JP2015183973A - Supercooling-type latent heat storage material composition and heat storage system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a supercooling-type latent heat storage material composition which can be kept stably in a supercooling state prior to nucleating motion, has the certainty of nucleation in which crystallization surely proceeds as stimulus is applied by the nucleating motion, certainly returns to a supercooling state via melting of crystal by heating after heat dissipation, and has high reliability for repeated use of this cycle, and to provide a heat storage system using the same.SOLUTION: The supercooling-type latent heat storage material composition contains sodium acetate, water, and alcohol. The alcohol is one or more alcohols selected from the group consisting of ethylene glycol, propylene glycol, 1-propanol, 2-butanol, and 1,3-butanediol. Molecular molar concentrations of sodium acetate, water, and alcohol, in a three-component system composition diagram, are within a polygon area with the points A, B, C, and D as vertices (with an area on a border line included). There is also provided a heat storage system using the supercooling-type latent heat storage material composition.

Description

  The present invention relates to a supercooled latent heat storage material composition and a heat storage system using the same.

  Conventionally, a latent heat storage material that uses latent heat due to phase change (melting) from a solid phase to a liquid phase has been used as a heat storage material. Among the latent heat storage materials, heat storage materials that use the supercooled state retain the liquid phase in the supercooled state even below the freezing point, and phase change (crystallize) from the liquid phase to the solid phase by external stimulation means (nucleation means). It is a material that releases heat. Heat can be extracted from the latent heat storage material at an arbitrary timing by the operation of the nucleation means that crystallizes by applying the external stimulus.

In the use of latent heat storage materials, the supercooled state is stably maintained before the nucleation operation, crystallization proceeds promptly when stimulated by the nucleation operation, and after heat dissipation, the crystal melts by heating, It is desired that the cycle to return to the supercooled state can be used repeatedly.
The minimum temperature before the nucleation operation in which the latent heat storage material can be used is a temperature at which the supercooled state can be stably maintained. For example, −20 ° C. or less is required for automobile applications.

  Also, due to the recent increase in environmental awareness, it is recommended to shorten or cancel the warm-up operation, and prompt operation of each mechanism after the engine is started is required. Accordingly, latent heat storage materials used in automobiles are required to release heat more reliably and quickly after a nucleation operation.

Examples of the latent heat storage material developed so far include sodium acetate trihydrate (see Patent Documents 1 and 2), sodium sulfate decahydrate, and the like.
However, conventional latent heat storage materials are not always sufficient in terms of the stability in the supercooled state, the certainty of crystallization, and the reliability from the viewpoint of repeated use (such as the amount of heat that can be extracted even after repeated use does not vary). It had no characteristics.

JP-A-53-14173 JP-A-4-324092

  Therefore, the present invention maintains the supercooled state with good stability before the nucleation operation, and has the certainty of nucleation that reliably proceeds with crystallization when stimulated by the nucleation operation. An object of the present invention is to provide a supercooled latent heat storage material composition that reliably returns to a supercooled state through melting of crystals by heating and has high reliability for repeated use of this cycle. Furthermore, this invention makes it a subject to provide the system using the supercooling type | mold latent heat storage material composition which shows such an outstanding characteristic and has high reliability with respect to repeated use.

The object of the present invention has been achieved by the following means.
(1) A supercooled latent heat storage material composition containing sodium acetate, water and alcohol,
The alcohol is one or more alcohols selected from the group consisting of ethylene glycol, propylene glycol, 1-propanol, 2-butanol and 1,3-butanediol;
In the ternary composition diagram of sodium acetate, water and alcohol shown in FIG. 1, the molecular molar concentrations of sodium acetate, water and alcohol are point A (sodium acetate 22.6 mol%, water 60.8 mol%, Alcohol 16.6 mol%), point B (26.2 mol% sodium acetate, water 70.9 mol%, alcohol 2.9 mol%), point C (sodium acetate 17.8 mol%, water 81.1 mol%, alcohol 1.1 mol) %) And point D (sodium acetate 14.4 mol%, water 79.1 mol%, alcohol 6.5 mol%) in the polygonal region (including on the boundary line) as the vertex, but supercooled latent heat storage Material composition.
(2) The molecular molar concentration of each of the sodium acetate, the water and the alcohol is point E in the ternary composition diagram (sodium acetate 21.4 mol%, water 64.3 mol%, alcohol 14.3 mol%). , B point (sodium acetate 26.2 mol%, water 70.9 mol%, alcohol 2.9 mol%), F point (sodium acetate 21.5 mol%, water 76.4 mol%, alcohol 2.1 mol%), G point ( Polygonal region having apexes of sodium acetate 18.2 mol%, water 77.7 mol%, alcohol 4.1 mol%) and point H (sodium acetate 18.2 mol%, water 72.7 mol%, alcohol 9.1 mol%) The supercooled latent heat storage material composition according to (1), which is inside (including on the boundary line).
(3) The molecular molar concentration of each of the sodium acetate, the water and the alcohol is the M point in the ternary composition diagram (sodium acetate 22.3 mol%, water 67.0 mol%, alcohol 10.7 mol%). , J point (sodium acetate 24.3 mol%, water 73.0 mol%, alcohol 2.7 mol%), K point (sodium acetate 23.0 mol%, water 74.5 mol%, alcohol 2.5 mol%), L point ( Polygonal region with apexes of sodium acetate 21.4 mol%, water 73.8 mol%, alcohol 4.8 mol%) and point I (sodium acetate 21.4 mol%, water 67.9 mol%, alcohol 10.7 mol%) The supercooling latent heat storage material composition according to (1) or (2), which is inside (including on the boundary line).
(4) The total mass of the sodium acetate and the water forming sodium acetate trihydrate is 70% by mass or more and 95% by mass or less in the total mass of the sodium acetate, the water and the alcohol (1 The supercooled latent heat storage material composition according to any one of (1) to (3).
(5) The thickening agent according to any one of (1) to (4), which contains 0.001 part by mass or more and 5.0 parts by mass or less with respect to 100 parts by mass of the total mass of the water and the alcohol. Supercooled latent heat storage material composition.
(6) The supercooled latent heat storage material composition according to any one of (1) to (5), wherein the supercooled state is maintained at −20 ° C. or lower and crystallized by nucleation operation to generate heat.
(7) The supercooled latent heat storage material composition according to any one of (1) to (6) is crystallized from the supercooled state by nucleation operation to dissipate heat, and after heat radiation, A heat storage system that repeatedly uses the cycle of melting and returning to a supercooled state.

The supercooling type latent heat storage material composition of the present invention has a certainty that the supercooled state is stably maintained before the nucleation operation, and the crystallization surely proceeds when stimulation is given by the nucleation operation, After the heat release, the crystal is surely returned to the supercooled state through melting of the crystal by heating, and the reliability in repeated use of this cycle is high. Furthermore, the heat storage system of the present invention has an excellent operational effect capable of constructing a highly reliable cycle.
The system of the present invention using the supercooled latent heat storage material composition of the present invention is suitable for applications requiring stability in a supercooled state, certainty of crystallization and higher reliability, for example, automotive applications. .

FIG. 1 is a ternary composition diagram of sodium acetate, water and alcohol. FIG. 2 is an enlarged view of the molar concentration region that defines the supercooled latent heat storage material composition of the present invention in the ternary composition diagram of FIG. 1. FIG. 3 is a diagram for explaining an example of the heat storage system of the present invention.

  Hereinafter, the supercooled latent heat storage material composition of the present invention will be described in detail.

<Supercooled latent heat storage material composition>
The supercooled latent heat storage material composition of the present invention contains sodium acetate, water, and one or more alcohols as constituent components.
The supercooling type latent heat storage material composition of the present invention is a supercooling type heat storage material composition that maintains a liquid state without phase change (crystallization) even below the freezing point. The solid-phase crystals are mainly composed of sodium acetate trihydrate crystals in which three molecules of acetate ions and water are surrounded by sodium ions.
Therefore, in the present invention, "contains sodium acetate, water, and one or more alcohols" is not necessarily limited to the case where these components are contained alone, The case where it exists in the form of sodium acetate trihydrate in each composition of a solid phase and a liquid phase is also included.

(Composition of supercooled latent heat storage material composition)
First, the components and composition of the supercooled latent heat storage material composition of the present invention will be described.
As long as the sodium acetate used for this invention satisfy | fills the molar concentration mentioned later, even if it is anhydrous sodium acetate, it is good also considering sodium acetate trihydrate as a raw material.
The water used in the present invention is preferably pure water.

The alcohol used in the present invention is one or more alcohols selected from the group consisting of ethylene glycol, propylene glycol, 1-propanol, 2-butanol and 1,3-butanediol. These alcohols can stabilize the supercooled state of the supercooled latent heat storage material.
Alcohol may be used individually by 1 type and may use 2 or more types together. The preferable combination in the case of using 2 or more types together is not specifically limited, For example, the combination in an Example is mentioned.
In order to maintain a high heat storage density, the alcohol to be added is selected from alcohols having a low molecular weight, that is, the above alcohols, so that the mass concentration of sodium acetate trihydrate satisfies 70% by mass or more of the total. Is preferred. However, if a certain amount or more is added in a single composition, alcohol phase separation from the hydrate tends to occur. Therefore, it is necessary to satisfy the required molecular molar concentration with respect to the hydrate and water by adding a plurality of alcohols. preferable.
In addition, these alcohols have relatively close molecular weights, and since the influence on the heat storage density by the regulation in the molar concentration is small, the composition is defined by the molar concentration.

In the present invention, a known latent heat storage material compatible with a liquid of sodium acetate trihydrate, such as sodium sulfate decahydrate or sodium thiosulfate pentahydrate, may be added.
Moreover, if it is a range which does not impair the target effect of a supercooling type | mold latent heat storage material composition, according to a use etc., you may contain alcohol other than the above, and well-known additives. For example, the viscosity of the supercooled latent heat storage material composition may be adjusted using a thickener, or the viscosity may be increased until it becomes a gel. Metal powder, powder having a liquid mixing effect, and filler may be prepared so as to eliminate temperature unevenness and concentration segregation due to the location of the heat storage material composition liquid and to mix the heat storage material composition homogeneously.

  Although it does not specifically limit as a thickener, For example, a xanthan gum, carboxymethylcellulose, and a xylitol are mentioned. Examples of the additive powder include carbon powder, metal powder such as iron, aluminum and copper, polymer powder, and inorganic powder such as alumina and silica. The content of the thickener is preferably 0.001 to 5.0 parts by mass with respect to the total mass of water and alcohol.

  In the supercooled latent heat storage material composition of the present invention, the molecular molar concentrations of sodium acetate, water and alcohol satisfy the following conditions. That is, the molecular molar concentrations of sodium acetate, water, and alcohol are point A (sodium acetate 22.6 mol) in the ternary composition diagram (also referred to as ternary phase diagram) of sodium acetate, water, and alcohol shown in FIG. %, Water 60.8 mol%, alcohol 16.6 mol%), point B (sodium acetate 26.2 mol%, water 70.9 mol%, alcohol 2.9 mol%), point C (sodium acetate 17.8 mol%, water 81) .1 mol%, alcohol 1.1 mol%) and point D (sodium acetate 14.4 mol%, water 79.1 mol%, alcohol 6.5 mol%) in the area of the polygon ABCD (including the boundary line) .)It is in.

In the present invention, the reason why the respective compositions of sodium acetate, water, and alcohol are defined by molar concentration will be described later.
The said molar concentration is the density | concentration which converted the supercooling type | mold latent heat storage material composition into the composition of each of sodium acetate, water, and alcohol. For example, when 1 mol of sodium acetate trihydrate is contained in the supercooled latent heat storage material composition, the molar concentration is calculated by converting 1 mol of sodium acetate and 3 mol of water.
When the molar concentration is within the range of polygonal ABCD, the supercooled latent heat storage material composition is excellent in terms of stability in the supercooled state, reliable crystallization, and operational reliability of repeated use without phase separation. Combined with special characteristics.

In the supercooled latent heat storage material composition of the present invention, the molecular molar concentrations of sodium acetate, water, and alcohol are E points (sodium acetate 21.4 mol%, water 64.3 mol%, alcohol, alcohol in the ternary composition diagram). 14.3 mol%), B point (26.2 mol% sodium acetate, 70.9 mol% water, 2.9 mol% alcohol), F point (21.5 mol% sodium acetate, 76.4 mol% water, 2.1 mol% alcohol) ), G point (sodium acetate 18.2 mol%, water 77.7 mol%, alcohol 4.1 mol%) and H point (sodium acetate 18.2 mol%, water 72.7 mol%, alcohol 9.1 mol%) It is preferable to be within the region of the polygon EBFGH (including the boundary line).
When the molar concentration is in the region of the polygonal EBFGH, it has more excellent characteristics with respect to stability in a supercooled state, reliable crystallization, and operational reliability of repeated use. Moreover, as will be described later, the thermal responsiveness, phase change stability and heat storage density are also excellent.

More preferably, the molecular molar concentration of each of sodium acetate, water and alcohol is M point (sodium acetate 22.3 mol%, water 67.0 mol%, alcohol 10.7 mol%), J point ( Sodium acetate 24.3 mol%, water 73.0 mol%, alcohol 2.7 mol%), K point (sodium acetate 23.0 mol%, water 74.5 mol%, alcohol 2.5 mol%), L point (sodium acetate 21. 4 mol%, water 73.8 mol%, alcohol 4.8 mol%) and within the region of the polygon MJKLI with the I point (sodium acetate 21.4 mol%, water 67.9 mol%, alcohol 10.7 mol%) as vertices (however, , Including on the boundary line).
When the molar concentration is in the region of the polygon MJKLI, it has particularly excellent characteristics with respect to stability in a supercooled state, reliable crystallization, and operation reliability in repeated use. Furthermore, it is particularly excellent in thermal responsiveness, phase change stability and heat storage density.

  If the molar concentration is in any one of the polygonal regions, the reason for the above effect is not yet clear, but it is estimated as follows.

If the content ratio of sodium acetate is too large beyond the polygonal area, the content ratio of water is relatively reduced, and the sodium acetate anhydride is likely to precipitate from the heat storage material composition liquid. Especially when repeatedly used, anhydrous sodium acetate gradually precipitates, and when the precipitation amount of anhydrous sodium acetate increases and accumulates at the bottom of the container of the heat storage material composition, even in a temperature condition that completely dissolves in the surrounding heat storage material composition liquid, Anhydrous sodium acetate remains without being dissolved. Since anhydrous sodium acetate does not change phase as a heat storage material, the amount of sodium acetate trihydrate is reduced and the amount of heat available is reduced. As a result, the amount of heat that can be extracted gradually decreases, and reliability in repeated use is impaired.
In addition, since anhydrous sodium acetate precipitated from the latent heat storage material composition is deposited so that the interfacial energy with the liquid of the surrounding heat storage material composition becomes small, nucleation of the supercooled heat storage material composition during precipitation It will not be the original. Therefore, the stability of the supercooled state is not greatly impaired, but it causes compositional segregation in the heat storage material composition.

  On the other hand, when the content rate of sodium acetate is too small beyond the polygonal area, the content rate of water becomes relatively large, and the amount of sodium acetate that functions as a latent heat storage material decreases. In addition, when water is phase-separated from the heat storage material composition and volatilizes, it becomes an external factor that impairs the stability of the supercooled state, and reliability may also be impaired.

  Therefore, in this invention, it is preferable that the content rate (molar concentration) of sodium acetate fluctuates according to the content rate of water, and exists in the said polygonal area | region. When the content ratio of sodium acetate is within the polygonal region, phase separation of water can be prevented, and reliability in repeated use is excellent.

If the content ratio (molar concentration) of alcohol with respect to water or sodium acetate is too large beyond the polygonal area, the viscosity of the heat storage material composition tends to be high, and the crystal growth rate after nucleation operation tends to be slow. . Excessive alcohol content is not preferable, and at a content ratio that is high enough to break up the aggregation of water molecules with respect to sodium ions that constitute the center of sodium acetate trihydrate in the heat storage material composition, crystallization occurs even after nucleation operation. The crystal speed slows down so that it does not seem to occur.
On the other hand, if the alcohol content is too small beyond the polygonal area, the supercooled state of the heat storage material composition cannot be stabilized.
Therefore, in the present invention, the alcohol content varies depending on the water and sodium acetate content, but is preferably within the polygonal region, and the alcohol content is within the polygonal region. And the supercooled state can be stabilized, and fast crystallization can be realized. Also, the certainty of nucleation is improved.

  Thus, in the supercooled latent heat storage material composition of the present invention, the composition of the above three components is within the region of the polygon ABCD (however, including on the boundary line), the stability of the supercooled state, crystallization And reliability from the viewpoint of repeated use and reliability.

The relative amount of sodium acetate trihydrate decreases as the sodium acetate and water contained in the heat storage material composition move away from the composition of sodium acetate trihydrate (molar ratio, sodium acetate: water = 1: 3). The amount of heat that can be used is reduced, and is not suitable for applications that require heat extraction in a short time. Moreover, anhydrous sodium acetate is likely to precipitate due to composition segregation.
On the other hand, the composition of sodium acetate and water in each polygonal region shown in FIG. 1 is close to the composition of sodium acetate trihydrate (sodium acetate: water = 1: 3). The supercooled latent heat storage material composition of the invention is excellent in reliability in repeated use, and preferably maintains a high heat storage density.

As described above, the supercooled latent heat storage material composition of the present invention can preferably maintain a high heat storage density and meet the demand for the heat storage density required for the latent heat storage material.
The heat storage material composition of the present invention is not limited to automobile use, but will be described taking automobile use as an example. In other words, in order to improve the fuel efficiency and power consumption of automobiles, it is necessary to reduce the size and weight of automobile-mounted components, and the amount of latent heat storage material to achieve the required amount of heat becomes a problem. Therefore, the amount of heat release (or the amount of heat absorption) with respect to the mass of the supercooling latent heat storage material composition is important for the supercooling latent heat storage material composition, and a reduction in the amount of mounting is required.

  The amount of sodium acetate trihydrate formed, that is, the total mass ratio (theoretical amount) of sodium acetate and water forming sodium acetate trihydrate is not particularly limited. 70 mass% or more and 95 mass% or less are preferable in the total mass of sodium acetate, water, and alcohol.

(Phase change of supercooled latent heat storage material composition)
When the liquid phase of the heat storage material is cooled to below the freezing point, it crystallizes as sodium acetate trihydrate in a state where three molecules of acetate ion and water surround the sodium ion in an equilibrium state.
However, even if the supercooled latent heat storage material composition of the present invention is cooled to below the freezing point, crystallization of sodium acetate trihydrate is suppressed and the supercooled state can be stably maintained. When the supercooled liquid is stimulated by nucleation means, it quickly crystallizes as sodium acetate trihydrate.

  The reason why the supercooled state becomes stable is not necessarily clear, but in the present invention, adjustment of the alcohol content ratio reduces the cohesive force of acetate ions and water molecules on sodium ions, and suppresses nucleation factors. Is possible.

In order to prevent acetate ions and water molecules from approaching sodium ions, it is effective to reduce the polarity of water molecules by containing and coexisting alcohol, and to move around sodium ions and prevent segregation.
On the other hand, in the nucleation operation of the heat storage material composition, the region crystallized by the nucleation operation works as a crystal nucleus for the non-crystalline region that is in contact with it, so that crystallization proceeds continuously, Sodium ions must be adjacent. However, when sodium ions are separated due to the presence / coexistence of alcohol, the contact of the crystallized region with the non-crystallized region is hindered, making it difficult for continuous crystal growth to occur and the crystallization rate to decrease.
As described above, when the heat storage material is divided due to excessive alcohol content / coexistence, crystal growth may not continuously proceed.

On the other hand, preferential nucleation due to external fluctuations can be suppressed by the presence and coexistence of alcohol. Alcohol is present around the continuous phase of the heat storage material, and its boundary energy is supercooled between the container and the air phase. This is considered to be because it is smaller than the boundary energy with the cooling type latent heat storage material.
Further, the continuous phase has an effect of suppressing nucleation because the boundary area is smaller than the divided phase and the total sum of boundary energy is also small.

That is, in the present invention in which the content ratio of alcohol is adjusted, it is considered that the supercooled latent heat storage material in a supercooled state forms a continuous phase and the contribution to activation energy for nucleation is reduced.
Moreover, when it adjusts to the said content rate, the ratio of the sodium acetate trihydrate formed in a supercooling type | mold latent heat storage material composition will increase, and it will become difficult to form anhydrous sodium acetate.

  Also in the form of crystal growth, segregation of the composition as a whole can be suppressed because the crystals are finely dispersed in a dendrite shape instead of a unidirectional crystal.

Therefore, the supercooled latent heat storage material composition of the present invention has a stable supercooled state and is excellent in reliability in repeated use.
According to the above, in the design of forming a continuous phase without phase separation of the supercooled latent heat storage material composition, the composition of sodium acetate, water and alcohol is the molar concentration (mol%) in the total number of moles thereof. It can be seen that the definition in is more preferable than the conventional definition in mass ratio.

  When the supercooled latent heat storage material composition in such a supercooled state is stimulated by a nucleation device or the like, sodium acetate trihydrate quickly crystallizes and heat release occurs. The mechanism of crystallization, the reason for rapid crystallization, and the reason why anhydrous sodium acetate is difficult to precipitate are as described above.

  When the heat associated with crystallization by nucleation of the heat storage material composition is taken out and used, it is necessary to quickly conduct the heat and remove it from the crystallization site to maintain a high crystal growth rate. The form of the continuous phase of the heat storage material composition can secure a path for heat and is effective in maintaining a faster crystal growth rate.

  On the other hand, in the endothermic process accompanying the melting of the crystals of the heat storage material composition by heating, rapid complete melting is required for the crystallization, and the form of the heat storage material composition according to the present invention works effectively.

Due to the refinement of the crystals of sodium acetate trihydrate, the alcohol exists in a form that penetrates into the grain boundaries. In the temperature raising process by heating, melting starts from a low concentration melting point near the crystal grain boundary, and the crystal is divided by melting. The melting of the crystal proceeds more rapidly when the crystal is dissolved in the surrounding liquid than when the liquid nucleus is generated and melted in the crystal. If the liquid is surrounded, the heat conductivity of the liquid is low, so there is a concern that the heat conduction to the crystal is slow and the melting temperature is not reached, but if the viscosity of the surrounding liquid is low, the crystal is denser than the liquid Therefore, it precipitates and complete melting of the crystal occurs rapidly due to heat conduction from the bottom of the container.
If alcohol is dispersed throughout the heat storage material, even if there is some concentration segregation inside the crystal of the heat storage material, the effect of concentration homogenization by diffusion occurs due to sedimentation of the crystal and convection of the liquid portion.

In the temperature rising process, it is preferable to completely melt the supercooled latent heat storage material composition. If any part remains, the supercooled state cannot be maintained in the subsequent temperature lowering process and unexpected crystallization occurs. There is. Therefore, lowering the temperature and shortening the time necessary for complete melting are important in stabilizing the supercooled state.
The supercooled latent heat storage material composition of the present invention also suppresses precipitation of anhydrous sodium acetate, and microcrystallization suppresses coarsening of anhydrous sodium acetate and facilitates remelting of anhydrous sodium acetate.
The fine crystals are also effective against the stagnation phenomenon of melting in which the temperature temporarily decreases due to the endothermic process at the time of melting and the phase boundary between recrystallization and melting occurs. In a fine crystal, when it melts, it interdiffuses with the surrounding lower-concentration liquid, and if the concentration decreases, it becomes difficult to recrystallize, so that the melting proceeds quickly. As described above, the supercooled latent heat storage material composition thus melted is not easily phase-separated and the precipitation of anhydrous sodium acetate is also suppressed.

  As described above, the supercooled latent heat storage material composition of the present invention can store and release heat by repeating the temperature rising process and the temperature rising process.

(Characteristics of supercooled stable latent heat storage material composition)
In the supercooled latent heat storage material composition of the present invention, the supercooled state is stabilized. For example, the supercooled state can be maintained for a day or more at a low temperature of at least −20 ° C., and preferably the supercooled state can be maintained for a day or more even at −25 ° C. Therefore, it can be said that the supercooling type latent heat storage material composition of the present invention is a supercooling stable latent heat storage material composition.
Further, as described above, the supercooled latent heat storage material composition of the present invention has certainty of nucleation in which crystallization proceeds by nucleation operation, and has high reliability in repeated use of heat dissipation and heat absorption processes. Have sex.
Thus, the supercooled latent heat storage material composition of the present invention has supercooled state stability, certainty of crystallization, and high repeatability, and is particularly suitable for automotive applications.

The supercooled latent heat storage material composition of the present invention preferably has the following characteristics.
The supercooled latent heat storage material composition of the present invention is stable in a supercooled state, but when stimulated by a nucleation operation, it quickly crystallizes and generates heat.
The crystallization speed varies depending on the application and use conditions and is not uniquely determined, but is preferably 0.6 mm / s or more, more preferably 1.0 mm / s or more, and further preferably 2.0 mm / s or more.
Since the supercooled latent heat storage material composition has a fast crystallization rate in the above range, it is suitable for automotive applications that require rapid heat dissipation as described above.
The crystallization rate can be measured as follows. That is, a supercooled latent heat storage material composition of 22 mL and a metal plate trigger (a dome-shaped stainless steel plate having cracks) are sealed in a sealed container of 60 mm × 160 mm × 3 mm and left at −10 ° C. The temperature transition of the supercooled latent heat storage material composition is measured with a thermocouple at a plurality of points starting from the trigger, and the time at which the temperature starts to rise is determined as the crystallization start time at each measurement point, and between the distances of 100 mm The crystallization progress time is obtained from the time difference of the crystallization start time, the crystallization progress distance / crystallization progress time is calculated, and this is used as the crystallization speed (mm / s).

The heat storage density is not particularly limited, but is preferably 70 kJ / kg or more, and more preferably 75 kJ / kg or more.
Since the supercooling type latent heat storage material composition has a high heat storage density in the above range, the amount of the supercooling type latent heat storage material composition required to dissipate the necessary amount of heat can be reduced. Therefore, it is suitable for automotive applications that require a reduction in the amount of mounting while maintaining the heat dissipation amount.
The heat storage density can be measured as follows. That is, a sample in which 22 mL of a supercooled latent heat storage material composition and a metal plate trigger are sealed in a 60 mm × 160 mm × 3 mm sealed container used for crystallization rate measurement, and a 25 ° C. water in a water bath that is thermally insulated. The sample is placed in water, nucleating is performed in the water, and the temperature rise of the water temperature is measured by a plurality of thermocouples, for example, twelve. The water tank is shaken so that the water temperature at each measurement point is uniform, and the water temperature is made uniform, and further, the temperature rise value is obtained by the average value of 12 points. The density of water is 1 g / cm ³ , the specific heat is 4.2 J / g · ° C., and the amount of heat received by water is calculated from the mass of water and the temperature rise value for each measurement, and the mass of the supercooled latent heat storage material composition The value divided by is obtained as the heat storage density (kJ / kg).

(Preparation of supercooled stable latent heat storage material composition)
The supercooled latent heat storage material composition of the present invention is prepared by mixing anhydrous sodium acetate, water and alcohol at a ratio satisfying the molar concentration.
In preparing the supercooled latent heat storage material composition, sodium acetate trihydrate may be used as part or all of anhydrous sodium acetate. When sodium acetate trihydrate is used, each molar concentration is set separately for sodium acetate and water.

(Use of supercooled stable latent heat storage material composition)
The supercooled latent heat storage material composition of the present invention can be used as a heat source for a heat storage system. In particular, it has characteristics suitable for automobile use in any of the stability in the supercooled state, the certainty of crystallization and the reliability in repeated use, and is suitable for the automobile application.
Examples of automotive applications include a heat storage system that stores heat by exhaust heat from an engine, a motor, cooling water, etc., and uses it for heating at the time of starting, heating a battery, and lubricating oil.

<Heat storage device>
An example of an apparatus constituting the heat storage system of the present invention includes a supercooling latent heat storage material composition of the present invention, a container for storing the supercooling latent heat storage material composition, and a generator that crystallizes by applying an external stimulus. And a nuclear device.
The supercooled latent heat storage material composition of the present invention is as described above.

(container)
A container will not be specifically limited if the supercooling type | mold latent heat storage material composition of this invention can be accommodated. For example, a pack surrounded by an exterior material made of a flexible laminate film, a metal container such as stainless steel, and the like can be given.
Since the volume of the supercooled latent heat storage material composition of the present invention expands and contracts by heating and cooling, when using a metal container, a space is provided in the container to prevent damage to the container due to expansion and contraction. Is preferred.

(Nucleation device)
The nucleation device is not particularly limited as long as nucleation can be caused by stimulation in the supercooled latent heat storage material composition of the present invention, and may be provided inside the container or outside the container.
The nucleation apparatus used in the present invention is preferably an apparatus that enables nucleation operation up to at least −20 ° C.
Examples of the nucleation means of the nucleation apparatus include a method of bringing a seed crystal into contact with the supercooled latent heat storage material composition, a method of applying an impact using a metal rod or a metal plate, for example, inverting the metal plate. A method of applying an impact, a method of pressing a metal rod), a method of applying a voltage, a method of local cooling, and a method of applying vibration. Among these, it is preferable to use a method in which a seed crystal is brought into contact or a method using a metal plate, and it is particularly preferable to use a metal plate.

(Other configurations)
The nucleation device of the present invention comprises heat supply means thermally connected to the supercooling latent heat storage material composition of the present invention housed in a container and transferring heat to the supercooling latent heat storage material composition from the outside. It is preferable. In addition, a heat transfer means is provided that is thermally connected to the supercooling latent heat storage material composition of the present invention housed in a container and transfers heat released from the supercooling latent heat storage material composition to the outside. Is preferred.
The heat supply means and the heat transfer means are not particularly limited as long as they have materials and structures capable of transferring heat, and examples thereof include a heat pipe and a heat transfer plate.
The heat supply means and the heat transfer means may have one or two or more fins (heat plates) that increase the heat exchange area.

  Examples of such a heat storage device include “heat storage device” described in JP2013-257080A.

  Although the preferable thermal storage system of this invention is demonstrated with reference to drawings, this invention is not limited to this.

  As shown in FIG. 3, a preferable heat storage device 1 used in the heat storage system of the present invention includes a pack 2 formed of an exterior material made of a flexible laminate film, and a supercooling type housed in the pack 2. Latent heat storage material composition 3 and nucleation device 4 for reversing dome-shaped metal plate 4c enclosed in pack 2 from a pair of metal rods 4a and 4b that can move forward and backward with respect to pack 2 outside pack 2 And a heat supply plate 5 and a heat transfer plate 6 that are arranged so as to sandwich the pack 2 vertically.

In the heat storage device 1, the supercooling latent heat storage material composition 3 is stably in a supercooled state even at −20 ° C. or lower. When taking out heat from the heat storage device 1, the supercooled latent heat storage material composition 3 in a supercooled state is moved from the outside of the pack 2 to the pack 2 side and enclosed inside the pressing The dome-shaped metal plate 4c is reversed and an impact is applied. Thereby, the supercooled latent heat storage material composition 3 is crystallized, and the released heat can be taken out from the heat transfer plate 6 to the outside. At this time, the supercooled latent heat storage material composition 3 is quickly crystallized. After the nucleation operation, one metal bar 4a is moved backward and separated from the pack 2. For the repetitive operation, the other metal rod 4b is advanced to the pack 2 side and the metal plate 4c is pushed from the opposite direction to return the metal plate 4c to its original shape.
On the other hand, when heat is supplied from the heat supply plate 5, the supercooling latent heat storage material composition 3 changes to a liquid phase. At this time, anhydrous sodium acetate is difficult to precipitate. When cooled as it is, it enters a supercooled state. When extracting heat, the nucleation device 4 is operated as described above.

  In this way, the heat storage device 1 can be used repeatedly. As described above, the heat storage device 1 is a device that is difficult to deposit anhydrous sodium acetate and has high repeatability.

  Although the heat storage device 1 includes one pack 2 in which the supercooled latent heat storage material composition 3 is stored, in the present invention, a plurality of packs 2 may be provided.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

Example 1
Sodium acetate, water, and alcohols shown in the following Tables 1 and 2 were mixed so as to have molar concentrations shown in Tables 1 and 2 below to prepare respective supercooled latent heat storage material compositions.
Tables 1 and 2 summarize the results obtained by measuring the following items for each of these samples.
Further, in each supercooled latent heat storage material composition, the ratio of the total mass (theoretical amount) of sodium acetate and water forming sodium acetate trihydrate to the total mass (theoretical amount) is shown in Tables 1 and 2. % By weight ”.

(Stability in supercooled state)
Three specimens of each of the supercooled latent heat storage material compositions were prepared, and the supercooling stability was confirmed. Each specimen was heated to 90 ° C., melted the supercooled latent heat storage material composition, cooled to −20 ° C., and maintained for 1 day, and then evaluated for the supercooled state. Each of the three specimens was evaluated for heating and cooling three times. In all cases, the case where the stability of supercooling could be maintained was evaluated as “◯”, and the case where it was crystallized even once was evaluated as “x”. The results are shown in Tables 1 and 2.

(Reliability of nucleation operation: certainty of crystallization)
Three samples that have been confirmed to be stable in the supercooled state are nucleated once after being cooled to 0 ° C. (one reversing operation of the metal plate), and the heat generated by the supercooled latent heat storage material composition Was confirmed. If the nucleation operation can be confirmed, the subcooling latent heat storage material composition is heated to 90 ° C., cooled to -20 ° C. and then nucleated once, and the heat generation of the subcooling latent heat storage material composition is confirmed. Went. This was regarded as one cycle, and three cycles were evaluated. In all cases, the case where heat generation due to nucleation could be confirmed was evaluated as “◯”, and the case where no nucleation occurred even once was evaluated as “x”.

(Repeated reliability)
In the above “reliability of nucleation operation”, after three cycles of nucleation and melting at 0 ° C., nucleation and melting at −20 ° C., each of the three specimens is again heated to 90 ° C. In the supercooled latent heat storage material composition in a melted state, it was confirmed whether it was completely melted or not melted. The case where 5% or more undissolved residue was confirmed on the volume basis was evaluated as “×”, and the case where the undissolved residue was confirmed but was less than 5% on the volume basis was evaluated as “◯”. It was shown in 2.

  In the present invention, it is important that the supercooled latent heat storage material composition satisfies all of the above evaluation items. Therefore, when it failed, subsequent evaluation was not performed and "-" was described in Table 1 and Table 2 in the column which has not been evaluated.

  As is clear from Table 1, samples 1 to 15 all have points at which the molar concentrations of sodium acetate, water and alcohol are point A, point B, point C and point D in the ternary composition diagram shown in FIG. The stability of the supercooled state, the certainty of crystallization, and the reliability of repeated use were all excellent.

  On the other hand, as apparent from Table 2, the molar concentrations of sodium acetate, water, and alcohol are within the polygonal region having points A, B, C, and D as vertices in the ternary composition diagram. None of Samples 16 to 23 were inferior in at least one of the stability of the supercooled state, the reliability of nucleation (certainty of crystallization), and the repetition reliability.

The following matters were found by comparison of the above-described supercooled latent heat storage material composition.
That is, in terms of reliability in the repeated use of the supercooled latent heat storage material composition, in the ternary composition diagram, the composition of the inner region of the straight line AB (including the straight line; the same applies hereinafter), the inner side of the straight line EB It turned out that it is excellent in order of the area | region and the inner area | region of the straight line MJ. Note that the composition of the inner region of the straight line EB is also preferable in terms of preventing deterioration (stability) of the phase change.
In terms of certainty and reliability of nucleation, in the ternary composition diagram, the composition of the inner region of the straight line AD, the composition of the inner region of the straight line EH (alcohol amount) and the straight line HG (water amount), and the straight line It turned out that it is excellent in the order of the composition of the inner region of IL.

It was found that the supercooling stability was stabilized when the composition was in the inner region of the straight line BC.
Furthermore, it was also found that the supercooling stability is lowered when the composition is in the inner region of the linear CD, and the phase-separated water is solidified to further lower the supercooling stability.
Further, it was found that the composition of the inner region of the straight line GF is excellent in the reliability of the repeated cycle of the phase change to the solid phase and the liquid phase, and particularly the composition of the inner region of the straight line LK is excellent.

Example 2
Regarding the supercooled latent heat storage material composition (sample Nos. 1 to 15) prepared in Example 1, as a preferable characteristic when used as a device, heat responsiveness during heat dissipation and heat generation, after repeated crystallization The phase stability and heat storage density of the supercooled liquid were evaluated. The results are shown in Table 3.
(Evaluation of thermal response)
Phase change time when each supercooled latent heat storage material composition is nucleated at 0 ° C (phase change time during nucleation) and melting time when kept at 80 ° C (phase change time during melting) Was measured. The phase change time when nucleating at 0 ° C. is the time required for crystallization to reach 90% from nucleation, and the melting time at 80 ° C. is 90% of crystals after reaching 80 ° C. The time required for melting was measured. The phase change time at the time of nucleation and the phase change time at the time of melting were evaluated three times for each of the three specimens, and were evaluated with the slowest phase change time.
The evaluation criteria are as follows.
“◎” when the latest phase change time is within 1 minute, “◯” when it is over 1 minute and within 5 minutes, “△” when it is over 5 minutes and within 10 minutes In the case where either the phase change time during nucleation or the phase change time during melting exceeds 10 minutes, “x” is given.
If the evaluation is “Δ” or more, the material satisfies the thermal responsiveness required when used as a device.

(Evaluation of phase change stability)
First, the average volume fraction of the portion crystallized 10 minutes after nucleating each of the supercooled latent heat storage material compositions at 0 ° C. was defined as the initial crystallization rate and measured.
Next, after 100 cycles of the phase change process of melting and nucleation at 0 ° C. as one cycle, three samples were nucleated at 0 ° C., and the average volume fraction of the portion crystallized from the supercooled liquid The value was measured. A value obtained by dividing the measured value by the initial crystallization rate was defined as a crystallization change rate. This crystallization change rate is an index that can evaluate the phase stability of the crystallized supercooled liquid, and when it is 100%, it means that there is no change due to repetition (phase change stability is high).
The evaluation criteria are as follows.
When the rate of crystallization change is 95% or more, “◎”, when it is 90% or more and less than 95%, “◯”, when it is 80% or more and less than 90%, “△”, less than 80% The case where it was was made into "x".
If the evaluation is “Δ” or more, the material satisfies the phase change stability required for use as a device.

(Heat storage density)
The heat storage density of each supercooled latent heat storage material composition was measured by the above method.
Evaluation is “◯” when the heat storage density is 75 kJ / kg or more, “Δ” when 70 kJ / kg or more and less than 75 kJ / kg, and “X” when it is less than 70 kJ / kg. did.
If the evaluation is “Δ” or more, the material satisfies the heat storage density required for use as a device.

  As is clear from Table 3, the composition in the region of the polygon EBFGH and further the composition in the region of the polygon MJKLI than the composition in the region of the polygon ABCD in the ternary composition diagram are overcooled. In addition to the stability of the state, the certainty of crystallization, and the reliability of repeated use, it also has excellent thermal responsiveness, phase change stability, and heat storage density, and was found to be suitable for use as a device.

Example 3 Using the supercooled latent heat storage material composition (sample Nos. 1 to 15) prepared in Example 1, the heat storage system shown in FIG. 3 was constructed and the characteristics thereof were confirmed. As a result, in each heat storage system, the supercooled state is stably maintained before the nucleation operation, and crystallization progresses reliably when stimulated by the nucleation operation. It returned to the supercooled state. That is, all of these heat storage systems showed high reliability in the repeated use of the above cycle consisting of an endothermic process and a heat release process.

DESCRIPTION OF SYMBOLS 1 Heat storage device 2 Pack 3 Supercooling type latent heat storage material composition 4 Nucleation device 4a, 4b Metal rod 4c Metal plate 5 Heat supply plate 6 Heat transfer plate

Claims (7)

A supercooled latent heat storage material composition containing sodium acetate, water and alcohol,
The alcohol is one or more alcohols selected from the group consisting of ethylene glycol, propylene glycol, 1-propanol, 2-butanol and 1,3-butanediol;
In the ternary composition diagram of sodium acetate, water and alcohol shown in FIG. 1, the molecular molar concentrations of sodium acetate, water and alcohol are point A (sodium acetate 22.6 mol%, water 60.8 mol%, Alcohol 16.6 mol%), point B (26.2 mol% sodium acetate, water 70.9 mol%, alcohol 2.9 mol%), point C (sodium acetate 17.8 mol%, water 81.1 mol%, alcohol 1.1 mol) %) And point D (sodium acetate 14.4 mol%, water 79.1 mol%, alcohol 6.5 mol%) in the polygonal region (including on the boundary line) as the vertex, but supercooled latent heat storage Material composition.   In the ternary composition diagram, the molecular molar concentrations of the sodium acetate, the water, and the alcohol are point E (sodium acetate 21.4 mol%, water 64.3 mol%, alcohol 14.3 mol%), point B, respectively. (Sodium acetate 26.2 mol%, water 70.9 mol%, alcohol 2.9 mol%), F point (sodium acetate 21.5 mol%, water 76.4 mol%, alcohol 2.1 mol%), G point (sodium acetate 18 .2 mol%, water 77.7 mol%, alcohol 4.1 mol%) and within the polygonal region with the H point (sodium acetate 18.2 mol%, water 72.7 mol%, alcohol 9.1 mol%) as vertices (however, The overcooling type latent heat storage material composition according to claim 1, which is included on the boundary line.   In the ternary composition diagram, the molecular molar concentrations of the sodium acetate, the water and the alcohol are M points (sodium acetate 22.3 mol%, water 67.0 mol%, alcohol 10.7 mol%), J points, respectively. (Sodium acetate 24.3 mol%, water 73.0 mol%, alcohol 2.7 mol%), K point (sodium acetate 23.0 mol%, water 74.5 mol%, alcohol 2.5 mol%), L point (sodium acetate 21 .4 mol%, water 73.8 mol%, alcohol 4.8 mol%) and within a polygonal region with the I point (sodium acetate 21.4 mol%, water 67.9 mol%, alcohol 10.7 mol%) as vertices (however, The supercooled latent heat storage material composition according to claim 1, wherein the composition is on a boundary line.   The total mass of the sodium acetate and the water that forms sodium acetate trihydrate is 70% by mass to 95% by mass in the total mass of the sodium acetate, the water, and the alcohol. The supercooled latent heat storage material composition according to any one of the above.   The subcooling latent heat according to any one of claims 1 to 4, wherein the thickener is contained in an amount of 0.001 parts by mass to 5.0 parts by mass with respect to 100 parts by mass of the total mass of the water and the alcohol. Thermal storage material composition.   The supercooled latent heat storage material composition according to any one of claims 1 to 5, wherein the supercooled latent heat storage material composition is maintained at a temperature of -20 ° C or less and generates heat by crystallization by nucleation operation.   The supercooled latent heat storage material composition according to any one of claims 1 to 6 is crystallized from a supercooled state by nucleation operation to dissipate heat, and after heat dissipation, the crystal is melted by heating, A heat storage system that repeatedly uses the cycle to return to the cooling state.

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