JP2775410B2 - Thermoelectric module - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoelectric power generation module using a thermoelectric conversion element.

[0002]

2. Description of the Related Art Two types of p-type and n-type thermoelectric conversion elements (hereinafter simply referred to as thermoelectric elements) are electrically connected in series and thermally in parallel, and the temperature difference between the junctions is reduced. When applied, an electromotive force is generated, and when an external load is connected, a current flows and an electrical output can be obtained. The principle of converting thermal energy into electrical energy using a thermoelectric element is already known.

FIG. 7 is a perspective view showing an example of use of a conventional thermoelectric generation module.
The module 1 has a module configuration in which thermoelectric elements (not shown) are two-dimensionally arranged inside and each thermoelectric element is fixed by an electrically insulating flat plate. For this reason, when a high or low temperature fluid 2 is used as a heat source for generating a temperature difference, a flat surface is formed on the outer side surface 4 of the cylindrical fluid path 3, and the fixing member 5 for mounting the module 1 is connected to the screw 6.
It was configured to be tightened and fixed.

Next, the distortion of the flat module 1 due to heat will be described with reference to the side view of FIG.

In the thermoelectric element, it is necessary to provide a temperature difference of several tens to 100 ° C. or more between the thermoelectric elements 11 having a height of about several mm. In principle, thermoelectric element (p, n element pair) 1
Power generation and cooling can be performed if there is a metal electrode part connecting them to each other. However, in order to increase the mechanical strength by firmly fixing the electrodes, usually an insulating high heat conduction from both sides In many cases, such a configuration is adopted that it is sandwiched between substrates (hereinafter simply referred to as substrates) 12 (FIG. 8A). In this case, there is a merit that handling becomes very easy, but on the other hand, when actually used with a difference in temperature, the difference in thermal expansion between the high-temperature side substrate 12A and the low-temperature side substrate 12B causes the entire module 1 8 (b) occurs over the entire range.

The warpage of the module 1 will be described using a simple model in only one dimension as an example.

When a temperature difference ΔT is applied to both ends of the module 1 as shown in FIG. 8A, the high-temperature side substrate 12A undergoes thermal expansion of ΔL = αΔT · L. Where α is the coefficient of thermal expansion of the substrate,
L is the length of the substrate.

Assuming that the temperature of the substrate 12B on the low temperature side is T ₀ and the length L does not change, the substrate 12A on the high temperature side generates a distortion with a radius of curvature ρ as shown in equation (1). Here, d is the distance between both substrates 12A and 12B.

[0009]

(Equation 1) Since the radius of curvature is ρ = | d ² y / dx ² | ⁻¹ , integration as shown in Expression (2) gives

[0010]

(Equation 2) Is obtained. Here, C and D are constants. boundary condition,
From x = 0 → y = 0, x = L / 2 → dy / dx = 0 Finally, the shapes of both substrates 12A and 12B are as shown in Expression (3).

[0011]

(Equation 3) It turns out that it becomes. Assuming that the displacement amount of the substrate in the y direction at x = L / 2 (center) is δ, as shown in Expression (4),

[0012]

(Equation 4) It can be seen that when the displacement is small, a displacement proportional to the temperature difference can be obtained.

When the module 1 is actually used for the purpose of power generation and cooling, it is necessary to closely contact the heat source and the module 1 to reduce the thermal resistance, and the distortion as expressed by the equation (4) is required. When this occurs, the efficiency is greatly reduced.

From the above, when the module 1 is actually used, it is common knowledge that a considerably large (〜１０10 kg / cm ² ) pressure is applied from the outside by tightening with a screw 6 as shown in FIG. Has become. However, this can fully take advantage of the inherent advantages of thermoelectric elements, such as an increase in extra cost when constructing a system, and a limited range of application due to a larger structure compared to the case where only the module 1 is used. It is a cause that cannot be exhibited.

[0015]

By the way, in the structure of the conventional flat plate type module 1, as shown in FIG. 8 (b), a shear stress inevitably occurs in the module 1 in a direction perpendicular to the heat flux. There was a problem in reliability in that the module 1 was warped, sometimes leading to breakage of the module 1.

In order to increase the heat receiving area of the module 1, in a conventional “power generation module” shown in FIG. 9 (Japanese Patent Publication No. 60-84979), one end of a cylindrical body 22 facing a low-temperature fluid 21. A module configuration in which a thermoelectric element 25 is wound and housed between a portion and a cylindrical body 24 facing the high-temperature fluid 23 has been proposed.
The point regarding the internal stress generated in 5 remains unresolved.

Thus, in the conventional module configuration,
Since the fluid path as the heat source and the module 1 are each configured as separate elements, the number of parts is large, and in order to improve the heat exchange between the parts, heat conduction grease,
As shown in FIG. 7, a complicated power generation system configuration is required, such as a fixing member 5 for fastening elements. This is very inconvenient in terms of cost and construction in the case of using a large number of modules, such as collecting unused thermal energy to construct a power generation system, and requires a module with a simpler configuration. I have.

In the conventional flat plate type module 1 as shown in FIG. 8, a difference in thermal expansion occurs in the substrate 12 made of ceramics or the like by giving a temperature difference between both sides, so that electrodes, solder joints, thermoelectric Since a shear stress is applied to each component of the element 11, the module 1
As long as the configuration is adopted, there is no effective means that does not apply shear stress to the thermoelectric element.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and requires a fixing member or the like by integrally forming a thermoelectric power generation module using a high-temperature fluid as a heat source and a fluid path. It is an object of the present invention to obtain a thermoelectric power generation module having a simple configuration.

[0020]

The present invention SUMMARY OF] is a predetermined air gap between the inner tube inside the electrical insulation comprising a fluid path of the hot fluid, and the inner tube in the same axis as the inner pipe and the double cylinder consisting of an outer tube, respectively are continuously formed on the opposite surface of the outer tube and the inner tube is disposed in the electrically insulating but which is formed
Inner and outer electrodes, the inner electrode and the outer electrode
And a plurality of thermoelectric conversion elements that are electrically connected in parallel between the electrodes and generate electric power based on a temperature difference generated between both ends.

The plurality of electrodes and the thermoelectric conversion elements are arranged in a rotationally symmetric manner.

[0022]

In the present invention, when a high-temperature fluid flows through the inner tube of the thermoelectric power generation module, heat is radiated from the outer tube to the surroundings,
Electric power can be taken out by applying a temperature difference to each element. Since the inner tube serves as a fluid path and also serves as a substrate for the thermoelectric element, the heat loss is smaller than in the conventional module, a large temperature difference can be given to the thermoelectric element, and the power generation efficiency is improved. Further, since the inner tube thermally expands and applies a compressive stress to the thermoelectric element, the electrical and thermal contact state is improved. If the compressive stress at this time is designed to be equal to or less than the compressive strength of the thermoelectric element, the problem of element destruction does not occur.

Further, by arranging the electrode and the thermoelectric element in a rotationally symmetrical manner, thermal expansion is transmitted to the thermoelectric element isotropically, so that the shear stress inside the element, which has conventionally caused the module to break, is: This does not occur in the configuration of the thermoelectric generation module of the present invention.

[0024]

【Example】

[Embodiment 1] FIGS. 1 and 2 show a first embodiment of the present invention, which is also a basic configuration diagram of the present invention. FIG.
FIG. 2 is a partially cutaway longitudinal sectional view, and FIG. 2 is shown smaller than FIG. In these figures, reference numeral 31 denotes a thermoelectric power generation module (hereinafter, simply referred to as a module), which includes an inner tube 32 having a high-temperature fluid path inside, and an outer tube 33 for releasing heat of the inner tube 32. The inner tube 32 and the outer tube 33 have the same axial center and a predetermined gap is formed therebetween. Both have high thermal conductivity, have mechanical and thermal strength, and have electrical insulation. It is. Outer peripheral surface 32a of inner tube 32 and outer tube 33
A plurality of electrodes 35 are formed on the inner peripheral surface 33a of the electrode 35. Of these electrodes 35, one surface is provided at an end of the electrode 35 on one surface and the other is provided at an end of the electrode 35 on the other surface. Both sides of the p-type and n-type thermoelectric elements 36 are mechanically and electrically joined with the other surface sandwiched therebetween. The inner tube 32 and the outer tube 33 form a double cylinder 34. Each thermoelectric element 36 is electrically connected in series by an electrode 35, and each thermoelectric element 36
And the electrodes 35 are alternately arranged in a rotationally symmetric manner, and the terminal ends thereof are taken out of the double cylinder 34 as electric output terminals 37. The thermoelectric elements 36 and the electrodes 35 are in close contact with the outer peripheral surface 32a of the inner tube 32 and the inner peripheral surface 33a of the outer tube 33, and transmit heat of the high-temperature fluid 39 flowing through the fluid path 38 inside the inner tube 32 well. Although FIG. 1 shows one cross section of the module 31, such an arrangement of the thermoelectric elements 36 is equivalent to that of the double cylindrical body 3.
4 continue in the longitudinal direction. As shown in FIG. 2, at the longitudinal end of the module 31, the inner tube 32 and the outer tube 33 are mechanically fixed by the support 40, and even if a temperature difference is given to the inner tube 32 and the outer tube 33, , So that no shear stress is applied to the thermoelectric element 36.

In the above, when the thermoelectric elements 36 and the electrodes 35 are arranged in a rotationally symmetrical manner, the thermal expansion is transmitted in the same direction, so that the shear stress that would destroy the module does not work. However, even if it is not necessarily a rotationally symmetric shape, a practically sufficient configuration can be obtained by selecting the dimensions and intervals of the electrodes 35 and the thermoelectric elements 36 so that thermal stress is applied to the double cylinder 34 as evenly as possible. .

At both ends of the module 31, a right-hand screw 41A and a left-hand screw 41B are formed to facilitate the attaching and detaching operation when the module 31 is connected to a tube (not shown).

Next, a description will be given of the strain and stress state of the module 31 in which the thermoelectric elements 36 are arranged in the double cylinder 34 according to the present invention, with reference to FIG.

Assuming that the thicknesses of the inner tube 32 and the outer tube 33 are sufficiently smaller than the straight line, when there is an internal pressure p, the circumferential stress of the inner tube 32 is expressed by the following equation (5).

[0029]

(Equation 5) It is represented by First, the inner tube 32 and the outer tube 33 have the same temperature T.
_In this state, the thermoelectric elements 3
No stress is applied to 6 at all.

Since the thermal conductivity of the constituent material (for example, aluminum) of each tube 32, 33 is nearly two orders of magnitude higher than the thermal conductivity of the thermoelectric element 36, the temperature distribution is uniform inside the material of each tube 32, 33. Probably. Assuming that the temperature of the inner tube 32 when a high-temperature fluid (for example, hot water of 100 ° C.) 39 flows through the inner tube 32 is T ₀ + ΔT and the temperature of the outer tube 33 is T ₀ , the inner tube 32 is used for thermal expansion. the radius r ₁ tries to increase. When the inner tube 32 is single, δ ₁ = α ₁ r ₁ ΔT
Only the outer tube 33 expands outward, but is pressed down by the outer tube 33 and the thermoelectric element 36.
2 in the circumferential direction

[0031]

(Equation 6) Compressive stress acts on the thermoelectric element 36 in the diametrical direction as shown in equation (7).

[0032]

(Equation 7) Such compressive stress works. In addition, from the relationship of Expression (5), the inside of the outer tube 33 is

[0033]

(Equation 8) Circumferential tensile stress is applied. Incidentally, E ₁ represents the Young's modulus of the material constituting the inner tube 32.

As apparent from FIGS. 1 and 2, the thermoelectric element 3
6 itself does not receive any shear stress as in the case of the flat module 1 of FIGS. 7 and 8, and the shear breakage of the thermoelectric element 36 is eliminated. Thus, the reliability of the module 31 is significantly improved.
Further, since a compressive force is applied to the thermoelectric element 36, the effect of reducing the thermal resistance between the thermoelectric element and the pipe wall is produced, and FIG.
There is a great advantage in that the external structure for tightening, which is always required in the flat-plate type module 1 as shown in (a) and (b), becomes unnecessary.

[Embodiment 2] FIG. 3 is a cross-sectional view showing a second embodiment of the present invention, which is a specific example created based on the basic structure of FIGS. Indicates the same part. The inner tube 32 and the outer tube 33 are made of a material having a high thermal conductivity, such as aluminum, which has been subjected to insulation coating by anodic oxidation and sealing, and the inner peripheral surface 32 b inside the inner tube 32 and the outer surface outside the outer tube 33 are used. The shape of the outer peripheral surface 33b may be a shape having a large surface area so as to enhance the heat exchange efficiency. In addition to the method of dissipating heat to the surroundings using air, for example, a method of dissipating heat by flowing a cooling liquid may be used. The outer tube 33 does not need to be a single part, but is divided into equal parts and combined.
It may be a method of fixing in a cylindrical shape. The thermoelectric element 36 is 25
This is a bismuth telluride-based thermoelectric semiconductor element having excellent thermoelectric conversion efficiency up to 0 ° C., and a p-type element and an n-type element are shown in FIG.
It is arranged in a rotationally symmetrical form as in. In FIG. 3, p
The type and the n-type are alternately arranged, but if they are electrically connected in series, the p-type and the n-type may be repeatedly arranged in the depth direction (longitudinal direction). These thermoelectric elements 36 are electrically connected in series by electrodes 35 (material: copper, aluminum, etc.) produced by metal bonding, thermal spraying, or the like, and a final electric output is obtained from an electric output terminal 37.

In this way, the arrangement of the thermoelectric elements 36 and the electrodes 35 is made by comparing several rows in the longitudinal direction of the double cylinder 34 according to the required electric output, and the electric output terminals 37 are electrically connected in series. Alternatively, they are connected in parallel to provide an electric output of one module.

In order to suppress distortion due to thermal expansion in the longitudinal direction, the inner tube 32 and the outer tube 33 are firmly fixed at the ends.

At the end, a threaded portion (see right-hand thread 41A and left-hand thread 41B in FIG. 2) is provided to facilitate connection with the fluid path 38 from the heat source so that the thermoelectric power generation module 31 is handled as a replaceable part. Make it easier.

Further, the outer tube 33 is provided with fins 41 for promoting heat radiation in a radial manner.

Embodiment 3 FIG. 4 is a cross-sectional view showing a third embodiment of the present invention. This embodiment differs from the first embodiment in that the thermoelectric elements 36 are all connected in parallel. Therefore, the electrode 3 connected to the thermoelectric element 36
5 is formed continuously instead of being alternately arranged inside and outside as shown in FIG.

It goes without saying that a series-parallel connection in which the first embodiment of FIG. 1 and the third embodiment of FIG. 4 are combined is also possible. The embodiment of FIG. 4 can be embodied as in the second embodiment of FIG.

[Examples of Use] FIGS. 5 and 6 are configuration diagrams showing examples of use of the thermoelectric power generation module 31 of the present invention. FIG. 5 shows a case where the module is used for a boiler, and FIG. The following shows the case.

In FIG. 5, reference numeral 51 denotes a boiler, and a radiator 53 is connected in parallel through a pipe section 52.
The module 31 according to the present invention is connected in series with these radiators 53. Heated water (hot water) or steam of the boiler 51 flows as a high-temperature fluid 39 through the inner tube (shown in FIG. 1) 32 of the module 31.

In FIG. 6, reference numeral 61 denotes a muffler which is attached to an exhaust pipe 62 of an automobile or the like, and a module 31 according to the present invention is attached to a piping portion 63 on the exhaust side of the muffler 61.

Exhaust gas flows as a high-temperature fluid 39 through the inner tube (shown in FIG. 1) 32 of the module 31.

[0046]

As described above, according to the present invention, a predetermined space is provided between an inner pipe having an electrically insulating inside and serving as a fluid path for a high-temperature fluid, and the inner pipe having the same axis as the inner pipe. A double cylindrical body including an electrically insulating outer tube having a void portion formed therein, a plurality of electrodes disposed on opposing surfaces of the inner tube and the outer tube, and both ends connected to these electrodes; Since a plurality of thermoelectric conversion elements that generate electric power at the generated temperature difference are provided, it is possible to prevent breakage of the module due to thermal stress, which is a problem of the conventional module, and to improve reliability. In addition, by integrating the fluid path and the double cylinder forming the module, heat transfer loss can be reduced and power generation efficiency can be improved. Furthermore, the number of parts such as the necessity of external parts for fastening the module is eliminated. This has the advantage that practical applications such as reduction of construction and construction can be facilitated.

Further, since the plurality of electrodes and the thermoelectric exchange element are arranged in a rotationally symmetrical manner, the thermal expansion is transmitted to the thermoelectric element in the same direction, so that there is an advantage that no shear stress is generated inside the thermoelectric conversion element.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a configuration of a first exemplary embodiment of the present invention.

FIG. 2 is a partially broken longitudinal sectional view showing the configuration of the first embodiment of the present invention.

FIG. 3 is a transverse sectional view showing a second embodiment of the present invention.

FIG. 4 is a cross sectional view showing a third embodiment of the present invention.

FIG. 5 is a configuration diagram showing an example of use of the thermoelectric generation module of the present invention.

FIG. 6 is a configuration diagram showing another example of use of the thermoelectric generation module of the present invention.

FIG. 7 is a perspective view showing an example of use of a conventional thermoelectric generation module.

FIG. 8 is an explanatory diagram of distortion of a flat thermoelectric generation module.

FIG. 9 is a partially cutaway side view showing an example of a conventional thermoelectric generation module.

[Explanation of symbols]

 31 thermoelectric power generation module 32 inner tube 32a outer peripheral surface 33 outer tube 33a inner peripheral surface 34 double cylindrical body 35 electrode 36 thermoelectric conversion element 37 electric output terminal 38 fluid path 39 high temperature fluid

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-254082 (JP, A) JP-B-38-7278 (JP, B1) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01L 35/32 H01L 35/30 H02N 11/00

Claims (1)

(57) [Claims] 1. A electrically insulative predetermined gap portion between the inner and the inner tube of the electrical insulation as a fluid path of the hot fluid, and the inner tube in the same axis as the inner pipe is formed and the double cylinder consisting of an outer tube, on the facing surface of the outer tube and the inner tube
The inner electrode and the outer electrode which are formed and disposed continuously, respectively.
A pole and an electrical connection between the inner electrode and the outer electrode.
A thermoelectric power generation module comprising: a plurality of thermoelectric conversion elements connected to a row and configured to generate power by a temperature difference generated at both ends.