Fabrication of a multi-walled carbon nanotube-deposited glass fiber air filter for the enhancement of nano and submicron aerosol particle filtration and additional antibacterial efficacy

We grew multi-walled carbon nanotubes (MWCNTs) on a glass fiber air filter using thermal chemical vapor deposition (CVD) after the filter was catalytically activated with a spark discharge. After the CNT deposition, filtration and antibacterial tests were performed with the filters. Potassium chloride (KCl) particles (< 1 μm) were used as the test aerosol particles, and their number concentration was measured using a scanning mobility particle sizer. Antibacterial tests were performed using the colony counting method, and Escherichia coli (E. coli) was used as the test bacteria. The results showed that the CNT deposition increased the filtration efficiency of nano and submicron-sized particles, but did not increase the pressure drop across the filter. When a pristine glass fiber filter that had no CNTs was used, the particle filtration efficiencies at particle sizes under 30 nm and near 500 nm were 48.5% and 46.8%, respectively. However, the efficiencies increased to 64.3% and 60.2%, respectively, when the CNT-deposited filter was used. The reduction in the number of viable cells was determined by counting the colony forming units (CFU) of each test filter after contact with the cells. The pristine glass fiber filter was used as a control, and 83.7% of the E. coli were inactivated on the CNT-deposited filter.     

Effect of face velocity and the nature of aerosol on the collection of submicrometer particles by electrostatic precipitator

Despite the electrostatic collection of aerosol particles as one of the most widely used air cleaning methods, there has not been sufficient amount of effort devoted to investigate its performance in the full range of operating conditions. This paper reports results of the tests of a two-stage electrostatic precipitator (ESP) conducted in the particle size range of 0.018-1.2 microns over a range of flow rates using NaCl and Environmental Tobacco Smoke (ETS) test aerosols. The total collection efficiency of the precipitator was found to increase with an increase in the count median diameter (CMD) of the particles, to have polynomial dependence on flow rate and no significant dependence on the type of test aerosol. The fractional efficiency of the precipitator was found to be dependent on flow rate. However, the 'critical' particle size of about 1.2 microns was found to exist when the fractional collection efficiency becomes independent of flow rate. For submicrometer particles, the collection efficiency was found to be independent of particle size at flow rates below 560 l/s. A minimum in the efficiency was observed in the 0.1-0.45 micron particle size range and for particles smaller than about 0.02 micron.     

Improvement of desalination efficiency in capacitive deionization using a carbon electrode coated with an ion-exchange polymer

A composite carbon electrode coated with a cation-exchange polymer, crosslinked poly(vinyl alcohol) with sulfosuccinic acid, was fabricated to enhance the desalination performance of a capacitive deionization (CDI) system. The electrochemical properties of the prepared electrode were characterized by impedance spectroscopy, and desalination experiments were carried out at various operating conditions using a CDI cell with carbon electrodes only, and a membrane-capacitive-deionization (MCDI) cell including a coated-carbon electrode, to evaluate the effect of the coated-carbon electrode on desalination performance. The electrical resistance of the coated electrode was increased by a small amount over the uncoated electrode, but the capacitance was improved by the coating. In the CDI cell, the salt-removal efficiencies were in the range of 50-67%, while the efficiencies increased to 75-85% for the MCDI cell. Depending on the operating conditions, the salt-removal and current efficiencies of the MCDI cell were enhanced by 27-56% and 69-95%, respectively, compared to the CDI cell. The enhanced efficiency for the MCDI cell was attributed to the selective transport of cations between the electrode surface and bulk solution due to the cation-exchange coating layer.     

若干掺合料对减水剂塑化效果的影响

研究了经活化处理并磨细的煤矸石及粉煤灰以不同比例等量替代部分水泥后,对掺减水剂水泥浆体流动度的影响规律,并将其与常用的矿物掺合料进行比较.结果表明,对于所选用的3种硅酸盐水泥和2种减水剂,用煤矸石等量替代部分水泥均会对减水剂的塑化效果产生负面影响,而与此相反,粉煤灰、矿渣粉和高钙粉煤灰有助于改善减水剂的塑化效果.分析了煤矸石、粉煤灰、矿渣粉和高钙粉煤灰等矿物掺合料对减水剂塑化效果的影响机理.     

Development of envelope efficiency labels for commercial buildings: Effect of different variables on electricity consumption

After the first federal law on energy efficiency was published in 2001, the Brazilian government promoted several actions on energy efficiency, including the Federal Regulation for Voluntary Labeling of Energy Efficiency Levels in Commercial, Public and Service Buildings. Divided into three parts, lighting system, HVAC and building envelope, it is expected to become mandatory in 2013. This paper describes the criteria adopted to evaluate the envelope efficiency level, focusing on the development of a regression equation which provides an electricity consumption indicator. The envelope label is divided into five efficiency levels, from A (more efficient) to E (less efficient), identified according to the electricity consumption indicator. The linear regression equation considers variables such as window to wall ratio (WWR), SHGC, solar protection angles, building volume indicators and the roof U_value. The U_value of the walls was excluded from the equation due to its non-linearity. Its relation with electricity consumption depends on internal gains, exterior temperatures, building size and thermal capacity of the walls and could not be described by a linear regression equation. Some limitations were identified and shape factor limits were provided. The envelope efficiency label is obtained by the comparison of the electricity consumption indicator of the proposed building with the electricity consumption indicators of two other building envelopes presented.     

Study on inhaled air quality in a personal air-conditioning environment using new scales of ventilation efficiency

A detailed study using computational fluid dynamics (CFD) was conducted on the influence of the difference in the effective diameters of air supply openings (air velocity, assuming the airflow rate to be constant) when using personal air-conditioning (PAC) with isothermal air currents. A new method to analyze the age of air (SVE3*) for individual supplies and the residual lifetime of air (SVE6*) for individual exhausts was developed and proposed. The study focuses on the individual supply openings and exhaust openings in a room with multiple supply openings and exhaust openings when using PAC. PAC with the larger supply opening resulted in less mixture with the surrounding air and a lower age of air than the smaller diameter, which therefore indicated better ventilation characteristics.     

Effect of the moment transfer efficiency of a beam web on deformation capacity at box column-to-H beam connections

This paper investigates the effect of moment transfer efficiency of a beam web on deformation capacity at beam-to-column connections. Non-linear finite element analysis of five connection models was conducted. Analytical results showed that the moment transfer efficiency of the connection with a box column was poor when compared to a connection with an H-column; this was due to the out-of-plane deformation of the column flange. Based on previous test data, analytical results were compared with experimental results. Analytical and experimental results showed that the deformation capacity of the connection with a box column decreased due to the poor moment transfer efficiency of a beam web, followed by strain concentration at the beam flange.     

基于生理指标评价人体热舒适、工作效率和长期健康的研究路线探讨

分析了人体在热环境中的生理响应机制,综述了国内外基于生理指标的人体热舒适、工作效率和长期健康的研究现状,指出生理指标在评价工作效率和人体健康方面具有重要价值,但对于热舒适研究只能作为一个辅助评价指标,并提出了生理指标在评价热舒适、工作效率和人体健康方面的研究路线。     

负荷不确定性对三联供系统配置和经济性的影响

利用围绕代表日负荷的概率分布来描述所有负荷的不确定性,以年总费用期望值为目标函数,建立了三联供系统的优化模型.根据一实例,系统地研究了负荷不确定性对三联供系统配置和经济性的影响.结果表明,负荷不确定性对三联供系统核心设备的配置影响不大,对辅助设备影响较大;随不确定性的增大,三联供系统初投资和运行费用都有所增加,系统经济优势有所下降.