JPH05256591A - Heat accumulating tank using solid/liquid mixture heat accumulating material - Google Patents

Abstract

PURPOSE:To obtain a heat accumulating tank using solid/liquid mixture heat accumulating material of a structure in which a casing is not damaged even if the material having a large volume change in the case of a phase change of solidifying.melting of nitrate or the like is used for the tank. CONSTITUTION:A solid heat accumulating material and a heat accumulating material which is solid at the ambient temperature and becomes liquid at an elevated temperature in a heat accumulating temperature range are filled in a heat accumulating tank 11, and solid/liquid mixture heat accumulating material 12 having an electric heater 14 of a heating source arranged to the heat accumulating material 12 and a heat transfer tube 13 in which liquid is introduced is used. The heater 14 is inserted from an upper part of the tank 11 into the material 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat storage tank using a solid-liquid mixed heat storage material, and more particularly to a heat storage tank suitable for using a heat storage material having a large volume change in solidification and melting.

[0002]

2. Description of the Related Art Conventionally, magnesia or nitrate has been mainly used as a heat storage material in a heat storage tank having a heat storage temperature of 100 ° C. or more. A heat storage tank using a solid heat storage material such as magnesia has a large heat storage capacity, but has a problem that cracks occur in the solid heat storage material due to repeated heat input and output, and heat transfer characteristics deteriorate. Further, nitrate is used in a liquid state of 142 ° C. (melting temperature) or more and 600 ° C. (pyrolysis temperature) or less, and a heat storage tank using this liquid heat storage material has excellent heat transfer characteristics because it can flow. Since the heat storage capacity is smaller than that of magnesia, there is a problem that the heat storage capacity is reduced by using this. Therefore, the applicant of the present invention has previously proposed a heat storage tank using a solid-liquid mixed heat storage material in which solid magnesia is made into a clinker (small piece) shape, and liquid nitrate is permeated into the gaps of the magnesia clinker by taking advantage of both of them. Wishhei 2-
No. 84505 (Japanese Patent Laid-Open No. 282101) was filed.

Such a conventional heat storage tank has a structure shown in FIG. In FIG. 4, the heat storage tank 11 is filled with the solid-liquid mixed heat storage material 12, and a heat transfer tube 13 and an electric heater 14 serving as a heating source are arranged inside the heat storage tank 11. The electric heater 14 is installed laterally at a relatively lower portion in the heat storage tank 11, and the heat transfer tube 13 is formed in a meander structure and is disposed entirely in the solid-liquid mixed heat storage material 12. The solid-liquid mixed heat storage material 12 in the heat storage tank 11 is heated to a high temperature by the electric heater 14. When a demand for heat output is generated, a liquid such as water 15 is passed through the heat transfer tube 13, the water 15 exchanges heat with the high temperature solid-liquid mixed heat storage material 12, and the steam 16 flows inside the heat transfer tube 13. A high temperature fluid such as is generated and supplied to the outside. Note that reference numeral 17 is an expansion tank provided in a water passage pipe for water 15, and reference numeral 18 is a space space formed above the heat storage tank 11.

In the heat storage tank 11 constructed as described above, the nitrates become liquid and heat the air layer between the solid-liquid mixed heat storage material 12 and the heat transfer tube 13 and the solid-liquid mixed heat storage material 12 and the electric heater 14. Since it becomes a medium and is buried, the heat transfer is good. Therefore, during heat storage, the solid-liquid mixed heat storage material 12
Can be rapidly heated, and at the time of heat output, rapid heat transfer from the solid-liquid mixed heat storage material 12 to the heat transfer tube 13 is possible.

However, when the heat storage tank 11 using this solid-liquid mixed material as the heat storage material 12 stores heat at 500 ° C. and heat input / output is repeated until the temperature reaches 100 ° C., the heat input is repeated at the third heat input. A trap was generated in which the casing of the heat storage tank 11 was damaged along with a roar. When the cause of damage to the heat storage tank 11 was investigated, when the solidified nitrate melted, about 13
% Volume expansion occurs, and due to this volume expansion, the heat storage tank 11
It turned out that the casing of was damaged.

[0006]

In such a conventional heat storage tank 11, sufficient consideration is not given to solidification / melting of nitrate, that is, volume change due to phase change.
Therefore, once solidified, there is a problem that the casing of the heat storage tank 11 is damaged due to an increase in the volume of nitrate when remelting.

Therefore, the present invention has been made to solve the above problems, and an object thereof is to provide a heat storage tank using a heat storage material such as nitrate having a large volume change at the time of phase change of solidification and melting. Even if there is, it is to provide a heat storage tank using a solid-liquid mixed heat storage material having a structure that does not damage the casing.

[0008]

In order to achieve the above object, a heat storage tank using the solid-liquid mixed heat storage material according to the present invention has the following configuration. That is, a solid heat storage material and a heat storage material that is solid at normal temperature and becomes a liquid in the heat storage temperature range are filled, and an electric heater that is a heating source disposed between the heat storage materials and a liquid inside In a heat storage tank using a solid-liquid mixed heat storage material having a heat transfer tube to which is introduced, the electric heater is inserted into the heat storage material from an upper portion of the heat storage tank.

An electric heater, which is a heating source, is filled with a solid heat storage material and a heat storage material that is solid at room temperature and is heated to become a liquid in the heat storage temperature range. In a heat storage tank using a solid-liquid mixed heat storage material having a heat transfer tube into which a liquid is introduced, an electric heater arranged in the tube group of the heat transfer tube is solid at room temperature from the heat transfer tube. It is characterized in that it is installed at a position sufficiently distant to absorb the volume expansion during the phase change of the heat storage material that rises in temperature and becomes liquid in the heat storage temperature range.

Further, in the present invention, the solid heat storage material is magnesia, and the heat storage material that is solid at normal temperature and becomes liquid in the heat storage temperature range by heating is a mixture of sodium nitrate, sodium nitrite and potassium nitrate, or , Sodium nitrate and potassium nitrate.

[0011]

According to the above structure, since the electric heater as a heating source is inserted into the heat storage material from the upper part of the heat storage tank, the heat storage material (mixture of nitrates) solidified at room temperature is mixed with the electric heater. First, the heat is melted from the vicinity of the surface of the electric heater. By this melting, the heat storage material on the surface of the electric heater becomes a liquid and becomes a fluid state. The heat storage material whose volume has expanded due to melting rises along the surface of the electric heater,
It is possible to escape to the space above the heat storage material. For this reason, even if a heat storage material that expands in volume with melting is used, no large stress is generated, so that the casing of the heat storage tank is not damaged.

Further, the electric heater arranged in the tube group of the heat transfer tubes is expanded from the heat transfer tubes in volume at the time of phase change of the heat storage material which is solid at room temperature and rises in temperature to become liquid in the heat storage temperature range. Since the heat storage material is installed at a position sufficiently distant from the heat transfer tube, it solidifies from the vicinity of the surface of the heat transfer tube when the heat storage material solidifies, and when all the heat storage material solidifies, a void is generated near the electric heater.
Therefore, even if the heat storage material melts again, the volume expansion can be absorbed by the voids, so that the casing of the heat storage tank is not damaged.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of the present invention, which is shown in FIG.
The same members as those are indicated by the same reference numerals. In FIG. 1, a heat storage tank 11 is filled with a solid-liquid mixed heat storage material 12, inside which a heat transfer tube 13 and an electric heater 14 as a heating source are arranged. The electric heater 14 is disposed inside the solid-liquid mixed heat storage material 12 through the space 18 from the upper part of the solid-liquid mixed heat storage material 12 in the heat storage tank 11. The heat generating portion of the electric heater 14 is buried inside the solid-liquid mixed heat storage material 12. Further, the heat transfer tube 13 is formed in a meander structure and is disposed entirely in the solid-liquid mixed heat storage material 12. As the solid-liquid mixed heat storage material 12, magnesia was used as the solid heat storage material and nitrate was used as the liquid heat storage material. The nitrate is 7% by weight sodium nitrate and 4%
It is a mixture of 9% by weight of sodium nitrite and 44% by weight of potassium nitrate. It is a liquid at 142 ° C. (melting temperature) or higher, but it solidifies at a temperature below this temperature to become a solid. When the nitrate is a solid, the specific gravity is 2.2.
However, when the temperature reaches 142 ° C. and melts, the specific gravity becomes 1.95, at which time the volume expands by about 13% and increases. Since this nitrate starts thermal decomposition at about 600 ° C. or higher, it must be used as a liquid heat medium at 142 ° C. or higher and 600 ° C. or lower. The solid-liquid mixed heat storage material 12 in the heat storage tank 11 is heated to a high temperature by the electric heater 14. When a demand for heat output is generated, a liquid such as water 15 is passed through the heat transfer tube 13, the water 15 exchanges heat with the high temperature solid-liquid mixed heat storage material 12, and the steam 16 flows inside the heat transfer tube 13. A high temperature fluid such as is generated and supplied to the outside. The steam 16 mixes with the tap water or exchanges heat with it to generate hot water, or the steam 16 is used as it is as a heating fluid.

The operation and embodiment of the heat storage tank 11 thus constructed will be described below. The high temperature heat storage tank 11 is used to store heat at 500 ° C., and the solid-liquid mixed heat storage material 12 is 100 ° C.
Heat input and output was repeated until heat was reached. When the temperature of the solid-liquid mixed heat storage material 12 is 100 ° C., the nitrate is in a solidified state, and when the electric heater 14 is energized and heating is resumed, the temperature rises from the vicinity of the electric heater 14. When the temperature exceeds 142 ° C., the nitrate becomes liquid. The volume of the liquid nitrate increases, but the increase in volume moves upward through the liquid portion of the surface of the electric heater 14 and is carried to the space space 18 above the solid-liquid mixed heat storage material 12.
Therefore, no large stress is generated in the heat storage tank 11. Therefore, the casing of the heat storage tank 11 will not be damaged during heat input.

2 and 3 show another embodiment of the present invention, FIG. 2 is a schematic configuration diagram thereof, and FIG. 3 is a diagram showing the relationship between the heat transfer tube group and the electric heater. In FIG. 2, a heat storage tank 21 is filled with a solid-liquid mixed heat storage material 22, and a heat transfer tube 23 and an electric heater 24 which is a heating source are arranged inside the heat storage tank 21. The electric heater 24 is installed inside the solid-liquid mixed heat storage material 22 through the space space 28 from the upper part of the solid-liquid mixed heat storage material 22 in the heat storage tank 21. The heat generating portion of the electric heater 24 is buried inside the solid-liquid mixed heat storage material 22. The heat transfer tubes 23 are formed in a meander structure and are arranged in the solid-liquid mixed heat storage material 22 mainly in the same direction as the electric heater 24 and so as to form a tube group as a whole. As the solid-liquid mixed heat storage material 22,
Magnesia was used as the solid heat storage material, and nitrate was used as the liquid heat storage material. In the heat storage tank 21 having such a configuration,
In this embodiment, when the electric heater 24 is arranged in the group of heat transfer tubes 23, it is arranged at a position sufficiently distant from the heat transfer tube 23. Here, the position sufficiently distant from the heat transfer tube 23 is sufficiently distant to absorb the volume expansion during the phase change of the heat storage material (nitrate) which is solid at normal temperature and rises in temperature to become liquid in the heat storage temperature range. This means a region where nitric acid begins to coagulate from the surface of the heat transfer tube 23 and the volume of nitric acid is reduced due to coagulation. FIG. 3 shows details of the positional relationship between the electric heater 24 and the heat transfer tube 23 group. The electric heater 24 is a heat transfer tube 23.
It is arranged in the central portion surrounded by a, 23b, 23c, and 23d. The solid-liquid mixed heat storage material 22 in the heat storage tank 21 is heated to a high temperature by the electric heater 24. Then, when a demand for heat output is generated, a liquid such as water 25 is passed through the heat transfer tube 23, and the water 25 exchanges heat with the high-temperature solid-liquid mixed heat storage material 22 to generate steam 26 inside the heat transfer tube 23. A high temperature fluid such as is produced and supplied to the outside for use.

According to the heat storage tank 21 of this embodiment, when heat is taken out, the electric heater 24 starts when solidification of all the nitrates starts from the nitrates near the surface of the heat transfer tube 23.
Voids occur in the vicinity. The volume occupied by these voids is about 13% of the total volume. The electric heater 24 is arranged in the void area of this 13% area. Therefore, the volume expansion when the solidified nitrate is melted again can be absorbed by the voids around the electric heater 24.
There is no limitation that 4 must be arranged inside the heat storage material 22 from the upper part of the solid-liquid mixed heat storage material 22 without fail.

A specific example using the heat storage tank 21 of this embodiment is shown below. 120 kg of magnesia and 45 kg of the mixture of nitrates described in FIG. 1 were used to fill the solid-liquid mixture heat storage material 22, and the vertical and horizontal pitches of the heat transfer tubes 23 were set to 70 mm. Was formed in a meander structure so as to form a heat storage tank 21 in which an electric heater 24 was disposed in a central portion surrounded by a heat transfer tube 23. The electric heater 24 is inserted into the heat storage material 22 from above the solid-liquid mixed heat storage material 22. This heat storage tank 2
Example 1 was repeated heat input / output at a temperature of the heat storage material 22 between 100 ° C and 500 ° C. As a result, the casing of the heat storage tank 21 was not damaged even when the heat input / output was 1000 times.

In the above embodiment, as the heat storage material which is solid at room temperature and becomes a liquid in the heat storage temperature range by raising the temperature,
Although the example of the mixture of nitrates consisting of sodium nitrate and sodium nitrite and potassium nitrate has been described, the present invention is not limited thereto. For example, a mixture of nitrates composed of sodium nitrate and potassium nitrate may be used.

[0019]

As described above, according to the heat storage tank using the solid-liquid mixed heat storage material of the present invention, a substance such as nitrate having a large volume change at the time of phase change such as solidification / melting is used as the heat storage material. Even if it is used as a heat storage tank, it is possible to provide a heat storage tank having a structure in which the casing is not damaged, and thus it is possible to provide a heat storage tank having a large heat storage capacity and good heat transfer characteristics.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of a heat storage tank using a solid-liquid mixed heat storage material according to the present invention.

FIG. 2 is a schematic configuration diagram of another embodiment of a heat storage tank using the solid-liquid mixed heat storage material according to the present invention.

FIG. 3 is a diagram showing a relationship between a heat transfer tube group and an electric heater in FIG.

FIG. 4 is a schematic configuration diagram of a conventional heat storage tank.

[Explanation of symbols]

 11 heat storage tank 12 solid-liquid mixed heat storage material 13 heat transfer tube 14 electric heater 15 water 16 steam 17 expansion tank 18 space space 21 heat storage tank 22 solid-liquid mixed heat storage material 23 heat transfer tube 24 electric heater 25 water 26 steam 27 expansion tank 28 space space

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Fumio Yoshiya, 4-33 Komachi, Naka-ku, Hiroshima City, Hiroshima Prefecture, Chugoku Electric Power Co., Inc. Sales Department (72) Tetsuyoshi Ishida 3-36, Takaramachi, Kure City, Hiroshima Prefecture Babcock-Hitachi Stock Company Kure Research Institute (72) Inventor Hidenori Hidaka No. 36 Takaracho, Kure City, Hiroshima Prefecture Babcock Hitachi Co., Ltd. Kure Research Institute (72) Nobuo Morimoto No. 36 Takaracho, Kure City, Hiroshima Prefecture Babcock Hitachi Kure Research Co., Ltd. (72) Inventor Yu Morikawa 6-9 Takaracho, Kure-shi, Hiroshima Babcock Hitachi Kure Factory (72) Inventor Tadayuki Fujiwara 2-6-2 Otemachi, Chiyoda-ku, Tokyo Babcock Hitachi Ltd.

Claims (3)

[Claims] 1. An electric heater, which is a heating source, is filled with a solid heat storage material and a heat storage material that is solid at room temperature and becomes a liquid in a heat storage temperature range, and is a heating source disposed between the heat storage materials, In a heat storage tank using a solid-liquid mixed heat storage material having a heat transfer tube into which a liquid is introduced, the electric heater is inserted into the heat storage material from above the heat storage tank. Heat storage tank using. 2. An electric heater, which is a heating source, is filled with a solid heat storage material and a heat storage material that is solid at room temperature and is heated to become a liquid in the heat storage temperature range. In a heat storage tank using a solid-liquid mixed heat storage material having a heat transfer tube into which a liquid is introduced, an electric heater arranged in the tube group of the heat transfer tube is solid at room temperature from the heat transfer tube. A heat storage tank using a solid-liquid mixed heat storage material, characterized in that the heat storage material is installed at a position sufficiently distant to absorb the volume expansion of the heat storage material that becomes liquid in the heat storage temperature range during the phase change. 3. The heat storage material according to claim 1 or 2, wherein the solid heat storage material is magnesia, and the heat storage material that is solid at room temperature and becomes a liquid in a heat storage temperature range is sodium nitrate, sodium nitrite and potassium nitrate. A heat storage tank using a solid-liquid mixed heat storage material, which is a mixture or a mixture of sodium nitrate and potassium nitrate.