Numerical simulation and analysis for indoor air quality in different ventilation

Indoor air environment includes indoor thermal environment and air quality, and a reasonable ventilation provides guarantee for a good indoor environment. A numerical study of the indoor environment in different ventilation is presented in this paper. The External Energy Saving Lab of the WenYuan Building was selected for this purpose, and its indoor air quality and thermal performance in the typical summer climate were simulated. For the numerical simulation, the techniques of Fluent Air-pak was adopted to establish the physical and numerical model of lab. A attention is given to the velocity field and the distribution of pollutant concentration, followed by a discussion of two ventilation modes (displacement ventilation and up-in and up-out ventilation). By comparison, it is found that the Displacement ventilation in improving indoor air quality is obviously superior to the traditional up-in and up-out ventilation.

Optimising multi-vent module-based adaptive ventilation using a novel parameter for improved indoor air quality and health protection

As infectious respiratory diseases are highly transmissible through the air,researchers have improved traditional total volume air distribution systems to reduce infection risk.Multi-vent module-based adaptive ventilation(MAV)is a novel ventilation type that facilitates the switching of inlets and outlets to suit different indoor scenarios without changing ductwork layout.However,little research has evaluated MAV module sizing and air velocity selection,both related to MAV system efficiency in removing contaminants and the corresponding level of protection for occupants in the ventilated room.Therefore,the module-source offset ratio(MSOR)is proposed,based on the MAV module size and its distance from an infected occupant,to inform selection of optimal MAV module parameters.Computational fluid dynamics simulations illustrated contaminant distribution in a two-person MAV equipped office.Discrete phase particles modelled respiratory contaminants from the infected occupant,and contaminant concentration distributions were compared under four MAV air distribution layouts,three air velocities,and three module sizes considered using the MsOR.Results indicate that lower air velocities favour rising contaminant levels,provided the ventilation rate is met.Optimal contaminant discharge can be achieved when the line of outlets is located directly above the infected occupant.Using this parameter to guide MAV system design,85.7% of contaminants may be rendered harmless to the human body within 120 s using the default air vent layout.A more appropriate supply air velocity and air vent layout increases this value to 91.4%.These results are expected to inform the deployment of MAV systems to reduce airborne infection risk.

Field measurement of the impact of natural ventilation and portable air cleaners on indoor air quality in three occupant states

Natural ventilation(NV)has been considered a simple and effective method of ventilation.However,the intro-duction of NV does not achieve better indoor air quality(IAQ)when the outdoor atmospheric environment is polluted.Therefore,portable air cleaners(PACs)are increasing in use in recent years,but their effectiveness is highly dependent on the residents’habits.A typical residence in Xi’an,China was selected to examine the effects of the use of NV alone and the use of NV and PACs together on IAQ in the three occupant states,i.e.,unoc-cupied,sleeping and leisure.Parameters,such as temperature,relative humidity,CO_(2),and PM_(2.5)concentration were measured when changing the window opening and the position of the PAC.The results showed that in the unoccupied state,opening the inner door can promote a more uniform thermal and humid environment.In the sleeping state,the I/O ratio of the PM_(2.5)concentration was the lowest when the window opening of the bedroom was 1/2 or 3/4,with a mean value of 0.3.In the leisure state,only using NV,when the purification rate reaches 90%,the mean purification time of each window opening in the living room is 87.5 min.The mean purification time was reduced to 25 min when both NV and PAC were used.The on-site purification efficiencies were 91.0%and 94.5%,when the window opening was 1/2(i.e.,the PAC was placed in the center of the room)and 3/4(i.e.,the PAC was placed away from the outer window),respectively.

Efficacy of coupling heat recovery ventilation and fan coil systems in improving the indoor air quality and thermal comfort condition

Mechanical Ventilation with Heat Recovery(MVHR)systems are gaining increasing interest in buildings with low energy demand,for improvement of the Indoor Air Quality(IAQ)and reduction of the ventilation energy loss.In retrofitted buildings,MVHRs are often integrated with an additional air heater to cover space heating demand.Hence,evaluation of the interactions between MVHR and heat emitter,and their effects on indoor airflow characteristics is of significant importance.The present study aims to investigate effects of a combined MVHR-fan-coil system in heating mode on IAQ and thermal comfort parameters inside a retrofitted room,by means of a computational fluid dynamic(CFD)code.The proposed CFD model is validated by comparing the numerical results with experimental data.The results yielded by numerical simulations allow evaluating the indoor environmental quality characteristics as well as addressing the MVHR and fan coil interactions.The results indicate that the airflow discharged from the fan coil could have a significant impact on the age of the air;while it provides a desirable thermal comfort condition within the room,it may hinder to some extent delivery of the fresh air to the occupied zone due to creation of counterflow fields.Furthermore,it is shown that although increasing the fan speed(ON mode)would slightly enhance the air change efficiency,the OFF mode yields not only a better distribution of the fresh air but also a higher ventilation efficiency than when fan coil operates.

Indoor Air Quality Measurement with the Installation of a Rooftop Turbine Ventilator

The present paper presents a numerical analysis of the difference in comfort level inside a room of a residential building when roof top turbine ventilator is installed. This analysis simulates various comfort factors which includes the indoor air movement, room temperature, Predicted Mean Vote (PMV) and Predicted Percentage of Dissatisfied (PPD). Various test cases of ventilator exhaust rate were examined. The results showed that general comfort satisfying international standards in building can be achieved. This study also presents a qualitative and quantitative study of indoor air temperature and overall indoor air flow pattern. A promising conclusion that can be drawn from this study is that wind driven ventilators can play an important role in the design of a cost effective and energy efficient ventilation system inside a building.

New and innovative wind catcher designs to improve indoor air quality in buildings

Wind catchers used in various countries in Middle East and North Africa in order to improve indoor air environ-ment and to reduce reliance on cooling load.However,nowadays they are used across the globe with modern shapes and advanced techniques.The study focuses on investigating new and innovative shapes of wind catch-ers to improve air speed indoors which will elevate indoor comfort and air quality in buildings.The study used computer modeling CFD and a real model experiment to conduct the study.The study highlighted that curved shapes have highest pattern of wind speed driven,especially curved shape with double inlets.In addition,the study showed that octagon shape has the lowest pattern of wind speed driven because of its various sides which prevent air to flow easily inside the tunnel.

Experimental study on indoor environment improvement in toll booth by personalized ventilation technology

The necessity and feasibility of the use of the personalized ventilation（PV）technology in a toll booth is described.First,the indoor environment of the toll booth equipped with a PV system is analyzed.Based on the analysis results,a set of equipment for controlling the indoor air quality（IAQ）of the toll booth is devised.Then,a full-scale model of the toll booth is set up in the laboratory.The airflow organization,the optimum operation parameters,and the restraint effects of the PV system on pollution are also experimentally studied.The experimental results on the air supply characteristics show that the PV system can effectively reduce the air age,improve the ventilation efficiency,and enhance the comfort and acceptability of human beings.In addition,this system plays a significant role in preventing pollution.

基于CFD模拟的办公室自然通风方案研究

随着人们对居住环境的要求逐步提高,在节能的前提下进行通风是改善室内环境的有效措施,对建筑物选择合理通风方式是保证通风效果的重要条件。自然通风作为一种广泛应用的通风方式,不消耗能量而能改善室内环境,对其方案的探索和优化具有较好意义。以某办公室的自然通风方案为研究对象,采用敏感性分析法定量分析相关因素变化对通风效果的影响。按不同变化比例设定不同的工况,以风速和空气龄为评价指标,采用CFD技术模拟窗户的开口面积和窗台高度变化时的室内风环境的参数分布,从而分析窗户开口面积以及窗台高度对自然通风的影响,合理的自然通风可以满足人们对室内舒适度的要求,实现人与自然和谐共生。研究结果为办公区域实现良好的自然通风提供理论参考,有利于自然通风方式的推广应用。

深凹立面建筑房间自然通风效果及污染物浓度分布

以西安地区某主导风向为侧向来风的深凹立面建筑房间为研究对象,通过过渡场模型对室外场到室内场进行了多尺度CFD模拟,研究了不同开窗方式下的室内空气质量。结果显示:全开窗对于排出室内产生的污染物有较好效果,但是对于室外污染物的抵抗能力不如单开平立面窗;当室内污染物集中于某个单个房间时,开窗形成的对流通风会造成其他无污染源房间内的污染物浓度增大;当污染物分散在各个房间时,对流通风则可以有效降低各房间污染物浓度,降低幅度约为50%;单开平立面窗能有效杜绝室外污染物进入室内,而增大出风口是排出室内污染物的最好方法。

基于CFD的置换通风空调房间数值模拟

以下送风置换通风空调房间为例,采用计算流体力学CFD软件,运用两方程湍流模型模拟置换通风房间的温度场和污染物浓度场,揭示了置换通风在提高人体的热舒适性、改善室内空气品质、节能等方面的作用。模拟结果对改善室内空气品质具有指导意义。

基于Airpak的室内空气品质分析

随着人们生活水平的提高,人们对室内空气品质的要求越来越高,室内空气品质的好坏与人们的健康、工作效率息息相关。用Airpak软件模拟计算了某空调办公室在开门和不开门时的气流组织,通过对计算结果的分析,可以看出不同的气流组织对空气品质的影响,为合理改善和提高室内空气品质提供了参考。

基于双碳目标下居住建筑自然通风设计研究

建筑若存在夏季通风不畅的现象,则会增加空调能耗。以河南科技大学家属院某户为研究对象,利用CFD数值模拟软件对室内风速和空气龄进行分析,并对室内现有风环境存在的问题提出居住建筑自然通风设计方案。结果表明:通过优化建筑平面和通风构件的方式增加室内热压通风,优化方案室内平均风速增加了0.12 m/s,提升了室内风舒适度;在自然通风条件下对7月空调制冷能耗进行模拟分析,优化方案中空调制冷能耗降低了4.1%。

空调通风运行策略对室内空气污染物浓度影响的研究

室内空气环境与建筑使用者的健康息息相关。空调通风作为可辅助净化排除污染物的手段,如何采用有效的系统运行策略值得探讨。现对某新装修办公环境进行试验,应用多组空调通风运行策略测试其对室内污染物PM_(2.5)、HCHO、TVOC浓度的影响,以探究各空气处理措施的稀释净化效果。研究发现,运行适宜的空调通风策略可有效排除室内污染物,且各空气处理措施对PM_(2.5)、HCHO、TVOC的处理效果不同,可结合需求、污染源特性、系统设计针对性处理。

通风、空调设计中的CFD技术

阐述了CFD(计算流体动力学)技术在通风、空调设计中的应用情况,说明了其使用步骤、方法,提出了CFD应用方面存在的问题及今后发展前景。

Airpak软件在气流组织领域的应用

Airpak是用于模拟室内气流组织的CFD专用软件,用于工程领域和科学研究。介绍了Airpak软件的基本特点,并用该软件模拟了某办公室的气流组织和热舒适性,为改善室内热环境提供参考。

脉动送风对大空间建筑室内污染物通风效率和流动分布的影响

为提高大空间建筑室内的空气品质,将脉动送风应用于大空间喷口送风中,以CO_(2)为示踪气体,基于实验分析喷口送风的流场特征,并以校核后的计算流体力学(CFD)模拟结果,研究脉动送风在不同振幅和周期下对大空间建筑室内污染物通风效率和流动分布的影响。研究结果表明:脉动送风的CO_(2)浓度衰减曲线呈现波动下降的趋势,大周期脉动送风的通风效率低于定风速送风;与定风速送风相比,脉动送风可有效降低室内污染物的极大值,增强新风对室内污染物的稀释范围,喷口下方和排风口附近的污染物浓度有明显的降低;在大空间喷口送风建筑中,推荐随时间波动变化快、幅度小的小周期小振幅的脉动送风。该研究可为实际大空间通风系统优化设计提供参考。

On the optimisation of age of the air in the breathing zone of floor heating systems:The role of ventilation design

For a mechanically ventilated space,the nominal age of the air can be obtained by the reciprocal of the air change rate.However,values of the local mean age of the air in practice may differ to some extent from the nominal one since the nominal time constant employs as reference the theoretical optimum model.This discrepancy could become more prominent in spaces conditioning with both ventilation and heating system where the indoor air pattern is affected by turbulent mixed convection flow.Given importance of knowledge on the distribution of age of the air in these spaces,the present study provides insights on how ventilation design in floor heating systems can optimise the delivery of fresh air into the breathing zone.In this context,by establishing a computational fluid dynamic(CFD)model validated against experimental data,the local mean age of the air as well as the indoor air quality(IAQ)indices in the breathing zone of the floor heating system are examined under different ventilation modes.Six different ventilation scenarios are regarded in order to find the optimal ventilation design in terms of the delivery of the fresh air and ventilation effectiveness in occupied space.Furthermore,the integrated effects of the floor temperature and inlet supply temperature along with the ventilation design on the distribution of local age of the air are addressed.The obtained results indicate that the up-supply ventilation strategy is more efficient than down-supply one in the ventilation effectiveness and delivery of fresh air into the breathing zone.Moreover,it is shown that the mean age of the air in the breathing zone of the up-supply ventilation increases with increment of the Ri(Richardson number),whereas an increase in Ri improves the delivery of fresh air in down-supply mode.For a given floor temperature,the similar trend is also observed in the variation of age of the air with the characteristic temperature of supply inlet,namely the temperature difference between inlet supply and surrounding walls.

北方滨海地区自然通风乒乓球馆冬季风热环境调查研究

文章通过现场测试及主观问卷调查,分析了初冬非采暖期青岛市某高校乒乓球馆在自然通风条件下运动人群在热舒适、室内空气品质、风速干扰性三方面的主观感受。研究发现:与非运动人群相比,运动人群感觉偏暖,可接受的舒适温度下限更低;运动人群可接受的CO_(2)浓度更高,但同时对CO_(2)浓度的变化表现出更高的敏感度;虽然乒乓球馆室内平均风速仅为0.09m/s,但仍有65.67%的运动者认为风速干扰较大。乒乓球资深运动人群有习惯性关窗的行为,避免运动区域的风场干扰是乒乓球馆中引入自然通风亟须解决的首要问题。

基于CFD数值模拟的图书馆门厅中庭室内热环境分析与优化

门厅、走道等过渡区域高大空间空调制冷系统,如何获得舒适的夏季室内环境,满足节能要求,是一个难题。通过CFD软件模拟某大学图书馆门厅中庭的温度场和气流分布,更直观地呈现室内空调环境,分析计算结果,提出结论和针对性建议,以提高室内舒适度。对类似工程中高大空间夏季空调系统设计有一定的参考价值。

浅谈车内新风系统

针对车内空气污染情况做了简要的介绍,针对新风系统的开发特点做了一定的阐述,同时罗列了目前市面上已应用车内新风系统的各类功能,包括定时通风、高温保护、解锁新风、降窗通风和极速通风。浅要分析了各项新风系统的应用特点和适用场景,为优化车内空气质量提供一定的参考和借鉴,为后续新模式新场景化的新风系统开发提供思路。