摘要
现代生活中,人们大约有80-90%的时间是在室内环境中度过的,室内的空气品质直接关乎人们的健康。在室内空气品质的研究中,室内微生物污染问题已经受到国内外学者广泛而高度的重视。非典型性肺炎(SARS)的爆发和人感染高致病性禽流感(H5N1型)、猪流感(H1N1型)病例的蔓延使人们对于微生物污染的关注程度上升到了前所未有的高度。大量资料及研究成果表明,携带病毒的微生物颗粒物可以在空气中进行传播,而建筑室内环境中的人们更容易接触和感染病菌。气流组织及送风气流形态对室内空气品质起着非常重要的影响,从气流组织和送风流态角度寻求快速排除和控制室内生物污染的方法和途径是通过空调系统控制室内生物污染要解决的首要问题。
本课题从理论计算入手室内生物污染问题,首先针对对人体健康威胁较大的1~2μm左右的微生物进行受力分析,结合气溶胶运动传播的理论计算模型和微生物特性,考察该粒径大小的微生物在室内环境中的气流跟随性。根据理论计算的结果,该粒径大小的微生物具有良好的气流跟随性。
本文提出了针对微生物气溶胶在室内扩散的浓度均匀分布和非均匀分布两种预测模型,并依照实验对其分别进行了计算验证和进一步修正。两种预测模型在室内生物污染扩散的评估和防控上可以起到比较良好的预测效果。
实验采用全尺寸模型结合三种风口形式对上送风、侧送风和下送风的三种气流组织形式的普通办公环境下室内的风速场进行测试,采用不均匀系数、空气特性分布指标ADPI评价不同气流形式下的气流均匀性,用自净时间和换气效率等指标对各形式的污染物去除能力进行评价,并用发菌实验模拟办公环境下致病菌携带者在伴随轻微咳嗽的呼吸作用产生示踪微生物气溶胶,通过合理的发生系统和采样方法,提出两项生物安全性指标对其他办公位置的浓度影响水平进行评价。通过综合分析比较,下送风气流组织形式对室内环境的传染病防控有较好的效果,而不同的风口形成的送风流态也影响着气流的分布。
最后,本文通过实验结果分析发现气流紊动度和沉降菌之间存在一定的关系,对此问题进行了初步的探索,所得到的数据对此问题的进一步研究具有一定参考价值。
In modern daily life, people spend nearly 80-90% of all time in indoor environment, so their health directly relate with the indoor air quality. Among the research on indoor air quality, the issue of indoor microbe contamination has received widely and highly respect of scholars both home and abroad. The outbreak of Severe Acute Respiratory Syndrome (SARS) and the spread of Bird Flu (H5N1) and Swine Influenza (H1N1) raise people’s attention on microbe contamination to an unprecedented level. Numerous data and results of research show that the bio-particles with virus can spread through air, which make people that staying in indoor environment more likely to contact and be infected by virus. Airflow pattern exerts a vital influence on indoor air quality. To find an effective way from the perspective of air distribution and flow pattern to quickly remove and control the bio-particles is the chief task on inhibiting the indoor microbe contamination by HVAC equipments.
The issue of indoor microbe contamination was initiated by theoretical calculation. Basing on the aerosol dispersion model and microbe characteristics, force analysis on the threatening bio-aerosols of 1~2μm was conducted in order to investigate their airflow following performance. According to the results, bio-aerosols of this particle size have good airflow following performance.
This article put forward the even distributed concentration predicting model and the uneven distributed concentration predicting model aiming at describing indoor bio-aerosol dispersion. They were validated and further modified respectively according to the experiment and would have good predicting effect on evaluating and defending the dispersion of indoor microbe contamination.
During the experiment test, up air supply, lateral air supply and under floor air supply combined with three types of air diffuser for common office environment were tested for their wind speed field in a full size chamber. Uneven Coefficient and ADPI were used to evaluate the evenness of these three air flow pattern, while Self-cleaning Time and Air Exchange Efficiency were used to appraise their ability of pollutant removing. Bacteria emanating experiment was conducted simulating the situation that a pathogen carrier generates bio-aerosols by breathing with slight cough. With reasonable emanating system and air sampling method, two bio-safety indexes were established to appraise the effect of bacteria source on other position under different airflow pattern. As results of comprehensive comparison, under floor air supply could have better effect of preventing infections in indoor environment and the airflow pattern formed by different air diffuser affects the airflow distribution.
Additionally, settling microbe was found to be related with air turbulence to a certain extent. The preliminary exploration embraces the reference value for further research on this subject.
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