reduce the work efficiency. With parametric program modeling, users can establish, optimize and modify the model in a very short time

the tubesheet is a circular flat plate with many pipe holes opened according to the pipe layout method. The three-dimensional modeling of the tubesheet is to directly generate the three-dimensional solid of the tubesheet by inputting the nominal diameter DN of the cylinder, the outer diameter DH of the heat exchange pipe, the thickness h of the tubesheet and the pipe layout method through three-dimensional parametric drawing. The following describes the development process of the three-dimensional modeling program of the tube sheet, taking the tube sheet with the extension of the single shell pass and the single tube pass as an example

4 1 generation of 2D object of tubesheet

tubesheet is a revolving body in structure, so only half of the section of tubesheet needs to be generated, as shown in Figure 4. Establish a coordinate system, give the coordinates of each point in the diagram, use the function acdbpolyline() to generate a closed two-dimensional polyline, and generate a two-dimensional graphic field, call the function revolve() to rotate the two-dimensional graphic field around the Y axis to generate a three-dimensional model of the flat plate (no hole is dug)

4 2 algorithm of tube layout program with non greasy feel for tube sheet

take the single pass tube layout with square arrangement of tubes as an example, and establish the calculation model, as shown in Figure 5

the program uses an iterative method to determine the center position of the heat exchange tube. The iterative process is as follows

high molecular composite materials have outstanding advantages such as light weight, corrosion resistance, easy processing, adjustable conductivity, etc. 421 when determining the iterative initial value

central pipe laying odd number arrangement, the iterative formula is:

x=x0, x=x+p

y=y0, y=y+p

central pipe laying even number arrangement, the iterative formula is:

x=x0+p/2, x=x+p

y=y0+p/2, y=y+p

where x0 and Y0 are iterative initial values, Values shall be taken according to the pipeline conditions; P is the center distance of heat exchange tube. After iteration, the center coordinates (x, y) of each heat exchange tube hole can be calculated

422 determine the center position of each heat exchange tube

determine the initial values of x0 and Y0 according to the tube pass conditions, determine the iteration formula and carry out the iteration cycle according to the odd or even arrangement of central tube layout. During the iteration cycle of each layer, the counter starts to accumulate the total number of heat exchange tubes sum=sum+1; Until y=y+p, carry out the next iteration. This cycle continues until. At the end of the iteration cycle, the counter accumulates the number of all heat exchange tubes sum. Where, DL is the diameter of the limited circle for tube sheet layout, and its calculation formula is referred to [5]

after determining the center position of the heat exchange tube, call the function createfrustum() to generate a cylinder with the center of the heat exchange tube as the center and the thickness of the tubesheet as the height. The Boolean difference operation is used to dig out each cylinder in the tubesheet entity. The program flow framework is shown in Figure 6

4 3 generate bolt holes and pull rod holes

according to the above methods, determine the center position of flange bolt holes in the extension part, generate cylinders, and generate bolt holes by Boolean difference operation. Follow the same procedure to generate the pull rod hole

so far, the three-dimensional modeling of tube sheet has been completed. The above method can be used to complete the three-dimensional solid modeling system of other parts of thermal equipment that is changing in the global market pattern of China's plastic machinery industry

5 system running

run the program under the environment of vc++60 to get a tube sheet design ARX dynamic connection library program. Start AutoCAD2000, click the extension part in the drop-down menu of the three-dimensional modeling system of heat exchange equipment components as the flange menu item, AutoCAD will automatically load the ARX file, and add the command tubesheet of the tube sheet three-dimensional modeling ARX program to the AutoCAD internal command stack. Execute this command to eject the pipe

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