JPH0650686A - Latent heat accumulator - Google Patents

Abstract

PURPOSE:To enhance a load follow-up capacity and heat storage efficiency of brine by setting concentrations of inorganic salts to be dissolved in an aqueous solution to concentration ranges not exceeding component concentration ranges corresponding to an ice point and and a eutectic point and an N component eutectic point of the inorganic salt and water. CONSTITUTION:Capsules 2 sealed with latent heat accumulator 1 are filled in a heat storage tank 23, brine heat exchanged by a load side heat exchanger 22 is charged from above the tank 23, heat exchanged with the capsules 2, and then sent to a load side heat exchanger 22 via a pump 24 and a bypass passage 25. The accumulator sealed in the capsule 2 is obtained by dissolving inorganic salts of (N-1) types with water as three or more N (N>=3) component series, and concentrations of the salts to be dissolved in the solution are set to a concentration range not exceeding component concentration ranges corresponding to an ice point and eutectic point and N component eutectic point of the inorganic salts and water. Thus, a load follow-up capacity and heat storage efficiency of brine can be enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat storage device using a capsule containing a heat storage agent.

[0002]

2. Description of the Related Art Conventionally, there has been known a heat storage device which uses heat generated by solidifying / melting water or brine stored in a heat storage tank, and such a heat storage device is better than sensible heat storage means. It has a high heat storage density, is easy to extract cold / heat at a constant temperature, and has a small system and a simple configuration, so its range of use is wide, and it is used in various fields such as the consumer industry including the food industry. It's being used.

In this heat storage device, a large number of capsules containing a eutectic composition aqueous solution of an inorganic salt and other heat storage agents are charged in a heat storage tank, and then the brine is directly contacted with brine to perform heat storage. A so-called capsule type heat storage device that takes out cold / heat, and water or brine stored in the heat storage tank is directly solidified by using a cooling pipe to perform hot heat cold storage, and then the molten heat of the solidified body. It is roughly divided into the so-called ice bank type that takes out cold heat by using the former, but the former is the state that the capsule heat is stored in the brine in the heat storage tank, and the heat storage and the cold / heat extraction Since it is possible to circulate, it is possible to circulate a large amount of brine with a small device, which is preferable. In addition, as a specific conventional technique that refers to the heat storage agent to be encapsulated in the capsule, an aqueous solution of an inorganic carbonate, an inorganic nitrate, or an organic halogenated hydrocarbon is generally used.

[0004]

However, if such a two-component heat storage agent is enclosed in a capsule as it is, the following problems occur. That is, in this device, since the method of transferring cold energy is through the [capsule], in the process of cold heat storage and removal,
[Refrigerator cooling pipe] → [Brine] → [Capsule] or vice versa, and as a result, the evaporation temperature of the refrigerant in the refrigerator cooling pipe has to be set low, and in particular, the heat storage agent When frozen in a capsule, the frozen eutectic ice melts in the capsule due to natural convection during melting, resulting in a slow melting temperature and insufficient melting under load, resulting in a heat storage tank. The temperature inside has risen,
It is not possible to maintain the brine temperature sent from the heat storage tank at a predetermined low temperature, resulting in a reduction in heat storage efficiency.

Therefore, the inventor of the present invention has studied the use of the heat storage agent for heat storage used in the ice bank heat storage method. For example, Japanese Patent Laid-Open No. 62-62192 (hereinafter referred to as “first conventional technology”) discloses two kinds of inorganic salts having a eutectic point of less than 0 ° C., more specifically, chlorides forming eutectic crystals. We have proposed using a mixed aqueous solution of sodium and potassium chloride as a heat storage agent. Also, JP-A-2-2147
In Japanese Patent Laid-Open No. 93 (hereinafter, referred to as the second prior art), the above-mentioned heat storage agent is further investigated, and an aqueous solution in which potassium nitrate and sodium nitrate are dissolved is used as the heat storage agent. A heat storage agent has been proposed that takes out the heat generated by the above as cold heat of about -5 ° C.

However, as in each of the above-mentioned prior arts, 3
When the heat storage agent having a primary eutectic point is enclosed in a capsule, when the initial concentration of the inorganic salt exceeds the concentration of the eutectic point, the inorganic salt crystal or the inorganic salt of the inorganic salt itself is cooled during cooling. Salt hydrates precipitate, but these precipitates precipitate in the capsules, and when the precipitates are dissolved again in the solution during cold heat removal, the heat storage agent for heat transfer is also at a low temperature, and the heat transfer The rate of redissolution in the heat storage agent solution is limited.

In view of the above-mentioned drawbacks of the prior art, the present invention improves the heat transfer characteristics of the capsule heat storage agent by increasing the melting rate of the heat storage agent stored in the capsule, thereby improving the load followability of brine. The purpose is to improve the heat storage efficiency. Another object of the present invention is to provide a heat storage device for heat storage, which is configured to easily and accurately take out desired temperature cold heat.

[0008]

DISCLOSURE OF THE INVENTION The present invention provides a heat storage apparatus in which a heat storage tank filled with a capsule containing a heat storage agent is provided in a part of a circulation circuit for a cooling medium, and at least the capsule contains at least the heat storage tank. A heat storage agent obtained by dissolving (N-1) kinds of inorganic salts in water as 3 or more N (N ≧ 3) component system is enclosed, and the concentration of each inorganic salt dissolved in the aqueous solution is adjusted. , A freezing point, a eutectic point of the inorganic salt and water, and a concentration region that does not exceed the concentration range of each component corresponding to the N-component eutectic point are proposed.

In this case, the concentration of each inorganic salt in the aqueous solution is in the range of 50 to 98% of the concentration of the eutectic line connecting the eutectic point of the water and each inorganic salt and the N-element eutectic point. The content of the at least one inorganic salt in the aqueous solution is preferably set in the range of 60 to 98% of the concentration of the eutectic crystal of the one inorganic salt and water, and in the aqueous solution. It is preferable that the total content of the inorganic salt is set to be equal to or lower than the concentration of the N component eutectic of the heat storage agent.

[0010]

Next, the operation of the present invention will be described in detail. The heat storage agent is an N component solution (N ≧ 3) consisting of water and at least two types of water-soluble inorganic salts, and the concentration of the inorganic salt in the heat storage agent is a freezing point, water and a eutectic of each inorganic salt. Points and the concentration range not exceeding each component concentration range corresponding to the N component eutectic point, as shown in FIG. 2, in the heat storage tank in which the capsule containing the heat storage agent is put in the refrigeration cycle. When the brine is circulated and cooled below the freezing point, initially, the heat storage agent in the capsule is cooled while keeping the state of the aqueous solution by the freezing point lowering effect of the inorganic salt, but when cooled below the freezing point lowering effect, ice and A binary eutectic crystal is precipitated in the descending order of the binary eutectic point of each of the (N-1) types of inorganic salts, resulting in a two-phase state of the binary eutectic material and the inorganic salt mixed aqueous solution. When cooling is further advanced in this state to reach the N-ary eutectic point, the heat storage agent for precipitation contains N-component eutectic crystals in addition to ice / binary eutectic crystals, and finally ice / binary eutectic It becomes one phase of a solid phase mixture of N component eutectic. In the above process, the solidification heat of the ice is absorbed as the ice precipitates, and the eutectic heat is absorbed even when the ice is transformed into a eutectic. Therefore, the temperature change is buffered due to the absorption of solidification heat associated with the precipitation of the solidified product, as compared with the case where the binary eutectic composed of only one inorganic salt and water is encapsulated and cooled.

Therefore, comparing a capsule heat storage device according to the present invention with a capsule heat storage device using each of the capsules containing the two-component eutectic, the former shows that the temperature change due to absorption of coagulation heat is buffered. Therefore, it is possible to maintain the temperature of the brine sent from the heat storage tank at a predetermined low temperature without sufficiently increasing the temperature in the heat storage tank against the load of the brine, resulting in an increase in heat storage efficiency. Connect

Further, since the N component eutectic point of the heat storage agent is lower than the eutectic point of each inorganic salt and water, the take-out temperature can be adjusted by appropriately selecting the inorganic salt. A eutectic line connecting the binary eutectic point and the N-element eutectic point of water and each inorganic salt with the concentration of each inorganic salt in the heat storage agent can be set to an arbitrary low temperature below the freezing point. Of the concentration of 50
To 98%, and more preferably, the concentration of one inorganic salt in the heat storage agent is set to 60 to 98% of the concentration of the eutectic of the inorganic salt and water. And the total content of the inorganic salt in the heat storage agent,
By setting the concentration below the N-component eutectic, there is no risk of precipitation of inorganic salts or hydrates of inorganic salts during the cooling process. The speed of re-dissolution in the heat storage agent solution is not limited, and as a result, the heat transfer characteristics of the capsule heat storage agent are improved, whereby the load followability of brine and the heat storage efficiency can be enhanced.

Therefore, according to the present invention, the heat storage agent for storage in the heat storage tank is an aqueous solution prepared by dissolving (N-1) kinds of inorganic salts in water as at least 3 or more N (N ≧ 3) component system. Yes Select an arbitrary temperature as the freezing point from the temperature range above the temperature of the N-ary eutectic point and below the temperature of the binary eutectic point by changing the concentration of each inorganic salt in this aqueous solution within a predetermined concentration range. Even if a capsule is used, cold heat at a desired temperature can be easily and accurately taken out.

[0014]

Embodiments of the present invention will now be illustratively described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative positions and the like of the components described in this embodiment are not intended to limit the scope of the present invention thereto, but are merely examples, unless otherwise specified. Not too much.

FIG. 1 is a schematic view showing a refrigerating system in which a heat storage device for heat storage according to an embodiment of the present invention is incorporated in a circulation circuit of brine. To briefly explain the structure, 11 is driven by a power source. In this compressor, a discharge side of the compressor 11 is connected to an evaporator 14 via a condenser 12 and an expansion valve 13, and a refrigerating closed cycle in which the refrigerant evaporated from the evaporator 14 is recompressed by the compressor 11. 10 are formed. A coil-shaped heat exchanger 21 forming a brine circulation circuit 20 is inserted in the evaporator 14, and the heat exchanger 2
1, the load side heat exchanger 22, the heat storage tank 23, and the pump 24 constitute a brine circulation circuit 20. Further, 25 is a bypass path for brine, for example, the refrigeration cycle 1 at night.
After storing the heat in the heat storage tank 23 at 0, the power can be saved by switching to the bypass path 25 during the daytime load operation. Further, the heat storage tank 23 is filled with a capsule 2 enclosing a heat storage agent 1 made of a ternary eutectic of an inorganic salt, and brine heat-exchanged by a load side heat exchanger 22 is introduced from above the heat storage tank 23. The capsule 2
After exchanging heat with the pump 24 and the bypass 25
It is sent to the load side heat exchanger 22 side.

The heat storage agent 15 contained in the capsule 2 is water and two kinds of inorganic salts, potassium nitrate (KNO ₃ ).
And the sodium nitrate (NaNO ₃ ) in the above three-component system, the characteristics of which will be described with reference to Table 1 and FIG. Table 1 below shows potassium nitrate (KNO ₃ ) -sodium nitrate (Na
NO ₃ ) -water (H ₂ O) ternary system related eutectic concentration,
FIG. 2 is a solid-liquid equilibrium diagram of the ternary system in which the eutectic point is shown in FIG.

In the solid-liquid equilibrium diagram of FIG. 2, the concentration of each component is set to 100% by weight on the ridgeline, and the state of the three components is shown in a triangular prism whose temperature is graduated in the vertical direction. Points A, B, and C are melting points of potassium nitrate, sodium nitrate, and water, point E ₁ is a eutectic point of potassium nitrate and water, and point E ₂ is a eutectic point of potassium nitrate and sodium nitrate. , And E ₃ is the eutectic point of sodium nitrate and water. The temperatures at these points and the weight concentration of each component are shown in Table 1.

[0018]

[Table 1]

In FIG. 2, the line AE ₁ is a solid-liquid phase line showing the temperature at which potassium nitrate crystals precipitate during the cooling process of a binary aqueous solution having a potassium nitrate concentration range of 8 to 100% by weight. The line CE ₁ is a solid-liquid phase line showing the temperature at which ice precipitates during the cooling process of an aqueous solution in which the concentration range of potassium nitrate is 0 to 8% by weight. In the temperature regions AA ₁ E ₁ and CC ₁ E ₁ sandwiched between both solid-liquid phase lines and the isotherms A ₁ · E ₁ · C ₁ passing through the binary eutectic point E ₁ (-3.5 ° C) In the former region, potassium nitrate-water solution and in the latter region, ice-
Solids and liquids of aqueous solutions coexist. By the way, when cooled below the eutectic point E ₁ , the aqueous solution can no longer exist,
It becomes a solid mixture of potassium nitrate-eutectic and ice-eutectic, respectively.

When the temperature is below the solid-liquid phase line and above the eutectic point, the concentration is, for example, [p / (p + q)].
× 100% by weight the co-vertical line KK'K ₁ showing a potassium nitrate aqueous solution K is Akirasen A ₁ K ₁ 'intersection of the K' C ₁ parallel to the temperature lines t are, in the temperature line t ' It is known that the ratio of the distance r from the intersection K ′ to the ridge of water and the distance s from the intersection K ′ to the solid-liquid phase line indicates the weight ratio of solid and liquid. That is, the solid-liquid phase line AE ₁ also indicates the solubility of sodium nitrate. The solid-liquid line CE ₁ is
The weight ratio of ice and aqueous solution in potassium nitrate aqueous solution thinner than the concentration of eutectic is shown. Similarly, the solid-liquid phase line AE ₂ and the solid-liquid phase line BE ₂ show the coexistence limits of potassium nitrate-melt solution and sodium nitrate-melt solution in the potassium nitrate-sodium nitrate component system, respectively. The line BE ₃ and the solid-liquid phase line CE ₃ are respectively for the sodium nitrate aqueous solution,
It is a temperature-concentration curve which shows the limit of coexistence of sodium nitrate-aqueous solution and ice-aqueous solution.

Further, the line E ₁ E represents the solid-liquid phase line of the precipitate-eutectic E ₁ -aqueous solution in the above-mentioned three-component system of potassium nitrate-sodium nitrate-water, in which the concentration of the inorganic salt is Is greater than or equal to the solid-liquid phase line E ₁ -E, the precipitate is an inorganic salt crystal, and conversely, when the concentration is less than or equal to the solid-liquid phase line E ₁ E, the precipitate is ice. Similarly, line E3E the precipitates - eutectic E ₃ - shows a solid-liquid phase line of the aqueous solution, if the 3-component concentration solid-liquid phase line of an inorganic salt E ₃ E above, the precipitates If it is an inorganic salt crystal and, on the contrary, it is not more than the solid-liquidus line E ₃ E, the precipitate is ice.

When the temperature is lower than the eutectic point E, it is a solid mixture of precipitate-eutectic E, and the precipitate is 3
Depending on the concentration of the component system, it is a mixture of inorganic salt crystals, ice, eutectic crystal E ₁ or eutectic crystal E ₂ .

Here, strictly speaking, the aqueous solution of the inorganic salt cannot exist above the boiling point of the aqueous solution (about 100 ° C. at atmospheric pressure). Therefore, the solid-liquid phase line above the boiling point in FIG. 2 is an imaginary line, and although it is a line that can be realized at high pressure, it is shown to grasp the whole image.

The ternary eutectic point E is shown in FIG.
As such, it is −22.8 ° C. Therefore, the three-component system
The composition is the eutectic point E of the three-component system, potassium nitrate-water two-component
Eutectic point E of the system₁, Sodium nitrate-water binary system eutectic point
E₃, And the concentration not exceeding the solid-liquid phase curved surface including the freezing point C
Temperature range, ice and eutectic E during the cooling process
1, E₃While eutectic point reaches eutectic point-22.8 ℃
Cold heat can be stored. Furthermore, the concentration of the inorganic salt is
In the cooling process, the
Temperature at which solid precipitates are formed (hereinafter referred to as the freezing point)
Can be set arbitrarily. As heat storage agent 15
Example in which the freezing point was −5 ° C. using the three-component system
1, Example 2 in which the freezing point was −11 ° C., and
Potassium nitrate and glass of Example 3 with a fixing point of -22 ° C
Table 2 shows the concentration and characteristics of the aqueous solution of sodium acid.

[0025]

[Table 2]

Next, the operation of the present invention will be described. First, the spherical heat storage agent of Example 1 is filled in the spherical capsule 2 having a diameter of 30 to 80 mm, and then the capsule 2 is stacked and filled in the heat storage tank 23. And the brine has a freezing point of -25.
When cold heat is stored in the capsule 2 by using brine of ℃ or less, first, the refrigerating cycle 10 is operated to compress the primary refrigerant such as Freon gas by the compressor 11 and the discharged primary refrigerant to the condenser. In 12, the condensed refrigerant is condensed and liquefied, and then the pressure of the primary refrigerant is reduced and vaporized through the expansion valve 13, and the primary refrigerant is flowed into the evaporator 14.

In the evaporator 14, the primary refrigerant exchanges heat with the brine circulating in the coil heat exchanger 22 to evaporate it, and then flows into the suction side of the compressor 11 again. On the other hand, the brine exchanges heat with the capsule 2 in the heat storage tank 23 to cool the heat storage agent 15 in the capsule 2,
Due to the freezing point lowering effect, no freezing occurs even at 0 ° C., and the temperature at which the solid-liquid phase curved surface shown in FIG. 2 intersects, that is, the freezing point of −5 ° C. at the concentration of Example 1, first ice, and then eutectic E ₁
A solid containing as a main component is deposited. That is, as shown in the solidification / melting characteristic diagram of FIG. 3, the heat storage agent 15 absorbs and accumulates cold heat in the form of the solidification heat quantity of 72 kcal / g while maintaining approximately −5 ° C. And before reaching the eutectic point E of three components, IPF
The heat storage process in the heat storage tank 2316 is terminated when the ratio of the ice / binary eutectic in the aqueous solution of the heat storage agent reaches 30 to 80%.

Next, for example, during the daytime load operation, the heat storage tank 23
For more heat dissipation, the brine circulation circuit 20 is switched to the bypass circuit and then the pump 24 is operated to collect the liquid portion of the heat storage agent 15 and the inorganic salt deposits in the heat storage tank 23.
It is circulated to the load heat exchanger 2219 via the bypass passage 17. As shown in FIG. 3, the heat storage agent 15 radiates melting heat having a heat quantity of 72 kcal / g while maintaining a temperature of approximately -5 DEG C. Therefore, the load side of the heat exchanger 22 has a temperature of -5 DEG C. Can receive cold heat. Further, when Example 2 is enclosed in the capsule 2 as the heat storage agent 1,
Heat was stored in the heat storage tank 23 in the same manner as in Example 1, and in the cold heat extraction process, the heat of the heat storage agent 1 having a heat transfer amount of 65 kcal / g was taken out as cold heat while keeping -11 ° C substantially constant, and heat exchange was performed. The load side of the vessel 22 can receive cold heat of -11 ° C.

As described above, according to the above configuration, the heat storage process is finished when the IPF reaches less than 100%, for example, 50% in the heat storage process.
In the solidification / melting characteristics of No. 3, the IPF increases and does not reach the ternary eutectic point E, and the heat of the eutectic body E ₁ can be substantially taken out as cold heat while ensuring the above take-out temperature. Further, since the IPF is set to less than 100%, the heat storage agent 1 for heat storage is not completely frozen and at least a part of the heat storage agent is always in a liquid state. Therefore, heat exchange is easy even through the capsule 2.

For example, when the fluctuation of the inlet temperature of the pump 24 on the outlet side of the heat storage tank 23 is compared with that of the above embodiment, as compared with the case of using a two-component inorganic salt aqueous solution for the heat storage agent 1 in the capsule 2, It was confirmed that the variation amount was reduced to 1/3 or less in this example, and that the brine at a constant temperature could be obtained with high accuracy. In addition, the IPF of the heat storage agent of Example 3 was set to 1
When the heat is stored up to 00%, when the heat storage process is terminated when it reaches 80%, it is confirmed that the heat fluctuation is large at the initial stage of heat radiation, and it is difficult to accurately follow it when the fluctuation on the load side is large. It was In addition, in the above-mentioned embodiment, the three-component heat storage agent was described, but as the four-component heat storage material 15, sodium nitrate as water and two salts which do not have common ions as inorganic salts ( An aqueous solution composed of NaNO ₃ ) and ammonium chloride (NH ₄ Cl) can be used.

Aqueous solution containing only two kinds of inorganic salts
Will be treated as four components, and the reason will be described below.
The two types of inorganic salts do not have a common anion
In addition, it is ionized / bonded in an aqueous solution and
Salt, salt (NaCl), ammonium nitrate (NH_FourNO₃) Forms
there is a possibility. Of the above four types of inorganic salts, NaCl is xNa
NO 3 + yNH_FourCl-zNH_FourNO₃Can be represented by
The solution is NaNO₃， NH_FourCl, NH 4NO₃, And H₂As 4 components of O
Will be handled. In this case, in the four-component system,
The concentration of sodium nitrate in the aqueous solution is 30% by weight and salt
If the concentration of ammonium iodide is 7% by weight, the
A melting point is obtained.

[0032]

As described above, according to the present invention, the heat transfer property of the heat storage agent in the capsule is improved by increasing the melting rate of the heat storage agent in the capsule that solidifies in the capsule, and thus the load of the brine is increased. It is possible to improve the following ability and heat storage efficiency. Further, according to the present invention, temperature cold heat can be taken out easily and accurately. It has various remarkable effects.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a refrigeration system incorporating a heat storage device according to an embodiment of the present invention.

FIG. 2 is a solid-liquid phase equilibrium diagram of the three-component system of the heat storage agent enclosed in capsules.

[Explanation of symbols]

 1 heat storage agent 2 capsules 23 heat storage tank

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Soichiro Shibata 1-3-1, Uchisaiwaicho, Chiyoda-ku, Tokyo Tokyo Electric Power Company (72) Inventor Noriyuki Shimamura 1-3-1, Uchiyuki-cho, Chiyoda-ku, Tokyo Within the Tokyo Electric Power Company (72) Inventor Naritake Kawasaki 1-12-6 Hachimandai, Isehara-shi, Kanagawa (72) Keisuke Kasahara 3-6-11 Shirasagi, Nakano-ku, Tokyo (72) Inventor Sakuma Seiichi, 12-12-14, Sugakuya, Tama-ku, Kawasaki-shi, Kanagawa Prefecture (72) Inventor Fujio Komatsu, 2-13-1, Botan, Koto-ku, Tokyo Maekawa Works Ltd. (72) Inventor Masaya Ishikawa, Botan, Koto-ku, Tokyo Maekawa Manufacturing Co., Ltd. 2-13-1 Kunio Sugiyama 72-35 Kunio Sugiyama 7-35 Higashiohisa Arakawa-ku Tokyo Asahi Denka Kogyo Co., Ltd. (72) Inventor Masashige Mitsuo 7-35, Higashiokyu, Arakawa-ku, Tokyo Asahi Denka Kogyo Co., Ltd. (72) Inventor Minoru Shindo 7-35, Higashiohisa, Arakawa-ku, Tokyo Asahi Denka Kogyo Co., Ltd. (72) Inventor Kawamura Kuniaki 1-13-8 Mizukino, Moriya-cho, Kitasoma-gun, Ibaraki Prefecture

Claims (3)

[Claims] 1. A heat storage apparatus in which a heat storage tank filled with a capsule containing a heat storage agent is provided in a part of a circulation circuit of a cooling medium, wherein at least 3 or more N (N ≧ 3) is provided in the capsule. ) As a component system, a heat storage agent obtained by dissolving (N-1) kinds of inorganic salts in water is enclosed, and the concentration of each inorganic salt dissolved in the aqueous solution is adjusted to the freezing point and the inorganic salts and water. And a eutectic point of N and a eutectic point of N component. 2. The concentration of each inorganic salt in the aqueous solution is set within a range of 50 to 98% of the concentration of the eutectic line connecting the eutectic point of the water and each inorganic salt and the N-element eutectic point. Claim 1
Heat storage device described 3. The content of the at least one inorganic salt in the aqueous solution is set to a range of 60 to 98% of the concentration of the eutectic crystal of the one inorganic salt and water, and the inorganic salt in the aqueous solution is set. The heat storage device according to claim 1, wherein the total content of salt is set to be equal to or lower than the concentration of the N-component eutectic of the heat storage agent.