JPS6034653B2 - Freezing method for cavities with insulation - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The disclosed technique belongs to a cooling/freezing technique in which a cavity formed inside a rock is used as a refrigerator for freezing through a heat insulating material attached to the inner wall surface of the rock.

Accordingly, the invention of this application attaches a heat insulating material to the inner wall surface of the rock of an underground cavity formed by excavating into the bedrock, and then cools the inside of the cavity to below freezing point, whereby the water content of the heat insulating material freezes. This relates to a method of freezing a cavity with insulation material to create an underground freezer or an underground refrigerator by freezing free water in the bedrock and forming it on the wall of an impermeable layer.In particular, it relates to a method of freezing a cavity with insulation material installed on the inner wall surface of the bedrock. We purposely bring the material into a supersaturated water-containing state and cool it below freezing, freezing the free water in the rock through the freezing state of the insulation material, and sublimating the frozen water content within the insulation material to restore its original insulation function. In addition, this method freezes the cavity by once melting the ice and increasing the temperature of the gas phase, liquid phase, and contact surfaces to further freeze and sublimate quickly. This is related.

As is well known, large stocks of marine products, livestock products, processed foods, etc. are essential not only in the production area but also in the distribution process, and in such cases, they are usually stored frozen or refrigerated depending on storage conditions. A storage method is used.

Generally existing freezers and refrigerators are so-called building-type above-ground structures, and therefore, they are subject to regulations for cooling efficiency design, land acquisition, landscape and pollution issues, etc. It is becoming impossible to build warehouses with

Therefore, recently, a technology has been developed to excavate a cavity of a set capacity in a predetermined appropriate rock mass, freeze the free water contained in the cavity enclosure within the rock mass to form an impermeable layer, and use the cavity as a freezer or refrigerator. It has been devised, and design research is underway to put it into practical use.

By the way, when forming such underground type freezers, etc., it is of course necessary to go through a pre-cooling freezing process to form a free water frozen layer as an impermeable layer, and on the other hand, when operating the freezer, etc. In order to save cooling energy, it is necessary to attach heat insulating material to the inner wall surface of the rock in order to suppress and slow down the growth and expansion of the frozen zone in the rock.

Although the pre-cooling and freezing process can be carried out as appropriate by operating a cooling device installed in the cavity, there are various problems in adding a heat insulating material at the same time as the pre-cooling and freezing process, and it is difficult to put it into practical use. It has become a bottleneck.

That is, there are basically two construction methods for adding the insulation material, one of which is the method of attaching the insulation material after pre-cooling. The free water in the surrounding bedrock is frozen to form a frozen layer.
After that, a heat insulating material is attached to the wall surface.

However, in this method, the insulation material is attached closely to the inner wall surface of the frozen rock, which has the disadvantage that the work is extremely difficult to do at low temperatures, and the work efficiency is poor, resulting in a long construction period and increased costs. Furthermore, there is a drawback that support itself is inhibited by freezing and support cannot be guaranteed.

On the other hand, in these two methods, contrary to the above method, insulation material is attached to the inner wall of the rock in advance and then frozen by cooling the cavity, but compared to the previous method, the insulation material is applied more accurately. There are advantages such as being able to assist in the field and having good work efficiency)
Immediately after attachment, the heat insulating material becomes wet due to water retention in the rock, and in the later stages of freezing, it becomes hydrated and frozen, resulting in a reduction in its insulation function. This had the disadvantage of requiring a large internal and external temperature gradient due to the insulation, and requiring an extremely long period of time for free water to freeze within the rock.

The purpose of the invention of this application is to solve the problems of the method of freezing a cavity with insulation material based on the above-mentioned prior art, and
An excellent insulation material that can freeze free water within the rock extremely quickly, restore the function of the insulation material over a long period of time, and enable efficient attachment work, benefiting the field of storage utilization in the energy industry. The aim is to provide a method for freezing cavities.

In order to solve the above-mentioned problems, the present invention according to the above-mentioned purpose attaches a heat insulating material to the inner wall surface of the rock of an underground cavity excavated in the bedrock, and then the heat insulating material is sprayed with water, etc. The material is made to contain water in a supersaturated state, and is frozen below the freezing temperature of the rock to freeze the rock as a highly thermally conductive solid. Depending on the frozen state, the frozen water sublimes and disappears, or melts and becomes a liquid phase. The gist is that a technical measure was taken to raise the ice level using a capillary tube against the gas phase, causing it to sublime again, quickly disappearing moisture content, and restoring the function of the insulation material. be.

In FIG. 1, an underground cavity 3 for a freezer is excavated in a bedrock 1 in a predetermined appropriate area using a conventional construction method in such a manner that the surrounding area is sufficiently hydrated with underground free water 2. In that case, the vertical shaft 4 is used both as a work shaft and as an elevator shaft for loading and unloading stored goods after completion, and is connected to the loading and unloading control building 5. Next, with the formation of the cavity 3, the overcoat part 6
A predetermined cooling device 7 is disposed so as to face the inside, and is connected to a control device 9 via a bush connection 8. Therefore, as mentioned above, in this much-desired invention, the first invention
As shown in Figures 1 and 2, the inner wall surface 10 of the rock mass 1 is lined with shotcrete 11 to form the inner wall surface, and the inner wall surface 12 of the shotcrete lining 11 is lined with polystyrene-based strong instant adhesive. Then, a nylon sponge 13 as a hydrophilic porous heat insulating material is heated and bonded.

Therefore, in the process of adding the heat insulating material 13, it is natural that moisture in the concrete lining 11 and free water in the rock 1 gushes out through the gaps in the concrete lining 11 and drains into the heat insulating material 13. This results in a wet state, which significantly deteriorates the heat insulation performance of the original dry state for the time being.

Of course, this state constitutes an active transitional step in the invention of this application, and is effective as it can omit the curing work and period of the concrete wall surface 12.

After all of the heat insulating material 13 has been supplemented, water is further absorbed into the heat insulating material 13 until it is in a supersaturated state by means of water discharging means or the like in the cavity.As shown in FIGS. 3a and 3b, the heat insulating material 13 is Sufficient water 14 is retained in the interstices of the tissue 13' such as a fiber matrix.

Of course, the substrate 13' itself also absorbs water, but in this state, the insulation performance of the insulation material 13 further deteriorates, but this is intentional and does not affect the insulation performance and function of the original dry state during operation. It doesn't affect anything.

For convenience of explanation, Figures 3a and 3b schematically show the structure and supersaturated water retention state of the heat insulating material 13 as a partial longitudinal section and cross section.

Next, when the cooling device 7 is operated to cool the inside of the cavity 3 to below freezing point, the above-mentioned heat insulating material 13 first cools down its supersaturated water retention water 14.
By freezing, it becomes solid and becomes a highly thermally conductive medium.

Therefore, the structure 13' of the heat insulating material 13 shown in FIGS. 3a and 3b
When the moisture 14 in between freezes, the air inside the cavity 3 is cooled down to below the freezing temperature of the rock 1 via the cooling device 7, and the air inside the cavity 3 is dried at a low temperature. The bedrock 1 is cooled and frozen by oxidation.

By the way, in general, as shown in Figure 6, if we take the water content w as the vertical axis and the sublimation time t as the axis, the theory is that the water content sublimates and decreases over time, drawing a reduction curve P that asymptotically approaches the saturated water content wo. known both physically and experimentally.

Therefore, the frozen water retained in the heat insulating material 13 starts to sublimate ice chips at a temperature below the freezing temperature of the rock 1 in the cavity 3.

In addition, since the sublimation rate of ice flake sublimation is reduced if the temperature is too low, it is desirable that the temperature be below the freezing temperature of the rock 1 and above the set temperature in order to speed up the sublimation rate.

Therefore, when sublimation due to freeze-drying begins, the frozen portion of the water contained in the entire cross section of the heat insulating material 13 shown in FIG. The ice pieces 14' begin to sublimate, and as the cooling time passes through the B process, C, and D processes, the heat insulating material 13
The ice pieces 14' inside the heat insulating material 13 are sublimated, and the sublimated ice pieces are collected by the cooling device 7, while finally all the ice pieces 14 inside the heat insulating material 13 are collected and collected as shown in process D in FIG. The degree of dryness reached the water vapor partial pressure at the freezing temperature in the cavity 3, and the dry heat insulating material 13 was attached at this water vapor partial pressure>
A similar state will occur, and therefore the insulation performance in that state will be restored.

The above embodiment follows the sublimation moisture content and time curve shown in Fig. 6, and is possible when there is time leeway, such as when the work is carried out concurrently with other work inside the cavity 3. However, the following is an example of an embodiment in which the insulation function is restored even earlier than the above embodiment due to various construction conditions such as construction period, work efficiency, and reduction in power cost.

That is, it has been found that the sublimation is directly proportional to the contact area of the open surface to the dry air and the flow distance of the open surface.

Therefore, assuming that the circulating air flow rate by the cooling device 7 is constant, it is better to expose the frozen ice pieces 14' on the inner surface of the cavity 3 of the heat insulating material 13 as much as possible. It can be seen that both the contact area and the flow rate of the passing air are faster than when the air is sublimated and searched inside.

Therefore, the ice pieces 14' that are sublimated and infiltrated inside the structure 13' of the heat insulating material 13 are melted and turned into a liquid phase by temporarily increasing the temperature inside the cavity 3, and the fine gaps in the structure 13' of the heat insulating material 13 are utilized. It is possible to promote sublimation by raising it to the inner surface of the heat insulating material 13 by capillary action and freezing it again by rapidly cooling the temperature inside the cavity 3, thereby increasing the amount of sublimation.

As shown in FIGS. 5 and 7, the ice pieces 14' inside the heat insulating material 13 undergo the first sublimation process P, from the inner surface as shown in the process E in FIG. As shown in Figure 7, starting along the sublimation curve P, → t,'
Due to the sublimation effect over time, the ice pieces 14' go deep inside the heat insulating material 13 as shown in FIG. 5E, and the sublimation rate gradually decreases. Therefore, the cooling device 7 is stopped for t2 hours, or the cavity 3 is actively flooded to melt the ice chips 14' in the heat insulating material 13 and undergo the liquid phase process Q. As a result, As shown in the process in FIG. 5F, the moisture 14 rises due to capillary action on or near the inner surface of the heat insulating material 13.

In that case, the insulation material 1 is determined by theoretical analysis and experiments in advance.
It goes without saying that the temperature rises to such an extent that only the ice pieces 14' in the rock 3 are melted and the frozen rock 1 does not thaw.

Then, at a later time, the cooling device 7 is operated again to cool the inside of the cavity 3 to below the freezing point, so that the melted water 14 in the heat insulating material 13 freezes again, and in order to cool it to below the freezing temperature of the rock 1, the process shown in FIG. As shown in the figure, sublimation starts again, and ice piece 1
4' is on the inner surface of the heat insulating material 13, therefore, the contact area with the dry air is wide and the air current is far away, so the second sublimation curve P2 is similar to the first sublimation curve P, as shown in FIG. and crosses the reduction part of the original sublimation curve P.

Then, after 2' hours, that is, when the sublimation has decreased below the set sublimation rate, cooling is stopped again and the heating melting process Q is started.
2, and then repeat the third sublimation process and the melting, freezing, and sublimation processes described above. Therefore, as shown in FIG. 7, each sublimation process Pn takes a rapid sublimation process similar to that P in FIG. It is possible to recover.

Note that the embodiments of the invention of this application are not limited to the above-mentioned embodiments, and various embodiments are possible, for example, in which the first frozen ice flake sublimation is continued for a considerable period of time, and then the temperature is increased to turn it into a liquid phase. Of course, the heat insulating material is not limited to nylon sponge.

Furthermore, it goes without saying that the invention of this application is applicable not only to freezers but also to refrigerators.

As described above, according to the invention of this application, when a cavity excavated in a bedrock is used as a refrigerator or a freezer, a predetermined heat insulating material is attached to the inner wall surface of the bedrock in advance in the construction process, and then the cavity is cooled. In the method of freezing a cavity that has a heat insulating material that freezes water from the surrounding seams in the bedrock through the heat insulating material, the above-mentioned attached heat insulating material is soaked with water to the extent that the joint is saturated and the cavity is cooled to below freezing. By doing so, basically the entire twilled insulation material is temporarily frozen and formed into a solid body with good thermal conductivity, and therefore, even though the insulation material is interposed,
The cavity and the bedrock form a kind of direct thermal connection, which has the excellent effect of rapidly freezing free water within the bedrock.

In addition, when a heat insulating material is installed on the shotcrete surface of the inner wall of the rock, the heat insulating material absorbs water due to moisture from the cracks or water content in the concrete, and the heat insulating function temporarily decreases, but this is due to sublimation at a later stage. It does not cause any problem directly because it is recovered by

Therefore, attaching the heat insulating material before cooling has the advantage of being easy to perform and having high installation accuracy.

By lowering the temperature of the insulation material freezing cavity to below the freezing temperature of the rock, the frozen ice pieces in the insulation material come into contact with the cooling dry air inside the cavity, undergo a sublimation action, and gradually reduce the content over time. Ice chips, that is, water content, can disappear from the insulation material and be collected in the cooling device, and the partial pressure can eventually be equal to that of saturated steam at a predetermined temperature in the cavity, that is, it can be in a dry state, resulting in dry insulation. It has a broken effect that can restore the insulation function similar to Zaizoejo.

Therefore, the cold energy during operation of a refrigerator or refrigerator is controlled by the heat insulating material, and it is possible to suppress the growth of the frozen zone in the bedrock.

Furthermore, the moisture content time curve during sublimation shows a decreasing curve, but after the ice flakes of the insulation material sublimate due to initial cooling, the air contact surface searches inside the insulation material structure and the sublimation rate decreases temporarily. The temperature inside the cavity is increased to increase the temperature of the insulation material, which melts the ice chips and turns them into a liquid phase, causing the liquid phase surface to rise to the gas phase surface due to capillary action with the tissue, thereby reducing the contact area and air flow. Attempt to recover, recover the sublimation rate, and repeat this process to quickly dissipate ice chips, that is, water content, in the insulation village, and quickly recover the dry insulation efficiency of the insulation material. There are excellent effects that can be achieved. Early functional recovery of the insulation material can provide excellent benefits such as improved workability and precision when installing the insulation material on the rock before cooling, as well as shortened construction time, reduced construction costs, and improved safety.

[Brief explanation of the drawing]

The drawings show embodiments of the invention of this application, and
The figure is a schematic explanatory diagram of an underground cavity, Figure 2 is a schematic explanatory diagram of insulation material addition, Figures 3a and 3b are partial longitudinal and cross-sectional schematic diagrams explaining the moisture content of the insulation material, and Figure 4 A, B, C, D. 5 is an explanatory diagram of the sublimation process of the first embodiment, FIGS. 5E, F, and G are explanatory diagrams of the repeated process of sublimation, liquid phase, and sublimation of other embodiments. FIG. 6 is an explanatory diagram of the water content time relationship of sublimation. FIG. 7 is an explanatory diagram of the relationship between sublimation, liquid phase, and sublimation water content and time. 1...Bedrock, 3...Cavity, 13...
...Insulation material, 2...Free water, 14...
・Water content, 14'...Ice pieces. Figure 1 Figure 2 Figure 3a Figure 3b Figure 4 Figure 5 Figure 6 Figure 7

Claims (1)

[Claims] 1. A cavity formed in a rock mass is cooled with a heat insulating material attached to the inner wall surface of the rock mass, and the rock mass surrounding the cavity is cooled through the heat insulating material. In the method of freezing free water in the rock, the insulation material is brought into a supersaturated water-containing state after installation, and then the water-containing insulation material is frozen by cavity cooling, and the freezing is continued to sublimate the ice chips in the insulation material. A method for freezing insulation cavities, characterized by drying the insulation material and restoring the insulation function of the insulation material. 2. A cavity formed in the rock mass is cooled with a heat insulating material attached to the inner wall surface of the rock mass, and the rock mass surrounding the cavity is cooled through the heat insulating material, so that the free water in the rock mass is cooled. In the method of freezing, the heat insulating material is brought into a supersaturated water-containing state after installation, and then the water-containing heat insulating material is frozen by cavity cooling to sublimate the frozen ice pieces in the heat insulating material, and after a predetermined period of time, the temperature inside the cavity is raised. After turning the frozen ice pieces inside the heat insulating material into a melting liquid phase and increasing the temperature of the gas-liquid contact surface, the cavity is cooled again to freeze and sublimate the water content, and the sublimation, melting and liquefaction are repeated. A method for freezing a cavity with a heat insulating material, characterized in that ice chips are sublimated from the heat insulating material to restore the heat insulating function of the heat insulating material.