两种标准实验方法测定的气体爆炸极限的比较

比较了国际上普遍采用的两种确定常压室温下气体爆炸极限实验方法(20 L球形实验装置和DIN 51649的实验装置)测得的实验结果.通过对四种碳氢化合物的测试发现,两种方法测得的爆炸上限存在有明显的差异,约为1%(体积比).提出了一个使得两种实验方法测得的爆炸上限非常接近的新判据.     

三套管蓄能型太阳能与空气源热泵集成系统运行特性的实验研究

本文针对三套管蓄能型太阳能与空气源热泵集成系统建立了实验台,通过实验验证了这一新型系统在蓄冷模式下的运行特性。在蓄冷模式下,压缩机的蒸发压力和冷凝压力变化平缓,压缩比在3～3.6之间;系统换热效果良好,运行稳定。另外,实验还验证了三套管蓄能换热器作为蓄能装置的蓄能能力。在实验测得了冷凝热量和压缩机耗功的基础上,通过计算得到了蓄冷量,这一参数值与随后进行的取冷实验的取冷量之间可以满足能量守恒定律。在整个实验过程中,压缩机的COP在2.02～2.79之间,证明了三套管蓄能型太阳能与空气源热泵集成系统在蓄冷模式下可以安全、可靠地运行。     

纳米水离子对细颗粒物的净化效果实验研究

纳米水离子是通过对凝水放电尖端施加高压电释放的复合离子粒子集团,理论上粒径范围几至几十nm。本实验以香烟产生的颗粒物为实验净化对象,进行了自主研制水离子发生装置的颗粒物净化效果实验研究,并与相关技术的离子发生装置进行对比实验,实验讨论了电压对水离子净化效果的影响,为此类净化装置的设计提供了依据。     

纳米水离子发生装置参数优化实验研究

纳米水离子是羟基被水分子包裹的纳米级水离子,具有杀菌、消臭、除尘等作用。本文对原有装置进行了改进并小型化,实验研究了电压、两极间距对细颗粒物净化效果的影响,并与传统负离子的细颗粒物净化能力进行对比分析。结论表明改进后的小型化装置升高电压,减少两极间距均能提高颗粒物净化效果;水离子的净化效果亦优于普通空气负离子。     

多种方法研究二极管的伏安特性曲线

介绍了多种用于测量二极管伏安特性的方法,我们利用四种方法分别测量同一个二极管的电流电压值,并得出实验数据。用实验数据画出对应各个方法测得的二极管的伏安特性曲线,最后通过对四种方法测得的伏安特性曲线图做出相应的分析给出测量最为精准的方法。     

动物暴露实验中控制甲醛和苯浓度稳定的方法

为了研究动物暴露实验中,在相对小的染毒柜内将低浓度的受试气体长时间保持在稳定状态的可行方法,本文以甲醛和苯为代表气体,通过自行设计并定制的染毒柜,分别对静态控制法和动态控制法进行实验研究。实验结果表明,静态控制法装置简单,但染毒柜内的受试气体浓度衰减过快,若用于长期的暴露实验,不具备可行性。动态控制法相比静态控制法在装置上多了一套送排风系统和一个受试气体的发生装置,能够长时间的保持染毒柜内甲醛和苯的浓度的稳定,可用于长期的动物暴露实验。     

基于模型槽实验的位移土压力研究

文章对倾覆模式下挡土墙位移土的压力进行模型槽实验。通过埋置在模型槽内的土压力盒和自制的填土位移测量装置,测得填土的土压力和变形位移,分析出不同荷载下位移土压力的变化关系。     

氯离子非稳态电迁测试方法在碱矿渣混凝土中的适用性及其改进措施

混凝土孔隙液化学组成对氯离子电迁实验影响显著。碱矿渣胶凝体系孔隙液化学组成不同于硅酸盐水泥体系。因此,普遍适用于硅酸盐水泥混凝土的氯离子电迁测试方法是否适用于碱矿渣混凝土尚存疑虑。通过实验探讨了NT BUILD 492氯离子非稳态电迁测试方法在碱矿渣混凝土中的适用性。结果显示,由于孔隙液电导率影响了测试电压和/或测试时长的选择,采用NT BUILD 492不能很好地将不同配比的碱矿渣混凝土氯离子迁移系数区分开。通过采用增大测试电压至60 V,延长测试时长至72 h的改进措施,测得的氯离子迁移系数区分度得到了较大地提高。     

一种新型静电除尘装置设计

本文提出了一种新型的静电除尘装置,在现有静电除尘技术上进行了改进。该装置通过DSP控制系统处理激光PM2.5传感器对PM2.5浓度的检测信号,进而设定不同PM2.5浓度下的目标电压值,并通过电压传感器测定集尘板间的实际电压。通过比较器处理前述的电压差值,并将其输入PI控制器,同时输出控制信号,DSP根据该控制信号调节输出PWM脉冲的占空比,作用给BUCK电路的功率开关来实现电压调节。通过上述方法可以解决现有静电除尘技术存在的问题,以期实现对PM2.5高效低阻且无副产物的净化目的。     

夹层液体循环隔热玻璃实验装置研制及性能测试

研制建筑外墙体新型夹层隔热玻璃实验装置——夹层液体循环隔热玻璃实验系统,通过实验测试得到了明显的隔热性能与蓄能效果,表明了此新型的夹层液体隔热玻璃有节能效果与发展前景,     

Desiccant wheels as gas-phase absorption (GPA) air cleaners: evaluation by PTR-MS and sensory assessment

Two experiments were conducted to investigate the use of the co-sorption effect of a desiccant wheel for improving indoor air quality. One experiment was conducted in a climate chamber to investigate the co-sorption effect of a desiccant wheel on the chemical removal of indoor air pollutants; another experiment was conducted in an office room to investigate the resulting effect on perceived air quality. A dehumidifier with a silica-gel desiccant wheel was installed in the ventilation system of the test chamber and office room to treat the recirculation airflow. Human subjects, flooring materials and four pure chemicals (formaldehyde, ethanol, toluene and 1,2-dichloroethane) were used as air pollution sources. Proton-Transfer-Reaction--Mass Spectrometry (PTR-MS) and sensory subjects were used to characterize the effectiveness of chemical and sensory pollution removal of the desiccant wheel. The experiments revealed that all the measured VOCs were removed effectively by the desiccant wheel with an average efficiency of 94% or higher; more than 80% of the sensory pollution load was removed and the percentage dissatisfied with the air quality decreased from 70% to 20%. These results indicate that incorporating a regenerative desiccant wheel in a ventilation system is an efficient way of removing indoor VOCs. PRACTICAL IMPLICATIONS: This study may lead to the development of new air cleaners and validates a new concept for the design of ventilation systems that can improve indoor air quality and reduce energy consumption.     

脉冲电晕放电法低温等离子体净化室内VOCs

室内挥发性有机物(VOCs)对居民健康有严重危害：用低温等离子体技术降解室内VOCs是空气净化领域近几年兴起的一种的新技术,本文首先简单介绍了VOCs的主要来源和对人体的危害,然后介绍了脉冲电晕放电低温等离子体分解VOCs的原理,提出了两种VOCs分解的模型。依据模型分析了处理过程的影响因素。分析了低温等离子体净化VOCs的现状和存在的问题,指出了以后的发展方向及在实际生活中的应用。最后提出这是一项有广阔应用前景但还待进一步发展完善的技术。     

Modelling of Emission and Re-emission of Volatile Organic Compounds from Building Materials with Indoor Air Applications

Polymer materials and their additives are today ever present in our daily surroundings. These materials have been found to emit a number of different volatile organic compounds (VOCs) into the ambient air, thus affecting the quality of the indoor air VOCs with detectable concentrations are exchanged between the different materials and indoor air. Materials present in the system act as sorbents as well as sources of emission, depending on the concentration of the VOCs in the air at a specific time. This work demonstrates a method of studying the phenomena of absorption/re-emission. A hypothetical room that resembles a furnished office has been studied. A PVC flooring material was used as a primary emission source in a system where materials such as wood, paint, cloth, chipboard, and cellulose were present. Mass transfer in the solid materials was assumed to be by diffusion. The results show that the mechanism of absorption/re-emission of volatiles may extend the time of residence in an indoor system considerably. A person working in this environment could risk longer exposure to toxic volatiles than if there were no absorption/re-emission effects.     

Characterization Of Ofice Dust By VOCs And TVOC Release - Identification Of Potential Irritant VOCs By Partial Least Squares Analysis

Floor dust from nine city hall office buildings was separated into fiber and particulate fractions and analyzed for volatile organic compounds (VOCs) and total VOC (TVOC) by thermal desorption/high resolution gas chromatography (HRGC). Components were identified by HRGC/mass spectroscopy (MS). Principal component analysis was applied to VOC emission profiles revealing similarities between buildings and correlations between profiles and SBS symptoms of mucous membrane irritation and “concentration difficulty”. While the dominant pattern in emission profiles was not correlated with SBS irritation complaints, partial least squares analysis in latent variables (PLS analysis) identified VOCs for which peak areas were correlated with SBS irritation complaints and the CNS Complaint, “concentration difficulty”     

Modeling and physical interpretation of photocatalytic oxidation efficiency in indoor air applications

Volatile organic compounds (VOCs) are the major pollutants in indoor air, which significantly impact indoor air quality (IAQ). As a promising technique to remove VOCs, photocatalytic oxidation (PCO) takes the advantages of oxidation of a large range of VOCs with low energy consumption. In this study, the mass transports and reaction mechanism involved in the PCO process have been studied. In addition, the kinetic models of PCO on the different conditions of elementary reactions have been critically reviewed. Moreover, the factors that may affect the efficiency of PCO were interpreted based on the established fundamental mechanism of PCO. Some recommendations were made for future work to improve the efficiency of PCO system for building applications.     

Are We Measuring the Relevant Indoor Pollutants?

Abstract Concentrations of volatile organic compounds (VOCs) measured indoors may exceed their odor thresholds, but are usually far below TLV estimates. Even applying additivity to eye and airway irritation effects, it is difficult to rationalize increased sick building syndrome (SBS) symptoms by exposure to generally chemically inert VOCs in the indoor environment. Several studies suggest that chemical reactions in indoor air are linked with SBS symptoms and the examination of these reactions may be necessary in order to understand the role of VOCs as causative agents of SBS symptoms. The usual evaluation of odor annoyance of VOCs based on odor thresholds should be modified, taking into account the large variation of individual human odor thresholds for single substances, and specific additivity phenomena even at subthreshold levels of VOCs. The conclusion of this review is that chemical reactions between oxidizable VOCs and oxidants, such as ozone and possibly nitrogen oxides, can form irritants which may be responsible for the reported symptoms. Compounds adsorbed to particles may also contribute to SBS symptoms. The individual effects of indoor pollutants may act in concert with temperature and relative humidity. New analytical methods are required to measure the oxidative and reactive species or specific markers thereof in indoor air.     

固相微萃取法同时分析源水中54种挥发性有机物

建立了同时测定饮用水源水中54种挥发性有机物的前处理方法———顶空固相微萃取法。用65μm聚二甲基硅氧烷二乙烯基苯(PDMS-DVB)固相微萃取柱顶空萃取水样中的挥发性有机物,萃取物用气相色谱/质谱联用法(GC-MS)分析,采用质谱(MS)检测器的选择离子监测模式(SIM)和内标法进行定量分析。试验优化了顶空固相微萃取条件,如萃取柱涂层、盐度、萃取温度和萃取时间等。采用优化后的条件获得的方法检出限为0.01～0.37μg/L,在所测浓度范围内校准曲线的相关系数良好(除三氯甲烷和四氯化碳外均大于0.991),对0.60μg/L标准水样测得结果的RSD均小于15%;实际饮用水源水样加标回收率均值和RSD分别为73.1%～130%和1.4%～19%(n=6)。该方法适用于饮用水源水中挥发性有机物的监测分析。     

Influencing factors of carbonyl compounds and other VOCs in commercial airliner cabins: On-board investigation of 56 flights

Volatile organic compounds (VOCs) as a non-negligible aircraft cabin air quality (CAQ) factor influence the health and comfort of passengers and crew members. On-board measurements of carbonyls (short-chain (C₁-C₆)) and other volatile organic compounds (VOCs, long-chain (C₆-C₁₆)) with a total of 350 samples were conducted in 56 commercial airliner cabins covering 8 aircraft models in this study. The mean concentration for each individual carbonyl compound was between 0.3 and 8.3 μg/m³ (except for acrolein & acetone, average = 20.7 μg/m³) similar to the mean concentrations of other highly detected VOCs (long-chain (C₆-C₁₆), 97% of which ranged in 0–10 μg/m³) in aircraft cabins. Formaldehyde concentrations in flights were significantly lower than in residential buildings, where construction materials are known formaldehyde sources. Acetone is a VOC emitted by humans, and its concentration in flights was similar to that in other high-occupant density transportation vehicles. The variation of VOC concentrations in different flight phases of long-haul flights was the same as that of CO₂ concentration except for the meal phase, which indicates the importance of cabin ventilation in diluting the gaseous contaminants, while the sustained and slow growth of the VOC concentrations during the cruising phase in short-haul flights indicated that the ventilation could not adequately dilute the emission of VOCs. For the different categories of VOCs, the mean concentration during the cruising phase of benzene series, aldehydes, alkanes, other VOCs (detection rate > 50%), and carbonyls in long-haul flights was 44.2 µg/m³, 17.9 µg/m³, 18.6 µg/m³, 31.5 µg/m³, and 20.4 µg/m³ lower than those in short-haul flights, respectively. Carbonyls and d-limonene showed a significant correlation with meal service (p < 0.05). Unlike the newly decorated rooms or new vehicles, the inner materials were not the major emission sources in aircraft cabins. Practical Implications.

• The on-board measurements of 56 flights enrich the VOC database of cabin environment, especially for carbonyls. The literature review of carbonyls in the past 20 years contributes to the understanding the current status of cabin air quality (CAQ).
• The analysis of VOC concentration variation for different flight phases, flight duration, and aircraft age lays a foundation for exploring effective control methods, including ventilation and purification for cabin VOC pollution.
• The enriched VOC data is helpful to explore the key VOCs of aircraft cabin environment and to evaluate the acute/chronic health exposure risk of pollutants for passengers and crew members.

     

Source apportionment of human personal exposure to volatile organic compounds in homes, offices and outdoors by chemical mass balance and genetic algorithm receptor models

A number of past studies have shown the prevalence of a considerable amount of volatile organic compounds (VOCs) in workplace, home and outdoor microenvironments. The quantification of an individual's personal exposure to VOCs in each of these microenvironments is an essential task to recognize the health risks. In this paper, such a study of source apportionment of the human exposure to VOCs in homes, offices, and outdoors has been presented. Air samples, analysed for 25 organic compounds and sampled during one week in homes, offices, outdoors and close to persons, at seven locations in the city of Leipzig, have been utilized to recognize the concentration pattern of VOCs using the chemical mass balance (CMB) receptor model. In result, the largest contribution of VOCs to the personal exposure is from homes in the range of 42 to 73%, followed by outdoors, 18 to 34%, and the offices, 2 to 38% with the corresponding concentration ranges of 35 to 80 microg m(- 3), 10 to 45 microg m(- 3) and 1 to 30 microg m(- 3) respectively. The species such as benzene, dodecane, decane, methyl-cyclopentane, triethyltoluene and trichloroethylene dominate outdoors; methyl-cyclohexane, triethyltoluene, nonane, octane, tetraethyltoluene, undecane are highest in the offices; while, from the terpenoid group like 3-carane, limonene, a-pinene, b-pinene and the aromatics toluene and styrene most influence the homes. A genetic algorithm (GA) model has also been applied to carry out the source apportionment. Its results are comparable with that of CMB.     

Treatment of VOCs in high strength wastes using an anaerobic expanded-bed GAC reactor

The potential of the expanded-bed granular activated carbon (GAC) anaerobic reactor in treating a high strength waste containing RCRA volatile organic compounds (VOCs) was studied. A total of six VOCs, methylene chloride, chlorobenzene, carbon tetrachloride, chloroform, toluene and tetrachloroethylene, were fed to the reactor in a high strength matrix of background solvents. Performance was evaluated. The reactor was found to effect excellent removal of all VOCs (97%). Chloroform, while itself removed at levels in excess of 97%, was found to inhibit the degradation of acetate and acetone, two of the background solvents. Without any source of chloroform in the feed, excellent COD removals were obtained in addition to near-complete removal of all the VOCs.