高汇聚太阳能流下甲烷水蒸气重整制氢的瞬态特性的研究

发布时间：2018-06-24 05:40

本文选题：太阳能 + 多孔介质　；参考：《哈尔滨工业大学》2015年硕士论文

【摘要】：面对传统能源供给短缺、不可再生和容易造成环境污染等弊病,世界各国致力于发展持续、高效、可再生的各类新能源,来解决传统能源开发利用带来的问题。太阳能热化学利用以其新颖、高效等特点成为新能源研究领域的重点。传统的太阳能热化学转化装置由于有效气体产量低、费用高等缺点无法实现推广,而多孔介质太阳能反应器具有质量轻、体表面积大等优点,使得其转化效率较高,以其为载体的太阳能热化学转化装置成为近年来研究的重点,对其进行研究不仅具有重要的理论价值,更具有广泛的工程应用前景。因此,本文对高汇聚太阳能流下多孔介质反应器内甲烷水蒸气重整制氢的热化学反应瞬态响应特性开展了数值研究。本文以表面涂有催化涂层的多孔介质热化学反应器为研究对象,基于多孔介质流动及传热传质模型,将热化学反应机理与“局部非平衡假设”相耦合,建立了高汇聚太阳能流下甲烷水蒸气重整制取氢气的热化学瞬态反应模型。首先,在无热化学反应的条件下,分析多孔介质反应器内混合流体流动及传热过程,重点研究各类关键因素对温度场瞬态响应特性的影响,为后续甲烷水蒸气重整制取氢气的热化学反应研究提供一定依据。然后,分别采用蒙特卡罗热流和高斯热流作为边界热源,选取典型工况,对多孔介质反应器热化学反应的温度场及产物场的瞬态响应特性进行模拟研究。最后,针对边界条件、多孔介质物性和边界辐射热损失,着重研究其在瞬态热化学反应过程中对制氢效率的影响。研究结果表明,多孔介质反应器内各点稳态温度和出口流体温度均随入口混合流体中甲烷相对含量的增加而升高,如甲烷含量升高50%,出口流体温度升高约40K;在孔隙率0.66-0.93范围内,出口流体温度随孔隙率减小而升高,氢气相对产量升高,如孔隙率由0.9降低为0.7时,出口流体温度升高约60K,氢气相对产量升高约8%;出口面氢气产量随固体骨架导热系数的升高而增大,如导热系数增加20%,氢气产量增加约10%;混合流体入口流速降低,出口面氢气相对产量升高,如入口流速减小0.025m/s,氢气相对产量增大约6%;在不考虑边界辐射热损失的条件下,出口面氢气产量较高,但实际工作环境下,由于入口壁面温度较高,辐射热损失对瞬态温度场和产物场的影响较大,应在考虑辐射热损失的前提下,设法降低其影响。
[Abstract]:In the face of the shortage of traditional energy supply, non-renewable and easy to cause environmental pollution, countries all over the world are committed to the development of sustainable, efficient and renewable new energy to solve the problems brought about by the development and utilization of traditional energy. Thermochemical utilization of solar energy has become the focus in the field of new energy for its novel and high efficiency. The traditional solar thermochemical conversion device can not be popularized because of its low effective gas output and high cost, while the porous medium solar reactor has the advantages of light weight and large surface area, which makes its conversion efficiency higher. The solar thermochemical conversion device with solar energy as its carrier has become the focus of research in recent years. Its research not only has important theoretical value, but also has a wide range of engineering application prospects. Therefore, the transient response characteristics of thermal chemical reaction in a porous medium reactor for hydrogen production by steam reforming of methane with high convergent solar energy flow have been studied numerically in this paper. In this paper, a porous medium thermochemical reactor coated with catalytic coating is studied. Based on the porous media flow and heat and mass transfer model, the thermochemical reaction mechanism is coupled with the "local non-equilibrium hypothesis". A thermochemical transient reaction model for hydrogen production by steam reforming of methane with high convergent solar energy was established. Firstly, under the condition of no thermal chemical reaction, the flow and heat transfer process of mixed fluid in porous media reactor is analyzed, and the influence of various key factors on the transient response of temperature field is studied. It provides a basis for the study of the thermal chemical reaction of methane steam reforming to produce hydrogen. Then, Monte Carlo heat flow and Gao Si heat flux were used as boundary heat source, and the transient response characteristics of thermal chemical reaction temperature field and product field in porous media reactor were simulated. Finally, considering the boundary conditions, the physical properties of porous media and the heat loss of the boundary radiation, the effect of the porous media on the efficiency of hydrogen production during the transient thermal chemical reaction is studied. The results show that the steady state temperature and outlet fluid temperature in the porous media reactor increase with the increase of the relative content of methane in the inlet mixed fluid. If the methane content increases by 50, the outlet fluid temperature increases by about 40K, and the porosity ranges from 0.66-0.93. The temperature of outlet fluid increases with the decrease of porosity, and the relative yield of hydrogen increases, such as when the porosity decreases from 0.9 to 0.7, The outlet fluid temperature increases about 60K, and the relative hydrogen production increases by 8. The hydrogen production increases with the increase of the thermal conductivity of solid skeleton, such as the increase of the thermal conductivity by 20, the increase of the hydrogen production by about 10 percent, and the decrease of the flow rate at the inlet of the mixed fluid. The relative production of hydrogen on the outlet surface is increased, if the inlet velocity is decreased by 0.025 m / s, the relative production of hydrogen gas increases by about 6 parts. Without considering the boundary radiation heat loss, the output of hydrogen on the outlet surface is higher, but in the actual working environment, the temperature of the inlet wall is higher. The radiation heat loss has a great influence on the transient temperature field and the product field, so we should try to reduce the effect of radiation heat loss on the premise of considering the radiation heat loss.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ116.2

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