JPH1011472A - High-temperature durability evaluating method and storage medium storing its evaluation model generating program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To generate an element file as a model for a simulation program in a relatively short time with relatively small man-days. SOLUTION: Main surface files having main surfaces constituting a model for object equipment of high-temperature durability evaluation such as a heat exchanger are prepared as many as models. According to inputted kind data on a model to be evaluated and size data specifying the size of the equipment to be evaluated, a model correspondence main surface file is generated which has at least coordinate data on four nodes sectioning respective main surfaces and plate thickness data as attribute data by the main surfaces. The respective main surfaces are divided into mesh-shaped elements to generate an element data file having element data having point data in the respective elements as attribute data. Then temperature data obtained by detecting the heating state of the actual equipment are added as attribute data to the respective element data and stress data by the elements are found by a thermal stress analyzing program.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a heat equipment such as a heat exchanger which is operated repeatedly between high temperature and room temperature.
The present invention relates to a high-temperature durability evaluation method and a storage medium storing the evaluation model creation program.

[0002]

2. Description of the Related Art In a variety of equipment, such as a heat exchanger of a water heater, in which a state of being heated to a high temperature and a state of being stopped at a room temperature are repeated, parts constituting the equipment by the high temperature heating have material characteristics. The expansion and contraction are repeated according to the above, and strain and stress are generated between the parts. Therefore, in the design stage of the heat exchanger,
It is necessary to predict the stress characteristics by simulation or the like and analyze the life due to the fatigue fracture.

[0003]

However, in order to perform this simulation, it is necessary to create a simulation model applicable to the simulation program for the heat exchanger, and the simulation model applicable to the existing simulation program is required. Generally, it takes a lot of time and man-hours to create a model.

An object of the present invention is to provide a high-temperature durability evaluation method and a storage medium storing an evaluation model creation program, which can create such a model in a relatively short time and man-hour.

A further object of the present invention is to provide a high-temperature durability evaluation method capable of creating an element file serving as a model of a simulation program by the finite element method in a relatively short time and man-hour, and a storage storing an evaluation model creation program. To provide a medium.

[0006]

According to the present invention, there is provided, according to the present invention, a main surface file having a plurality of main surfaces constituting a model of a target device to be subjected to a high-temperature durability evaluation is prepared for a plurality of models. And the type data of the model to be evaluated and the dimensional data for specifying the size of the device to be evaluated based on the main surface file,
A step of creating a model-compatible principal plane file having coordinate data of at least four nodes defining each principal plane and sheet thickness data as attribute data for each principal plane, and principal planes constituting the model-corresponding principal plane file According to the element division data of the element size or the number of divisions given to each element, each main surface is divided into a plurality of mesh-like elements, and an element data file having element data having point data in each element as attribute data is obtained. Creating, and adding, as attribute data, temperature data detected in a heating state of the actual device to each element data according to the element data file, and obtaining stress data of each element by a thermal stress analysis program. This is achieved by providing a method for evaluating high-temperature durability.

Further, according to the present invention, there is provided an evaluation model creation program for a target device to be subjected to a high-temperature durability evaluation, wherein only a plurality of models are prepared for the target device to be subjected to a high-temperature durability evaluation. Based on a principal plane file having a plurality of principal planes constituting the model, at least respective principal planes are defined in accordance with input type data of the model to be evaluated and dimensional data for specifying the size of the device to be evaluated. A program code for creating a model-compatible main surface file having coordinate data of four nodes and thickness data as attribute data for each main surface, and an element size given to the main surface constituting the model-compatible main surface file Or, according to the element division data of the division number, each main surface is divided into a plurality of mesh-like elements, and the point data in each element is It is achieved by providing a storage medium readable to a computer evaluation model creation program is stored with a program code for creating an element data file with element data with the sex data.

[0008] A plurality of main surface files having a plurality of main surfaces constituting a model of a target device to be subjected to high-temperature durability evaluation are prepared for a plurality of models, and type data and dimensional data of the model to be evaluated are provided. By defining the principal planes that make up the model to be evaluated with, and inputting the data necessary to decompose the principal planes into elements, tens of thousands of element data files can be generated in a short time .

[0009]

Embodiments of the present invention will be described below with reference to the drawings. However, the technical scope of the present invention is not limited to the embodiment.

FIG. 1 is a flow chart of the entire process of the method for evaluating high-temperature durability according to the present invention. Various simulation programs for heat conduction analysis or thermal stress analysis by the finite element method are commercially available. For example, H. K. S. ABAQUS sold by the company. In such a finite element method program, the model to be analyzed needs to be decomposed into tens of thousands of elements and given to the program. For this purpose, in the embodiment of the present invention, a step of creating a model decomposed into tens of thousands of elements (S1 to S5) and a step of giving temperature data during heating to the model (S6).
And a step of performing a thermal stress analysis (S7, 8).

As a method of disassembling the heat exchanger into tens of thousands of elements, specifically, it is most common to disassemble the parts of the heat exchanger into meshes and use each mesh as an element. However, the finite element method program A
In BAQUS, etc., in order to disassemble the heat exchanger into tens of thousands of mesh-shaped elements and input each as element data, it is generally necessary to manually give commands for each element and use it practically. Not a target.

Therefore, in the present invention, a main surface file in which a heat exchanger model is developed on a plurality of main surfaces is prepared in advance (S1), and the type of heat exchanger to be analyzed and predetermined dimensions are given. This makes it possible to easily create a main surface file of the heat exchanger to be analyzed (S2, S3). Then, by giving necessary information for decomposing into a mesh to each main surface of the main surface file, a data file of elements decomposed into a mesh is created (S5). By doing so, a data file in which the heat exchanger model required for the finite element method is developed into elements can be generated relatively easily and in a short time.

Thereafter, the temperature data detected by the thermo-viewer or the like is provided to the element data file as attribute data of each element (S6). At this time, for the temperature that cannot be detected by the internal thermo-viewer such as the radiation fin, the measured temperature at the main point should be given, and the temperature data of all elements should be obtained by calculation according to the heat conduction characteristics and its finite element method program. Can be. Further, the stress-strain characteristics obtained by measuring each component and using the temperature as a variable, and the strain values of all the elements are calculated by calculation according to the finite element method program (S7). Since this strain corresponds to stress one-to-one, the stress of each element is calculated in the same way, the amplitude of the stress at the time of heating and the stress at the time of rest, and the maximum stress amplitude is extracted to determine the life. Yes (S8).

The above is a schematic process step of the present invention. The details will be described below with reference to the drawings.

FIG. 2 is a perspective view of a general heat exchanger 10 used for a water heater or the like. The heat exchanger 10 includes a fin 12, an inner trunk 14, a skirt 16, and a water tube 20. The inner trunk 14 and the fin 12 are connected by a slope 18. Such a heat exchanger 10
Means that the main configuration above is the same for all models,
What differs is the size of each and the number of turns of the water tube. Therefore, in the present invention, by preparing files developed on the main surface for the heat exchanger 10 in advance for the number of windings of the water pipe, if the dimensions and the number of windings of the water pipe are given as input data, the heat of the object is obtained. The main plane file of the exchanger model can be created.

FIG. 2 is a perspective view of a heat exchanger model in which the number of windings is two as an example. In this case, for example, the heat exchanger model is disassembled into main surfaces M1 to M27 shown in FIG. Is prepared in advance. FIG. 3 shows a part of the development view. Only the main surface of the portion viewed from the front in FIG. 2 is shown. The fin portion 12 is developed on an upper surface M1 and an outer surface M2, the inner body portion 14 is formed of three surfaces M10, M14, and M18 whose side surfaces are divided by a water pipe 20, and the skirt portion 16 is a surface M22. .

For example, when the number of turns of the water pipe 20 becomes three,
The divided surface becomes four. Therefore, in that case,
You will use a different kind of principal plane file. still,
Although described as the upper surface M1, in a specific heat exchanger, the upper surface M
The portion corresponding to 1 is developed into a plurality of fins and a water pipe penetrating the fins.

Now, the developed main surface of the heat exchanger requires a combination of only the types of windings having different numbers of turns, but the size of the decomposed main surface differs depending on the dimensions of the heat exchanger. Come. Therefore, as shown in step S2 of FIG. 1, the height of the target heat exchanger model and the inner trunk 1
4, the length L, the width W, the height H, the plate thickness, the length L, the width W, the height H, the plate thickness, the length L of the skirt portion 16,
Width W, height H, plate thickness, number of fins and plate thickness, water pipe position,
Although not shown, data necessary for defining the size of the developed view of the main surface prepared in advance, such as the entry position of the water pipe into the fin, the number and thickness of the fins, the connection part of the fin and the water pipe, etc. give. Further, the number of turns of the water pipe is given as model type data.

As a result, a principal plane file corresponding to the type of the model is selected according to the kind data, and a principal plane file having three-dimensional coordinate data and thickness data of four nodes of the principal plane as attribute data according to given dimensions. Is generated.

FIG. 4 is a structural diagram showing a data structure of the main surface file. The main surfaces M1 to M28 and the like are classified into portions to which they belong, and each of the main surfaces M1 to M28 and the like has four-node three-dimensional coordinate data and thickness data as attribute data thereof. The number of the main surfaces is, for example, about 250, and is a number determined according to the details of the model of the heat exchanger. Further, if necessary, the inner radius of the inner fin, the outer fin, the corner of the skirt portion, the radius of the corner of the water pipe, the width of the joint of the water pipe to the inner fuselage, etc. are also input data for defining the main surface. Can also be given. The input data to be given differs depending on how detailed the main surface is. At this stage, the three-dimensional shape of the heat exchanger model of interest is defined.

After the principal planes of the target heat exchanger model are specified as described above, each principal plane is divided into meshes. This mesh will be treated as an element in the finite element method. As a method of dividing the main surface into a mesh, in the present invention, the number of divisions or the element size (mesh size) is given to each main surface by the operator.

FIG. 5 is a diagram showing, as an example, the relationship between the main surface Mk and the mesh (element) of the main surface when the main surface Mk is divided into a plurality of meshes. The principal surface Mk has its four nodes (k1, k
2, k3, k4) and the plate thickness d. When the main surface Mk is a simple rectangle, it is simply divided into elements E1 to En as shown in the upper part of FIG. And each element E is
As shown in the lower part of FIG. 5, for example, it is specified by four nodes and the plate thickness d.

As a method of decomposing the main surface Mk into meshes (elements), by giving the size of the element, four nodes and the thickness d of the element divided by calculation are obtained. If the size of each main surface is different, giving the size of the element to be divided can make the size of the whole element the same, which may be more preferable for the finite element method program .

In a commercially available finite element method program, given four nodes and sheet thickness, conversion to integration points inside each element is performed based on the four nodes and sheet thickness. That is, as shown in the lower part of FIG. 5, the coordinates of the integration point as indicated by the internal X mark are converted as the attribute data. Or 4
The coordinates of 20 integration points in addition to the nodes and the plate thickness may be provided as attribute data. By using such integration points as attribute data, it is possible to easily paste temperature data of 20 points in the element later.

Alternatively, as shown in the lower part of FIG. 5, instead of the four nodes and the plate thickness, the coordinates of the integral points as shown by the internal X marks are used as attribute data for the divided elements.
It may be given to the finite element method program.

FIG. 6 is a structural diagram showing an example of an element data file in a case where the attribute data of each of the elements E1 to Em has four nodes and a thickness. Each element is classified into each part as in the case of the main surface. When the element data file is created in this way, the heat exchanger model becomes a model composed of elements decomposed into a mesh.

FIG. 7 is a perspective view of a heat exchanger model synthesized by image processing of a computer according to the element data file of FIG. FIG. 7 shows a state in which the outside of the heat exchanger model 10 to be analyzed is disassembled into elements, but the element data file also includes disassembly of the internal fins and the water pipe penetrating the fins. Elements are included.

In general, in a program of a finite element method such as ABAQUS, when an analysis model is given as a decomposed element, it may be required to give it in accordance with a command suitable for the program. In that case, the command is generated by a predetermined macro program according to the attribute data of the element data file of FIG. 6, and the element data is given in a form suitable for the finite element method program.

Next, for the heat exchanger model, the change in temperature for each element during heating is determined. For this purpose, the actual machine of the actually produced heat exchanger is put into a heated state, its temperature distribution is obtained, and given as additional attribute data to each element of the element data file. In that case, as a method of measuring the temperature of each element, it is preferable to use a thermoviewer to obtain temperature distribution data relatively easily. The thermo viewer detects the radiant heat (or radiant heat) radiated from the surface of the heated model, generates the distribution as radiant heat data of each divided part, and displays the temperature distribution on the display screen in different colors. Things. Therefore, the radiant heat data can be given as additional attribute data to the element data file of FIG.

FIG. 8 is a diagram showing an example of the display output of the thermo viewer. In FIG. 8, the darker portions indicate higher temperatures and the lighter portions indicate lower temperatures. The heat exchanger model is heated by an internal burner, a high temperature is detected in the upper fin portion, and the lower inner trunk portion and skirt portion have a relatively low temperature. Further, since the water circulates inside the water pipe, a very low temperature is detected.

In order to provide the data of the temperature distribution detected from such a thermoviewer as additional attribute data to the element data file, it is necessary to add the data to the outside of the fin, the inner body, the skirt, and the water pipe located on the outer surface. On the other hand, the data of the temperature distribution detected from the thermo-viewer can be directly pasted for each main surface by a complement method or the like. For example, with respect to the main surface M2 (fin outer surface) shown in FIGS. 2 and 3, radiant heat data of the same surface detected by the thermoviewer is used as temperature data of each element by associating the four nodes. Can be. When the radiant heat data of the main surface M2 detected by the thermo viewer is smaller than the number of the element data in FIG. 6, the temperature data of the missing element can be obtained by the complementation method. Conversely, when the radiant heat data of the main surface M2 detected by the thermoviewer is larger than the number of element data in FIG. 6, the radiant heat data is thinned out to obtain the temperature data of the element at the corresponding position.

The temperature data of the element at a position difficult to be detected by the thermoviewer such as inside the fin is obtained by using a thermocouple, a temperature gauge, a data logger, or the like from a heat exchanger model in a heated state only at a main point. The temperature of the unmeasurable element is calculated from the heat conduction characteristics of each component by calculation, and the obtained temperature data is given as additional attribute data of the element.

FIG. 9 is a diagram showing a data structure of the element En when such temperature data is given for every 20 integration points of the attribute data of the element. Temperature data is given to each element based on the external thermal image data from the thermoviewer and the internal temperature data calculated from the temperature data of the representative points and the heat transfer characteristics. Will be sought. Therefore, after that, a strain characteristic F with respect to the temperature of each component is obtained by measuring the characteristic of the material and the thickness of the material, and the strain value of each element (ε = size after expansion due to temperature rise / Original size). Further, the stress σ (Kg / mm ² ) given to each element is determined according to the strain / stress characteristic curve obtained by the tensile test of the material piece of each part. Any of these operations can be easily obtained by a program using a finite element method such as ABAQUS.

FIG. 10 shows an example of a strain / stress characteristic curve of a material having nonlinear characteristics. The state changes from the initial state 1 to the state 2 when heating, and then to the rest state 3 after cooling. In the initial state, there is usually almost no stress and no strain. When heated to a certain temperature state, strain and stress as shown in the figure are applied, and after cooling, the stress as shown in the figure may be applied.

The stress at the time of heating and the stress at the time of rest are:
In an actual machine that repeats normal heating and resting, it is applied as a stress amplitude. Depending on the material of the component to which each element belongs, a life characteristic corresponding to the stress amplitude is provided. Therefore, when the stress amplitude for each element is obtained by the calculation using the finite element method, the element having the largest stress amplitude can be extracted, and the life of the heat exchanger model can be predicted from the maximum stress amplitude.

FIG. 11 shows the stress amplitude on the vertical axis and the repetition on the horizontal axis.
And the life characteristic curves of various parts
It is a curve figure. For example, the maximum stress amplitude is 8.36 kg /
mm ^TwoThen, the life of each component Nf-1, 3, 4 is reached
Is required. Therefore, the designed heat exchange
Obtain the life characteristics of the entire container model and the life characteristics of each element
be able to.

Therefore, based on the life characteristics obtained by the program according to the finite element method as described above, information as to whether or not a heat exchanger having an appropriate structure has been designed and where to improve should be actually obtained. It can be obtained without repeating tens of thousands of heating and resting experiments.

FIG. 12 is a diagram showing the configuration of hardware and software for implementing the above-described high-temperature durability evaluation method. A pre-post workstation 30 and an analysis workstation 40 for executing a heat conduction analysis and a thermal stress analysis are connected. The pre-post workstation 30 stores a file 32 storing a program for creating a finite element method model, a file 34 storing main surface files for the types of heat exchangers, and a main surface file corresponding to the model. File 36 is connected. Further, a personal computer or the like may be further connected to the pre-post workstation 30 and used for creating each file. The analysis workstation 40 is connected with a file 42 storing a finite element method program for performing heat conduction analysis and thermal stress analysis, and files 44 and 46 storing a temperature distribution file and a stress distribution file, respectively. I have.

The main surface file prepared in step S 1 shown in FIG. 1 is stored in the file 34. Steps S2 to S5 are performed by executing the finite element method model creation program on the pre / post workstation 30. That is, the principal plane file corresponding to the model selected from the principal plane file 34 and generated according to the input dimensions is stored in the file 36 in accordance with the input data in step S2. The structure of the data is as shown in FIG.

At steps S4 and S5, the element data file shown in FIG. 6 or FIG. 9 is created by the finite element method model creation program and stored in the file 38. Further, thermal image data (temperature data) from the thermo viewer and temperature data at a specific point from a data logger (not shown) are input to the workstation 30 and the temperature data is added to the element data file 38.

The element data file prepared in this way is transferred to the workstation 40 for analysis, and
According to a finite element method program such as BAQUS, a temperature distribution file 44 and a thermal stress distribution file 46 are created.

In the above embodiment, the heat exchanger is described as an example. However, the present invention is not limited to this, and can be used for stress analysis of various heating devices. Also,
Files 32 and 4 storing the program shown in FIG.
Reference numeral 2 may be any computer-readable storage medium such as a hard disk, a magnetic tape, and a CDROM.

[0043]

As described above, according to the present invention, a model to be analyzed such as a heat exchanger to be analyzed necessary for a computer program using the finite element method can be tens of thousands by a relatively simple operation. The input data can be decomposed into pieces to generate appropriate input data. Therefore, when performing a thermal stress analysis by a computer program using the finite element method, the input data preparation process can be completed in a relatively simple process in a short time, and a realistic simulation of the thermal stress analysis is possible. Can be Furthermore, the stress amplitude and the life characteristics of each element of the analysis model can be obtained by computer simulation by the finite element method, and the high-temperature durability evaluation at the design stage can be performed relatively easily and in a short time.

[Brief description of the drawings]

FIG. 1 is a flowchart of the entire process of the high-temperature durability evaluation method of the present invention.

FIG. 2 is a schematic perspective view of a general heat exchanger used for a water heater or the like.

FIG. 3 is a development view of a main surface.

FIG. 4 is a structural diagram showing a data structure of a main surface file.

FIG. 5 is a diagram illustrating a relationship between a main surface and meshes (elements) when the main surface Mk is divided into a plurality of meshes.

FIG. 6 is a structural diagram showing an example of an element data file.

FIG. 7 is a perspective view of a heat exchanger model synthesized by image processing of a computer according to an element data file.

FIG. 8 is a diagram showing an example of a display output of a thermo viewer.

FIG. 9 is a diagram illustrating stress analysis by the finite element method.

FIG. 10 shows an example of a strain-stress characteristic curve of a material having nonlinear characteristics.

FIG. 11 is a characteristic curve diagram in which life characteristic curves of various components are entered.

FIG. 12 is a diagram showing a configuration of hardware and software for performing the high-temperature durability evaluation method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Heat exchanger M1-M27, Mk Principal surface E1-Em element 30 Workstation for pre-post 32 Model creation program file 34 Principal surface file 36 Principal surface file corresponding to model 38 Element data file 40 Workstation for analysis 42 Finite element method Program file 44 Temperature distribution file 46 Stress distribution file

Claims (5)

[Claims] 1. A step of preparing a plurality of principal plane files having a plurality of principal planes constituting a model of a target device to be subjected to high-temperature durability evaluation, and an evaluation inputted based on the principal plane files. According to the type data of the target model and the dimensional data for specifying the size of the device to be evaluated, coordinate data of at least four nodes defining the respective main surfaces and thickness data are provided as attribute data for each main surface. A step of creating a model-compatible principal surface file, and dividing each principal surface into a plurality of mesh-like elements in accordance with the element division data of the element size or the number of divisions given to the principal surface constituting the model-corresponding principal surface file Splitting and creating an element data file having element data having point data in each element as attribute data; A temperature data detected in a heating state of the actual machine as attribute data to each element data according to the file, and obtaining stress data of each element by a thermal stress analysis program. . 2. The high-temperature durability evaluation method according to claim 1, wherein the element data of the element data file is classified for each component, and the thermal stress analysis program executes a stress-strain curve of the component to which each element belongs. The stress data of the element is obtained according to the following. 3. The high-temperature durability evaluation method according to claim 1, wherein the thermal image data is input as the temperature data from a thermo-viewer that detects radiant heat from the actual device in a heated state and generates thermal image data. Then, thermal image data at a corresponding position is added as attribute data of element data. 4. An evaluation model creation program for a target device to be subjected to a high-temperature durability evaluation, wherein a plurality of models are prepared and have a plurality of main surfaces constituting a model of the target device to be subjected to a high-temperature durability evaluation. Based on the input type data of the model to be evaluated and the dimension data specifying the size of the device to be evaluated based on the surface file, coordinate data and plate thickness data of at least four nodes defining respective main surfaces are obtained. According to a program code for creating a model-compatible principal surface file having attribute data for each principal surface, and element division data of the element size or the number of divisions given to the principal surface constituting the model-corresponding principal surface file, The main surface is divided into multiple mesh-like elements, and element data with point data in each element as attribute data is available. Program codes and the storage medium readable to a computer evaluation model creation program is stored with creating that element data file. 5. The storage medium storing the evaluation model creation program according to claim 4, wherein the element data of the element data file is classified for each component.