Comparison of Displacement and Mixing Diffusers

In order to cumpare the peformance of different supply diffuers of ventilation air, the airflow passern, temperature stratifiation and contaminant dispersion in a furnitured office ventilated by three kinds of air diffuer were numerically investigated. The air diffuers studied in this paper are a quarter-cylinder displacement diffuer on the floor and mixing diffuers (linear and vortex diffuers) on the ceiling. The heat sources in the of-fice are considered to be 50% convective and 50% radiative. The k-? two-equatwn model of turbulence is employed to predict the turbulent diffusion. The results show that the displacement diffuser provides a rather uniform flow field with low velocify in most areas, and the vertical temperature difference from floor to ceiling is as high as 6 K. With the linear diffuser, the air velociry is high, and the temperature is uniform both horizontally and vertically. The air velocity generated by the vortex diffuser is moderate. The distributions of the temperature and the contaminant are rather uniform.     

Separation-and-Recovery Technology for Organic Waste Liquid with a High Concentration of Inorganic Particles

The environmentally friendly and resourceful utilization of organic waste liquid is one of the frontiers of environmental engineering. With the increasing demand for chemicals, the problem of organic waste liquid with a high concentration of inorganic pollutants in the processing of petroleum, coal, and natural gas is becoming more serious. In this study, the high-speed self-rotation and flipping of particles in a three-dimensional cyclonic turbulent field was examined using a synchronous high-speed camera technique; the self-rotation speed was found to reach 2000–6000 rad·s⁻¹. Based on these findings, a cyclonic gas-stripping method for the removal of organic matter from the pores of particles was invented. A technological process was developed to recover organic matter from waste liquid by cyclonic gas stripping and classifying inorganic particles by means of airflow acceleration classification. A demonstration device was built in Sinopec’s first ebullated-bed hydro-treatment unit for residual oil. Compared with the T-STAR fixed-bed gas-stripping technology designed in the United States, the maximum liquid-removal efficiency of the catalyst particles in this new process is 44.9% greater at the same temperature, and the time required to realize 95% liquid-removal efficiency is decreased from 1956.5 to 8.4 s. In addition, we achieved the classification and reuse of the catalyst particles contained in waste liquid according to their activity. A proposal to use this new technology was put forward regarding the control of organic waste liquid and the classification recovery of inorganic particles in an ebullated-bed hydro-treatment process for residual oil with a processing capacity of 2 × 10⁶ t·a⁻¹. It is estimated that the use of this new technology will lead to the recovery of 3100 t·a⁻¹ of diesel fuel and 647 t·a⁻¹ of high-activity catalyst; in addition, it will reduce the consumption of fresh catalyst by 518 t·a⁻¹. The direct economic benefits of this process will be as high as 37.28 million CNY per year.     

Design Impact on Airflow Patterns in Fluidization Units

The airflow behavior in a fluidization unit was integrally studied by means of experimental work and computational fluid dynamics simulation. The computational domain included the gas inlet pipe, plenum, perforated plate, fluidization chamber, and air outlet pipe. Different scenarios were simulated to allow distinguishing the best way to represent perforated‐plate distributors and elucidate the impact of the grid design on the fluidization performance. The simulated pressure drop across the distributor and the plenum flow pattern were in concordance with the experimental data. It was found that the distance between the peripheral holes and walls has a great impact on the airflow downstream the distributor.     

Experimental and numerical study of the airflow distribution in mixed-flow grain dryers

The aim of this study was to investigate the airflow distribution in a mixed-flow dryer (MFD) and to study the effect of different bed materials and air duct arrangements. The results were used to validate the numerical model developed in a previous work based on Computational Fluid Dynamics (CFD). A series of experiments have been conducted at a semi-technical MFD test dryer with horizontal and diagonal air duct arrangement. Wheat and rapeseed were used as bed materials. The experiments were performed under isothermal conditions. Two experimental methods were selected and adapted to the measuring problem—the measurement of the isobar distribution within the grain bed and the residence time analysis using the tracer gas pulse method. As could be shown, the isobar distributions measured for wheat and rapeseed agreed well with the model predictions. The numerical model could calculate the influence of the bed material with its different particle characteristics (e.g., particle shape, particle size, bed porosity). The results obtained from the residence time analysis confirmed the known quartering of the air stream flowing from one inlet air duct to the four surrounding outlet air ducts for the horizontal air duct arrangement; in the diagonal air duct arrangement, the air stream from one inlet air duct was nearly halved flowing to the two adjacent diagonal outlet air ducts. These results were confirmed by investigations of the air velocity distribution within the grain bulk. Further experiments are necessary to refine the model. The residence time and isobar measurements will be extended to study the influence of different air properties under real drying conditions, the effect of structural elements, and dryer designs.     

激光片光浓度场测量系统及其在风洞模拟中的应用

为在大型环境风洞中模拟大气污染物迁移扩散状况,开发出污染物浓度激光片光测量系统和污染物发放系统。基于激光片光浓度场测量系统,风洞模拟得到城市环境下点、线和面源污染物的扩散分布图案。基于风洞试验工况的边界条件,计算流体动力学(CFD)仿真得到污染物扩散分布,CFD仿真结果和激光片光浓度测量结果,两者定性一致,达到了相互印证的效果。将研究开发的激光片光浓度场测量系统和定量采样方法相结合,有望实现风洞试验中污染物浓度场的定量测试。     

影剧院舞台夏季不同送风方式的模拟及优化

通过运用FLUENT软件模拟夏季影剧院舞台上送上回形式下,三种不同送风方式下的舞台气流组织,通过对温度场、速度场的分布的比较,得出了最优送风方式。     

生物洁净室的污染控制

生物洁净室的目的是控制细菌污染。通过对细菌特性、来源及污染途径的分析,确定了全方位、全过程控制的基本思想,即污染源控制,污染传播过程控制和交叉污染控制,通过分析微粒的运动特性,提出了空气途径污染的主要手段是气流流动控制和表面污染控制,最后分析了交叉污染的形成原因及其防治措施。     

Room Airflow Studies Using Sonic Anemometry

Abstract To ensure prompt response by real-time air monitors to an accidental release of toxic aerosols in a workplace, safety professionals should understand airflow patterns. This understanding can be achieved with validated computational fluid dynamics (CFD) computer simulations, or with experimental techniques, such as measurements with smoke, neutrally buoyant markers, trace gases, or trace aerosol particles. As a supplementary technique to quantify airflows, the use of a state-of-the art, three-dimensional sonic anemometer was explored. This instrument allows for the precise measurements of the air-velocity vector components in the range of a few centimeters per second, which is common in many indoor work environments. Measurements of air velocities and directions at selected locations were made for the purpose of providing data for characterizing fundamental aspects of indoor air movement in two ventilated rooms and for comparison to CFD model predictions. One room was a mockup of a plutonium workroom, and the other was an actual functioning plutonium workroom. In the mockup room, air-velocity vector components were measured at 19 locations at three heights (60, 120 and 180 cm) with average velocities varying from 1.4 cm s^?1 to 9.7 cm s^?1. There were complex flow patterns observed with turbulence intensities from 39% up to 108%. In the plutonium workroom, measurements were made at the breathing-zone height, recording average velocities ranging from 9.9 cm s^?1 to 35.5 cm s^?1 with turbulence intensities from 33% to 108%.     

Scale model study of airflow performance in a ceiling slot-ventilated enclosure: Non-isothermal condition

Scale-model study of a non-isothermal ceiling slot-ventilated enclosure was investigated in both airspeed and thermal fields. Results of airflow pattern, centerline velocity and centerline temperature decay, velocity and temperature profile, airflow boundary layer and thermal boundary layer growth, floor velocity, and floor temperature difference were analyzed to establish semi-empirical prediction equations. Results also compared with previous researches to validate the physical behavior of air-jet. Data of centerline velocity decay showed similar airflow characteristics as isothermal air-jet with Archimedes number (Ar)<0.004$(\mathit{Ar})<0.004$, which performed as pseudo-isothermal airflow. Air-jet fell on entry with Ar>0.018$\mathit{Ar}>0.018$. A single circulation airflow existed at 0.004<Ar<0.011$0.004<\mathit{Ar}<0.011$ and two-circulation airflow occurred at 0.011<Ar<0.018$0.011<\mathit{Ar}<0.018$. The centerline velocity decay was fitted well as similar form of an isothermal condition. The centerline temperature decay was fitted well as the form of centerline velocity decay in both ceiling and floor regions. Both the velocity and temperature profiles agreed with results obtained from literature. Both airflow boundary layer and thermal boundary layer growths increased with traveling distance of air-jet. Maximum floor velocity and floor temperature difference were fitted well with different parameters. Analysis of airflow performance in a non-isothermal condition makes progress in predicting air quality inside the enclosures and guides the design concepts of ventilation system for an indoor environment.