Heat storage device

Abstract

To provide a heat storage device that enables compactification without requiring a complicated mechanism that is costly to manufacture, and can phase-change the entire latent heat storage material quickly to supply large amount of heat after the latent heat storage material enclosed inside a container nucleates.SOLUTION: A heat storage device 10 comprises a heat storage container 11 in which a latent heat storage material 12 is enclosed, heat transfer means to the latent heat storage material 12, a nucleation trigger 13 arranged in the heat storage container 10, and a pressing member 14 for pressing the nucleation trigger 13. The pressing member 14 is arranged slidably in the heat storage container 11. The tip of the pressing member 14 advances from a position where it starts pressing the nucleation trigger 13 to press the nucleation trigger 13, and then retreats to a position farther away from the nucleation trigger 13 than the pressing start position.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a heat storage device. [Background technology]

[0002] Conventionally, various heat storage devices have been proposed that temporarily store thermal energy discharged from a moving body such as a vehicle in a heat storage material and use it when starting the engine in order to promote warm-up, improve fuel efficiency, purify exhaust gas, and improve heating performance.

[0003] For example, Patent Document 1 describes a heat storage device that includes a container filled with a heat storage agent, a nucleation trigger located within the container to nucleate the heat storage agent, an actuator that presses the nucleation trigger, a pressing means that is pushed toward the nucleation trigger by a pressing pin of the actuator and presses the nucleation trigger, and a sealing means provided on the pressing means.

[0004] The heat storage principle of supercooled latent heat storage materials as described in Patent Document 1 is that when the material is heated above its melting point in a solid phase, it transforms into a liquid phase. This liquid phase does not recrystallize even when cooled below the melting point, but continues to remain in a supercooled state, and the heat absorbed during heating is stored as latent heat. When it is desired to utilize this absorbed heat, the heat storage material is nucleated to break down the supercooled state, and recrystallization begins, so that the stored latent heat can be extracted as dissipated heat accompanying the state change from liquid to solid.

[0005] In order to nucleate the liquid-phase latent heat storage material in a supercooled state at any time and cause the material to change into a solid phase, it is known to change the shape of an elastic metal piece in contact with the liquid-phase latent heat storage material, to bring the liquid-phase latent heat storage material into contact with a seed crystal, etc. In order to stably hold the seed crystal, it is known to use a supercooling prevention agent that forcibly changes the phase of the heat storage material to a solid below its melting point. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2007-232332 A Summary of the Invention [Problem to be solved by the invention]

[0007] Considering the installation of latent heat storage materials in vehicles, a large amount of energy is required, and therefore the capacity of the latent heat storage materials becomes large. However, in supercooled latent heat storage materials, when nucleation begins, the phase change propagates and heat is released, but the propagation speed is slow. Therefore, when nucleation is caused from one end of the latent heat storage material sealed in a container, it takes several tens of seconds to reach the opposite end, which causes a problem that heat cannot be released quickly to supply heat when it is needed.

[0008] In view of the above problems, the present invention aims to provide a heat storage device that does not require a complex mechanism that is costly to manufacture, can be made compact, and can quickly supply a large amount of heat by quickly changing the phase of the entire latent heat storage material sealed in a container after nucleation. [Means for solving the problem]

[0009] In order to achieve the above-mentioned object, the heat storage device of the present invention comprises a container in which a latent heat storage material is sealed, a heat transfer means to the latent heat storage material, a nucleation trigger for breaking down the supercooled state of the latent heat storage material, the nucleation trigger being disposed within the latent heat storage material inside the container, and a pressing member for pressing the nucleation trigger, the pressing member being slidably disposed in the container, the tip of the pressing member moving forward from a position where it starts to press the nucleation trigger to press the nucleation trigger, and then moving back to a position farther away from the nucleation trigger than the pressing start position. Effect of the Invention

[0010] According to the present invention, the pressing member is advanced so as to press the nucleation trigger, nucleating the liquid phase latent heat storage material sealed in the container, and then the pressing member is retreated to a position farther away from the nucleation trigger than the starting position of the pressing, so that the solid phase latent heat storage material is drawn up by the retreated pressing member, and the solid phase latent heat storage material thus generated can be used as a seed crystal to solidify the entire latent heat storage material in the container in a short period of time, thereby making it possible to supply a large amount of heat quickly when heat is needed. [Brief description of the drawings]

[0011] [Figure 1] FIG. 2 is a flow diagram for explaining heat storage and heat release in one embodiment of the heat storage device according to the present invention. [Diagram 2] FIG. 4 is a flow diagram for explaining heat storage and heat release in a heat storage device according to a reference example. [Diagram 3] FIG. 4 is a flow diagram for explaining heat storage and heat release in another embodiment of the heat storage device according to the present invention. [Figure 4] 4 is an enlarged cross-sectional perspective view of a flexible member and a guide of the rod shown in FIG. 3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a heat storage device according to the present invention will be described with reference to the accompanying drawings.

[0013] As shown in FIG. 1(a), the heat storage device 10 of this embodiment mainly comprises a heat storage container 11 containing a latent heat storage material 12, a nucleation trigger 13 located on the bottom surface of the heat storage container 11, and a rod 14 for pressing the nucleation trigger 13.

[0014] The heat storage container 11 may be one that can withstand heating and cooling for changing the state of the latent heat storage material 12 between the solid phase and the liquid phase, and may use the material and structure of a container that contains a latent heat storage material in a conventional heat storage device. For example, the material may be stainless steel, aluminum alloy, brass, etc., because of its good thermal conductivity. The structure of the heat storage container 11 is preferably a three-dimensional shape that is long in one direction, and may be, for example, a rectangular shape, a cylindrical shape, or any other three-dimensional shape. In addition, a heat transfer part (not shown), such as a fin for increasing the heat transfer area, is attached to the outer circumferential surface of the heat storage device 10 as a heat transfer means to the latent heat storage material 12. For example, a fin-shaped fin or a corrugated fin may be used as the fin.

[0015] The latent heat storage material 12 is not particularly limited as long as it is a substance that changes into a liquid phase when heated above its melting point in a solid phase, and continues to maintain the liquid phase in a supercooled state even when cooled below its melting point, and can store the heat absorbed during heating as latent heat. For example, calcium chloride hydrate, sodium acetate hydrate, sodium sulfate hydrate, etc. are preferred.

[0016] The nucleation trigger 13 may be, for example, a curved metal plate having elasticity. Such a curved plate can change its shape, such as by inverting, to break the supercooled state of the latent heat storage material 12 in the supercooled state, and initiate a phase change from liquid to solid, that is, nucleation. The nucleation trigger 13 is preferably disposed at one end of the heat storage container 11 in the longitudinal direction, and is disposed, for example, on the bottom surface of the elongated heat storage container 11 as shown in FIG. 1. The nucleation trigger 13 is also preferably disposed at the center of the bottom surface.

[0017] The rod 14 is slidably disposed in the heat storage container 11 so that the tip of the rod 14 can press the nucleation trigger 13 in the heat storage container 11. The base end of the rod 14 opposite to the tip passes through the ceiling of the heat storage container 11 and is connected to a rod drive device (not shown). The rod 14 is slidably supported on the ceiling of the heat storage container 11 via a seal member (not shown) such as an O-ring. The rod 14 is preferably slidably disposed in the longitudinal direction of the heat storage container 11, and is preferably disposed in a central portion extending in the longitudinal direction of the heat storage container 11.

[0018] The rod 14 is configured such that the tip of the rod 14 moves toward the nucleation trigger 13 (hereinafter referred to as "forward") to press the nucleation trigger 13, and the tip of the rod 14 moves toward the opposite side of the nucleation trigger 13 (hereinafter referred to as "rearward") to a position where the tip of the rod 14 is pulled out from the liquid surface of the latent heat storage material 12L. The operation of the rod 14 is controlled by a control circuit (not shown) of the heat storage device 10. The heat storage container 11 is also provided with a temperature sensor (not shown) that measures the temperature of the latent heat storage material 12 in the heat storage container 11, and the temperature sensor and the control circuit are arranged to be able to communicate with each other.

[0019] The heat storage and heat release of the heat storage device 10 having such a configuration will be described with reference to Fig. 1. First, in the heat storage device 10 in a state where heat storage is completed and heat release is not yet performed, as shown in Fig. 1(a), liquid phase latent heat storage material 12L is contained in the heat storage container 11. The tip of the rod 14 is in a position where it starts to press the nucleation trigger 13 (hereinafter referred to as the "pressure start position"). In other words, the tip of the rod 14 is in a position close to or adjacent to the nucleation trigger 13.

[0020] Next, when the heat storage device 10 is to release heat, as shown in Fig. 1(b), the tip of the rod 14 advances toward the nucleation trigger 13 and presses the nucleation trigger 13 with the tip. This causes the shape of the nucleation trigger 13 in the liquid phase latent heat storage material 12L to change, causing nucleation 15 to occur near the nucleation trigger 13.

[0021] As shown in Fig. 1(c), the liquid phase latent heat storage material 12L starts to solidify near the nucleation trigger 13, and the solid phase latent heat storage material 12S is generated and starts to release heat. After pressing the nucleation trigger 13, the tip of the rod 14 immediately retreats toward the opposite side of the nucleation trigger 13 and moves to a position farther away from the nucleation trigger 13 than the pressing start position.

[0022] As the tip of the rod 14 retreats in this manner toward the opposite side to the nucleation trigger 13, a local pressure drop occurs within the liquid phase latent heat storage material 12L, as shown in Figure 1(d), and the solid phase latent heat storage material 12S generated by the nucleation 15 is instantly sucked up, generating rod-shaped solid phase latent heat storage material 12S.

[0023] The tip of the rod 14 retreats to a position where it is pulled out from the liquid surface of the latent heat storage material 12L, as shown in Fig. 1(e). The solidification of the liquid phase latent heat storage material 12L proceeds concentrically with the rod-shaped solid phase latent heat storage material 12S as a seed crystal. Then, as shown in Fig. 1(f), the entire inside of the heat storage container 11 becomes solid phase latent heat storage material 12S, and heat dissipation is completed.

[0024] The heat storage device 10 starts storing heat in the state shown in FIG. 1(f). Since the heat storage container 11 is entirely filled with solid-phase latent heat storage material 12S, the tip of the rod 14 cannot be moved to the pressing start position. When the latent heat storage material 12 is heated to above its melting point and heat storage is completed, the heat storage container 11 is entirely filled with liquid-phase latent heat storage material 12L. When this state is reached, the tip of the rod 14 is advanced and returned to the pressing start position. Next, the heat storage device 10 is cooled below its melting point, and the inside of the heat storage device 10 becomes liquid-phase latent heat storage material 12L in a supercooled state. This again brings the device 10 into the preparation state for heat release shown in FIG. 1(a). In this way, the heat storage device 10 can repeatedly release and store heat.

[0025] The above-mentioned operation of returning the tip of the rod 14 to the pressing start position can be controlled so as to be performed based on the temperature of the latent heat storage material 12 detected by a temperature sensor. For example, the operation may be performed by the temperature sensor detecting that the temperature of the latent heat storage material 12 has risen to a temperature equal to or higher than the melting point, or by the temperature sensor detecting that the temperature of the latent heat storage material 12 has dropped to a temperature equal to or lower than the supercooling temperature. Also, without relying on the temperature sensor, the operation may be performed, for example, immediately before starting heat dissipation when the heat storage device 10 is in a preparation state in which heat dissipation is possible.

[0026] In this embodiment, as described above, the tip of the rod 14 is moved back to a position farther from the nucleation trigger 13 than the pressing start position after pressing the nucleation trigger 13, so that the entire inside of the heat storage container 11 can be solidified in a short time. This can be more clearly understood by explaining the case where the tip of the rod is moved back only to the initial pressing start position after pressing the nucleation trigger, as shown below.

[0027] As shown in FIG. 2(a), the heat storage device 20 has completed heat storage and is in a state before heat dissipation, with the tip of the rod 24 at the pressing start position. Then, in order to dissipate heat from the heat storage device 20, as shown in FIG. 2(b), the tip of the rod 24 is advanced toward the nucleation trigger 23 to press the nucleation trigger 23, and nucleation 25 occurs near the nucleation trigger 23. As shown in FIG. 2(c), the liquid phase latent heat storage material 22L generates a solid phase latent heat storage material 22S near the nucleation trigger 23, and heat dissipation begins. Then, as shown in FIG. 2(d), the liquid phase latent heat storage material 22L in the heat storage container 21 gradually becomes solid from the vicinity of the nucleation trigger 23 on the bottom surface of the heat storage container 21 toward the ceiling surface side on the opposite side.

[0028] Once nucleation begins in the liquid phase latent heat storage material 22L, the phase change propagates and heat is released. However, because the propagation speed is slow, it takes a long time, such as several tens of seconds, for the phase change from the bottom of the heat storage container 21 to reach the liquid surface of the liquid phase latent heat storage material 22L and for all of the heat storage container 21 to become solid phase latent heat storage material 22S, as shown in Figure 2(e). As a result, it is not possible to quickly release heat and supply heat from the heat storage device 20 when it is needed.

[0029] In contrast, in the heat storage device 10 of the present embodiment, the liquid-phase latent heat storage material 12L in the heat storage container 11 does not gradually solidify from the vicinity of the nucleation trigger 13 on the bottom surface of the heat storage container 11 toward the ceiling surface on the opposite side, but solidifies concentrically from the portion extending to the center of the heat storage container 11, so that the entire inside of the heat storage container 11 can be solidified in a short time. Therefore, since a large amount of heat generation starts immediately, it becomes possible to quickly supply heat from the heat storage device 10 when heat is required.

[0030] In Fig. 1, the tip of the rod 14 is retracted until it is pulled out from the liquid surface of the liquid phase latent heat storage material 12L after pressing the nucleation trigger 13, but the present invention is not limited to this. By retracting the tip of the rod 14 to a position farther from the nucleation trigger 13 than the pressing start position, a rod-shaped solid phase latent heat storage material 12S is generated in the heat storage container 11 in part, and then the solid phase is concentrically formed from there, so that the entire inside of the heat storage container 11 can be made solid in a relatively short time. The position to which the tip of the rod 14 is retracted after pressing the nucleation trigger 13 is preferably retracted from the nucleation trigger 13 to a position 25% from the nucleation trigger 13, more preferably retracted from the 50% position, and even more preferably retracted from the 75% position, assuming that the distance from the nucleation trigger 13 to the liquid surface of the liquid phase latent heat storage material 12L is 100%.

[0031] In addition, since rod-shaped solid-phase latent heat storage material 12S is generated in the heat storage container 11 in this manner and the phase change progresses concentrically using this as a seed crystal, it is preferable to place the nucleation trigger 13 in the center of the bottom surface of the heat storage container 11 and the rod 14 along the portion extending to the center of the heat storage container 11, but the present invention is not limited to this, and even if these are not placed in the center, rod-shaped solid-phase latent heat storage material 12S is generated in the heat storage container 11 by the movement of the tip of the rod 14 and the phase change progresses from there, so that the entire inside of the heat storage container 11 can be made solid in a short time compared to the phase change from near the nucleation trigger 23 as shown in Figure 2.

[0032] 1, a rod 14 having a linear shape is slid, and the material of the rod 14 may be one that can withstand heating and cooling for changing the state of the latent heat storage material 12 between the solid phase and the liquid phase, similar to the heat storage container 11, and it is preferable to use stainless steel, aluminum alloy, brass, etc., similar to the heat storage container 11, but the present invention is not limited thereto, and for example, as shown in Fig. 3, a flexible member 30 can be used for the rod 14A. The heat storage device 10A shown in Fig. 3 will be described below. Note that the same components as those of the heat storage device 10 in Fig. 1 are given the same reference numerals, and detailed description thereof will be omitted.

[0033] As shown in FIG. 3(a), the heat storage device 10 mainly includes a heat storage container 11 in which a latent heat storage material 12 is enclosed, a nucleation trigger 13 located on the bottom surface of the heat storage container 11, a rod 14A for pressing the nucleation trigger 13, and a guide 16 for supporting the rod 14A at a position on the surface of the latent heat storage material 12 and in the center of the heat storage container 11. The rod 14A includes a tip portion for pressing the nucleation trigger 13, a base end portion on the opposite side thereof that is connected to a rod drive device (not shown), and an intermediate portion consisting of a flexible member 30 located between them. For example, a rubber material or a synthetic resin material can be used as the flexible member 30. The tip portion and the base end portion may be made of the same material as the rod 14 in FIG. 1.

[0034] The guide 16 supports the sliding movement of the rod 14A, and is slidably engaged with the middle part of the flexible member 30 of the rod 14A as shown in Fig. 4. The rod 14A is also slidably supported on the ceiling part of the heat storage container 11 via a sealing member (not shown) such as an O-ring, but the position does not have to be the center of the ceiling part as shown in Fig. 1, and can be, for example, the end part of the ceiling part as shown in Fig. 3(a).

[0035] According to this configuration, when dissipating heat from the heat storage device 10A, as shown in Fig. 3(b), the rod 14A advances the tip of the rod 14A toward the nucleation trigger 13 while the flexible member 30 is bent by the guide 16, and presses the nucleation trigger 13. This causes the shape of the nucleation trigger 13 to change, nucleating the liquid phase latent heat storage material 12L, and as shown in Fig. 3(c), the solid phase latent heat storage material 12S is generated from the position of the nucleation trigger 13, and heat dissipation begins.

[0036] 3(d), the tip of rod 14A is immediately retracted while the flexible member 30 of rod 14A is bent by guide 16, whereby solid-phase latent heat storage material 12S is instantaneously sucked up and rod-shaped solid-phase latent heat storage material 12S is generated. In this way, since rod 14A does not necessarily need to be pulled up vertically outside heat storage container 11, it is possible to greatly improve the degree of freedom in designing heat storage device 10A, such as the arrangement of the space required to pull up rod 14A and the arrangement of the rod drive device.

[0037] 1 to 3, the heat storage device in which the rod slides vertically has been described, but the present invention is not limited to this, and the same effect can be obtained even if the rod slides horizontally. For example, the heat storage container may be made to extend longitudinally horizontally, a nucleation trigger may be disposed on one inner surface, and a rod may be provided slidably from the inner surface facing it to the nucleation trigger. EXAMPLES

[0038] Examples and comparative examples of the present invention will be described below.

[0039] A 100mL beaker was prepared, a nucleation trigger was placed in the center of the bottom, and then the latent heat storage material was placed in the container. 80g of sodium acetate trihydrate (C2H3NaO2·3H2O) was used as the latent heat storage material. A curved metal disk used in a commercially available recycled warmer was used as the nucleation trigger. The container was then heated to 58°C or higher, which is the melting point of the latent heat storage material, in a hot water bath to liquefy all of the latent heat storage material, and then removed from the hot water and cooled quietly to room temperature. Next, the nucleation trigger was pressed from the upper opening of the container with a straight rod, and the rod was immediately pulled out of the container (Example). The time (seconds) from pressing the nucleation trigger until all of the latent heat storage material in the container solidified was measured, and the change in the state of the latent heat storage material during that time was observed. This test was repeated three times. The test results are shown in Table 1.

[0040] As a comparative example, a test was conducted in the same manner as in the example, except that after the nucleation trigger was pressed with the rod, the rod was not pulled out but was left in the same position. This test was also repeated three times. The test results are shown in Table 1.

[0041] [Table 1]

[0042] In the embodiment, when the rod was rapidly pulled out after the nucleation trigger was pressed, crystals of the latent heat storage material were formed in the center of the container as if they were sucked up by the rod, as shown in Figure 1(d), and then the change to a solid phase simply spread laterally until all of the latent heat storage material in the container solidified. As shown in Table 1, the time it took for the entire material to solidify was 4.7 seconds on average.

[0043] In the comparative example, the rod was left in the container after the nucleation trigger was pressed, so the change of the latent heat storage material to a solid phase proceeded gradually from the nucleation trigger at the bottom toward the liquid surface, as shown in Figure 2(d), until all of the latent heat storage material in the container solidified. As shown in Table 1, the time it took for the entire material to solidify was 8.7 seconds on average.

[0044] Therefore, by pulling the rod out of the container after nucleation, the time from the start of nucleation of the latent heat storage material to the entire solidification was shortened by approximately 46% compared to when the rod was left in the container. Furthermore, an analysis of variance of the test results showed that the effect of pulling up the rod was statistically significant. [Explanation of symbols]

[0045] 10, 10A Heat storage device 11 Heat storage container 12 Latent heat storage material 13 Nuclear Trigger 14, 14A Rod 16 Guide 30 Flexible member

Claims

1. A container in which a latent heat storage material is enclosed; A heat transfer means to the latent heat storage material; A nucleation trigger for breaking down the supercooled state of the latent heat storage material, the nucleation trigger being disposed in the latent heat storage material in the container; a pressing member for pressing the nucleation trigger, the pressing member being slidably disposed on the container, the tip of the pressing member moving forward from a position where pressing of the nucleation trigger is started to start so as to press the nucleation trigger, and then moving backward to a position farther from the nucleation trigger than the pressing start position; A heat storage device comprising:

2. The heat storage device according to claim 1 , wherein the separated position of the tip of the pressing member is a position where the tip of the pressing member is pulled out from the latent heat storage material.

3. The heat storage device according to claim 1 or 2, further comprising a temperature sensor for detecting a temperature of the latent heat storage material, and the tip of the pressing member advances from the separation position to the pressing start position based on the temperature of the latent heat storage material detected by the temperature sensor.

4. The heat storage device according to claim 1 or 2, wherein the pressing member includes a flexible member, and the forward and backward movements of the tip of the pressing member are performed in a state in which the pressing member is curved by the flexible member.

Images