Numerical simulation of a direct internal reforming solid oxide fuel cell using computational fluid dynamics method

A detailed mathematical model of a direct internal reforming solid oxide fuel cell （DIR-SOFC） incorporating with simulation of chemical and physical processes in the fuel cell is presented. The model is developed based on the reforming and electrochemical reaction mechanisms, mass and energy conservation, and heat transfer. A computational fluid dynamics （CFD） method is used for solving the complicated multiple partial differential equations （PDEs） to obtain the numerical approximations. The resulting distributions of chemical species concentrations, temperature and current density in a cross-flow DIR-SOFC are given and analyzed in detail. Further, the influence between distributions of chemical species concentrations, temperature and current density during the simulation is illustrated and discussed. The heat and mass transfer, and the kinetics of reforming and electrochemical reactions have significant effects on the parameter distributions within the cell. The results show the particular characteristics of the DIR-SOFC among fuel cells, and can aid in stack design and control.     

Numerical Analysis of Influencing Factors on Temperature Field and Airflow Distribution of the Displacement Ventilation System

Indoor air quality and thermal comfort are important features of indoor environment, In this paper, a numerical simulation based on the k-ε model of CFD is used to analyze factors such as loading, exterior-protected construction, blowing-in rate that play an important role in the temperature field and airflow field of the displacement ventilation system. Exterior-protected construction has little influence on indoor temperature distribution of displacement ventilation systems and the influence is limited only in a small area near the external wall when the indoor heat source is the main cooling load. The height of a room has little influence on indoor temperature field, and the temperature gradient of active region is basically unchanged. In the system combined with a displacement ventilation system and a cooling system, the height also has little influence. When the cooling load is high,the indoor heat source creates a strong convective plume, which will make the average indoor air age lower, the ventilation efficiency higher and the elimination of pollutant easier. Air supply rate plays an important role in displacement ventilation systems. The increase of air supply rate that can be realized by increasing the air supply velocity and enlarging the area of air inlet will increase the mass capability of the system and diminish the vertical temperature gradient. From the comparison between simulations and experiments, it is concluded that this simulation are creditable.     

Numerical study on viscosity reduction in mining heavy oil by circulating hot water

Viscosity reduction is an important process in mining heavy oil.To predict the temperature variation and viscosity variation of heavy oil in flow direction,computational fluid dynamics(CFD) was adopted to simulate the process of heat transfer and flow in this paper.Moreover,an objective function,namely viscosity reduction efficiency,was established to analyze the effect of viscosity reduction.The results indicate that circulating hot water can reduce viscosity significantly,and that the effect of viscosity reduction depends on the inlet temperature and inlet volumetric flow rate of hot water.There is a maximum temperature of heavy oil in flow direction.With the inlet volumetric flow rate of 2.0m3/h and the inlet temperatures of 60,℃,70,℃ and 80,℃,viscosity reduction efficiencies are 94.6%,96.7% and 97.3%,respectively.With the inlet temperature of 70,℃ and the volumetric flow rates of 1.5m3 /h,2.0 m3/h and 2.5m3/h,viscosity reduction efficiencies are 94.4%,96.7% and 97.2%,respectively.     

风力机叶片后掠对径向流动的影响

以NREL Phase VI 实验叶片为基础设计了一种后掠型风力机叶片,通过CFD计算模拟,发现后掠叶片的绕流中存在更复杂的径向流动,主要表现在后掠段吸力面流线在前缘附近向叶轮旋转中心偏转,在尾缘附近向叶尖方向明显偏转. 分析得出,叶片后掠改变了入流状态,使得后掠段吸力面流线在前缘附近向叶轮旋转中心偏转;在尾缘附近,其与离心力和科氏力的共同作用使得流动向叶尖发生明显偏转.     

等离子割炬喷嘴热－流耦合分析及优化设计

等离子割炬工作原理复杂,喷嘴在冷却水温度场和流场耦合作用下工作,实物实验难度较大,文章采用CFD软件针对两种割炬喷嘴进行数值模拟,分析在不同冷却水流速度下的温度云图和温度曲线图,确定喷嘴结构,给出建议冷却水流速度。     

车用三元催化转化器流场的数值模拟与结构优化设计

分析了催化转化器内部流场及其结构影响因素,建立了催化转化器内部流场数学模型,应用CFD软件对催化转化器内部流场进行了数值模拟,得到不同结构参数下载体前端面速度和压力分布规律,从而得出比较理想的改进方案。     

Fluent在城市街区大气环境中的一个应用

利用CFD软件Fluent建立了一个三维街道十字路口模型,模拟了 2种风向条件下街区风速分布和CO质量浓度分布的情况.结果表明,十字路口的建筑物布局与风向共同作用,会对街区的风速和CO质量浓度分布产生很大影响.模拟结果表明,CFD对所建模型模拟结果合理,用于街区大气环境问题研究有着良好前景.     

CFD模拟技术在流体力学实验教学改革中的若干探索

实验教学水平的高低是衡量高校综合教学水平的重要组成因素之一。该文在分析流体力学课程现状和实验课程存在的问题的基础上,提出了引入CFD软件进行流体力学实验教学的必要性,CFD模拟技术具有强大的计算能力,将复杂的流体运动以云图的形式展现,将抽象的理论具体化,提高了实验教学的质量和效率,拓展了实践教学环节,提升了学生的科研能力和职业能力。     

Simulation, experimentation, and collaborative analysis of adjacent heat exchange modules in a vehicular cooling system

A cooling system consisting of several heat exchange modules is a necessary part of an automobile, and its performance has a direct effect on a vehicle’s energy consumption. Heat exchangers, such as a charged air cooler (CAC), radiator, oil cooler, or condenser have different structures and can be arranged in various orders, and each combination may produce different effects because of interactions among them. In this study, we aimed to explore the principles governing interactions among adjacent heat exchangers in a cooling system, using numerical simulation and experimental technology. 3D models with different combinations were developed, compared, and analyzed comprehensively. A wind tunnel test platform was constructed to validate the computational results. We found that the heat dissipation of the modules was affected slightly by their relative position (the rules basically comply with the field synergy principle), but was independent of the modules’ spacing within a certain distance range. The heat dissipation of one module could be effectively improved by restructuring, but with a penalty of higher resistance. However, the negative effect on the downstream module was much less than expected. The results indicated that the intensity of heat transfer depends not only on the average temperature difference between cold and hot mediums, but also on the temperature distribution.     

Numerical investigation of the power generation of a ducted composite material marine current turbine

In the hostile and highly corrosive marine environment,advanced composite materials can be used in marine current turbines due to their high strength-to-weight ratios and excellent resistance to corrosion.A composite material marine current turbine(CMMCT),which has significant advantages over traditional designs,has been developed and investigated numerically.A substantial improvement in turbine performance is achieved by placement of a duct to concentrate the energy.Computational fluid dynamics(CFD) results show that the extracted power of a ducted CMMCT can be three to four times the power extracted by a bare turbine of the same turbine area.The results provide an insight into the hydrodynamic design and operation of a CMMCT used to shorten the design period and improve technical performance.