候机厅自然排烟CFD模拟

利用计算流体力学软件PHOENICS对机场候机厅进行自然排烟的计算机模拟。设定火灾场景，给出厅内温度场和烟浓度分布状况，分析了排烟方案的有效性，为设计方案的比较和优化提供一定的依据。     

Sensitivity analysis of CFD coupled non-isothermal heat and moisture modelling

CFD (Computational Fluid Dynamics) is a useful tool to study air flow patterns in a room. Current CFD models are able to simulate air flow combined with temperature distributions and species distributions. In this paper a coupled CFD–HAM model is discussed. This model combines CFD with a HAM model (Heat, Air and Moisture) for hygroscopic materials. This coupled model is able to simulate air flow around a porous material and combines this with heat and moisture transport in the porous material. Validation with a small scale experiment in which gypsum board was used as a hygroscopic material showed good results. In this paper a further validation of the model is discussed based on a sensitivity analysis of some model parameters. Especially hygrothermal parameters like sorption isotherm and water vapour permeability proved to have a non negligible influence on the modelling outcome. Adding a hysteresis model showed improvement of the model during desorption. The model was also used to compare two modelling strategies. In one strategy the gypsum board was modelled as a uniform material, in a second approach the material was modelled as being layered. The difference between the two approaches showed to be negligible.     

An approach to improve the separation of solid-liquid suspensions in inclined plate settlers: CFD simulation and experimental validation

The most important requirements for achieving effective separation conditions in inclined plate settler (IPS) are its hydraulic performance and the equal distribution of suspensions between settler channels, both of which depend on the inlet configuration. In this study, three different inlet structures were used to explore the effect of feeding a bench scale IPS via a nozzle distributor on its hydraulic performance and separation efficiency. Experimental and Computational Fluid Dynamic (CFD) analyses were carried out to evaluate the hydraulic characteristics of the IPS. Comparing the experimental results with the predicted results by CFD simulation implies that the CFD software can play a useful role in studying the hydraulic performance of the IPS by employing residence time distribution (RTD) curves. The results also show that the use of a nozzle distributor can significantly enhance the hydraulic performance of the IPS, which contributes to the improvement of its separation efficiency.     

北京汽车博物馆空调气流组织的CFD模拟研究

针对北京汽车博物馆跨度大、空间高、形状复杂、空调系统设计难度大的特点,采用CFD软件对高大空间的温度场和速度场进行了数值模拟和研究,最终达到调整和优化空调系统设计方案的目的.     

运用CFD模拟工具优化某酒店宴会厅空调设计

通过运用CFD模拟工具,发现某酒店宴会厅原空调设计中存在的问题,从而修改了空调系统和风口布置,成功解决了原方案的不足。工程实际运行后与模拟结果一致,对以后相似的工程设计具有一定的指导意义。     

CFD simulation of anaerobic digester with variable sewage sludge rheology

A computational fluid dynamics (CFD) model that evaluates mechanical mixing in a full-scale anaerobic digester was developed to investigate the influence of sewage sludge rheology on the steady-state digester performance. Mechanical mixing is provided through an impeller located in a draft tube. Use is made of the Multiple Reference Frame model to incorporate the rotating impeller. The non-Newtonian sludge is modeled using the Hershel–Bulkley law because of the yield stress present in the fluid. Water is also used as modeling fluid to illustrate the significant non-Newtonian effects of sewage sludge on mixing patterns. The variation of the sewage sludge rheology as a result of the digestion process is considered to determine its influence on both the required impeller torque and digester mixing patterns. It was found that when modeling the fluid with the Hershel–Bulkley law, the high slope of the sewage stress-strain curve at high shear rates causes significant viscous torque on the impeller surface. Although the overall fluid shear stress property is reduced during digestion, this slope is increased with sludge age, causing an increase in impeller torque for digested sludge due to the high strain rates caused by the pumping impeller. Consideration should be given to using the Bingham law to deal with high strain rates. The overall mixing flow patterns of the digested sludge do however improve slightly.     

CFD simulation of VOCs concentrations in a resident building with new carpet under different ventilation strategies

This paper investigates the effect of ventilation strategies on the concentrations of volatile organic compounds (VOCs) emitted from a new carpet in an apartment with the VOCs emission characteristics taken from chamber test data. The commercial software FLUENT 6 has been employed to solve the continuity, momentum, turbulence and concentration equations under five different ventilation strategies. Numerical results show that ventilation strategies have a small effect on VOCs emission from carpet. Continuous ventilation keeps a low level of VOCs concentration in the air. Flushing ventilation has a significant effect on the VOCs concentration in the air. During a period without ventilation, VOCs concentration in the air usually increases to a high level. Thus, the ventilation should be carried out before the arrival of residents to ensure a low level of VOCs concentration. At the startup of ventilation run, the sudden flow strongly promotes the mixing of VOCs, which may lead to local high concentration.     

地铁站台气流状况现场测试及CFD模拟

地铁站台的气流流动属湍流流动,采用CFD对站台通风方式进行模拟时需要确定相关的边界条件和适用的湍流模型。通过对既有地铁站台气流状况的现场测试,获得了有参考价值的数据;建立了CFD模型。CFD模拟结果与测试数据的比较表明,所选的湍流模型能正确模拟复杂的站台气流流动。     

冷辐射吊项＋独立新风窒调系统的CFD模拟研究——新型空调系统在居室中的运用

利用CFD数值模拟的方式分析冷辐射吊项（CRCP）＋独立新风（DOAS）空调系统的热工性能,与传统的全空气系统（VAV）不同的是,这种新型空调系统采用直接辐射和间接对流的方式来消除室内的热负荷,冷辐射吊顶通过直接辐射和间接对流来承担室内的部分显热负荷,独立新风承接室内的全部潜热负荷与部分显热负荷。以上海某居室为例,分析了冷辐射员顶和独立新风空调系统的原理,并建立了居室的物理模型与数学模型,利用CFD软件模拟了居室内的气流组织,分析了速度场与温度场的分布特征,并对室内热舒适性进行了模拟,并采用PMV—PPD指标对室内热舒适性进行了评价。模拟结果显示,这种新型空调系统能提供较好的热舒适环境和较高的空气品质。     

应用CFD方法确定置换通风系统的设计参数

总结了CFD在研究置换通风系统中的进展,根据对简化模型推导,提出了置换通风系统的设计参数,使设计的空调系统既能保证较高的室内空气品质,又能防止出现吹风感、垂直温差过大等现象。     

CFD simulation of mechanical draft tube mixing in anaerobic digester tanks

Computational Fluid Dynamics (CFD) was used to simulate the mixing characteristics of four different circular anaerobic digester tanks (diameters of 13.7, 21.3, 30.5, and 33.5 m) equipped with single and multiple draft impeller tube mixers. Rates of mixing of step and slug injection of tracers were calculated from which digester volume turnover time (DVTT), mixture diffusion time (MDT), and hydraulic retention time (HRT) could be calculated. Washout characteristics were compared to analytic formulae to estimate any presence of partial mixing, dead volume, short-circuiting, or piston flow. CFD satisfactorily predicted performance of both model and full-scale circular tank configurations.     

亚运自行车馆气流组织CFD的分析和探讨

介绍亚运自行车馆的空调方案,高大空间-观众区和赛场的气流组织,在观众区顶侧部和赛场的顶部设了送风,在前四排座位底和最后一排座位平台侧面进行回风,排风设在场馆最顶部,使用了CFD软件对观众区和赛场进行了三维数值模拟,通过分析模拟的结果表明:观众区和赛场气流组织是满足设计要求的,温度、速度、PMV、PPD、空气龄均较为合适...     

基于CFD技术的室外风热环境分析在某大型商业建筑中的应用

商业建筑的室外风、热环境不仅影响室外广场等人行区域的舒适与安全,更是室内空间进行物理环境设计时的外部条件。该文采用CFD数值模拟方法,对重庆市某大型商业综合体的室外风热环境进行了详细的分析与评价,并提出优化设计建议。该文的研究将为改善该项目的建筑风热环境品质提出有效的技术措施,并为类似工程问题提供参考。     

Response surface models for CFD predictions of air diffusion performance index in a displacement ventilated office

Based on the Response Surface Methodology (RSM), the development of first- and second-order models for predicting the Air Diffusion Performance Index (ADPI) in a displacement-ventilated office is presented. By adopting the technique of Computational Fluid Dynamics (CFD), the new ADPI models developed are used to investigate the effect of simultaneous variation of three design variables in a displacement ventilation case, i.e. location of the displacement diffuser (L_dd), supply temperature (T) and exhaust position (L_ex) on the comfort parameter ADPI. The RSM analyses are carried out with the aid of a statistical software package MINITAB. In the current study, the separate effect of individual design variable as well as the second-order interactions between these variables, are investigated. Based on the variance analyses of both the first- and second-order RSM models, the most influential design variable is the supply temperature. In addition, it is found that the interactions of supply temperature with other design variables are insignificant, as deduced from the second-order RSM model. The optimised ADPI value is subsequently obtained from the model equations.     

Investigation of moisture condensation on papermaking plant envelopes in high humidity environment by orthogonal analysis and CFD simulation

The objective of this study is to investigate the problem of moisture condensation on papermaking plant envelopes in high humidity environment. In this study, orthogonal experiment method is combined with CFD simulation to explore how moisture condensation varies with governing factors, such as the thermal parameters of building envelopes, temperature and humidity distributions or ventilation and air distribution. The criteria used by our work to determine whether the condensation will occur on envelopes are to calculate the temperature differences between the inner surface and the air dew point near the envelopes. Specifically, the temperature differences have a linear relationship with the governing parameters, and a first-order linear regression equation is derived, which is validated by data from investigation and measurement. This research provides theoretical support and measurement data for solutions of the envelope condensation problems and anti-condensation design of HVAC systems in papermaking plants.     

Controlled atmosphere pyrolysis apparatus II (CAPA II): A new tool for analysis of pyrolysis of charring and intumescent polymers

A new gasification apparatus has been developed to enable a comprehensive analysis of pyrolysis of charring and intumescent materials. This apparatus provides well defined boundary conditions and highly resolved measurements of mass, temperature and sample profile evolution of a disk-shaped 0.07 m diameter material sample exposed to radiant heat. All measurements are collected simultaneously, in a single experiment, and recorded as a function of time. The oxygen concentration in the pyrolysis zone is controlled and can be reduced below 1 vol% to ensure that the measurements are free of oxidation effects. The radiation from an external conical heater has been carefully characterized to account for changes in the sample surface position, including the surface's angular orientation. Using an empirical expression, the radiation heat flux can be predicted with less than 2% error based on the known surface position and heat flux set point. The NIST Fire Dynamics Simulator (FDS) has been utilized in the direct numerical simulation mode to investigate convective losses from the sample surfaces. The convective heat transfer coefficient computed for the top (radiation exposed) surface has been found to be dependent on the surface position; its space-averaged value has been validated against experimental measurements. The capabilities of the apparatus are demonstrated using poly(vinyl chloride). It is shown that the apparatus provides repeatable data necessary for modeling of transport processes inside pyrolyzing intumescent solids. Non-one-dimensional nature of these processes is discussed.     

温州某工业建筑室外风环境的CFD模拟分析

建筑室内风环境受室外风环境影响很大,尤其是自然通风、建筑防风效果受室外风环境决定性影响。通过采用Fluent对温州某工业建筑的室外风环境进行了模拟计算,对比分析了2个规划方案在冬夏2种工况下的速度场与压力场。在模拟结果分析基础上,提出了建议规划方案。     

基于CFD的复杂形体超高层建筑风流场数值模拟

建立了某拟建复杂形体超高层建筑的全尺度模型,编写了其入口平均风速剖面、湍动能和湍流耗散率的UDF程序,并选取0度、30度和-30度三种来流风向角,考察了这三种典型来流工况下建筑绕流流场.比较分析表明,相对于标准k-ε模型,RNGk-ε模型和Realizablek-ε模型能更好地捕捉该复杂形体超高层建筑的绕流流场分布特征.同时,在钝体迎风面流动分离的拐角处,RNGk-ε模型和Realizablek-ε模型均可以给出其合理的湍动能分布形态;并且,在流动分离的负压区可以给出其具有满意精度的平均风压分布.     

Thermal simulation: Response factor analysis using three-dimensional CFD in the simulation of air conditioning control

The heat generated from an air-conditioning equipment or other thermal loads is distributed throughout a room by a three-dimensional airflow. This three-dimensional airflow creates a three-dimensional heat distribution in a room. To better understand building performance, we must integrate this spatial distribution into building simulations. Thus, three-dimensional computational fluid dynamics (CFD) analysis is necessary in design process because most conventional building energy simulations still employ a temperature that is averaged across the space of a room. However, usually only a few cases of CFD analyses are executable in real design process because of the large computational load they require. This paper presents a new, simplified method to calculate heat transport phenomena in rooms, based on a few cases of CFD analysis, and to integrate data into a nodal analysis. This method can be used to calculate an indoor environment, including the spatial distribution of temperature, with a computational load that is much lighter than it is in a simulation using CFD alone. Furthermore, in terms of precision, it is a far more reliable method than the conventional simulation, which assumes the perfect mixing of heat in a room. In the paper, we apply this method to simulate the control of air conditioning. Ordinarily, the reproduction of the phenomena shown in the calculation examples requires substantial manpower and costly computing resources for experimentation or CFD analysis. With our calculation method, it is possible to reproduce the same calculation results in a very short time with a PC. And we checked the potential to the practical use through a verification calculation with CFD analysis.     

Mixing characterisation of full-scale membrane bioreactors: CFD modelling with experimental validation

Membrane Bioreactors (MBRs) have been successfully used in aerobic biological wastewater treatment to solve the perennial problem of effective solids-liquid separation. The optimisation of MBRs requires knowledge of the membrane fouling, biokinetics and mixing. However, research has mainly concentrated on the fouling and biokinetics (Ng and Kim, 2007). Current methods of design for a desired flow regime within MBRs are largely based on assumptions (e.g. complete mixing of tanks) and empirical techniques (e.g. specific mixing energy). However, it is difficult to predict how sludge rheology and vessel design in full-scale installations affects hydrodynamics, hence overall performance. Computational Fluid Dynamics (CFD) provides a method for prediction of how vessel features and mixing energy usage affect the hydrodynamics. In this study, a CFD model was developed which accounts for aeration, sludge rheology and geometry (i.e. bioreactor and membrane module). This MBR CFD model was then applied to two full-scale MBRs and was successfully validated against experimental results. The effect of sludge settling and rheology was found to have a minimal impact on the bulk mixing (i.e. the residence time distribution).