不同示踪气体对房间通风量测试效果的探讨

示踪气体法是一种常用的室内通风量测试方法,目前已有多种测试模式及示踪气体种类。针对示踪气体的种类和测试条件的不同,来对测量通风量的测试效果进行实验研究分析。在设定标准工况下,通过多组工况的测试结果发现,在自然混合或机械混合的条件下,SF_6与CO_2作为示踪气体的测试效果差异不是很明显,当室内存在机械混合时,测试效果明显比自然混合状态要好很多,更接近于标准设定工况,此时SF_6在作为示踪气体测量通风量比CO_2的测试效果更佳。     

宁德市博物馆空调通风系统设计

介绍了宁德市博物馆工程的空调和通风系统设计。根据房间的使用功能,分区域设计了舒适性空调系统及工艺性空调系统。项目组合使用了变制冷剂流量多联机空调系统、风冷热泵空调系统和恒温恒湿空调系统等多种空调形式。为保证藏品安全,藏品库房设计了平时通风系统及气体灭火后通风系统。     

用示踪气体方法研究通风房间的空气龄

应用示踪气体测量得到了8种强制通风工况下实验小室各各测点处的浓度衰减曲线,并计算出各测点的空气龄,实验结果表明,示踪气体用于强制通风研究时实验可重复性较好,实验结果正确合理,测得的空气龄反映了房间各点空气的新鲜程度,也揭示了室内空气的流动形态。     

铁路变配电房屋暖通设计浅析

本文结合工程实际,对铁路变配电房屋通风、空调及消防设计中存在的若干问题进行了归纳、总结和探讨。主要包含电缆夹层通风及排水设计、电力设备机房正常及事故通风设计、空调设计、气体消防及灭火器设计等内容,提出个人观点及建议。对类似工程设计有一定的借鉴意义。     

外窗通风换气性能测试与流场模拟

采用示踪气体法(选取二氧化碳作为示踪气体)中的下降法(将一定量的示踪气体充入测试区域,在测试区域空气中示踪气体体积分数均匀后开始记录示踪气体体积分数的下降过程,通过记录数据可以计算出房间换气次数,从而得出待测外窗的通风换气性能),对上悬窗、内平开窗、外平推窗的通风换气性能进行测试。外平推窗的通风换气能力最强,上悬窗的通风换气能力最弱,内平开窗的通风换气能力居中。流体力学数值模拟结果表明,在测试期间,由于室内温度高于室外温度,在热压作用下,室内高温空气与室外低温空气在外平推窗的窗口处完成了换热。类似风帽的外平推窗,既促进了自然通风的进行,又避免了室外空气对室内气流组织的干扰。     

CO2示踪气体法测定室内新风计算方法研究

新风是评价室内微环境空气质量的重要指标之一,精确测定室内新风量在室内环境污染、通风空调和建筑节能等领域具有非常重要的意义.本文以CO2作为示踪气体,首先利用干冰升华和人体呼吸产生CO2这2种方法对室内新风进行测定,而后运用盒子模式,分别用非线性回归法、差分法、国标法和稳态法计算新风量,最后根据计算结果,讨论了不同计算方法的误差来源及优缺点.结果表明,CO2作为示踪气体测定新风量,不同的计算方法得到的结果差别较大：非线性回归法与其它方法相比最为精确,差分法其次,国标法计算的新风量偏低,而稳态法计算的新风量偏高.     

某人防指挥工程通风空调设计探讨

介绍了人防指挥工程通风空调及防化设计,阐述了通风空调系统计算及设计方法,指出通风空调系统的设计要点,并对通风空调系统方案及冷源选择、工程防化设计进行了详细分析,总结了人防指挥工程通风空调系统设计主要原则,为同类工程设计提供了一定的理论依据。     

建筑机电安装施工的管理要点

建筑机电安装工程施工包括电器工程、给排水工程、弱电工程、空调通风工程、防火卷闸、建筑灭火器配置、气体灭火等系统的施工,其施工质量的好坏将决定建筑使用质量的高低。     

置换通风在某车间空调改造中的应用

分析了原有工程空调系统存在的夏季室温降不下来、室内空气品质差等问题,改造设计中采用了水平置换通风空调系统,改造后空调系统运行良好。介绍了设计经验,认为置换通风空调方式在大空间工艺性空调中使用有其优越性,提出了发展这种空调方式尚需解决的一些问题。     

浅谈通风空调工程预算的编审工作

建筑通风空调工程造价在工程总造价中的占比越来越高,通风空调工程预算的编审工作直接影响着建筑工程的造价管理;通风空调工程预算的编审工作首先需要对工程图纸进行识读,了解通风空调工程的设计意图,熟悉通风空调工程的施工工艺、设计标准、工程概况、安装要求等信息;进行通风空调工程量计算时,需要具备相关通风空调工程的专业知识储备,详细了解通风空调工程量的计算规则;进行工程量清单的编制工作时,要熟知定额相关的基础资料。     

What is ventilation efficiency?

Various defintions of ventilation efficiency are examined. When using tracer gas techniques the definitions of a ventilation system's efficiency can be based on the slope of the tracer gas curves, or the ratio between concentrations, or the area under the curves. The consequences of these definitions are examined for a simple theoretical model. Experimental measurement on a test room are presented which show that sometimes very low ventilation efficiency can occur.     

System identification theory of the thermal network model and an application for multi-chamber airflow measurement

A comprehensive theory of multi-chamber air infiltration measurement using a single tracer gas is introduced from the general stand point of system identification. The thermal network model can be applied not only to the temperature transfer and diffusion system but also to the tracer gas transfer system. This model is formulated mathematically in a state equation. The coefficients in the state equation represent airflow rates of infiltration. Two theories for estimating these coefficients are deduced from the least square. These are batch and successive identification. Further, the evaluation method of estimation errors that has been so far insufficient is described. Finally, the accuracy and the practicality of the theory are confirmed by the actual measurement system and experiments.     

Ventilation performance measurement using constant concentration dosing strategy

Air change performances of an office with variable air volume (VAV) mechanical ventilation system and a domestic apartment with natural ventilation were evaluated using tracer gas techniques. Both the constant concentration and the decay method were utilized. Experimental results showed that the domestic apartment with opened windows performed better than the VAV system in terms of air-exchange efficiency, and maintained the highest air change rate. However, poor air change rate and air-exchange efficiency were resulted when the windows were closed in the home. By comparing the measurement results from the two tracer gas methods, it is found that the results obtained by the constant concentration dosing method were compatible with that obtained from the widely adopted tracer decay method. Several recommendations for conducting constant concentration dosing test were also discussed in this article.     

Experimental determination of air-flow in a naturally ventilated room using metabolic carbon dioxide

The paper reports extension to a naturally ventilated room of the metabolic CO₂ method for ventilation measurement. The analysis, which under some circumstances will also be relevant to tracer gas decay measurements, allows assessment of the individual incoming flows of air.     

传统换气次数测量方法的问题及其改进

以示踪气体下降法为例,通过实测和模拟分析,指出传统示踪气体测量换气次数方法存在的问题:因依据均匀混合理论,以拟合浓度曲线斜率的方法得到的各点换气次数基本相同,不能很好地反映各点的换气能力差异;同时,求取房间平均换气次数的方法存在数学原理上的不足。建议采用反映局部换气能力的指标——局部换气次数,并给出获得新的换气次数的方法。     

Dynamic evaluation of airflow rates for a variable air volume system serving an open-plan office

In a typical air-conditioned office, the thermal comfort and indoor air quality are sustained by delivering the amount of supply air with the correct proportion of outdoor air to the breathing zone. However, in a real office, it is not easy to measure these airflow rates supplied to space, especially when the space is served by a variable air volume (VAV) system. The most accurate method depends on what is being measured, the details of the building and types of ventilation system. The constant concentration tracer gas method as a means to determine ventilation system performance, however, this method becomes more complicated when the air, including the tracer gas is allowed to recirculate. An accurate measurement requires significant resource support in terms of instrumentation set up and also professional interpretation. This method deters regular monitoring of the performance of an airside systems by building managers, and hence the indoor environmental quality, in terms of thermal comfort and indoor air quality, may never be satisfactory. This paper proposes a space zone model for the calculation of all the airflow parameters based on tracer gas measurements, including flow rates of outdoor air, VAV supply, return space, return and exfiltration. Sulphur hexafluoride (SF6) and carbon dioxide (CO2) are used as tracer gases. After using both SF6 and CO2, the corresponding results provide a reference to justify the acceptability of using CO2 as the tracer gas. The validity of using CO2 has the significance that metabolic carbon dioxide can be used as a means to evaluate real time airflow rates. This approach provides a practical protocol for building managers to evaluate the performance of airside systems.     

高压驱动下非均匀介质内气体输运数值模拟

通过利用商用软件,对地下腔室内的示踪气体在高压驱动下向非均匀围岩介质的输运进行了数值模拟,并分析了影响示踪气体输运行为的主要因素.结果表明,理想的均匀介质可以较好地包容示踪气体,而在实际的非均匀介质内示踪气体更倾向于以较高的浓度沿介质局部薄弱环节向外输运;腔室外的坑道中,采用堵塞段和空段的设计有利于阻止示踪气体向外输运...     

A field validation of a roof-top dispersion formula in an urban centre

A tracer experiment of gaseous dispersion for a flush roof-top vent was carried out for ten months. The concentration of the tracer gas in front of the fresh air-intake duct, installed on the same roof, was monitored.The medium-rise building is among a group of buildings of similar height. By using Wilson's semi-empirical formula, with one modification to suit the field measurement problem of representative wind velocity within a city centre, it was shown that a conservative estimate of dilution factors was obtained.     

Air Change Effectiveness Measurements in Two Modern Office Buildings

Local age of air and air change effectiveness were determined in two office buildings using tracer gas techniques to study the applicability of the associated measurement procedures in mechanically ventilated office buildings. Measurement issues examined include the establishment of a uniform tracer gas concentration at the start of the test and the relationship of ventilation system configuration and system operation to the test procedure. Air change effectiveness was determined at locations in the occupied space based on the local age of air at that location and the age of air in the corresponding ventilation system return duct. Values of the air change effectiveness in the occupied space were generally close to one, which is consistent with good mixing of the Ventilation air within the occupied space. Deviations from 1.0, on the order of 10%, did occur, but given the limited experience with these measurement procedures in the field it is not clear whether these deviations are significant. These tests provide data on air change effectiveness to supplement the limited database on mechanically ventilated office buildings in the US. In addition, the experience obtained with the measurement procedures will assist in the development of a standardized approach to measuring air change effectiveness in the field.     

VLCC修船通风气流组织的研究

从理论上分析了气流组织对通风效果的影响，根据大型原油运输船（ＶＬＣＣ）修船通风的特点，提出了一种新式的气流组织模型及其相应的末端装置，并通过利用示踪气体法测定通风效率，对气流组织作出了定量评价。