Optimization of dilution ventilation layout design in confined environments using Computational Fluid Dynamics (CFD)

Dilution ventilation systems have been widely used to control the airborne toxic and explosive material in confined spaces. Layout design of dilution ventilation is critical to industrial hygiene control and ventilation efficiency. A properly designed dilution ventilation system can significantly improve the safety of confined workshops and maintain a comfortable work condition. In this work, Computational Fluid Dynamics (CFD) has been used to analyze the performance of dilution ventilation system in the confined workshop environment. Seven different ventilation layouts are proposed to evaluate ventilation performance of different installation layouts. Carbon monoxide (CO), which has the similar density as air, is selected as the sample contaminant to conduct steady-state CFD simulations. The simulation results of different layouts are examined and compared to get the optimal layout design for the best contaminant control. Results have shown that the layout with two opposite inlets has the highest ventilation efficiency among seven proposed layouts. This work can serve as a reference to increase dilution ventilation efficiency and minimize the energy cost in general confined areas.     

Application of Bayesian Regularization Artificial Neural Network in explosion risk analysis of fixed offshore platform

Computational Fluid Dynamics (CFD) is routinely used in Explosion Risk Analysis (ERA), as CFD-based ERA offers a good understanding of underlying physics accidental loads. Generally, simplifications were incorporated into CFD-based ERA to limit the number of simulations. Frozen Cloud Approach (FCA) is a frequently used simplification in the dispersion part of the CFD-based ERA procedure. However, its accuracy is questionable in the complex and congested environment such as offshore facility. Furthermore, in explosion part, some specific techniques, e.g. linear/double bin-interpolated techniques have been proposed while the corresponding accuracy is still unknown since the developers did not yet check their accuracy by considering the explosion computational data as the benchmark.This study presents a more accurate algorithm, namely Bayesian Regularization Artificial Neural Network (BRANN) and accordingly proposes the frameworks regarding BRANN-based models for the CFD-based ERA procedure. Firstly, the framework is proposed to develop the Transient-BRANN (TBRANN) model for transient dispersion study. In addition, the framework to determine the BRANN model for explosion study is developed. The proposed frameworks are explained by a case study of the fixed offshore platform. Consequently, this study confirms the more accuracy of the TBRANN model over FCA and the accuracy of BRANN model for CFD-based ERA.     

Computational fluid dynamics (CFD) study of heat radiation from large liquefied petroleum gas (LPG) pool fires

Liquefied petroleum gas (LPG) is flammable and has risks of pool fires during its transportation, storage, and applications. The heat radiation by LPG pool fires poses hazards to individuals nearby and can lead to potential failures of ambient facilities. Due to the high costs and invasive nature of experiments for investigating large-scale pool fires, computational fluid dynamics (CFD) is employed in this study as the cost-effective and noninvasive method to simulate the process and analyze the characteristics of large hydrocarbon pool fires. Specifically, an experimentally validated 3-D CFD model has been built to simulate surface emissive power (SEP) and incident radiation of large-scale LPG pool fires with three different diameters and wind speeds. Steady-state simulations with P1 radiation and probability density function (PDF) combustion models were employed to obtain reliable data after the optimizations based on the comparisons with experimental data and empirical models. The comparison with benchmark experimental data demonstrates that the CFD model employed in this study can accurately predict the incident radiation of large LPG pool fires. A new SEP correlation is also proposed, which is specifically for LPG pool fires with a diameter between 10 m and 20 m. Additionally, the safe separation distances between LPG facilities and surrounded objects have been estimated based on the CFD simulation results. The high-resolution CFD model for large LPG pool fires in this work provides noninvasive and direct quantitative evidence to enhance the fundamental understanding on the safety of large LPG pool fires and can assist regulatory agencies in refining the safety limits in the cost-effective and time-saving manners.     

陆上物质的远距离输送对西太平洋热带海域降水化学组成的影响

１９８８年９－１０月在西太平洋热带海域收集了４６个雨水样品和３８８份雨水样品和３８８份雨滴谱。分析结果表明，３个ｐＨ值范围下的平均两滴谱的分布基本上满足指数递减律。在风系作用下，远距离输送来的陆上物质对该海域雨水的平均ｐＨ值为５．７３，而“陆地性”降雨的平均ｐＨ值只有４．８０。ｐＨ５．７３可认为是ＴＷＰＡ上未受陆地源直接影响的天然降雨的平均ｐＨ值。最后还给出了观测期间该海域非海化学组分的湿沉降通量     

库车前陆盆地流体化学、成因与流动

库车前陆盆地寒武系 -第三系流体分析显示 :寒武系 -奥陶系和侏罗系油田水与白垩系 -第三系有所差异 ,前者总矿化度相对较低 ,为 90g/L～ 1 1 0g/L ;相对富Ca2 + 和HCO-3 ;后者总矿化度介于 73g/L～ 3 1 0g/L,主要为 1 3 0g/L～ 2 90g/L,相对富K+ +Na+ 和Cl-;而大宛齐第三系油田水则相对富Ca。影响水化学演化的因素包括 :膏盐类、沸石类矿物溶解以及白云化作用和富镁绿泥石形成等。白垩系油田水δ18O、δD关系显示为淡水蒸发成因 ,且在轮台断隆带油田水87Sr/86Sr向西降低 ,指示了富87Sr的流体来自东部的碎屑泥岩 ,这与本区煤成油运移方向是一致的。而 2个寒武系 -奥陶系油田水87Sr/86Sr高达0 .71 71 6,并富Li、B、Sr元素和δ18O ,被认为来自结晶基岩 ,与氮气、氦气及部分甲烷的来源一致。     

绿色化学—21世纪的化学

绿色化学是从节约资源和防止污染的角度来重新和改革传统化学。文中评述了近年来对原料、化学反应、产品、催化剂和溶剂的绿色化开展的一些主要研究及目前取得的进展。     

绿色化学教育的探讨

当今全球十大环境问题几乎每都直接与化学和化学工业污染污染有关，如何减少化学和化学工业所造成的污染是许多环境保护工作者所研究的重要课题，本文介绍了绿色化学的内涵，提出了实施绿色化学理论教育和绿色化学实验教育的具体措施，绿色化学及绿色化学教育对环境保护具有重大而深远的意义。     

高浓度氨氮废水处理试验

采用二级吹脱加生化的方法处理高浓度氨氮废水，试验在工况I（气、水温均为4℃）和工况Ⅱ（气温4℃，水温28℃,pH=10.5)条件下分别进行静、动态试验，结果表明在工况Ⅱ条件下，氧化铁废水（浓氨水）的静、动态试验怕氮去除率分别为82.67%和84.19%；综合废水的静、动态试验氨氮去除率一级吹脱分别为62.03%和74.16%，二级吹脱后氨氮浓度降至82.16mg/L和74.32mg/L。再接上后续的生化处理，该废水能达到规定的排放标准。     

NO_X大气化学概论及全球NO_X释放源综述

NOX 在全球大气环境、气候变化和地圈N生物地球化学循环中起着极其重要的作用。本文综述了NOX 大气浓度增长对对流层大气O3污染、大气氧化能力和酸沉降及平流层O3消耗的影响 ;同时探讨了全球NOX 释放源组成、年释放总量和人类活动的贡献 ,并与N2 O的源组成进行了对比。     

一个液相化学反应机理的建立和应用

利用比较积分反应速率的方法,建立了一个简化液相化学反应机理ARCML,并在各种大气状况下以及各种物理参数下对ARCML作了验证.然后利用ARCML模拟光化学烟雾形成初期的云水酸化过程,结果表明,自由基氧化s(Ⅳ)在污染或高NO_x的大气中非常重要.