Nonlinear Least-Squares Minimization Applied to Tracer Gas Decay for Determining Airflow Rates in a Two-Zone Building

Abstract We developed a method based on tracer gas decay measurements to quantify the airflow rates, including the interzonal airflows, in a two-zone building: different tracer gases were simultaneously pulse-injected into each of the two zones and the evolution of the gas concentrations in each zone was measured; theoretical concentration profiles obtained by solving dynamic material-balance equations for two coupled, well-mixed zones were fit to the experimental data using nonlinear least-squares minimization; and estimates of the airflow rates were iteratively refined until a best fit was achieved between the model and the data. We conducted experiments validating the method in two full-sized rooms of a test house. Airflows were controlled using blowers, and mixing was ensured by the use of fans. Airflow rates inferred by the tracer gas technique agreed with imposed airflow rates within an average absolute error of 8%. Results are also reported for two experiments conducted in the same structure under uncontrolled conditions. Goodness-of-fit tests revealed no statistically significant differences between measured tracer gas concentrations and theoretical concentration profiles constructed using the least-squares parameter estimates.     

Enhancement of Drying Rate in Paper Machines with Multi-Functional Radial Jet Reattachment Blow Boxes — Theoretical Analysis

Multi-functional radial jet reattachment blow boxes deliver a dry air into the pockets of the dryer section of a paper machine by impinging directly onto the unsuppned sheet in the open diaw. The air flow also maintains or improves the sheet swbility.

The iadial jet reattachment blow box technology pmvides a significant enhancement in drying rates. The theoretical drying results are presented in terms of average drying rates, moisture and temperature pmfiles along the drying section with and without the presence of the multi-functional radial jet reaaachment blow boxes. The thcorclical results indicate that enhancements of drying rates within the range of 8% to 25% are feasible depending on ihe operating conditions and machine configuration.     

江西省大茅山铜钼矿通风方式的探讨

对国内外无底柱分段崩落法采场通风方式,进行了系统的研究,在此基础上,提出在大茅山铜钼矿开采条件下的贯穿风流通风新形式,研究表明,该方案是当前无底柱分段崩落法的最佳通风方式之一.     

Ventilation: A behavioural approach

Behavioural studies of the window-opening habits of families in one hundred and twenty three houses show a strong seasonal pattern. During winter window opening is closely related to moisture level in the external air. In summer it is more closely linked to mean daily temperature. There are wide differences between families, with larger families having more open windows. Re-examination of ventilation criteria suggests three seasons, one in deep winter which needs minimum adequate air for body odour removal, the second in spring/autumn for controlling moisture and the third in summer for cooling.     

VENTILATION INFLUENCE UPON INDOOR AIR RADON LEVEL

ＶＥＮＴＩＬＡＴＩＯＮ　ＩＮＦＬＵＥＮＣＥ　ＵＰＯＮ　ＩＮＤＯＯＲ　ＡＩＲ　ＲＡＤＯＮ　ＬＥＶＥＬＴｉａｎＤｅｙｕａｎ（田德源）（ＬａｂｏｒａｔｏｒｙｏｆＩｎｄｕｓｔｒｉａｌＨｙｇｉｅｎｅ，ＭｉｎｉｓｔｒｙｏｆＰｕｂｌｉｃＨｅａｌｔｈ，Ｂｅｉｊｉｎｇ...     

电焊烟尘的危害与防治

水文详细阐述了电焊烟尘对空气环境的污染以及对人体带来的危害，探讨了如何经济而有效地防治电焊烟尘的综合技术措施。     

Hygienic Aspects of Processing Oil Residues in Ventilation Ducts

The hygienic properties of two types of processing oils used in the manufacture of galvanised metal air ducts mere investigated. One of the oils was based on mineral oil and the other on vegetable oil. Evaporation of the oil emulsions from the galvanized metal surface was followed for ten months, after which the water-binding capacity of the residues was measured in increasing and decreasing RH at the range of 75-100%. The potential of processing oil residues to act as nutrients for fungi was tested with Penicillium brevi-compactum in the laboratory. The odour emission of oil residues was evaluated with the aid of a trained panel for eight months. After the ten months, the residue of mineral-oil- and vegetable-oil-based products was 60% and 79% of the original amount, respectively. Both oils were able to absorb water but desorption of the water from vegetable-oil-based products was delayed, thus increasing the risk of fungal growth. The residues of both oils provided sufficient nutrients for fungal growth. The odour emissions from the oil residues were high and that of vegetable oil tended also to increase. To attain high indoor air quality, duct manufacturing methods which do not leave residues should be developed.     

Mixing of a Point-Source Indoor Pollutant by Forced Convection

The mixing rate of pollutants emitted from indoor sources influences the effectiveness of pollutant removal by building ventilation and the potential variability of exposure for a given release scenario. Quantitative information is scant on the mixing rate and the factors that govern it. We present mixing data for an instantaneously released tracer gas, carbon monoxide, in a sealed, unoccupied room under a range of forced airflow conditions, in which the flow is induced by blowers. The resulting mixing times, from 2 to 42 minutes, are related to the mechanical power of the air jets produced by the blowers. Mixing times are found to correlate well with the inverse of the cube root of power, in accordance with theoretical predictions and experimental observations for mixing in chemical reactors. The exposure index, defined as the time-averaged concentration at a point relative to the time-averaged concentration for the room as a whole, is presented for three experimental conditions, yielding quantitative information on the appropriateness of the well-mixed hypothesis under various flow conditions. In general, the exposure period following instantaneous release of a point-source pollutant must be much greater than the mixing time for the assumption of uniform mixing to hold. The correlation between mixing time and power input is used to predict the mixing time from the mixing action of a supply air jet for a typical ventilation scenario. The predicted mixing time, τ_mix～7 min, is substantially lower than the time scale for removal by ventilation, τ_vent～48 min. Under these conditions, complete mixing of an instantaneous release, point-source pollutant would be approximately attained within the interior space well before the pollutant would be thoroughly removed by ventilation.     

薛湖煤矿通风系统优化改造

针对薛湖煤矿的实际情况,通过通风阻力测定得出相应阻力系数及风阻值,通过风机性能鉴定得到风机实际运行曲线,利用矿井通风网络分析软件对薛湖煤矿现阶段通风系统进行分析,查明矿井通风系统存在问题,并提出优化改造方案。通过对优化方案的解算分析、比较,选取较优方案作为薛湖煤矿最终改造方案,解决了矿井主要巷道风速超限和后期生产工作面风量不足的问题,有效保证了矿井的安全生产。     

云南省某剧院空调通风设计

云南省某剧院采用直膨式全空气空调系统,空调系统由室外机直接蒸发式全空气处理机组两部分组成,无需水泵、冷却塔等设备,安装使用及维护方便。机组置于屋顶或者室外空地,无需机房,节省初投资,维修方便。机组不需要二次冷媒,系统效率高。剧院采用大风道,消声减震处理较为简单。介绍剧院直膨式空调系统、通风系统设计,包括空调冷热源、空调系统、防排烟系统、节能、自控、消声与隔振处理,直膨机与其他空调冷热源方案对比等内容。