Study On Influence Factors Of Heat Transfer Capacity Of Heat Pipe Used For Coal Storage Pile

Coal spontaneous combustion is one of the most difficult problems in coal storage and transportation and safety management.Coal spontaneous combustion phenomenon often occurs in the places such as coal mine,thermal power plant,port terminal,coal washery,freight station and so on.In addition,the coal production and consumption are large and the distribution of resources in space is uneven,leading to the increase of storage period of coal production and transportation.And these lead to the increase of the risk of spontaneous combustion of coal.The traditional prevention and control methods of coal spontaneous combustion are mostly used after the phenomenon and take a lot manpower and money.The successful application of heat pipe technology in many fields,such as solving the problem of frozen soil in the Qinghai Tibet Plateau,has aroused the attention of scholars in the field of coal spontaneous combustion.Although the basic theory of heat pipe technology is relatively mature,there are still a lot of key scientific problems to be studied in order to apply the heat pipe to the prevention of coal spontaneous combustion.By building a gravity heat pipe heat transfer test bed in coal storage pile,the experimental research on the influence of liquid filling rate and the type of condensation section on the heat transfer efficiency of the gravity heat pipe in the coal storage pile.Using the electric heating plate to heat the coal to simulate the high temperature area of the coal storage pile.When the temperature reaches 50 or 100?,the heating is stopped and the experiments are put out.The starting performance of the gravity heat pipe,the cooling rate of the high temperature area cooling to 50 ?,and the attenuation rate of the cooling rate in the same time period after the temperature of 50 ? are compared and analyzed.The difference of cooling effect of the same gravity heat pipe at different temperature and influence of gravity heat pipe on temperature variation at different horizontal heights are also compared and analyzed.The experimental results show that the cooling effect is better when the liquid filling rate is less(10%)or higher(40%).And the cooling effect of gravity heat pipe which vertical fin with radian is better.The general trend of the change of the cooling rate with the liquid filling rate was analyzed by polynomial fitting.It shows that with the increase of the filling rate,the cooling rate decreases first and then increases.When the coal pile temperature increases,the corresponding liquid filling rate increases with the lowest cooling rate.Based on the analysis of the experimental results,it is found that a large temperature gradient is formed in the coal storage pile due to the fast heating rate.Thus,the heat transfer between the coal bodies is accelerated,and the heat transfer effect of the gravity heat pipe is disturbed.Aiming at this problem,a method of improving the experiment by constant temperature control is put forward.The research in this paper provides a reference for the follow-up study on the application of gravity heat pipe in coal spontaneous combustion prevention and control.