JPH10187769A - Device and method for evaluating high-temperature durability - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a system for evaluating high-temp. durability contractible at a low cost, to make it easy to construct the system, to make a miss hardly occur, and to shorten the processing time. SOLUTION: A model generating means 21 generates a simulation model for a heat exchanger, a temperature data setting means 22 sets temperature data in the actual heating state of the heat exchanger corresponding to the model, and a heat conduction analyzing means 23 finds a temperature distribution in the heating state of the heat exchanger; and a heat stress analyzing means 24 finds a stress distribution in the heating state of the model from the found temperature distribution and stress-strain characteristics of a material piece constituting the heat exchanger, and a durability evaluating means 27 evaluates the high-temperature durability of the heat exchanger according to the found stress distribution and life characteristic data. The respective means are actualized by one work station 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-temperature durability evaluation apparatus and method for evaluating the high-temperature durability of a device such as a heat exchanger that is repeatedly heated and stopped.

[0002]

2. Description of the Related Art Hitherto, a device in which a heating state and a resting state are repeated, for example, a heat exchanger has been developed according to the following procedure. That is, first, in the design stage, various numerical values are determined based on a rule of thumb from before. At that time, it is general to adopt a so-called over-spec design in consideration of safety. here,
The design is made based on empirical rules because it is extremely difficult to theoretically analyze the life, especially for fatigue failure, and it is impossible to make a quantitative judgment by calculation. After the design is completed, the environment in which the designed heat exchanger is used is predicted, and a durability test corresponding to the environment is performed.
For example, in the case of a heat exchanger used in a general household water heater, the operation and the stop of the heat exchanger at the maximum output temperature at one-minute intervals are set to 10 minutes.
Repeat 10,000 times (required period is about 5 months). In the case of a heat exchanger used for business equipment, the number of times of operation and stop is 300,000. If there is no problem as a result of the durability test, the development is terminated.

[0003] However, in the conventional development procedure, in particular, the life can be determined only by trial and error based on empirical rules. Therefore, it is difficult to develop a heat exchanger based on a logical or rationally quantitative determination. There was a problem that it was possible. Further, as long as the design based on the empirical rule is performed, it is impossible to perform a novel design that cannot make use of the past experience. As a result, only heat exchangers that are no different from those of the past are designed.

[0004] In the conventional development procedure, the evaluation of the durability test is very important, but the durability test requires enormous monetary cost and time (if a heat exchanger used in a domestic water heater, (About 5 months).

[0005] Further, in the conventional development procedure, the reliability of the endurance test is not perfect because the life cannot be quantitatively evaluated. For this reason, the design had to be over-designed with a large margin of strength.

[0006] In order to address these problems, the present applicant has filed Japanese Patent Application Nos. 7-72601 and 8 filed earlier.
In 161580, a simulation model was created for the equipment to be evaluated for high-temperature durability, and based on the temperature distribution in the heated state of the equipment and the stress-strain characteristics of the material pieces constituting the equipment, a thermal stress analysis was performed. We have proposed a system that evaluates the stress distribution in the heating state of the simulation model and evaluates the high-temperature durability of the equipment based on the stress distribution and the life characteristics of the equipment. According to the system, it is possible to quantitatively evaluate the high-temperature durability of the device.

[0007]

The systems proposed in the above-mentioned patent applications use two workstations connected by a LAN (local area network). One of these two workstations is mainly responsible for pre-post processing such as simulation model creation and high-temperature durability evaluation, and the other one is primarily responsible for analysis processing such as thermal stress analysis. Was supposed to.

However, in such a system,
Since two workstations are used, the system becomes very expensive. In addition, since the two workstations are connected via the LAN, the construction of the system becomes complicated, and there is a problem that unimportant mistakes such as connection mistakes are likely to occur. Further, there is a problem that the process of transferring data via the LAN is complicated and time-consuming, and as a result, the processing time of the entire system becomes long.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has as its object to make it possible to construct a system at low cost, to simplify the construction of the system, to reduce the possibility of errors, and to shorten the processing time. It is an object of the present invention to provide an apparatus and a method for evaluating high-temperature durability.

[0010]

According to the present invention, there is provided a high-temperature durability evaluation apparatus, comprising: a model generating means for generating a simulation model for a device whose high-temperature durability is to be evaluated;
Thermal stress analysis means for obtaining a stress distribution in a heating state of a simulation model created by a model creation means based on a temperature distribution in a heating state of the equipment and a stress-strain characteristic of a piece of material constituting the equipment; Evaluation means for evaluating the high-temperature durability of the equipment based on the stress distribution obtained by the analysis means and the life characteristics of the equipment, wherein these model creation means, thermal stress analysis means and evaluation means are operated by one computer It has been realized.

In this high-temperature durability evaluation apparatus, a simulation model for a device whose high-temperature durability is to be evaluated is created by the model creation means, and the temperature distribution and the equipment in the heating state of the equipment are constituted by the thermal stress analysis means. Based on the stress-strain characteristics of the material piece, a stress distribution in a heated state of the simulation model created by the model creation means is obtained, and the evaluation means
The high-temperature durability of the device is evaluated based on the stress distribution obtained by the thermal stress analysis means and the life characteristics of the device. The model creation means, thermal stress analysis means and evaluation means are realized by one computer.

According to a second aspect of the present invention, there is provided a method for evaluating a high-temperature durability, comprising: a model preparing procedure for preparing a simulation model for a device whose high-temperature durability is to be evaluated; a temperature distribution in a heating state of the device; Based on the stress-strain characteristics, a thermal stress analysis procedure for obtaining a stress distribution in a heating state of the simulation model created by the model creation procedure, and a stress distribution obtained by the thermal stress analysis procedure and a life characteristic of the device. And an evaluation procedure for evaluating the high-temperature durability of the device based on the computer. The model creation procedure, the thermal stress analysis procedure, and the evaluation procedure are executed by one computer.

In this high-temperature durability evaluation method, a simulation model for a device whose high-temperature durability is to be evaluated is created by a model creation procedure, and a temperature distribution and a device in a heated state of the device are configured by a thermal stress analysis procedure. Based on the stress-strain characteristic of the material piece, a stress distribution in a heating state of the simulation model created by the model creation procedure is obtained, and by the evaluation procedure,
The high-temperature durability of the device is evaluated based on the stress distribution obtained by the thermal stress analysis procedure and the life characteristics of the device. The model creation procedure, the thermal stress analysis procedure, and the evaluation procedure are executed by one computer.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is an explanatory view showing a schematic configuration of a high-temperature durability evaluation apparatus according to one embodiment of the present invention. In addition,
Hereinafter, a heat exchanger for a water heater will be described as an example of a device to be evaluated for high-temperature durability. The high-temperature durability evaluation apparatus according to the present embodiment includes a workstation 10 corresponding to a computer according to the present invention that implements a model creating unit, a thermal stress analyzing unit, and an evaluating unit according to the present invention.
It has. The workstation 10 has a file 1 in which a finite element method model creation program is stored.
1, a file 12 storing a finite element method program for performing heat conduction analysis and thermal stress analysis, a file 13 storing main surface files f1, f2, f3,... File 14 in which surface files are stored, file 1 in which element data files are enabled
5, storage means for storing a file 16 storing a temperature distribution file and a file 17 storing a stress distribution file is connected or built in. Further, temperature data of the heat exchanger in the heating state and the like are input to the workstation 10. In addition,
File 11 storing the finite element method model creation program, file 12 storing the finite element method program
The storage means for storing the file 13 storing the main surface file may be an IC (integrated circuit) memory, or various computer-readable storage media such as a hard disk, a magnetic tape, and an optical disk. Similarly, storage means for storing the files 14 to 17
Any type of IC memory, hard disk, magnetic tape, optical disk, or the like may be used as long as it can write and read.

FIG. 2 is a functional block diagram showing the configuration of the high-temperature durability evaluation apparatus according to the present embodiment. The high-temperature durability evaluation apparatus according to the present embodiment includes a terminal 30 for inputting temperature data and the like to the workstation in addition to the workstation 10 described above. This terminal 30 is constituted by, for example, a personal computer.

The workstation 10 has a model creating means 21 for creating a simulation model for a heat exchanger, which is a device whose high-temperature durability is to be evaluated, and a heat model corresponding to the simulation model created by the model creating means 21. Temperature data setting means 22 for setting temperature data in an actual heating state of the exchanger, and a temperature distribution in a heating state of the heat exchanger based on the temperature data and heat conduction characteristics set by the temperature data setting means 22. And a simulation model created by the model creating means 21 based on the temperature distribution obtained by the heat conduction analyzing means 23 and the stress-strain characteristics of the material pieces constituting the heat exchanger. Thermal stress analysis means 2 for obtaining stress distribution in heated state
4, an analysis result verification unit 25 for verifying the validity of the stress distribution obtained by the thermal stress analysis unit 24, a life characteristic data holding unit 26 for storing life characteristic data of the heat exchanger, and a thermal stress analysis unit. A durability evaluation means 27 for evaluating the high-temperature durability of the heat exchanger based on the stress distribution obtained by 24 and the life characteristic data held by the life characteristic data holding means 26 is provided.

The workstation 10 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and an input / output unit (not shown). Alternatively, the above-described units are realized by executing a program stored in an external storage unit. In particular, the model creating means 21 is realized by executing a finite element method model creating program stored in the file 11 shown in FIG. 1, and the heat conduction analyzing means 23 and the thermal stress analyzing means 24 are shown in FIG. This is realized by executing the finite element method program stored in the file 12. Examples of the finite element method program include various commercially available simulation programs for heat conduction analysis or thermal stress analysis (HKS S.D.).
ABAQUS sold by the company) can be used.

The terminal 30 processes the temperature data of each part of the heat exchanger detected by the thermo-viewer 34 and other temperature detecting means 35 into a format suitable for input to the workstation 10, Workstation 1
The temperature data processing means 31 given to the temperature data setting means 22 of 0 and the tensile tester 36 input data obtained by conducting a tensile test on a piece of material constituting each part of the heat exchanger, and input heat exchange. A stress-strain characteristic (stress-strain diagram) is created for each part of the vessel, and the data is given to the thermal stress analysis means 24 of the workstation 10 by a tensile test result processing means 32 and a strain tester 37. A distortion test result processing means 33 is provided for inputting data obtained by measuring the distortion of the heat exchanger in a heated state and for providing the data to the analysis result verification means 25 of the workstation 10.

Next, the operation of the high-temperature durability evaluation apparatus according to the present embodiment and the high-temperature durability evaluation method according to the present embodiment will be described.

FIG. 3 is a flowchart showing the entire operation of the high-temperature durability evaluation apparatus according to the present embodiment. In this operation, first, the model creating means 21 creates a simulation model for a heat exchanger which is a device whose high-temperature durability is to be evaluated (step S101). Next, the temperature data in the actual heating state of the heat exchanger sent from the temperature data processing unit 31 is set by the temperature data setting unit 22 in accordance with the simulation model (step S102). Next, based on the set temperature data and the heat conduction characteristics, the heat conduction analysis unit 23 performs a heat conduction analysis for obtaining a temperature distribution in a heating state of the heat exchanger (step S103). Next, based on the temperature distribution obtained by the heat conduction analysis and the stress-strain characteristics of the material pieces constituting the heat exchanger, the thermal stress analysis means 24
A thermal stress analysis for obtaining a stress distribution in the heating state of the simulation model is performed (step S10).
4). Next, analysis result verification is performed by the analysis result verification means 25 to verify the validity of the stress distribution obtained by the thermal stress analysis (step S105). Next, the durability evaluation means 27 evaluates the high-temperature durability of the heat exchanger based on the stress distribution obtained by the thermal stress analysis and the life characteristic data held by the life characteristic data holding means 26 ( Step S106), the operation ends.

Next, referring to the flowchart of FIG. 4, the simulation model of FIG. 3 is created (step S10).
1) will be described. 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, in order to disassemble the heat exchanger into tens of thousands of mesh-like elements and input them as respective element data in the above-mentioned finite element method program ABAQUS or the like, it is generally necessary to manually operate each one of the elements. It gives a command to the element and is not practical.

Therefore, in the model creation in the present embodiment, the principal surface files in which the heat exchanger model is developed on a plurality of principal surfaces are prepared in advance for the types of the models (the number of turns of the water tubes) (step S111). By giving the type data of the heat exchanger model to be analyzed and the dimension data specifying the size of the heat exchanger (step S112),
The main surface file of the heat exchanger to be analyzed can be easily created. Specifically, a file of three-dimensional coordinates of four nodes of about 250 main surfaces is created from the main surface file corresponding to the model type (step S113). Then, data (the number of divisions or element size) necessary for decomposing (developing) into a mesh (element) is given to each main surface of the main surface file (step S114), whereby the main surface is decomposed into a mesh. An element data file is created (S115). Specifically, an element (mesh) data file having four node coordinates and a plate thickness as attributes or an element (mesh) data file having coordinates of 20 integration points as attributes is created. As described above, in the present embodiment, a data file in which a heat exchanger model required for the finite element method is developed into elements can be generated relatively easily and in a short time.

Next, the creation of the above-described model will be described in detail with reference to FIGS. FIG. 5 is a perspective view of a general heat exchanger 40 used for a water heater or the like. The heat exchanger 40 includes a fin portion 41, an inner trunk portion 42, a skirt portion 43, and a water pipe portion 45. Fin 4
1 and the inner body 42 are connected by a slope 44. Regarding such a heat exchanger 40, the above-described main configuration is the same in all models, and the difference is in the respective dimensions and the number of turns of the water tube. Therefore, in the present embodiment, for the heat exchanger 40, the files developed in advance on the main surface are prepared for the number of turns of the water pipe, thereby providing
If the dimensions and the number of turns of the water pipe are given as input data, the principal plane file of the target heat exchanger model can be created. Note that all types of principal plane files are stored in the file 13 shown in FIG.

FIG. 5 shows, as an example, a heat exchanger in the case where the number of windings of the water pipe is two. In the heat exchanger model in this case, for example, the main surfaces M1 to M shown in FIG.
27, and a developed view thereof is prepared in advance. FIG. 6 shows a part of the development view.
Only the main surface of the portion viewed from the front in FIG. 5 is shown. In this figure, the fin portion 41 has an upper surface M1 and an outer surface M1.
2, the inner body 42 has three surfaces M10, M14, and M18 whose side surfaces are divided by a water pipe portion 45, the skirt portion 43 has a surface M22, and the slope portion 44 has a surface M6.

For example, when the number of turns of the water pipe becomes three, the number of surfaces divided by the water pipe part 45 in the inner body part 42 becomes four. Thus, in that case, another type of principal plane file would be used. In a specific heat exchanger, a portion corresponding to the upper surface M1 is further developed into a plurality of radiating fins and a water pipe penetrating the fins.

By the way, the types of combinations of the developed main surfaces in the heat exchanger are mainly required only for the number of windings, but the size of the decomposed main surfaces differs depending on the dimensions of the heat exchanger. come. Therefore, in step S112 in FIG. 4, the height of the target heat exchanger model
Length L, width W, height H, plate thickness, fin 4 of inner body 42
1 length L, width W, height H, plate thickness, length L, width W, height H, plate thickness of skirt portion 43, water tube position, position of water tube (not shown) entering water tube fin portion 41, Number and thickness of fins,
The data necessary to determine the size of the developed view of the main surface prepared in advance, such as the connection portion between the fin and the water pipe, is given. 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. In addition, the main surface file for the created model is
It is stored in the file 14 in FIG.

FIG. 7 is an explanatory diagram showing the data structure of the principal plane 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 three-dimensional coordinate data of four nodes and data of plate thickness as attribute data thereof. The number of this main surface is, for example, 250
Degree, which is a number that depends on the details of the model of the heat exchanger. Furthermore, if necessary, the inner trunk,
The outer radius of the fin, the radius of the corner of the skirt portion, the radius of the corner of the water tube, the width of the joint portion of the water tube to the inner body, and the like can also be given as input data for determining the main surface. The input data to be given differs depending on how detailed the main surface is. At this stage, the three-dimensional shape of the target heat exchanger model is determined.

When the main surfaces of the target heat exchanger model are specified as described above, each of the main surfaces is divided into meshes. This mesh will be treated as an element in the finite element method. When the main surface is divided into meshes, in the present embodiment, for each main surface,
The number of divisions or the element size (mesh size) is given by the operator.

FIG. 8 is an explanatory diagram showing, as an example, the relationship between a main surface and a mesh (element) when the main surface Mk is divided into a plurality of meshes. The main surface Mk is determined by the coordinates of the four nodes (k1, k2, k3, k4) and the plate thickness d. In the case where the main surface Mk is a simple rectangle, the number of divisions is simply given, and a simple operation is performed, as shown in FIG.
Are decomposed into elements E1, E2,..., En,. Each element is composed of, for example, four nodes ES1, ES2, ES3, ES4 as shown in the lower part of FIG.
And the plate thickness d.

When the main surface Mk is decomposed into meshes (elements), the coordinates of the four nodes of the divided elements and the plate thickness d are obtained by calculation by giving the sizes of the elements. When 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 the coordinates and plate thickness of four nodes, the information is converted into integration points inside each element.
That is, as shown in the lower part of FIG. 8, the attribute data of the element is converted into the coordinates of the integration point 50 as shown by the mark x inside the element. Alternatively, in addition to the coordinates of the four nodes and the plate thickness, the coordinates of 20 integration points 50 may be provided as attribute data. By using such integration points 50 as attribute data, it is possible to easily paste the temperature data to 20 points in the element later.

As shown in the lower part of FIG. 8, not the coordinates of the four nodes and the thickness of the divided element, but the coordinates of the integration point 50 as shown by an internal X mark as its attribute data, as shown in the lower part of FIG. , A finite element method program.

FIG. 9 is an explanatory diagram showing an example of an element data file in the case where attribute data of each element E1,..., En,. Each element is categorized into its parts 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. Note that the created element data file is stored in the file 15 shown in FIG.

FIG. 10 is a perspective view showing a heat exchanger model synthesized by image processing of a computer according to the element data file shown in FIG. In this figure, the outside of the heat exchanger model to be analyzed is disassembled into elements.In the element data file, the inside fin and the water pipe penetrating the fin are also disassembled. Elements are included.

In general, in a finite element method program 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 in accordance with the attribute data of the element data file of FIG. 9, and element data is given in a form suitable for the finite element method program.

After the heat exchanger model is created as described above, a change in the temperature of each element during heating is determined for the model. For that purpose, the actual machine of the heat exchanger actually created is put into a heated state, its temperature distribution is determined,
The temperature data setting means 22 in FIG. 2 gives each element of the element data file as additional attribute data. As a method of measuring the temperature of each element, in order to obtain temperature distribution data relatively easily, a thermo viewer 34 is used.
It is preferable to use The thermo-viewer 34 detects radiant heat (or radiant heat) radiated from the surface of the heated model, generates radiant heat data of each of the divided portions in order to represent the distribution, and based on the radiant heat data, The temperature distribution is displayed on the generated display screen in different colors. Therefore, the radiant heat data can be given as additional attribute data to the element data file shown in FIG.

As for the temperature of the portion where the temperature is difficult to be measured by the thermo-viewer 34 such as inside the fin, for example, only the main points of the heat exchanger in the heated state are indicated by a thermocouple, a temperature gauge, and a data. The temperature is measured by using other temperature detecting means 35 such as a logger, and the measured temperature is given to each point, so that the heat conduction analyzing means 23 in FIG. By the analysis, the temperature data of all the elements can be obtained by calculation.

FIG. 11 is an explanatory diagram showing an example of the display output of the thermo viewer 34. In FIG. 8, a darker portion indicates a higher temperature, and a lighter portion indicates a lower temperature. The heat exchanger model is heated by an internal burner, and a high temperature is detected at the upper fin portion, and a relatively low temperature is detected at the lower inner trunk portion and the skirt portion. Further, in the water pipe portion, a very low temperature is detected because water circulates inside.

When the data of the temperature distribution detected by the thermo-viewer 34 is given as additional attribute data to the element data file, the data is applied to the outside of the fin, the inner body, the skirt, and the water pipe located on the outer surface. The
The data of the temperature distribution detected by the thermoviewer 34 can be directly pasted for each main surface by a complement method or the like. For example, the main surface M2 shown in FIGS.
With respect to the (fin outer side surface), the radiant heat data of the same surface detected by the thermo viewer 34 can be used as the temperature data of each element so as to correspond to the four nodes. When the radiant heat data of the main surface M2 detected by the thermoviewer 34 is smaller than the number of element data in FIG. 9, the temperature data of the missing element can be obtained by the complementation method. Conversely, Thermo Viewer 3
9 shows the radiant heat data of the main surface M2 detected by FIG.
When the number of the element data is larger than the number of the element data, the temperature data of the element at the corresponding position can be obtained by thinning out the radiant heat data.

As described above, the temperature of each portion where the temperature is difficult to be measured by the thermoviewer 34, such as the inside of the fin, is measured at each point, the heat conduction characteristic, and the heat by the finite element method program. The temperature data obtained by the conduction analysis is given as additional attribute data.

Next, a thermal stress analysis by the finite element method is performed by the thermal stress analysis means 24 in FIG. This will be described with reference to FIG. FIG. 12A shows that, as described above, the temperature data is 20
9 shows a data structure of an element En when given for each of the integration points. Thus, the thermo-viewer 34
The temperature data of each element is given by the external temperature data and the temperature data of the main points measured by the above method, and the internal temperature data calculated based on the heat conduction characteristics. Is obtained as data. The temperature distribution file including the data of the temperature distribution is stored in the file 16 in FIG.

Thereafter, as shown in FIG.
Strain characteristic F = f (m, T) with respect to temperature of each part
(Function of the part m and the temperature T) is obtained by measuring the properties of the material and the thickness of the material, etc., and the strain amount F of each element (= size after expansion due to temperature rise / original size) is obtained by the strain property F. )
Ask for.

Next, as shown in FIG. 12 (c), the stress-strain characteristic (temperature) as a variable obtained by measuring each material piece of each part of the heat exchanger by the tensile tester 36 was obtained. −strain applied to each element according to the strain curve)
mm ² ). All of these operations are ABAQ
It can be easily obtained by a program using the finite element method such as the US.

Next, the analysis result verification means 25 shown in FIG.
, An analysis result verification for verifying the validity of the stress distribution obtained by the thermal stress analysis is performed. Specifically, a strain test is performed on the heated heat exchanger by the strain tester 37, the test result is processed by the strain test result processing unit 33, and the result is sent to the analysis result verification unit 25 of the workstation 10. The analysis result verification means 25 compares the strain obtained during the thermal stress analysis with the actually measured strain,
If there is no significant difference between them, it is determined that the stress distribution obtained by the thermal stress analysis is appropriate.

It is desirable that this analysis result verification be performed, but it may be omitted. When the analysis result verification is omitted, the analysis result verification unit 25, the distortion test result processing unit 33, and the distortion tester 37 in FIG. 2 and the analysis result verification in FIG. 3 (step S105) are omitted.

Next, also in the rest state (non-heated state), the stress applied to each element is determined, and the difference (amplitude) between the stress in the heated state and the stress in the pause state is determined. By extracting the stress amplitude (maximum stress amplitude) of the element having the maximum stress amplitude when the operation and suspension are repeated, the life of the heat exchanger subjected to the analysis can be known.

FIG. 13 shows the stress of a material having linear characteristics.
7 shows an example of a distortion curve. In the case of a material having linear characteristics, the stress in the initial state before heating is equal to the stress in the rest state after heating. Therefore, the stress amplitude is equal to the difference between the stress in the heated state and the stress in the initial state.

On the other hand, as shown in an example of the stress-strain curve of the material having the non-linear characteristic in FIG. 14, in the case of the material having the non-linear characteristic, the stress in the initial state and the resting state after heating are obtained. Are not equal. Further, as shown in FIG. 15, in a durability test or the like, a cycle in which the next heating is started before the temperature falls to the temperature in the initial state is performed. Some materials do not match the stress in the later rest state. In the case of the material having the non-linear characteristic shown in FIG. 14 or the material shown in FIG. 15, the stress amplitude as the criterion for determining the durability against the high-temperature damage includes the stress in the heating state and the resting state. Should be adopted. for that reason,
Prior to determining the maximum stress amplitude, the stress distribution in the rest state is determined.

Once the stress amplitude is determined in this way, the durability against high-temperature damage is evaluated by the durability evaluation means 27 in FIG. In this case, the material constituting the components of the heat exchanger is known in advance, and various data are available for the life characteristics (fatigue curve) indicating the relationship between the stress amplitude and the life of the material. Therefore, for example, FIG.
As shown in FIG. 1, life characteristic data with the stress amplitude on the vertical axis and the number of repetitions of operation / stop on the horizontal axis are stored in advance in the life characteristic data holding means 26 in FIG. From the stress amplitude in the heat exchanger, the limit number of repetitions corresponding to the stress amplitude can be obtained using the life characteristic data shown in FIG. FIG.
In FIG. 6, reference characters Nf-1 to Nf-4 denote the types of materials. Then, for example, if the limit number of repetitions exceeds 100,000 times, it can be evaluated that the high-temperature damage durability as a heat exchanger in which household products are used is sufficient.

Here, FIG. 16 will be explained. If the stress amplitude is 8.36 kg / mm ² , even a component made of a material having high-temperature durability indicated by reference symbol Nf-3 in FIG. 16 can withstand about 320,000 repetitions of operation and suspension. Because it can also be used for home use,
It is evaluated that the high-temperature durability is sufficient even for heat exchangers used for commercial products. Also, in FIG.
Since a component made of a material having high-temperature durability indicated by f-1 can withstand about 650,000 repetitions of operation and suspension, the high-temperature durability for business use is evaluated to be sufficient. .

On the other hand, in FIG.
In the case of a component made of a material having high-temperature durability indicated by No. 4, it is determined that the component has sufficient high-temperature durability for home use since the limit number of repetitions exceeds 100,000 times. Since it has not been reached, its high-temperature durability is evaluated to be insufficient as a heat exchanger used for commercial products.

As described above, the determination of the high-temperature durability in the present embodiment is based on the assumption that the limit number of repetitions obtained from the life characteristic data as shown in FIG. 15 is a predetermined number (for example, 100,000 times for a home heat exchanger). 300,000 times for commercial heat exchangers)
Is very accurate because it is a quantitative determination of whether or not it exceeds. Therefore, according to the present embodiment, information on whether a heat exchanger having an appropriate structure is designed, and information on a place to be improved, etc. is actually subjected to tens of thousands of repeated heating and rest experiments. Can be obtained by simulation without the need.

Further, according to the apparatus and method for evaluating high-temperature durability according to the present embodiment, model creating means 21, temperature data setting means 22, heat conduction analyzing means 23, thermal stress analyzing means 24, analysis result verifying means 25 And durability evaluation means 2
7, one computer (workstation 10)
The model creation shown in FIG. 3 (step S
101) to the durability evaluation (step S106) by one computer (workstation 1).
0), the system can be executed stand-alone, so that a system for evaluating high-temperature durability can be constructed inexpensively, the system can be constructed easily, mistakes such as connection mistakes are less likely to occur, and a plurality of systems can be constructed. Since the data transfer between the workstations does not occur, the processing time can be reduced.

Further, according to the apparatus and method for evaluating high-temperature durability according to the present embodiment, a simulation model of a device whose high-temperature durability is to be evaluated is decomposed into tens of thousands of elements by a relatively simple operation. Thus, appropriate input data can be created. 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.

The present invention is not limited to the above-described embodiment. For example, in the above-described embodiment, a heat exchanger for a water heater has been described as an example of a device to be evaluated for high-temperature durability. The present invention is not limited to this, but includes heat exchangers for gas air conditioners, combustion chambers for fan heaters using gas or oil, heat exchangers for FF (Forced Flue) heaters, water / water heat exchangers, boilers, ceramic heaters, The present invention can be applied to all devices to which thermal stress is applied, such as a heat exchanger of an oil heater, an electric pot, and a rice cooker. Even when evaluating the high-temperature durability of equipment other than heat exchangers for water heaters,
Similar to the embodiment, a simulation model of the target device is created, and other processes and data may be changed to those suitable for the target device.

FIG. 17 shows an example of creating a model for a combustion chamber of a fan heater as an example of equipment other than a heat exchanger for a water heater. In the case of the combustion chamber of this fan heater,
As shown in FIG. 17, the model of the combustion chamber of the fan heater is decomposed into main surfaces M1, M2,... Corresponding to the respective planes. Subsequent processing is the same as that of the heat exchanger for a water heater.

The computer in the present invention is not limited to the workstation 10, but may be a personal computer or the like.

The simulation model in the present invention is preferably a finite element method model, but is not limited to the finite element method model, and is a model that can be used in a simulation effectively executed using a computer. Is fine. Similarly, the thermal stress analysis in the present invention is not limited to the one using the finite element method. If the temperature data of all the elements can be obtained by actual measurement without performing the heat conduction analysis, the heat conduction analysis means 23 in FIG. 2 and the heat conduction analysis (step S103) in FIG. 3 may be omitted.

[0061]

As described above, according to the high temperature durability evaluation apparatus of the present invention, the model creation means, the thermal stress analysis means and the evaluation means are realized by a single computer. According to the performance evaluation method, the model creation procedure, the thermal stress analysis procedure, and the evaluation procedure are executed by one computer, so that the system can be constructed at low cost, and the construction of the system is simplified, and errors occur. This is advantageous in that the processing time can be reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a schematic configuration of a high-temperature durability evaluation apparatus according to an embodiment of the present invention.

FIG. 2 is a functional block diagram showing a configuration of the high-temperature durability evaluation device shown in FIG.

FIG. 3 is a flowchart showing the entire operation of the high-temperature durability evaluation apparatus shown in FIG. 1;

FIG. 4 is a flowchart for explaining creation of a simulation model in FIG. 3;

FIG. 5 is a perspective view of a general heat exchanger used for a water heater or the like.

6 is a development view of a main surface of the model of the heat exchanger shown in FIG.

FIG. 7 is an explanatory diagram showing a data structure of a main surface file according to the embodiment of the present invention.

FIG. 8 is an explanatory diagram showing a relationship between a main surface and a mesh (element) in one embodiment of the present invention.

FIG. 9 is an explanatory diagram illustrating an example of an element data file according to an embodiment of the present invention.

FIG. 10 is a perspective view showing a heat exchanger model synthesized by image processing of a computer according to the element data file shown in FIG. 9;

FIG. 11 is an explanatory diagram showing an example of a display output of a thermo viewer according to an embodiment of the present invention.

FIG. 12 is an explanatory diagram for describing thermal stress analysis according to one embodiment of the present invention.

FIG. 13 is a characteristic diagram showing an example of a stress-strain curve of a material having linear characteristics.

FIG. 14 is a characteristic diagram showing an example of a stress-strain curve of a material having nonlinear characteristics.

FIG. 15 is an explanatory diagram showing a heating and rest cycle in a durability test and the like.

FIG. 16 is a characteristic diagram illustrating an example of life characteristic data according to an embodiment of the present invention.

FIG. 17 is a perspective view showing an example of creating a model for a combustion chamber of a fan heater.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Workstation 11-17 File 21 Model creation means 22 Temperature data setting means 23 Heat conduction analysis means 24 Thermal stress analysis means 25 Analysis result verification means 26 Life characteristic data holding means 27 Durability evaluation means

Claims (2)

[Claims] 1. A model creating means for creating a simulation model for a device for which high-temperature durability is to be evaluated, and a temperature distribution in a heating state of the device and a stress-strain characteristic of a piece of material constituting the device. Thermal stress analysis means for obtaining a stress distribution in a heating state of the simulation model created by the model creation means; and a high temperature of the equipment based on the stress distribution obtained by the thermal stress analysis means and the life characteristics of the equipment. A high-temperature durability evaluation apparatus comprising: evaluation means for evaluating durability; wherein the model creation means, thermal stress analysis means, and evaluation means are realized by one computer. 2. A model creation procedure for creating a simulation model for a device to be evaluated for high-temperature durability, based on a temperature distribution in a heating state of the device and a stress-strain characteristic of a material piece constituting the device. A thermal stress analysis procedure for obtaining a stress distribution in the heating state of the simulation model created by the model creation procedure; and a high temperature of the equipment based on the stress distribution obtained by the thermal stress analysis procedure and the life characteristics of the equipment. A high-temperature durability evaluation method, comprising: an evaluation procedure for evaluating the durability; and a model creation procedure, a thermal stress analysis procedure, and an evaluation procedure performed by a single computer.