JP4775932B2 - Cushion for heat transfer and thermoelectric conversion module having the same - Google Patents

Description

  The present invention relates to a heat transfer cushion and a thermoelectric conversion module including the same. More specifically, the present invention relates to a heat transfer cushion having both a cushion and a heat transfer function, and a thermoelectric conversion module including the same.

  Examples of heat transport means for transporting heat from a heat generating device to a heat radiation facility include a loop for forcibly circulating a coolant, a heat pipe, a high heat conductive material such as copper and carbon fiber, a heat pump, and a Peltier cooling system. Regardless of which heat transporting means is used, in order to efficiently transport heat from the heat generating device to the heat dissipating equipment, for example, as shown schematically in FIG. 3, the heat generating surface 101a of the heat generating device 101 and the heat generating surface The surface 103a of the heat transport means 103 facing the 101a and the heat receiving surface 102a of the heat radiating equipment 102 and the surface 103a 'of the heat transport means 103 facing the heat receiving surface 102a are reliably brought into contact to reduce the contact thermal resistance. There is a need.

  On the other hand, there is a thermoelectric conversion module that generates power using waste heat from a heat source. For example, as shown in FIG. 4, the thermoelectric conversion module 105 includes a plurality of alternately arranged P-type thermoelectric semiconductors 106a and N-type thermoelectric semiconductors 106b, and adjacent P-type thermoelectric semiconductors 106a and N-type thermoelectric semiconductors 106b. The electrically connected electrode 107, the electrically insulating heat receiving plate 108 laminated on the heat source side of the electrode 107, and the electrically insulating heat insulating plate 108 laminated on the electrode 107 on the opposite side of the heat receiving plate 108 and cooled by the cooling means. And a cooling plate 109.

  In this thermoelectric conversion module 105, it is necessary to give a temperature difference as large as possible on both surfaces of the thermoelectric semiconductor 106 in order to improve the power generation performance. For this reason, conventionally, as shown in FIG. 4A, the assembled thermoelectric conversion module 105 is sandwiched between a heating duct 110 as a heat source and a cooling duct 111 as a cooling means. A method has been adopted in which heat is applied effectively so that the heating duct 110 and the cooling duct 111 are in close contact with the thermoelectric conversion module 105 to reduce contact thermal resistance and effectively conduct heat. In addition, as shown in FIG. 4B, there is a method in which a rubber sheet 112 is interposed between the thermoelectric conversion module 105, the heating duct 110, and the cooling duct 111 to apply pressure from above and below the ducts 110 and 111. Further, as shown in FIG. 4C, a method in which grease 113 having good thermal conductivity is interposed between the thermoelectric conversion module 105, the heating duct 110, and the cooling duct 111 and pressure is applied from above and below the ducts 110 and 111. There is also (refer patent document 1).

JP-A-11-30782

However, the contact thermal resistance when the heat generating surface 101a of the heat generating device 101 shown in FIG. 3 and the surface 103a of the heat transport means 103, and the surface 103a ′ of the heat transport means 103 and the heat receiving surface 102a of the heat dissipating equipment 102 are simply brought into contact is Although it depends on the surface finish state and the pressing force pressing the surfaces, it is generally about 10 ⁻³ to 10 ⁻² (m ² K / W), and a large temperature drop is generated on the contact surface, resulting in thermal resistance. Joining the contact surfaces is the most effective way to reduce the contact thermal resistance, but the relative displacement of both members becomes impossible due to the joining, and the thermal expansion difference due to temperature changes of the members cannot be absorbed, resulting in damage to the members. May lead to

  Further, in the thermoelectric conversion system, in the method of applying pressure from above and below the ducts 110 and 111 sandwiching the thermoelectric conversion module 105 shown in FIG. 4A, if the pressure is weak, the contact thermal resistance increases, and the thermoelectric semiconductor The temperature difference to the main body 106 decreases, and the output decreases. Conversely, when the applied pressure is increased, the output increases, but the thermoelectric semiconductor 106 main body may be destroyed, and adjustment of the applied pressure is extremely difficult. For this reason, in order to reduce the contact thermal resistance, high-precision finishing is performed to improve the flatness and surface roughness of the heat receiving plate 108, the cooling plate 109, the heating duct 110, and the cooling duct 111, which are contact surfaces, and the contact It is necessary to improve the adhesion of the surface. However, even when such high-precision finishing is performed, if a temperature difference occurs, the contact surfaces of the heat receiving plate 108, the cooling plate 109, the heating duct 110, and the cooling duct 111 are deformed into curved surfaces (surfaces). Therefore, it is impossible to always maintain good adhesion. If the contact surface is deformed into a curved surface, a gap is generated between the contact surfaces, and a large contact thermal resistance is generated. In addition, the system shown in FIG. 4A is inferior in terms of practicality because it is necessary to relax the applied pressure in order to avoid thermal stress caused by thermal transients when starting and stopping.

  Further, in the method shown in FIG. 4B, since the flexible rubber sheet 112 relieves thermal stress, fine adjustment of the pressing force is unnecessary, but the thermal conductivity of the rubber sheet 112 is poor, so the thermoelectric semiconductor 106 main body There is a disadvantage that the temperature difference to the temperature is remarkably reduced and the output is greatly reduced. Further, the method shown in FIG. 4C cannot be employed in a practical system because the grease 113 is immediately oxidized and deteriorates or evaporates.

  In particular, since the heating duct 110 causes a large thermal expansion displacement due to a temperature difference during operation and stoppage, a structure that the thermoelectric conversion module 105 can tolerate this displacement is indispensable. Otherwise, the thermoelectric conversion module 105 will be destroyed by repeated stress. The amount of thermal expansion displacement is proportional to the dimension of the heating duct 110 (distance from the fixed position to the free end) and the temperature difference during operation / stop. For example, when the heating duct 110 made of carbon steel having a side of 2 m is fixed at the center, the distance from the fixing position to the free end is 1 m. If this heating duct 110 is 520 ° C. during operation and 20 ° C. during stoppage, the amount of displacement is calculated by the following equation.

<Formula 1>
Displacement = linear expansion coefficient x temperature difference x distance
= 16 × 10 ⁻⁶ × (K ⁻¹ ) × 500 (K) × 1000 (mm) = 8 (mm)

  As described above, the thermoelectric conversion module 105 needs to be firmly pressed and restrained in order to reduce the contact thermal resistance, and at the same time, it is necessary to allow the displacement due to the thermal expansion. At present, there is a demand for measures that can satisfy such conflicting requirements.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a heat transfer cushion capable of effectively conducting heat by reducing contact thermal resistance and easily absorbing thermal expansion displacement, and a thermoelectric conversion module including the same.

In order to achieve such an object, the invention described in claim 1 is provided between two surfaces having a temperature difference, receives pressure from these two surfaces, and transfers heat from the high temperature side surface to the low temperature side surface. This is a thermal cushion, and has a low melting point material that is liquid at the use temperature, and has a flexibility that encapsulates the low melting point material and allows deformation of the liquid low melting point material, and has a melting point that is higher than the use temperature. have a shell made of a material, a carbon sheet is in so that provided on one or both of the hot side of the surface opposite the surface or the cold side of the surface opposite the surface of the shell.

Therefore, the low-melting-point material that exhibits a liquid state at the operating temperature and the flexible shell that encloses the low-melting-point material follow the curved deformation (out-of-plane deformation) of the heat-transfer surface that comes into contact with the two heat-transfer surfaces. The gap between the two is satisfactorily filled, and a gap is prevented from being generated between these two surfaces. Therefore, the heat transfer cushion always maintains good contact with the two opposing surfaces. Moreover, since the liquid low melting point material has high thermal conductivity, the heat resistance of the heat transfer cushion can be kept low, and heat can be efficiently transferred from the high temperature side surface to the low temperature side surface.
Therefore, even when the heat transfer surface is thermally expanded, the heat transfer surface is slid on the sheet material and slid in the surface direction, so that the shearing stress acting on the shell can be released and the shell can be prevented from being broken. Thereby, a large thermal expansion displacement when the heat transfer surface becomes large, for example, a thermal expansion displacement caused by a temperature difference during operation / stop of the large heating duct can be allowed.
The carbon sheet is excellent in slidability, and the thermal resistance at the interface where the carbon sheet is interposed can be reduced to 1/10 or less of the case without this.

The invention of claim 2, in the cushion heat transfer according to claim 1, wherein the shell is assumed to made of a metal foil. In this case, since the shell is made of a metal having high thermal conductivity and is thinly formed, the thermal resistance of the heat transfer cushion can be kept low, and efficiently from the high temperature side surface to the low temperature side surface. Can convey heat.

According to a third aspect of the present invention, in the heat transfer cushion according to the first or second aspect , the low melting point material is a metal having a melting point equal to or lower than the operating temperature. In this case, the low-melting-point material is a metal having high thermal conductivity and is in a molten state at the operating temperature and further increases the thermal conductivity. Therefore, the thermal resistance of the heat transfer cushion can be kept low, and the temperature can be effectively increased. Heat can be transferred from the side surface to the low temperature side surface.

The invention according to claim 4 is the heat transfer cushion according to claim 1 or 2, wherein the low melting point material is obtained by adding fine particles having a higher thermal conductivity to a metal having a melting point lower than the operating temperature. It is supposed to be. Therefore, it is possible to satisfy conditions suitable for a low-melting-point material having a melting point lower than the use temperature and a high thermal conductivity.

According to a fifth aspect of the present invention, in the heat transfer cushion according to any one of the first to fourth aspects, a gap is formed inside the shell in a state where a low melting point material is enclosed. In this case, the volume expansion when the low melting point material is melted can be absorbed, and the shell can be prevented from being damaged by the volume expansion of the low melting point material.

According to a sixth aspect of the present invention, in the heat transfer cushion according to the fifth aspect , the gap is evacuated or an inert atmosphere. In this case, oxidation of the low melting point material can be prevented.

The invention according to claim 7 includes at least a pair of thermoelectric elements, a heat receiving part that receives heat from a heat source, and a heat radiating part that is located on the opposite side of the heat receiving part across the thermoelectric element and is cooled by a refrigerant. In the thermoelectric conversion module which generates electric power by the temperature difference between the heat receiving part and the heat radiating part, heat transfer according to any one of claims 1 to 6 is provided on one or both of the heat receiving part and the heat radiating part. A cushion is provided.

  Therefore, the low-melting-point material that exhibits a liquid state at the operating temperature and the flexible shell that encloses the low-melting-point material follow the curved deformation (out-of-plane deformation) of the heat-transfer surface that comes into contact with the two heat-transfer surfaces. The gap between the two is satisfactorily filled, and a gap is prevented from being generated between these two surfaces. Therefore, the heat transfer cushion always maintains good contact with the two opposing surfaces. Moreover, since the liquid low melting point material has a high thermal conductivity, the heat resistance of the heat transfer cushion can be kept low, and heat can be transferred efficiently. Thereby, the temperature difference which can be loaded to a thermoelectric conversion module can be increased compared with the past, and the generated electric power of a thermoelectric conversion module can be improved. That is, substantial energy conversion efficiency can be improved. Thereby, the power generation unit price of the thermoelectric conversion system can be reduced. In addition, a flexible shell encapsulating a liquid low-melting-point material functions as a cushion, and prevents the thermoelectric element from being destroyed by the applied pressure acting on the thermoelectric conversion module.

Thus, according to the heat transfer cushion according to claim 1, the low melting point material that is liquid at the operating temperature and the flexible shell that encloses the low melting point material are deformed in a curved shape (surface Following the outer deformation), the space between the two heat transfer surfaces is satisfactorily filled, and a gap is prevented from being generated between these two surfaces. Moreover, since the liquid low melting point material has high thermal conductivity, the thermal resistance of the heat transfer cushion can be kept low. Therefore, heat can be efficiently transferred from the high temperature side surface to the low temperature side surface. By using this heat transfer cushion, the requirements for the flatness and surface roughness of the heat transfer surface of the heat generating device, the heat radiating equipment, or the heat transporting means can be relaxed, and two opposing heat transfer surfaces Is not required to be joined directly, so that the member is not damaged by the difference in thermal expansion between the two opposing heat transfer surfaces.
Moreover, according to the heat transfer cushion according to claim 1, even when the heat transfer surface is thermally expanded, the heat transfer surface is slid on the sheet material and slid in the surface direction, so that it tends to act on the shell. Shear stress can be released and the shell can be prevented from breaking. Thereby, a large thermal expansion displacement when the heat transfer surface becomes large, for example, a thermal expansion displacement caused by a temperature difference during operation / stop of the large heating duct can be allowed.
In particular, according to the heat transfer cushion according to claim 1, since the sheet material is a carbon sheet, the carbon sheet is excellent in slidability, and the thermal resistance at the interface where the carbon sheet is interposed is 1 / 10 or less.

Furthermore, according to the heat transfer cushion of claim 2 , since the shell is made of a metal foil, the heat resistance of the heat transfer cushion can be kept lower, and the high temperature side surface can be efficiently moved to the low temperature side. Can convey heat to the surface.

Furthermore, according to the heat transfer cushion according to claim 3 , since the low melting point material is a metal having a melting point equal to or lower than the operating temperature, the heat resistance of the heat transfer cushion can be kept low, and the high temperature side can be efficiently Heat can be transferred from the surface to the low-temperature surface.

Furthermore, according to the heat transfer cushion according to claim 4 , the low melting point material is formed by adding fine particles having a higher thermal conductivity than the metal to a metal having a melting point equal to or lower than the use temperature. It is possible to satisfy conditions suitable for a low melting point material having a lower melting point and a higher thermal conductivity.

Furthermore, according to the heat transfer cushion according to claim 5 , since the gap is formed inside the shell in a state where the low melting point material is enclosed, the volume expansion when the low melting point material is melted can be absorbed. It is possible to prevent the shell from being damaged by the volume expansion of the low melting point material.

Furthermore, according to the heat transfer cushion according to the sixth aspect , since the gap is evacuated or an inert atmosphere, oxidation of the low melting point material can be prevented.

Furthermore, according to the thermoelectric conversion module of claim 7, since the heat transfer cushion is provided, the temperature difference that can be applied to the thermoelectric conversion module can be increased as compared with the conventional case, and the generated power of the thermoelectric conversion module can be improved. That is, substantial energy conversion efficiency can be improved. Thereby, the power generation unit price of the thermoelectric conversion system can be reduced. In addition, a flexible shell encapsulating a liquid low-melting-point material functions as a cushion, and prevents the thermoelectric element from being destroyed by the applied pressure acting on the thermoelectric conversion module.

  Hereinafter, the configuration of the present invention will be described in detail based on embodiments shown in the drawings.

  FIG. 1 shows an embodiment of the heat transfer cushion of the present invention. The heat transfer cushion 1 is interposed between two surfaces S1 and S2 having a temperature difference, receives pressure from the two surfaces S1 and S2, and transfers heat from the high temperature side surface S1 to the low temperature side surface S2. Is.

  For example, in a heat transport means for transporting heat from a heat generating device to a heat radiating facility, when the heat transfer cushion 1 is interposed between the heat generating device and the heat transport means, the heat generating surface of the heat generating device becomes the high temperature side surface S1, The surface of the heat transport means that faces the heat generating surface of the heat generating device is the low temperature surface S2. When the heat transfer cushion 1 is interposed between the heat transporting means and the heat radiating equipment, the heat receiving surface of the heat radiating equipment becomes the low temperature side surface S2, and the surface of the heat transporting means facing the heat receiving face of the heat radiating equipment is It becomes the surface S1 on the high temperature side. In the present embodiment, the surface on the high temperature side is called the heating surface S1, the surface on the low temperature side is called the heat receiving surface S2, the member having the heating surface S1 is called the heat source 2, and the member having the heat receiving surface S2 is the heat receiving member 3. Call. For example, FIG. 1 shows an example in which the heat source 2 is a heating duct and the heat receiving member 3 is a cooling duct.

  The heat transfer cushion 1 includes a low melting point material 4 having a melting point equal to or lower than a use temperature, and a shell 5 that encloses the low melting point material 4 and has flexibility to allow deformation of the liquid low melting point material 4. ing.

  The thickness of the shell 5 can be reduced in order to flexibly follow the curved surface deformation (out-of-plane deformation) due to the temperature difference between the heating surface S1 and the heat receiving surface S2 and from the viewpoint of reducing the thermal resistance. Desirably, for example, about 20 μm to 100 μm (0.1 mm) is preferable. In addition, the material of the shell 5 is selected so that the melting point is higher than the use temperature and the coexistence with the low melting point material 4 to be sealed so that the low melting point material 4 can be reliably sealed at the use temperature. In particular, it is preferable to use a metal material having a high thermal conductivity. For example, when the operating temperature is 250 ° C. or lower, aluminum (Al), copper (Cu) or the like can be used. When the operating temperature is 400 ° C. or lower, stainless steel (SUS304, SUS316) or the like can be used, and the operating temperature is 600 ° C. Below, Inconel etc. can be used. The shell 5 of the present embodiment is formed using, for example, a thin metal foil (metal foil). However, the material of the shell 5 is not limited to metal.

On the other hand, as the low melting point material 4, a material having a melting point lower than the use temperature, a high thermal conductivity, and good coexistence with the shell 5 is selected. Specifically, tin (Sn: melting point 232 ° C.), bismuth (Bi: melting point 271 ° C.), or the like can be used. Here, a low melting point satisfying the condition that the melting point is lower than the working temperature and has a high thermal conductivity by adding fine particles having a higher thermal conductivity than the metal to the metal having a melting point equal to or lower than the working temperature. The material 4 may be obtained. For example, the apparent thermal conductivity can be increased by adding fine particles such as copper (Cu) or tungsten (W) to bismuth. In addition, although not expensive because of its high price, gallium (Ga: melting point: 30 ° C.), indium (In: melting point: 157 ° C.), etc. can be used as the low melting point material 4. However, the low melting point material 4 is not limited to metal. For example, a molten salt (for example, NaNO ₃ / KNO ₃ ) or the like can be used as the low melting point material 4 other than metal.

  The heat transfer cushion 1 is manufactured as follows, for example. For example, when one or both of two thin flat metal foils are subjected to press molding and the peripheral edges of these two metal foils are combined, about 1 to 2 mm between the two metal foils. To create a gap. A low melting point material 4 formed into a sheet having the same thickness as the gap is put into the gap, and the surroundings are sealed by a method such as electron beam welding in a state where the two metal foils are combined. Thereby, the two metal foils function as the shell 5. FIG. 1 shows an example in which only one of the two flat metal foils is press-molded to form a gap for enclosing the low melting point material 4. However, it is not limited to the configuration of FIG. 1, for example, by performing press forming processing on both of the two flat plate-like metal foils, the two metal foils constituting the shell 5 have a vertically symmetrical shape, A gap for enclosing the low melting point material 4 may be formed inside the shell 5. Alternatively, the low melting point material 4 may be a powder (for example, a metal powder exemplified above), and the powdery low melting point material 4 may be filled in a gap formed inside the shell 5.

  Here, it is preferable that a gap 6 is formed inside the shell 5 in a state where the low melting point material 4 is sealed. For example, in the present embodiment, the dimension of the sheet of the low melting point material 4 is made smaller than the plane dimension inside the shell 5 so as to ensure the gap 6 inside the shell 5. By securing the gap 6, the volume expansion when the low melting point material 4 is melted can be absorbed, and the shell 5 can be prevented from being damaged by the volume expansion of the low melting point material 4.

  Further, it is preferable that the gap 6 secured inside the shell 5 is in a vacuum or an inert atmosphere in order to prevent the low melting point material 4 from being oxidized. When the periphery of the shell 5 is sealed by electron beam welding, since the electron beam welding is performed in a vacuum atmosphere, the inside of the shell 5 is naturally evacuated. When the inside of the shell 5 is an inert atmosphere, an inert gas such as argon (Ar) or helium (He) is enclosed in the shell 5 together with the low melting point material 4.

  As the size of the gap between the two metal foils constituting the shell 5, in other words, the thickness h of the heat transfer cushion 1 increases, the deformation of the curved surface due to the temperature difference between the heating surface S1 and the heat receiving surface S2 increases. The heating surface S1 and the heat receiving surface S2 can be satisfactorily filled, but the heat resistance of the heat transfer cushion 1 itself is also increased, so that the necessary minimum is required. preferable. For this reason, the thickness h of the heat transfer cushion 1 is appropriately determined depending on the degree of deformation assumed for the heating surface S1 and the heat receiving surface S2.

  A force for pressing the heat transfer cushion 1 acts on the heating surface S1 and the heat receiving surface S2. For example, the heat receiving member 3 is fixed and the heat source 2 is movable, the heat source 2 is moved to the heat receiving member 3 side, and the pressure P shown in FIG. 1 is applied.

  The low melting point material 4 enclosed in the shell 5 is heated by the heat source 2 and melted, for example. Since the shell 5 has flexibility to allow deformation of the liquid low melting point material 4, the heat transfer cushion 1 is in close contact with the heating surface S1 and the heat receiving surface S2, and the heating surface S1 and the heat receiving surface S2 are curved due to temperature differences. Even if it is deformed, the deformation is flexibly followed to satisfactorily fill the space between the heating surface S1 and the heat receiving surface S2 and prevent a gap from being generated between the heating surface S1 and the heat receiving surface S2. Therefore, the heat transfer cushion 1 always maintains a good contact state with the heating surface S1 and the heat receiving surface S2.

  Here, it is more preferable to provide a sheet material 7 on which the heating surface S1 or the heat receiving surface S2 is in contact with and slidable on one or both of the surface facing the heating surface S1 of the shell 5 or the surface facing the heat receiving surface S2. preferable. In this case, even if the heating surface S1 and the heat receiving surface S2 change greatly due to heat, the heating surface S1 and the heat receiving surface S2 slide and slide on the sheet material 7, so that the thermal expansion displacement is allowed flexibly, and the shell 5 It is possible to prevent the shear stress from acting on the shell 5 and to prevent the shell 5 from being destroyed. The amount of displacement of the heating surface S1 and the heat receiving surface S2 due to the heat is substantially proportional to the size of the heating surface S1 and the heat receiving surface S2 (distance from the restraint point), so that the heating surface S1 and the heat receiving surface S2 are particularly large. It is valid. In general, the heating surface S1 has a larger amount of displacement due to thermal expansion than the heat receiving surface S2. Therefore, in the present embodiment, the sheet material 7 is provided on the surface of the shell 5 that faces the heating surface S1. However, the sheet material 7 may be provided only on the surface of the shell 5 facing the heat receiving surface S2 or on both the heating surface S1 and the two surfaces facing the heat receiving surface S2.

  As the material of the sheet material 7, a material that can reduce the contact thermal resistance and has high slidability (that is, low friction coefficient), heat resistance, and flexibility that can follow the deformation of the shell 5 is selected. More desirably, a material having a high thermal conductivity in the thickness direction is selected. For example, use of a carbon sheet or a polymer sheet is preferable.

  For example, in the present embodiment, an existing carbon sheet is used as the sheet material 7. Here, the sheet material 7 preferably has a high thermal conductivity in the thickness direction, but existing carbon sheets generally have a high thermal conductivity in the plane direction but a low thermal conductivity in the thickness direction. It is. However, it has been clarified by experiments of the present inventor that an effect of greatly reducing the contact thermal resistance can be obtained even with such an existing carbon sheet. The experiment will be described below.

For example, a carbon sheet having a thermal conductivity in the thickness direction of 5 (W / mK) and a thickness of 0.15 (mm) is interposed between two copper blocks to obtain 0.4 (kg / cm ^2). ) And the thermal resistance was measured. In addition, as a comparative example, the two blocks were pressurized at the same pressure as described above without a carbon sheet interposed therebetween, and the thermal resistance was measured. Further, the above measurement was performed while changing the temperature condition. The measurement results are shown in Table 1.

  The value of the thermal resistance when using the carbon sheet shown in Table 1 hardly changes even if the two copper blocks sandwiching the carbon sheet are relatively displaced parallel to the surface of the carbon sheet. Moreover, the thermal resistance at the time of using the carbon sheet shown in Table 1 is the total of the thermal resistance of contact with the copper block on the upper and lower surfaces of the carbon sheet and the thermal resistance of the carbon sheet itself. Among these, the thermal resistance (Rc) of the carbon sheet itself can be obtained by the following calculation.

<Formula 2>
Thermal resistance of carbon sheet itself (Rc) = (thickness) / (thermal conductivity)
= 0.15 × 10 ⁻³ (m) / 5 (W / mK)
= 3 × 10 ⁻⁵ (m ² K / W)

On the other hand, when the total thermal resistance is R, the thermal contact resistance with the copper block on the upper and lower surfaces of the carbon sheet is calculated by (R−Rc) / 2. That is, the contact thermal resistance with the copper block on the upper and lower surfaces of the carbon sheet is 3.5 × 10 ⁻⁵ (m ² K / W) at 150 to 200 ° C., and 3 × 10 ⁻⁵ (m ² at 300 to 400 ° C. K / W).

On the other hand, the contact thermal resistance of the two copper blocks when no carbon sheet is interposed is 100 × 10 ⁻⁵ (m ² K / W) or more. Therefore, the heat resistance can be reduced to 1/10 or less by using the carbon sheet. From the above experimental results, it is considered desirable to apply a pressure of 0.4 (kg / cm ² ) or more to the carbon sheet so that the carbon sheet exhibits the effect of reducing the contact thermal resistance. Incidentally, a carbon sheet having a high thermal conductivity in the thickness direction is being developed, and if such a carbon sheet is employed, the thermal resistance can be further reduced. In general, the carbon sheet can be used up to about 400 ° C. in air and up to about 1100 ° C. in a vacuum and an inert atmosphere.

  The carbon sheet as the sheet material 7 is attached to the surface of the shell 5 facing the heating surface S1 using, for example, a bonding material (for example, an adhesive or a brazing material). For example, in this embodiment, the surface facing the heat receiving surface S2 of the shell 5 is attached to the heat receiving surface S2 using a bonding material (for example, an adhesive or a brazing material). Reference numeral 9 in FIG. 1 indicates a bonding material for bonding the shell 5 and the heat receiving surface S2. In addition, it is preferable to use what has high heat conductivity for the joining material used for joining of the sheet | seat material 7 and the shell 5, and the shell 5 and the heat receiving surface S2.

  According to the heat transfer cushion 1 configured as described above, the liquid low-melting-point material 4 and the flexible shell 5 enclosing the low-melting-point material 4 are deformed in the curved shape of the heating surface S1 and the heat receiving surface S2 ( Following the out-of-plane deformation), the space between the heating surface S1 and the heat receiving surface S2 is satisfactorily filled, and a gap is prevented from being generated between the heating surface S1 and the heat receiving surface S2. Therefore, the heat transfer cushion 1 always maintains a good contact state with the heating surface S1 and the heat receiving surface S2. Moreover, the low melting point material 4 that is a molten metal has a high thermal conductivity, and the shell 5 is made of metal and thinly formed so as to achieve flexibility. Therefore, the thermal resistance of the heat transfer cushion 1 itself is Heat can be efficiently transferred from the heating surface S1 to the heat receiving surface S2. By using this heat transfer cushion 1, the requirements for the flatness and surface roughness of the heating surface S1 and the heat receiving surface S2 can be relaxed, and the heating surface S1 and the heat receiving surface S2 are not directly joined. The heat source 2 and the heat receiving member 3 are not damaged by the difference in thermal expansion between the heat receiving surface S2 and the heat receiving surface S2.

  Furthermore, even when the heating surface S1 side is thermally expanded, the heating surface S1 is slid on the sheet material 7 and slid in the surface direction (the direction of arrow A in FIG. 1), so that the shear stress that tends to act on the shell 5 To prevent the shell 5 from being destroyed. Thereby, the thermal expansion displacement of large heating surface S1, for example, the thermal expansion displacement resulting from the temperature difference during operation / stop of the large heating duct can be allowed. Moreover, the thermal resistance of the interface where the carbon sheet as the sheet material 7 is interposed can be reduced to 1/10 or less of the case without this.

  Next, an embodiment of the thermoelectric conversion module 20 of the present invention will be described. In the following description, the same components as those in the above-described embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. The thermoelectric conversion module 20 includes at least a pair of thermoelectric elements 10, a heat receiving part that receives heat from the heat source 2, and a heat radiating part that is located on the opposite side of the heat receiving part across the thermoelectric element 10 and is cooled by the refrigerant. The power is generated by the temperature difference between the heat receiving part and the heat radiating part, and one or both of the heat receiving part and the heat radiating part are provided with a heat transfer cushion 1.

  For example, the thermoelectric conversion module 20 shown in FIG. 2 receives P-type thermoelectric semiconductors 10a and N-type thermoelectric semiconductors 10b as a plurality of alternately arranged thermoelectric elements 10, and receives adjacent P-type thermoelectric semiconductors 10a and N-type thermoelectric semiconductors 10b. Laminated on the electrode 11 on the opposite side of the heat source 2, the electrode 11 that is electrically connected alternately on the heat source side, and the heat receiving plate 12 that is laminated on the electrode 11 on the heat source 2 side to constitute the heat receiving part And a cooling plate 13 constituting a heat radiating portion. The heat receiving plate 12 and the cooling plate 13 are made of an electrically insulating material such as ceramics.

  However, the thermoelectric conversion module 20 illustrated in FIG. 2 is an example, and is not limited to the illustrated configuration, and a known or new configuration can be appropriately employed. For example, a compliant pad made of a functionally graded material having an electrode layer and an electrical insulating layer in place of both or one of the electrodes 11 on the upper and lower surfaces of the thermoelectric element 10 (P-type thermoelectric semiconductor 10a, N-type thermoelectric semiconductor 10b) ( FGM compliant pad) may be used. The FGM compliant pad is, for example, an electrode layer on the thermoelectric element 10 side and an electrically insulating layer on the opposite side, and the composition of both is continuously changed. For example, it is disclosed in Japanese Patent No. 3056047 and Japanese Patent No. 3482094. You can use things. In addition, you may use the FGM compliant pad which both surfaces consist of an electrode layer and an inside is an electrically insulating layer. When the FGM compliant pad is used, the heat receiving plate 12 or the cooling plate 13 does not need to be made of an electrically insulating material, and may be made of metal. Further, for example, the cooling plate 13 may be omitted and the FGM compliant pad may function as a heat radiating portion. Further, the heat receiving plate 12 may be omitted and the FGM compliant pad may function as the heat receiving portion. Further, the thermoelectric conversion module 20 having the thermoelectric element 10 of the minimum unit may be used, for example, a uni-couple type including one P-type and one N-type thermoelectric semiconductor.

  In the example of FIG. 2, a heat transfer cushion 1 is provided on a heat receiving plate 12 serving as a heat receiving portion. The heat source 2 is, for example, a heating duct, and the heat transfer cushion 1 is interposed between the heat source 2 and the heat receiving plate 12. The sheet material 7 is affixed to the surface facing the heating surface S1 of the shell 5 using, for example, a bonding material (for example, an adhesive). The surface of the shell 5 that faces the heat receiving plate 12 is attached to the heat receiving plate 12 using a bonding material (for example, an adhesive) 9. The surface of the heat receiving plate 12 becomes the heat receiving surface S2. The cooling plate 13 serving as a heat radiating portion of the thermoelectric conversion module 20 is joined to the cooling duct 14 through which the refrigerant passes, using, for example, a joining material (for example, an adhesive or a brazing material) having high thermal conductivity. Reference numeral 15 in FIG. 2 indicates a bonding material for bonding the cooling plate 13 to the cooling duct 14. However, the configuration is not limited to the configuration in which the heat transfer cushion 1 is provided only in the heat receiving portion, and the heat transfer cushion 1 may be provided only in the heat dissipation portion or in both the heat receiving portion and the heat dissipation portion.

  A force that presses the thermoelectric conversion module 20 acts on the heating duct as the heat source 2 and the cooling duct 14 as the cooling means. For example, the cooling duct 14 is fixed and the heat source 2 is movable, the heat source 2 is moved to the cooling duct 14 side, and the pressure P shown in FIG. 2 is applied.

  According to the thermoelectric conversion module 20 configured as described above, the liquid low-melting point material 4 and the flexible shell 5 enclosing the low-melting point material 4 are deformed in a curved shape (out-of-plane) of the heat source 2 and the heat receiving plate 12. Following the deformation), the space between the heat source 2 and the heat receiving plate 12 is satisfactorily filled, and a gap is prevented from being generated between the heat source 2 and the heat receiving plate 12. Therefore, the heat transfer cushion 1 is always kept in good contact with the heat source 2 and the heat receiving plate 12. Moreover, the low melting point material 4 that is a molten metal has a high thermal conductivity, and the shell 5 is made of metal and thinly formed so as to achieve flexibility. Therefore, the thermal resistance of the heat transfer cushion 1 itself is Heat can be transferred from the heat source 2 to the heat receiving plate 12 efficiently. By using this heat transfer cushion 1, the requirements for the flatness and surface roughness of the heating duct as the heat source 2 and the heat receiving plate 12 can be relaxed. In addition, the flexible shell 5 enclosing the liquid low-melting-point material 4 functions as a cushion, and prevents the thermoelectric element 10 from being destroyed by the applied pressure acting on the thermoelectric conversion module 20.

  Furthermore, even when the heating duct as the heat source 2 is thermally expanded, the contact surface (heating surface S1) of the heat source 2 with respect to the thermoelectric conversion module 20 is slid on the sheet material 7 and is in the surface direction (the direction of arrow A in FIG. 2). Therefore, the shearing stress that acts on the shell 5 is released, and the shell 5 is prevented from being broken. Thereby, the thermal expansion displacement resulting from the temperature difference during operation / stop of the heating duct can be allowed. Moreover, the thermal resistance of the interface where the carbon sheet as the sheet material 7 is interposed can be reduced to 1/10 or less of the case without this.

  As described above, the temperature difference that can be applied to the thermoelectric conversion module 20 can be increased to about 1.8 times that of the conventional type. Since the generated electric power of the thermoelectric conversion module 20 is substantially proportional to the square of the temperature difference, even if the same thermoelectric conversion module 20 is used, the generated electric power of the thermoelectric conversion module 20 can be improved about three times by the present invention. That is, the substantial energy conversion efficiency can be improved about three times. Thereby, the power generation unit price of the thermoelectric conversion system can be reduced to about 1/3.

  The above-described embodiment is an example of a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the gist of the present invention. For example, the present invention is effective for application to a thermoelectric conversion system having a large heating / cooling duct, for example, a thermoelectric conversion system using waste heat from various industrial equipment as a heat source. The present invention can be applied to a system that effectively removes heat from accompanying devices, such as transportation such as automobiles, space systems, and various industrial devices. The heat transfer cushion 1 is preferably provided with a sheet material 7, but the sheet material 7 may be omitted when the heating surface S1 and the heat receiving surface S2 are relatively small.

It is a side view which shows one Embodiment of the cushion for heat transfer of this invention, and shows a part in cross section. It is a side view which shows one Embodiment of the thermoelectric conversion module of this invention, and shows a part in cross section. It is a schematic block diagram which shows the heat transport means which conveys heat from the conventional heat-emitting device to a thermal radiation installation. A conventional thermoelectric conversion module is shown, (A) shows a state in which a thermoelectric conversion module is sandwiched between a heating duct and a cooling duct and pressure is applied from above and below the duct, and (B) shows a thermoelectric conversion module, a heating duct, and The case where a rubber sheet is interposed between cooling ducts is shown, and (C) shows the case where grease is interposed between a thermoelectric conversion module, a heating duct and a cooling duct.

Explanation of symbols

S1 High temperature surface (heating surface)
S2 Low temperature side (heat receiving surface)
DESCRIPTION OF SYMBOLS 1 Heat transfer cushion 4 Low melting point material 5 Shell 6 Crevice inside shell 7 Sheet material 10 Thermoelectric element 12 Heat receiving part (heat receiving plate)
13 Heat radiation part (cooling plate)
20 Thermoelectric conversion module

Claims (7)

A low-melting-point cushion that is interposed between two surfaces with a temperature difference and receives heat from these two surfaces and conducts heat from the high-temperature side to the low-temperature side. It possesses a material and a shell made of a material higher melting point than the operating temperature provided with a flexibility that permits deformation of the low melting point material and a liquid encapsulating the low-melting material, the hot side of the shell A heat transfer cushion, characterized in that a carbon sheet is provided on one or both of the surface facing the surface and the surface facing the low temperature side surface . 2. The heat transfer cushion according to claim 1, wherein the shell is made of a metal foil . The cushion for heat transfer according to claim 1 or 2, wherein the low melting point material is a metal having a melting point equal to or lower than a use temperature . The heat transfer cushion according to claim 1 or 2, wherein the low melting point material is obtained by adding fine particles having a higher thermal conductivity to a metal having a melting point equal to or lower than a use temperature . The heat transfer cushion according to any one of claims 1 to 4, wherein a gap is formed inside the shell in a state where the low melting point material is sealed . 6. The heat transfer cushion according to claim 5, wherein the gap is evacuated or inert . At least a pair of thermoelectric elements, a heat receiving part that receives heat from a heat source, and a heat radiating part that is located on the opposite side of the heat receiving part and is cooled by a refrigerant across the thermoelectric element, the heat receiving part and the heat radiating part A thermoelectric conversion module that generates electric power due to a temperature difference between the heat receiving portion and the heat radiating portion is provided with a heat transfer cushion according to any one of claims 1 to 6. Conversion module.

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