Study Of The Effect Of Moisture And Windward Angle On Heat Removal From Coal Piles By Gravity Heat Pipes

Coal as China’s main energy and chemical industry as the main raw material,in the national economic development has a very important position.However,spontaneous combustion of coal storage piles and gangue hills happens from time to time,which seriously threatens people’s life and property safety.In view of this,this paper uses gravity heat pipe technology to extract the heat inside the coal storage pile in order to prevent the coal pile from spontaneous combustion,and researches the influencing factors of the effect of gravity heat pipe to suppress combustion,the main conclusions are as follows:(1)The effect of air of varying relative humidity on the heat transfer of gravity heat pipes inside a coal storage pile was investigated.The change trend of the high temperature heat source point was analysed.The experimental results show that the change trend of the high temperature heat source point is divided into three phases,a large decrease phase from 0 to 7h,a transition phase from 7 to 20 h,and a stable phase from 20 to 24 h.The magnitude of cooling,cooling rate and the radius of heat transfer by gravity heat pipe were analysed for typical monitoring points at two heat source temperatures with different air humidities.The results show that the cooling rate,the cooling rate and the radius of heat transfer at the typical monitoring points in the range of 50 % to 75 % relative humidity show a trend of increasing and then decreasing,and the gravity heat pipe has the best heat transfer effect on the coal storage pile at 62 % relative humidity.(2)The effect of different coal pile injection volumes on the heat transfer of the gravity heat pipe inside the coal storage pile was investigated.The cooling range and rate of temperature reduction at typical monitoring points and the heat transfer radius of the gravity heat pipe were analysed for different coal pile injection volumes.The results show that the cooling rate,the cooling rate and the heat transfer radius of the typical monitoring points all show a gradually increasing trend in the range of 3～5 L.The best heat transfer effect is achieved when the coal pile is filled with 5 L of water.The radius of heat transfer at a medium temperature heat source with a relative humidity of 62% was also compared with that of the coal pile at 5 L.The results show that the heat transfer radius of the gravity heat pipe at a coal pile injection of 5 L is 4.7 % higher than that at an air relative humidity of 62 %.(3)The effect of the windward angle of the coal pile on the suppression of gravity heat pipes in the high temperature region of the coal storage pile was investigated.The temperature of the coal pile naturally warming up was analysed.The results show that the temperature rises gradually in the windward angle range of 30° to 75°,with the highest temperature at a windward angle of 75°.The effect of different windward angles on the inhibition of temperature rise of the gravity heat pipe in the high temperature region of the coal pile was analysed.The results show that the temperature suppression effect in the windward angle range of 30° to 75° tends to increase and then decrease,and the best temperature suppression effect is achieved at a windward angle of 60°,which is 28.1 % higher than that at a windward angle of 30°.Investigating the optimum air humidity and coal pile water injection for the gravity heat pipe to move heat to the coal storage pile,and the optimum windward angle for the gravity heat pipe to inhibit heating of the coal storage pile provides a new way of thinking to prevent coal spontaneous combustion.