JP2018128190A - Heat storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat storage device capable of making heat storage amount and heat output compatible.SOLUTION: A heat storage device can store heat received from a heat medium, and radiate the stored heat. The heat storage device includes: an internal heat storage material 106 configured to perform heat storage or heat radiation with phase change to a solid phase or liquid phase at a first predetermined temperature; and an external heat storage member 107 configured to perform heat storage or heat radiation with phase change to one solid phase or the other solid phase at a second predetermined temperature, and formed so as to store the internal heat storage member 106 therein. The external heat storage member 107 is a strong correlation electronic system material configured to perform heat storage or heat radiation with phase change to a metal or insulator.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a heat storage device capable of storing and releasing heat.

  2. Description of the Related Art Conventionally, it is known that a solid-liquid phase change material is used to improve a heat storage density in a regenerator that stores waste heat of an internal combustion engine (see, for example, Patent Document 1). Since the heat storage material uses a solid-liquid phase change, the heat storage material is enclosed in a case so as not to flow out during liquefaction, and heat is taken in and out between the cooling water and the heat storage material through the case.

JP-A-6-11286

  However, the case of a regenerator generally does not exhibit a heat storage effect. For this reason, in order to increase the heat storage amount of the heat accumulator, it is necessary to increase the amount of inclusion of the solid-liquid phase change material. However, since the solid-liquid phase change material has a low thermal conductivity, the heat output decreases as the amount of inclusion increases, and the heat output decreases as the heat storage amount increases. For this reason, the heat storage amount and the heat output are in a trade-off relationship, and the degree of freedom in design is extremely reduced.

  In view of the above points, an object of the present invention is to provide a heat storage device capable of achieving both a heat storage amount and a heat output.

  In order to achieve the above object, according to the first aspect of the present invention, there is provided a heat storage device capable of storing heat received from a heat medium and dissipating the stored heat. The internal heat storage material (106) that stores or dissipates heat by changing the phase to the solid phase and the solid phase and the solid phase at the second predetermined temperature to store or dissipate heat and house the internal heat storage material inside And an external heat storage material (107) formed as described above.

  As a result, the external heat storage material constituting the case of the internal heat storage material can also have a heat storage function, and the heat storage amount of the heat storage device can be maintained regardless of the proportion of the internal heat storage material. The ratio can be easily changed. Thereby, the relationship between the heat storage amount of the heat storage device and the heat output can be relaxed to achieve both the heat storage amount and the heat output, and the degree of freedom in designing the heat storage device can be increased.

  In addition, the code | symbol in the bracket | parenthesis of each said means shows the correspondence with the specific means as described in embodiment mentioned later.

It is the figure which showed the structure of the thermal storage system which concerns on 1st Embodiment of this invention. It is the figure which showed the thermal storage unit. It is the figure which showed the thermal storage apparatus. Is a graph showing the phase transition temperature of VO _2. It is a graph which shows the relationship of the heat storage amount, heat output, and weight of the heat storage apparatus of 1st Embodiment. It is a graph which shows the relationship of the heat storage amount of the thermal storage apparatus of a comparative example, a heat output, and a weight. It is the figure which showed the thermal storage apparatus of 2nd Embodiment. It is the figure which showed the thermal storage apparatus of 2nd Embodiment.

(First embodiment)
Hereinafter, a heat storage system according to an embodiment to which the present invention is applied will be described with reference to the drawings. As shown in FIG. 1, the heat storage system includes an energy conversion unit 10, a cold heat generation unit 20, an indoor heat exchanger 30, and a radiator 40.

  The energy conversion unit 10 converts the energy source into another form of energy, and releases heat through the heat medium simultaneously with the energy conversion. For example, in the case of a vehicle, the energy conversion unit 10 is a vehicle engine (that is, an internal combustion engine), a fuel cell, or the like. The energy source is fuel, and other forms of energy are driving force, electric power, and the like. The heat medium is engine coolant, exhaust gas, or the like. In the present embodiment, the energy conversion unit 10 is a vehicle engine, and the heat medium is engine cooling water.

  The exhaust heat released from the energy conversion unit 10 is input to the cold heat generation unit 20 via the first heat medium (engine cooling water) circulating through the first heat medium flow path 11. An exhaust heat recovery device 12 and a heat storage unit 100 are provided in the first heat medium flow path 11. The exhaust heat recovery device 12 is a heat exchanger for recovering the exhaust heat of the energy conversion unit 10. The heat storage unit 100 is a device for storing the exhaust heat of the energy conversion unit 10. The heat storage unit 100 stores the heat of the first heat medium when the first heat medium is higher than a predetermined temperature, and stores the heat stored in the first heat medium when the first heat medium is lower than the predetermined temperature. Dissipate heat. The heat storage unit 100 will be described later in detail.

  The cold heat generation unit 20 is an exhaust heat driving device that operates using the exhaust heat of the energy conversion unit 10 as a drive source. Specifically, the cold heat generation unit 20 generates cold using the exhaust heat of the energy conversion unit 10. As the cold heat generation unit 20, for example, an energy conversion is performed between thermal energy and acoustic energy using an adsorption refrigerator that generates cold by adsorbing and desorbing a working medium to an adsorbent or a thermoacoustic phenomenon. A thermoacoustic refrigerator that generates cold heat can be used.

  The cold generated by the cold heat generator 20 is supplied to the indoor heat exchanger 30 by the second heat medium (for example, cooling water) circulating in the second heat medium flow path 31. The indoor heat exchanger 30 is a device that uses the cold generated by the cold heat generator 20, and the cold generated by the cold generator 20 is used for indoor cooling.

  The exhaust heat generated by the cold heat generation unit 20 is released to the radiator 40 via a third heat medium (for example, cooling water) that circulates through the third heat medium flow path 41. The radiator 40 is a heat exchanger that exchanges heat between the cooling water and the atmosphere, and discharges the exhaust heat of the cold heat generation unit 20 into the atmosphere.

  As shown in FIG. 2, the heat storage unit 100 includes a unit case 101. The unit case 101 is provided with an inlet 102 through which cooling water flows into the unit case 101 and an outlet 103 through which cooling water flows out of the unit case 101. Inside the unit case 101 is an internal flow path 104 through which cooling water can flow.

  A plurality of heat storage devices 105 are accommodated in the internal flow path 104 of the unit case 101. The heat storage device 105 of this embodiment is formed in a plate shape, and a plurality of heat storage devices 105 are arranged in parallel to the internal flow path 104 of the unit case 101. The heat storage device 105 exchanges heat with the first heat medium flowing through the internal flow path 104.

  The heat storage device 105 includes an internal heat storage material 106 and a case member 107. The internal heat storage material 106 is a heat storage material made of a solid-liquid phase change material, and is a material that becomes a solid phase at a temperature lower than the phase transition temperature and becomes a liquid phase at a temperature higher than the phase transition temperature. The phase transition temperature of the internal heat storage material 106 corresponds to the “first predetermined temperature” of the present invention.

  In this embodiment, paraffin is used as the internal heat storage material 106. Paraffin is a lightweight material and contributes to weight reduction of the heat storage device 105. Moreover, the melting point of paraffin can be adjusted according to the molecular weight (that is, the number of carbon atoms).

  Case member 107 is formed so as to accommodate internal heat storage material 106 therein. The case member 107 of the present embodiment has a rectangular parallelepiped shape with a hollow interior.

  The case member 107 of this embodiment is comprised by the external heat storage material which has a heat storage function. As an external heat storage material constituting the case member 107, a solid-solid phase change material that undergoes a phase change in a solid state at a phase transition temperature is used. The phase transition temperature of the case member 107 corresponds to the “second predetermined temperature” of the present invention.

  In the present embodiment, a strongly correlated electron material is used as the solid-solid phase change material constituting the case member 107. A strongly correlated electron material is a substance having a strong effective Coulomb interaction between electrons. The strongly correlated electron material includes a transition metal oxide, an organic π electron complex, and the like, and in this embodiment, a transition metal oxide is used.

  The transition metal oxide has a property of changing from an insulator to a metal when heat energy is applied from the outside. More specifically, in transition metal oxides, the effective Coulomb interaction between the outermost shell electrons of the transition metal atom is strong. Therefore, when the temperature is lower than the metal-insulator transition temperature, the outermost electrons are free to move freely. It will be unable to move (insulator). When the transition metal oxide serving as an insulator is given thermal energy from the outside until the temperature exceeds the metal insulator transition temperature, the outermost shell electrons can move freely (metal). That is, the transition metal oxide becomes an insulator at a temperature lower than the phase transition temperature, and becomes a metal at a temperature higher than the phase transition temperature.

  Thermal energy is stored in the transition metal oxide during this phase transition from insulator to metal. That is, the transition metal oxide can store thermal energy by utilizing the enthalpy change at the time of phase change. The heat stored at this time is stored when, for example, ice (solid) in which water molecules cannot move freely changes to water (liquid) in which water molecules can move freely. Heat corresponding to latent heat of fusion. On the other hand, when the transition metal oxide undergoes a phase transition from a metal to an insulator, the stored heat is dissipated. Therefore, the transition metal oxide can perform heat storage or heat dissipation by changing the phase between a metal and an insulator. This phase change takes place as a solid.

In this embodiment, VO ₂ (vanadium dioxide), which is a transition metal oxide, is used as the case member 107. VO ₂ is a solid-solid phase change material and has a phase transition temperature of 68 ° C.

  As described above, the melting point of the internal heat storage material 106 can be adjusted according to the molecular weight of paraffin, and the melting point of the internal heat storage material 106 is preferably approximately the same as the phase transition temperature of the case member 107. The melting point of the internal heat storage material 106 and the phase transition temperature of the case member 107 are not necessarily the same and may be different. Specifically, the internal heat storage material 106 and the case member 107 need only be capable of phase transition by the first heat medium (in this embodiment, engine cooling water) that transfers heat to and from the heat storage device 105, and the melting point of the internal heat storage material 106 is sufficient. The phase transition temperature of the case member 107 may be within the temperature range of the engine cooling water.

  Moreover, the transition metal oxide used as the case member 107 can adjust the transition temperature (phase transition temperature between the metal and the insulator) by adding an additive. An inorganic material can be employed as the additive.

As shown in FIG. 4, the phase transition temperature can be lowered by adding W (tungsten) to VO ₂ , and the phase transition temperature can be lowered as the addition amount increases. Moreover, the phase transition temperature can be increased by adding Cr (chromium) to VO ₂ , and the phase transition temperature can be increased as the addition amount increases.

  FIG. 5 shows the heat capacity, heat output, and weight of the heat storage device 105 when the proportion of the internal heat storage material 106 in the heat storage device 105 of the present embodiment is changed. FIG. 6 shows the heat capacity, heat output, and weight of a heat storage device using aluminum as the case member 107 as a comparative example.

  When the volume of the internal heat storage material 106 is increased, the volume of the case heat storage material 106 is decreased. When the volume of the internal heat storage material 106 is decreased, the volume of the case heat storage material 106 is increased. Is changing. The volume of the case member 107 is increased or decreased by changing the thickness of the case member 107.

  5 and 6, the proportion of the internal heat storage material 106 in the heat storage device 105 increases from the left to the right. In FIGS. 5 and 6, design target values for the items of heat capacity, heat output, and weight are indicated by broken lines, and ranges satisfying the target values are indicated by oblique lines. In FIG. 5, portions where the ranges exceeding the design target values for each item overlap are indicated by cross lines.

  In the heat storage device 105 of this embodiment shown in FIG. 5, the heat storage amount does not change regardless of the ratio of the internal heat storage material 106. In the heat storage device 105 of the present embodiment, the heat storage device 105 has a constant heat storage amount as a whole by increasing or decreasing the ratio of the case member 107 having a heat storage function in accordance with the increase or decrease of the ratio of the internal heat storage material 106. On the other hand, in the heat storage device of the comparative example shown in FIG. 6, the heat storage amount increases in proportion to the amount of the internal heat storage material 106.

In the heat storage device 105 of the present embodiment shown in FIG. 5, the heat output decreases as the ratio of the internal heat storage material 106 increases. Also in the heat storage device of the comparative example shown in FIG. 6, the heat output decreases as the ratio of the internal heat storage material 106 increases as in the heat storage device 105 of the present embodiment. In addition, since the thermal conductivity of aluminum of the comparative example is higher than that of VO ₂ used in the present embodiment, the thermal output of the thermal storage apparatus of the comparative example is slightly higher than that of the thermal storage apparatus 105 of the present embodiment. Yes.

In the heat storage device 105 of this embodiment shown in FIG. 5, the weight decreases as the proportion of the internal heat storage material 106 increases. Also in the heat storage device of the comparative example shown in FIG. 6, as the heat storage device 105 of this embodiment, the weight decreases as the proportion of the internal heat storage material 106 increases. In addition, since the aluminum of the comparative example is lighter than VO ₂ used in the present embodiment, the heat storage device of the comparative example is slightly lighter than the heat storage device 105 of the present embodiment.

  In the heat storage device of the comparative example shown in FIG. 6, the ranges that exceed the design target values do not overlap in heat capacity and heat output. That is, in the heat storage device of the comparative example, an appropriate design range that satisfies the design target value cannot be obtained.

  On the other hand, in the heat storage device 105 of this embodiment shown in FIG. 5, the heat storage amount exceeds the target value in the entire range regardless of the ratio of the internal heat storage material 106. For this reason, in the heat capacity, the heat output, and the weight, there are portions where ranges that exceed the design target values overlap.

  The heat storage device 105 of the present embodiment described above includes the internal heat storage material 106 made of a solid / liquid phase change material and the case member 107 made of a solid / solid phase change material. For this reason, the case member 107 can also have a heat storage function, the heat storage amount of the heat storage device 105 can be maintained regardless of the ratio of the internal heat storage material 106, and the ratio of the internal heat storage material 106 can be easily changed. It becomes possible to do. Thereby, the relationship between the heat storage amount of the heat storage device 105 and the heat output can be relaxed to achieve both the heat storage amount and the heat output, and the degree of freedom in designing the heat storage device 105 can be increased.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. The second embodiment is different from the first embodiment in the configuration of the case member 107 of the heat storage device 105. Hereinafter, description of the same parts as those in the first embodiment will be omitted, and only different parts will be described.

  As shown in FIG. 7, the case member 107 of the second embodiment is configured as a porous body having a predetermined gap. The gap of the case member 107 only needs to allow the internal heat storage material 106 to permeate. For this reason, the case member 107 should just be a porous body at least the site | part (namely, inner surface) which contact | connects the internal heat storage material 106. FIG. In order to facilitate the penetration of the internal heat storage material 106 into the case member 107, it is desirable that adjacent gaps communicate with each other.

  In the example shown in FIG. 7, the porosity of the case member 107 is the highest at the part in contact with the internal heat storage material 106, and decreases as the distance from the internal heat storage material 106 increases. That is, the porosity decreases from the inside to the outside of the case portion 107. In the case portion 107, it is desirable that the porosity is zero at a portion in contact with the first heat medium (that is, the outer surface).

  The internal heat storage material 106, which is a solid-liquid phase change material, contracts when the phase changes from the liquid phase to the solid phase. At this time, a gap may be formed at the boundary between the internal heat storage material 106 and the case member 107. Such a gap serves as a thermal resistance between the heat medium and the internal heat storage material 106, leading to a decrease in performance of the heat storage device 105.

  On the other hand, in the heat storage device 105 of the second embodiment, the case member 107 is configured as a porous body, so that the liquid-phase internal heat storage material 106 penetrates into the gap of the case member 107. For this reason, when the internal heat storage material 106 changes from a liquid phase to a solid phase, the formation of a gap at the boundary between the internal heat storage material 106 and the case member 107 is suppressed. Thereby, the thermal resistance between the heat medium and the internal heat storage material 106 can be suppressed, and the performance degradation of the heat storage device 105 can be suppressed.

  In order to effectively suppress the formation of a gap at the boundary between the internal heat storage material 106 and the case member 107, it is desirable to make the size of the gap of the case member 107 smaller than the size of the gap.

  Further, the porosity of the case member 107 decreases from the side closer to the internal heat storage material 106 toward the side farther from the side. Thereby, it is possible to effectively suppress the internal heat storage material 106 that has penetrated into the gap of the case member 107 from flowing out of the case member 107.

  Further, as shown in FIG. 8, a sealing layer 108 for sealing the internal heat storage material 106 may be provided on the outer surface of the case member 107. The sealing layer 108 may be provided on the whole or a part of the outer surface of the case member 107. In order to reduce the thermal resistance due to the sealing layer 108 as much as possible, it is desirable to form the sealing layer 108 as thin as possible (for example, about several tens of μm).

  For the sealing layer 108, a metal material such as an aluminum paste or a resin material such as an epoxy resin can be used. When a metal material is used for the sealing layer 108, the thermal resistance due to the sealing layer 108 can be reduced. In the case where a resin material is used for the sealing layer 108, the sealing layer 108 can be easily formed.

  Thus, by providing the sealing layer 108 on the outer surface of the case member 107, it is possible to prevent the internal heat storage material 106 that has penetrated into the gap of the case member 107 from flowing out of the case member 107. Further, the flatness of the outer surface of the case member 107 is improved by the sealing layer 108, and a rectifying effect of the heat medium flowing outside the case member 107 is obtained.

  Further, when the sealing layer 108 is provided on the outer surface of the case member 107, the porosity of the case member 107 does not necessarily have to be decreased from the side closer to the internal heat storage material 106 toward the side farther from the side.

(Other embodiments)
The present invention is not limited to the above-described embodiment, and can be variously modified as follows without departing from the spirit of the present invention. Further, the means disclosed in each of the above embodiments may be appropriately combined within a practicable range.

  (1) In each of the above embodiments, paraffin is used as the internal heat storage material 106 of the heat storage device 105. However, the present invention is not limited to this, and different types of solid-liquid phase change materials may be used. For example, a metal salt hydrate such as sodium acetate hydrate or barium hydroxide hydrate can be used as the solid-liquid phase change material.

  (2) In each of the above embodiments, the heat storage device 105 is configured in a plate shape. However, the present invention is not limited to this, and the heat storage device 105 may have another shape such as a rod shape (for example, a column shape) or a spherical shape. The shape of the heat storage device 105 may be determined based on the heat transfer coefficient and the pressure loss. For example, when the heat storage device 105 is spherical, the filling rate of the heat storage device 105 in the unit case 101 of the heat storage unit 100 can be increased, and the heat transfer rate between the heat medium and the heat storage device 105 is increased. However, the pressure loss of the heat medium increases.

100 heat storage device unit 105 heat storage device 106 internal heat storage material 107 case member (external heat storage material)
108 Sealing layer

Claims (5)

A heat storage device capable of storing heat received from a heat medium and dissipating the stored heat,
An internal heat storage material (106) that stores or dissipates heat by changing phase between a solid phase and a liquid phase at a first predetermined temperature;
A heat storage device comprising: an external heat storage material (107) formed so as to store or dissipate heat by changing phase between a solid phase and a solid phase at a second predetermined temperature, and to house the internal heat storage material therein.   The heat storage device according to claim 1, wherein the external heat storage material is a strongly correlated electronic material that performs heat storage or heat dissipation by changing phase between a metal and an insulator.   The heat storage device according to claim 1, wherein the external heat storage material has a predetermined gap, and the liquid internal heat storage material can penetrate into the gap.   The heat storage device according to claim 3, wherein the external heat storage material has a porosity that decreases from a side closer to the internal heat storage material to a side farther from the side.   The heat storage device according to claim 3 or 4, wherein the external heat storage material is provided with a sealing layer (108) for sealing the internal heat storage material on at least a part of an outer surface.

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