侧墙上置风口置换通风系统性能的实验研究

对侧墙上置风口置换通风在不同负荷率下进行夏季工况,过渡季节工况,冬季内区工况的系统性能进行实验研究,得出此种通风方式下送风口的速度分布,室内的温度分布,0.1m处的风速等实验数据。通过分析实验数据得出,侧墙上置风口置换通风在满足室内热舒适性的前提下,能够提高房间的负荷承担能力,与混合通风相比能够得出较高的通风效率;另外,阶梯形的风口较普通的送风口能较少地卷吸上区品质差的空气,能更好地满足侧墙上置置换通风的风口特性要求。     

风口侧上置置换通风的热舒适性实验研究

以小型办公室为实验模型,采用了5组对比工况进行了实验,并将实验值与模拟值进行了比较,结果二者吻合较好。分析了侧墙上置风口置换通风的热舒适性。结果表明风口侧上置置换通风在各设计工况下,其负荷承担能力要大于传统置换通风,并且不论是吹风感、吹风温度还是室内头脚垂直温差都满足人体热舒适。这也证实风口上置置换通风与传统置换通风一样,可以在室内形成良好的热力分层现象,并且其能很好地满足人体的热舒适性需求,具有置换通风系统的特性。     

风口上置置换通风及风口选型实验研究

提出了风口上置的置换通风方案，并给出此种方案的特点和上置式置换通风风口的要求，推导了风口出风速度呈阶梯状分布的射流特性公式。以喷口为基础进行实验，筛选出了满足条件的风口型式，并给出了出风速度呈阶梯状分布时圆形射流轴线速度衰减公式。     

上置风口置换通风方式的讨论

针对传统置换通风系统中存在的不足,提出了上置风口置换通风方式,介绍了该通风方式的工作原理,并将其与传统置换通风进行了比较分析,指出上置风口置换通风具有热舒适性好、高效节能的特性,发展前景广阔。     

基于方柱面贴附空气幕式送风模式气流组织特性研究

提出了一种适用于大空间建筑通风空调系统的方柱面贴附空气幕式送风模式。采用数值模拟方法,研究了多柱组合送风模式下各柱体间气流组织特性的对称性,分析了送风速度、温度和热流密度3个特性参数对房间速度场和温度场分布的影响,并对工作区人员热舒适性进行了评价。研究表明,该送风模式能够在房间下部工作区形成类似于置换通风的空气湖状速度及温度分布,人员热舒适性较强,承担的室内负荷较传统置换通风模式大,而且上置送风口便于布置,是一种通风效率较高、工作区空气品质较好的气流组织形式。     

侧墙上置送风口置换通风流场及通风效果评价

针对设置侧墙上置送风口置换通风系统的房间,采用CFD软件对室内空气速度场、温度场进行模拟。根据模拟结果,分析贴附射流、冲击射流的发展过程,评价侧墙上置送风口置换通风系统的通风效果。     

送风口间距对层式通风热舒适性能影响的研究

本文使用标准k-ε湍流模型对层式通风房间进行模拟计算,并对其进行实验验证,结合速度场,温度场及热舒适性分析,研究了六种不同送风风口间距层式通风性能的影响.研究结果表明:层式通风房间送风风口间距会影响多股送风射流间的相互作用,从而影响室内的气流组织分布,导致工作区内不同区域的热舒适差异.随着风口间距的增加,工作区的预测评价热感觉投票PMV和有效通风温度EDTS先减少后增加呈二次函数关系,即工作区内热舒适性先逐渐改善后降低.950mm风口间距下的PMV和EDTS绝对值均最小,工作区最接近于热中性环境,故可作为最佳送风口间距.     

工业厂房置换通风两种送风口形式的比较

对采用置换通风的厂房在不同送风口形式下的气流组织特性进行数值模拟,分析送风量对厂房内温度场、速度场、污染物浓度场的影响。结果表明:矩形送风口在下部单向流动区会产生较大温差,造成人体不舒适感,在上部混合区温度分布均匀,送风速度与平均温度呈负线性相关。圆柱形送风筒能较好满足舒适要求,在热源附近温度梯度大,送风速度较大的情况下室内温度分布趋于平稳,较矩形送风口除热效果更好。圆柱形送风筒排污效果更稳定,30分钟左右甲醛浓度分布均匀。矩形进料口具有较高的污染物去除效率,可广泛用于医院等高空气洁净度较高的工厂。     

毛细管辐射空调加置换通风系统在夏热冬冷地区应用可行性分析

本文分析了毛细管辐射空调加置换通风复合空调系统在夏热冬冷地区应用的可行性。并且对复合空调系统不同的送风方式进行数值模拟,得出在空调房间上置送风口的送风方式可以使空调房间气流更均匀的结论,同时这种送风方式也能更好地避免结露现象的产生。     

置换通风的热压驱动增益模式可行性研究

通过对传统下置置换通风系统特点的研究,提出了一种新的下置置换通风空调系统——由太阳能烟囱为新系统中送风提供热压动力,使送风具有传统下置置换通风系统的送风特点,室内工作区具有良好的空气品质。同时通过数值模拟的方法分析并比较了传统下置置换通风系统与新系统。结果表明:该系统能解决传统置换通风不舒适的吹风感和竖直温差大的问题;相对于传统下置置换通风,新系统还具备节能和环保特性;烟囱具有良好的自我调节性能。     

办公建筑中旋流风口地板送风系统的设计及实验研究

基于地板送风与置换通风原理的相似性,参考办公室中置换通风的设计方法,结合旋流风口地板送风系统的特性,提出旋流风口地板送风系统的设计方法。通过实验对设计方法进行了验证,并对室内热舒适性进行了评价。     

Floor-supply displacement ventilation for workshops

This paper reported the investigation of the performance of floor-supply displacement ventilation with swirl diffusers or perforated panels under a high cooling load (nearly 90 W/m²). The experiment was carried out in a full-scale environmental chamber to obtain reliable data on the floor-supply displacement ventilation for the validation of a computational-fluid-dynamics (CFD) program. Numerical simulations using CFD program were to evaluate the performance of the system for a large workshop. The impacts of several parameters, such as the air change rate, number of diffusers, diffuser location, occupant location, furniture arrangement, partition location, and arrangement of exhausts, on the indoor environment were investigated based on the thermal comfort level and indoor air quality. This study ranked the impacts of these parameters on indoor environment.     

Development of ventilation design strategy for effective removal of pollutant in the isolation room of a hospital

This paper investigates the airflow and pollutant distribution patterns in a “negative pressure” isolation room by means of objective measurement and computational fluid dynamics (CFD) modeling based on three ventilation strategies. An effective ventilation system is crucial to protect doctors, nurses and other health-care workers from patients with infectious disease. In the preliminary study with Strategy 1, the isolation room has two air supply diffusers and two extract grilles mounted on the ceiling. Strategy 2 retains the air supply diffusers in Strategy 1 but relocates the two extract grilles to the wall behind the bed at 0.3 m above the floor level. Strategy 3 has the same layout as Strategy 2 except the ceiling diffusers are replaced by supply grilles and relocated closer to the wall behind the bed.     

Modelling and simulation of the near-wall velocity of a turbulent ceiling attached plane jet after its impingement with the corner

At present, ceiling-mounted diffusers are very popular for indoor air distribution, particularly in offices, owing to greater efficiency in the distribution of the air supply and a more comfortable indoor environment. The objective of this study is to construct an effective model to design the indoor airflow of an attached plane jet after its impingement with the corner in a room. In this study, a full-scale test facility was set up to obtain detailed experimental data. One commercial CFD tool, CFX 11.0, was used to simulate the air velocity distribution of an attached plane air jet bounded by the ceiling and an insulated wall. One semi-empirical model was also constructed to predict the impingement jet velocity. The results show that bout the semi-empirical model and CFX 11.0 were able to predict the maximum velocity of an impinging jet at low Reynolds numbers, 1000 and 2000, with an inaccuracy of ±11%. However, the semi-empirical model could be more conveniently used to predict the maximum jet velocity decay after its impingement the corner in a room than CFD simulation in terms of accuracy and the time required to design the indoor airflow pattern.     

武汉某剧院空调气流组织分析

结合现场所测的数据对观众厅部分现有空调喷口送风的气流组织做简要的计算和分析,并简要计算了设计工况下速度分布和温度分布,得出该送风形式下的池座和楼座的气流组织存在诸多问题,进而针对池座提出用旋流风口代替球形喷口垂直下送,楼座则建议改为座椅下送风。     

送风口高度对碰撞射流气流特征影响实验研究

通过实验研究了碰撞射流热风供热时不同的送风口高度下室内空气温度、速度和热舒适参数分布情况。分析了送风口高度影响作用,结果表明碰撞射流热风供热系统的送风口高度对室内热环境有显著影响。     

下送上回通风方式供冷与供暖运行性能比较

下送上回通风方式目前得到了广泛的研究应用,其供冷运行时就是置换通风,但同样一套通风系统在一些地区的寒冷季节则有可能需要作供暖运行.为了获得下送上回通风系统在分别作供冷与供暖运行时的具体性能参数,本文应用实验测试与计算流体力学(CFD)模拟的方法研究了置于环境实验室内的某办公环境.研究中分析比较了该办公环境内的空气速度、温度以及追踪气体污染物的浓度分布.研究结果表明,下送上回通风方式作供冷运行时空气温度及污染物浓度分层现象明显,空气处于半混合状态,置换效果较好;作供暖运行时,温度及污染物浓度趋于均匀,通风系统性能接近于混合送风系统,不具备良好的抑制交叉污染的能力.     

Airflow and air temperature distribution in the occupied region of an underfloor ventilation system

Measurements were carried out in an office-type experimental room ventilated by a floor return-type underfloor ventilation system to investigate the distributions of airflow velocity and air temperature. A fan-powered floor air unit (FAU) with rectangular supply and return air outlets covered by straight-profile linear bar-type air diffusers was installed to deliver the conditioned air in the experimental room. Turbulence intensity and draught rate distributions inside the room were also calculated by using the measured data. From the experimental results, it is found that undesirable high air velocities and high draught rates were created within a small region near the supply outlet of the FAU. Temperature differences between different height levels were maintained within an acceptable comfort level under the tested supply air conditions and heat loads. The results indicated that the temperature stratification could be maintained at an acceptable comfort level by designing the supply air conditions properly. A clearance zone is suggested as a design consideration for locating the FAUs and occupants to avoid undesirable draught discomfort to the occupants.     

Measurements of air temperatures close to a low-velocity diffuser in displacement ventilation using an infrared camera

The near zone of supply air diffusers is very critical for the indoor climate. Complaints of draft are often associated with low-velocity diffusers in displacement ventilation because the air is discharged directly into the occupied zone. Today, the knowledge of the near zone of these air supply diffusers is insufficient, causing an increased need for better measuring methods and representation of the occupied zone.A whole-field measuring technique has been developed by the authors for visualization of air temperatures and airflow patterns over a large cross-section. In this particular whole-field method, air temperatures are measured with an infrared camera and a measuring screen placed in the airflow. The technique is applicable to most laboratory and field test environments. It offers several advantages over traditional techniques; for example, it can record real-time images within large areas and capture transient events.The purpose of this study was to conduct a parameter and error analysis of the proposed whole-field measuring method applied to a flow from a low-velocity diffuser in displacement ventilation. A model of the energy balance, for a solid measuring screen, was used for analyzing the influence of different parameters on the accuracy of the method. The analysis was performed with respect to the convective heat transfer coefficient, emissivity, screen temperature and surrounding surface temperatures.Theoretically, the temperature difference between the screen and the ambient air was found to be 0.2–2.4 °C for the specific delimitation in the investigation. However, after applying correction the maximum uncertainty of the predicted air temperature was found to vary between 0.62 and 0.98 °C, due to uncertainties in estimating parameters used in the correction. The maximum uncertainty can be reduced to a great extent by estimating the convective heat transfer coefficient more accurately and using a screen with rather low emissivity.