WO2005088211A1

WO2005088211A1 - Reaction body of hydrogen storage alloy

Info

Publication number: WO2005088211A1
Application number: PCT/KR2004/000566
Authority: WO
Inventors: Kyu Jung Kim; Kyung Do Kim
Original assignee: Lg Electronics Inc.
Priority date: 2004-03-17
Filing date: 2004-03-17
Publication date: 2005-09-22

Abstract

Reaction body of a hydrogen storage alloy including powder of the hydrogen storage alloy for absorbing or emitting hydrogen, and a body having a shape of a hollow cylinder with an inside diameter and an outside diameter formed by applying a pressure to the powder, thereby having an improved heat conductivity.

Description

REACTIONBODYOF HYDROGEN STORAGEALLOY

Technical Field The present invention relates to hydrogen storage alloys, and more particularly, to a reaction body of a hydrogen storage alloy for reaction with hydrogen. Background Art The hydrogen storage alloy makes reaction with hydrogen, to absorb/emit the hydrogen. The absorption/emission of the hydrogen by the hydrogen storage alloy accompanies reversible transfer of heat. That is, if the hydrogen storage alloy generates heat if the hydrogen storage alloy absorbs the hydrogen, and absorbs heat if the hydrogen storage alloy emits the hydrogen. Therefore, basically, the hydrogen storage alloy is applied to a hydrogen storage apparatus, particularly, recently, applied to room cooling/heating system by using the reversible heat absorption and generation reactions. For an example, such a room cooling/heating system is basically provided with a reaction container filled with the hydrogen storage alloy, and a pipeline connected to the reaction container for flow of the hydrogen. In the system, when hydrogen is introduced into the reaction container through the pipeline, the alloy absorbs the hydrogen, and generates heat. According to this, the reaction container is heated, and at the same time with this, environmental air is also heated. Opposite to this, if hydrogen is discharged from the alloy through the pipeline, the alloy and the reaction container are cooled, to cool the environmental air. Such heated or cooled air may be supplied to a room by a fan. However, the hydrogen storage alloy has the following problems in practical application. First, the hydrogen storage alloy, in a state of powder, has relatively great voids between particles of the alloy while contact areas between the particles are small. Therefore, the hydrogen storage alloy has very low thermal conductivity, with a consequential low heat transfer efficiency. Second, the hydrogen storage alloy expands and contracts repeatedly during absorption/emission of hydrogen, and according to this, the hydrogen storage alloy is micronized, gradually. According to this, the micronized hydrogen storage alloy is liable to infiltrate into an inside of an applied system, to cause faults, as well as drop of thermal conductivity, and air pollution. Third, the powder state of the hydrogen storage alloy is not convenient for use in various systems. The powder state of alloy is very difficult, not only in installation in various systems, but also in replacement. Disclosure of Invention An object of the present invention designed to above problems is to provide a reaction body of a hydrogen storage alloy having a high thermal conductivity. The object of the present invention can be achieved by providing a reaction body of a hydrogen storage alloy including powder of the hydrogen storage alloy for absorbing or emitting hydrogen, and a body having a shape of a hollow cylinder with an inside diameter and an outside diameter formed by applying a pressure to the powder. Preferably, the body is formed by applying a pressure to the powder. The reaction body further includes a plurality of voids. In more detail, preferably, the reaction body has a density equal to, or lower than 90% of density of a solid of the hydrogen storage alloy, or higher than 60% of density of a solid of the hydrogen storage alloy. Most preferably, the reaction body has a density 60 ~ 80% of density of a solid of the hydrogen storage alloy. The reaction body preferably has a length equal to, or smaller than two times of an outside diameter of the reaction body, and the reaction body preferably has an inside diameter greater than 1mm. Preferably, the reaction body further includes chamfer formed at edges thereof, and the chamfer has a width of one tenth of the outside diameter of the reaction body. Preferably, the reaction body further includes a binder material for cohering the powder of the hydrogen storage alloy. The binder material is aluminum, copper, tin, or Teflon, and includes 5% ~ 50% of the binder material. The reaction body enables to heat transfer only with heat conduction with a reaction container, and for this, preferably the reaction body further includes a coated layer in contact both with an inside surface of the reaction body, and an outside circumferential surface of the reaction body. Thus, in the present invention, powder of hydrogen storage alloy is formed into a reaction body having optimal dimensions. According to this, a heat conductivity is improved, and micronization of particles of the powder is suppressed. Brief Description of Drawings The accompanying drawings, which are included to provide a further understanding of the invention, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings; FIG 1 illustrates a perspective view of a reaction body and a reaction container of a hydrogen storage alloy in accordance with a preferred embodiment of the present invention; FIG 2 illustrates a diagram showing detail of a reaction body of a hydrogen storage alloy in accordance with a preferred embodiment of the present invention; and FIG 3 illustrates a partial section showing reaction bodies of the present invention filled in a reaction container.

Best Mode for Carrying Out the Invention Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. In describing the embodiments, identical parts will be given the same names and reference symbols, and repetitive description of which will be omitted. FIG. 1 illustrates a perspective view of a reaction body and a reaction container of a hydrogen storage alloy in accordance with a preferred embodiment of the present invention, and FIG. 2 illustrates a diagram showing detail of a reaction body of a hydrogen storage alloy in accordance with a preferred embodiment of the present invention. As shown, basically the reaction body 100 of the hydrogen storage alloy is formed of powder of the hydrogen storage alloy which is to absorb or emit hydrogen. That is, in the present invention, the powder of the hydrogen storage alloy is solidified to have a predetermined independent shape, i.e., a body for reaction with hydrogen. The solidification makes particles of the hydrogen storage alloy to come closer, to improve, first of all, the thermal conductivity at a single reaction body 100 substantially compared to a same volume of the powder of the hydrogen storage alloy. It is suitable that a particle size of the powder of the hydrogen storage alloy, a raw material of the reaction body 100,

is lOμm ~ lOOμm. If the particle size is greater than lOOμm, cohesive forces between the

particles drop to fail to form a reaction body 100 greater than a certain size. In formation of the reaction body 100, preferably, the powder of the hydrogen storage alloy is pressed at a preset pressure. The application of pressure makes the voids between the particles of the hydrogen storage alloy smaller, and according to this, the thermal conductivity of the particles of the hydrogen storage alloy is also improved, proportionally. In order to make the reaction body 100 to react with hydrogen smoothly, it is required that the hydrogen is diffused into an inner side of the reaction body 100, uniformly. In general, for such hydrogen diffusion, an appropriate voids between the particles of the hydrogen storage alloy is favorable. Therefore, it is required that, though the powder of the hydrogen storage alloy is compressed, the powder forms a porous reaction body 100. That is, it is preferable that the reaction body 100 of the present invention has a plurality of voids. For this, it is required that density of the reaction body 100 is equal to, or lower than 90% of density of a lump of pure hydrogen storage alloy. Such density of the reaction body 100 enables to secure a volume of voids appropriate for diffusion of the hydrogen therein. If the density of the reaction body 100 is below 60% of the density of a solid hydrogen storage alloy, resulting to have an excessive voids and too low strength, the reaction body 100 fails to form its own shape, or liable to break by an external impact. Moreover, under the same reason, the thermal conductivity is also drops substantially. Therefore, it is required that the density of the reaction body 100 is higher than 60% of the density of solid hydrogen storage alloy. Furthermore, for securing optimal voids, it is the most preferable that the density of the reaction body 100 is 60 ~ 80% of the density of the solid hydrogen storage alloy. The reaction body 100 has a form of cylindrical body. That is, a geometrical shape of the reaction body 100 of the present invention can be defined with an outside diameter 'D', an inside diameter Η', and a length 'L'. In view of structure, the hollow cylindrical reaction body 100 has an inside passage 110 owing to the inside diameter 'FT. The inside passage, passed through the reaction body 100, serves as a passage for the hydrogen. Therefore, during the hydrogen passes through the inside passage 110, the hydrogen diffuses into an inner part of the reaction body 100, to accelerate fast and uniform reaction of the hydrogen with the reaction body 100. Moreover, as the reaction body 100 has an inside circumferential surface and an outside circumferential surface owing to its characteristic of shape, the reaction body 100 has maximized areas of a heat transfer surface, and a reaction surface. Therefore, such a hollow cylindrical reaction body 100 has, not only an improved reactivity, but also an improved heat transfer characteristic (heat exchange characteristic). Because the reaction body 100 is formed of powder of hydrogen storage alloy, the greater the size, the more difficult to fabricate, and the higher the relative cost. Particularly, it is more difficult to fabricate a long reaction body 100 while appropriate strength of the reaction body is maintained. Therefore, as shown in FIG. 2, it is preferable that the length 'L' of the reaction body 100 is below two times of the outside diameter 'D' of the reaction body 100. In more detail, if the outside diameter is great substantially, the length 'L' is restricted further. For an example, if the outside diameter 'D' is greater than 10mm, an aspect ratio D/2:L is set to 1 :1 ~ 1:2. That is, the length 'L' is 1/2 ~ 1 times of the outside diameter 'D'. In the meantime, if the outside diameter 'D' is small substantially, the length 'L' may have relatively a great value. If the outside diameter 'D' is below 10mm, the aspect ratio may be set to D/2:L = 1:2 ~ 1 :4, which means that the length 'L' is in a range of 1 ~ 2 times of the outside diameter 'D'. Moreover, if the inside diameter 'FT is too small, the inside passage 110 is liable to be blocked with impurities introduced thereto together with hydrogen. Therefore, it is required that the inside diameter 'FT is greater than 1mm. Moreover, edges of the reaction body 100 may be chamfered 'C\ for easy insertion into the reaction container 200. It is appropriate that a width of the chamfer 'C is one tenth of the outside diameter 'D' of the reaction body.

However, if the outside diameter 'D' is small, a size of the chamfer 'C according to the ratio (i.e., the one tenth of the outside diameter) is negligibly small, to fail to perform an intended function. Therefore, if the outside diameter 'D' of the reaction body 'D' is below 10mm, the width of the chamber 'C has a fixed value in a range of 0.5 ~ 1mm. The binder body 100 may be formed, with a binder material added thereto more.

The binder material, serving to cohere particles of the hydrogen storage alloy, leads to form the reaction body 100, more rigidly. Moreover, as described before, even if the hydrogen storage alloy is micronized due to the expansion and contraction of the hydrogen storage alloy accompanying the absorption/emission of hydrogen, the binder material prevents the micronized particles from breaking away. As the binder material, aluminum, copper, tin, or Teflon may be used. It is suitable that the reaction body 100 contains 5% ~ 50% of the binder material, such that a ratio of the hydrogen storage alloy to the binder material is in a range of 50:50 ~ 95 ~ 5. As described before, since the binder material, a metallic material, serves as a kind of heat conduction body in the reaction body 100, to increase a thermal conductivity of the reaction body 100, substantially. In the meantime, even if the reaction body 100 is inserted in the reaction container 200, uniform contact between the reaction body 100 and the reaction container 200 is not secured. For an example, there is a clearance between the reaction container 200 and the reaction body 100, and finishing allowances of the inside diameter of the reaction container 200 and the outside diameter 'D' of the reaction body 100 are unavoidable. Even if there are such allowances, heat can be transferred between the reaction body 100 and the reaction container 200, actually. However, heat conduction by means of contact is the most efficient for heat transfer between the reaction body 100 and the reaction container 200. Therefore, the reaction body 100 is liable to fail to cool/heat the reaction container 200, effectively. As shown in FIG 3, for solving such a problem in the present invention, the reaction body 100 further includes a coated layer 120a formed on the outside circumferential surface 120. The coated layer 120a, placed between the reaction container 200 and the reaction body 100, is in contact both with an inside surface of the reaction container 200 and the outside circumferential surface 120 of the reaction body 100. Though the coated layer 120a may be formed by various methods, it is preferable that the coated layer 120a is formed by melting a coating material for uniform contact both with the reaction container 200 and the reaction body 110. If the coating material starts to melt at a high temperature, (i.e., has a high melting point), it is liable that voids are formed in the coated layer 120a of the coating material. The voids form a thermal insulating layer, and drop the thermal conductivity of the coated layer. Therefore,

it is preferable that the coating material has a melting point below 800°C. Moreover, since

the reaction container 200 is cooled/heated by the reaction body 100 through the coated layer 120a, it is understandable that the coating material is required to have an excellent thermal conductivity. At first, in formation of such a coated layer 120a, the coating material is placed between the reaction container 200 and the reaction body 100. For an example, the coating material is coated on, or attached to, an inside surface of the reaction container 200, and, thereafter, the reaction body 100 is inserted in the reaction container 200. On the other hand, after the coating material is coated on, or attached to, an outside circumferential surface of the reaction body 100, the reaction body 100 may be inserted in the reaction container 200. Then, the reaction container 200 (together with the coating material and the reaction body 100) is heated up to the melting point of the coating material. If there is oxygen around the reaction body 100 during the heating, an oxidation reaction occurs for produce a stable reactant at the reaction body 100. The reactant makes reactivity of the reaction body 100 with respect to hydrogen poor. Therefore, it is required that the coated layer 120a is formed under an oxygen free environment. The coating material is melt by the heating, and spreads between the reaction container 200 and the reaction body 100 evenly. Then, when the heating stops, the melted coating material solidifies, to form the coated layer 120a in contact both with the reaction container 100 and the reaction body 100 evenly. According to this, the coated layer 120a makes a thermal uniform connection between the reaction body 100 and the reaction container 200, enabling the reaction body 100 to heat/cool the reaction container 200 more effectively with heat conduction only. In the meantime, referring to FIGS. 1 and 3, for enhancing a reaction efficiency, a plurality of the reaction bodies 100 are stacked in one reaction container 200. Serial arrangement of the plurality of the reaction bodies is favorable for enhancing the reaction efficiency. It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents. Industrial Applicability In the present invention, a powder storage alloy is compressed to form into a reaction body of a required shape. Moreover, the reaction body has dimensions designed to be optimized to heat transfer. Therefore, the hydrogen storage alloy of the present invention has a high heat conductivity, and increases a system efficiency having the hydrogen storage alloy applied thereto, too. The contraction/expansion of particles of the hydrogen storage alloy is suppressed in the compressed reaction body, to suppress micronization of the particles. Moreover, even if the particles are micronized, the binder material in the reaction body prevents the micronized particles from breaking away.

According to this, system fault, drop of thermal conductivity, and air pollution are prevented. Furthermore, by having a substantial body, the hydrogen storage alloy can be used, conveniently. That is, the reaction body of the hydrogen storage alloy can be applied to various systems conveniently, and the applied reaction body can also be replaced with new one, conveniently.

Claims

What is Claimed is: 1. A reaction body of a hydrogen storage alloy comprising: powder of the hydrogen storage alloy for absorbing or emitting hydrogen; and a body having a shape of a hollow cylinder with an inside diameter and an outside diameter formed by applying a pressure to the powder.

2. The reaction body as claimed in claim 1, wherein the powder has a particle size

of 10 ~ 100μm.

3. The reaction body as claimed in claim 1, wherein the body is formed by applying a pressure to the powder.

4. The reaction body as claimed in claim 1, further comprising a plurality of voids.

5. The reaction body as claimed in claim 1, wherein the reaction body has a density equal to, or lower than 90% of density of a solid of the hydrogen storage alloy.

6. The reaction body as claimed in claim 1, wherein the reaction body has a density higher than 60% of density of a solid of the hydrogen storage alloy.

7. The reaction body as claimed in claim 1, wherein the reaction body has a density 60 ~ 80% of density of a solid of the hydrogen storage alloy.

8. The reaction body as claimed in claim 1, wherein the reaction body has a length equal to, or smaller than two times of an outside diameter of the reaction body.

9. The reaction body as claimed in claim 1, wherein the outside diameter and the length of the reaction body have a dimensional ratio of D/2:L = 1 :1 ~ 1:2, if the outside diameter is greater than 10mm, where 'D' denotes the outside diameter of the reaction body, and 'L' denotes the length of the reaction body.

10. The reaction body as claimed in claim 1, wherein the outside diameter and the length of the reaction body have a dimensional ratio of D/2:L = 1:2 ~ 1:4, if the outside diameter is smaller than 10mm, where 'D' denotes the outside diameter of the reaction body, and 'L' denotes the length of the reaction body.

11. The reaction body as claimed in claim 1, wherein the reaction body has an inside diameter greater than 1mm.

12. The reaction body as claimed in claim 1, further comprising chamfer formed at edges thereof.

13. The reaction body as claimed in claim 12, wherein the chamfer has a width of one tenth of the outside diameter of the reaction body.

14. The reaction body as claimed in claim 12, wherein the width of the chamfer is 0.5 ~ 1mm if the outside diameter of the reaction body is below 10mm.

15. The reaction body as claimed in claim 1, further comprising a binder material for cohering the powder of the hydrogen storage alloy.

16. The reaction body as claimed in claim 15, wherein the binder material is aluminum, copper, tin, or Teflon.

17. The reaction body as claimed in claim 15, wherein the reaction body includes 5% ~ 50% of binder material.

18. The reaction body as claimed in claim 1, enabling heat transfer only with heat conduction with a reaction container.

19. The reaction body as claimed in claim 1, further comprising a coated layer in contact both with an inside surface of the reaction body, and an outside circumferential surface of the reaction body.

20. The reaction body as claimed in claim 19, wherein the coated layer is formed by melting a coating material.

21. The reaction body as claimed in claim 19, wherein the coated layer is formed under an oxygen free environment.

22. The reaction body as claimed in claim 19, wherein the coated layer is formed by the coating material attached to an inside surface of the reaction container.

23. The reaction body as claimed in claim 19, wherein the coated layer is formed by the coating material attached to an outside circumferential surface of the reaction body.

24. The reaction body as claimed in claim 1, wherein a plurality of the reaction bodies are stacked in the reaction container.

25. The reaction body as claimed in claim 24, wherein the plurality of reaction bodies are arranged in series.