RU2621912C2 - Method of cooling underground structures in masses of permafrost rocks and device for its implementation - Google Patents

Abstract

FIELD: mining.

SUBSTANCE: method of cooling underground constructions in masses of permafrost rocks includes the accumulation of cold in the upper part of the frozen soil masses in the winter season through a seasonally operating air cooling device. Underground construction is located at a depth, which is determined by the formula:

,

where h₁ - the depth of seasonal thawing of soils, in the sole of which there are pipes of the cooling device, m; τ - duration of the cooling device operation in the cold season (taken equal to the time delay of the temperature wave at the depth of the underground construction location) per season, h; λ and C - the average values of the thermal conductivity coefficient, W/(m⋅K⋅), and the volumetric heat capacity of the soil, J/(m³⋅K), in the roof of the underground structure; T - the amplitude of external air temperature fluctuations, K. The device for year-round cooling underground constructions in masses of permafrost rocks includes two independent air cooling devices, each of which includes, at least, one horizontal cooling pipe in the ground and, at least, two vertically oriented tubes that protrude above the surface of the earth. Internal volumes of vertical and horizontal pipes are connected. At least, one horizontal cooling pipe of one cooling device is laid in the ground close to the side wall of the underground construction at the mid-height level, and, at least, one horizontal cooling pipe of the second cooling device is laid in the bottom of the seasonal thawing layer.

EFFECT: increasing the reliability, reducing energy costs, increasing the autonomy of cryogenic storage and ensuring low negative temperatures in underground constructions throughout the year.

4 cl, 2 dwg

Description

The invention relates to mining thermal physics and is intended for cooling in the warm season of underground structures built in the thickness of permafrost rocks.

The well-known "METHOD OF THERMOSTATIC STORAGE OF PRODUCTS AND THERMOSTATIC STORAGE OF PRODUCTS", RU 2052740 [1], by supplying atmospheric air in the cold season to recharge the cold accumulator located in the ground and pumping refrigerant through a closed cavity located in a closed circulation loop storage air is conducted in a soil layer close to its thermal boundary, with the formation of a cold reserve in the form of a lithospheric ice-ground mass using ground moisture, and ithout last compulsorily continue feeding the air and the refrigerant cooling before pumping in the storage array are in ldogruntovom.

The disadvantages of the known design are the high complexity and cost of construction and high energy costs to maintain low temperatures in the storage.

It is known "DEVICE FOR STORAGE OF AGRICULTURAL PRODUCTS", RU 2023383 [2], including an underground structure, at least one horizontal pipe in the ground and at least one vertically oriented pipe protruding above the surface of the earth, and the internal volumes of the vertical and horizontal pipes are connected.

The known design can drastically reduce operating energy costs and increase the reliability of the storage compared to [1].

A disadvantage of the known design is the high complexity and cost of manufacturing heat pipes with thermal compensators and coolant, low reliability of the device and the inability to obtain significant negative stable temperatures. In addition, the disadvantage is the laboriousness of temperature control, due to the need for installation and dismantling of removable insulation, leading to wear of the insulation and the need for periodic replacement, which in turn leads to increased operating costs and the lack of autonomy of the storage.

The technical result of the invention is to increase reliability, reduce energy costs, increase the autonomy of the cryogenic storage and ensure low negative temperatures in underground structures throughout the year.

The technical result is achieved by the fact that in summer the cooling method of underground structures in the permafrost massif is characterized by the accumulation of cold in the upper part of the frozen ground massif in winter by means of a seasonally operating air cooling device, while the underground structure is located at a depth ensuring this the depth of the first temperature wave from the pipes of the cooling device at the moment of termination of the circulation of cold air, which calculated by the formula:

Where

h ₁ - the depth of seasonal thawing of soils, in the sole of which are located the pipes of the cooling device, m;

τ - the duration of the cooling device in the cold season (taken equal to the time delay of the temperature wave at the depth of the underground structure) for the season, h;

λ and C are the average values of the coefficient of thermal conductivity, W / (m⋅K), and volumetric heat capacity of soils, J / (m ³ ⋅K), in the roof of an underground structure;

T is the amplitude of the outdoor temperature, K.

The width of the strip of horizontal cooling pipes is determined from the equality B = 2 (h ₂ -h ₁ ) + in, and the number of pipes n = B / l, in - the width of the underground structure; l is the distance (step) between the pipes, determined by the heat engineering calculation.

A device is also proposed for cooling in summer the underground structures in the permafrost massif, which includes two independent air cooling devices (OU-1 and OU-2), each of which includes at least one horizontal cooling pipe in the ground and at least two vertically oriented pipes protruding above the surface of the earth, and the internal volumes of vertical and horizontal pipes are connected, with at least one horizontal cooling pipe of one cooling device (OU-1) laid in the ground close to the side wall of the underground structure at the level of the middle of its height, and at least one horizontal cooling pipe of the second cooling device (OU-2) is laid at the base of the seasonal thawing layer (on the upper surface of the permafrost layer).

The number of vertically oriented pipes can be four, with each pipe having its upper end in communication with the atmosphere, the lower ends of the vertically oriented pipes are each connected to their own collector, two of which are located at the depth of the seasonal thawing layer, the other two are located next to the cooled room at the level of its middle heights, horizontal parallel pipes are located between the respective collectors, the cross-sectional areas of the vertical pipes are equal to the cross-sectional areas collectors. The specified implementation will provide maximum cooling of horizontal pipes and the surrounding soil pipe in the winter.

The upper end of one vertical pipe extending from the collector is located above the height of the maximum snow cover, the second pipe extending from the collector opposite to the mentioned one is located at a height of 3-5 m from the surface of the earth. The different height position of the upper ends of the pipes will ensure the difference in air pressure to obtain stable convection of air in the cold season.

In winter, the circulating cold air in the horizontal pipe ОУ-1 cools the underground structure and accumulates cold in the surrounding frozen rocks for partial cooling of the underground structure in the summer. The main cold for summer cooling of the underground structure is accumulated in the upper layers of the permafrost mass using a series of horizontal pipes OU-2 located at the base of the seasonal thawing (thawing) layer, through which cold air moves, and the underground structure is located at a depth at which the cold temperature waves from the OU-2 horizontal cooling pipes enter the underground structure throughout the summer, and the initial cold temperature wave reaches the underground structure at the time termination of its winter cooling period, defined by formula (1).

In FIG. 1 is a schematic cross-sectional view, FIG. 2 shows a top view of an air cooling device for implementing the method, where

1 - vertical pipe for the downward flow of cold air OU-1;

2 - horizontal cooling pipes OU-1;

3 - vertical pipe for the upward flow of air OU-1;

4 - collectors OU-1;

5 - vertical pipes for the downward flow of cold air OU-2;

6 - horizontal cooling pipes OU-2;

7 - vertical pipes for the upward flow of air OU-2;

8 - collectors OU-2;

9 - vertical shaft service and loading shafts;

10 - underground structure;

11 - lower boundary of the seasonal thawing layer;

12 - the depth of the seasonal thawing layer;

13 - the width of the underground structure;

14 - the distance between the horizontal pipes OU-2.

Convective action air cooler ОУ-1 contains two cooling metal pipes 2 horizontally located near the underground structure 10, and two metal collectors 4 and two vertical pipes connected to them for downward air flow 1 and for upward air flow 3 connected to the collectors .

Convective action air cooler ОУ-2 contains a number of cooling metal pipes 6 horizontally located at the base of the seasonal defrosting layer 11, and metal collectors 8 and two vertical pipes connected to them for downward air flow 5 and for upward air flow 7 connected to collectors .

The total cross-sectional area of the OU horizontal cooling pipes is equal to the cross-sectional area of the collector and the vertical pipe. OU vertical pipes rise above the earth's surface: for downward air flow 1 and 5 to the maximum snow depth, for upward air flow 3 and 7 - 3-5 m. Exhaust vertical pipes 3 and 7 are made of material with low thermal conductivity or insulated metal.

Underground structure 10 is located at a depth of h ₂ defined by formula (1).

In the service and loading shafts 9 there is equipment for lowering and lifting personnel and cargo, placing electric cables and other equipment. The distance 15 between the horizontal pipes ОУ-2 is calculated by thermotechnical calculations based on the width of the underground structure 13 and the depth of seasonal thawing 12.

The device operates as follows.

When atmospheric air temperature drops below the soil temperature directly around the horizontal pipes 2 ОУ-1 and 6 ОУ-2 under the influence of the pressure difference of the air columns at the base of the vertical pipes 1 and 3 ОУ-1, 5 and 7 ОУ-2, cold air moves through the collectors 4 ОУ-1 and 8 ОУ-2 along horizontal pipes 2 ОУ-1 and 6 ОУ-2, cooling the surrounding soils. Seasonal operation of cooling devices stops when the temperature of the air rises above the temperature of the cooled soils around horizontal pipes 2 and 6.

Horizontal pipes 2 ОУ-1, located in the ground close to the side wall of the underground structure 10 at the level of the middle of its height, cool it and accumulate cold in the surrounding frozen rocks during the cold period for partial cooling of the underground structure in the summer. The main cold for summer cooling of the underground structure 10 is accumulated in the upper layers of the permafrost mass using horizontal pipes 6 OU-2. The first temperature wave from the cooling pipes 6 located at the base of the seasonal thawing layer at a depth of h ₁ reaches an underground structure 10 located at a depth of h ₂ after a period of time δ equal to the duration of the operation of the cooling devices and cold temperature waves from the array cooled in winter time frozen rocks in the underground structure continue to flow throughout the summer. The duration of the cooling OU-2 must be at least 6 months. This limits the use of the proposed device by climatic factor.

The technical result - increased reliability - is achieved by the use of widespread and sufficiently strong metal horizontal and vertical pipes, without a special coolant and the need for complete sealing with temperature compensators, which significantly reduce the reliability of the device. Increased reliability is also achieved by the absence of pressure or ventilation equipment and, accordingly, the absence of ballasts, powered by an external power supply, which has a non-zero probability of failure. The technical result is a reduction in energy costs due to automatic cooling of the soil adjacent to horizontal pipes in the winter without special pressure devices, while ensuring significant negative stable temperatures. The technical result - increasing the autonomy of the cryogenic storage - is ensured by the possibility of automatic operation of the cooling system without the obligatory participation of a person, which further reduces operating costs for maintaining the cryogenic storage.

Industrial application

The method and device were implemented during the construction in Yakutsk of the world's first Federal cryostorage of plant seeds, based entirely on the use of natural cold without the use of pressure mechanisms. In winter, the rock mass surrounding the cryostorage is cooled with the help of an air convective device, the horizontal channels of which are laid behind the roof of the structure. For summer cooling, horizontal pipes are connected by collectors, laid in trenches dug to the upper surface of permafrost rocks above the cryogenic storage and covered with soil. Collectors are connected to vertical pipes for downward and upward flows of atmospheric air.

Claims (10)

1. The method of cooling in summer the underground structures in the permafrost massif, characterized by the accumulation of cold in the upper part of the frozen ground massif in the winter by means of a seasonally operating air cooling device, while the underground structure is located at a depth ensuring the achievement of this depth of the first temperature wave from the pipes of the cooling device at the time of termination of the circulation of cold air, which is determined by the formula:

, Where h ₁ - the depth of seasonal thawing of soils, in the sole of which are located the pipes of the cooling device, m; τ - the duration of the cooling device in the cold season, h; λ and C are the average values of the coefficient of thermal conductivity, W / (m⋅K), and volumetric heat capacity of soils, J / (m ³ ⋅K), in the roof of an underground structure; T is the amplitude of the outdoor temperature, K. 2. The summer cooling device of underground structures in the permafrost massif, including two independent air cooling devices, each of which includes at least one horizontal cooling pipe in the ground and at least two vertically oriented pipes protruding above the surface of the earth, with internal volumes vertical and horizontal pipes are connected, while at least one horizontal cooling pipe of one cooling device is laid in the ground close to the side wall At the bottom of the underground structure at the level of the middle of its height, and at least one horizontal cooling pipe of the second cooling device is laid at the base of the seasonal thawing layer. 3. The device according to claim 2, characterized in that the number of vertically oriented pipes is four, with all the pipes having upper ends communicating with the atmosphere, the lower ends of the vertically oriented pipes being connected each to its own collector, two of which are located at the depth of the seasonal defrost layer, the other two are located in the ground close to the side walls of the refrigerated room at the level of the middle of its height, horizontal parallel pipes are located between the respective collectors, the area is transverse cross sections of vertical pipes are equal to the cross-sectional area of the respective collectors. 4. The device according to claim 2, characterized in that the upper end of one vertical pipe extending from the collector is located above the height of the maximum snow cover, the second pipe extending from the collector opposite to the aforementioned one, located at a height of 3-5 m from the ground .

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