Experimental Study On Extraction Of Coal Spontaneous Combustion Heat Energy By Heat Pipe Combined With Thermoelectric Power Generation

The phenomenon of spontaneous combustion in coalfield has been a major disaster problem in the major coal producing countries.If the harmful waste heat produced by coal spontaneous combustion is recycled,it can not only solve the problem of coal spontaneous combustion,but also reuse the heat energy of coal field.Heat pipe heat transfer cooling is a rapid heat transfer process using phase change latent heat.When the heat pipe is inserted into the coal pile,the temperature difference between the internal oxidation high temperature and the external environment is used as the starting heat source of the evaporation end,which is expected to realize the secondary utilization of the heat in combination with the thermoelectric conversion technology.In this paper,a heat pipe is arranged in the coal pile to transfer heat,and combined with the thermoelectric power generation technology,the heat in the coal is directly converted into electric energy under the action of the Seebeck effect.This paper analyzes the heat transfer mechanism between the coal-heat pipe-thermoelectric power generation module by building an experimental platform for coal spontaneous combustion heat energy extraction and thermoelectric conversion,and provides a theoretical basis for the experimental verification of the feasibility of the thermoelectric conversion device.The factors affecting the cooling effect and thermoelectric conversion performance of the experimental system are analyzed and discussed.Through research,it is found that when the filling rate of the heat pipe is 30%,the two-phase heat transfer of the working fluid in the heat pipe reaches the best state,the heat resistance of the heat pipe is the smallest,and the open circuit voltage and short-circuit current of the thermoelectric power generation chip reach the maximum at the corresponding time.The heat pipe arrangement spacing of 15cm can give full play to the cooling and heat conduction performance of the heat pipe,and minimize the average temperature of the coal pile.At the same time,the heat pipe transfers more heat energy in the coal pile to the thermoelectric power generation module,thereby showing better thermoelectric conversion efficiency.The temperature of the heat source that simulates the spontaneous combustion of coal has a great influence on the thermoelectric conversion of the system.The higher the temperature of the heat source,the greater the temperature difference between the hot and cold ends of the thermoelectric generator,the output power will increase accordingly,and the corresponding open circuit voltage and short circuit current will also increase.Under the same temperature gradient,the greater the open circuit voltage,the greater the corresponding short-circuit current.It is found that increasing the number of power generation modules can improve the system power generation performance to a certain extent.However,this method to improve the power generation performance of the system is not sustainable,and there is a dynamic and the thermoelectric conversion performance.The optimal number of series-connected generators for the experimental system set up this time is 6 pieces.There is an optimal matching resistance of 17.3 ? in the system,which can make the load power at both ends of the resistance reach the maximum value.The dimensionless merit value of the thermoelectric power generation sheet has a linear increasing relationship with the temperature difference between its cold and hot ends.Enlarging the temperature gradient of the hot and cold end modules can enable the entire thermoelectric power generation system to exert the best thermoelectric conversion performance.The research of this paper provides a new idea for the treatment of heat damage in coalfield fire zone by means of substitute treatment.