Li Bo, Wei Wen-Na, Wan Qing-Cui, Peng Kang, Chen Ling-Ling
State Key Laboratory of Coal Mine Disaster Dynamics and Control, School of Resources and Safety Engineering, Chongqing University, Chongqing 400044, China.
School of Resources and Safety Engineering, Central South University, Changsha 410083, China.
Entropy (Basel). 2020 Oct 26;22(11):1212. doi: 10.3390/e22111212.
The purpose of this study is to analyze the dynamic properties of gas hydrate development from a large hydrate simulator through numerical simulation. A mathematical model of heat transfer and entropy production of methane hydrate dissociation by depressurization has been established, and the change behaviors of various heat flows and entropy generations have been evaluated. Simulation results show that most of the heat supplied from outside is assimilated by methane hydrate. The energy loss caused by the fluid production is insignificant in comparison to the heat assimilation of the hydrate reservoir. The entropy generation of gas hydrate can be considered as the entropy flow from the ambient environment to the hydrate particles, and it is favorable from the perspective of efficient hydrate exploitation. On the contrary, the undesirable entropy generations of water, gas and quartz sand are induced by the irreversible heat conduction and thermal convection under notable temperature gradient in the deposit. Although lower production pressure will lead to larger entropy production of the whole system, the irreversible energy loss is always extremely limited when compared with the amount of thermal energy utilized by methane hydrate. The production pressure should be set as low as possible for the purpose of enhancing exploitation efficiency, as the entropy production rate is not sensitive to the energy recovery rate under depressurization.
本研究的目的是通过数值模拟分析大型水合物模拟器中天然气水合物开发的动态特性。建立了甲烷水合物降压分解传热及熵产的数学模型，并对各种热流和熵产的变化行为进行了评估。模拟结果表明，外部提供的大部分热量被甲烷水合物吸收。与水合物储层的热吸收相比，流体产出造成的能量损失微不足道。天然气水合物的熵产可视为从周围环境到水合物颗粒的熵流，从高效开采水合物的角度来看是有利的。相反，在沉积物中显著的温度梯度下，不可逆的热传导和热对流会导致水、气和石英砂产生不良的熵产。虽然较低的生产压力会导致整个系统的熵产增加，但与甲烷水合物利用的热能相比，不可逆的能量损失始终极其有限。为了提高开采效率，生产压力应尽可能设置得低，因为在降压条件下熵产率对能量回收率不敏感。
