All-season heat rod device and permafrost stability maintenance method

Abstract

The present invention discloses an all-season hot rod device and a method for maintaining the stability of permafrost, which belongs to the technical field of permafrost protection. The all-season hot rod device includes a hot rod unit and a refrigeration unit. The hot rod unit is divided into a condensation section, an insulation section and an evaporation section from top to bottom. The condensation section is placed above the ground surface, the insulation section is placed in the seasonal active layer of the frozen soil, and the evaporation section is placed in the permafrost layer. The gaseous heat carrier at the bottom of the evaporation section is ejected into the upper condensation section by an ejector in the insulation section; the refrigeration unit is placed on the top of the condensation section, which can absorb the heat of the condensation section and release it into the atmosphere; the operation of the hot rod unit and the refrigeration unit is controlled according to the permafrost temperature. The present invention combines the hot rod unit with the refrigeration unit to continuously deliver cold to the permafrost throughout the year, and maintain the thermal stability of the permafrost project; at the same time, it has the advantages of zero energy consumption, efficient heat transfer, convenient transportation and convenient installation, reliable operation, and can achieve the dual goals of permafrost protection and energy saving and efficiency improvement.

Description

Technical Field

[0001] The invention belongs to the technical field of permafrost protection, and in particular relates to an all-season heat rod device and a permafrost stability maintenance method. Background Art

[0002] Permafrost refers to a special geological body located below the surface, which remains in a negative temperature state for a long time and contains ice. Its upper part is covered by seasonal freezing and thawing layers of a certain depth, which are called permafrost and active layer respectively. China's permafrost is mainly distributed in the Greater Khingan Range and Lesser Khingan Range in the northeast, the Altai Mountains, Tianshan Mountains, Qilian Mountains and the Qinghai-Tibet Plateau in the west, with a total area of ​​more than 1 / 5 of the country's land area. The difficulty faced by transportation construction activities in permafrost areas is that under the combined effects of climate warming and engineering disturbances, permafrost foundations are prone to temperature creep and melting settlement deformation, which in turn causes deformation and damage to the upper roadbed. Therefore, protecting permafrost is currently the primary principle of engineering construction in permafrost areas.

[0003] At present, heat rods are the main measure to protect permafrost. In essence, they are enlarged coreless gravity heat pipes. Heat pipes are heat transfer elements with extremely high thermal conductivity. They rely on the latent heat of phase change of the internal medium to greatly increase the heat flux. When there is a small temperature difference between the evaporation section and the condensation section, the heat transfer cycle can be started with zero power consumption. The principle of heat rods to protect permafrost is: the evaporation section is placed in the permafrost layer, and the condensation section is placed above the surface. In winter, when the air temperature is lower than the permafrost temperature, the liquid medium in the evaporation section absorbs heat and vaporizes. The gaseous medium rises to the condensation section, dissipates heat and liquefies, and flows back to the evaporation section by gravity. In this way, it absorbs heat from the permafrost foundation repeatedly to cool it down, thereby efficiently storing cold in winter. When the air temperature is higher than the permafrost temperature, the gaseous medium cannot liquefy and the heat transfer cycle is terminated. The shortcoming of heat rods is that they are in a suspended state when the permafrost is seriously degraded during the warm season. They are not timely enough and can only indirectly protect the frozen soil. They have poor seasonal matching and are actually "winter heat rods". For this reason, in recent years, the industry has begun to introduce "refrigeration" technology to continuously cool permafrost. For example, the patent application number CN201711190185.7 discloses a compression refrigeration system for preventing and controlling permafrost degradation, which is a refrigeration system driven by solar and wind energy. The refrigeration equipment can operate continuously throughout the year, covering the operation window period of the heat rod in the warm season, but the cooling load required when using only refrigeration equipment to protect permafrost is very large, which increases the capacity of the refrigeration equipment and the investment in external energy supporting equipment, and has the disadvantages of high energy consumption and high investment.

[0004] In general, refrigeration equipment can output continuously and have high seasonal matching, but it is difficult to have the zero energy consumption and high thermal conductivity of heat rods; heat rods have high heat transfer efficiency and zero energy consumption, but it is difficult to have the continuous cooling performance of refrigeration equipment throughout the year. It can be seen that improving the compatibility of heat rods and refrigeration equipment so that both can share the permafrost cooling load is the key to promoting the low energy consumption, seasonal matching and timeliness of permafrost protection technology. Summary of the invention

[0005] The purpose of the present invention is to provide an all-season heat rod device and a permafrost stability maintenance method, aiming to solve the technical problems of the heat rod warm season operation window and the high energy consumption of refrigeration equipment in the existing permafrost protection technology.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] An all-season heat rod device comprises a heat rod unit and a refrigeration unit. The heat rod unit is divided into a condensation section, an insulation section and an evaporation section from top to bottom. The condensation section is arranged above the ground surface, the insulation section is arranged in the seasonal active layer of frozen soil, and the evaporation section is arranged in the permafrost layer. An ejector is provided in the insulation section for ejecting the gaseous heat carrier at the lower part of the evaporation section into the upper condensation section. The refrigeration unit is arranged at the top of the condensation section of the heat rod unit for absorbing the heat of the condensation section and releasing it into the atmosphere.

[0008] Furthermore, the heat rod unit includes a tube shell, heat dissipation fins, an ejector and a phase change heat storage sleeve, the tube shell is a tubular structure sealed at the top and bottom, the heat dissipation fins are arranged outside the tube shell of the condensing section, the ejector is arranged inside the tube shell of the insulation section, the outlet end of the ejector extends to the tube shell of the condensing section, and the inlet end extends to the tube shell of the evaporation section; the phase change heat storage sleeve is arranged outside the tube shell of the evaporation section, and an annular cavity is provided between the tube shell of the evaporation section and the phase change heat storage sleeve, and the upper and lower ends are sealed, and the annular cavity is filled with phase change material.

[0009] Furthermore, a positioning base is fixed to the outside of the tube shell of the insulation section, a concrete foundation is provided on the top of the positioning base, the concrete foundation is arranged above the ground surface, and the positioning base is arranged below the ground surface.

[0010] Furthermore, a capillary mesh core is provided on the inner wall of the tube shell of the evaporation section, and the capillary mesh core is composed of a plurality of pieces, which are arranged at intervals along the circumferential direction of the inner wall of the tube shell; the length of the capillary mesh core is equal to the length of the evaporation section, and the coverage area of ​​the capillary mesh core is 50% of the total area of ​​the inner wall of the tube shell of the evaporation section.

[0011] Furthermore, the ejector comprises a nozzle, a contraction section, a mixing section and an expansion section from bottom to top, the nozzle and the contraction section are both reducers that are small at the top and large at the bottom, the mixing section is a straight tube that connects the contraction section and the expansion section from top to bottom, and the expansion section is a reducer that is large at the top and small at the bottom.

[0012] Furthermore, the small diameter ends of the contraction section and the expansion section are the same as the inner diameter of the mixing section, the contraction section is the same as the expansion section in length, and the length of the mixing section is smaller than the length of the contraction section and the expansion section.

[0013] Furthermore, the refrigeration unit includes a cabinet, a refrigeration component and a power supply component for providing power thereto, the cabinet is a hollow cylindrical shell, and the bottom of the cabinet is connected to the condensing section of the heat rod unit through a flange; the power supply component includes an energy storage battery, a voltage stabilization controller, a wind generator and a solar photovoltaic panel, the solar photovoltaic panel is arranged on the outer wall of the cabinet, the wind generator is arranged on the top of the cabinet, and a ventilation window corresponding to the wind generator is provided on the side wall of the cabinet, the energy storage battery and the voltage stabilization controller are arranged at the lower part of the cabinet, and the energy storage battery, the wind generator and the solar photovoltaic panel are all connected to the voltage stabilization controller;

[0014] The refrigeration assembly includes a compressor, a condenser and an evaporative refrigerator. The compressor and the condenser are arranged inside the cabinet. The evaporative refrigerator is arranged on the lower outer side of the condensing section and is used to supply cold to the condensing section to cool the internal heat carrier; the evaporative refrigerator is connected to the condenser through a refrigerant pipeline, the outlet of the condenser is connected to the inlet of the compressor, and the outlet of the compressor is connected to the evaporative refrigerator through a refrigerant pipeline.

[0015] Furthermore, the refrigerant pipeline includes a liquid refrigerant pipe and a gas refrigerant pipe, both of which are spiral and staggered around the outer wall of the condensing section. The inlet of the evaporative refrigerator is connected to the liquid refrigerant pipe through a throttle, and the inlet of the compressor is connected to the gas refrigerant pipe.

[0016] Furthermore, the evaporative refrigerator is provided with a heat preservation sleeve on the outside, the heat preservation sleeve is composed of two arc plates, and a gap is provided between the two arc plates, and the upper end of the arc plate is connected to the condensing section through a flange. The throttle is a capillary tube, and a protective sleeve is provided on the outside of the capillary tube.

[0017] The present invention also provides a method for maintaining the stability of permafrost, which uses the all-season heat rod device to cool the permafrost, comprising the following steps:

[0018] (1) When the permafrost temperature is less than -2.5°C, the heat flux from the atmosphere to the permafrost is ≤ 0, and the heat rod unit does not operate;

[0019] (2) When the permafrost temperature is ≥ -2.5°C and < -1.5°C, the heat flux from the atmosphere to the permafrost is > 0, the heat rod unit starts to operate, and the refrigeration unit does not start;

[0020] (3) When the permafrost temperature is ≥ -1.5℃ and < -0.5℃, the heating unit operates and the refrigeration unit operates intermittently. The start and stop time of the refrigeration unit is calculated and determined according to the following formulas (1) and (2):

[0021] (1)

[0022] In the formula, H i is the average monthly cooling requirement in the permafrost control area corresponding to the i-th all-season heat rod device, kJ; CP A , CP T are the monthly average heat capacity flow rates of the atmospheric heat flux and the cold flux of the heat rod unit in the permafrost control area corresponding to the i-th all-season heat rod device, kW / ℃; T i is the average permafrost temperature in the control area of ​​the i-th all-season heat rod device; m i is the mass of permafrost in the control area of ​​the i-th all-season thermal rod device, kg; c i is the specific heat capacity of permafrost in the control area of ​​the i-th all-season heat rod device, kJ / (kg·℃); ΔT i is the change in the monthly average temperature of permafrost in the control area of ​​the i-th all-season heat rod device compared with the same month in previous stable years, ℃;

[0023] (2)

[0024] In the formula, t i is the daily required operating time of the refrigeration unit of the i-th all-season heat rod device, h; N is the number of days in the corresponding month; q is the refrigeration power of the refrigeration unit of the i-th all-season heat rod device, W;

[0025] (4) When the permafrost temperature is ≥ -0.5°C, the refrigeration unit operates at full capacity until the permafrost temperature drops below -0.5°C, and the refrigeration unit executes according to step (3).

[0026] Compared with the prior art, the present invention has the following technical advances:

[0027] The present invention combines a heat rod unit with a refrigeration unit to form an all-season heat rod device that can continuously deliver cold to permafrost throughout the year, thereby getting rid of the seasonal dependence on winter and achieving more real-time and effective maintenance of the thermal stability of permafrost engineering; the operation of the heat rod unit and the refrigeration unit is controlled according to the permafrost temperature to achieve the purpose of protecting permafrost. The present invention has zero energy consumption, efficient heat transfer and all-season continuous cold delivery performance, and has convenient transportation and installation, good scene adaptability, reliable operation, and intelligent technical effects, which can achieve the dual goals of permafrost protection and energy saving and efficiency improvement. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention.

[0029] In the attached picture:

[0030] Figure 1 A schematic structural diagram of an all-season heat rod device provided by an embodiment of the present invention;

[0031] Figure 2 It is the appearance diagram of the heat rod unit and the refrigeration unit in the embodiment of the present invention;

[0032] Figure 3 It is a structural schematic diagram of an ejector in an embodiment of the present invention;

[0033] Figure 4 Schematic diagram of the internal structure of a cabinet in an embodiment of the present invention;

[0034] Figure 5 is an appearance diagram of a cabinet in an embodiment of the present invention;

[0035] Figure 6 This is a schematic diagram of the installation of an evaporative refrigerator on a condensing section in an embodiment of the present invention;

[0036] Figure 7 A schematic diagram of the structure of a refrigeration unit in an embodiment of the present invention;

[0037] Figure 8 It is a schematic diagram of the installation of the capillary mesh core inside and outside the tube shell and the phase change heat storage sleeve in the embodiment of the present invention;

[0038] Fig. 9 A schematic diagram of installing an all-season heat rod device in permafrost provided by an embodiment of the present invention;

[0039] Fig.10 An application state diagram of an all-season heat rod device provided by an embodiment of the present invention;

[0040] In the figure:

[0041] 1-tube shell, 101-condensing section, 102-insulating section, 103-evaporating section; 2-bracket; 4-flange; 5-heat dissipation fin; 6-phase change heat storage sleeve; 7-positioning base; 8-concrete foundation; 9-capillary mesh core; 10-ejector, 1001-nozzle, 1002-contraction section, 1003-mixing section, 1004-expansion section; 11-cabinet; 12-base; 13-equipment cabin, 1301-upper cabin, 1302-lower cabin Cabin; 14-ventilation window; 15-wind turbine; 16-condenser; 17-voltage stabilization controller; 18-energy storage battery; 19-compressor; 20-solar photovoltaic panel; 21-evaporative refrigerator; 22-insulation sleeve; 23-throttle; 24-refrigerant pipeline, 2401-liquid refrigerant pipe, 2402-gas refrigerant pipe; 25-roadbed; 26-foundation, 2601-seasonal active layer of frozen soil, 2602-permafrost layer. DETAILED DESCRIPTION

[0042] The following specific embodiments may be combined with each other, and the same or similar concepts or processes may not be described in detail in some embodiments. The embodiments of the present invention will be described below in conjunction with the accompanying drawings.

[0043] like Figure 1 , Figure 2 As shown, an all-season hot rod device provided by an embodiment of the present invention includes a hot rod unit and a refrigeration unit. The hot rod unit is divided into a condensation section 101, an insulation section 102 and an evaporation section 103 from top to bottom. The condensation section 101 is arranged above the ground surface, the insulation section 102 is arranged in the frozen soil seasonal active layer 2601, and the evaporation section 103 is arranged in the permafrost layer 2602. An ejector 10 is provided in the insulation section 102 for ejecting the gaseous heat carrier at the bottom of the evaporation section 103 into the upper condensation section 101; the refrigeration unit is arranged at the top of the condensation section 101 of the hot rod unit for absorbing the heat of the condensation section 101 and releasing it into the atmosphere. The refrigeration unit and the condensation section 101 are detachably connected, and the two are connected by a flange 4 for easy installation and disassembly.

[0044] In the specific production, the length of the condensation section 101 is 80% of the length of the evaporation section 103, the length of the insulation section 102 is consistent with the thickness of the frozen soil seasonal active layer 2601, and the length of the evaporation section 103 is the target depth range of permafrost layer protection. The standard lengths of the evaporation section, insulation section, and condensation section are 6.0 m, 2.0 m, and 4.8 m, respectively. When the upper limit of the permafrost burial depth or the permafrost protection depth range in the actual scene is significantly different from the standard size, a corresponding special design can be made.

[0045] In a specific embodiment of the present invention, Figure 1As shown, the heat rod unit includes a tube shell 1, heat dissipation fins 5, an ejector 10 and a phase change heat storage sleeve 6, the tube shell 1 is a tubular structure sealed at the top and bottom, the heat dissipation fins 5 are arranged outside the tube shell 1 of the condensation section 101, the ejector 10 is arranged inside the tube shell 1 of the insulation section 102, the outlet end of the ejector 10 extends to the tube shell 1 of the condensation section 101, and the inlet end extends to the tube shell 1 of the evaporation section 103; the phase change heat storage sleeve 6 is arranged outside the tube shell 1 of the evaporation section 103, and an annular cavity is provided between the tube shell 1 of the evaporation section 103 and the phase change heat storage sleeve 6, and the upper and lower ends are sealed, and the annular cavity is filled with phase change material.

[0046] During the specific production, the tube shell is made of stainless steel tubes or carbon seamless steel tubes with equal diameter, hollow, smooth inner and outer walls, with specifications of standard tubes with outer diameter of 89mm and wall thickness of 3.0mm, and tube length of 10.0~16.0m; the bottom of the tube shell is sealed with a flat plate of the same material, and the top is connected with a special end cover, and the sealing and connection processes are all argon arc welding. Among them, the end cover adopts a cylindrical spinning head, and a mechanical one-way valve is welded on the spinning head to inject heat carrier into the tube shell. The material is the same as the tube shell, and the height is 5cm. The specific production of the condensation section 101, the insulation section 102 and the evaporation section 103 is as follows:

[0047] On the outer wall of the tube shell 1 of the condensing section 101, 40 cm below the top and 40 cm above the bottom, an annular flange 4 is welded, the inner diameter of the flange is equal to the outer diameter of the tube shell 1, and the flange width is 4 cm. The heat dissipation fins 5 are welded between the upper and lower flanges 4. The heat dissipation fins 5 are made of aluminum alloy, with a width of 3.0 cm and a thickness of 1.0 mm. They are tightly welded on the outer wall of the tube shell 1. The structure is a fin type. The spacing of the heat dissipation fins 5 along the longitudinal direction of the tube shell 1 is 3.0 cm, the purpose is to increase the effective heat exchange area of ​​the condensing section 101 and enhance the air-cooled heat dissipation condensation effect.

[0048] A phase-change heat storage sleeve 6 is installed on the outer wall of the tube shell 1 of the evaporation section 103. The phase-change heat storage sleeve 6 is a sandwich tube made of 201 stainless steel. The wall thickness of the phase-change heat storage sleeve 6 is 1.0 mm, the inner diameter is equal to the outer diameter of the tube shell 1, the thickness of the phase-change heat storage sleeve 6 is 3.0 cm, and the length of the phase-change heat storage sleeve is equal to the length of the evaporation section 103. The annular cavity between the phase-change heat storage sleeve 6 and the tube shell 1 is filled with a phase-change material. The phase-change material is a solid-liquid nano-eutectic negative temperature phase-change material, and the critical phase change temperature is taken as the average ground temperature value of the permafrost protection depth range minus 0.5°C. The function of the phase-change heat storage sleeve 6 is: during the operation of the hot rod unit, if the external temperature of the shell of the evaporation section 103 is too low, it will cause the hot rod unit to absorb insufficient heat and the heat carrier gasification rate to be too low, so that the hot rod unit will stop working. The phase change thermal storage material helps to maintain the temperature level of the outer wall of the tube shell 1 under the condition of increasing the cold storage capacity during the heat absorption and cold transmission process of the evaporation section 103, ensure the gasification rate of the evaporation section 103, and increase the effective operation time of the heat rod unit. When the heat rod unit stops working due to climate change, the cold contained in the phase change thermal storage material continues to diffuse into the permafrost foundation.

[0049] The tube shell 1, heat dissipation fins 5, and phase change heat storage sleeve 6 are all treated by a "hot dip galvanizing" surface treatment process, and the zinc layer is used to resist oxidation corrosion in a humid environment and extend the service life of the equipment.

[0050] In a specific embodiment of the present invention, Figure 2 , 9 As shown, a positioning base 7 is fixed to the outside of the tube shell 1 of the insulation section 102, and a concrete foundation 8 is provided on the top of the positioning base 7. The concrete foundation 8 is arranged above the ground surface, and the positioning base 7 is arranged below the ground surface. During the specific production, a positioning base 7 is welded at a position 20 cm below the junction with the upper condensation section 101. The inner diameter of the positioning base 7 is equal to the outer diameter of the tube shell 1, and the outer edge of the positioning base 7 is a square with a side length of 20 cm. The concrete foundation 8 is a split-type prefabricated foundation. The inner diameter of the concrete foundation 8 is equal to the outer diameter of the tube shell 1, and the outer edge is a square with a side length of 30 cm and a height of 20 cm. The function of the concrete foundation 8 is, on the one hand, to increase the counterweight of the heat rod to prevent deflection, and on the other hand, to prevent rainwater from seeping in.

[0051] Further optimize the above scheme, such as Figure 8As shown, a capillary mesh core 9 is provided on the inner wall of the tube shell 1 of the evaporation section 103. The capillary mesh core 9 is composed of several pieces, which are arranged at intervals along the inner wall of the tube shell 1; the length of the capillary mesh core 9 is equal to the length of the evaporation section 103, and the coverage area of ​​the capillary mesh core 9 is 50% of the total area of ​​the inner wall of the tube shell of the evaporation section 103. The width of each capillary mesh core is 3 to 5 cm, and they are evenly distributed and installed at a certain interval; the material of the capillary mesh core 9 is a fine mesh of stainless steel material, which has a capillary suction function. The effect of the capillary mesh core 9 is to make a part of the liquid heat carrier in the evaporation section located at the bottom of the tube shell, and the other part is located in the capillary mesh core, so as to maintain the uniformity of the cooling in the evaporation section and avoid the uneven cooling caused by the cooling area of ​​the traditional gravity reflux hot rod being concentrated at the bottom of the evaporation section.

[0052] During the actual operation of the heat rod unit, the gaseous heat carrier generated in the upper part of the evaporation section has a short rising path to enter the condensation section, while the gaseous heat carrier generated in the lower part of the evaporation section has a longer rising path. When the vaporization rate is low, it may be suspended and stagnant in the evaporation section due to insufficient rising kinetic energy, and cannot enter the condensation section for liquefaction, resulting in the termination of the gas-liquid phase change cycle of the heat rod heat carrier. For this reason, an ejector 10 is installed inside the tube shell 1 of the middle insulation section 102, and the ejector 10 is welded to the inner wall of the tube shell 1 through an annular bracket (not shown in the figure). Figure 3 As shown, the ejector 10 is composed of a nozzle 1001, a contraction section 1002, a mixing section 1003 and an expansion section 1004 from bottom to top. The nozzle 1001 and the contraction section 1002 are both reducers with a small top and a large bottom. The mixing section 1003 is a straight tube connecting the contraction section 1002 and the expansion section 1004 from top to bottom. The expansion section 1004 is a reducer with a large top and a small bottom. The ejector 10 is used to separate the interior of the evaporation section 103 into different gas channels. The gaseous heat carrier in the upper part of the evaporation section 103 directly rises and enters the condensation section 101, while the gaseous heat carrier in the lower part is efficiently ejected by the ejector into the upper condensation section 101, so as to ensure that the gaseous heat carrier flows in an orderly manner inside the heat rod unit, prevent suspension stagnation, increase the overall upward and downward circulation volume inside the heat rod unit when the gasification rate of the liquid heat carrier in the evaporation section 103 is low, increase the heat transfer efficiency, and thus improve the permafrost protection effect of the heat rod unit.

[0053] During the specific manufacturing process, the small diameter ends of the contraction section 1002 and the expansion section 1004 are the same as the inner diameter of the mixing section 1003, the contraction section 1002 and the expansion section 1004 are the same in length, and the length of the mixing section 1003 is less than the length of the contraction section 1002 and the expansion section 1004. The ejector 10 is made of stainless steel with a thickness of 0.4 mm and an overall height of 7.0 m. The nozzle 1001 is a reducer with a height of 2.5 m, an inlet and an outlet diameter of 50 mm and 15 mm respectively, the contraction section 1002 is a reducer with a height of 2.0 m, an inlet and an outlet diameter of 45 mm and 20 mm respectively, the mixing section 1003 is a constant diameter tube with a height of 0.5 m and a diameter of 20 mm, and the expansion section 1004 is a reducer with a length of 2.0 m, an inlet and an outlet diameter of 20 mm and 45 mm respectively.

[0054] The heat carrier in the heat rod unit is pure ammonia. The boiling point of liquid ammonia at normal pressure is -33.5℃, the latent heat of vaporization is 1336.97kJ / kg, and the critical density is 0.235g / cm 3 The beneficial effect of using pure ammonia is that ammonia has a low boiling point and a large latent heat of evaporation. It can quickly absorb and release heat in the tube shell of the heat rod unit. It is suitable for applications that require efficient heat transfer. It has moderate density and good fluidity. It can form a good upward and downward gravity circulation migration and capillary mesh core uniform migration inside the heat rod, which is conducive to uniform heat transfer.

[0055] The working principle of the heat rod unit is as follows: the liquid ammonia in the evaporation section 103 absorbs the heat of the permafrost from the tube wall, gasifies into steam and the pressure increases accordingly. The gaseous ammonia then flows upward to the condensation section 101 with lower pressure, and turns into liquid again after releasing heat in the condensation section 101. The liquid flows back to the evaporation section 103 along the inner wall of the tube shell by gravity, and then absorbs heat to enter the next cycle. This cycle is repeated, and the absorption, transmission and transfer of permafrost heat is achieved with zero energy consumption and high efficiency.

[0056] Given that the working characteristics of the heat rod are driven by natural temperature differences, only in winter when the atmospheric temperature is lower than the permafrost temperature can the gaseous ammonia in the condensation section of the heat rod be liquefied and flow back to the evaporation section to realize the heat transfer cycle. It cannot work in the warm season when the permafrost is severely degraded, and has seasonal dependence on winter. The warm season is an operating window period, and the refrigeration unit is needed to assist in cooling. It can be seen that the advantages of the heat rod unit are zero energy consumption, high heat transfer efficiency, no mechanical moving parts inside the equipment, and a long service life, generally up to 20 years or more.

[0057] In a specific embodiment of the present invention, Figure 4 , 6As shown, the refrigeration unit includes a cabinet 11, a refrigeration component and a power supply component for providing power thereto. The cabinet 11 is a hollow cylindrical shell. The lower part of the cabinet 11 is a base 12 and the upper part is an equipment compartment 13. The base 12 is connected to the condensing section 101 of the heat rod unit through a flange 4; the power supply component includes an energy storage battery 18, a voltage stabilization controller 17, a wind generator 15 and a solar photovoltaic panel 20. The solar photovoltaic panel 20 is arranged on the outer wall of the cabinet 11, the wind generator 15 is arranged on the top of the equipment compartment 13, and a ventilation window 14 corresponding to the wind generator 15 is provided on the side wall of the cabinet 11. The energy storage battery 18 and the voltage stabilization controller 17 are arranged in the lower compartment 1302 of the equipment compartment 13, and the energy storage battery 18, the wind generator 15 and the solar photovoltaic panel 20 are all connected to the voltage stabilization controller 17. The ventilation window is a blind used to guide air to drive the wind turbine to generate electricity; the solar photovoltaic panel and the wind turbine generate electricity in coordination, and the voltage stabilization controller controls the wind turbine 15 and the solar photovoltaic panel 20 to charge the energy storage battery 18, and controls the energy storage battery 18 to supply power to the compressor 19 load, to prevent the energy storage battery 18 from being overcharged or over-discharged, and to ensure the voltage stability and time continuity of the input power supply of the compressor 19. At the same time, the voltage stabilization controller has a remote control function, that is, it can realize remote dynamic adjustment under unattended conditions.

[0058] like Figure 7 As shown, the refrigeration assembly includes a compressor 19, a condenser 16 and an evaporative refrigerator 21. The compressor 19 and the condenser 16 are respectively arranged in the upper compartment 1301 and the lower compartment 1302 of the equipment compartment 13 in the cabinet 11. The evaporative refrigerator 21 is arranged on the lower outer side of the condensing section 101, and is used to transfer cold to the condensing section 101 to cool down the heat carrier inside the condensing section 101. The evaporative refrigerator 21 is connected to the condenser 16 through a refrigerant pipeline 24, and the outlet of the condenser 16 is connected to the inlet of the compressor 19, and the outlet of the compressor 19 is connected to the evaporative refrigerator 21 through a refrigerant pipeline 24. During assembly, the energy storage battery 18 is arranged above the voltage stabilizer controller 17, the condenser 16 is arranged above the energy storage battery 18, and the compressor 19 is arranged below the voltage stabilizer controller 17.

[0059] During the specific production, the cabinet 11 is made of stainless steel, the cabinet 6 is 1.0 m high and 110 mm in inner diameter, and is divided into an equipment compartment 13 and a base 12 from top to bottom. Among them, the height of the base 12 is 50 cm, and the height of the equipment compartment 13 is 50 cm. An annular flange 4 is welded to the bottom of the base 12, the inner diameter of the flange is equal to the outer diameter of the tube shell 1, the flange width is 2.0 cm, and it is fixedly connected to the flange 4 at the top of the condensing section 101 of the hot rod unit by bolts. The height of the upper compartment 1301 is 25 cm, and the wind turbine 15 and the condenser 16 are installed from top to bottom, and the shutters are installed on the side walls. The height of the lower compartment 1302 is 25 cm, and the energy storage battery 18, the voltage stabilization controller 17 and the compressor 19 are installed from top to bottom. The above components of the equipment compartment 13 are integrated on a multi-layer bracket 2 for easy installation and maintenance.

[0060] A solar photovoltaic panel 20 is laid on the outer wall of the cabinet 11. The solar photovoltaic panel adopts a single crystal silicon flexible solar photovoltaic panel with an output voltage of 24V, a size of 28cm in length, 100cm in height and 2.0mm in thickness.

[0061] The wind power generator 15 adopts a vertical axis magnetic suspension wind turbine generator, with an output voltage of 24V, an operating wind speed range of 2.5 to 25m / s, and an overall size of 15cm in height and 100mm in outer diameter.

[0062] The energy storage battery 18 is a cylindrical plateau-specific low-temperature-resistant high-density colloid battery with an outer diameter of 80 mm and a height of 120 mm, and a rated capacity of 24V10An·h. The energy storage battery 18 is used to store the electricity generated by the wind turbine 15 and the solar photovoltaic panel 20.

[0063] The compressor 19 is a miniature DC variable frequency twin-rotor compressor driven by a 24V DC power supply, with a refrigeration coefficient of 1.2 to 3.0 and an input power of 40 to 120W. The dimensions are an outer diameter of 56.7mm and a height of 92.2mm. The function is to compress the low-pressure and low-temperature refrigerant gas generated by the evaporative refrigerator 21 into a high-pressure and high-temperature gas.

[0064] The condenser 16 is a cylindrical air-cooled steel tube fin condenser with an overall size of 15 cm in height and 60 mm in outer diameter, which dissipates heat by means of the vortex airflow of the wind turbine. Its function is to dissipate the high-pressure and high-temperature refrigerant gas generated by the compressor 19 to the atmosphere and condense into liquid.

[0065] To further optimize the above scheme, an insulation sleeve 22 is provided on the outside of the evaporative refrigerator 21, and the insulation sleeve 22 is composed of two arc-shaped plates, and a gap is provided between the two arc-shaped plates, and the upper end of the arc-shaped plate is connected to the condensing section 101 through a flange 4. The evaporative refrigerator 21 is a cylindrical tube row with openings at the top and bottom. The pipeline adopts a copper tube with a length of 10.0m, an outer diameter of 5mm, and a wall thickness of 1.0mm. The copper tube is evenly arranged in a serpentine loop. The inner diameter of the tube row is 89mm, the height is 10cm, and it has a certain opening and closing elasticity. The evaporative refrigerator 21 is installed within 40cm above the bottom end of the condensing section 101 of the heat rod unit shell 1, so that the refrigerant absorbs the heat of the shell and vaporizes inside it, producing a cooling effect, thereby absorbing the heat of the gaseous ammonia inside the condensing section 101 to liquefy it. The insulation sleeve 22 is installed in a split manner on the outside of the evaporative refrigerator 21, with an inner diameter of 100 mm, a thickness of 50 mm, an outer diameter of 200 mm, and is made of polyurethane. Its function is to prevent the cold energy generated by the evaporative refrigerator 21 from overflowing into the atmosphere, so that all of it can be used to input into the inside of the hot rod shell for condensation and liquefaction of gaseous ammonia.

[0066] like Figure 1 , 6 As shown in Figures 7 and 8, the refrigerant pipeline 24 includes a liquid refrigerant pipe 2401 and a gas refrigerant pipe 2402. The liquid refrigerant pipe 2401 and the gas refrigerant pipe 2402 are both spiral and interlaced on the outer wall of the condensing section 101. The inlet of the evaporative refrigerator 21 is connected to the liquid refrigerant pipe 2401 through the throttle 23, and the inlet of the compressor 19 is connected to the gas refrigerant pipe 2402. The liquid refrigerant pipe 2401 is a copper pipe with an outer diameter of 4.0 mm and a wall thickness of 1.0 mm, and the gas refrigerant pipe 2402 is a copper pipe with an outer diameter of 6 mm and a wall thickness of 1.0 mm. The two copper pipes are spirally interlaced and fixed at the root of the heat dissipation fin 5 of the heat rod shell condensing section 101. The function of the refrigerant pipeline is to accelerate the migration speed of the refrigerant and prevent the heat loss or increase of the refrigerant along the way.

[0067] The throttle 23 is a capillary tube with a length of 0.8m and an inner diameter of 0.4mm, which is used to adjust the pressure and flow of the high-pressure liquid refrigerant, so as to reduce the pressure and turn it into a low-pressure wet vapor state. During production, the capillary tube is embedded in a protective sleeve with a length of 1.0m, an outer diameter of 5mm, and a wall thickness of 1.0mm. The protective sleeve is a copper tube, and a 10cm long connection end is left at each end of the copper tube to facilitate the connection with the liquid refrigerant tube 2401 and the evaporative refrigerator 21, and to provide protection for the capillary tube.

[0068] like Figure 7As shown, the connection relationship of the refrigeration components is that the outlet of the evaporative refrigerator 21 is directly connected to the inlet of the spiral gas refrigerant tube 2402, the outlet of the gas refrigerant tube 2402 is directly connected to the inlet of the compressor 19, the outlet of the compressor 19 is connected to the inlet of the condenser 16 through a copper tube with an outer diameter of 6 mm and a wall thickness of 1.0 mm, the outlet of the condenser is directly connected to the inlet of the spiral liquid refrigerant tube 2401, the outlet of the liquid refrigerant tube 2401 is directly connected to the inlet of the throttle 23, and the outlet of the throttle 23 is directly connected to the inlet of the evaporative refrigerator 21, that is, they are connected in sequence to form a closed circulation loop.

[0069] The model of the refrigerant used in the refrigeration component is R134a. R134a is a refrigerant with zero ozone depletion potential. It will not damage the ozone layer and has little potential impact on the plateau environment. The standard evaporation temperature is -26.2℃, and it has good refrigeration energy efficiency. It can effectively replace the condensation section of the heat rod to liquefy and reflux the gaseous ammonia inside. The function of the refrigerant is to complete the heat conversion in the refrigeration component, efficiently and continuously absorb the heat of the condensation section of the heat rod through the gas-liquid phase change cycle, and release the heat to the atmosphere.

[0070] The working principle of the above refrigeration assembly is as follows: the refrigeration cycle consists of a compression process (compressor), a condensation process (condenser), an expansion process (throttle), and an evaporation process (evaporative refrigerator). First, in the evaporative refrigerator 21, the refrigerant absorbs the heat of the permafrost absorbed by the gaseous heat carrier inside the surrounding hot rod condensation section, thereby vaporizing into a low-temperature, low-pressure gaseous refrigerant. Secondly, the compressor 19, driven by the power supply, inhales the low-temperature, low-pressure gaseous refrigerant of the evaporative refrigerator 21 and compresses it into a high-temperature, high-pressure gaseous refrigerant. Then, the high-temperature, high-pressure gaseous refrigerant enters the condenser 16, and exchanges heat with the external environment (atmospheric environment), releases heat, gradually cools and turns into a high-pressure liquid refrigerant. Subsequently, the liquid refrigerant passes through the throttle 23, and a throttling and pressure reduction effect occurs. The pressure and temperature of the refrigerant are rapidly reduced, and it is transformed into a low-temperature, low-pressure liquid and gas mixture, in which the liquid refrigerant accounts for the majority. After that, the low-temperature, low-pressure refrigerant mixture enters the evaporative evaporator 21 and continues to absorb heat and vaporize. Finally, the evaporated gaseous refrigerant is sucked into the compressor 19 again, and a new round of compression process begins. This cycle repeats, continuously absorbing heat from the condensation section of the hot rod to achieve a refrigeration effect, so that the permafrost is cooled and protected, and the heat is discharged into the atmosphere. In short, it is to use limited refrigerant in the closed refrigeration component, repeatedly compress, condense, expand, and evaporate the refrigerant, and continuously absorb heat and vaporize it at the evaporative refrigerator 21 to perform refrigeration and temperature reduction.

[0071] The working characteristics of the refrigeration unit are that it is driven by power supply, and the refrigeration cycle can be realized throughout the year. It can also work in the warm season when permafrost degradation is serious. It has no seasonal dependence, and there is no operating window period when power supply conditions are met. It can be seen that the advantage is that it can operate in all seasons, and the disadvantage is high energy consumption. The compressor inside the equipment is a mechanical moving part, and its service life is limited by the number of discharges of wind and solar power generation components and energy storage batteries.

[0072] The present invention adopts a heat rod unit and a refrigeration unit to form an all-season heat rod device, and the principle of the functional integration of the two is: the evaporative refrigerator 21 of the refrigeration unit is located at the lower part of the condensing section 101 of the heat rod unit. When the natural convection heat dissipation effect of the air in the upper heat dissipation fin range of the condensing section 101 of the heat rod unit is poor, resulting in the termination of the gas-liquid phase change cycle of the heat carrier inside the tube shell, the refrigeration unit can be turned on, and the evaporative refrigerator 21 can be used to transfer cold to the heat rod condensing section to cool it down, thereby activating the heat transfer cycle inside the heat rod unit.

[0073] The structural combination principle of the refrigeration unit and the hot rod unit is: the hot rod unit and the refrigeration unit are independent closed heat transfer circulation systems. The evaporative cooler 21 of the refrigeration unit is attached to the outside of the condensing section 101 of the hot rod unit, and belongs to the heat transfer enhancement structure of the hot rod unit. The refrigeration unit is a detachable and freely combined auxiliary structure of the hot rod unit. The main cabinet 11 of the refrigeration component is connected and fixed to the hot rod unit by a flange 4. It can be integrated with the hot rod unit as a whole product before leaving the factory, and can also be attached to the hot rod that has been put into operation as a heat transfer enhancement structure.

[0074] The manufacturing process of the all-season heat rod device includes the manufacturing of a heat rod unit, the manufacturing of a refrigeration unit, and the connection of the heat rod unit and the refrigeration unit.

[0075] 1. The production steps of the hot rod unit include:

[0076] 1) Prepare the tube shell of the hot rod unit. Select the tube body that meets the various specifications such as material, diameter, wall thickness and length, and clean and dry it.

[0077] 2) Processing the evaporation section, condensation section, and insulation section. Using argon arc welding technology, weld flanges and heat dissipation fins on the outer walls of the insulation section and evaporation section according to the design plan, and attach a capillary mesh core on the inner wall of the evaporation section.

[0078] 3) Process and install the ejector. According to the design plan, prepare the ejector that meets the material, wall thickness, diameter reduction method and length requirements, and weld it to the inner wall of the shell and tube evaporation section and the insulation section through the ring bracket.

[0079] 4) Welding seal. Using argon arc welding technology, the bottom of the evaporation section is sealed with a flat plate of the same material, and the top of the condensation section is sealed with a spinning head, and the sealing performance has been tested.

[0080] 5) Vacuum treatment. The inside of the hot rod is evacuated through a one-way valve, and combined with heat drying, the vacuum degree reaches 10 -3 Below pa.

[0081] 6) Inject liquid ammonia with a filling volume of 3500g and close the one-way valve.

[0082] 7) Prepare a phase change heat storage sleeve and install it on the outer wall of the evaporation section.

[0083] 2. The production steps of the refrigeration unit include:

[0084] 1) Prepare cabinets and multi-layer brackets. Prepare cabinets and multi-layer brackets that meet the material, outer diameter, wall thickness, height and other specifications according to the design plan, and lay solar photovoltaic panels on the outer wall of the cabinet.

[0085] 2) Equipment installation on multi-layer racks. The power supply components and refrigeration components are integrated and installed on the multi-layer racks, including installing wind turbines and condensers from top to bottom in the upper chamber, and installing energy storage batteries, voltage stabilizer controllers and compressors from top to bottom in the lower chamber.

[0086] 3) Electrical connection: Make electrical connections between the power components and between them and the compressor.

[0087] 4) Refrigeration component pipeline connection. Use oxygen welding technology to weld the pipelines at the condenser inlet and the compressor outlet. Weld a 1.5m long liquid refrigerant pipeline branch and a gas refrigerant pipeline branch at the condenser outlet and the compressor inlet respectively.

[0088] 5) Install the multi-layer bracket inside the cabinet. Put the multi-layer bracket with the components fixed and connected into the cabinet, and fix the multi-layer bracket to the cabinet wall with bolts. At the same time, pass the liquid refrigerant pipeline at the condenser outlet and the gas refrigerant pipeline at the compressor inlet through the reserved hole at the bottom of the equipment compartment and enter the cabinet base.

[0089] 6) Prepare the throttle and evaporative cooler. Prepare the throttle and evaporative cooler that meet the specification requirements according to the design plan, and weld the pipes at the throttle outlet and the evaporative cooler inlet.

[0090] 3. The steps for connecting the heat rod unit and the refrigeration unit include:

[0091] 1) Fix the cabinet to the top of the heat rod unit. Put the base of the cabinet into the top of the heat rod shell, fit the cabinet base flange with the upper flange of the heat pipe shell, align the reserved bolt holes of the two, and fix them with bolts. At the same time, pass the liquid refrigerant pipeline at the condenser outlet and the gas refrigerant pipeline at the compressor inlet through the gap between the cabinet base and the heat rod shell, and extend to the outside of the base.

[0092] 2) Install the throttle and evaporative cooler to the lower part of the condensing section of the heat rod unit. The installation position is within the range of 40cm above the bottom of the wall and is positioned by the flange.

[0093] 3) Install the liquid refrigerant pipeline and the gas refrigerant pipeline. Manually spirally wind the pipe body and fix it on the root of the heat sink fin of the heat rod shell condensation section.

[0094] 4) Refrigeration cycle connection. Use threaded connectors to connect the outlet of the liquid refrigerant pipeline to the inlet of the throttle, and the inlet of the liquid refrigerant pipeline is connected to the outlet of the condenser through the liquid refrigerant pipeline branch. Connect the inlet of the gas refrigerant pipeline to the outlet of the evaporative refrigeration pipe, and connect the outlet of the gas refrigerant pipeline to the inlet of the compressor through the gas refrigerant pipeline branch to form a refrigeration cycle.

[0095] 5) Vacuum the refrigeration cycle and charge the refrigerant. The refrigeration cycle is evacuated through the one-way valve on the compressor to a vacuum degree of 10 -3 pa or less, and then inject refrigerant R134a through the one-way valve with a filling amount of 250g. After the filling is completed, close the one-way valve.

[0096] 6) Install the pre-prepared insulation sleeve on the outside of the evaporative cooler.

[0097] like Fig.10 As shown, the all-season heat rod device provided by the present invention can be applied to roadbed projects. The all-season heat rod device adopts the same on-site layout as ordinary heat rods, that is, it is evenly and symmetrically arranged on both sides of the roadbed. According to the provisions of "Heat Rod" (GB / T 27880), the longitudinal spacing of ordinary heat rods is generally 3.0m to 5.0m, and the longitudinal spacing of all-season heat rods is increased to 5.0 to 8.0m. Of course, it can also be applied to other construction projects, and the specific design and installation of the specific project can be used.

[0098] The beneficial effects of the all-season heat rod device provided by the present invention are as follows:

[0099] The present invention combines traditional heat rods with refrigeration technology to form an all-season heat rod device that can continuously supply cold to permafrost throughout the year, freeing it from seasonal dependence on winter and achieving more real-time and effective maintenance of the thermal stability of permafrost projects. On the basis of the traditional heat rod device, on the one hand, an improvement scheme for its main heat transfer performance is proposed, including a flow guide inside the heat rod and a phase change heat storage sleeve in the external evaporation section. The flow guide has the function of pressurizing and accelerating the gaseous refrigerant, speeding up the gas-liquid up and down circulation efficiency inside the heat rod and improving the heat transfer efficiency. The phase change heat storage sleeve improves the relative relationship between the heat absorption and the temperature drop amplitude of the evaporation section, which is conducive to absorbing and storing more cold and maintaining a lower temperature drop amplitude, thereby improving the gasification rate of liquid ammonia inside the evaporation section and improving the cold output of the heat rod under the same climatic conditions. On the other hand, a refrigeration reinforcement device is proposed for its winter dependence and warm season operation window period. Through the built-in photovoltaic and wind clean energy power generation to drive the compression refrigeration cycle, the negative temperature boundary condition is output to the condensation section of the heat rod, so that the heat rod can also activate the internal gas-liquid phase change cycle in the warm season, thereby having the ability to cool the permafrost in real time in the warm season. Moreover, the refrigeration unit and the heat rod unit belong to two independent closed heat transfer systems, which can be freely combined and disassembled. Therefore, the refrigeration unit can be integrated with the heat rod as an inherent device and used as a whole at the factory, or it can be used as a supplementary device for the heat rod that has been put into field application for the reinforcement of the heat rod.

[0100] The present invention also provides a method for maintaining the stability of permafrost, which uses the all-season heat rod device to cool the permafrost.

[0101] The idea of ​​maintaining thermal stability of permafrost projects is: first, with the heat rod unit as the main body, give full play to the properties of zero energy consumption, efficient heat transfer and long service life of the heat rod, so that the permafrost can reserve cold in advance in winter to indirectly resist thermal erosion in the warm season and disturbances caused by engineering activities. Secondly, with the refrigeration unit as the auxiliary body, according to the temperature rise of the permafrost and the change of thermal stability state, the refrigeration unit is flexibly started to enhance the natural heat transfer efficiency of the heat rod in the cold season, or activate the heat rod in the warm season to shorten the window period of the heat rod operation, and fully volatilize the functional properties of the refrigeration unit that can output negative temperature cold in a positive temperature environment, so that the permafrost can further increase the winter cold storage on the basis of the heat rod, and obtain cold in the warm season to eliminate thermal erosion in real time, and strictly control the heat balance relationship and temperature changes of the permafrost.

[0102] Since there are no mechanical moving parts inside the heat rod unit, it does not require external energy to drive it, has zero energy consumption, and has a long service life, the heat rod unit is in standby mode all year round. Once the atmospheric temperature is lower than the annual temperature of permafrost, the heat rod unit will enter the gas-liquid phase change cycle heat transfer state.

[0103] In view of the presence of a mechanical moving component, the compressor 7, inside the refrigeration unit, which requires electrical energy to drive, its service life is limited by the operating time ratio of the compressor 7 and the number of discharges of the energy storage battery 14 of the power supply component. Therefore, the operating time of the refrigeration unit should be shortened as much as possible while ensuring the thermal stability of permafrost.

[0104] According to the requirements of the Technical Specifications for Design and Construction of Highways in Permafrost Areas (JTG / T 3331) and other specifications, the thermal stability of permafrost is divided into four levels according to the temperature level, namely low-temperature stable permafrost (<-2.5 ℃), low-temperature basically stable permafrost (-2.5~-1.5 ℃), high-temperature unstable permafrost (-1.5~-0.5 ℃), and high-temperature extremely unstable permafrost (-0.5~0 ℃). Therefore, considering the comprehensive cooling effect of the heat transfer process of the hot rod unit and the refrigeration unit on the permafrost, a "pinch point" operation control method for the all-season hot rod refrigeration unit is proposed. The pinch point has three states: cold state (pinch point temperature is -2.5 ℃), warm state (pinch point temperature is -1.5 ℃) and hot state (pinch point temperature is -0.5 ℃).

[0105] The execution principle of the "pinch point" operation control method is: when permafrost warms up and degrades, its own heat balance relationship is a deficit, that is, the heat exchange process between it and the atmospheric environment can be regarded as the atmospheric environment inputting a heat flow to the permafrost, while the heat rod unit and the refrigeration unit respectively input a cold flow to the permafrost.

[0106] The specific steps are as follows:

[0107] (1) When the permafrost temperature is less than -2.5°C, that is, when it is low-temperature stable permafrost, the annual average heat flux from the atmosphere to the permafrost is ≤0, the pinch point is not activated, it is in a cold state, and the heat rod unit does not operate;

[0108] (2) When the permafrost temperature is ≥-2.5℃ and <-1.5℃, the permafrost temperature moves below the cold pinch point temperature and enters the warm state. The annual average heat flux from the atmosphere to the permafrost is >0, and the heat rod unit operates. However, the cold flux of the heat rod unit is basically the same as the heat flux of the atmospheric environment, and the refrigeration unit does not start.

[0109] (3) When the permafrost temperature is ≥-1.5℃ and <-0.5℃, the permafrost temperature moves past the pinch point temperature of the warm state and enters the subthermal state, where it begins to breed lesions. At this time, the cold flux of the heat rod unit is difficult to balance the heat flux of the atmospheric environment. Therefore, in addition to the operation of the heat rod unit, the refrigeration unit needs to be started to control the deterioration trend of the permafrost subthermal state and then restore it to the warm state as soon as possible. At this time, the refrigeration unit adopts an intermittent operation mode. Due to the strong thermal inertia of permafrost and the insignificant temperature change in a short period of time compared with the same period of previous years, the operation mode is set according to a monthly ratio. The start and stop time is determined based on the monthly cold and heat flow balance relationship and the permafrost temperature change rate, and is calculated and determined according to formulas (1) and (2):

[0110] (1)

[0111] In the formula, H i is the average monthly cooling requirement in the permafrost control area corresponding to the i-th all-season heat rod device, kJ; CP A , CP T are the monthly average heat capacity flow rates of the atmospheric heat flux and the heat rod unit cold flux in the permafrost control area corresponding to the i-th all-season heat rod device, kW / ℃; T i is the average permafrost temperature in the control area of ​​the i-th all-season heat rod device; m i is the mass of permafrost in the control area of ​​the i-th all-season thermal rod device, kg; c i is the specific heat capacity of permafrost in the control area of ​​the i-th all-season heat rod device, kJ / (kg·℃); ΔT i is the change in the monthly average temperature of permafrost in the control area of ​​the ith all-season heat rod device compared with the same month in previous stable years, ℃.

[0112] (2)

[0113] In the formula, t i is the required daily operating time of the refrigeration unit of the i-th all-season heat rod device, h; N is the number of days in the corresponding month; q i is the cooling power of the refrigeration unit of the i-th all-season heat rod device, W.

[0114] (4) When the permafrost temperature is ≥ -0.5℃, the permafrost temperature moves past the pinch point temperature of the superheated state and enters the hot state. At this time, the permafrost is close to the critical point of degradation and thawing, and creep deformation and thermal thaw deformation will occur. At this time, the refrigeration unit must be controlled to operate continuously at full capacity to output the maximum cooling potential, restore the permafrost to the subthermal state as soon as possible (the permafrost temperature drops below -0.5℃), and then deal with it according to the subthermal control plan. The refrigeration unit executes according to step (3).

[0115] In view of this, a convenient and fast operation method of the all-season heat rod device is provided, in which the soil at the middle position of two adjacent all-season heat rod devices is used as the monitoring object, that is, the operation mode of the all-season heat rod is controlled according to the thermal stability state of the most unfavorable position.

[0116] 1) When the permafrost temperature is ≥-0.5℃, which is high-temperature and extremely unstable permafrost, the all-season heat rod solution is immediately implemented. Through the remote control function of voltage stability control, the refrigeration unit is adjusted to a full-time continuous open state, that is, as long as the power unit can output power, the refrigeration unit is in the open state regardless of the season.

[0117] 2) When the permafrost temperature is <-0.5℃ but ≥-1.5℃, which is high-temperature unstable permafrost, the full-season heat rod scheme is implemented. The heat rod unit is in operation and the refrigeration unit is turned on intermittently. The control scheme is set according to one operation mode per month, and the required daily operation time is calculated and determined by formulas (1) and (2).

[0118] 3) When the permafrost temperature is <-1.5 ℃ but ≥-2.5 ℃, that is, it is low-temperature basically stable permafrost, the ordinary heat rod scheme is implemented, the heat rod unit is operated, and the refrigeration unit is shut down.

[0119] 4) When the permafrost temperature is <-2.5 ℃, that is, it is low-temperature stable frozen soil, the thermal rod scheme will not be implemented.

[0120] In summary, the all-season heat rod device provided by the present invention has the technical effects of convenient transportation and installation, good scene adaptability, reliable operation and intelligence; the permafrost stability maintenance method provided can coordinate the implementation of the heat rod unit and the refrigeration unit, and the functional integration of the two achieves the purpose of permafrost stability, and solves the technical problems of strong winter dependence, long operation window period and poor seasonal matching of the heat rods used to protect permafrost; the dual goals of permafrost protection and energy saving and efficiency improvement are achieved.

[0121] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the scope of protection of the claims of the present invention.

Claims

1. A method for maintaining the stability of permafrost, characterized in that: An all-season heat rod device is used to cool permafrost. The all-season heat rod device includes a heat rod unit and a refrigeration unit. The heat rod unit is divided into a condensation section, an insulation section and an evaporation section from top to bottom. The condensation section is arranged above the ground surface, the insulation section is arranged in the seasonal active layer of the frozen soil, and the evaporation section is arranged in the permafrost layer. An ejector is arranged in the insulation section to eject the gaseous heat carrier at the lower part of the evaporation section into the upper condensation section. The refrigeration unit is arranged at the top of the condensation section of the heat rod unit to absorb the heat of the condensation section and release it into the atmosphere. The heat rod unit comprises a tube shell, heat dissipation fins, an ejector and a phase-change heat storage sleeve. The tube shell is a tubular structure sealed at the top and bottom. The heat dissipation fins are arranged outside the tube shell of the condensing section, and the ejector is arranged inside the tube shell of the insulation section. The outlet end of the ejector extends into the tube shell of the condensing section, and the inlet end extends into the tube shell of the evaporation section. The phase-change heat storage sleeve is arranged outside the tube shell of the evaporation section. An annular cavity is arranged between the tube shell of the evaporation section and the phase-change heat storage sleeve, and the upper and lower ends are sealed. The annular cavity is filled with phase-change material. The phase change heat storage sleeve is a sandwich tube made of 201 stainless steel, the wall thickness of the phase change heat storage sleeve is 1.0 mm, the inner diameter is equal to the outer diameter of the tube shell, the thickness of the phase change heat storage sleeve is 3.0 cm, and the length of the phase change heat storage sleeve is equal to the length of the evaporation section; the phase change material selects a solid-liquid nano eutectic negative temperature phase change material, and the critical phase change temperature is taken as the average ground temperature value within the permafrost protection depth range minus 0.5°C; A positioning base is fixed to the outside of the tube shell of the thermal insulation section, a concrete foundation is provided on the top of the positioning base, the concrete foundation is arranged above the ground surface, and the positioning base is arranged below the ground surface; A capillary mesh core is provided on the inner wall of the tube shell of the evaporation section. The capillary mesh core is composed of a plurality of pieces, which are arranged at intervals along the inner wall of the tube shell in the circumferential direction. The length of the capillary mesh core is equal to the length of the evaporation section, and the coverage area of ​​the capillary mesh core is 50% of the total area of ​​the inner wall of the tube shell of the evaporation section. The following steps are involved: (1) When the permafrost temperature is less than -2.5°C, the heat flux from the atmosphere to the permafrost is ≤ 0, and the heat rod unit does not operate; (2) When the permafrost temperature is ≥ -2.5°C and < -1.5°C, the heat flux from the atmosphere to the permafrost is > 0, the heat rod unit starts to operate, and the refrigeration unit does not start; (3) When the permafrost temperature is ≥ -1.5℃ and < -0.5℃, the heating unit operates and the refrigeration unit operates intermittently. The start and stop time of the refrigeration unit is calculated and determined according to the following formulas (1) and (2): （1） In the formula, H i is the average monthly cooling requirement in the permafrost control area corresponding to the i-th all-season heat rod device, kJ; CP A , CP T are the monthly average heat capacity flow rates of the atmospheric ambient heat flux and the heat rod unit cold flux in the control area of ​​the i-th all-season heat rod device, kJ / ℃; T i is the average permafrost temperature in the control area of ​​the i-th all-season heat rod device; m i is the mass of permafrost in the control area of ​​the i-th all-season thermal rod device, kg; c i is the specific heat capacity of permafrost in the control area of ​​the i-th all-season heat rod device, kJ / (kg·℃); Δ T i is the change in the monthly average temperature of permafrost in the control area of ​​the i-th all-season heat rod device compared with the same month in previous stable years, ℃; （2） In the formula, t i is the daily required operating time of the refrigeration unit of the i-th all-season heat rod device, s; N is the number of days in the corresponding month; q is the cooling power of the refrigeration unit of the i-th all-season heat rod device, W; (4) When the permafrost temperature is ≥ -0.5°C, the refrigeration unit operates at full capacity until the permafrost temperature drops below -0.5°C, and the refrigeration unit executes according to step (3).

2. A method for maintaining the stability of permafrost according to claim 1, characterized in that: The refrigeration unit comprises a cabinet, a refrigeration component and a power supply component for providing power thereto, the cabinet is a hollow cylindrical shell, the bottom of the cabinet is connected to the condensing section of the heat rod unit through a flange; the power supply component comprises an energy storage battery, a voltage stabilization controller, a wind generator and a solar photovoltaic panel, the solar photovoltaic panel is arranged on the outer wall of the cabinet, the wind generator is arranged on the top of the cabinet, the side wall of the cabinet is provided with a ventilation window corresponding to the wind generator, the energy storage battery and the voltage stabilization controller are arranged at the lower part of the cabinet, and the energy storage battery, the wind generator and the solar photovoltaic panel are all connected to the voltage stabilization controller; The refrigeration assembly includes a compressor, a condenser and an evaporative refrigerator. The compressor and the condenser are arranged inside the cabinet. The evaporative refrigerator is arranged on the lower outer side of the condensing section and is used to supply cold to the condensing section to cool the heat carrier inside the condensing section. The evaporative refrigerator is connected to the condenser through a refrigerant pipeline. The outlet of the condenser is connected to the inlet of the compressor. The outlet of the compressor is connected to the evaporative refrigerator through a refrigerant pipeline. The cabinet is made of stainless steel, with a height of 1.0 m and an inner diameter of 110 mm. It is divided into an equipment compartment and a base. The height of the base is 50 cm, and the height of the equipment compartment is 50 cm. An annular flange is welded at the bottom of the base. The inner diameter of the flange is equal to the outer diameter of the tube shell. The flange width is 2.0 cm. It is fixedly connected to the flange at the top of the condensing section of the hot rod unit by bolts. The height of the upper compartment of the equipment compartment is 25 cm. The wind turbine and condenser are installed from top to bottom, and shutters are installed on the side walls. The height of the lower compartment of the equipment compartment is 25 cm. The energy storage battery, voltage stabilization controller and compressor are installed from top to bottom. The above components of the equipment compartment are integrated on a multi-layer bracket. The evaporative refrigerator is arranged above the ground surface. A heat preservation sleeve is arranged outside the evaporative refrigerator. The heat preservation sleeve is composed of two arc-shaped plates with a gap between the two arc-shaped plates. The upper end of the arc-shaped plate is connected to the condensing section through a flange.

3. A method for maintaining the stability of permafrost according to claim 1, characterized in that: The ejector comprises a nozzle, a contraction section, a mixing section and an expansion section from bottom to top, wherein the nozzle and the contraction section are both reducers with a small top and a large bottom, the mixing section is a straight tube connecting the contraction section and the expansion section from top to bottom, and the expansion section is a reducer with a large top and a small bottom.

4. A method for maintaining the stability of permafrost according to claim 3, characterized in that: The small diameter ends of the contraction section and the expansion section are the same as the inner diameter of the mixing section. The contraction section and the expansion section are the same in length. The length of the mixing section is less than that of the contraction section and the expansion section.

5. A method for maintaining the stability of permafrost according to claim 2, characterized in that: The refrigerant pipeline includes a liquid refrigerant pipe and a gas refrigerant pipe, both of which are spiral and interlaced on the outer wall of the condensing section. The inlet of the evaporative refrigerator is connected to the liquid refrigerant pipe through a throttle, and the inlet of the compressor is connected to the gas refrigerant pipe.

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