Thermal analysis method, thermal analysis apparatus, and thermal analysis program

Abstract

To provide a thermal analysis method, a thermal analysis apparatus, and a thermal analysis program capable of easily calculating a heat transfer coefficient of a bus bar.SOLUTION: A thermal analysis method includes a calculation step of calculating heat transfer coefficient h1 of a bus bar 10, and a thermal analysis step (S14) of performing thermal analysis of the bus bar 10 using the heat transfer coefficient h1 calculated in the calculation step, and in the calculation step, when the bus bar 10 is a rectangular parallelepiped and length D in an extending direction X in a plan view is longer than width W, the heat transfer coefficient h1 is calculated using the sum of the length D in the extending direction X and the width W as the length D in the extending direction X.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a thermal analysis method, a thermal analysis device, and a thermal analysis program. [Background technology]

[0002] Conventionally, as a thermal analysis method, a thermal analysis device, and a thermal analysis program, for example, as described in Patent Document 1, a thermal analysis method, a thermal analysis device, and a thermal analysis program are known in which a wire harness is divided in the longitudinal direction, thermal characteristic parameters of the divided parts are calculated by thermal analysis, a thermal equivalent circuit of the wire harness is created based on the calculated thermal characteristic parameters, and a thermal network method is executed to perform a thermal analysis of the wire harness. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-128426 Summary of the Invention [Problem to be solved by the invention]

[0004] The above-described thermal analysis method, thermal analysis device, and thermal analysis program can be applied to a busbar. For example, when performing a thermal analysis of a busbar, it is conceivable to calculate the heat transfer coefficient of the busbar and then calculate the busbar temperature using a thermal network analysis. The heat transfer coefficient is calculated using a coefficient corresponding to the surface morphology of the busbar, the temperature difference between the ambient temperature and the busbar temperature, the representative length of the busbar, and other factors. However, multiple models are required to perform a thermal analysis of one busbar, and the amount of calculation required to calculate the heat transfer coefficient is significant. Therefore, there is a need for a technology that can easily calculate the heat transfer coefficient in a thermal analysis of a busbar.

[0005] Therefore, an object of the present invention is to provide a thermal analysis method, a thermal analysis device, and a thermal analysis program that can easily calculate the heat transfer coefficient of a bus bar. [Means for solving the problem]

[0006] That is, the thermal analysis method according to the present invention includes a calculation step of calculating a heat transfer coefficient of a busbar, and a thermal analysis step of performing a thermal analysis of the busbar using the heat transfer coefficient calculated in the calculation step, and the calculation step is configured to calculate the heat transfer coefficient by defining the sum of the length in the extension direction and the width as the length in the extension direction when the busbar is a rectangular parallelepiped and the length in the extension direction in a plan view is longer than the width. [Effects of the Invention]

[0007] According to the thermal analysis method, the thermal analysis device, and the thermal analysis program of the present invention, the heat transfer coefficient of the bus bar can be easily calculated. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram of a busbar that is a thermal analysis target of a thermal analysis method, a thermal analysis device, and a thermal analysis program according to an embodiment. [Figure 2] FIG. 2 is a perspective view of a bus bar that is the subject of thermal analysis by the thermal analysis method, the thermal analysis device, and the thermal analysis program according to the embodiment. [Figure 3] FIG. 3 is a block diagram showing an outline of the electrical configuration of the thermal analysis device according to the embodiment. [Figure 4] FIG. 4 is an explanatory diagram of a thermal analysis model of a bus bar in the thermal analysis method, the thermal analysis device, and the thermal analysis program according to the embodiment. [Figure 5] FIG. 5 is a flowchart showing a thermal analysis method according to the embodiment. [Figure 6] FIG. 6 is a diagram showing a thermal analysis result in the thermal analysis method, the thermal analysis device, and the thermal analysis program according to the embodiment. [Figure 7] FIG. 7 is a diagram showing a thermal analysis result in the thermal analysis method, the thermal analysis device, and the thermal analysis program according to the embodiment. [Figure 8] FIG. 8 is a diagram showing the results of thermal analysis of the comparative example. [Figure 9] FIG. 9 is a diagram showing the results of thermal analysis of the comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to these embodiments. Furthermore, the components in the following embodiments include those that are easily replaceable by those skilled in the art, or those that are substantially the same.

[0010] [Embodiment] The present embodiment relates to a thermal analysis method, a thermal analysis device, and a thermal analysis program. In the following description, of a first direction, a second direction, and a third direction that intersect with each other, the first direction is referred to as the "extension direction X," the second direction is referred to as the "width direction Y," and the third direction is referred to as the "height direction Z." Here, the extension direction X, the width direction Y, and the height direction Z are perpendicular to each other. The extension direction X corresponds to the direction in which the bus bar extends. The width direction Y corresponds to the direction of the width of the bus bar. The width direction Y and the height direction Z intersect with the extension direction X. Furthermore, unless otherwise specified, each direction used in the following description represents the direction in which each part is assembled to each other. Note that orthogonal here includes nearly orthogonal.

[0011] As shown in FIG. 1, a busbar 10, which is the subject of thermal analysis, is a conductor that electrically connects electrical components mounted on a vehicle and is formed, for example, as a rectangular parallelepiped. Here, the term "rectangular parallelepiped" includes a substantially rectangular parallelepiped. The busbar 10 has conductive members connected to both ends in the extension direction X, and is used, for example, by being connected to electric wires 12 via terminals 11 at both ends. For example, the busbar 10 is housed in an electrical junction box, and multiple busbars 10 are arranged inside the electrical junction box.

[0012] As shown in Fig. 2, busbar 10 passes current along extension direction X, and is formed such that the length in extension direction X is longer than the width W and height H. In Fig. 2, busbar 10 is arranged horizontally so that the width W is longer than the height H. Busbar 10 may also be arranged vertically so that the height H is longer than the width W. Busbar 10 may also be a covered busbar in which the conductor is covered with an insulating coating.

[0013] The thermal analysis method, thermal analysis device 1, and thermal analysis program according to the present embodiment are applied to, for example, the thermal analysis of a busbar 10 housed in an electrical junction box. That is, the thermal analysis method, thermal analysis device, and thermal analysis program according to the present embodiment calculate the heat transfer coefficient for natural convection 60 that occurs around the busbar 10 when the busbar 10 generates heat during operation of the electrical junction box, and predict the temperature or temperature rise of the busbar 10.

[0014] 3, the thermal analysis device 1 includes a control unit 2, an input unit 3, and an output unit 4, and is configured by, for example, a computer system including an input / output interface, a processor, and a memory. The input unit 3 is a unit that inputs data and the like to the control unit 2, and corresponds to, for example, a keyboard, a mouse, etc. The output unit 4 is a unit that outputs the analysis results of the control unit 2, and corresponds to, for example, a monitor, a speaker, etc.

[0015] The control unit 2 is a control unit that performs thermal analysis and temperature prediction, and is configured, for example, by a computer main body. The control unit 2 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), etc. For example, the control unit 2 loads a thermal analysis program stored in the ROM into the RAM and executes it with the CPU to perform thermal analysis and temperature prediction of the busbar 10.

[0016] The control unit 2 includes a model setting unit 21, a temperature setting unit 22, a calculation unit 23, a thermal analysis unit 24, and a storage unit 25. The model setting unit 21, the temperature setting unit 22, the calculation unit 23, and the thermal analysis unit 24 are configured, for example, by installing a thermal analysis program into the control unit 2. Furthermore, the model setting unit 21, the temperature setting unit 22, the calculation unit 23, and the thermal analysis unit 24 may be configured as individual control units.

[0017] As shown in Fig. 4, the model setting unit 21 sets a thermal analysis model 211 for the busbar 10 using a thermal network method. Fig. 4 is a schematic diagram of the thermal analysis model 211 for thermally analyzing the busbar 10. The thermal analysis model 211 is a thermal equivalent circuit of the busbar 10, and, for example, thermal resistances R1 to R3 are set between the busbar 10 and the environment G. The environment G corresponds to the air surrounding the busbar 10. Heat emitted from the busbar 10 moves to the environment G via the thermal resistances R1 to R3.

[0018] The thermal resistance R1 is the thermal resistance due to convection on the upper surface 10A and the lower surface 10B of the busbar 10. For example, the thermal resistance R1 is set using the heat transfer coefficient due to convection from the upper surface 10A and the lower surface 10B to the surrounding air. Specifically, the thermal resistance R1 is set as the reciprocal of the product of the heat transfer coefficient h1 due to convection from the upper surface 10A and the lower surface 10B to the surrounding air and the area of ​​the upper surface 10A and the lower surface 10B. In other words, when the area of ​​both the upper surface 10A and the lower surface 10B is S1, the thermal resistance R1 is expressed as (2·S1·h1) -1 is set as

[0019] The heat transfer coefficient h1 is expressed as K·C·(ΔT / L) where K is a first coefficient that depends on the ambient temperature around the busbar 10, C is a second coefficient that depends on the surface configuration of the upper surface 10A and the lower surface 10B, ΔT is the difference between the temperature of the busbar 10 and the ambient temperature, and L is the characteristic length of the busbar 10. 1 / 4The representative length L is a parameter of the representative length of the busbar 10, and is set as 2·W when the busbar 10 is arranged horizontally, with the length in the extension direction X being D and the length in the width direction Y being W. The busbar 10 being arranged horizontally means that the busbar 10 is arranged so that the length in the width direction Y is longer than the length in the height direction in a cross section intersecting with the extension direction X of the busbar 10, and is, for example, a horizontal arrangement in which the wide surface of the busbar 10 is oriented horizontally. Here, the horizontal arrangement also includes an arrangement that is approximately horizontal.

[0020] Generally, the representative length of the busbar 10 when it is arranged horizontally is set to 2·D·W / (D+W). In contrast, in the thermal analysis device 1 according to this embodiment, the representative length L of the busbar 10 when it is arranged horizontally is set to 2·W. This simplifies the representative length L of the thermal analysis device 1 according to this embodiment, making it easy to calculate the heat transfer coefficient of the busbar 10 and smoothly performing thermal analysis of the busbar 10.

[0021] When the length D of the busbar 10 in the extension direction X is longer than the width W in the width direction Y, particularly when the length D in the extension direction X is sufficiently longer than the width W in the width direction Y, the representative length L of the busbar 10 can be approximated as 2·W, making it easy and appropriate to perform thermal analysis of the busbar 10. Furthermore, by setting the thermal resistances due to convection on the top surface 10A and the bottom surface 10B of the busbar 10 as a single thermal resistance as the thermal resistance R1, it is possible to perform thermal analysis of the busbar 10 more easily than when the thermal resistance due to convection on the top surface 10A and the thermal resistance due to convection on the bottom surface 10B are set as two separate thermal resistances.

[0022] The thermal resistance R2 is the thermal resistance due to convection at the side surfaces 10C and 10D of the busbar 10. For example, the thermal resistance R2 is set using the heat transfer coefficient due to convection from the side surfaces 10C and 10D to the surrounding air. Specifically, the thermal resistance R2 is set as the reciprocal of the product of the heat transfer coefficient h2 due to convection from the side surfaces 10C and 10D to the surrounding air and the area of ​​the side surfaces 10C and 10D. In other words, if the areas of the side surfaces 10C and 10D are both S2, the thermal resistance R2 is (2·S2·h2)-1 is set as

[0023] The heat transfer coefficient h2 is expressed as K·C·(ΔT / L2) where K is a first coefficient that depends on the ambient temperature around the busbar 10, C2 is a second coefficient that depends on the surface configuration of the side surfaces 10C and 10D, ΔT is the difference between the temperature of the busbar 10 and the ambient temperature, and L2 is the characteristic length of the busbar 10. 1 / 4 When the length of the busbar 10 in the height direction is H, the characteristic length L2 is set as H.

[0024] Although the busbar 10 has end faces on both sides in the extension direction X, the thermal analysis device 1 omits calculation of convective heat transfer at the end faces in the extension direction X. This is because, because the terminals 11 and the electric wires 12 are connected to the end faces in the extension direction X, the convective heat transfer at the end faces is different from that at the side faces 10C and 10D, and omitting this calculation in the thermal analysis of the busbar 10 has little effect on the temperature prediction of the busbar 10. By omitting calculation of convective heat transfer at the end faces in the extension direction X, the thermal analysis device 1 can smoothly perform the thermal analysis of the busbar 10 without complicating it.

[0025] The thermal resistance R3 represents the thermal resistance due to radiation on the entire surface of the busbar 10. The thermal resistance R3 can be set using a known method, for example, using the emissivity of the busbar 10, the view factor, the area of ​​the entire surface of the busbar 10, the ambient temperature, etc.

[0026] 3, temperature setting unit 22 sets the boundary temperature of busbar 10. The boundary temperature is, for example, the boundary condition or ambient temperature of busbar 10, and is set as the initial value of the temperature before thermal analysis is performed.

[0027] Calculation unit 23 calculates the heat transfer coefficient, thermal resistance, etc. of busbar 10. When multiple busbars 10 are installed, calculations are performed for each busbar 10. Calculation unit 23 calculates the heat transfer coefficient, thermal resistance, etc. of busbar 10 using thermal analysis model 211 of busbar 10 set in model setting unit 21.

[0028] The thermal analysis unit 24 performs a thermal analysis of the busbar 10 using the heat transfer coefficient, thermal resistance, and the like of the busbar 10. For example, the thermal analysis unit 24 calculates the temperature of the busbar 10 using the heat transfer coefficient, thermal resistance, and the like of the busbar 10 calculated by the calculation unit 23. Specifically, the volume resistivity, electrical resistivity, current value flowing through the busbar 10, ambient temperature around the busbar 10, and initial temperature of the busbar 10 are set as temperature calculation conditions, and the heat generation amount Q of the busbar 10 is calculated. Then, the heat transfer coefficient h1, heat transfer coefficient h2, thermal resistance R1, thermal resistance R2, and thermal resistance R3 of the busbar 10 are calculated. Then, a combined thermal resistance RA of the thermal resistances R1, R2, and R3 is calculated. The estimated temperature T of the busbar 10 is calculated as the sum (RA·Q+T0) of the product of the combined thermal resistance RA and the heat generation amount Q and the ambient temperature T0.

[0029] The memory unit 27 stores various data related to thermal analysis in the thermal analysis device 1. For example, the size and length of the busbar 10, the volume resistivity and electrical resistivity of the busbar 10, the value of the current flowing through the busbar 10, the ambient temperature around the busbar 10, and the initial temperature of the busbar 10 are set and stored in the memory unit 27.

[0030] Next, a thermal analysis method, the operation of the thermal analysis device 1, and the execution of the thermal analysis program according to this embodiment will be described.

[0031] Fig. 5 is a flowchart showing a thermal analysis method according to this embodiment. The flowchart in Fig. 5 also shows the operation of the thermal analysis apparatus 1 and the execution of the thermal analysis program. The flowchart in Fig. 5 is executed by, for example, the control unit 2 of the thermal analysis apparatus 1.

[0032] As shown in step S10 of FIG. 5 (hereinafter simply referred to as "S10," the same applies to S10 and subsequent steps), a thermal analysis model 211 of the busbar 10 is set. This setting step is a step of setting the thermal analysis model 211 according to the busbar 10. For example, the model setting unit 21 sets the thermal analysis model 211 according to the specifications of the busbar 10, including the size of the busbar 10. Specifically, as shown in FIG. 4, thermal resistances R1 to R3 and heat transfer coefficients h1 and h2 of a thermal equivalent circuit are set for the busbar 10, and the thermal analysis model 211 is set. At this time, the heat transfer coefficient h1 of the thermal resistance R1 due to convection on the top surface 10A and the bottom surface 10B of the busbar 10 uses 2·W as the representative length L.

[0033] 5, where a temperature setting step is performed. This temperature setting step is a step of setting a temperature in the thermal analysis model 211. For example, the temperature setting unit 22 sets the ambient temperature around the busbar 10 and the initial temperature of the busbar 10.

[0034] Then, the process proceeds to S14, where a thermal analysis step is performed. This thermal analysis step is a step of calculating the heat transfer coefficient and performing a thermal analysis of the busbar 10 under the conditions set in S10 to S12. For example, the thermal analysis unit 24 performs a thermal analysis of the busbar 10, calculates the heat transfer coefficients h1 and h2, and predicts and outputs the temperature of the busbar 10. That is, the thermal analysis unit 24 calculates the heat transfer coefficients h1 and h2 and the thermal resistances R1 to R3 set in the model setting step of S10, and calculates the temperature of the busbar 10. At this time, the calculation of the thermal resistance R1 is facilitated by using the heat transfer coefficient h1 with a simplified characteristic length L. Furthermore, the heat transfer coefficient h1 with a simplified characteristic length L can be applied to busbars 10 of different sizes and is therefore versatile.

[0035] Then, the process proceeds to S16, where it is determined whether the temperature of the busbar 10 calculated in the thermal analysis process matches the initial temperature set in S12. If the temperature of the busbar 10 calculated in the thermal analysis process does not match the initial temperature set in S12, the process returns to the temperature setting process of S12. In this case, the temperature of the busbar 10 calculated in the thermal analysis process of S14 is reset as the initial temperature. Then, the thermal analysis process of S14 is performed again.

[0036] On the other hand, if it is determined that the temperature of the busbar 10 calculated in the thermal analysis step of S16 matches the initial temperature set in S12, it is determined that the temperature prediction of the busbar 10 is complete, and the series of control processes in FIG. 5 ends. Note that in S16, the case where the calculated temperature of the busbar 10 matches the initial temperature includes the case where the temperature almost matches the initial temperature. For example, if the temperature of the busbar 10 calculated in the thermal analysis step of S16 is within a predetermined temperature range of the initial temperature set in S12, it is determined that the temperature matches the initial temperature set in S12. The predicted temperature of the busbar 10 is then output to the output unit 4.

[0037] Such a thermal analysis method, a thermal analysis program, and a thermal analysis device 1 can easily calculate the heat transfer coefficient h1 of the busbar 10 by using the simplified characteristic length L. Furthermore, the thermal analysis method, the thermal analysis program, and the thermal analysis device 1 can appropriately predict the temperature of the busbar 10 based on the heat transfer coefficient h1 using the simplified characteristic length L.

[0038] 6 and 7 show the temperatures of the busbar 10 predicted by the thermal analysis method, thermal analysis program, and thermal analysis device 1 according to this embodiment. FIG. 6 shows the predicted temperatures when the busbar 10 is horizontally arranged, and FIG. 7 shows the predicted temperatures when the busbar 10 is vertically arranged. A vertical arrangement refers to an arrangement in which the busbar 10 is oriented vertically, with the wide surface of the busbar 10 facing vertically. In FIGS. 6 and 7, the horizontal axis represents the current flowing through the busbar 10, and the vertical axis represents the predicted temperature and the temperature deviation. In FIGS. 6 and 7, the predicted temperature of the busbar 10 obtained by the thermal analysis method, thermal analysis program, and thermal analysis device 1 according to this embodiment is shown as a 1D dashed line, and the detailed results of the thermal fluid analysis are shown as a 3D solid line. The difference between the 1D and 3D values ​​is shown as a deviation with a dashed-dotted line. In FIGS. 6 and 7, the ambient temperature around the busbar 10 is set to 20 degrees Celsius.

[0039] 6 and 7, the center of the vertical axis is the position where the deviation is zero, and the closer the deviation is to the center of the vertical axis, the more appropriate the predicted temperature of the thermal analysis method, thermal analysis program, and thermal analysis device 1 according to this embodiment. Also, (A) to (D) of Fig. 6 and Fig. 7 show the results of predicted temperatures when the width W of the busbar 10 in the width direction Y is changed. Fig. 6(A) shows the case where the busbar 10 is 20 mm wide and 5 m high, Fig. 6(B) shows the case where the busbar 10 is 30 mm wide and 5 m high, Fig. 6(C) shows the case where the busbar 10 is 40 mm wide and 5 m high, and Fig. 6(D) shows the case where the busbar 10 is 50 mm wide and 5 m high. Figure 7(A) shows the case where the busbar 10 has a vertical width of 20 mm and a horizontal height of 5 m, Figure 7(B) shows the case where the busbar 10 has a width of 30 mm and a height of 5 m, Figure 7(C) shows the case where the busbar 10 has a width of 40 mm and a height of 5 m, and Figure 7(D) shows the case where the busbar 10 has a width of 60 mm and a height of 5 m.

[0040] Looking at the predicted temperatures of the thermal analysis method, thermal analysis program, and thermal analysis device 1 according to this embodiment in Figure 6, (A) to (D) of Figure 6 show that the deviation from the thermal convection analysis is about ±4 degrees, and good analysis results are obtained. Also, looking at the predicted temperatures of the thermal analysis method, thermal analysis program, and thermal analysis device 1 according to this embodiment in Figure 7, (A) to (D) of Figure 7 show that the deviation from the thermal convection analysis is about ±3 degrees, and good analysis results are obtained.

[0041] In contrast, the predicted temperatures of a comparative example are shown in FIGS. 8 and 9. FIG. 8 shows the predicted temperatures when the busbar is horizontally arranged, and FIG. 9 shows the predicted temperatures when the busbar is vertically arranged. For the horizontal arrangement in FIG. 8, 2·D·W / (D+W) is used as the representative length of the heat transfer coefficient. D is the length of the busbar in the extension direction X, and W is the length in the width direction Y. Looking at the predicted temperatures in FIG. 9, they are almost the same as those predicted by the thermal analysis method, thermal analysis program, and thermal analysis device 1 according to this embodiment in FIG. 7, and good analysis results are obtained. However, the predicted temperatures in FIG. 8 deviate more significantly as the current value increases, and the predicted temperature of the busbar cannot be said to be appropriate. In this respect, it can be seen that the thermal analysis method, thermal analysis program, and thermal analysis device 1 according to this embodiment can accurately predict the temperature of the busbar 10.

[0042] As described above, the thermal analysis method, the thermal analysis device 1, and the thermal analysis program according to the present embodiment can easily calculate the heat transfer coefficient h1 of the busbar 10 by simplifying the calculation of the heat transfer coefficient h1 by defining the sum of the length D in the extension direction X of the busbar 10 and the width W as the length D in the extension direction X.

[0043] Furthermore, the thermal analysis method, the thermal analysis device 1, and the thermal analysis program according to this embodiment calculate the heat transfer coefficient h1 by K C (ΔT / L) where K is a first coefficient that depends on the ambient temperature, C is a second coefficient that depends on the surface form of the busbar 10, ΔT is the difference between the temperature of the busbar 10 and the ambient temperature, and L is the characteristic length of the busbar 10. 1 / 4Then, when the width of the busbar 10 is W, the characteristic length L is calculated as 2·W, and the heat transfer coefficient h1 is calculated. This simplifies the heat transfer coefficient h1, and the heat transfer coefficient h1 can be easily calculated.

[0044] Furthermore, the thermal analysis method, thermal analysis device 1, and thermal analysis program according to the present embodiment can accurately predict the temperature of the busbar 10 by calculating the heat transfer coefficient h1 of the busbar 10 that is disposed horizontally.

[0045] The thermal analysis method, thermal analysis device, and thermal analysis program according to the present invention are not limited to the above-described embodiment, and various modifications are possible within the scope of the claims. The thermal analysis method, thermal analysis device 1, and thermal analysis program according to this embodiment may be configured by appropriately combining the components of the above-described embodiment and modified examples.

[0046] For example, in the above-described embodiment, a thermal analysis of the bus bar 10 mounted on a vehicle is described, but a thermal analysis of a bus bar not mounted on a vehicle may also be performed. [Explanation of symbols]

[0047] 1:Thermal analysis device 10: Busbar 23: Calculation section 24: Thermal analysis department h1: Heat transfer coefficient D: Length L:Representative head W:Width X: Extending direction

Claims

1. a calculation step of calculating a heat transfer coefficient of the bus bar; a thermal analysis step of performing a thermal analysis of the bus bar using the heat transfer coefficient calculated in the calculation step, In the calculation step, when the bus bar is a rectangular parallelepiped and the length in the extension direction in a plan view is longer than the width, the sum of the length in the extension direction and the width is used as the length in the extension direction to calculate the heat transfer coefficient. Thermal analysis method.

2. The bus bar has conductive members connected to both ends in the extension direction. The thermal analysis method according to claim 1 .

3. In the calculation step, a heat transfer coefficient h1 is calculated by the following equation: K C (ΔT / L) where K is a first coefficient that depends on the ambient temperature, C is a second coefficient that depends on the surface shape of the bus bar, ΔT is a difference between the temperature of the bus bar and the ambient temperature, and L is a characteristic length of the bus bar. １／４ When the width is W, the characteristic length is 2 W, and the heat transfer coefficient h is calculated. The thermal analysis method according to claim 1 or 2.

4. the calculating step calculates the heat transfer coefficient of the bus bar that is provided laterally. The thermal analysis method according to claim 1 or 2.

5. a calculation unit for calculating a heat transfer coefficient of the bus bar; a thermal analysis unit that performs a thermal analysis of the bus bar using the heat transfer coefficient calculated by the calculation unit, When the bus bar is a rectangular parallelepiped and the length in the extension direction in a plan view is longer than the width, the calculation unit calculates the heat transfer coefficient by defining the length in the extension direction as the sum of the length in the extension direction and the width. Thermal analysis equipment.

6. A thermal analysis program that causes a computer to execute temperature prediction of a bus bar mounted on a vehicle, a calculation step of calculating a heat transfer coefficient of the bus bar; a thermal analysis step of performing a thermal analysis of the bus bar using the heat transfer coefficient calculated in the calculation step, In the calculation step, when the bus bar is a rectangular parallelepiped and the length in the extension direction in a plan view is longer than the width, the sum of the length in the extension direction and the width is defined as the length in the extension direction to calculate the heat transfer coefficient. Thermal analysis program.

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