储氢合金罐的传热模拟与优化

发布时间：2018-09-17 16:55

【摘要】：随着世界经济的高速发展,人类对能源的需求日益增加。然而化石燃料日益枯竭,寻找新的替代能源已迫在眉睫。作为最理想的替代品,氢能成为各国学者关注的焦点。而在氢能的应用与推广的过程中,储氢问题是其关键与难题。本文将通过多物理场仿真软件COMSOL,利用合金储氢的偏微分方程组PDEs建立储氢罐一维与二维有限元模型,并进行仿真分析。随后通过对合金储氢放氢过程中的一维模型与二维模型结果对比分析,探讨了维度对收敛性的影响。在文中最后对传热传质基本的PDEs的弱形式进行了简易的推导与验证,并对合金储氢罐内储氢过程中的弱形式进行了探讨。首先,通过对金属储氢基本原理的研究,运用P-C-T曲线对合金储氢过程中氢气的相变过程进行详尽的分析。随后,通过热力学三大定律的基本形式,对合金储氢罐内各部分分别进行分析,给出各自的热力学表达式。进一步地,研究了罐壁与外界换热的换热形式与换热计算方法、罐内换热装置与热源的换热计算方法等。并且对耦合过程进行了描述,为建模打好理论基础。其次,通过对一维与二维小尺度合金储氢罐模型的建立,对一维模型与二维模型的仿真结果进行对比分析。得出在该过程中,温度场、压力场以及达西速度场的模拟结果趋势基本一致,但是其在储氢结束时的状态并不一致。经过分析这可能与建模过程中,一维相对于二维来说,维度的差别会导致信息的损失,造成储氢结束时的状态不同。接着,通过对一维模型与二维模型在仿真过程中迭代过程的分析,并对残差导数的结果进行绘图研究,发现二维模型在计算的过程中残差的导数在短暂收敛后逐渐增大,最终向无穷大趋近;而一维模型则在50s后基本趋于收敛于固定数值。结果表明,一维模型在合金储氢罐的研究中,对参数适应性较好。最后,通过对弱形式的回顾,提出了用弱形式解决合金储氢的方案。随后,对基本传热问题进行弱形式的推导与分析。运用Comsol分别建立PDE方程的模型与弱形式的模型,对比结果,两种模型对比结果具有99%以上的符合度。进一步地,对储氢罐内PDE方程进行弱形式推导,最后得出弱形式的描述。并且将弱形式写成Comsol中的形式,这种理论上的探索对未来模型的完善具有一定的借鉴意义。
[Abstract]:With the rapid development of the world economy, the human demand for energy is increasing day by day. However, fossil fuels are drying up day by day, so it is urgent to find new alternative energy sources. As the ideal substitute, hydrogen energy has become the focus of attention of scholars all over the world. In the process of application and popularization of hydrogen energy, hydrogen storage is the key and difficult problem. In this paper, the one-dimensional and two-dimensional finite element models of hydrogen storage tank are established by using the partial differential equation group (PDEs) of alloy hydrogen storage by the multi-physical field simulation software COMSOL, and the simulation analysis is carried out. Then the effect of dimension on convergence is discussed by comparing the results of one-dimensional model and two-dimensional model in hydrogen storage and desorption process of alloy. In the end, the weak form of heat and mass transfer basic PDEs is deduced and verified, and the weak form of hydrogen storage in alloy hydrogen storage tank is discussed. Firstly, by studying the basic principle of metal hydrogen storage, the phase transition process of hydrogen in the hydrogen storage process of alloy is analyzed in detail by using P-C-T curve. Then, through the basic forms of the three laws of thermodynamics, each part of the alloy hydrogen storage tank is analyzed, and their thermodynamic expressions are given. Furthermore, the heat transfer form and calculation method of the heat transfer between the tank wall and the outside world, the heat transfer calculation method of the heat exchanger and the heat source in the tank are studied. The coupling process is described, which lays a theoretical foundation for modeling. Secondly, through the establishment of one-dimensional and two-dimensional small-scale alloy hydrogen storage tank model, the simulation results of one-dimensional model and two-dimensional model are compared and analyzed. It is concluded that the simulation results of temperature field, pressure field and Darcy velocity field are basically consistent in this process, but their states at the end of hydrogen storage are not consistent. It is possible that the difference between one dimension and two dimensions will lead to the loss of information and result in a different state at the end of hydrogen storage. Then, by analyzing the iterative process of the one-dimensional model and the two-dimensional model in the simulation process, and drawing the results of the residual derivative, it is found that the residual derivative of the two-dimensional model increases gradually after the transient convergence. Finally, it approaches infinity, while the one-dimensional model converges to a fixed value after 50s. The results show that the one-dimensional model has good adaptability to the parameters of hydrogen storage tanks. Finally, by reviewing the weak form, a solution to the hydrogen storage of alloys with weak form is proposed. Then, the weak form of the basic heat transfer problem is deduced and analyzed. The model of PDE equation and the model of weak form are established by Comsol, and the comparison results show that the comparison results of the two models have more than 99% coincidence degree. Furthermore, the PDE equation in hydrogen storage tank is deduced in weak form, and the description of weak form is obtained. And the weak form is written as the form in Comsol, this theoretical exploration has certain reference significance for the perfection of the future model.
【学位授予单位】：武汉理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ116.2;TQ053.2

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