RU2519012C2 - Method and device for year-round cooling, freezing of ground at foundation base and for heat supply of structure on permafrost ground in cryolytic zone - Google Patents

Abstract

FIELD: heating.

SUBSTANCE: invention relates to devices for controlled temperature stabilisation, cooling and freezing of ground at foundation bases as well as for heat supply of structures on permafrost grounds (in cryolytic zone). Method of year-round cooling, freezing of ground at a foundation base and for heat supply of a structure on permafrost ground in cryolytic zone involves drilling of wells, cooling of ground. All year round, cooling and freezing of the ground of a foundation base are controlled and the year-round partial heat supply of the structure is carried out due to the heat of the foundation base ground and adjacent ground layers that are cooled and frozen. The primary circuit of a heat pump with low temperature heat carrier is formed, the boiling temperature of the heat pump working medium is by 10-30°C lower than the minimal temperature of the heat carrier in the primary circuit. The heat pump is installed inside a structure and heat is supplied with the conversion factor above 1-3. The freezing temperature of the heat carrier in the primary circuit of the heat pump is lower than the minimal temperature of the ambient air of the structure's site up to -60°C. The evaporation temperature of the working medium in the secondary circuit is higher than the lower limit of its working range of temperatures up to -75°C. A thermal well is set in the block of a structure base with bearing piles on the periphery or thermal wells being divided into less powerful ones are set at its periphery along with providing for additional bearing function of a pile. The heat carrier of the divided thermal wells is delivered by heat insulated heating conduits to a common heat exchanger of the heat pump primary circuit or to several heat pumps installed in different rooms of the structure.

EFFECT: guaranteed year-round provision for frozen state of structure foundation base along the whole well depth as well as provision for year-round backing up of part (approximately the half) of structure's thermal load by means of a heat pump due to the usage of heat from the permafrost ground being cooled and frozen.

5 cl, 1 dwg, 3 tbl

Description

The invention relates to devices for controlled temperature stabilization, cooling and freezing of the foundation foundation soil, as well as heat supply to structures on permafrost soils (under permafrost conditions).

During industrial and civil construction of buildings in permafrost soils, a change in the temperature field of the foundations of structures occurs, since under the thermal action of structures defrosting bowls are formed, which leads to building settlement. The main task of erecting a foundation on permafrost soil is to preserve the frozen state of the soil, in which it has a high bearing capacity.

Many methods and devices are known for stabilizing and freezing the foundations of structures on permafrost soils, and many patents have been obtained for such methods and devices. However, none of them guarantees year-round freezing of the soil throughout the depth of the well and does not contain an additional heat supply function due to the heat of cooling of permafrost soil.

There is a method of increasing the stability of pile foundations in the permafrost zone, including placing a heat-insulating screen on the surface of the soil base and calculating its necessary parameters (RF patent No. 2159308, publ. November 20, 2000). The heat-insulating screen is placed on the surface and inside the soil base, its dimensions, geometric configuration, as well as the thermal properties of the material having spatial anisotropy, are determined from the conditions of coincidence of the designed temperature field, which ensures the stability of the structure throughout the entire period of operation, and the calculated temperature field obtained by solving by the finite difference method a non-stationary two-dimensional inhomogeneous heat equation in rectangular coordinates ah anisotropic medium for the presence therein movable boundary phase section and constituting geotechnical soil base section accommodating the projected heat shield and an adjacent soil layers.

The disadvantages of this method are the need for a large amount of heat-insulating material and the associated large amount of soil work, as well as the likelihood of a mismatch between the calculated and actual values of the temperature fields and the inability to subsequently adjust the temperature of the pile foundations.

A device for cooling soil is proposed for increasing the intensity and reducing the duration of the soil cooling process, as well as performing soil cooling with an adjustable process (RF patent No. 2110647, publ. May 10, 1998). The device comprises a casing pipe installed in a soil well with an internal pipe placed therein, connected by an air duct to a suction or pressure pipe of a fan. A pipe is inserted inside the casing, communicating with the surrounding air or the air duct and having the possibility of longitudinal movement inside the casing. The tube is made of a material with low thermal conductivity or has a coating of heat-conducting material. The inner pipe at the end has an ejection nozzle, and on the side surface has a helical rib and holes with a diameter of 0.08-0.12 D. The latter are located in the lower part of the pipe with a step in length of 30-50 D, where D is the inner diameter of the pipe.

The disadvantage of this device is its dependence on the temperature of the surrounding air environment, on the uncertainty of the position of the movable tube, low heat transfer coefficient from air to the inner surface of the casing.

A device for stabilization of plastic-frozen soils with a year-round mode of operation for accumulating cold at the base of structures, including the underground and aboveground parts of the tubular sealed enclosure filled with refrigerant, the underground part of which is an evaporator, and the aboveground part is a condenser equipped with a shelf having located on its surface thermoelectric modules in the form of a battery of Peltier elements (application for invention No. 2009114953, publ. October 27, 2010). This device is equipped with a heat pipe, one end of which having a shelf is attached to the hot surface of thermoelectric modules, and the other end, which is a condensation zone, has a ribbed surface, and the axis of the condensation zone is at an angle φ of inclination to the horizon and, alternatively, has a shelf on which radiators with fans installed on them.

The disadvantage of this device is the energy consumption and the possibility of icing on the ribbed surface of the capacitor.

The closest in technical essence to the proposed device is a thermal pile (RF patent No. 2250302, publ. 20.04.2005). Thermal piles are installed in permafrost in winter by drilling in it with the help of a drilling rig wells. Then the piles are exposed and fixed among themselves, after which water is poured into the gaps of the wells, which freezes and rigidly binds the entire structure in permafrost. The freezing of the flooded water in the gaps of wells in permafrost is also facilitated by the operation of the heat pipe when the ambient temperature is lower than the permafrost temperature. In this case, cooling of the soil around the evaporators begins to a temperature almost equal to the temperature of the surrounding air. A T-shaped pile with metal plate finning of capacitors, made simultaneously with the elements of the horizontal part of the pile, which allowed not only to provide a sufficiently developed external surface for intensive cooling of the condensers in winter, but also to ensure the strength of the heat pipe connected to the heat pile. If the heat pile is metal, then the heat pipe can simply be welded to the steel barrel and to the metal fins. In the case of not very large loads, the heat pipe itself can simultaneously serve as a pile. For more powerful structures, for the construction of buildings, roads, etc. it is advisable to make thermal piles reinforced concrete, while the heat pipe is part of the metal reinforcement. The invention was awarded a gold medal and diploma at the World Exhibition of Innovations, Research and New Technologies in Brussels “Eureka 2003”.

The disadvantage of the thermal pile of the prototype is the passivity of the thermal control system using a heat pipe, depending on the ambient temperature, the heat of condensation is not used.

In addition to those noted, a common drawback of all analogues and other structures for strengthening the foundations of the foundations in the permafrost zone is the lack of a heat supply system for structures due to the heat of a cooled or frozen permafrost.

The objective of the invention is the guaranteed year-round adjustable provision of the frozen state of the soil of the foundation foundation of the structure throughout the depth of the well, as well as the simultaneous provision of partial, up to half, coverage of the heat load of the structure with a heat pump conversion coefficient of more than one due to the heat of cooling and freezing of the permafrost and adjacent to it soil layers of the base.

The use of this invention will ensure a year-round stable state of the foundation of the structure due to the constantly frozen base, excluding thawing of the soil, as well as covering a partial, up to half the calculated value, heat load due to the heat of cooling and freezing of the soil with increasing temperature in the supply line by a heat pump, for example, up to + 35 ° C, followed by heating to the normative.

The above result is achieved by the fact that in the proposed method for year-round cooling, freezing the soil of the foundation base and heating the structure on permafrost soil in the permafrost zone, including drilling wells, cooling the soil, they regulate the cooling and freezing of the soil of the foundation base year-round and conduct year-round partial heat supply to the structure due to the heat cooled and frozen soil of the base of the foundation and adjacent layers of soil, while forming primary circuit with a low temperature coolant of the heat pump, in which the working fluid has a boiling point lower by 10-30 ° C of the minimum temperature of the primary coolant, the heat pump is placed inside the building and heat is supplied with a conversion factor greater than 1-3 unit, and the primary coolant the pump has a freezing temperature below the minimum ambient temperature of the construction site to -60 ° C, and the temperature of the evaporation of the working fluid of the secondary circuit in Above the lower limit of its operating temperature range to -75 ° C, the thermal well is installed in the center of the base of the structure with bearing piles on the periphery or, being divided into less powerful, the thermal wells are installed on its periphery, additionally carrying the function of the foundation piles of the structure, and the heat carrier divided thermal wells are fed through heat-insulated heat pipes to a common heat exchanger of the primary circuit of the heat pump or to several heat pumps installed in different rooms facilities.

In the proposed method, FreeziumTM is used as the primary coolant, and R23 freon is used as the working fluid of the heat pump.

In the proposed method, the foundation base soil can be any of the permafrost zone, for example, permafrost, taliks.

The technical result is also achieved by the fact that the proposed device for year-round cooling, freezing the soil of the foundation foundation and heating the structure on permafrost soil in the permafrost zone, containing a casing pipe plugged at the bottom and plugged in from below without a gap in the soil borehole, with a coaxially placed pipe with an open bottom end between the pipes at the upper end of the casing is plugged, the upper ends of the pipes contain nozzles, the cavity of the pipes and nozzles are filled with coolant, contains heat pump, low-temperature coolant, heating of the coolant occurs from the soil in the casing pipe, the inner pipe is insulated from the outside, the pipes are connected through the heat-insulated pipes to the suction and discharge pipes of the heat pump, forming the primary circuit, the working body of the heat pump has a boiling point lower by 10-30 ° With a minimum temperature of the primary coolant, the heat pump is located inside the building and provides heat supply with a conversion coefficient greater units, while the pipe nozzles are connected to an adjustable liquid pump and a heat exchanger, form an independent primary closed loop connected to the evaporator of the heat pump.

In the proposed device, the drive power for a heat pump and an adjustable liquid pump is consumed from the mains or from a wind generator.

The permafrost soil of the surface (hundreds of meters deep) earth layers is also considered as a low-grade energy source for heat supply through the use of heat pumps, which select the heat of the cooled and frozen soil and increase the coolant temperature in the supply line as the foundation foundation of the structure.

A pile, it is also a heat well, is made in the form of a heat exchanger of the type, for example, “pipe in pipe”, with a low-temperature (freezing temperature much lower than 0 ° С) coolant, pipelines forming the primary circuit of the heat pump; includes a heat pump with a boiling point of the working fluid below the lower freezing temperature of the coolant, auxiliary adjustable pumps of the primary circuit and the flow line, heating devices of the structure.

The essence of the invention is illustrated in figures 1, 2 and 3.

Figure 1 shows a schematic diagram of a device.

Figure 2 shows the design diagram of thermal well.

Figure 3 shows the changes in the minimum temperature of thermal wells 100 and 150 m, the diameter of the frozen soil and the conversion coefficient of the heat pump over the years of operation of the structure.

The principle of operation of heat pumps was proposed by W. Thompson in 1852.

The method of year-round cooling, freezing the soil of the base of the foundation and heat supply to the structure on permafrost soil in the permafrost zone is as follows.

Heat taken from the environment, such as soil, is transferred to the heat exchanger 1 of the heat pump evaporator, in a closed circuit of which a working fluid, such as freon, is circulated. Freon in evaporator 2 boils and evaporates at low temperature, absorbing the latent heat of evaporation. Vapors enter compressor 3, where their pressure and temperature rise. The compressed freon vapor enters the condenser 4, where the freon 5 is cooled by the heat exchanger 5, transferring its latent phase transition heat to the heat carrier circulating in the heat supply system 6. After cooling, the freon goes into a liquid state and returns through the control valve or expander 7 to the evaporator 2. The heat pump has own primary pump or (and) auxiliary 8, if own power is not enough.

The thermal well can be located both in the center of the foundation foundation and on the periphery of the structure, performing the functions of piles, while the power and depth of thermo-well piles decreases in proportion to their number, and the heat pipes from the thermo-well piles are connected to a common heat pump located inside the structure, or to separate heat pumps located in different rooms of the structure.

Before using the device at the site of the future structure, engineering and geological drilling is carried out in order to determine the properties and power of the soil, if this was not known before. The thermal loads of the structure (s) are determined and thermal engineering calculations are carried out, as a result of which the parameters of the well and the thermal well placed in it without a gap are determined (Fig. 2), which selects heat from the ground using a heat pump (Fig. 1). A thermal well is a heat exchanger of the type, in particular, “pipe in pipe”, immersed vertically in soil at a design depth. The heat carrier circulating in the heat exchanger removes heat from the soil and delivers it to the heat exchanger 1 of the evaporator 2 of the heat pump (Fig. 1). After cooling, the coolant through the inner pipe returns to the lower part of the heat exchanger, the primary loop closes. A working fluid, for example, freon, circulates along the secondary circuit. Freon in evaporator 2 boils and evaporates at low temperature, absorbing the latent heat of evaporation. Vapors enter compressor 3, where their pressure and temperature rise. The compressed freon vapor enters the condenser 4, where the freon 5 is cooled by the heat exchanger 5, transferring its latent phase-transition heat to the heat carrier circulating in the heat supply system 6. After cooling, the freon goes into a liquid state and returns to the evaporator 2 through the control valve or expander 7.

The heat pump has its own primary pump or (and) auxiliary 8, if its own power is not enough.

Due to the fact that every year the volume of chilled soil around the thermal well increases, the course of time of this process and its effect on the foundation foundation is considered using the example of covering the heat load of a two-story building with an area of S = 250 sq. meters, in which 10 people live, located in an area with conditions similar to the conditions of the village of Khatanga, Krasnoyarsk Territory.

According to SNiP-23-01-99, the duration and average outdoor temperature of the period with an average air temperature of not more than 8 ° C are determined, respectively, z _ht = 311 days and t _ht = -17.1 ° C.

According to SNiP-23-02-2003, the degree-day is determined by the formula:

Dd = (t _int -t _ht ) z _ht ,

where t _int = 21 ° C is the calculated average temperature of the internal air of the building; Dd = 11849 degree days. The normalized specific heat energy consumption for heating is determined according to table 8 of SNiP-23-02-2003:

Вт·ч(м²·°C·сут), $$q_h^{reg}=105\mathrm{to}D\mathrm{well}/\left({\mathrm{<figure-callout\; id="2"\; label="m"\; filenames="00000007.png,00000009.png"\; state="\{\{state\}\}">m</figure-callout>}}^2{\cdot }^{\circ }\text{A.}C\cdot \mathrm{from}\mathrm{at}t\right)=29.17$$

W · h (m ² · ° C · day),

and then the heat load of the heating period

$$Q=q_h^{reg}\cdot Dd\cdot S/3.6=86409\text{kW}\cdot \text{h}\text{.}$$

Monthly heat load is taken, in the absence of data, for example, uniform for 10 months of the heating period, which is 8640 kWh, and in June and July - only for hot water supply. Take the thermal load, which is covered by the heat pump converting the heat of frozen soil, equal, for example, to half the calculated value (Table 1). The remaining half of the load is covered by a heat generator or pre-heater, usually built into the heat pump housing.

They are limited by the processes of heat transfer from the soil to the heat well heat exchanger. Figure 2 shows the design diagram of the thermal well, where d ₀ is the diameter of the outer pipe of the heat exchanger, d ₁ is the diameter of the soil layer after the first month of cooling (covering the monthly load), di is after the second month, etc., d ₂ is the next diameter .

Calculations are made under the assumption of a quasistationary regime during each month. The mass of each layer is determined by the formula:

$$m=\frac{Q}{c_p\left(t_w-t_c\right)},\left(5\right)$$

where Q is the monthly heat load from Table 1, c _p is the specific heat of the soil, t _w and t _c are the average temperature of the layer at the boundaries with uncooled and cooled soil layers. The heat flux from the cooled layer to the heat exchanger is defined as

$$q=\frac{t_w-t_0}{R},\left(6\right)$$

where t ₀ is the average temperature on the outer shell of the heat exchanger, R is the thermal resistance from the uncooled layer to the heat exchanger, for example from d ₁₃ to d ₀ :

$$R=\frac{\mathrm{one}}{2\pi \lambda h}\ln \frac{d_i}{d_0},\left(7\right)$$

where d _i are the diameters d ₁ , d ₂ , ..., d _n , d _i ; h - the height of the hollow cylinder (the next layer of soil).

Take, for example, due to lack of data, the following properties of permafrost soil:

temperature t _w = -4 ° С [Alekseev S.I. Foundations and foundations. Part 12. Quote: “Below the depth of H ₀ - the amplitude of zero temperatures, permafrost soil will be at a constant negative temperature ≈ -4 ° С ... at a depth of ≈15 m”];

thermal coefficients: c _p = 2.135 kJ / (kg · ° C), γ = 917.4 kg / m ³ , λ = 2.09 W / (m · K) [Gavrilyev RI Theoretical estimates of the thermal conductivity of segregated ice. Institute of permafrost them. P.I. Melnikova SB RAS, 677010, Yakutsk, mpi@ysn.ru Author's project O8ODE.RU]; the temperatures at the inlet to the evaporator t _in and at the outlet t _{out are} determined by calculations to obtain a given thermal power. The mass of soil cooled per year is ≈3000 tons in this example.

Calculations are carried out from the beginning of the heating season, assuming completely naturally chilled soil (first year of operation). Calculations and graphics are performed using the computer program Excel, the graph is presented as in figure 3.

Coverage of the heat load in the first year of operation with the diameter of the outer pipe of the heat exchanger (casing) d ₀ = 0.5 m occurs: at a well depth of h≈150 m, the coolant in the casing is cooled to a temperature of -16 ° C and the diameter of the cooled soil is ≈6 m; at a well depth of h≈100 m, respectively, -26 ° C and 8 m. For the second and every subsequent years of operation, the heating period will begin with an increasingly thicker cooled soil layer, i.e. with increasing thermal resistance R. Figure 3 shows the change in the diameter of the frozen soil and the minimum temperature of the well during 10 years of operation.

As follows from figure 3, in the 10th year, these indicators will increase to ≈21 m and -25 ° C (well 150 m) and ≈21 m and -37 ° C (100 m). In the future, this pattern has a weakly expressed exponential character. It also shows the average annual values of the conversion coefficients of the ideal reverse Carnot heat pump cycle, which shows that with a decrease in the cooling temperature (freezing) and a decrease in the depth of the thermal well, the conversion coefficients decrease. For a real cycle with a coefficient of thermodynamic perfection ν = 0.2-0.5, the conversion coefficient remains greater than unity.

Based on the obtained temperature values, a low-temperature coolant, a working fluid and a heat pump cycle are selected. Next, a well is drilled, a casing is installed without clearance, installation of thermal borehole components, pipelines, work inside the structure: connecting a heat pump, driving power from a network or from a system with a wind generator, thermal devices and automation systems in accordance with building codes.

The device may have an independent primary closed circuit with an adjustable liquid pump and a heat exchanger connected through pipe pipes to the heat pump evaporator. This scheme is applicable if the heat pump primary circuit pump is insufficient.

The device contains a low-temperature coolant of the primary circuit of the heat pump with a freezing temperature below the minimum ambient temperature of the construction site, for example, FreeziumTM having a freezing temperature of -60 ° C [http://temper-t.narod.ru/Freeziumpdf.pdf], and the temperature the evaporation of the working fluid of the secondary circuit, for example Freon R23, above the lower limit of its working temperature range (-75 ° C) [Internet. ["Geofrost-Trade" © 2009-2011]. Ozone Depletion Potential ODR = 0 [http://www.freon-group.ru/freon_r23/]. Such temperatures will not lead to freezing of the heat carrier and the working fluid of the heat pump during installation of an emergency stop of the equipment, but the nominal temperatures are selected according to the calculation results (Fig. 3).

The device freezes any soil in the permafrost zone, for example, permafrost, taliks, as at a sufficient depth of the well, tens of meters, the thermoway is held in place by the soil without additional fixing devices, and freezing near the casing takes place quite quickly (several hours) after the heat pump is turned on.

The thermal well of the device is located, depending on the size and configuration of the structure, in the center of the base of the structure with bearing piles on the periphery or, being divided into less powerful, thermal wells are installed on its periphery, performing an additional bearing function of the pile.

The device uses drive power for a heat pump and an adjustable fluid pump from the mains or from a wind generator, providing constant or intermittent drive power.

Claims (5)

1. The method of year-round cooling, freezing the soil of the base of the foundation and heat supply to the structure on permafrost soil in the permafrost zone, including drilling wells, cooling the soil, characterized in that the cooling and freezing of the soil of the base of the foundation is regulated year-round, and the structure is heated all year round due to the heat of the cooled and the frozen soil of the base of the foundation and adjacent layers of soil, while forming a primary circuit with low-temperature heat carrier fluid, the working fluid of the heat pump has a boiling point lower by 10-30 ° C of the minimum temperature of the primary coolant, the heat pump is located inside the building and heat is supplied with a conversion factor greater than 1-3 units, and the primary coolant of the heat pump has a freezing temperature below the minimum ambient temperature of the construction site to -60 ° C, and the temperature of the evaporation of the working fluid of the secondary circuit is higher than the lower limit of its working temperature range to -75 ° C, while a thermal well is installed in the array of the base of the structure with bearing piles around the periphery or, being divided into less powerful, thermal wells are installed along its periphery, additionally carrying the function of piles, and the heat carrier of the separated thermal wells is fed through heat-insulated heat pipes to a common heat exchanger of the primary circuit of the heat pump or to several heat pumps installed in various rooms of the structure. 2. The method according to claim 1, characterized in that FreeziumTM is used as the primary coolant, and R23 freon is used as the working fluid of the heat pump. 3. The method according to claim 1, characterized in that the foundation base soil can be any of the permafrost zone, for example, permafrost, taliks. 4. A device for year-round cooling, freezing of the foundation foundation soil and heat supply of the structure on permafrost soil in the permafrost zone, containing a casing pipe plugged at the bottom and plugged in it with a coaxial pipe with an open bottom end, a gap between the pipes on the upper end face of the casing the pipe is plugged, the upper ends of the pipes contain nozzles, the cavity of the pipes and nozzles are filled with coolant, characterized in that the device contains a heat pump, low temperature thermal fluid, heating of the coolant comes from soil in the casing pipe, the inner pipe is insulated externally, the pipes are connected through heat-insulated pipes to the suction and discharge pipes of the heat pump, forming a primary circuit, the working body of the heat pump has a boiling point lower by 10-30 ° C minimum temperature primary coolant, and the heat pump is located inside the structure and provides heat supply with a conversion factor greater than unity, while the nozzles pipes are connected to an adjustable liquid pump and heat exchanger and form an independent primary closed loop connected to the heat pump evaporator. 5. The device according to claim 4, characterized in that the drive power for the heat pump and the regulated liquid pump is consumed from the mains or from a wind generator.

Images