RU2650005C1 - Method of cold accumulation in the ground - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: invention relates to the construction on permanently frozen soils and is intended for freezing and temperature stabilization of soil bases of buildings and structures. Technical result is achieved by a method of accumulating cold in the ground, which is carried out by removing heat from the ground around a two-pipe coaxial column by means of the circulation of the refrigerant, while using removable, of different functionality and universal attachments for removable attachments on a two-pipe column.

EFFECT: invention makes it possible under control to ensure a rapid freezing of the soil in the warm season, acceleration of the natural process of ground freezing and supporting its frozen state during the cold season.

13 cl, 5 dwg

Description

The claimed invention relates to the construction on permafrost soils and is intended to create year-round freezing and temperature stabilization systems for the soil foundations of buildings and structures.

A known method of cooling the soil by supplying a cooling agent that circulates through the coil of a gravitational heat pipe immersed in the soil. The circulation can be stopped or resumed, including under the control of an agent that responds to the temperature of the condensation zone (see RF patent No. 68108, IPC F28D 15/00, published on November 10, 2007).

The considered method is designed only for operation in a vapor-liquid (two-phase) circuit, i.e. with condensation and evaporation zones, moreover, between these zones, in the so-called transport zone, additional cooling of the coolant vapor is provided at an insufficiently cold ambient temperature in the condensation zone. The presence of additional equipment prevents the natural process of circulation of vapors and condensed refrigerant in the transport zone. All this limits the effectiveness of the technology, requires additional energy-intensive equipment and increases the cost of implementing the method.

A known method of cooling the soil, including the fan blowing cold air into the inner pipe in the casing, which then passes through the annulus between the casing and the inner pipe to the soil surface, or, conversely, when working according to the intake circuit, cold air from the soil surface through the annulus it is sucked into the casing and through the inner pipe enters the suction pipe of the fan. The inner tube at the end may have an ejection nozzle (see RF patent No. 2110647, IPC E02D 3/115, publ. 05/10/1998).

The disadvantage of this method is the narrow scope of applicability, the need to use external energy-intensive equipment and the difficulty of servicing the underground part of the device, including the ejection nozzle, which is at risk of possible clogging and freezing.

A known method for freezing the soil, which includes cooling the cold environment with liquid nitrogen. The cold carrier is cooled by a cold medium. Ethanol, butane, isobutane or propane are used as a cold medium. As a cold carrier use brine, synthetic saline or a mixture of aqueous glycol. The cold carrier is introduced into the soil mass through the pipe wall, where the cold is transferred from the cold carrier to the soil mass by the pipe wall (see patent EP2757199, IPC E02D 3/115).

The disadvantage of this method is the increased complexity of its implementation, because in addition to the need for a large number of energy-intensive equipment, control of the maintenance personnel is also required.

A common disadvantage of these methods is the use of energy-intensive equipment. The installation of energy-intensive equipment requires temporary foundations, which can also thaw permafrost soils (MMG), and this heat also needs protection, especially in the warm season. Maintenance of this equipment requires the presence of personnel, which is impossible for linear facilities in the environment of the MMG location, especially in the warm season. In addition, the implementation of such methods requires external power supply of sufficient power, which is also not always possible for extended linear objects.

Closest to the proposed method is a method of accumulating cold in the soil, which contains the steps of active and passive freezing of the soil by circulating the refrigerant in at least one column, inside which an inner pipe is installed to force the supply of refrigerated refrigerant from an external pump, and with the inner pipe removed natural circulation (see RF patent No. 2039861, IPC E02D 3/115, publ. July 20, 1995).

A significant drawback of this method is the difficulty of implementation, in which, for example, when switching from active to passive cooling mode, it becomes necessary to dismantle the inner pipe, and when using liquid refrigerant such as kerosene, environmental risks to the environment are not excluded. The disadvantage is the impossibility of organizing active cooling without energy-intensive equipment and the narrow scope of the method.

Based on the practice of freezing, maintaining or enhancing the frozen state of soil in the foundations of structures located at MMG, it is known that a period of active cooling in the warm season is desirable a year or two after construction. After this, as a rule, enough work of any of the known types of devices for thermal stabilization of soil (hereinafter - TSG) in the cold season, but preferably under the control of the freezing process. The best option would be to use TSG in the early years in active cooling mode in summer and passive in winter, but with the condition of low costs for its transfer from mode to mode, especially if there is a large amount of TSG in the facility in operation. It is at least difficult to evaluate the operating costs of the first two years, with the extraction of long inner pipes in the spring and installation back in the fall, and with coaxiality, with pumping and pouring kerosene, installing and removing pump-ventilation equipment and other works. And, in addition, for the implementation of the method, high-power electric power and protection of MMG from thawing caused by the operation of pumping and ventilation equipment are necessary.

The difficulties mentioned above have not led to the widespread use of known methods. In practice, they often use well-known designs and systems of TSG, as a rule, with a two-phase principle of operation, in which there is no control over the operation of TSG, especially in automatic mode, which leads to a number of unpleasant consequences. The criticism of single-phase TSH is largely justified due to a number of disadvantages, which the proposed method allows to overcome.

Thus, the prior art does not reveal a universal method and device, the use of which allowed to realize the principles of accumulation of cold in the soil, devoid of the above disadvantages.

The technical problem of the present invention is the creation of a method of accumulating cold in the soil, which allows for quick, if necessary, freezing of the soil in the warm season, acceleration of the natural process of freezing the soil and maintaining its frozen state in the cold season.

The technical result consists in proposing a method that provides a flexible controlled mode of soil freezing without energy-intensive equipment and without the thawing effect of this additional equipment on the soil.

The technical problem is solved in that in the method of accumulating cold in the soil, including active and passive freezing of the soil by circulating the refrigerant in at least one two-pipe coaxial column, buried in the soil, with the active freezing by forced circulation of the refrigerant, and in passive freezing by natural circulation of the refrigerant, and before the start of the freezing process, the closed circuit is evacuated and filled with refrigerant, according to the solution with active freezing In the warmer months, the refrigerant is injected into the central pipe of the column through a removable discharge two-pipe nozzle mounted on the column, the refrigerant is cooled by throttling; with active freezing in the cold season, the refrigerant is pumped through a removable discharge two-pipe nozzle into the central pipe of the column; with passive freezing in the cold season, a removable two-tube nozzle mounted on the column with external and internal fins is used, they provide natural refrigerant circulation in a closed loop - down the central pipe of the column, up to the volume between the central and external pipes, and then up the central tube of the nozzle, then between the central and outer tube of the nozzle down into the central tube of the column.

Further, in the text, the use of the term TSG implies a one-volume system consisting of a column, nozzle and, if necessary, an external pumping device.

In this case, by means of a pumping device is meant a device that provides the necessary level of refrigerant compression and contains control and management elements, including remote control, and in the case of an autonomous version, a power source and electric energy storage. The injection device may be external and provide the operation of several TSG. The number of TSG working from one pumping device is determined by the need and technological ability to maintain the tightness of the common closed loop of all TSG, especially if the refrigerant contains helium.

The removable two-tube discharge nozzle for active freezing may have external and internal fins. With active freezing in the warm and cold season, an injection device is placed inside or on it, and if necessary, additional attachment is provided to the nozzle itself. The nozzle may contain an autonomous power source with a storage battery, as a direct energy source use a solar battery and a wind generator. In this case, the operation of the pumping device is carried out for periods as the battery accumulates energy, and the nozzle and the pumping device provide anti-vandal protection.

The removable discharge two-pipe nozzle for the active freezing stage can be equipped with external and internal fins, which, together with similar fins of the column, provide atmospheric cooling of the refrigerant.

The removable two-tube nozzle for the passive freezing step further comprises an internal maze, the device of which is described below.

As a refrigerant, helium or a mixture of helium with gases with a quantitative helium content of at least 30% is used. For the circulation of the refrigerant during passive freezing, additional measures are provided for organizing the flow of the refrigerant using at least one valve installed in the nozzle.

The method provides for visual control of the tightness and safety of pressure inside the TSG, as well as remote control of the temperature of the refrigerant inside the central pipe of the column and between the central pipe and the body of the column. With active freezing, remote control of the electric current consumption of the discharge device is additionally organized.

If necessary, the TSG column casing is placed inside the foundation. With active freezing, the column casing or its lower part can be positioned horizontally or at an angle to the vertical. With active freezing of the arches, the column body is placed on the frozen arches, while the nozzle is placed in the lower part of the column.

The invention is illustrated by drawings.

In FIG. 1 schematically shows the principle of the implementation of the method of accumulation of cold in the soil according to the stage of active freezing in the warm season, according to the version equipped with an external pumping device and a nozzle equipped with external and internal fins.

In FIG. 2 schematically shows the principle of implementing the method of accumulating cold in the soil according to the passive freezing step.

In FIG. 3 is a section AA of FIG. one.

In FIG. 4 schematically shows the principle of the implementation of the method of accumulation of cold in the soil according to the step of passive freezing using a valve (fragment).

In FIG. 5 schematically shows the principle of implementing the method of accumulating cold in the soil by organizing a visual control of the tightness and preservation of pressure inside a closed refrigerant circuit (fragment).

The positions in the drawings indicate:

1. Two-pipe coaxial column;

2. Two-pipe nozzle;

3. External ribbing of the column;

4. Internal vertical fins of the column;

5. The flow of refrigerant;

6. Forcing device;

7. Throttling device;

8. The central tube of the column;

9. External finning of the nozzle;

10. Central pipe nozzles;

11. Internal vertical finning of the nozzle;

12. The valve;

13. Filling nozzle;

14. The signal element;

15. The membrane;

16. Cap.

The method of accumulation of cold in the soil is carried out in the form of stages that differ in the type of freezing (active and passive), while the stages of active freezing can be carried out year-round, and the passive freezing stage only in the cold season. The cold season is the period when the difference in temperature between air and soil provides the process of natural circulation of the refrigerant. The stages of the method are carried out by removing heat from the soil around a two-pipe coaxial column to the surrounding atmosphere using a refrigerant circulation, using replaceable nozzles of different functionality and universal mounting brackets on a two-pipe column.

At the stage of active freezing of the soil in the warm season (Fig. 1), the refrigerant 5 is throttled inside the central pipe 8 of column 1 due to the pumping device 6. The refrigerant 5 is cooled by the operation of the throttling device 7 and circulates in a closed loop through the central pipe 8 of column 1 downward, in volume, between the central pipe 8 and the column housing 1 upwards through the nozzle 2 to the blower 6, and then through the blower 6 and the nozzle 2 back into the central pipe 8 of column 1. Before the stage is completed, the total volume of mknutogo TSG circuit consisting of the nozzle 2, column 1 and the booster unit 6 is filled with refrigerant of 5 previously provakuumirovav. This stage allows, upon completion of the construction part and without waiting for the cold season, to freeze the soil. The use of helium 5 as a refrigerant or a mixture of helium with gases with a quantitative helium content of at least 30% can reduce the energy consumption of the method. The gas mixture should not contain water vapor or gases that contribute to the corrosion destruction of the TSG elements.

The stage of active freezing in the cold season eliminates the throttling operation, which allows the use of a pressure device 6, too, because its energy is spent only on the circulation of refrigerant 5. This stage allows maximum efficiency to use the cold season due to more intensive heat exchange of the soil with the atmosphere during forced circulation and additional cooling of the refrigerant 5 due to external and internal vertical fins (9, 11, respectively) of the nozzle 2 .

Thus, the discharge nozzle for the stage of active soil freezing:

- in the warm season, contains a throttling device 7, which provides a decrease in the temperature of the refrigerant 5, based on the Joule-Thomson effect. In an embodiment of the method with an autonomous power source and a storage battery, the operation of the pumping device 6 is carried out in periods when the battery accumulates energy and mainly in the dark, when the thermal effect from sunlight on the ground equipment of the TSG is minimal;

- in the cold season provides an additional reduction in the temperature of the refrigerant 5 due to heat transfer to the ambient air through the internal and external fins (11, 9, respectively) of the nozzle 2. The structural difference is the absence of a throttling device 7, which makes it possible to more efficiently use the power of the blowing device 6.

The passive freezing stage in the cold season (Fig. 2) allows, inter alia, using helium 5 and a helium-containing gas as a refrigerant, to circulate the refrigerant 5 naturally due to the difference in soil and air temperatures with greater efficiency. This, in addition to the well-known physicochemical properties of helium, is facilitated by the fact that the nozzle 2 has external and internal vertical fins (9, 11, respectively), as well as the fact that inside the nozzle 2 they change the locations of the ascending and descending flows of the refrigerant 5. Upward flow , which carries soil heat in volume between the central pipe 8 and the casing of column 1, passes into the central pipe 10 of the nozzle 2, passes through it to the top of the nozzle 2 and passes into the volume between the central pipe 10 and the body of the nozzle 2, where it gives off heat to the surrounding atmosphere e through the internal vertical and external fins (11, 9, respectively) of the nozzle 2 and passes into the central pipe 8 of column 1. Thus, a significant difference from the known methods of organizing the operation of single-phase TSG is the use for heat transfer from the soil to the refrigerant and from the refrigerant to the ambient air internal fins (11 and 4), respectively, nozzles 2 and columns 4. Moreover, inside the column 1, the internal fins 4 are located in those places in which this heat transfer is most appropriate - at the top, in the area of the external fins 3 and below, in the area of soil freezing.

The proposed method of improving heat transfer in the column and nozzle will create additional effects and will allow:

a) the implementation of natural circulation at a higher ambient temperature, which allows you to start the process of natural circulation earlier and end later;

b) it is not evenly cooled from the flow of refrigerant to the column body, which will create cooler local zones of the column;

c) reduce the size of the nozzle without decreasing the heat transfer efficiency.

If necessary, it is possible to additionally organize natural circulation from the use of at least one valve 12, which opens in the direction of the necessary movement of the refrigerant flow 5. As in the remaining steps, the change of nozzles 2 on column 1 is accompanied by evacuation of TSG and its subsequent filling with refrigerant 5.

The design feature of column 1, which is common to all stages of the method, is that it has an external, in the upper above-ground part and located above the snow level, heat-dissipating fins 3, as well as internal vertical fins 4 in the upper and lower parts of column 1. Internal vertical ribbing 4 of column 1 can be performed as a separate device (Fig. 3), consisting of two coaxially arranged cylinders connected by plates. Manufacturing material with good heat transfer. The inner diameter of the inner cylinder of the fins 4 should be larger than the outer diameter of the central pipe 8 so that the pipe 8 is located freely inside the fins 4. The contact of the fins 4 with the body of the column 1 should be as good as possible. For this, the fins 4 must enter the casing of column 1 as tightly as possible, and to improve the heat transfer it is possible to use a thermal paste chemically resistant to refrigerant 5. The main task of the internal fins 4 is to increase the heat transfer between the flow of refrigerant 5 and the casing of column 1 at the installation of the fins 4, additional - centering the pipe 8 inside the column 1.

Column 1 TSG for implementing the method, especially for the active freezing stages, can be installed in any direction from vertical to horizontal, and the lower part of the column can have an additional inclined or horizontal part, while the column itself can be an integral part of the foundation or foundation support, recessed into priming. Additional gravitational resistance to the movement of the refrigerant 5 is compensated by an increase in the power of the blowing device 6.

For applications of the method, for example, freezing arches to ensure their strength and waterproofness, column 1 is positioned higher than the nozzle 2.

Thermal separation of downward and upward flows provides low thermal conductivity of the walls of the central pipes (8, 10) of column 1 and nozzle 2, respectively, which is especially important in the natural circulation mode.

The implementation of the method at any stage, except for the well-known direct methods of monitoring the operation when using a pumping device, can be judged by indirect signs, for example, by monitoring the tightness of the TSG. To do this, the signal spring element 14 is extended from the nozzle body at a refrigerant pressure 5 inside the TSG above the minimum allowable due to the action of the flexible membrane 15 separating the volumes of the TSG and the atmosphere. When the pressure of the refrigerant 5 inside the TSH decreases below the minimum permissible spring, the spring overcomes the extruding action of the membrane 15, and the signal element 14 is recessed inside the nozzle body 2. In this case, the extendable part of the signal element 14 is protected by a transparent cap 16 from external influences (Fig. 5).

Remote control of the temperature of the refrigerant allows you to compare and analyze the temperatures of the refrigerant before and after heat transfer with the frozen soil, and when you take into account the ambient temperature, you can determine the temperature of the frozen soil, the performance of the TSG and, as an indirect indicator, the pressure of the refrigerant inside the TSG. Statistical analysis of the obtained data on temperature allows you to simulate the freezing zone of the soil and decide on the application of the corresponding steps of the present method. With active freezing, the indicator - current consumption of the injection device 6 - allows you to control the process of active freezing and provide the necessary actions to maintain the efficiency of the injection device, as well as protecting it from possible looting. The power source for remote control during active freezing is the power source of the refrigerant injection device, and in passive freezing it is a standard galvanic type battery, battery, solar panel, etc. Remote control data is transmitted in real time by known methods, for example, for objects of local location over wired and wireless networks of known types.

The operation of any TSH depends on the estimated amount of refrigerant involved in the heat transfer process, especially when it comes to a refrigerant such as helium. The advantage of using helium as a refrigerant is increased heat transfer and superfluidity, which distinguishes it from other gases and allows you to accelerate the process of accumulation of cold. Also, the use of helium will ensure competitive advantages of TSH based on the proposed method over the known two-phase and single-phase cooling devices, including due to the cost of helium. Therefore, the use of TSG on the basis of the proposed method will allow us to review the commonly used number of known TSG in the direction of reduction, and the universality of fastening and possible maintainability of nozzles in a warm room will allow you to implement a method with maximum economic effect.

Evacuation during seasonal changes of nozzles 2 will allow the use of helium or helium-containing gas during repeated recharges. In addition, helium is non-toxic, non-explosive and flammable, has no harmful effects on the environment, is more mobile and comparable in price to known refrigerants, and also eliminates internal freezing, corrosion and salt deposition inside the TSH. The disadvantage of helium, as well as its advantage, as applied to the proposed method, is its superfluidity, therefore, special attention must be paid to sealing the detachable connection of the nozzle and column when developing a device for implementing the proposed method. For example, for sealing, it is possible to use various known sealants, including thermally expanded graphite, and when transferred to a permanent passive freezing step, the joint is glued or scalded. The advantage of helium as a refrigerant is also that at any stage of the implementation of the method, the addition of helium to the closed circuit of the refrigerant circulation is easily carried out through the filling nozzle 13 (Fig. 4). Helium non-toxicity and non-explosive fire hazard allow this work to be carried out without affecting the operation of other equipment, for example, at a hazardous production facility.

Installation of column 1 in the ground during construction can be carried out with a technological plug instead of nozzle 2, which avoids difficulties and damage during subsequent construction work.

The proposed method will also be effective in situations where the thawing effect of the equipment on the installed foundation during operation is insignificant, and much more important is quick freezing after construction, for example, for transmission line supports or pipelines. In this case, after the necessary freezing of the soil, the discharge nozzle 2, as the most expensive TSG element, can be dismantled for reuse, and the cost of column 1 and refrigerant 5 (helium is environmentally friendly) can be neglected. This will avoid known situations where the uncontrolled use of known TSG leads to freezing of soils with subsequent expansion and displacement of foundations. Taking into account the prevailing practice, the proposed method will have significant economic benefits, especially when using well-known TSG with environmentally unsafe refrigerants.

The undoubted advantage of the method is that the transition from active to passive freezing is not associated with large financial and time costs for remounting nozzles 2. In addition, these works and the operation of TSG do not require the involvement of specialized organizations, their own trained personnel are sufficient. The injection nozzles of the active freezing stage after the transfer of TSH to passive freezing can be reused, which, for example, is convenient in the construction of linear objects.

Thus, the problem of the present invention is solved - the creation of a universal method of accumulation of cold in the soil, which allows for quick, if necessary, freezing of the soil in the warm season, acceleration of the natural process of freezing the soil and maintaining its frozen state in the cold season.

Claims (13)

1. The method of accumulation of cold in the soil, including active and passive freezing of the soil by circulating the refrigerant in at least one two-pipe coaxial column, buried in the ground, with the implementation of active freezing forced circulation, and in passive freezing - the natural circulation of the refrigerant, while before starting the freezing process, the closed circuit is evacuated and filled with refrigerant, characterized in that during active freezing in the warm season, the refrigerant is pumped into the center column through a removable discharge two-pipe nozzle on the column, cool the refrigerant by throttling, with active freezing in the cold season, the refrigerant is pumped through the removable discharge two-pipe nozzle inside the central pipe of the column, when passively freezing in the cold season, use a removable two-pipe inner nozzle with an external by fins, they ensure the natural circulation of the refrigerant in a closed circuit - down the central pipe of the column, in volume between the central the pipe and the column body up, and then up the central nozzle pipe, then between the central pipe and the nozzle body down into the central column pipe. 2. The method according to claim 1, characterized in that the removable discharge two-tube nozzle for active freezing is equipped with external and internal fins. 3. The method according to claim 1, characterized in that the walls of the central pipes of the nozzles and columns are made of a material with low thermal conductivity or have a coating of a material with low thermal conductivity. 4. The method according to claim 1, characterized in that during active freezing in the warm and cold season, the removable two-pipe discharge nozzle is equipped with a discharge device with control elements, and the nozzle provides additional fastening. 5. The method according to p. 4, characterized in that the nozzle additionally contains an autonomous power source with a storage battery, solar batteries and a wind generator are used as direct energy sources, while the operation of the discharge device is carried out periodically as the battery accumulates energy, while the nozzle provide anti-vandal protection. 6. The method according to claim 1, characterized in that helium is used as the refrigerant. 7. The method according to claim 1, characterized in that a mixture of helium with gases with a quantitative helium content of at least 30% is used as a refrigerant. 8. The method according to claim 1, characterized in that for the circulation of the refrigerant during passive freezing provide for the organization of the flow of refrigerant using at least one valve installed in the nozzle. 9. The method according to claim 1, characterized in that they carry out visual control of the tightness and preservation of pressure inside the closed circuit of the refrigerant circulation. 10. The method according to claim 1, characterized in that they carry out remote control of the temperature of the refrigerant inside the central pipe of the column and between the central pipe and the casing of the column, and with active freezing, they organize remote control of the current consumption of the discharge device. 11. The method according to claim 1, characterized in that the column housing is placed inside the foundation. 12. The method according to claim 1, characterized in that with active freezing, the column housing is positioned horizontally or at an angle to the vertical. 13. The method according to claim 1, characterized in that with active freezing, the column housing is located on the arches, while the nozzle is located in the lower part of the column.

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