Ventilation measurement using spot sampling of sulphur hexafluoride on a solid adsorbent

A technique for measuring the ventilation rate using spot sampling of sulphur hexafluoride (SF₆) on a solid adsorbent for subsequent thermal desorption and gas chromatographic analysis has been developed. This paper describes the mathematical model used, the analytical details of the technique, as well as results from a validation test using an experimental chamber. The mathematical model assumes an exponential decay of the tracer gas concentration. The precision of the analytical procedure was estimated to be better than 9% whilst the error of the measured ventilation rate of the test chamber was 5%.     

Ventilation system design for a church pipe organ using numerical simulation and on-site measurement

Since old churches have had heating installed, more complaints have arisen of organs sounding out of tune. Sound frequency of organ pipes is dependent on air temperature. Old churches tend to have very large volumes, so are typically heated just before and during services in wintertime, in order to reduce energy usage. Warm air plumes rise at radiators and spread out into the room, finally reaching the cold organ casing where they cause a non-uniform temperature distribution within. If pipes standing in different temperature zones are played at the same time the organ sounds out of tune due to clearly audible beats (interference between two slightly different frequencies). The purpose of this study was to design a ventilation system inside the organ casing, able to create a uniform temperature distribution around the pipes. A computational fluid dynamic (CFD) model was developed for the St. Martin church in Oberesslingen, Germany. It was validated by on-site measurements that had been carried out in the organ casing of the church. Four organ divisions containing 300–500 pipes were represented by equivalent porous material zones. Their properties were determined using an auxiliary two-dimensional model of a staggered array consisting of 392 pipes. The effect of different ventilation system settings on the temperature field in the organ casing was examined. Best results were achieved by a system consisting of two ventilation lines together with a thin, synthetic net placed at the open interface between church and organ casing in order to reduce warm air inflow.     

Foam concentration measurement techniques

Three types of foam concentration measurement techniques are examined: total fluorine content, optical absorption, and specific conductivity. Specific conductivity was found to be the most useful for field measurements and was therefore compared with the traditional refractive index approach. It was found that electrical conductance provides a more accurate method of estimating the concentration of AFFF solution than does the refractive index technique described in NFPA 11.     

Ventilation and performance in office work

Outdoor air ventilation rates vary considerably between and within buildings, and may be too low in some spaces. The purpose of this study was to evaluate the potential work performance benefits of increased ventilation. We analyzed the literature relating work performance with ventilation rate and employed statistical analyses with weighting factors to combine the results of different studies. The studies included in the review assessed performance of various tasks in laboratory experiments and measured performance at work in real buildings. Almost all studies found increases in performance with higher ventilation rates. The studies indicated typically a 1-3% improvement in average performance per 10 l/s-person increase in outdoor air ventilation rate. The performance increase per unit increase in ventilation was bigger with ventilation rates below 20 l/s-person and almost negligible with ventilation rates over 45 l/s-person. The performance increase was statistically significant with increased ventilation rates up to 15 l/s-person with 95% CI and up to 17 l/s-person with 90% CI. Practical Implications We have demonstrated a quantitative relationship between work performance and ventilation within a wide range of ventilation rates. The model shows a continuous increase in performance per unit increase in ventilation rate from 6.5 l/s-person to 65 l/s-person. The increase is statistically significant up to 15 l/s-person. This relationship has a high level of uncertainty; however, use of this relationship in ventilation design and feasibility studies may be preferable to the current practice, which ignores the relationship between ventilation and productivity.     

Ventilation performance prediction for buildings: Model assessment

Designing ventilation systems for buildings requires a suitable tool to assess the system performance. This investigation assessed seven types of models (analytical, empirical, small-scale experimental, full-scale experimental, multizone network, zonal, and CFD) for predicting ventilation performance in buildings, which can be different in details according to the model type. The analytical model can give an overall assessment of a ventilation system if the flow could be approximated to obtain an analytical solution. The empirical model is similar to the analytical model in terms of its capacities but is developed with a database. The small-scale model can be useful to examine complex ventilation problems if flow similarity can be maintained between the scaled model and reality. The full-scale model is the most reliable in predicting ventilation performance, but is expensive and time consuming. The multizone model is a useful tool for ventilation design in a whole building, but cannot provide detailed flow information in a room. The zonal model can be useful when a user has prior knowledge of the flow in a room. The CFD model provides the most detailed information about ventilation performance and is the most sophisticated. However, the model needs to be validated by corresponding experimental data and the user should have solid knowledge of fluid mechanics and numerical technique. Thus, the choice for an appropriate model is problem-dependent.     

Ventilation strategy and air change rates in idealized high-rise compact urban areas

We regarded high-rise compact urban areas as obstacles and pathways to the approaching wind. Flow rates across street openings, open street roofs and along street networks contribute to air exchange between urban airspaces and their external surroundings. We numerically studied the ventilation and air change rates in some aligned square building arrays (the building width B = 30 mm, building heights H = 2B or 2.67B) with building area densities of λ_p = 0.25 or 0.4 (i.e. the ratio between the plan area of buildings viewed from above and the total underlying surface area). The main and secondary streets are parallel and perpendicular to the approaching wind respectively. Urban parameters are found important to the ventilation. The taller buildings (H = 2.67B) may capture larger inflow rates across windward street openings than the lower (H = 2B). Wider streets and smaller building area density provide more wind pathways and obtain larger flow rates along street networks. Meanwhile, the flow rates along the street may quickly decrease due to strong resistances produced by high-rise buildings, so the total street length should be limited, otherwise the ventilation in downstream regions is not good. The secondary streets always experience worse ventilation than the main streets. A building height variation benefits ventilation in the secondary streets by enhancing vertical mean flow rates across street roofs in contrast to those with uniform heights. If the base of all buildings is open from z = 0 to 0.33B, the ventilation in both the main and secondary streets becomes better.     

Environmental performance measurement indicators in construction

Environmental management system (EMS) has been suggested for promoting effective environmental protection. Environmental performance assessment (EPA) is a critical tool of the EMS in checking, reviewing, monitoring and evaluating environmental performance of organizations. In order to implement EPA, performance measurement indicators (PMIs) that show the environmental performance outcome are required, which, however, are lacking in the construction industry. By conducting a structured survey, in the form of a questionnaire and interviews, this paper attempts to identify three key output indicators, namely “regulatory compliance”, “auditing activities” and “resources consumption”, and nine sub-indicators. On the basis of their relative importance, the top five sub-indicators are “fines and penalties”, “complaints/warnings”, “non-compliance records of inspection”, “non-conformance reports”, and “reports of marginal cases put under observations”. The first three sub-indicators fall into the “regulatory compliance” category and the latter two into the category of “auditing activities”.     

水厂加药自动计量、调节系统设计

以一个典型设计为例,介绍了水厂加药自动计量、自动调节系统的结构和原理.该系统的使用将加药自动计量、自动调节和外购药剂核算纳入水厂的科学管理,总结出的适合现场运行、操作的数学模型和PLC程序可以确保水质,提高水厂运行和管理效率,具有很好的实用价值.     

战略导向的企业绩效管理体系--"平衡记分卡"在勘察设计企业的应用初探

本文对平衡记分卡战略绩效管理体系在勘察设计企业中的应用进行了初步探讨。     

天然气贸易计量现状分析及完善对策

对陕西省天然气贸易计量现状进行了分析,提出了完善天然气贸易计量工作,确保计量公正、准确的具体对策。     

温度控制与污染物浓度控制相独立的通风空调系统

为解决传统通风空调系统温度控制与污染物浓度控制需求风量不匹配的问题,提出了一种温度控制与污染物浓度控制相独立的通风空调系统结构和控制方法。通过室内负荷计算及PM2.5浓度计算,对比分析了北京、上海、深圳地区在保证室内温湿度需求时典型办公室内的PM2.5浓度水平。结果表明,该通风空调系统可以同时满足室内温度和PM2.5浓度的控制要求,尤其在室外气候温和且大气污染较重时期对室内环境的保障效果更为明显。以北京地区2018年为例计算,在室内温度相同情况下,采用该通风空调系统室内PM2.5浓度全面达标,而采用传统通风空调系统则有10.3%的时间超标。     

Analysis of microfiltration performance with constant flux processing of secondary effluent

This study involves the microfiltration (MF) of secondary effluent from a sequencing batch reactor processing industrial waste. The MF unit was a hollow fibre module with gas backwash capability, and operated with pumped permeate (controlled flux) and dead-end, crossflow or intermittent feed. The results showed that crossflow had no effect on flux and that intermittent dead-end filtration was less productive than non-intermittent operation. For dead-end filtration the cycle-time between gas backwashes depends very significantly on the imposed flux (varying from about 100 min at 30 L/m² h to about 5 min at 90 L/m² h) and the feed solids content. Optimal operation has to balance operating (energy for backwash) costs and the capital (membrane area) costs. Cost analysis based on capital and energy costs indicates that for lower energy cost the unit needs to be operated at lower imposed flux but to minimise total cost it is necessary to operate the unit above 60 L/m² h imposed flux depending on the maximum transmembrane pressure (TMP) allowed before back washing. Further analysis of TMP profiles showed that membrane resistance increased over time towards a maximum, which tended to increase with imposed flux. This implies more frequent chemical cleaning for high flux operation. Specific cake resistances were deduced from the profiles and indicated cake compression at higher flux and larger maximum TMP. Results of long-term trials are also reported. Water quality analysis shows consistent quality of permeate regardless of operating conditions.     

Ventilation performance prediction for buildings: A method overview and recent applications

This paper presented an overview of the tools used to predict ventilation performance in buildings. The tools reviewed were analytical models, empirical models, small-scale experimental models, full-scale experimental models, multizone network models, zonal models, and Computational Fluid Dynamics (CFD) models. This review found that the analytical and empirical models had made minimal contributions to the research literature in the past year. The small- and full-scale experimental models were mainly used to generate data to validate numerical models. The multizone models were improving, and they were the main tool for predicting ventilation performance in an entire building. The zonal models had limited applications and could be replaced by the coarse-grid fluid dynamics models. The CFD models were most popular and contributed to 70 percent of the literature found in this review. Considerable efforts were still made to seek more reliable and accurate models. It has been a trend to improve their performance by coupling CFD with other building simulation models. The applications of CFD models were mainly for studying indoor air quality, natural ventilation, and stratified ventilation as they were difficult to be predicted by other models.     

Virus concentration using hollow fiber membranes

A cellulose acetate hollow fiber membrane permeator was used to concentrate polio-l virus from 51. of water. The objective of the study was to evaluate the effect of several independent variables—radial flow direction, feed flow rate. feed concentration. cell type and effectiveness of backwashing—on process performance. The average virus recovery was 85° for a 50-fold dehydration in about 1 h.It is envisioned that the hollow fiber permeator. because of its compactness. low water hold-up. light weight and low cost. will be used as the first step of a system to concentrate and quantify viruses in contaminated waters.     

Ventilation and energy performance of partitioned indoor spaces under mixing and displacement ventilation

Large variation in indoor air quality (IAQ) and thermal comfort can occur in partitioned office spaces due to heterogeneous air mixing. However, few published studies examined IAQ, thermal comfort, and energy performance of partitioned occupied spaces, which are commonly found in today’s buildings. The objective of this study is to evaluate indoor environmental quality and air conditioning performance of a partitioned room under two typical ventilation modes: (1) mixing ventilation and (2) displacement ventilation. For a total of six representative air-conditioning scenarios, three-dimensional computational fluid dynamics (CFD) simulations are performed to examine temperature distribution, ventilation effectiveness, energy consumption, and local thermal comfort for two partitioned spaces. Simulation results indicate that temperature distribution in a partitioned room is a strong function of ventilation strategy (mixing vs. displacement), but marginally affected by diffuser arrangements. Local age-of-air (air freshness) significantly varies with both diffuser arrangement and ventilation strategy. Regarding energy consumption, displacement ventilation can achieve an indoor set-point temperature in the partitioned spaces about two times faster than mixing ventilation. Under mixing ventilation, the time to achieve a set-point temperature was notably reduced when each partitioned space is served by its own diffuser. For the same supply airflow rate, displacement ventilation can generate local draft risk at ankle level, while mixing ventilation may result in a draft sensation in wider areas around an occupant. Overall, the results suggest that mixing ventilation system can save energy if each partitioned zone is served by its own diffuser such as a multi-split air conditioning. However, when multiple partitioned zones are served by only one diffuser, displacement ventilation is more energy-efficient and can achieve higher ventilation effectiveness than mixing ventilation.     

定流量与变流量系统冷水温度节能控制策略

分析了冷水温度对冷水机组COP的影响.讨论了定流量系统和采用变压差阀位控制的变流量系统的冷水温度调节和节能控制的最佳运行策略.     

双臂电桥测量微电阻阻值

对双臂电桥正、误几种接线和原理进行了分析，并通过测量实例，分析了错误接线对测量结果产生的不良影响，对测量者有一定的参考意义。     

能谱仪氡测量的计数与浓度的自动计算

本文提供了一种γ谱仪解谱软件基础上,自动计算环境氡浓度的方法。该方法解决了用活性炭盒法测量环境中的氡浓度时计算量大且容易出现人为错误的问题,以及可以由γ谱仪的解谱软件得出特定能量位置的计数自动转换为环境浓度的精确计算。     

Automated performance measurement for 3D building modeling decisions

Building information modeling (BIM) is instrumental in documenting design, enhancing customer experience, and improving product functionality in capital projects. However, high-quality building models do not happen by accident, but rather because of a managed process that involves several participants from different disciplines and backgrounds. Throughout this process, the different priorities of design modelers often result in conflicts that can negatively impact project outcomes. To prevent such unwanted outcomes from occurring, the modeling process needs to be effectively managed. This effective management requires an ability to closely monitor the modeling process and correctly measure the modelers' performance. Nevertheless, existing methods of performance monitoring in building design practices lack an objective measurement system to quantify modeling progress. The widespread utilization of BIM tools presents a unique opportunity to retrieve granular design process data and conduct accurate performance measurements. This research improves upon previous efforts by presenting a novel application programming interface (API)-enabled approach to (a) automatically collect detailed model development data directly from BIM software packages in real-time, and (b) efficiently calculate several modeling performance measures during schematic and design development phases of building projects. These indicators can be used to properly arrange modeling teams in the quest for high-quality building models. The specific objectives of this study to examine the feasibility of a proposed automated design performance measurement framework, and to identify optimal modeling team configurations using empirical performance information. A passive data recording approach allows for the real-time capture of comprehensive user interface (UI) interaction and model element modification events. The proposed framework is implemented as an Autodesk Revit plugin. Next, an experiment is conducted to capture data using the developed Revit plugin. Experiment participants' individual production rates are estimated to establish the validity of the proposed approach to identify the optimal design team configuration. The presented approach uses the earliest due date (EDD) sequencing rule in combination with the critical path method (CPM) to calculate the maximum lateness for different design team arrangements.     

Implementation of project strategy to improve new product development performance

Poor project strategy is one of the major causes of project failure. However, many projects do not adequately develop strategy leading to a poor basis in subsequent phases. Thus, implementation of project strategy is critical to the success of any project. The primary purpose of this study was to validate a model for assessing the relationships among implementation of project strategy, new product development (NPD) project outcomes, and market performance. The analyses suggest that implementation of differentiation, operational, and quality strategies may improve NPD project outcomes. The research results also imply that improvement in NPD project outcomes may enhance market performance, while it helps accomplish the market share and sales goals.