JP7119579B2 - Heating device and temperature rising method for liquid content at normal temperature in frozen state - Google Patents

Description

TECHNICAL FIELD The present invention relates to an apparatus and method for raising the temperature of liquid contents at normal temperature in a frozen state, and more particularly, to a temperature below the freezing point of liquid contents at normal temperature in a frozen state. The present invention relates to a temperature raising device and a temperature raising method for efficiently raising temperature using a fluid medium having fluidity at .

In order to maintain the quality of foods and medicines that are liquid at room temperature for a long period of time, it is widely practiced to place them in a predetermined container and store or transport them in a frozen state.
For example, in the case of fruit and vegetable juices, by squeezing the juice at a place close to the production area of the fruit and freezing it, the quality of the fruit juice with excellent flavor and nutritional value can be extracted from the fresh fruits. It can be stored or transported as a frozen state without spoilage.
As a method for thawing such a frozen substance, conventionally, in addition to natural thawing and multi-stage frozen/refrigerated thawing, a method of thawing by application of hot air, a method of thawing by irradiating microwaves, and the like have been proposed.

As a food thawing method, a frozen food thawing method using sherbet ice as a thawing medium has also been proposed (Patent Document 1). This method uses fine ice, which has a large surface area and a higher thermal conductivity than water, to take away cold energy from the frozen product, enabling high-quality thawing in a short period of time.

JP 2016-154453 A

However, when a conventional thawing method such as natural thawing is used for a frozen product such as fruit juice that is liquid at room temperature as described above, the frozen product starts to melt from its surface, so a liquid boundary film forms on the surface of the frozen product. It is formed. When this liquid boundary film is formed, the heat transfer coefficient is extremely lowered, so that the temperature does not rise completely to the central portion, leaving a hard core. In addition, depending on the state of freezing, frozen products such as fruit juice may form areas with high juice concentration in the center and lower part, and freeze concentration may occur. is difficult to unzip. In addition, natural thawing requires a long time to completely thaw the entire frozen product, and during that time, there is a risk of quality deterioration such as putrefaction, oxidation, decomposition of the content components, and color change, and the quality deteriorates. There is also the problem of increased costs due to the disposal of such materials. Defrosting methods using hot air or microwaves can shorten the time, but they also require energy costs. Hot air has problems due to the boundary film on the surface of the frozen product, and microwave heating tends to cause partial overheating evenly. It is difficult to raise the temperature appropriately.

In addition, since the thawing method using sherbet ice described above adjusts the salt concentration and adjusts the temperature of the thawing medium to a temperature close to the freezing temperature of the frozen food, there is a limit to the container that stores the frozen food. . In other words, if the frozen product is stored in a metal container, there is a risk that the metal container will rust due to contact with the sherbet ice. Contamination may deteriorate the quality.
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above problems by using a fluid medium such as sherbet ice, which has fluidity at a temperature below the freezing point of the contents, and which is in a liquid state at room temperature in a frozen state. To provide a temperature raising device and a temperature raising method capable of uniformly and efficiently raising the temperature of the entire contents of a container.

According to the present invention, there is provided a temperature raising device for raising the temperature of contents that are in a liquid state at room temperature and are in a frozen state and that are contained in a metal container, wherein the temperature is below the freezing point of the contents. An outer container containing a fluid medium having fluidity, and a buffer member having a thermal conductivity equal to or higher than that of water, wherein the metal container is disposed inside the buffer member, and the buffer member There is provided a temperature raising device characterized in that heat is exchanged between the fluid medium and the frozen content via the fluid medium to raise the temperature of the frozen content.

In the temperature raising device of the present invention,
1. The fluid medium is sherbet ice made of salt water;
2. the buffer member is made of water and/or copper;
3. At least a portion of the buffer member is a copper container filled with water, the copper container is placed within the outer container, and the metal container is placed within the copper container;
4. An opening is formed in the upper part of the metal container, the opening is located above the interface of the fluid medium, and at least a part of the cushioning member is formed between the top surface and the top surface. a member comprising sidewalls depending from a perimeter, covering at least a portion of the opening of the metallic container, and a lower portion of the sidewall being immersed in the fluid medium within the outer container;
5. the metal container is made of steel;
6. a stirring device disposed within the outer container for stirring the fluid medium and equalizing the temperature of the fluid medium;
is preferred.

According to the present invention, there is also provided a temperature raising method for raising the temperature of contents that are in a frozen state and are liquid at room temperature, which are contained in a metallic container, wherein the metallic container is made of heat conductive material. is placed inside an outer container containing a fluid medium via a buffer material of water or more, and the fluid medium has a freezing point lower than that of water and flows at a temperature equal to or lower than the freezing point of the contents The fluid medium is a fluid medium having properties, and heat exchange is performed between the fluid medium and the frozen contents via the buffer member to raise the temperature of the frozen contents. A method of increasing temperature is provided.
In the temperature raising method of the present invention, it is preferable that the fluid medium is agitated by an agitating device provided in the outer container to equalize the temperature.

In the temperature raising apparatus and temperature raising method of the present invention, by using a fluid medium that has fluidity at a temperature below the freezing point of the liquid content at room temperature in a frozen state, the interface Since no boundary film that lowers the thermal conductivity is formed in the container, the fluid medium can efficiently remove the cold energy from the contents that are liquid at room temperature in the frozen state and raise the temperature.
Moreover, in the temperature raising device of the present invention, the metal container for containing the content that is liquid at room temperature in a frozen state and the fluid medium that has fluidity at a temperature below the freezing point are separated through the buffer member. Since the containers are in contact with each other, even when sherbet ice made of salt water is used as the fluid medium, there is no risk of deterioration damage such as rusting of the metal container or contamination of the contents with salt water.
In addition, since the buffer member is made of a material having a high thermal conductivity, it is possible to prevent loss of heat exchange between the fluid medium and the frozen contents.
Furthermore, the contents that are liquid at room temperature in a frozen state are heated to a desired temperature below the freezing point of the contents, so that the temperature is uniformly increased to the inside while maintaining the solid state, resulting in quality deterioration. There is no fear of
In addition, even if the frozen product has a concentration gradient, the temperature can be raised uniformly to the inside by freeze concentration.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows an example of the temperature raising apparatus of this invention, (A) is a top view, (B) is a sectional side view. It is a figure which shows another example of the temperature raising apparatus of this invention, (A) is a top view, (B) is a sectional side view. It is a figure which shows another example of the temperature raising apparatus of this invention, (A) is a top view, (B) is a sectional side view.

The temperature raising apparatus and temperature raising method of the present invention provide liquid contents at room temperature in a frozen state (hereinafter sometimes simply referred to as "contents") so that they become fluid at a temperature below the freezing point of the contents. It is based on the knowledge that the temperature of the contents in the frozen state can be efficiently raised by using a fluid medium having the above-described structure and performing heat exchange between the fluid medium and the contents in the frozen state. Therefore, this temperature raising operation can be performed efficiently without causing deterioration or damage to the apparatus or quality deterioration of the contents.
That is, when the contents that are liquid at room temperature in a frozen state are heated, if a boundary film with low thermal conductivity is formed at the interface of the contents, it is difficult to efficiently remove cold energy from the contents. However, in the present invention, it is possible to suppress the formation of such a boundary film by using a fluid medium having fluidity at a temperature below the freezing point of the contents. The fluid medium used in the present invention does not form a boundary film because the temperature difference between the fluid medium and the contents is small. Heat can be exchanged over an area, the temperature of the contents is not excessively raised, and the temperature of the contents can be uniformly raised while the contents are in a solid state, so there is no risk of quality deterioration.
In this specification, "freezing point" is the same concept as "freezing point" and "melting point". means the temperature at which it begins to melt. The freezing point can be measured according to JIS K 0065.
In addition, "cold heat" refers to negative energy that can be thought of as moving from a fluid medium with a relatively high temperature to a frozen product with a low temperature, while moving from a frozen product to a fluid medium. Say.

[Substances that are liquid at room temperature]
An object whose temperature is raised by the temperature raising apparatus and temperature raising method of the present invention is a substance that is in a liquid state at room temperature in a frozen state. When heated, a liquid film is formed at the interface, which makes it difficult to efficiently exchange heat. However, according to the temperature raising method of the present invention, the formation of the liquid film is suppressed, so the temperature can be raised efficiently. can do.
The term “liquid at room temperature” refers to liquid, gel, emulsion, etc., and it is sufficient that it has at least liquid and fluidity, and solid content may be present in this liquid.
The temperature raising device and temperature raising method of the present invention can be suitably used for substances that are liquid at room temperature and need to be stored or transported in a frozen state for quality maintenance, but are not limited to this. , fruit juice and other beverages, jellies, liquid eggs, mother's milk, medicines, blood and the like.
In the present specification, the term "frozen product" refers to a product that has been frozen after the content has been filled into a metal container such as a can.

[Fluid medium]
In the method for raising the temperature of the present invention, it is important that the fluid medium that exchanges heat with the frozen product has fluidity at a temperature below the freezing point of the substance to be heated, which is liquid at room temperature. be. That is, by having fluidity below the freezing point of the substance that is the object to be heated, it is possible to contact the object to be heated with a large contact area and efficiently exchange heat with the frozen product.
Such a fluid medium consists of sherbet ice (ice slurry), which is a solid-liquid two-phase mixture of fine ice and liquid (aqueous solution). Sherbet ice can store the cold heat taken from the frozen product as ice, and since ice has a large heat storage capacity and melting latent heat, the temperature of the sherbet ice can be kept constant, and the frozen product can be stably produced. It is possible to raise the temperature.
Salt (sodium chloride), sugar, urea, ethylene glycol, propylene glycol ethanol and the like can be exemplified as the solute of the aqueous solution of the fluid medium. Further, fine ice has a particle diameter of about several hundred μm.
In the present invention, a fluid medium having fluidity below the freezing point of the frozen product can be obtained by adjusting the ice filling rate of the sherbet ice and the type and concentration of the solute.

In the present invention, sherbet ice made of salt water, which can be safely used for food applications, can be preferably used as the fluid medium. For sherbet ice made of salt water, the temperature of the sherbet ice can be adjusted by appropriately changing the salt concentration and ice filling rate. That is, the temperature of the sherbet ice can be lowered by increasing the salt concentration and the ice filling rate.
The ice filling rate is desirably in the range of 5 to 30% in order to ensure suitable fluidity of the fluid medium. If it is less than 5%, the temperature retention function is poor, and if it exceeds 30%, the fluidity is insufficient, ice is likely to form on the surface of the frozen product, and heat transfer on the surface of the frozen product may be reduced. .

A method for producing sherbet ice from salt water at a desired temperature and ice filling rate will now be described. In general, the relationship between the salt concentration d (%) and the freezing point (melting point/freezing point) Te (° C.) is expressed by the following formula (1)
Te=−0.559d+0.000118d ² −0.000568d ³ (1)
is approximated by
First, determine the desired ice filling rate to ensure fluidity, and then determine the desired temperature for thawing the frozen product. Then, the salt concentration is obtained from the above equation (1) with the temperature being the freezing point (melting point/freezing point) of salt water, and salt water having the obtained salt concentration is produced.
For example, in order to set the temperature of sherbet ice to −1.5° C., if the ice filling rate is 30%, the salt concentration is 2.6% according to the above equation (1). Preliminarily produced sherbet ice is gradually introduced into the salt water while maintaining the salt concentration of the salt water, and salt is added and the sherbet ice is introduced until the temperature of the salt water drops to a desired temperature. Then, when the temperature of the salt water drops to the desired temperature, the amount of sherbet ice to be fed may be adjusted so as to achieve the desired ice filling rate.

Alternatively, the salinity concentration is obtained from the above formula (1), the initial salinity concentration is calculated when all the ice at the desired ice filling rate is water, and salt water having that salinity concentration is generated. For example, in order to set the temperature of sherbet ice to -1.5°C, when the ice filling rate is 30%, the final salt concentration is 2.6% from the above equation, and the final salt concentration is 2.6%. The initial salinity concentration is 1.8%. The temperature of the produced salt water is lowered to the freezing point of the salt water to produce ice until the desired ice filling rate is obtained.
In the case of ethanol, the above formula (1) is expressed as:
Te = -0.358d - ^0.00814d2 - ^0.0000788d3
and for ethylene glycol,
Te = -0.302d - ^0.00226d2 - ^0.000125d3
and for propylene glycol,
Te = ^-0.267d - ^0.00253d2 - 0.000138d3
is known to be approximated by

[Temperature raising device]
A temperature raising device of the present invention is a temperature raising device for raising the temperature of contents (frozen products) that are in a liquid state at room temperature and are in a frozen state, and are contained in a metal container. and a buffer member having a thermal conductivity equal to or higher than that of water, wherein the metal container is arranged inside the buffer member. and heat exchange is performed between the fluid medium and the frozen contents via the buffer member to raise the temperature of the frozen contents.
As described above, when sherbet ice made of salt water is used as the fluid medium, if the fluid medium comes into direct contact with the metal container containing the contents, the metal container may deteriorate due to rusting and the like. There is a risk that the quality of the contents may be impaired due to contamination with salt water, etc.
In the temperature raising device of the present invention, the deterioration and fluidization of the metal container described above are prevented by interposing a buffer member with high thermal conductivity without direct contact between the fluid medium and the metal container containing the contents. It is possible to effectively prevent contamination of the contents of the sexual medium.
Moreover, since the buffer member has a thermal conductivity higher than that of water, it is possible to achieve a heat exchange rate equivalent to that in the case where the fluid medium and the metal container are brought into direct contact with each other.

1A and 1B are schematic diagrams showing an example of a temperature raising device of the present invention, where (A) is a top view and (B) is a side sectional view. The temperature raising device, which is generally denoted by 1, comprises a cylindrical metal container 2 for containing contents, which has a bottom surface 2a and a side wall 2b, and four A buffer member 3 and an outer container 4 containing a fluid medium 5 arranged on the opposite side of the metal container 2 of each buffer member 3 are provided.
As is clear from FIG. 1B, the cushioning member 3 has a bottom portion 3a and side portions 3b so as to come into contact with the bottom portion 2a and side walls 2b of the metal container 2, and has an L-shaped side cross section. formed. The side portion 3b of the cushioning member is integrated with the outer container 4 and directly contacts the fluid medium 5 in the outer container to transfer the heat of the fluid medium 5. As shown in FIG. As a result, the buffer member 3 performs heat exchange between the metal container containing the content and the fluid medium. Heat is exchanged as efficiently as if the metal container were in direct contact with the fluid medium. Further, in this aspect, since the buffer member is interposed between the metal container and the fluid medium, there is no possibility that the fluid medium will enter the metal container, and the quality of the contents will not be impaired. is effectively prevented.
In the specific example shown in the figure, the buffer member 3 and the outer container 4 are movable in the radial direction of the metal container 2 (in the direction of arrow P in FIG. 1(A)), and the metal container filled with the contents can be easily installed and removed.

This aspect is not limited to the specific examples shown in the drawings, and various modifications are possible. For example, in FIG. 1, the buffer member was formed on one side of the outer container on the side of the metal container, but as shown in FIG. By forming a plurality of fins 6 protruding outwards to increase the contact area with the fluid member, the heat exchange efficiency can be further improved. Also, although a gap is formed between the adjacent cushioning members, it is possible to change the design such that a heat insulating material or the like is arranged so that the thermal efficiency of the cushioning member is not lowered. Furthermore, it is desirable that the contact surfaces of the metal container and the cushioning member are brought into close contact so as not to form a space, and if necessary, a cushioning material containing water can be used to ensure close contact.
Materials having thermal conductivity higher than that of water constituting the buffer member include metals such as copper, aluminum, brass, and stainless steel. Copper can be preferably used in order to prevent deterioration when using sherbet ice composed of ice. Also, in this embodiment, a steel container can be used because the metal container does not come into direct contact with the fluid medium.

2A and 2B are schematic diagrams illustrating another example of the temperature raising device of the present invention, where (A) is a top view and (B) is a side sectional view. The temperature raising device, which is indicated as a whole by 1, comprises a cylindrical metal container 2 consisting of a bottom surface 2a and a side wall 2b for containing contents, and a cushioning member 3 consisting of a container capable of accommodating the metal container 2 as a nest. and an outer container 4 in which the cylindrical container 3a can be installed and which contains a fluid medium 5.
The cushioning member 3 comprises a cylindrical container 3a made of a material having thermal conductivity higher than that of water, and when the metal container 2 is accommodated in the container 3a, the outer surface of the metal container 2 and the inner surface of the cylindrical container 3a consists of water or ice water that fills the space 3b formed between The buffer member 3 exchanges heat between the metal container 2 containing the contents and the fluid medium contained in the outer container 4. The buffer member 3 is a container having thermal conductivity higher than that of water. Since it is formed from 3a and water or ice water, heat exchange is performed efficiently.

In this embodiment, the cylindrical container 3a constituting the buffer member is formed higher than the liquid surface 5a of the fluid medium 5 contained in the outer container 4, and the fluid medium flows into the cylindrical container 3a. I have nothing to do. Further, the metal container 2 for storing the contents is made higher than the cylindrical container 3a constituting the buffer member in order to prevent not only the fluid medium but also water or ice water constituting the buffer member from flowing into the container. formed high.
In this aspect, the fluid medium in the outer container produces a temperature gradient in which the temperature near the interface with the cushioning member becomes lower than the temperature near the outer wall of the outer container over time. It is desirable to have a device for stirring or circulating the Thereby, the temperature of the fluid medium can be made uniform and the temperature of the contents can be efficiently raised.
In this embodiment, as in the embodiment of FIG. 1 described above, the metal container containing the frozen product does not come into direct contact with the fluid medium. material can be used.

3A and 3B are schematic diagrams illustrating another example of the temperature raising device of the present invention, where (A) is a top view and (B) is a side sectional view. The temperature raising device, which is generally denoted by 1, comprises a cylindrical metal container 2 consisting of a bottom surface 2a and side walls 2b for storing contents, a top surface 3a covering the upper part of this metal container 2, and from the top surface It comprises a lid-like cushioning member 3 consisting of a depending side wall 3b and an outer container 4 containing a fluid medium 5 in which a metal container 2 can be placed.
In this embodiment, an opening (not shown) may be formed in the upper surface of the metal container 2 to prevent the fluid medium 5 contained in the outer container from entering through the opening. , the metal container 2 is constructed to be higher than the liquid surface 5 a of the fluid medium 5 . For this reason, the upper portion of the metal container 2 that is not in contact with the fluid medium cannot exchange heat with the fluid medium. Since the lower part of the side wall 3b is immersed in the fluid medium 5, the heat exchange of the contents located in the upper part of the metal container can be performed to the same extent as when the contents are in contact with the fluid medium. can.

In this aspect, in order to prevent the temperature of the cushioning member from rising due to the ambient temperature, it is desirable to attach a heat insulating material to the outer surface of the top surface 3a of the cushioning member and the upper outer surface of the side wall 3b (the portion not immersed in the fluid medium).
In addition, since the metal container is directly immersed in the fluid medium, when sherbet ice made of salt water is used as the fluid medium, it is desirable that the metal container be made of a metal that does not easily rust, especially copper. It is desirable to become
Furthermore, the lid-shaped cushioning member shown in FIG. 3 can be used in combination with the cylindrical container 2a shown in FIGS. 1 and 2 described above.
Also in this embodiment, it is preferable to equip the outer container 4 with a device for stirring or circulating the fluid medium, similarly to the embodiment shown in FIG.

[Method of raising temperature]
The temperature raising method of the present invention uses the temperature raising device described above, and the liquid content (frozen product) stored in a metal container in a frozen state at normal temperature is made to flow at a temperature below the freezing point of the content. By using a fluid medium having a specific property and exchanging heat by bringing them into contact with the buffering member with thermal conductivity equal to or higher than that of water, the temperature of the contents is raised to a desired temperature below the freezing point. .
The target temperature for raising the temperature of the contents is determined according to the frozen state of the contents. It is desirable to aim for temperatures as low as 0°C. On the other hand, if the contents are freeze-concentrated, the outer part of the contents is ice with a lot of water, so in such a case, the freezing point of water, not the freezing point of the completely melted contents. Raise the temperature to the desired temperature below (0° C.). In that case, it is desirable to aim for a temperature about -0.5°C lower than the freezing point (0°C).

In the temperature raising method of the present invention, the smaller the specific surface area of the contents, the higher the heat transfer efficiency on the surface of the container. Although it depends on the type and shape of the frozen product, it is desirable to heat the product with a volume of 2 L or more.

In the temperature raising method of the present invention, the metal container filled with the contents is placed in the outer container containing the fluid medium of the temperature raising device shown in FIGS. It is preferable to raise the temperature to a state just before thawing. Phase conversion from solid to liquid requires a large amount of energy, but by stopping the temperature rise in the solid state immediately before thawing, the temperature rise time can be shortened without forming a liquid film on the surface of the frozen product, which improves efficiency. good. In addition, since the inside of the frozen product can be heated to a uniform temperature, no hard core remains inside the frozen product, and the frozen product can be easily handled after the temperature is raised. Moreover, since it is in a state just before thawing, quality deterioration can be prevented.
In addition, in the outer container filled with the fluid medium, a temperature gradient occurs over time in which the temperature near the interface with the frozen product becomes lower than the temperature near the outer wall of the outer container, so the fluid medium is stirred or circulated. It is desirable to Thereby, the temperature of the frozen product can be efficiently raised.

(Example 1)
An orange juice drink with a fruit juice concentration of 100% was filled in a steel container with a volume of 25 L (a cylinder with a diameter of 285 mm and a pail with a height of about 370 mm) and frozen at -40°C to obtain a frozen product. A thermocouple for temperature measurement is placed at the approximate center position of the frozen product in the steel container (160 mm from the upper end at the center position in the diameter direction) and at the outer part (25 mm away from the side of the container) at the center position in the height direction. was installed, and the temperature of the frozen product in the steel container was raised using the temperature raising device shown in FIG. The outer container contains sherbet ice (target temperature -1.5°C) made of salt water with a salt concentration of 2.6% and an ice filling rate of 30%. stowed. When the time required for the internal temperature of the frozen product to rise from -20°C to -10°C was measured, it was about 2 hours. Further, the temperature outside the frozen product at that time was -9°C, and the temperature difference from the temperature inside the frozen product was small, and the temperature could be raised uniformly.

(Comparative example 1)
The same frozen product as used in Example 1 was naturally thawed at room temperature of 15°C. After 2 hours, which is the heating time in Example 1, the center temperature was -25°C and the outside temperature was -20°C.

The temperature raising device and temperature raising method of the present invention raise the temperature of a frozen liquid content at room temperature contained in a metal container to a desired temperature below the freezing temperature of the content in a short period of time. In addition, since the metal container exchanges heat with the fluid medium through the buffer member, there is no risk of deterioration of the metal container or deterioration of the contents due to the fluid medium. It can be suitably used for thawing frozen products such as liquid eggs, medicines and blood.

1 heating device, 2 metal container, 3 cushioning member, 4 outer container, 5 fluid medium.

Claims (9)

A temperature raising device for raising the temperature of a liquid content at room temperature in a frozen state contained in a metal container,
An outer container containing a fluid medium having fluidity at a temperature below the freezing point of the content, and a buffer member having a thermal conductivity equal to or higher than that of water,
The metal container is arranged inside the buffer member, and heat exchange is performed between the fluid medium and the frozen content via the buffer member, thereby reducing the content in the frozen state. A temperature raising device characterized by raising the temperature. 2. A heating device according to claim 1, wherein said fluid medium is sherbet ice made of salt water. 3. The temperature raising device according to claim 1, wherein said buffer member is made of water and/or copper. At least a part of the buffer member is a copper container filled with water, the copper container is installed in the outer container, and the metal container is installed in the copper container. A temperature raising device according to any one of the above. An opening is formed in the upper part of the metal container, the opening is located above the interface of the fluid medium,
At least part of the cushioning member is a member consisting of a top surface and side walls hanging down from the periphery of the top surface, covering at least part of the opening of the metal container, and a lower part of the side wall The temperature raising device according to any one of claims 1 to 4, which is immersed in a fluid medium in a container. The temperature raising device according to any one of claims 1 to 5, wherein the metal container is made of steel. The temperature raising device according to any one of claims 1 to 6, further comprising a stirrer arranged in the outer container for stirring the fluid medium and uniformizing the temperature of the fluid medium. A temperature raising method for raising the temperature of a liquid content at room temperature in a frozen state contained in a metal container,
The metal container is placed inside an outer container containing a fluid medium via a buffer member having thermal conductivity equal to or higher than water, and the fluid medium has a freezing point lower than that of water and the contents A fluid medium that has fluidity at a temperature below the freezing point of the object, and is in a frozen state by performing heat exchange between the fluid medium and the frozen content via the buffer member. A temperature raising method characterized by raising the temperature of contents. 9. The temperature raising method according to claim 8, wherein the fluid medium is agitated by an agitating device provided in the outer container to uniformize the temperature.

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