JPS58153093A - Heat exchanger used in thermoelectric generator - Google Patents

Abstract

PURPOSE:To reduce the resistance of heat transfer, by pushing out superfluous grease when a heat-conductive grease is applied to the contact surfaces of fins and heat exchanger tubes, and thereby enabling to seal the grease only in the air gaps formed when the fins and the heat exchanger tubes are brought into direct contact with each other. CONSTITUTION:Stay bolts 16 are disposed at proper intervals between flanges of an upper and a lower retainer plates 15, 15 so that a required pressure is applied to the contact surfaces of heat exchanger tubes 9, 10 and sub-module units 8 with fins held between the upper and lower retainer plates 15 by imparting tension to the stay bolts 16 by tightening nuts 17 on the outside of the flanges of the retainer plates 15. Therefore, superfluous grease applied a little excessively to the contact surfaces of the heat exchanger tubes 9, 10 and fins 7 other than the amont of grease required for filling up the air gaps is pushed outwards and they are brought into direct contact with each other, so that the heat conductive grease can be sealed only in the air gaps formed between them in the above state.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat exchanger for a thermoelectric generator for directly converting heat into electricity using thermoelectric elements.

As part of the development of new energy and the development of energy-saving technologies, research and development on the use of heat that has not been used in the past is being undertaken, even though the amount is huge, the difference in temperature is small, such as the difference in energy between the ocean floor and the ocean surface. ``Power generation using thermoelectric elements'' is a technology that directly converts heat with such a low thermal drop into electricity.

A thermoelectric element has thermoelectric performance (ability to convert heat into electricity).
N-type and P-type semiconductors, one side of which is heated and the other side is cooled. The relationship is reversed. Therefore, as shown in FIG. 1, the P-type thermoelectric elements Ii', p2. ...and N-type thermoelectric elements N,,N
2......, all arranged alternately, and the two adjacent thermoelectric elements are arranged on the upper side as Pl and N, , P2 and N2゜.
..., on the lower side, N1 and P2+... are connected in a staggered manner with metal electrode pieces 2, and the electrode pieces on one side are heated and the electrode pieces on the other side are cooled. In other words, n is P type, N
The type of thermoelectric element is electrically connected in series and thermally in parallel, fixed to the submodule, and one side of it is heated.
When the other side is cooled to create a temperature difference between the two sides, an electromotive force is generated between the terminals connected to the thermoelectric elements at both ends. This direct generation of electric power from heat is the result of five basic physical phenomena that are closely related to each other: the Seebeck, Peltier, and Thomson effects, Joule heat generation, and heat conduction.

-For example, bismuth-tellurium heat, which is said to exhibit the highest performance in the ocean temperature range! - Figure 2 (a) shows a row of thermoelectric submodules made up of elements.
, (b) (C) (shown in (f)-J-0 (a) is the top surface of the sub module, (b) is the front surface, (C) is the bottom surface,
(The indicates the side.

The thermoelectric element l has a diameter of 13 ms and a thickness l. 5 disc-shaped, P-type and N-type elements each with 101 pieces each, arranged in 2 rows as shown in the 2-hole element plan, with P-type and N-type elements arranged alternately in each row. The electrodes are arranged so that the P type and the N type are lined up, and the two P and N type pieces arranged in the transverse direction are connected on the upper surface with an electrode piece 2 made of a copper plate. On the bottom surface, as shown in Figure 2 (C), two thermoelectric elements of P type and N type adjacent to each other in the longitudinal direction of the module are connected alternately like a full-wire tile stack, and thermoelectric elements without electrode pieces 2 are attached to the bottom surface of both ends. A terminal plate 3 similar to the electrode handle 2 is connected to the lower surface of the electrode.

The power plate 2 and the terminal plate 3 serve as both electrical conductors and heat transfer surfaces. In order to heat one side of the thermoelectric sub module 4 and cool the other side, for example, as shown in FIG. Used in heat exchangers for generators. Third
In the figure, square tube 5 is a low-temperature pipe filled with cold water, and square tube 6 is a high-temperature vibrator with hot water flowing inside.

The flow directions of cold water and hot water are opposite to each other.
By doing so, when heat exchange is performed between the low temperature pipe 5 and the high temperature vibro through the entire thermoelectric submodule 4, the temperature difference can be made the same everywhere. By sequentially stacking the above-mentioned low temperature pipe 5, submodule 4, and high temperature vibro in multiple stages, it is possible to obtain an arbitrary amount of power generation.

Now, the square heat exchanger tube mentioned above is an extruded aluminum alloy shape, and in the case of a heat exchanger for a large thermoelectric generator on a practical scale, it is necessary to Due to distortion of the tube, the tube may peel off from the adhesive surface of the thermoelectric module, and there is a risk that force will be applied to the adhesive parts, the elements themselves, and the soldered parts in the thermoelectric submodule, causing damage. Furthermore, the corrosion resistance against seawater required for a practical-scale heat exchanger is insufficient.

In order to improve all of these drawbacks, as shown in Figure 4, as a heat transfer structure for a large practical scale heat exchanger, when copper alloy circular tubes are used as high temperature and low temperature heat transfer tubes,
The aluminum extruded shape has a concave surface with an approximately semicircular cross section that closely contacts the outer peripheral surface of the circular tube on one side, and a flat surface that closely contacts the electrode piece 2 of the thermoelectric submodule 4 on the other side. A set of two each of the heat transfer pieces 7 and the thermoelectric submodules 4 which have been subjected to insulating alumite treatment are arranged in the direction of the arm,
(The thermoelectric submodule 4 is shown in one chisel i in Fig. 4)
A sub-module unit 8 with a heat transfer unit is formed by bonding the upper and lower surfaces with a thermally conductive adhesive, and as shown in FIG.
However, a heat exchanger has been proposed in which heat exchanger tubes 9, 10 and units 8 are alternately stacked and held in multiple stages within a frame structure 11 so that the high temperature heat exchanger tubes 10 are in contact with the other concave surface. ing.

According to this configuration, the thin-walled heat exchanger tube 9. Since the lO and the thick heat transfer piece 7 are no longer integrated, they can expand freely, and the above-mentioned drawbacks are improved. However, the heat transfer tube ≦), although the contact between lO and the heat transfer piece 7 is a metal slope,
Since there are dimensional tolerances between them, it is impossible for them to contact each other completely without gaps, but it is inevitable that air gear roughness will occur.3 If an air gap occurs, a large heat transfer resistance will occur.

What is the best way to improve this? A good heating body made of organic or inorganic materials, grease with good conductivity, total heat transfer piece 7 and heat transfer. 19.1
It is better to apply 1 to the joint surface with 0 to fill the gap and reduce heat transfer resistance.

However, no matter how good the thermal conductivity of grease is used, it cannot match the thermal conductivity of metal, so it is best to have metal contact between the heat transfer tube and the heat transfer piece. If a layer of grease is formed entirely between the two, it will have the opposite effect, and the grease will be sealed only in the air gap that inevitably occurs when the two are brought into direct contact. It is desirable to keep it in a cool state.

The heat transfer piece 7 and the heat transfer tubes SR and LO are pressed against each other directly, but it is not possible to obtain the tightening force necessary to push out the excess grease between them with T alone. Not enough.

In the present invention, a thermoelectric element sub-module with a heat transfer piece, a heat transfer tube, and a capillary τ'ri are stacked in multiple stages and held in a lever 714-frame structure, and a thermally conductive glue IJ- It is an object of the present invention to provide a heat exchanger for a thermoelectric generator completely coated with a heat exchanger having a structure such that a pressing force can be obtained between the heat exchanger and the heat exchanger.

Hereinafter, the invention will be described in detail with reference to drawings showing embodiments thereof.

In the heat exchanger of the embodiment shown in FIG. 6, the middle portion is omitted due to space constraints. The electric heating unit sub-module 8 and the heat exchanger tubes 9 and 10 are arranged at appropriate intervals in the longitudinal direction of the heat exchanger, and are provided facing each other with a width of n1 electric heating pieces 7 between them.
They are stacked alternately in multiple stages between pairs of side guides 11, and both sides are held by the side guides 11. The upper and lower parts of the side guides 11 on both sides are vertical holes made of 111 type 1 size, and are installed with the total length of the heat exchanger. It is fixed at 13 and 1'. The upper and lower longitudinal frames 12 are connected to each other by cross beams 14 provided at appropriate intervals, with the left and right longitudinal frames maintaining a predetermined interval.

Side frame 11. A three-dimensional frame structure is formed by the longitudinal frame 2 and the horizontal beams 14.

8- - Stacked between the left and right side frames 11 of frame groove structure; Q, 7v heat transfer submodule unit 8 and heat transfer tubes 9. Half of the top and bottom heat transfer tubes of the IO assembly are supported by only the heat transfer piece 7 at +B, but the flat side, that is, the upper and lower sides of the assembly, is as shown in Figure 7. It is held down by a holding plate 15 constructed by welding a grooved member 15a and a flat plate 15b. This presser plate 15 is provided between the horizontal beams 14, completely avoiding them. The flat plate 15b is a channel member 15a.
It protrudes to both sides to form 7 lunges.

Staples M6 are provided at appropriate intervals between the 7 lunges of the upper and lower presser plates 15, and the staples 16 are tightened by tightening nuts 17' provided on the outside of the 7 lunges of the upper and lower presser plates. By applying tension to the sub-module unit 8 and the heat transfer tube 9 held between the upper and lower presser plates 15. A desired pressing force can be applied to the contact surface of IO. As a result, the heat transfer piece 7 and the heat transfer tube 9. Among the grease that is applied to the contact surface with lO, the excess grease that is not necessary for filling the air gap is pushed out, and the two parts come into direct contact, and the air that is created at this time is pushed out. Thermal conductive grease can be filled only in the gap.

In another embodiment shown in FIGS. 8 and 9, instead of the stay pole 16 of the above embodiment, a short pole 1 is provided between the 7 langes of the holding plate 15 and the 7 horizontal langes of the longitudinal frame 12.
The pond in which the upper and lower holding plates 15 are applied in the direction of drawing them together via the upper and lower poles 15 and the frame structure between them is exactly the same as in the previous embodiment. It is.

As described above, according to the invention, when thermally conductive grease is applied to the contact surface between the heat transfer piece and the heat transfer tube, excess grease is pushed out and grease is applied only to the air gap when the two members are in direct contact. Since it can be encapsulated, the total heat transfer resistance can be significantly reduced, which has a significant effect on the thermoelectric power generation efficiency.

Figure 1 is a diagram explaining the principle of power generation using thermoelectric elements. Figure, 3rd
The figure is a perspective view showing the main parts of a heat exchanger for a laboratory-scale thermoelectric generator, and Figure 4 is a perspective view showing an example of a submodule unit with a heat transfer unit used in a practical-scale heat exchanger. Figure, 5th
The figure is a cross-sectional view showing the main structure of a heat exchanger that uses the sub-module unit and circular heat exchanger tubes shown in Figure 4, and Figure 6 shows the central part of the heat exchanger according to the uninvented embodiment. 7 is a sectional view showing in detail the lower part of the cross section taken along the line ■-■ in FIG. 6, and FIGS. 8 and 9 are side views showing other embodiments of the invention. FIG.

l... Thermoelectric element 2... Electrode piece 4... Sub module 7... Heat transfer piece 8... Sub module unit with heat transfer piece 9... Low temperature heat transfer tube lO... High temperature heat transfer tube 11, 12, 14... Frame structure 15... Pressing plate 16... Stay bolt 18... Bolt 11- Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] N-type and P-type thermoelectric elements are alternately connected electrically in series and thermally in parallel using flat plate electrode pieces, with the entire outside heating surface of the electrode piece on one side and the outside cooling of the electric and pupil pieces on the other side. A heat transfer piece having a concave surface having a shape that closely contacts the outer peripheral surface of a high temperature or low temperature heat transfer tube on the negative side and a flat surface that closely contacts the cooling surface or heating surface of the thermoelectric sub module on the other surface. The two pieces are sandwiched together and their contact surfaces are bonded with a thermally conductive adhesive to form an integrated thermoelectric submodule unit with a heat transfer unit.Construction 1~, one of the concave surfaces on both sides of the unit is equipped with a high temperature heat transfer tube. However, the heat exchanger tubes and the unit are alternately stacked and held in a frame structure in multiple stages so that the low-temperature heat exchanger tube is in contact with the other, and the contact surface between the concave surface of the heat exchanger piece of the unit and the heat exchanger tube is In a heat exchanger for a thermoelectric generator, which is made of a near-gap metal coated with thermally conductive grease, the upper and lower parts of the above-mentioned multi-stage stacked heat transfer sub module unit with heat transfer pieces and an assembly of heat transfer tubes. By holding each mt with a holding plate and pulling the upper and lower holding plates together with an appropriate tension with a stay bolt directly or with a bolt through the frame structure, an appropriate pressing force is applied to the heat transfer piece and the heat transfer tube. A heat exchanger for a thermoelectric generator, characterized in that the heat exchanger is pressed into contact with the thermoelectric generator.