Experimental Research On The Extraction Of Thermal Probe For Thermal Energy From Coal Fire And The Utilization Of Thermoelectric Power Generation

Coal fire has been one of the great disasters facing the world at present.The government of coal fire mainly adopts the conventional methods of "cooling-resisting-inerting" to control the coal combustion,such as water injection,grouting,and other extinguishment materials.The extraction of thermal energy for thermal probe and transfer efficiency of semiconductor thermoelectric generation technology are investigated by theoretical analysis and experimental research,the thermal energy from coal fire is utilized while controling coal fire,which can provide certain economic benefits.Those can provide a theoretical basis for the prevention and control of coal fires and the development of efficient and clean energy utilization.Extraction system of thermal energy from coal fire was built,and nanofluids was selected as working liquid and water as base liquids.Different Concentrations(5%,10%,15%,and 20%)of Nano-CuO Working Fluids are mixed,with the 0%nano-CuO as control group.The thermocouple was used to monitor the temperature variation of coal within 24 hours,and heat transfer capabilities and key parameters of different Concentrations for thermal probe were investigated in different heating source intensity for 100,200,and 300℃.We could find that the best working ratio of heat transfer performance for thermal probe is 5%,5%and 10%corresponding to the heating source temperature of 100,200 and 300℃ respectively.Furthermore,based on its best working ratio,maximum temperature difference of coal pile were 30.4,104.9,and 165.8 ℃,maximum cooling rate of thermal probe were 26.93%,47.65%,and 56.42%,and maximum effective cooling radius of thermal probe were 0.336,0.407,and 0.4565 m respectively.With the increase of time,temperature of condensation section for thermal probe increase.d rapidly in a short time and then decreased slowly,and it gradually decreased towards the cold section.Finally,the working fluids of thermal probe with 5%,5%,and 10%nano-CuO were selected corresponding to the heating source temperatures of 100,200,and 300 ℃,respectively.The thermal probe and semiconductor thermoelectric device were tightly connected to form thermoelectric power generation system,the temperature characteristics and open-circuit voltage of thermoelectric power generation system under different heat dissipation modes was investigated,and the output power and conversion efficiency were explored.We found that the temperature of hot and cold end for thermoelectric power generation system and the open-circuit voltage were steady under the forced convection of air.Under the forced convection of air,when the current increases gradually,the load voltage increases linearly,and output power of thermoelectric power generation system presented the tendency of firstly increasing and secondly decreasing.Furthermore,maximum output powers of thermoelectric power generation system were 0.143,1.908,and 3.136 W corresponding to the heating source temperatures of 100,200,and 300 ℃,respectively,which can realize the effective utilization of thermal energy.