Statistical model for the volume rate reaching the end of ventilation duct

Auxiliary ventilation is used to ventilate dead-ends of the drivages, and the most common method employed is to use auxiliary fans and ducting. In order to provide a safe and comfortable environment, it is necessary to provide sufficient air to the working areas. The optimum design of auxiliary ventilation systems may be difficult owing to the methods used in the design of such systems that require complex calculations. In this study, by evaluating data gathered from Turkish Hardcoal Enterprises, a predictive model of the volume flow rate reaching the end of a leaky ventilation duct for a simple auxiliary ventilation system was developed using multiple regression analysis. The independent variables that enter the regression were chosen as duct diameter, fan flow output, fan operating pressure, frictional pressure drop, duct length, duct resistance, and resistance coefficient of leakage paths. The coefficient of determination (R²) obtained for the predictive model was 0.931, and the residual analysis indicated that the model was statistically acceptable. Also, by using the two-sample t-test, it was shown that the developed regression model was consistent with the results obtained from another data set not included in the derivation of the presently developed regression model.     

A simple model to study the influence of fluctuating airflow on the effective air exchange rate when using natural ventilation

Fluctuating airflow may strongly influence the real air exchange rate when using natural ventilation, resulting in a larger “effective” air exchange rate than the “mean” air exchange rate calculated by conventional methods (i.e., the network method). To study the effective air exchange rate during natural ventilation under conditions of actual use, this study proposes a simple model that accounts for fluctuating airflow. The model assumes that the airflow near a building opening fluctuates regularly and velocity is assumed to have either a square or sine wave pattern. Our analysis shows that the effective air exchange rate is larger when accounting for fluctuating airflow. This suggests that the mean air exchange rate should not be calculated without consideration of real airflow fluctuations.     

The ventilation and climate modelling of rapid development tunnel drivages

The extraction of minerals and coal at greater depth, employing higher-powered machinery to increase production levels has imposed an increased burden on ventilation systems to maintain an acceptable working environment. A deterioration in the climate experienced within these workings may also adversely affect the health and safety of the workforce. In the UK, mineral extraction is now being practiced at depths of over 1000 m. In addition, the adoption of continuous miner and tunnel bolting support methods has permitted improved development rates to be achieved at the cost of increased emissions of dust, gas and heat and humidity. There is a recognized need to improve the efficiency in the design and operation of auxiliary ventilation systems to maintain an adequate underground environment and climate. Any improvement achieved in the quality, quantity and control of the delivered ventilation will assist in the provision of improved gas and dust dilution and climatic control. Due to the constraints imposed by the mining method, there may be an economic or practical limit to the climatic improvement that may be obtained by the sole use of ventilation air. Where this limit is identified, there may be the need to consider the selective application of air-cooling systems. The paper details the construction of a computer based climatic prediction tool developed at the University of Nottingham. This work builds upon earlier research (Ross et al., 1997, Proceedings of 6th International Mine Ventilation Congress, SME, Littleton, CO, pp. 283–288) that developed a prototype model for short tunnel developments. The current model predicts the psychrometric and thermodynamic conditions within long rapid development single entry tunnel drivages. The model takes into account the mass and heat transfer between the strata, water, machinery and the ventilation air. The results produced by the model have been correlated against ventilation, climatic and operational data, obtained from a number of rapid tunnel developments within UK deep coalmines. The paper details the results of a series of correlation and validation studies conducted against the ventilation and climate survey data measured within 105s district Tail Gate tunnel development at Maltby Colliery, UK. The paper concludes by presenting the results of a case study that illustrate the application of the validated model to the design and operation of an integrated mine ventilation and cooling system. The case study illustrates the effect that an increased depth and hence increased virgin strata temperature has on the climate experienced within rapid tunnel developments. Further investigations were performed to identify the optimum cooling strategy that should be adopted to maintain a satisfactory climate at the head of the drivage.     

通风对狭长空间电缆火灾影响数值分析

为研究狭长空间电缆发生火灾后的热流场特性规律,建立了适用于狭长空间的火灾仿真计算数学模型,对控制方程组进行了变形和离散,并用数值程序求解,得到电缆发生火灾后烟气蔓延特性规律、不同时刻温度场分布以及特征位置温度测点随时间的变化规律,分析了不同位置的火灾特征参数变化的差异性,探讨了通风对火灾热流场的影响。通过分析火灾流场特性变化规律,为狭长空间电缆火灾探测设计及通、排风设计提供参考。     

自然通风建筑室内气流组织优化研究

通过fluent模拟软件对诸多因素中最为关键的风向、风速、开窗位置及面积等进行了优化模拟研究。结果表明:在西安地区,南向为最佳风向,室外风速在1.3～2.5 m/s之间,基本上都能满足自然通风要求,最佳风速为1.5 m/s;综合考虑采光和自然通风因素,窗户开在墙的中间为宜;北向面积适当减小有利于自然通风在室内形成较均匀的气流,在保证建筑节能标准的前提下,增大南向窗户面积有利于自然通风。     

长距离隧道施工中通风排水等问题浅析

根据广州市轨道交通三号线的工程实例,分析了长距离隧道盾构工程的排水、通风降温及水平运输等问题,并介绍了解决问题的具体方法,以积累长距离隧道施工经验,从而保证隧道施工的顺利进行。     

长大隧道通风施工技术

结合六郎隧道设有贯通平导的特点和现场实际任务情况,采用压入式和巷道式通风于不同施工阶段分步实施的通风方案,通过设计与风量计算,合理配置风机,解决了六郎隧道的通风问题。     

龙泉山长大瓦斯隧道施工通风

以进口工区为例,对龙泉山长大瓦斯隧道采用的射流巷道式通风系统进行了介绍,并对实施过程中通风方案的两次优化进行了分析,最后,提出了一些有参考价值的结论。     

正压送风量的一种计算方法

针对装有正压送风系统的高层建筑，分析了影响正压送风量分配状况的因素，这些相关因素包括送风部位，同时开门楼层数和开门门洞的风速。提出了以门开启时通过门洞的空气流足以阻挡着火层或有烟层烟气流的水平扩散为基础的正压送风量计算公式。     

Experimental and numerical study of room airflow under stratum ventilation

This paper investigates the air movement, air temperature profile and gaseous contaminant transportation in an individual office with stratum ventilation. The room temperature is elevated compared with conventional standards. The experimental investigation is carried out in an environmental chamber with the presence of heat generating rectangles used to simulate an occupant and a computer. Measurements of temperature, velocity, and CO₂ concentration are carried out for nine plumb lines in the chamber. Up to sixteen points are measured along each plumb line. The experimental data of the aforesaid three parameters of the individual office in warm condition under stratum ventilation are presented. The experimental data collected are used to validate a re-normalization group (RNG) k–? turbulence model used for the warm condition. The agreements between the predicted values and experimental results are acceptable, which demonstrates the feasibility of simulating indoor airflows at elevated room temperature under stratum ventilation by the RNG k–? turbulence model.     

纵向通风风速对锯末正向阴燃过程的影响

为探讨通风条件对阴燃过程的影响,笔者利用小型阴燃试验炉,研究了纵向通风风速对落叶松锯末正向阴燃过程中的阴燃建立时间、阴燃速度、阴燃温度和质量损失的影响。结果表明,在不同的通风风速下,阴燃的建立时间差别不大,但总平均阴燃速度随着通风风速的增加而明显增大;沿阴燃传播方向,不同位置处的平均阴燃速度均呈现先增大后减小的趋势,阴燃温度均依次出现先升高后下降的变化趋势;当通风风速 v=0 m/s 时,阴燃最高温度达 451.9 ℃;锯末阴燃质量损失速率和最终剩余质量均随通风风速的增加而增大。研究结果可以为阴燃火灾事故预防提供一定参考。     

容积率对房地产开发项目的影响

容积率是房地产开发项目规划设计条件中最重要的指标之一,对项目的定位、成本、进度、投资效益等产生不同程度的影响.     

Experimental study of airflow characteristics of stratum ventilation in a multi‐occupant room with comparison to mixing ventilation and displacement ventilation

The motivation of this study is stimulated by a lack of knowledge about the difference of airflow characteristics between a novel air distribution method [i.e., stratum ventilation (SV)] and conventional air distribution methods [i.e., mixing ventilation (MV) and displacement ventilation (DV)]. Detailed air velocity and temperature measurements were conducted in the occupied zone of a classroom with dimensions of 8.8 m (L) × 6.1 m (W) × 2.4 m (H). Turbulence intensity and power spectrum of velocity fluctuation were calculated using the measured data. Thermal comfort and cooling efficiency were also compared. The results show that in the occupied zone, the airflow characteristics among MV, DV, and SV are different. The turbulent airflow fluctuation is enhanced in this classroom with multiple thermal manikins due to thermal buoyancy and airflow mixing effect. Thermal comfort evaluations indicate that in comparison with MV and DV, a higher supply air temperature should be adopted for SV to achieve general thermal comfort with low draft risk. Comparison of the mean air temperatures in the occupied zone reveals that SV is of highest cooling efficiency, followed by DV and then MV.     

The effect of floor heat source area on the induced airflow in a room

We examine the role of heat source geometry in determining rates of airflow and thermal stratification in natural displacement ventilation flows. We modify existing models to account for heat sources of finite (non-zero) area, such as formed by a sun patch warming the floor of a room. Our model allows for predictions of the steady stratification and ventilation flow rates that develop in a room due to a circular heat source at floor level. We compare our theoretical predictions with predictions for the limiting cases of a point source of heat (yielding a stratified interior), and a uniformly heated floor (yielding a mixed interior). Our theory shows a smooth transition between these two limits, which themselves result in extremes of ventilation, as the ratio of the heat source radius to the room height increases. Our model for the transition from displacement to mixing ventilation is compared to previous work and demonstrates that the transition can occur for smaller sources than previously thought, particularly for rooms with large floor area compared to ceiling height.     

铁路特长隧道施工通风排烟方案探讨

通过论述吕梁山隧道施工中不同的施工阶段,调整和采用不同的通风方案,动态解决长大隧道施工中的通风排烟难题,重点介绍了方案的选择,机型的配置,取得的效果等。     

《通风管道沿程阻力计算选用表》数据测试及分析

编制过程中,将原《全国通用通风管道计算表》中钢板风管、除尘风管、气密性风管的主要数据,经计算并测试校核后进行精简列入新编内容,同时增加了螺旋风管、水硬性无机玻璃钢风管、氯氧镁水泥风管、玻纤风管、酚醛风管、聚氨酯复合风管等的计算图表。误差分析表明,比摩阻的绝对误差为0.067Pa/m,相对误差为2.54%。     

多股等羽流的速度与流量修正及其对高大空间自然通风的影响

根据动量叠加原理对多股等羽流的相互作用进行了研究，定义了三个速度修正系数和流量修正系数。通过数值计算，分析了平均速度修正系数、流量修正系数随高度和热源间距的变化规律。将相互作用的多股等羽流应用于一种高大空间二区自然通风模型，计算结果显示多股等羽流的相互作用提高了热分层高度，增加了通风量，对高大空间自然通风的影响十分明显。     

浅谈工业厂房的通风设计

介绍了工业厂房通风的主要形式为自然通风、机械通风和混合通风,并对三种通风形式设计应注意的问题进行了探讨。对于工业厂房通风的设计,必须结合实际进行综合考虑,正确选择通风方式,达到改善室内空气环境的目的。     

重庆市公共建筑通风季节设计通风量计算

公共建筑在过渡季节采用通风可带来可观的节能效果。过渡季节通风量难以计算导致工程设计无法有效应用该项技术。在现有公共建筑通风节能的理论研究基础上,结合重庆市《公共建筑节能65%设计标准》(报批稿)提供的室内设计负荷指标,提出了重庆市公共建筑通风季节设计通风量的计算方法,并针对重庆市典型建筑给出了通风季节设计通风量指标。     

Effects of the solid curtains on natural ventilation performance in a subway tunnel

Solid curtains can be installed in subway tunnels for the promotion of air ventilation in ventilation ducts in association with the piston effect caused by a running train. With an aim to analyze the effects of solid curtains on duct ventilation performance in a subway tunnel, the current study adopts the tunnel and subway train geometries which are exactly the same as those in a previous model tunnel experiment, but newly incorporates two ventilation ducts connected vertically to the tunnel ceiling and two solid curtains placed at an upstream position of a duct near the tunnel inlet and at a downstream position of another duct near the tunnel outlet, respectively. A three-dimensional CFD model adopting the dynamic layering method for tracking the motion of a train, which was validated against the reported model tunnel experiment in a previous study, is employed to predict the train-induced unsteady airflows in the subway tunnel and in the ducts. The numerical results reveal that the duct ventilation performance in a subway tunnel strongly depends on the operation of the solid curtains. The suction mass flow of the air through the duct near the tunnel inlet and the exhaust mass flow of the air through the duct near the tunnel outlet are increased considerably in the case with the solid curtains in comparison with those in the case without the solid curtains.