Heating,ventilation and air conditioning system modelling

Heating, ventilation and air conditioning modelling methods, for large scale, spatially dispersed systems are considered. Existing techniques are discussed and proposals for the application of novel analysis approaches are outlined. The use of distributed–lumped parameter procedures enabling the incorporation of the relatively concentrated and significantly dispersed, system element characteristics, is advocated. A dynamic model for a heating, ventilation and air conditioning system comprising inlet and exhaust fans, with air recirculation, heating/cooling and filtration units is presented. Pressure, airflow and temperature predictions within the system are computed following input, disturbance changes and purging operations. The generalised modelling advancements adopted and the applicability of the model for heating, ventilation and air conditioning system simulation, re-configuration and diagnostics is emphasised. The employment of the model for automatic, multivariable controller design purposes is commented upon.     

The reliability and availability of heating,ventilation and air conditioning systems

Reliability theory has been applied to building HVAC facilities. In order to do this, the type of probability distribution for “mean time to repair”, “mean time between failures” and “decision time” was first studied, and it has been shown that the log-normal type of distribution applies here. This was evaluated from a large amount of data collected from buildings belonging to seven large real estate operators. Based on those results and assumptions, a “model” using standard reliability theory equations was deducted. The model has been used in a study of the seven large real estate operators.

• •The study shows that the model can give a good picture of the reliability and availability of HVAC systems.

The study also gave interesting results about the status of the studied HVAC systems:

• •the operational availability is high, almost 100%;
• •the decision time of the maintenance staff is large compared to repair time;
• •the system reliability depends strongly on the technical solutions and the number of components; and
• •the functional availability of the systems was low, partly because of malfunction of the ventilation systems. (Note: this depends, naturally, on the function criteria.)

Values of functional availability depend strongly on the function criteria. In this study, criteria connected to the actual buildings were used and no evaluation of the criteria themselves was made. The measurements were taken from different buildings both connected and not connected to the seven studied organisation.     

蒸发冷却与毛细管辐射供冷复合空调系统实验研究

基于蒸发冷却辐射供冷复合空调系统工程设计方法,对蒸发冷却和辐射供冷承担的负荷进行了分配,并于复合空调系统实验台上用实验的方法对其夏季工况的新风系统、高温冷水系统和室内热湿环境进行了测试.结果表明,在中湿度地区,当供水温度19℃、置换送风温度17℃时,0.1～1.1 m高度最大温差小于2℃,1.1 m高度室内温度26～26.5℃,0.1～1.1 m高度室内温度梯度小于2℃/m,1.1～2.7 m高度室内温度梯度小于1℃/m,室内空气相对湿度为53.3%～65.4%,温、湿度均满足热舒适性要求.辐射板表面平均温度为21.75～21.9℃,始终高于室内空气露点温度,避免了结露的可能性.     

谈供热通风空调设计中常见问题

简要介绍了供热通风空调设计及其设计要点,分析了设计中的常见问题,并从完善暖通空调系统设计、落实暖通空调大温差系统设计、优化节能与暖通空调蓄冷系统设计等方面,提出了相关解决策略,以彻底优化空调设计水平。     

Effectiveness of heating, ventilation and air conditioning system with HEPA filter unit on indoor air quality and asthmatic children's health

Poor indoor air quality has been linked to the exacerbation of asthma symptoms in children. Because people spend most of their time indoors, improving indoor air quality may provide some relief to asthma sufferers. A study was conducted to assess whether operating an air cleaning/ventilating unit (HEPAiRx^®) in a child's bedroom can improve his/her respiratory health. Thirty children diagnosed with asthma were randomly split into two groups. For the first six weeks, group A had the air cleaning/ventilating unit (HEPAiRx^®) running in the bedrooms of the participants and group B did not; for the second six weeks, both groups had the cleaners running in the bedrooms; and, for the final six weeks, group A turned the cleaners off and group B kept theirs running. Indoor air quality parameters, including temperature, relative humidity, particulate matter (PM 0.5–10 μm), carbon monoxide, carbon dioxide and total volatile organic compound (TVOC) concentrations, were monitored in each bedroom using an AirAdvice indoor air quality multi-meter. As a measure of pulmonary inflammation, exhaled breath condensate (EBC) was collected every sixth day and analyzed for nitrate and pH. Peak expiratory flow (PEF) was also measured. PM and TVOC concentrations decreased with operation of the HEPAiRx an average of 72% and 59%, respectively. The EBC nitrate concentrations decreased significantly and the EBC pH and PEF values increased significantly with operation of the unit (p < 0.001 when comparing on/off sample means). These results indicate that air cleaning in combination with ventilation can effectively reduce symptoms for asthma sufferers.     

暖通空调双语教学实践探索

文中介绍了暖通空调双语教学的教学目的和意义,结合西安工程大学暖通空调双语教学实践,总结了课程资源体系中师资、教材以及多媒体课件的建设方法,探讨了暖通空调双语教学的课堂实践模式。教学实践表明,暖通空调双语教学可以培养学生学习兴趣,提高以英语为工具获取专业知识的能力,应加强教材和题库建设,以优化教学质量。     

地铁通风空调集成闭式系统风道设计浅析

从系统的特点、风道的尺寸和位置、风井的布置、气流组织等方面详细阐述了通风空调集成闭式系统的风道设计,并对施工中的注意事项进行了总结.     

暖通空调节能设计分析

分析了建筑环境与暖通空调能耗之间的关系,探讨了室内环境,围护结构,建筑规化设计对暖通空调负荷及节能的影响,并阐述了暖通空调领域节能的途径与方法,以期促进暖通空调节能设计的进展。     

基于军校任职教育中通风空调课程教学模式的探讨

文章根据教学对象多元化的特点界定教学目标,科学组织教学内容;灵活应用多种教学模式,如直接讲授模式、探究模式、因果模式、课堂讨论模式、合作学习模式、PBL模式,打造"情景的课堂"、"思辩的课堂"、"自主的课堂"、"开放的课堂"、"合作的课堂";同时建立密切结合学习进程的评价体系,进一步促进课程教学的有效性,构建了军校任职教育通风空调课程的有效教学模式。     

Identification of SARS-CoV-2 RNA in healthcare heating,ventilation, and air conditioning units

Evidence continues to grow supporting the aerosol transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). To assess the potential role of heating, ventilation, and air conditioning (HVAC) systems in airborne viral transmission, this study sought to determine the viral presence, if any, on air handling units in a healthcare setting where coronavirus disease 2019 (COVID-19) patients were being treated. The presence of SARS-CoV-2 RNA was detected in approximately 25% of samples taken from ten different locations in multiple air handlers. While samples were not evaluated for viral infectivity, the presence of viral RNA in air handlers raises the possibility that viral particles can enter and travel within the air handling system of a hospital, from room return air through high-efficiency MERV-15 filters and into supply air ducts. Although no known transmission events were determined to be associated with these specimens, the findings suggest the potential for HVAC systems to facilitate transfer of virions to locations remote from areas where infected persons reside. These results are important within and outside of healthcare settings and may present necessary guidance for building operators of facilities that are not equipped with high-efficiency filtration. Furthermore, the identification of SARS-CoV-2 in HVAC components indicates the potential utility as an indoor environmental surveillance location.     

供冷供暖供生活热水蒸发式冷凝空调系统的应用

针对目前供冷供暖供生活热水系统的热水温度达不到60℃,且系统能效较低的现状,提出了该空调系统作为解决方案,根据能源梯级利用原则,在不提高冷凝温度的同时回收了部分潜热及全部显热。介绍了热回收系统蓄热阶段、用热阶段和不用热阶段的工作模式。结合某工程实例,介绍了机组的详细参数以及热回收热水系统的设计计算,供冷期的运行分析结果表明,在不同负荷率工况下,热回收量均大于生活热水用热量,即在供冷期,可以免费提供生活热水。     

冬季空调供冷及空调水系统制式选择

在我国北方地区,部分公共建筑冬季室内温度过高的问题比较突出,这个问题是伴随着建筑规模越来越大和围护结构保温密闭性能越来越好而出现的。两管制空调水系统结合新风供冷和四管制空调水系统是实现冬季同时供热供冷的2种常见系统形式。详细论证了两管制结合新风供冷的可行性和局限性,以及四管制空调水系统的优缺点,提出了这2种系统形式各自的适用范围。     

大型客车发动机冷却系统与除湿供冷联用的空调系统

介绍了除湿供冷系统的工作原理，探讨了大型客车发动机冷却系统与除湿供冷联用的空调系统的组合形式和工作过程，根据国外资料分析了此项技术的技术经济性能以及在我国的应用前景。     

交通岗亭间接水蒸发开式空调系统

将间接式水蒸发空调系统用于交通岗亭中 ,分析了系统的热力参数 ,建立了系统的数学模型 ,分析一次气流进口相对湿度及换热器效率对系统加湿量的影响 ,并给出计算例子。     

暖通空调设计中常见问题的探讨

针对目前暖通工程设计中审图部门提出的一些常见问题，对照设计规范、规定及标准，列举了在系统设计、设备选型、管道布置等几个方面应注意的问题，以期提高暖通工程的设计质量。     

Modeling and designing heating and ventilation system with underfloor air distribution

This paper presents analytical and numerical predictions of heat and pressure drop characteristics of a floor with the ventilating ducts. The experimental results are used to validate the models. An acceptable accuracy between the computational simulation and measured performance data is obtained. The analytical method is implemented as the computer program, which is a useful and accurate tool in designing heating system with underfloor air distribution. The bar chart of the design process and the diagrams for sizing the specific system of underfloor ventilation ducts are presented in the paper, too.     

新广州站无组织通风对空调系统负荷的影响

利用ContamW软件计算了新广州火车站空调季无组织通风的路径及通风量,用DeST软件分析了无组织通风对房间冷负荷的影响,并提出了相应的改进措施.     

蒸发冷却半集中式空调系统的控制方案

介绍了蒸发冷却半集中式空调系统的流程。基于该系统不同季节的运行模式,设计了自控方案,以保证该空调系统的安全性和节能性。详细介绍了控制内容和硬件配置。利用组态软件完成PC机与PLC之间的通讯,实现了系统集中控制、数据记录和打印等功能,能为现场设备维护人员提供详细的资料,简化操作、维护工作。工程应用实践表明,该自控系统运行稳定,能达到预期效果。     

空调冷(热)源的寿命周期价值分析

以某一集中空调工程为例,针对其冷(热)源系统的几个方案进行了寿命周期价值分析,以选择最佳的冷(热)源方案。     

太阳能供暖空调系统设计探讨

阐述了太阳能集热器的选择和布置、太阳能供暖空调系统的两种形式.结合工程实例,描述了太阳能应用于地板辐射供暖和热水型溴化锂吸收式制冷的设计方案及系统控制要求.