Numerical simulation of the coal temperature field evolution under the liquid nitrogen cold soaking
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ORIGINAL PAPER
Numerical simulation of the coal temperature field evolution under the liquid nitrogen cold soaking Shumin Liu 1 & Xuelong Li 1,2,3,4 & Dengke Wang 2 Received: 7 August 2020 / Accepted: 1 November 2020 # Saudi Society for Geosciences 2020
Abstract Liquid nitrogen fracturing technology is largely based on the characteristics of coal and rock destruction caused by its low temperature to achieve the purpose of increasing permeability. The temperature field study is very important in liquid nitrogen cold soaking. In order to study the spatiotemporal characteristics of the internal temperature field inside coal under the liquid nitrogen cold soaking, the overall heat transfer law of coal is discussed. Based on the theory of heat transfer, this paper discusses the heat transfer equation of coal under the liquid nitrogen cold soaking. A cold shock simulation experiment is performed on the coal specimens during the liquid nitrogen cold soaking by the COMSOL software, and the temperature field change of the coal specimens during the liquid nitrogen cold soaking are obtained. In addition, the simulation results are compared with the experimental results of coal specimens under the liquid nitrogen cold soaking to verify the rationality of the theory and simulation analysis. The results show that the temperature field of coal specimens propagates in the form of waves under the liquid nitrogen cold soaking, which gradually decrease with increasing distance. The closer the dried coal specimens are to the liquid nitrogen boundary surface, the greater the temperature impact speed and the shorter the time required to reach a steady state. Both the surface of the coal specimen and its internal temperature change curve can be divided into three typical phases: the accelerated cooling phase, the decelerated cooling phase, and the low-temperature maintenance phase. The laboratory test results have a good correspondence with the numerical simulation results, which show that it is feasible to use numerical simulation to study the temperature field change law of coal and rock under liquid nitrogen cold soaking. Keywords Coal . Liquid nitrogen cold soaking . Numerical simulation . Temperature field evolution
Introduction The coal industry is the basic industry of China’s national economy, and as an important strategic resource of the country, coal Responsible Editor: Murat Karakus * Xuelong Li [email protected] 1
State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China
2
State Key Laboratory Cultivation Base for Gas Geology and Gas Control, Henan Polytechnic University, Jiaozuo 454150, Henan, China
3
College of Energy and Mining Engineering, Shandong University of Science and Technology, Qingdao 266590, China
4
Mine Disaster Prevention and Control-Ministry of State Key Laboratory Breeding Base, Shandong University of Science and Technology, Qingdao 266590, China
occupies a dominant position in China’s primary energy consumption (Zhang et al. 2014; Kong et al. 20
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