| The heat exchanging and thermal state prediction between the surrounding rock and wind in a high temperature deep mine is a complicated process of heat and mass transferring,which play a crucial role in the study of heat damage in mines.This paper develops a study of heat exchange and numerical simulation method between the surrounding rock and wind flow in a high temperature deep mine.The aim is to carry out in-depth systematic analysis of the above problems through simulation experiments and mathematical analysis which is based on the numerous research results at home and abroad and the combine of the theories of fluid mechanics,thermodynamics and heat transfer.The research results are applied to the prevention and treatment of mine heat hazards and provide theoretical basis and practical means for solving the heat damage problem of high-temperature mines.In the thermal environment of the mine,heat dissipation of the surrounding rock is an important factor that causes the deterioration of the thermal environment of the mine.Heat transferring occurs when there is a temperature difference between the temperature of the original rock and the temperature of the air flowing in the tunnel.The surrounding rock transfers heat to the wall surface through heat conduction,and then passes through the surrounding rock wall surface to the surrounding environment.The temperature of the original rock of the surrounding rock gradually increases with the depth of mining.The quantity of heat emitted by surrounding rock in deep mines is very large and may even be greater than the sum of heat fluxes of other kinds of substances.Therefore,to deal with the heat damage in high-temperature mines,we must first study the heat dissipation of surrounding rock in high-temperature mines.When solving engineering and scientific problems,the commonly used research methods are mostly divided into theoretical analysis,numerical solution and laboratory experiments.With the development of computational science,great progress has been made in the application of mathematical physics methods to solve engineering practice problems.However,due to the complexity of engineering problems,generally only a few simple analytical solutions can be obtained.In order to meet the needs in the actual practice,the computer application of numerical simulation has become an effective means to solve the complex problems in engineering practice.Discrete methods using the regional division theory are becoming powerful tools that can solve the above complex problems and perform large-scale high-energy operations.In this paper,firstly,based on the problems of wind tunnel heat exchanging and thermal state prediction,carried out the selection of numerical simulation method and the analysis of the heat dissipation law of surrounding rock of high temperature mine roadway.According to the law of conservation of energy and Fourier's law,a mathematic model of the temperature field of roadway surrounding rock is established.The finite volume calculation method is used to analyze it discretely and the elimination field method is used to solve the temperature field of the unsteady roadway surrounding rock.The basic idea and basic principle of the finite volume calculation method are described in detail.The concrete solution process of the finite volume calculation method is illustrated by taking the heat conduction problem of the surrounding rock temperature field as an example.A similar simulated experimental model for the heat exchange between surrounding rock and wind in an asymmetric tunnel was established.Experimental results were used to verify the mathematical model of temperature field of surrounding rock in heterogeneous roadway.Through comparative analysis,the results of finite volume method and the results of similar simulation experiments were anastomosis.In a coincidence,the change trend of the spatial-temporal curve of the temperature field of roadway surrounding rock obtained by the two is consistent,which verifies the scientificity and accuracy of the study of heat transfer in the finite volume calculation method.At the same time,the theoretical analysis was carried out and the finite heat volume calculation method was used to solve the unstable heat transfer number between the roadway and the surrounding rock.The calculation result was consistent with the theoretical curve.In addition,using the finite volume calculation method and the similar simulation experiment platform,the distribution law of the temperature field of roadway surrounding rock is obtained,and the variation law of temperature with time at different locations is obtained.After analyzing the temperature at the wall surface of the tunnel,it was found that under the same external conditions,the temperature of somewhere with the higher thermal conductivity coefficient and the higher thermal conductivity coefficient were slightly higher.The calculation process of the unsteady temperature field of roadway surrounding rock is analyzed by example calculations.The variation law of the cooling circle of the roadway surrounding rock temperature field is given by image.The roadway temperature in the unsteady process,Surrounding rock heat dissipation and its changing trend are obtained by using the Newton cooling formula and the calculated wall surface temperature.This shows that the finite volume calculation method proposed in this paper has certain guiding significance for studying the temperature field of surrounding rock,and at the same time lays a foundation for the establishment of the thermal model of the surrounding rock of the coalmine face and the hot air prevention model of the goaf.To study the problem of heat exchanging and thermal state prediction in high temperature coal face,the first step is to study the temperature field around the coal face.According to the heat-dissipation mechanism of surrounding rock in high-temperature coalmine face and the advancement law of coalmine face,there is a great difference between the thermophysical properties of coal and the thermophysical properties of rocks and the differences in the distribution of rocks in the coal strata.Based on the study of the temperature field of the surrounding rock of heterogeneous roadway,the control equation of the temperature field of the surrounding rock of the heterogeneous coalmine face was established.It further expands the application of the finite volume method to simulate and calculate the heat release law of surrounding rock in continuous mining of medium coal working face.By analyzing the internal unit and the boundary element of the control equation,the finite volume calculation method was used to discrete it and the elimination method was used to solve and prepare the corresponding calculation program to solve the temperature field of the surrounding rock of the heterogeneous coalmine face.The boundary conditions of the temperature field of the coal working face were analyzed and determined.Taking the actual engineering geological conditions as an example,the cloud distribution map of the surrounding coalmine face in continuous advancing was calculated.By analyzing and comparing the characteristics of the changes,the effects of propulsion speed and convective heat transfer intensity on the temperature field of the coal working face were obtained.At the same time,the temperature disturbance range of the coal working face under propulsion was analyzed by comparing the surrounding rock temperature field.Finally,the heat dissipation of surrounding rock of coalmine face under various working conditions was obtained by calculating the wall overtemperature and Newton cooling formula.The reason why the longwall coalmine face has the phenomenon of air leakage in the goaf is the effect of the ventilation pressure difference in the coalmine face.With the continuous mining of deeper mines,under the influence of modern coal mining technology,the output of fully mechanized coalmine face continues to increase and the speed of advancement of the working face continues to accelerate and the temperature of the working face rises sharply.Due to the effect of ventilation pressure difference in the coalmine face,more and more fresh air flows into the goaf.The gas entering the goaf area is oxidized at low temperature with the coal left in the goaf area,causing the heat in the goaf area to gradually accumulate and continue to increase.The fluid in hot state continuously flows from the run-off goaf into the area of Mining face,which will inevitably cause a sharp increase in the temperature of the working face,especially at the corner of return wind,restricting the safe and efficient production of mines.The problem that the air leakage at the return side is serious and the temperature at the return wind corner is significantly increased in the fully mechanized coalmine face of coal mines,specific prevention and control measures must be proposed for the heat damage at the return angle of the working face.The coal-oxygen complex effect within the goaf area is a complex multiphysics coupling problem.It involves the study of the diffusion of oxygen,the seepage of gas and the heat exchange between solids and gases.According to the law of conservation of mass and Darcy's law,a seepage model for hot air drainage in goafs was established.According to the theory of heat transferring and the law of conservation of energy,a model of the temperature field of hot air drainage and solid porous media in goaf was established.According to the law of mass conservation and Fick's law,an oxygen diffusion model for hot air extraction in goafs was established.Based on the multi-field coupling of the seepage field,gas and solid porous medium temperature field and oxygen concentration field in the goaf,a hot blast extraction calculation program for the goaf was prepared.Through comparison and analysis,the hot blast extraction scheme in the goaf area was determined.All above laid the foundation for studying the effect of hot blast drainage in the goaf area on the thermal hazard prevention work in the coalmine face.The above research content provides a solid theoretical basis for the thermal status prediction of coalmine face.In the coalmine face,the heat sources of various types interact and interact with each other and it is an organic whole.After fully analyzing the characteristics of heat transfer along the inlet trough and the mining face,based on the principle of energy conservation,a mathematical model for predicting the thermal state of the inlet trough and the mining face was established.The above mathematical model is discretized using the method of finite difference,and based on the hot air extraction and calculation procedures in the goaf area,the program for predicting and calculating the thermal state of the air entry trough and the mining face is compiled.According to the research content of heat dissipation of roadway surrounding rock and heat dissipation of surrounding rock of coalmine face,the unstable heat transfer coefficient of heat exchange between surrounding wind and surrounding air flow in the intake trough and the mining face was calculated.Analyze the object with actual engineering conditions,find out the change rule of the wind temperature and the mutual influence law among various factors,and explain the effect of the hot blast drainage of the goaf on the heat damage control of the coal working face,which provide theoretical support and practical methods to the prevention of heat damage in the mine Engineering practices such as governance and governance.The innovation of the dissertation is mainly reflected in the following aspects:(1)According to the characteristics of coal strata in coal mines,most of strata are distributed in layers and the thermal physical properties of surrounding rocks in each stratum have certain differences.In this paper,the mathematical model of the temperature field of the surrounding rock of heterogeneous roadway is established by using the finite volume calculation method and the temperature field of the surrounding rock of the heterogeneous roadway is solved.Using similar simulation to verify the platform.The heat distribution law of the surrounding rock temperature field of the heterogeneous roadway was obtained.(2)The finite-volume method was used to simulate and calculate the heat-dissipation law of the surrounding rock of the coalmine face.Based on the differences between the thermal physical properties of coal and the thermophysical properties of rock and the differences in the distribution of rocks in each layer of the coal strata,a control equation for the temperature field of the surrounding rock of the heterogeneous coalmine face was established and solved.The main factors influencing the heat dissipation of the surrounding rock of the coalmine face were analyzed.The heat dissipation of the surrounding rock under various conditions and the disturbance range of the temperature during the propulsion were solved.(3)Based on the multi-field coupling of the goaf,the hot blast extraction calculation program for the goaf was compiled and the hot blast extraction program for the goaf was determined through comparative analysis.The effects of several kinds of ventilation resistance on the hot air extraction in the goaf area were analyzed.The theory of thermal state prediction for the intake trough and coalmine face was perfected and the effect of hot air drainage in the mined-out area on the heat damage control of the coalmine face was illustrated by specific examples. |
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