CN118376118B - Mine water heat storage device and method for reconstructing abandoned coal mine shaft - Google Patents
Mine water heat storage device and method for reconstructing abandoned coal mine shaft Download PDFInfo
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Abstract
A mine water heat storage device and method based on reconstruction and reconstruction of abandoned coal mine shafts, the device comprises: a sealing and filling section is arranged at the bottom of the waste coal mine shaft and at the communication position of the bottom and the horizontal roadway, a sealing section is arranged at the top of the waste coal mine shaft, and a shaft between the sealing and filling section and the sealing section is a water storage and heat storage section; two through holes for burying the water inlet pipe and the water outlet pipe are axially formed in the sealing section along the shaft of the sealing section, the lower end of the water inlet pipe stretches into the position, close to the bottom, of the water storage and heat storage section, and the lower end of the water outlet pipe stretches into the position, close to the top, of the water storage and heat storage section. The method comprises the following steps: the method comprises the steps of investigation of waste coal mine shaft production-pit closing parameters, unsealing and detecting peeping of waste coal mine shaft drilling, calculation of hydrogeologic parameters based on waste coal mine shaft pumping tests, closed reinforcement grouting, reconstruction of well walls, volume determination and simulation of heat storage effects of 3D hydrogeology and pumping and filling schemes. The device and the method realize transformation from waste coal mine shafts to the green heat storage system, cross-season water storage and heat storage and heating to buildings around mining areas.
Description
Technical Field
The invention relates to a mine water heat storage device and method for reconstructing abandoned coal mine shafts based on reconstruction, and belongs to the technical field of collaborative development and utilization of underground space energy storage and renewable energy sources.
Background
A large amount of underground roadway space is left after the mine is abandoned, and the abandoned space is submerged by the underground mine water after drainage is stopped, so that the low-grade heat energy storage with the mine water as a working medium can be developed. The underground heat energy storage is used as a unique heat storage method, different geological structures below the earth surface are used as a container, water or compressed air and the like are used as energy storage media, and the method has the advantages of low storage cost, long storage period, large storage capacity, no occupation of ground space and the like. At present, the sensible heat storage of groundwater is mainly of the following types: drilling heat storage, underground water tank heat storage, aquifer heat storage and abandoned mine heat storage. After the pit is closed, the stope collapses and the tunnel collapses, and the shaft is used as a concrete masonry structure, so that the support strength is high, the service life is long, the longitudinal space is large, and the underground heat storage of large-volume mine water is more suitable to be developed.
The abandoned coal mine shaft is subjected to the service of mineral resource development period, so that the degradation phenomena such as well wall cracking, water permeability, corrosion, carbonization and the like are easy to occur, and the problems such as water leakage and heat loss when mine water is stored are difficult to effectively solve in the current research of the abandoned coal mine shaft.
Disclosure of Invention
The invention provides a mine water heat storage device and a method for reconstructing waste coal mine shafts, the device and the method can realize transformation from waste coal mine shafts to the green heat storage system, and realize cross-season water storage and heat storage and heating to buildings around the mining area.
In order to achieve the above purpose, the invention provides a mine water heat storage device based on reconstruction and reconstruction of a waste coal mine shaft, which comprises a waste coal mine shaft, wherein a sealing section is arranged at the communication part of the bottom of the waste coal mine shaft and a horizontal roadway, a sealing section is arranged at the top of the waste coal mine shaft, and the shaft between the sealing section and the sealing section is a water storage heat storage section; two through holes for burying a water inlet pipe and a water outlet pipe are formed in the sealing section along the radial direction of the sealing section, the lower end of the water inlet pipe stretches into the position, close to the bottom, of the water storage and heat storage section, and the lower end of the water outlet pipe stretches into the position, close to the top, of the water storage and heat storage section; the upper ends of the water inlet pipe and the water outlet pipe extend out of the top of the sealing section.
Further, the water inlet pipe and the water outlet pipe are symmetrical about the central axis of the waste coal mine shaft, and the distances between the water inlet pipe and the water outlet pipe and the central axis of the waste coal mine shaft are respectivelyD is the inner diameter of the shaft; the water inlet pipe extends to the position of the water storage and heat storage section, which is at the position of H/4 from the top of the sealing and filling section, wherein H is the height of the water storage and heat storage section; the water outlet pipe extends into the water storage and heat storage section to be at a position which is H/4 of the bottom of the closed section.
Further, the lower end of the water inlet pipe is communicated with a horizontal pipeline extending to the position where the central shaft of the shaft is located.
Further, the shaft of the water storage and heat storage section is reinforced by grouting after passing through the wall, and a low-heat-conductivity nano material is added into the grouting; the sealing section is a sealing well cover, the diameter of the sealing section is at least 2m larger than that of a shaft, and the thickness of the sealing section is larger than 1m.
A mine water heat storage method based on reconstruction and reconstruction of abandoned coal mine shafts comprises the following steps:
Step one, carrying out production of abandoned coal mine shafts and investigation of pit closing parameters, wherein the investigation comprises main production technical data of a mine, position coordinates of the mine, types of the mine, materials of a well pipe of the mine, diameters of the mine, depths of the mine, mine structure drawings, stratum profile of the mine, hydrogeological data of stratum of the mine, construction design and completion report of pit closing; the mine main production technical data graph comprises an uphole underground comparison graph, a mining engineering plan graph and an industrial site floor plan graph;
Step two, evaluating the integrity of the abandoned coal mine shaft, including unsealing a central drilling hole of a shaft sealing section, sampling shaft wall concrete, sampling shaft mine water, monitoring shaft mine water level, detecting shaft wall integrity and shaft lane connectivity, and resealing the central drilling hole of the shaft sealing section, wherein the shaft wall integrity and the shaft lane connectivity are peeped through an underwater camera; carrying out water temperature and salt depth profile monitoring of a shaft and a mine according to field conditions, and finishing evaluation analysis report of the integrity and availability of the abandoned coal mine shaft;
Step three, for the abandoned coal mine shaft determined in the step two, a mining submersible pump is arranged through a central drilling hole of a sealing section, a flow-time and water level deep-down-time curve is obtained through carrying out a single-hole large-flow steady flow pumping test in a large-diameter shaft, and shaft stratum hydrogeological parameters such as a mining effect radius R, a permeability coefficient K and the like of the abandoned coal mine shaft are calculated through iteration of the following standard formula: ；
Wherein q is pumping flow, and the unit is m 3/s; s is the descending depth, unit m; r is the radius of the shaft, unit m; m is well depth, unit M;
step four, according to the shaft water pumping test result, if K ' is less than or equal to K ', wherein K ' is the formation permeability coefficient of the shaft in the production period, the fact that the waste coal mine shaft water stores the heat is considered to have a water sealing-like effect, and the influence of seepage of the mine water through the shaft wall on the heat storage performance is ignored;
If the obtained K is more than K', the situation that the wall of the waste coal mine shaft is broken and deformed is considered, seepage and migration of shaft mine water and surrounding stratum groundwater are obvious, and the heat storage effect of the shaft mine water is affected; adopting measures of underwater concrete injection and grouting sealing and reinforcing of the well wall after the well wall damage point by combining the waste coal mine well wall integrity detection peeping result; continuously performing measure effect test, performing secondary water pumping test, if K > K' still exists, continuously performing reconstruction of the wall of the waste coal mine shaft (1), prefabricating the complete wall in sections, and reconstructing the complete wall by a sunk well method to form an inner wall which is smaller than the original waste shaft but coaxial with the complete wall, wherein the reconstructed inner wall has the same thickness as the original wall, and a new water storage and heat storage section formed by the inner wall is used for storing mine water; determining the heat storage volume of the mine water of the shaft according to the reconstructed shaft parameters, the ground heat supply load and the heat loss in the heat storage period;
Taking mine water in a shaft and stratum around the shaft as combined heat storage bodies, considering that the heat storage capacity of the heat storage mine water volume and surrounding rock soil is related to heat storage heat source heat, winter heating building heat load and heat loss of a heat storage system, and determining the heat storage capacity of the mine water in the shaft by adopting the following method: assuming the heat load Q load required by heating building heating area in winter, the heat storage quantity of pit shaft mine water is derived from solar energy, and provided by the total solar heat collection quantity Q c and the heat storage quantity Q s of pit shaft mine water heat storage system to overcome heat storage loss Q loss, there are: ；
In the early stage of the solar cross-season underground heat storage system, the solar heat collector transmits heat to water bodies in a mine shaft, so that the water temperature is gradually increased; this heat is transferred from the body of water to the formations surrounding the wellbore, causing the temperature of the rock and earth contacting the body of water to rise; warmer rock soil spreads heat further to a wider area;
when entering a heating season, the temperature of the mine water body in the shaft gradually decreases due to continuous heat extraction; at this time, the heat transferred from the solar collector to the surrounding rock stratum is far greater than the heat recovered from the surrounding rock stratum, namely Q loss >0;
Along with the long-term operation of the system, a shaft water body and a stratum surrounding rock heat storage layer are formed; in heating season, if the temperature of the water body of the shaft is reduced due to heat extraction, the surrounding rock stratum releases the heat stored in the surrounding rock stratum to the water body of the shaft, so that the temperature of the water body of the shaft is gradually raised, the surrounding rock stratum plays a role in heat storage, namely, the heat flows out of Q loss <0 of the surrounding rock, so that a transition period that Q loss tends to zero exists, and the heat received by the water body of the shaft and the heat released by the surrounding rock stratum reach dynamic balance; if the heat injection is stopped at this point, the system will maintain this equilibrium, then there are: ；
In the method, in the process of the invention, Is mine water density, kg/m 3; Constant pressure specific heat capacity, unit J/(kg.K); t is the temperature of the water body of the shaft; t 0 is the indoor required temperature in winter; q wc is the heat collection quantity at the moment in winter; For the water intake flow at the moment, the unit is m 3/h;
The heat storage volume V of the mine water in the shaft is determined according to the water taking flow and the specified water changing times n at the moment: ；
step five, establishing a geometric model and a numerical calculation model control equation of a shaft and surrounding stratum according to the selected abandoned coal mine shaft, and setting different working condition parameters and combinations, including boundary and initial condition parameters such as the heat storage volume of the mine water of the shaft, the positions of a water inlet pipe and a water outlet pipe, initial and target temperatures, the permeability coefficient of the abandoned coal mine shaft and the stratum and the like; adopting numerical simulation software to develop a wellbore mine water heat storage scheme numerical simulation experiment based on a 3D hydrogeological model, analyzing a mine water heat storage temperature decay change rule, determining an optimal permeability coefficient, a heat storage action radius, heat storage heat cycle characteristics and a parameter combination scheme, and comprehensively analyzing the waste coal mine wellbore mine water heat storage availability;
In the process of heating and heat storage of fluid in a shaft, convection heat transfer follows mass conservation, momentum conservation and energy conservation equations, and a basic control equation is expressed as follows:
The mass conservation equation is expressed in fluid mechanics as a continuous equation, i.e., the increase in mass per unit time of a fluid microcell is equal to the net mass flowing into the microcell over the same interval, and its differential expression is as follows: ；
In the method, in the process of the invention, Respectively representing velocity components of the fluid micro-mass in the x, y and z directions, and the unit is m/s;
Conservation of momentum, i.e., the rate of change of the momentum of a fluid in a microbody over time, is equal to the sum of various external forces that are exerted on the microbody by the outside world, and for viscous incompressible flows, the momentum equations in the x, y, z directions are also known as follows: ；
In the method, in the process of the invention, Respectively representing the velocity components in the x, y and z axis directions, and the unit is m/s; tangential stress of the surface of the micro-element body is unit pa; The unit mass force in the x, y and z directions is unit m/s 2;
Energy conservation equation: ；
In the method, in the process of the invention, Is thermal diffusivity, unit，Wherein, the method comprises the steps of, wherein,The heat transfer coefficient of the fluid is expressed as the unit w/(m.K); Is a viscous dissipation term; Is a volumetric heat source;
For the surrounding rock of the shaft, the surrounding rock is only regarded as solid in preliminary research, and the influence of seepage flow heat exchange of the porous medium on heat accumulation is not considered, wherein the energy conservation equation of the surrounding rock is an unsteady heat conduction differential equation, namely: ；
Further, the positions of the water inlet pipe and the water outlet pipe in the fifth step are determined by adopting an equal circular ring surface method, and the process is as follows:
for a shaft with the inner diameter D, the water inlet pipe and the water outlet pipe are arranged on the diameter line of the circular cross section of the same shaft, the water inlet pipe and the water outlet pipe are respectively arranged on two sides of the center of the shaft, and the pipe distribution position is calculated by adopting the following formula: ；
Wherein i is the serial number of the equal-circle surface, and i=1, 2 and 3 . . . . . . from the center of the cross section circle of the shaft; n is an equal fraction or number of torus, n=1, 2,3.,; the mine water volume stored under each circular ring under the same water storage shaft height is equal.
Further, the selection of the 3D numerical simulation geometric model in the fifth step is divided into two types, namely, an irregular geometric model containing a well bore and a whole mine range, and a cylinder/cube/cuboid regular geometric model containing a well bore and a nearby stratum.
According to the method, a proper water storage and heat storage system is established by utilizing a sealing reinforcement measure according to the specific condition of the abandoned coal mine shaft, so that the normal water circulation operation and energy exchange of the water storage and heat storage section of the abandoned coal mine shaft are realized. The method can realize storage of different industrial waste heat sources and seasonal scale time delay conversion of energy by investigating waste coal mine shaft production-pit closing parameters, unsealing and detecting peeping of waste coal mine shaft drilling, hydrogeologic parameter calculation based on waste coal mine shaft pumping test, sealing reinforcing grouting, well wall reconstruction and volume determination, and 3D hydrogeology and pumping and filling scheme heat storage effect simulation, and is more environment-friendly and simple in principle compared with the existing energy storage system. The system adopts a high-efficiency energy storage mode, namely adopts physical medium to store energy, has long service life, low site selection requirement, no extra occupied ground space and low construction cost; compared with the traditional heat energy storage system, the invention reduces the initial investment of the energy storage system, expands the application range of the system, comprehensively utilizes the waste coal mine shaft and underground shallow geothermal energy while effectively solving the heat storage engineering problems such as water leakage, heat loss and the like, reduces the heat storage cost, improves the heat storage efficiency, realizes the secondary utilization of the waste coal mine shaft, and is beneficial to accelerating the formation of new quality production capacity of the waste coal mine transformation development.
Drawings
FIG. 1 is a schematic diagram of the structure of the present invention;
FIG. 2 is a flow chart of the method of the present invention;
FIG. 3 is a schematic illustration of an isocyclic approach;
FIG. 4 is a schematic view of the positions of a water inlet pipe and a water outlet pipe determined by an equal circular ring method according to the embodiment of the invention;
FIG. 5 is a two-dimensional plan view of a mine according to an embodiment of the present invention;
FIG. 6 is a 3D map of an entire mine of an embodiment of the present invention;
FIG. 7 is a grid view of an embodiment of the present invention;
FIG. 8 is a diagram of a 3D numerical model cuboid rule geometry meshing scheme in accordance with an embodiment of the present invention;
FIG. 9 is an axial cross-sectional temperature profile of a wellbore storing hot water for four months in accordance with an embodiment of the present invention;
FIG. 10 is a radial cross-sectional temperature profile of a wellbore storing hot water for four months in accordance with an embodiment of the present invention;
FIG. 11 is a temperature cloud plot of a water body cross-section at the top of a wellbore in accordance with an embodiment of the invention;
FIG. 12 is a temperature cloud of a water body section at the bottom of a wellbore in an embodiment of the invention.
In the figure: 1. the device comprises a shaft, 2 horizontal roadways, 3 sealing and filling sections, 4 sealing sections, 5 water storage and heat storage sections, 6 water inlet pipes, 7 water outlet pipes, 8 horizontal pipelines, 9 and grouting liquid.
Detailed Description
The invention is further described below with reference to the accompanying drawings.
As shown in fig. 1, the mine water heat storage device based on reconstruction and reconstruction of waste coal mine shafts comprises a waste coal mine shaft 1, wherein a sealing section 3 is arranged at the communication part of the bottom of the waste coal mine shaft 1 and a horizontal roadway 2, a sealing section 4 is arranged at the top of the waste coal mine shaft, and a shaft between the sealing section 3 and the sealing section 4 is a water storage heat storage section 5; two through holes for burying a water inlet pipe 6 and a water outlet pipe 7 are formed in the sealing section 4 along the radial direction of the sealing section, the lower end of the water inlet pipe 6 stretches into the position, close to the bottom, of the water storage and heat storage section 5, and the lower end of the water outlet pipe 7 stretches into the position, close to the top, of the water storage and heat storage section; the upper ends of the water inlet pipe 6 and the water outlet pipe 7 extend out of the top of the sealing section 4.
As a preferred embodiment, the water inlet pipe 6 and the water outlet pipe 7 are symmetrical with respect to the central axis of the waste coal mine shaft 1, and the distance between the water inlet pipe 6 and the water outlet pipe 7 and the central axis of the waste coal mine shaft is equal toD is the inner diameter of the shaft; the water inlet pipe 6 extends to the position of the water storage and heat storage section 5, which is at the position of H/4 from the top of the sealing and filling section 3, wherein H is the height of the water storage and heat storage section 5; the water outlet pipe 7 extends into the water storage and heat storage section 5 to be at a position which is far from the bottom H/4 of the sealing section 4.
In order to achieve more uniform mixing of the water in the water inlet and the water in the shaft and prevent thermal stratification, the lower end of the water inlet pipe 6 is communicated with a horizontal pipeline 8 extending to the position where the central shaft of the shaft 1 is located.
In order to further reduce the heat conductivity coefficient of the stratum reinforced by post-grouting on the wall of the well bore and the total heat conductivity coefficient of mine water in the well bore, the well bore of the water storage and heat storage section 5 is reinforced by post-grouting on the wall, and nano materials with low heat conductivity coefficients are added in grouting liquid 9; in order to further improve the tightness of the water storage and heat storage section 5, the sealing section 4 is a sealing well cover, the diameter of the sealing well cover is at least 2m larger than that of the shaft 1, and the thickness of the sealing well cover is larger than 1m.
As shown in fig. 2, the mine water heat storage method based on reconstruction and reconstruction of the abandoned coal mine shaft comprises the following steps:
Step one, carrying out production and pit closing parameter investigation of abandoned coal mine shafts 1, wherein the investigation comprises main production technical data graphs of mines, position coordinates of the mines, types of the mines, materials of well pipes of the mines, diameters of the mines, depths of the mines, mine structure drawings, stratum profile drawings of the shafts, hydrogeological data of stratum of the shafts, construction design and completion reports of pit closing; the mine main production technical data graph comprises an uphole underground comparison graph, a mining engineering plan graph and an industrial site floor plan graph;
Step two, evaluating the integrity of the abandoned coal mine shaft 1, including unsealing a central drilling hole of a sealing section of the shaft 1, sampling well wall concrete, sampling well water of the shaft, monitoring the well water level of the shaft, detecting the integrity of the well wall and connectivity of a well lane, and resealing the central drilling hole of the sealing section of the shaft, wherein the integrity of the well wall and the connectivity of the well lane are peeped through an underwater camera; carrying out water temperature and salt depth profile monitoring of a shaft 1 according to field conditions to finish evaluation reports of the integrity and availability of the abandoned coal mine shaft 1;
Step three, installing a mining submersible pump for the available abandoned coal mine shaft 1 determined in the step two, obtaining flow-time and water level deep-time curves by carrying out a single-hole drilling and high-flow steady flow pumping test in the large-diameter shaft 1, and iteratively calculating stratum hydrogeological parameters of the shaft 1 such as the extraction influence radius R, the permeability coefficient K and the like of the abandoned coal mine shaft water shaft 1 according to the following standard formula: ；
Wherein q is pumping flow, and the unit is m 3/s; s is the descending depth, unit m; r is the radius of the shaft, unit m; m is well depth, unit M;
Step four, according to the shaft water pumping test result, if K ' is less than or equal to K ', wherein K ' is the formation permeability coefficient of the shaft in the production period, the fact that the waste coal mine shaft 1 mine water stores heat has a water sealing-like effect is considered, and the influence of seepage of the mine water through the wall of the shaft 1 on heat storage performance is ignored;
If the obtained K is more than K', determining that the wall of the waste coal mine shaft 1 is broken and deformed, and seepage and migration of mine water of the shaft and underground water of surrounding stratum are obvious, so that the heat storage effect of the mine water of the shaft is affected, and adopting measures of underwater shotcrete and grouting after the wall to seal and strengthen the wall of the shaft at a broken point of the wall by combining the detection peeping result of the integrity of the wall of the waste coal mine shaft 1, wherein nano materials with low heat conductivity coefficient are added into grouting liquid 9 in the measure of grouting after the wall; further carrying out measure effect test, carrying out secondary water pumping test, if K > K' still exists, carrying out reconstruction of the wall of the waste coal mine shaft 1, prefabricating a complete wall of the shaft, and reconstructing the complete wall of the shaft by a sunk well method to form an inner wall which is smaller than the original waste shaft 1 but coaxial with the complete wall of the shaft, wherein the reconstructed inner wall of the shaft is kept to be the same as the original wall of the shaft in thickness, and a new water storage and heat storage section formed by the inner wall of the shaft is used for storing mine water; determining the mine water heat storage volume of the pit shaft 1 according to the reconstructed pit shaft 1 parameters, the ground heat supply load and the heat loss in the heat storage period;
Taking the mine water body in the shaft 1 and the stratum around the shaft 1 as a combined heat storage body, considering that the heat storage capacity of the heat storage mine water volume and the surrounding rock soil is related to the heat of a heat storage heat source, the heat load of a winter heating building and the heat loss of a heat storage system, and determining the mine water heat storage volume of the shaft 1 by adopting the following method: assuming that the heat load Q load required by the heating area of the heating building in winter is provided by the total solar heat collection quantity Q c and the heat storage quantity Q s of the mine water heat storage system of the pit shaft 1 to overcome the heat storage loss Q loss, the following are: ；
In the early stage of the solar cross-season underground heat storage system, the solar heat collector transmits heat to water in the mine shaft 1 so that the water temperature is gradually increased; this heat is transferred from the body of water to the formations surrounding the wellbore 1, causing the temperature of the earth in contact with the body of water to rise; warmer rock soil spreads heat further to a wider area;
when entering a heating season, the temperature of the mine water body in the shaft 1 gradually decreases due to continuous heat extraction; at this time, the heat transferred from the solar collector to the surrounding rock stratum is far greater than the heat recovered from the surrounding rock stratum, namely Q loss >0;
Along with the long-term operation of the system, a water body of the shaft 1 and a stratum surrounding rock heat storage layer are formed; in the heating season, if the temperature of the water body of the shaft 1 is reduced due to heat extraction, the surrounding rock stratum releases the stored heat to the water body of the shaft 1, so that the water body temperature of the shaft 1 gradually rises, the surrounding rock stratum plays a role in heat storage, namely, the heat flows out of Q loss <0 of surrounding rock, so that a transition period in which Q loss is towards zero exists, and the heat received by the water body of the shaft 1 and the heat released by the surrounding rock stratum reach dynamic balance; if the heat injection is stopped at this point, the system will maintain this equilibrium, then there are: ；
In the method, in the process of the invention, Is mine water density, kg/m 3; Constant pressure specific heat capacity, unit J/(kg.K); t is the water temperature of the shaft (1); t 0 is the indoor required temperature in winter; q wc is the heat collection quantity at the moment in winter; For the water intake flow at the moment, the unit is m 3/h;
The heat storage volume V of the mine water in the shaft is determined according to the water taking flow and the specified water changing times n at the moment: ；
Step five, establishing a geometric model and a numerical calculation model control equation of a shaft 1 and surrounding stratum according to the selected abandoned coal mine shaft 1, and setting different working condition parameters and combinations, including boundary and initial condition parameters such as the heat storage volume of the mine water of the shaft 1, the positions of a water inlet pipe 6 and a water outlet pipe 7, initial and target temperatures, the permeability coefficient of the abandoned coal mine shaft 1 and the stratum and the like; carrying out a well bore 1 mine water heat storage scheme numerical simulation experiment based on a 3D hydrogeological model by adopting numerical simulation software, analyzing a well bore water heat storage temperature decay change rule, determining an optimal permeability coefficient, a heat storage action radius, heat storage heat cycle characteristics and a parameter combination scheme, and comprehensively analyzing the waste coal mine well bore 1 mine water heat storage availability;
in the heating and heat accumulating process of the fluid in the shaft 1, the convection heat transfer follows mass conservation, momentum conservation and energy conservation equations, and the basic control equation is expressed as follows:
The mass conservation equation is expressed in fluid mechanics as a continuous equation, i.e., the increase in mass per unit time of a fluid microcell is equal to the net mass flowing into the microcell over the same interval, and its differential expression is as follows: ；
In the method, in the process of the invention, Respectively representing velocity components of the fluid micro-mass in the x, y and z directions, and the unit is m/s;
Conservation of momentum, i.e., the rate of change of the momentum of a fluid in a microbody over time, is equal to the sum of various external forces that are exerted on the microbody by the outside world, and for viscous incompressible flows, the momentum equations in the x, y, z directions are also known as follows: ；
In the method, in the process of the invention, Respectively representing the velocity components in the x, y and z axis directions, and the unit is m/s; tangential stress of the surface of the micro-element body is unit pa; The unit mass force in the x, y and z directions is unit m/s 2;
Energy conservation equation: ；
In the method, in the process of the invention, Is thermal diffusivity, unit，Wherein, the method comprises the steps of, wherein,The heat transfer coefficient of the fluid is expressed as the unit w/(m.K); Is a viscous dissipation term; Is a volumetric heat source;
for the surrounding rock of the shaft 1, the surrounding rock is only regarded as solid in preliminary research, and the influence of seepage flow heat exchange of a porous medium on heat accumulation is not considered, wherein an energy conservation equation of the surrounding rock is an unsteady heat conduction differential equation, namely: ；
In the fifth step, the positions of the water inlet pipe 6 and the water outlet pipe 7 are determined by an equal circular ring surface method, and the process is as follows:
as shown in fig. 3, for a shaft 1 with an inner diameter D, a water inlet pipe 6 and a water outlet pipe 7 are positioned on the diameter line of the circular cross section of the same shaft 1, the water inlet pipe 6 and the water outlet pipe 7 are respectively positioned at two sides of the center of the shaft 1, and the pipe distribution position is calculated by adopting the following formula: ；
Wherein i is the serial number of the equal-circle surface, and i=1, 2,3 . . . . . . from the center of the cross section circle of the shaft 1; n is an equal fraction or number of torus, n=1, 2,3.,; the mine water volume stored under each circular ring under the same water storage shaft height is equal.
Wherein i is the serial number of the equal-circle surface, and i=1, 2,3 . . . . . . from the center of the cross section circle of the shaft 1; n is an equal fraction or number of torus, n=1, 2,3.,; the mine water volume stored under each circular ring under the same water storage shaft height is equal.
As shown in fig. 4, in the embodiment of the present invention, n=1, that is, only 1 ring exists in the cross-sectional circle of the well bore 1, and simultaneously, the cross-sectional circle of the well bore corresponds to only two water pipes of the water inlet pipe 6 and the water outlet pipe 7, and when i=1, the positions thereof are positioned。
In the fifth step, the 3D numerical simulation geometric model is selected from two types, namely, an irregular geometric model including a well bore and a whole mine, and a regular geometric model including a cylinder/cube/cuboid of the well bore and a nearby stratum.
In the fifth step, the 3D numerical simulation geometric model may select a large-scale irregular geometric shape of the whole mine range, firstly, drawing a curve of the whole mine range according to a geological topography of the mine by using skchup software, then, importing SolidWorks software to draw a two-dimensional plane diagram of the mine as shown in fig. 5, creating a 3D stratum diagram of the whole mine as shown in fig. 6 by multi-layer multi-stretching, finally, dividing a grid diagram as shown in fig. 7, and performing numerical simulation calculation.
In another preferred embodiment, in the fifth step, the 3D numerical simulation geometric model may select a regular geometric shape of a small-scale square column of the stratum around the wellbore as shown in fig. 8, and the numerical simulation calculation is performed directly by dividing the network according to stratum data.
Examples: and establishing main components and connection modes of the device according to corresponding geological conditions and mine exploitation conditions. Taking a Xuzhou abandoned mine as an example, the diameter of the mine is 5.2m, the depth of the mine is 230m, and the thickness of the concrete well wall of the well bore is 350mm.
Xuzhou is located in the North-Suzhou region of China, and solar radiation can generate a large amount of heat energy during the summer from 5 months to 9 months old due to the high sunlight intensity. The building may use the coal mine water which has been shut down nearby as a water source, which is relatively stable in both temperature and water content. Mine water stored in the shaft 1 can be heated by combining a solar collector, low-grade industrial waste heat, a photovoltaic panel on the ground, wind energy, and heat removal from a data center. Over time, the heat in the wellbore 1 will transfer to the surrounding aquifer and other strata, so that the water and rock together act as a heat storage medium to store the heat;
In the transition season from 9 months to 11 months, the climate becomes gradually cool, the heat energy requirement of the building is relatively low, and a low-power operation system can be adopted or intermittent heat filling can be stopped. It may be considered to reduce the power of the heating system or to choose to stop heating completely during certain periods of the day to save energy. Heating intensity can be automatically adjusted according to indoor and outdoor temperature difference and expected thermal comfort, or heating is stopped at night and off-peak time periods, so that energy use efficiency is optimized;
During winter heating from the end of 11 months to the beginning of 3 months, the heat of the water in the shaft 1 is mainly used for circulating heating. In this process, two different cases need to be considered: 1. for medium-low temperature water of 30-40 ℃ recharged in summer, the stable temperature heat storage characteristics of the underground shaft 1 and surrounding rocks are utilized, and even if the transition season passes, the average temperature of the water can be kept above 20 ℃. The coefficient of performance COP of the mine water source heat pump is higher than that of the air source heat pump, and the temperature of hot water supply is higher, so that the mine water source heat pump is a heat source with higher efficiency; 2. when the temperature of the water stored in the shaft 1 is lower than the temperature of surrounding rocks after a period of time, the rocks release the heat stored in the rocks to the water body in the shaft 1, so that the heat storage function of the rock body is fully utilized. In this case, the geothermal energy is mainly indirectly used as a heat source of the heat pump. And for stored high-temperature hot water of 50 to 60 ℃, if the water temperature can be maintained at 40 to 50 ℃ after heat storage for several months, namely, the temperature failure is less than 10 ℃, the water supply temperature requirement of the low-temperature hot water ground radiation heating system is met.
In the embodiment, a flat plate type heat collector is adopted, sensible heat is adopted to store heat, water in a shaft 1 and surrounding rock on the outer wall are used as combined heat storage bodies, and the fluid-solid coupling heat storage-release characteristics are studied. The heat storage capacity of the volume of the heat storage water tank and surrounding rock soil is considered to be related to the heat collection capacity of the solar heat collector, the building heat load and the heat loss of the heat storage system. The design presumes that the heat load Q load required by the building heat supply area is provided by the total solar heat collection quantity Q c and the heat storage quantity Q s of the shaft mine water heat storage system by overcoming the heat storage loss Q loss, and then the heat storage system comprises the following components:;
in the early stage of the solar cross-season underground heat storage system, particularly in non-heating seasons, the solar heat collector continuously transmits heat to the mine water body in the shaft 1, so that the water temperature is gradually increased. This heat is gradually transferred from the body of water to the formation surrounding the wellbore 1, causing the temperature of the rock and earth in contact with the body of water to rise slightly. As this process continues, the warmer rock soil spreads the heat further to a wider area. However, when the heating season is entered, the temperature of the body of water gradually decreases due to the continuous heat extraction. At this time, the heat transferred from the solar collector to the surrounding rock is far greater than the heat recovered from the surrounding rock, i.e. Q loss is greater than zero. Along with the long-term operation of the system, a stable well bore 1 water body with higher temperature and a stratum surrounding rock heat storage layer are formed. In the heating season, if the temperature of the water body is reduced due to heat extraction, the surrounding rock releases the stored heat to the water body, so that the temperature of the water body is gradually raised. During this period, the surrounding rock has a heat storage effect, i.e. the Q loss of heat flowing out of the surrounding rock is less than zero. Therefore, a transition period exists when the Q loss is towards zero, and the heat received by the water body and the heat released by the surrounding rock are in dynamic balance. If the heat injection has been stopped at this point, the system will maintain this equilibrium state. Then there are: ;
Wherein T is the temperature of the water body of the shaft; t 0 is the indoor required temperature in winter; q wc is the heat collection quantity at the moment in winter; For the water intake flow at the moment, the unit is m 3/h; the heat storage volume V of the shaft mine water is determined according to the water intake flow and the specified water change times n at the moment: ;
After calculating the time-by-time heat load and the effective heat collection amount of the buildings around the mining area, the volume of the proper heat storage water body can be determined. Through calculation, in the embodiment, the heat storage volume of the mine water of the shaft 1 with the height of 110m and the water storage volume of 2336m 3 can be established by verification calculation;
And adopting simulation software, such as COMSOL Multiphysics 6.0.0, to carry out numerical modeling on the flowing heat transfer of the shaft 1 and surrounding rock in the heat storage process of the underground reservoir reconstructed by the waste mine shaft 1, and taking the numerical modeling as the basis of the subsequent multi-working-condition numerical simulation research.
Three layers of geological layers around the shaft 1 are arranged, the length and the width are 100m, and the depth is 200 m. The SolidWorks was used to build a geometric model of the reservoir of wellbore 1. Setting 0-30m underground as waterproof clay waterproof layer; the middle is a fine sandstone confined aquifer with the thickness of about 58.5m, and contains groundwater; the lower layer rock Dan Hou 41.5.5 m is a dark gray silty mud rock water-resisting layer, has a blocky mud structure and is poor in water permeability. In this embodiment, it may be assumed that the surface of the stratum is flat, and a three-dimensional unsteady wellbore 1 water and heat storage model is constructed. The model mainly focuses on the heat storage area of the shaft 1, is positioned in the ground for 20m to 130m, and calculates the transition season after the heat injection is finished, and the duration is four months. The calculated range of the rock formations is determined based on the effective thermal radius of the subsurface thermal reservoir. Unstructured grids are employed and can be controlled by the user to ensure grid partitioning is close to the actual physical scene. At the stratum interface, the water pipe inlet and outlet, the water pool interface and the contact surface of the fluid and the wall of the shaft 1, the grid is required to be locally thinned so as to improve the calculation accuracy. For other rock areas that do not greatly affect the results of the calculation, a more sparse grid may be used. Because the wall of the shaft 1 and the heat preservation layer are relatively thin, a thin layer structure is arranged in the COMSOL through the linkage of multiple layers of materials, so that the accuracy of numerical simulation can be ensured, and the requirement on computing resources and the simulation time can be reduced.
In the preliminary simulation, the injection period is ignored, the heating is assumed to be stopped in the initial heat storage stage of the heat collector, namely, the heat dissipation of the well bore 1 to surrounding rocks is assumed to be carried out by taking hot water filled in the well bore 1 as a heat source, and the heat storage action radius of the well bore 1 in different stratum is studied. Because the system is an unsteady heat transfer process, in order to obtain an ideal numerical simulation result, after a geometric model, grid division and basic control equation determination are established, reasonable initial and boundary conditions are determined first. The boundary conditions for the simulation set are as follows:
(1) Because the axial both ends area of pit shaft 1 is far less than pit shaft 1 lateral wall area, set up pit shaft 1 and the top and the bottom both ends of country rock and be the adiabatic face, namely: ;
(2) Because the heat diffusion rate to the surrounding rock is slower in the heat accumulation process of the water body of the shaft 1, the far end of the surrounding rock is set to be in a constant temperature condition, so that certain temperature distribution is maintained, and the heat is not affected by heat transfer. Generally, 20-30 m below the ground is a constant temperature zone of a rock stratum, and the deeper the rock stratum below the constant temperature zone is, the higher the temperature is, and the climate change on the ground hardly affects the underground. For Xuzhou region, the temperature of the constant temperature zone can be 16.8 ℃, the average ground temperature gradient below the constant temperature zone is 2.3K/hm, so that the temperature of the far end of the surrounding rock at the bottom z= -130m is 19.1 ℃, and the expression of the far end temperature of the surrounding rock at the height z is set as follows by a custom function UDF: ;
for the heat filling period, setting a water filling port as a speed inlet, and setting a parameter V i for the speed; the conjugate heat transfer sets inflow and outflow boundary conditions respectively; during actual operation, determining the upstream temperature according to the heat collection system, and writing UDF as a boundary condition to realize the joint operation of the heat collection system and the heat storage system; the drain port was a pressure outlet, and the relative pressure was set to 0 Pa.
After the simulation stops heating, the initial value is set as follows: When the temperature of the upper stratum is 16.8 ℃, the temperature gradient of the middle stratum and the lower stratum is 0.023K/m; the water storage section of the shaft 1 is filled with water with the temperature of 50 ℃; the working pressure is 101325Pa, and the speed is 0; acceleration of gravity of The direction is along the negative direction of the Z axis.
For the heat filling process of the shaft 1 in the sunlight intensity sufficient period, the water inlet pipe 6 injects water to the bottom of the shaft 1, and the cold water in the shaft 1 is continuously heated after being mixed with the injected hot water, so that the heat filling process is a mixed convection process in which forced convection and natural convection coexist and mainly adopts natural convection; the heat accumulation process after the heat injection period is finished is a natural convection heat dissipation process between the heat accumulation process and surrounding rock, so that non-isothermal flow multi-physical field coupling is adopted. To more accurately simulate thermal stratification, assuming an incompressible laminar flow of water within the wellbore 1, a Boussinesq approximation may be used with less variation in fluid density due to temperature differences. At this point, the density in the momentum equation is a function of temperature, i.e.In place of the equationWhereinIn order to provide a coefficient of thermal expansion,The water density is used, while the density in other equations is regarded as a constant, and the qualitative temperature is taken as the arithmetic average temperature of the hot water and the initial temperature of the surrounding rock. For natural convection simulation of incompressible flow in COMSOL, boussinesq approximation can be achieved by setting gravity and using reduced pressure. The thermophysical properties of the surrounding rock are as follows:
In the numerical model calculation process, the grid quality has great influence on the accuracy and reliability of the simulation result. In general, the smaller the grid cell size, the more cells, the more accurate the result of the calculation. However, the grid number is too dense, the higher the requirement on the performance of the computer is, the calculation amount of the computer is increased, and the calculation period is prolonged; meanwhile, for COMSOL finite element analysis software, the denser the grid is not, the better the convergence is. However, if the grid quality is too sparse, the calculation amount is reduced, but the calculation result deviates from the actual result, and the error is too large. Therefore, in order to reduce the influence of the grid number on the calculation result as much as possible, in the simulation calculation, grid independence verification is often performed to find a suitable grid number.
And (5) carrying out grid independence verification on the numerical model. In the case where the mesh unit numbers are 98082, 176245, 255094 and 348632, respectively, the temperatures of the internal measurement point 1 (x=0 m, y=0 m, z= -20 m), the measurement point 2 (x=2.8m, y=0 m, z= -75 m) and the measurement point 3 (x=5 m, y=0 m, z= -20 m) in the surrounding rock at the time of heat dissipation 720h in the wellbore 1 water storage section in the model are monitored, and the calculation results are compared as shown in table 2:
From this, it can be seen that when the number of grids is from 98082 to 176245, the maximum temperature change rate in the three measurement points is 1.93%; when the grid number is 176245 to 255094, the maximum temperature change rate in the three measuring points is 0.56%; when the number of grids is 255094 to 348632, the maximum temperature change rate in the three measuring points is only 0.14%, and when more grids need longer calculation time and more calculation memory, the calculation grids with the number of 255094 are suitable for saving calculation resources and simultaneously ensuring simulation accuracy. The mesh subdivision is shown in fig. 8.
Taking the wall rock with the length and width of 100m and the height of 110m, wherein the temperature distribution of xoz axial and xoy radial sections of the stored hot water after four months is shown in figures 9 and 10, and the temperature distribution cloud charts of the water sections at the top and bottom of the shaft 1 are shown in figures 11 and 12 respectively.
As can be seen from fig. 9 to 12: the temperature distribution after four months is in a shape of diverging from the center to the periphery, the central temperature of the shaft 1 reaches the maximum value, and gradually decreases from the wall surface of the shaft 1 to the periphery of the surrounding rock until the temperature is equal to the normal rock temperature; because of density difference caused by different temperatures, the water body in the shaft 1 shows obvious temperature layering, and the average temperature of the top surface is 310.69K and the average temperature of the bottom surface is 305.81K after post-treatment calculation; the upper layer surrounding rock and the lower layer surrounding rock have different thermal action radius (the distance from the point with minimum temperature difference between the infinite end of the surrounding rock and zero to the central axis of the shaft 1) subjected to heat accumulation due to different physical properties such as thermal diffusivity, the average thermal action radius is 16-18m, and the diameter of the temperature wave is about 1/3 of the side length of the surrounding rock. Therefore, in order to improve efficiency in subsequent researches, the peripheral rock diameter can be taken as 60m as a calculation area for heat accumulation calculation in the heat injection period of the shaft 1 under the condition of not affecting the accuracy of results.
The simulation result can provide guidance for implementation of the mine water heat storage system based on reconstruction and reconstruction of the abandoned coal mine shaft.
Claims (5)
1. The mine water heat storage device based on reconstruction and reconstruction of the abandoned coal mine shaft comprises the abandoned coal mine shaft (1) and is characterized in that a sealing section (3) is arranged at the communication part of the bottom of the abandoned coal mine shaft (1) and a horizontal roadway (2), a sealing section (4) is arranged at the top of the abandoned coal mine shaft, and the shaft (1) between the sealing section (3) and the sealing section (4) is a water storage heat storage section (5); two through holes for burying a water inlet pipe (6) and a water outlet pipe (7) are formed in the sealing section (4) along the radial direction of the sealing section, the lower end of the water inlet pipe (6) extends into the position, close to the bottom, of the water storage and heat storage section (5), and the lower end of the water outlet pipe (7) extends into the position, close to the top, of the water storage and heat storage section (5); the upper ends of the water inlet pipe (6) and the water outlet pipe (7) extend out of the top of the sealing section (4); the water inlet pipe (6) and the water outlet pipe (7) are symmetrical about the central axis of the waste coal mine shaft (1), and the distances between the water inlet pipe (6) and the water outlet pipe (7) and the central axis of the waste coal mine shaft (1) are respectivelyD, D is the inner diameter of the shaft (1); the water inlet pipe (6) extends into the water storage and heat storage section (5) at a position which is far from the H/4 position of the top of the sealing and filling section (3), and H is the height of the water storage and heat storage section (5); the water outlet pipe (7) extends into the water storage and heat storage section (5) at a position which is away from the bottom H/4 of the closed section; the lower end of the water inlet pipe (6) is communicated with a horizontal pipeline (8) extending to the central shaft of the shaft (1).
2. The mine water heat storage device based on reconstruction and reconstruction of abandoned coal mine shafts according to claim 1, wherein the shafts (1) of the water storage and heat storage section (5) are reinforced by grouting after wall and low-heat-conductivity nano materials are added into grouting liquid (9); the sealing section (4) is a sealing well cover, the diameter of the sealing section is at least 2m larger than that of the shaft (1), and the thickness of the sealing section is larger than 1m.
3. A method of storing heat using the mine water heat storage device based on reconstruction of abandoned coal mine shaft of any one of claims 1 to 2, comprising the steps of:
Step one, carrying out production and pit closing parameter investigation of abandoned coal mine shafts (1), wherein the investigation comprises main production technical data graphs of mines, position coordinates of the mines, types of the mines, materials of well pipes of the mines, diameters of the mines, depths of the mines, structure diagrams of the mines, stratum profile diagrams of the mines, hydrogeological data of the stratum of the mines, pit closing construction design and completion report;
Step two, evaluating the integrity of the abandoned coal mine shaft (1), wherein the step two comprises unsealing a central drilling hole of a shaft sealing section (4), sampling well wall concrete, sampling well water of the shaft, monitoring the water level of the well water of the shaft, peeping the well wall integrity and the connectivity of a roadway under water, and resealing the central drilling hole of the shaft sealing section (4); carrying out water temperature and salt depth profile monitoring of a shaft and a mine according to field conditions to finish evaluation analysis report of the integrity and availability of the abandoned coal mine shaft (1);
thirdly, for the available abandoned coal mine shaft (1) determined in the second step, installing a mining submersible pump through a central drilling hole of a shaft sealing section (4), carrying out a single-hole large-flow steady flow pumping test in the large-diameter shaft (1), obtaining a flow-time and water level deep-time curve, and iteratively calculating shaft stratum hydrogeological parameters of the abandoned coal mine shaft (1) with the influence radius R and the permeability coefficient K through the following standard formula:
；
Wherein q is pumping flow, and the unit is m 3/s; s is the descending depth, unit m; r is the radius of the shaft, unit m; m is well depth, unit M;
Step four, according to the water pumping test result of the shaft (1), if K ' is less than or equal to K ', wherein K ' is the stratum permeability coefficient of the shaft (1) in the production period, the fact that the mine water of the abandoned coal mine shaft (1) has a water seal-like effect is considered, and the influence of seepage of the mine water through the wall of the shaft (1) on the heat storage performance is ignored;
If the obtained K is more than K', the situation that the wall of the waste coal mine shaft is broken and deformed is considered, seepage and migration of shaft mine water and surrounding stratum groundwater are obvious, and the heat storage effect of the shaft mine water is affected; adopting measures of underwater concrete injection and grouting sealing and reinforcing of the well wall after the well wall damage point by combining the waste coal mine well wall integrity detection peeping result; continuously carrying out measure effect test, carrying out secondary water pumping test, if K > K' still exists, continuously carrying out reconstruction of the wall of the waste coal mine shaft (1), prefabricating the complete wall in sections, reconstructing the complete wall by a sunk well method to form an inner wall which is smaller than the original waste shaft but coaxial, keeping the thickness of the reconstructed inner wall to be the same as that of the original wall, and forming a new water storage and heat storage section (5) for storing mine water by the inner wall; determining the heat storage volume of the mine water of the shaft according to the reconstructed shaft parameters, the ground heat supply load and the heat loss in the heat storage period;
Taking a mine water body in a shaft (1) and stratum around the shaft as a combined heat storage body, and determining the heat storage volume of the mine water in the shaft (1) by adopting the following method: assuming that the heat load Q load, required for heating a building heating area in winter is provided by industrial waste heat such as solar heat collection quantity Q c and heat storage quantity Q s of a shaft mine water heat storage system overcoming heat storage loss Q loss, there are: ；
In the early stage of the solar cross-season underground heat storage system, the solar heat collector transmits heat to water bodies in a mine shaft (1) so that the water temperature is gradually increased; this heat is transferred from the body of water to the formations surrounding the wellbore (1) causing the temperature of the earth in contact with the body of water to rise; warmer rock soil spreads heat further to a wider area;
When the heating season is entered, the temperature of the mine water body in the shaft (1) gradually decreases due to continuous heat extraction; at this time, the heat transferred from the solar collector to the surrounding rock stratum is far greater than the heat recovered from the surrounding rock stratum, namely Q loss >0;
Along with the long-term operation of the system, a water body of a shaft (1) and a stratum surrounding rock heat storage layer are formed; in heating season, if the water temperature of the shaft (1) is reduced due to heat extraction, the surrounding rock stratum releases the stored heat to the water of the shaft (1) so that the water temperature of the shaft (1) is gradually raised, the surrounding rock stratum plays a role in heat storage, namely, the heat flows out of the surrounding rock, Q loss is less than 0, so that a transition period of Q loss approaching zero exists, and the heat received by the water of the shaft (1) and the heat released by the surrounding rock stratum are in dynamic balance; if the heat injection is stopped at this point, the system will maintain this equilibrium, then there are: ；
In the method, in the process of the invention, Is mine water density, kg/m 3; Constant pressure specific heat capacity, unit J/(kg.K); t is the water temperature of the shaft (1); t 0 is the indoor required temperature in winter; q wc is the heat collection quantity at the moment in winter; For the water intake flow at the moment, the unit is m 3/h;
The heat storage volume V of the mine water in the shaft is determined according to the water taking flow and the specified water changing times n at the moment: ；
Step five, according to the selected abandoned coal mine shaft (1), establishing a shaft (1) and surrounding stratum geometric model and numerical calculation model control equation, and setting different working condition parameters and combinations, including the boundary and initial condition parameters such as the heat storage volume of the mine water of the shaft (1), the positions of the water inlet pipe (6) and the water outlet pipe (7), the initial and target temperatures, the abandoned coal mine shaft (1) and the stratum permeability coefficient; carrying out a well bore (1) mine water heat storage scheme numerical simulation experiment based on a 3D hydrogeologic model by adopting numerical simulation software, analyzing a mine water heat storage temperature decay change rule, determining an optimal permeability coefficient, a heat storage action radius, heat storage heat cycle characteristics and a parameter combination scheme, and comprehensively analyzing the mine water heat storage availability of the abandoned coal mine well bore (1);
in the heating and heat accumulating process of fluid in a shaft (1), the heat transfer process follows mass conservation, momentum conservation and energy conservation equations, and the basic control equation is expressed as follows:
The mass conservation equation is expressed in fluid mechanics as a continuous equation, i.e., the increase in mass per unit time of a fluid microcell is equal to the net mass flowing into the microcell over the same interval, and its differential expression is as follows:
；
In the method, in the process of the invention, 、、Respectively representing velocity components of the fluid micro-mass in the x, y and z directions, and the unit is m/s;
Conservation of momentum, i.e., the rate of change of the momentum of a fluid in a microbody over time, is equal to the sum of various external forces that are exerted on the microbody by the outside world, and for viscous incompressible flows, the momentum equations in the x, y, z directions are also known as follows:
；
In the method, in the process of the invention, 、、Respectively representing the velocity components in the x, y and z axis directions, and the unit is m/s; tangential stress of the surface of the micro-element body is unit pa; 、、 The unit mass force in the x, y and z directions is unit m/s 2;
Energy conservation equation: In the method, in the process of the invention, Is thermal diffusivity, unit Wherein, the method comprises the steps of, wherein,The heat transfer coefficient of the fluid is expressed as the unit w/(m.K); Is a viscous dissipation term; Is a volumetric heat source;
For the surrounding rock of the shaft (1), the surrounding rock is only regarded as solid in preliminary research, the influence of seepage flow heat exchange of a porous medium on heat accumulation is not considered, and at the moment, the energy conservation equation of the surrounding rock is an unsteady heat conduction differential equation, namely: 。
4. The method for storing heat of mine water based on reconstruction and reconstruction of abandoned coal mine shafts according to claim 3, wherein in the fifth step, the positions of the water inlet pipe (6) and the water outlet pipe (7) are determined by adopting an equal circular ring method, and the process is as follows:
For a shaft (1) with the inner diameter D, a water inlet pipe (6) and a water outlet pipe (7) are arranged on the diameter line of the circular cross section of the same shaft (1), the water inlet pipe (6) and the water outlet pipe (7) are respectively arranged on two sides of the center of the shaft (1), and the pipe distribution position is calculated by adopting the following formula:
; wherein i is the serial number of an equal-circle surface, and i=1, 2,3 . . . . . . from the center of a cross section circle of the shaft (1); n is an equal fraction or number of torus, n=1, 2,3.,; the mine water volume stored under each circular ring under the same water storage shaft (1) is equal.
5. The method for storing heat in mine water based on reconstruction of abandoned coal mine shaft according to claim 3, wherein in the fifth step, the selection of 3D numerical simulation geometric model is divided into two types of irregular geometric model including shaft and whole mine range and cylinder/cube/cuboid regular geometric model including shaft and nearby stratum.
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| CN113626991A (en) * | 2021-07-20 | 2021-11-09 | 中国矿业大学 | Method for calculating water-heat storage potential of abandoned flooded coal mine |
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| CN216897882U (en) * | 2022-01-28 | 2022-07-05 | 中国地质科学院郑州矿产综合利用研究所 | Geothermal utilization system for underground space of coal mine |
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| CN113626991A (en) * | 2021-07-20 | 2021-11-09 | 中国矿业大学 | Method for calculating water-heat storage potential of abandoned flooded coal mine |
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