RU168171U1 - DEVICE FOR COOLING SOIL WITH LOCAL THERMAL STABILIZATION AREA - Google Patents

Abstract

The utility model relates to the field of construction and operation of structures in areas with difficult engineering and geocryological conditions, namely, thermal stabilization of permafrost and soft soils. The technical result of using the utility model will be to increase the efficiency of the heat stabilizer in cooling the soil and the possibility of creating a given temperature field in the soil configuration. The claimed result is achieved in that the thermostabilizer contains a gravitational heat pipe having a a meticulous case, made with the possibility of refueling with a coolant, a housing comprising a condenser and an evaporator, and at least a part of the surface of the evaporator is coated with an insulating layer, the thickness of which does not exceed 3 mm and the thermal conductivity of its material is not higher than 0.01 W / m ° C.

Description

The utility model relates to the field of construction and operation of structures in areas with difficult engineering and geocryological conditions, namely, the thermal stabilization of permafrost and soft soils.

Known devices for cooling the soil (thermostabilizers) made in the form of a gravitational heat pipe containing a sealed case partially filled with coolant with evaporation, condensation and transport zones (Abrosimov A., Zaletaev S. Soil coolers. Designs and calculation methods, Palmarium Academic Publishing, 2012 ) The evaporation zone (heat supply zone) is located in the ground, and the condensation zone (heat removal zone) and the transport zone are outside, in the air. The transport zone starts at ground level and ends at the entrance to the condensation zone. The cooler body in the evaporation zone and the transport zone is usually made in the form of a smooth-walled cylindrical pipe and can be referred to by the general term evaporator. In the condensation zone, the pipe has fins to increase the area of heat exchange with the surrounding space, and this part can be called a condenser as a whole. In the upper part of the condenser, a valve is usually located, which serves to evacuate the internal volume of the body, refuel the coolant, remove non-condensed gases, measure pressure, etc.

The disadvantages of such devices include heat loss in the transport zone and heat dissipation in the upper layers of the soil, which generally leads to a decrease in the efficiency of the thermostabilizer.

To solve this problem, use the external insulation of the pipe in the transport zone or the design of coolers in which there is no contact of condensate with the wall of the housing in the transport zone, the so-called anchor-type coolers (RF patents №2327940, 2349852). In an anchor-type cooler, condensate flows down the axial tube and does not contact its wall. In this case, the condensate enters the zone of excess condensate, having a minimum temperature. For the same reason, the greatest heat removal from the soil is achieved in the lower part of the cooler. The soil near the end of the cooler has a minimum temperature and forms a chilled block (“anchor”).

Another problem of using a thermal stabilizer arises when it is operated in difficult geocryological conditions on multilayer heterogeneous soils, when it becomes necessary to vary the degree of soil freezing at different depths.

For example, the presence at a certain depth of a clay layer saturated with moisture during freezing can lead to heaving of the soil and bulging of the heat stabilizer.

In part, this problem can be solved by installing a heat-insulating coating and a heat connector on the connecting heat pipe (in the transport zone) or by making a heat pipe from a heat-insulating material (RF patent No. 2083762). This prevents the dispersion of the heat flux in the upper layers of the soil and eliminates the heat loss of condensate on its way to the reclaimed zone. To regulate the depth of the soil heat exchanger (reclamation zone), the heat pipe can be made in the form of a corrugated sleeve. The change in the length of the heat pipe is carried out by longitudinal compression or stretching, followed by fixation. The heat pipe can also be made in the form of a flexible cross-section of the sleeve, bent during installation.

This solution is technologically complex (since it provides for a tight connection of dissimilar materials), it does not allow to ensure sufficient reliability and efficiency of the device. The presence in the device for cooling the soil of sections of various diameters, besides not having sufficient rigidity, will cause difficulties when it is installed in the well. In addition, the device provides for thermal insulation of only the upper (with respect to the evaporator) soil layers (although in practice alternation of zones of increased and decreased soil cooling is often required).

The device, made in accordance with the claimed utility model, is not inferior to well-known soil coolers working on the principle of a gravitational heat pipe in terms of manufacturability, ease of transportation and installation in a well (A. Abrosimov, S. Zaletaev S. Soil coolers. Designs and calculation methods, Palmarium Academic Publishing, 2012). Moreover, it surpasses them in operational efficiency and allows you to create a given map of the distribution of temperature fields in the soil.

The technical result of using the utility model will be to increase the efficiency of the thermostabilizer in cooling the soil and the possibility of creating a temperature field in the soil of a given configuration.

The claimed result is achieved in that the thermostabilizer contains a gravitational heat pipe having a sealed housing capable of refueling with a heat carrier, a housing including a condenser and an evaporator, and at least a part of the surface of the evaporator is coated with an insulating layer, the thickness of which does not exceed 3 mm and thermal conductivity its material is not higher than 0.01 W / m ° C.

The thickness of the coating layer should be minimally necessary so that on the one hand there are no additional obstacles when the evaporator is brought into the well, on the other hand, sufficient thermal insulation is provided. The nature of the soil layers, the depth of their occurrence at the construction site and the location of the heat stabilizers is determined before the start of construction during exploration. The corresponding heat-insulating coating in the required places of the evaporator can be formed at the factory (making equipment for a specific construction site), or on the spot before installing the heat stabilizer.

The coating is usually formed in the form of rings. The coating itself must have good adhesion to various materials (aluminum alloys, steel), be wear-resistant, and be chemically inert and hydrophobic. For these purposes, it is preferable to use liquid ceramic thermal insulation, for example: KORUND and its modifications (RF patent No. 2502763). Such a coating has a thermal conductivity of up to 0.002 W / m ° C, and a sufficient layer thickness may be less than 1.5 mm. In the described utility model, other materials having suitable properties can also be used (for example, materials described in RF patents No. 2251563, 2311397, 2374281). Similar coatings can be used for thermal insulation of the evaporator in the transport zone and in the upper layers of the soil. All sections of the thermal insulation coating on the evaporator are preferably applied in a single process cycle from the same materials. However, if necessary, coatings in different areas of the evaporator may differ from each other in thickness and / or thermal conductivity.

The inventive utility model can be used with heat stabilizers (soil coolers in the form of a gravitational heat pipe) of various types: with a steel small-sized evaporator, with an evaporator with bellows connections, with a long-sized evaporator from easily deformable aluminum alloys, with a single-tube and multi-tube condenser, with a collector evaporator .d.

The essence of the claimed utility model is illustrated by the following drawings:

In FIG. 1 shows a thermal stabilizer with thermal insulation of the transport zone and certain sections of the evaporation zone.

In FIG. 2 shows a thermal stabilizer with a triple star condenser buried in the ground.

Thermostabilizer (soil cooler) is an extended tight sealed case filled with liquid heat transfer medium (Fig. 1), having an evaporation (heat supply) zone 1, a condensation (heat removal) zone 2 and a transport zone 3 between them. The heat supply zone 1 is located in the soil 4, the heat removal zone 2 and the transport zone 3 are in the air, the latter starting at the ground level and ending at the entrance to the condensation zone.

Structurally, a thermostabilizer, made in accordance with the claimed utility model, usually contains: an evaporator 5, made in the form of a smooth-walled cylindrical pipe, in the lower part of which there is a liquid coolant 6. The evaporator is installed in zone 1 and zone 3. In zone 2 there is a condenser 7 having finning to increase heat transfer area. In the upper part of the condenser, a valve 8 is usually located for evacuating the internal volume of the housing, filling the coolant, removing non-condensed gases, measuring pressure, etc.

The evaporator in the transport zone 3 may have a heat-insulating coating 9 to prevent spurious heat loss there and heat leakage into zone 1. A similar coating 9 is located on the evaporator in the zone of clay soils 10 that do not require freezing. Since the condensate does not heat up in these places when it drains, it falls into the zone of excess condensate and has a lower temperature compared to conventional soil coolers. For the same reason, greater heat removal from the ground is achieved in open areas of the evaporator, i.e. its effectiveness increases. Prevention of soil heaving due to the formation of a certain temperature distribution gives additional stability to the position of the thermostabilizer and ensures reliability in its operation.

In FIG. 2 shows a heat stabilizer made of easily deformable aluminum alloys. The structural elements of the device are similar to those described above. In this case, the capacitor 7 is made according to the star scheme and consists of three finned tubes 11. The lower pipe has a large length, partially located in the transport zone, and is buried in the ground by at least 20 cm. This design, while maintaining the condensation efficiency, provides the required fixation rigidity thermostabilizer and its resistance to bending loads.

If necessary, the lower part of the capacitor in the transport zone and in the ground can also be covered with a heat insulating layer to prevent heat loss. The heat-insulating coating 9 is located on the evaporator at the required depth in the zone of clay soils 10.

Implementation example

To implement the claimed utility model, a stabilized plastic frozen soil stabilizer was used (SPMG (K) -22000). Its total length was 24500 mm, with an evaporator length of 22000 mm. The diameter of the evaporator was 30 mm. The capacitor was a single ribbed pipe with a height of 1500 mm and an outer diameter of 72 mm. The evaporator and condenser were made of easily deformable aluminum material. When installing a heat stabilizer, the height of the transport zone was 1 m. The condenser was additionally fixed by means of a bracket. The evaporator in the transport zone was coated with liquid ceramic thermal insulation. A similar coating was applied at a depth of 6 and 11 m in the form of a strip with a width of 85 and 120 cm, respectively. The choice of location of the coating was determined by preliminary exploration surveys.

Liquid ceramic thermal insulation coating is a composition consisting of an acrylic binder and ceramic ultrafine spheres with discharged air. It is used in liquid consistency and is applied by layer spraying through a nozzle. The working temperature range for such a coating is from - 60 to + 250 ° C. The thickness of the liquid layer is up to 0.5 mm (0.3-0.4 mm when dried). The drying time of one layer at a temperature of 20 ° C and a humidity of 60% is up to 24 hours. This device used 4 layers with a total thickness of 1.6 mm. The thermal conductivity of the material ranged from 0.0012 to 0.0016 W / m ° C. To determine the temperature field in the soil, temperature sensors were located along the surface of the evaporator.

Field tests showed that the map of temperature fields in the soil complies with the calculated values, the absence of bulging stresses acting on the thermostabilizer and an increase in its efficiency (up to 15%). Thus, the claimed utility model can be recommended for thermal stabilization of complex heterogeneous soils.

Claims (5)

1. Thermostabilizer containing a gravitational heat pipe having a sealed, made with the possibility of refueling with a coolant, a housing comprising a condenser and an evaporator, characterized in that at least a part of the surface of the evaporator is coated with an insulating layer, the thickness of which does not exceed 3 mm and thermal conductivity its material is not higher than 0.01 W / m ° C. 2. Thermostabilizer according to claim 1, characterized in that the layer thickness does not exceed 1.5 mm, and the thermal conductivity is not higher than 0.002 W / m ° C. 3. Thermostabilizer according to claim 1, characterized in that the layer is made of liquid ceramic thermal insulation. 4. Thermostabilizer according to claim 1, characterized in that the condenser and evaporator are made of aluminum alloy. 5. Thermostabilizer according to claim 1, characterized in that the condenser and evaporator are made of steel.