Indoor levels of volatile organic compounds at Florentine museum environments in Italy

Indoor Air Quality monitoring in cultural institutions is of particular concern to protect these places and the cultural heritage content. An indoor monitoring campaign was performed in three museums in Florence (Italy) to determine the occurrence and levels of volatile organic compounds (VOCs). VOCs of interest included BTEX (benzene, toluene, ethylbenzene, xylenes), terpenes, aldehydes, organic acids, and cyclic volatile methyl siloxanes (cVMS). The most abundant VOCs in all samples analyzed were BTEX, which were strictly related to the traffic source, followed by siloxanes and terpenes. Among BTEX, toluene was always the most abundant followed by xylenes, ethylbenzene, and benzene. cVMS in exhibition rooms with the presence of visitors showed higher values compared to samples collected when the museums were closed. Terpenes showed not only the influence of vegetation-biogenic sources surrounding a museum but could also be related to the wood used for the construction of showcases and furniture and the use of cleaning products. Data obtained also showed the presence of organic acids and aldehydes whose source can be traced back to exhibits themselves and wood-based furniture. Assessing the levels of organic acids in museums is important because, over time, it can cause deterioration of the artifacts.     

Study on effect of diverse air inlet arrangement on thermal management of cylindrical lithium-ion cells

Lithium-ion cells are preferred in the electrical powertrain due to high-power density, compactness, and modularity. In real driving conditions, the cells undergo discharge rates as high as 4 C resulting in high heat generation affecting the performance. To obtain the maximum performance the pack construction and thermal management of cells are crucial parameters. In our work, air-cooled technique with diverse air inlet and staggered scheme with a two-channel partition approach for thermal management of the cylindrical lithium-ion cells are studied in computational fluid dynamics. The simulation model is validated with experimental results. The obtained results demonstrate that the cells in the dual-directional air inlet arrangement had low maximum temperature difference among and within the cells and required least fan work. This arrangement required least fan work to generate optimal air inlet velocity of 2 m/s for 1, 2, and 3 C and 4 m/s for 4 C discharge rates. There is a reduction of 50% and 33% fan work for 3 and 4 C discharge rates, which are the majority operating points. Also, it shows that the temperature uniformity within the cells has improved. The results of this study can used to optimize parameters for designing an enhanced thermal management system.     

Research on the hot surface ignition of hydrogen‐air mixture under different influencing factors

To further reveal the pre‐ignition characteristics of hydrogen internal combustion engine, the effect of hot surface characteristic parameters on the ignition characteristics of hydrogen‐air mixture was investigated in this research. Based on the prototype of the constant volume combustion bomb with an overhead glow plug, the duration from the heating of the hot surface to the combustion of hydrogen‐air mixture, the so‐called heating duration, was firstly researched under different fuel‐air equivalence ratio, initial temperature, initial pressure, hot surface temperature, and hot surface area, and the influence of each factor on the heating duration was analyzed. The results show that the order of the effect of each factor on the hot surface ignition is as follows: hot surface temperature > initial pressure of hydrogen‐air mixture > equivalent ratio > initial temperature of hydrogen‐air mixture > hot surface area. The influence of the hot surface characteristic parameters on the heating duration was further analyzed in detail. On this basis, the relationship among the critical ignition temperature, the heating duration and the hot surface area was researched and established. The results show that the heating duration is the only major factor affecting the critical ignition temperature. Finally, the research results were applied to analysis the pre‐ignition in hydrogen internal combustion engine.     

Exergy analysis of the diesel pre-reforming solid oxide fuel cell system with anode off-gas recycling in the SchIBZ project. Part I: Modeling and validation

Solid oxide fuel cell (SOFC) systems with anode off-gas recirculation (AGR) and diesel pre-reforming are advantageous because they can operate with the current fuel infrastructure. In the SchIBZ-project, the prototype of such a SOFC system for maritime applications has already been commissioned. In this first paper, we model the system devices to conduct an exergy analysis of this real SOFC plant and validate them with experimental values from experiments in laboratory scale. The results of our simulation agree well with the experimental values. The calculations with the validated results may be closer to the real thermodynamic behavior of such system components than previous literature.     

搪瓷承压水箱在空气源热泵中实际运用研究

随着经济的快速发展，人们的生活水平得到了显著的提升，由此，人们对生活的质量就有了更高的要求，尤其是对热水的要求，更是出现了显著的提升。当前，国内的空气源热水器行业发展的十分迅速，能够充分地满足人们对热水的需求，这使得空气源热泵在人们的生活中应用的越来越广泛。在本文中，介绍了空气源热泵的工作原理以及优点，并介绍了搪瓷承压水箱在空气源热泵中的实际应用。     

气动潜孔锤跟管钻进技术在岩土工程勘察施工中的应用

以渤船重工新型总装生产线工程岩土工程勘察项目为依托，应用KG940 A型高风压履带式潜孔钻车﹑采用气动潜孔锤跟管钻进工艺，结合空气正循环排渣方式，摸索总结出一套针对复杂破碎覆盖层的干式成孔新方法，钻进效率及钻孔质量显著提高，为岩土工程勘察勘探孔施工增添了一种新的思路。     

Particulate matter emitted from ultrasonic humidifiers—Chemical composition and implication to indoor air

Household humidification is widely practiced to combat dry indoor air. While the benefits of household humidification are widely perceived, its implications to the indoor air have not been critically appraised. In particular, ultrasonic humidifiers are known to generate fine particulate matter (PM). In this study, we first conducted laboratory experiments to investigate the size, quantity, and chemical composition of PM generated by an ultrasonic humidifier. The mass of PM generated showed a correlation with the total alkalinity of charge water, suggesting that CaCO₃ is likely making a major contribution to PM. Ion chromatography analysis revealed a large amount of SO₄²⁻ in PM, representing a previously unrecognized indoor source. Preliminary results of organic compounds being present in humidifier PM are also presented. A whole-house experiment was further conducted at an actual residential house, with five low-cost sensors (AirBeam) monitoring PM in real time. Operation of a single ultrasonic humidifier resulted in PM_2.5 concentrations up to hundreds of μg m⁻³, and its influence extended across the entire household. The transport and loss of PM_2.5 depended on the rate of air circulation and ventilation. This study emphasizes the need to further investigate the impact of humidifier operation, both on human health and on the indoor atmospheric chemistry, for example, partitioning of acidic and basic compounds.     

Quantitative investigation of air gaps entrapped in multilayer thermal protective clothing in low‐level radiation at the moisture condition

The effects of air gaps entrapped within the multilayer protective clothing system on the thermal performance were studied during low‐level radiation (2–10 kW/m²). A bench‐scale apparatus was designed to produce the liquid droplets and simulate human sweat transferring through the multilayer fabric system. Two air gaps located between the outer shell and the moisture barrier (Gap A) and between the moisture barrier and the thermal liner (Gap B) were used with different gap sizes (0, 2, and 5 mm). The thermal resistance analysis for the heat transfer with a multilayer flat wall was used to interpret the effects of air gap. The results show that the total thermal resistance of a multilayer clothing system and the thermal resistances of the two air gaps are linearly related with the level of heat flux. It is also indicated that the air gap position affects the beneficial effect of the gap size. The effect of Gap B to improve the thermal performance is better than that of Gap A. Copyright © 2014 John Wiley & Sons, Ltd.     

Detection of occupancy profile based on carbon dioxide concentration pattern matching

Occupancy is one of major factors influencing indoor microclimate. The aim of this work was to determine the influence of this factor on indoor air quality (IAQ) on the basis of CO₂ concentration measurements and statistical analysis. We wanted to identify periods of time when IAQ was strongly affected by the occupancy described by the given profile. The proposed approach consisted of several stages. The CO₂ concentration was measured and recorded in the form of univariate time series. Then, the relationship between occupancy and internal structure of the time series was disclosed. There were distinguished segments based on sample periodogram. Each segment was associated with a particular occupancy profile. In order to detect how human factor represented by a given occupancy profile influences IAQ we proposed to use pattern matching. In this approach there was examined the similarity between segments of the time series and the pattern of CO₂ variability, which represented a selected occupancy profile. The analysis was performed in time domain using moving time window technique. The similarity was judged based on two types of indexes, namely correlation coefficients and distance measures. It was shown that our approach may be applied to successfully detect a particular occupancy profile. The best performance was achieved when using angular distance as the similarity index. In this case we reached 82% true positive and 22% false positive detections. The proposed method may be applied in diagnostics problems to reveal sources of indoor air quality problems.     

浅谈军用空调制冷系统管路抗振动、抗冲击工艺措施

本文介绍了军用空调制冷系统管路存在的常见管路断裂问题,并对系统管路出现的断裂缺陷进行了详细的原因分析,由此提出解决该问题的相应工艺措施。将该工艺措施用于实际生产,并生产出多品种、大批量的产品。