Experimental study on thermal environment in large-space building with low sidewall air supply

The thermal environmental characteristics are experim-entally studied in terms of different air supply volumes and outdoor meteorological parameters in a large-space building which is air conditioned with a low sidewall air supply.The experimental results show that the indoor vertical temperature distributions under different condition are similar.The maximum vertical temperature difference（MVTD）is up to about 20 ℃,and it linearly changes with the sol-air temperature.The indoor vertical temperature gradients（VTGs）in the upper,central and lower zones are different.The influence of the sol-air temperature on the VTGs in the upper and the lower zones is greater than that in the central zone.The characteristics of the VTGs in the three zones affected by the air supply volume are the same as those affected by the sol-air temperature.Besides,because of the small air velocity,the predicted mean vote（PMV）on comfort in the occupied zone is slightly high and the air temperature difference between the head and the ankle is usually more than 3 ℃.

Draft sensation distribution of air jet supply system in large space building in summer

To study the draft sensation distribution of an air jet supply system in a large space building in summer,experiments are conducted in a large laboratory.The temperature,velocity and draft sensation distributions at a nozzle height of 4 m in the occupied zone are obtained.Then,the numerical simulation under the test condition is carried out by the computational fluid dynamics（CFD）method.The calculation results of the indoor vertical temperature and the draft sensation distribution are validated by the test data.Simulations with different nozzle heights are conducted.The satisfactory air supply condition is determined by analyzing the draft sensations and the temperatures in the occupied zone under three conditions.The simulation results show that the optimal draft sensation distribution and the uniform temperature and velocity fields can be obtained at a nozzle height of 5 m.

Thermal stratification level of low sidewall air supply with air-conditioning system in large space

The thermal stratification level of low sidewall air supply system in large space was defined. Depending on the experiment of low sidewall air supply in summer 2008,the thermal stratification level was studied by simulation. Based on the simulation of experiment condition,the air velocity and vertical temperature distribution in a large space were simulated at different air-outlet velocities,and then the thermal stratification level line was obtained. The simulation results well match with the experimental ones and the average relative error is 3.4%. The thermal stratification level is heightened by increasing the air-outlet velocity with low sidewall air supply mode. It is concluded that when air-outlet velocity is 0.29 m/s,which is the experimental case,a uniform thermal environment in the higher occupied zone and a stable stratification level are formed. When the air-outlet velocity is low,such as 0.05 m/s,the thermal stratification level is too low and the air velocity is too small to meet the human thermal comfort in the occupied zone. So,it would be reasonable that the air-outlet velocity may be designed as 0.31 m/s if the height of the occupied zone is 2 m.

Air entrainment in a vertical dropshaft with limited air supply

Dropshafts are vertical structures widely used in urban drainage systems and buildings for water transportation.In this paper,a physical model study was conducted to investigate the air entrainment in the dropshaft under various flow regimes with and without air ventilation.Observed from the experiments,the air entrainment mechanisms varied with the water flow regimes in the dropshaft.When there was no water plug formed in the dropshaft,air could be supplied directly from downstream.Once the water plug was formed,while without venting,the air was replenished only from downstream intermittently and then in the form of large air bubble traveling upwards to the airspace at the top;while with venting,air was mainly replenished from the dropshaft top and no large air bubble was observed.The experimental results also showed that the amount of entrained air in the dropshaft with venting was greater than that without venting.

Adaptive inverse control of air supply flow for proton exchange membrane fuel cell systems

To prevent the oxygen starvation and improve the system output performance, an adaptive inverse control （AIC） strategy is developed to regulate the air supply flow of a proton exchange membrane fuel cell （PEMFC） system in this paper. The PEMFC stack and the air supply system including a compressor and a supply manifold are modeled for the purpose of performance analysis and controller design. A recurrent fuzzy neural network （RFNN） is utilized to identify the inverse model of the controlled system and generates a suitable control input during the abrupt step change of external disturbances. Compared with the PI controller, numerical simulations are performed to validate the effectiveness and advantages of the proposed AIC strategy.

Prediction Analysis on the Transport Distance of Supply Air in Warm Air Heating Room with Impinging Jet Ventilation Systems

To overcome the disadvantages of displacement ventilation( DV) and traditional mixing ventilation( MV) system,a new ventilation system known as impinging jet ventilation system( IJVS)has been developing. The warm air can be supplied with impinging jet ventilation( IJV), while the DV is only used for cooling.However,the flow and temperature field of IJV under heating scenario has had few references. The paper is mainly focused on computational fluid dynamics( CFD) and developing an adequate correlation between the distance L that warm air can reach and different parameters in the warm IJVS by using response surface methodology( RSM). The results indicate that L decreases as the supply velocity υ decreases but increases as the supply temperature difference ΔT or the discharge height h decreases. In the variable air volume( VAV) system, it is necessary to determine supply parameters both under the maximum-heat-load condition and the small-heat-load condition. Unlike the VAV system,the constant air volume( CAV) system has no need to study the small-heat-load condition. Draught discomfort near the nozzle becomes the issue of concern in IJVS, thus the suitable discharge height is of great importance in design and can be calculated based on the predictive model.

Location Problem of Air Materials Supply Center for Air Force

Based on the analysis of three influencing factors on the air material supply center location, the location model of air material supply center was established. By solving the model, the rational supply center of air materials was also determined.

Influences of the Fresh Air Volume on the Removal of Cough-Released Droplets in a Passenger Car of a High-Speed Train Using CFD

The spread and removal of pollution sources,namely,cough-released droplets in three different areas(front,middle,and rear areas)of a fully-loaded passenger car in a high-speed train under different fresh air flow volume were studied using computational fluid dynamics(CFD)method.In addition,the structure of indoor flow fields was also analysed.The results show that the large eddies are more stable and flow faster in the air supply under Mode 2(fresh air volume:2200m3/h)compared to Mode 1(fresh air volume:1100m3/h).By analysing the spreading process of droplets sprayed at different locations in the passenger car and with different particle sizes,the removal trends for droplets are found to be similar under the two air supply modes.However,when increasing the fresh air flow volume,the droplets in the middle and front areas of the passenger car are removed faster.When the droplets had dispersed for 60s,Mode 2 exhibited a removal rate approximately 1%–3%higher than Mode 1 for small and medium-sized droplets with diameters of 10 and 50μm.While those in the rear area,the situation is reversed,with Mode 1 slightly surpassing Mode 2 by 1%–3%.For large droplets with a diameter of 100μm,both modes achieved a removal rate of over 96%in all three regions at the 60 s.The results can provide guidance for air supply modes of passenger cars of high-speed trains,thus suppressing the spread of virus-carrying droplets and reducing the risk of viral infection among passengers.

Influence of the Channel Design on the Heat Exchange Characteristics of Pulsating Flows in the Supply System of an Engine

Heat engines based on reciprocating machines remain in demand as energy converters in a variety of industries around the world.The aim of the study was to evaluate the gas-dynamic,consumable and heat exchange characteristics of non-stationary air flows in a supply system with transverse profiling of valve channels based on experimental studies.Valve channels with cross sections in the form of a circle,square and triangle were used to control the consumable and heat exchange characteristics of the flows in the supply system of the reciprocatingengine model.The article presents data on changes in local velocity,volumetric airflow and instantaneous heat transfer coefficient of non-stationary airflow in supply systems with different valve channel designs.A spectral analysis of the pulsations of the local heat transfer coefficient was also performed.The Nusselt number was calculated for the studied supply systems.The figured valve channels lead to an increase in the volumetric airflow through the supply systemupto32%comparedwiththe basic configuration.The useof a square valve channel leads to suppression of heat transfer(drop is about 15%)compared to the basic supply system,and the use of a triangular valve channel causes an intensification of heat transfer(growth is about 17.5%).The obtained data can be useful for refining mathematical models,adjusting machine learning algorithms,and improving design methods for supply systems of reciprocating machines to improve their technical,economic,and environmental characteristics.

应力加载下采煤工作面卸压钻孔裂隙演化特征

采煤工作面卸压钻孔漏风诱发的煤自燃隐患威胁矿井安全生产,研究应力加载下采煤工作面或沿空预留煤柱卸压钻孔裂隙演化特征,对有效指导煤自燃预防具有重要意义。采用理论分析和实验测试相结合的研究方法,研究了3种含孔试件在单轴应力加载过程中的应力-应变曲线,分析和划分了试件破坏过程,确定了不同应力加载下,试件孔周围裂隙发育形态分布规律和孔周裂隙位移量。结果表明:相比完整煤试件,在各项应力加载下含孔煤试件的峰值应力强度平均降低55.49%,峰值应力超过6 MPa含孔煤试件孔周围出现T形裂隙。随着外加载应力增大,孔周裂隙扩展延伸至试件发生形变破坏,试件孔周边出现大量裂隙网络,外界应力加载过程中,试件沿孔周的径向位移和环向位移均大于0.5 mm。表明含孔试件在载荷应力作用下卸压钻孔发生形变破坏,产生大量毫米尺度的裂隙网络,在钻孔周围松动圈未及时采取裂隙封堵措施的状况下,容易长时间漏风供氧而发生煤自燃隐患。

转炉风机负荷分配在PS转炉集中供风系统中的应用

针对PS转炉集中供风系统在生产过程中转炉用风波动量大、风机易喘振等问题,以甘肃某公司动力厂鼓风机站转炉供风系统智能控制研发与应用项目为案例,分别对风机单机控制系统、PS转炉集中供风系统中风机负荷分配方案以及多台风机与PS转炉的智能联动系统做了详细的介绍,对于其他风机集中供风系统升级优化具有一定的借鉴意义。

空调温度对数据机房总能耗的影响

数据中心的高能耗问题成为各方关注的重点。本文针对上海市某数据中心业务包间在不同空调末端送回风设定温度下对空调末端运行能耗、IT设备运行能耗及空调末端能效的影响进行了测试研究。研究发现:随着空调末端送回风温差增大,机房整体运行能耗降低,空调末端能效提高;在固定送回风温差的情况下,送风温度越低,IT设备运行功耗越低,机房包间总能耗越低。

某报告厅空调系统气流组织优化设计

针对不适用座椅送风的报告厅冬季温度分层导致前排热舒适性差的问题,采用CFD数值模拟的方法,对比分析上送风方案和优化方案冬季气流组织效果,并基于空气分布特性指标ADPI对夏季设计工况进行了校核。结果表明,优化方案相比上送风方案有效缓解了温度分层的情况,人员热舒适性得到显著提高。

结合空气源热泵能耗分析及光伏辅助的建筑供热设计方法

随着国家对北方地区冬季集中供热方式的普及,煤燃烧供暖方式造成的环境污染和能源消耗问题更加严重。为了优化北方建筑供热系统的能耗问题,研究设计了光伏辅助的空气源热泵供热系统。研究方法通过数值模拟构建了建筑能耗模型,结合供热需求优化了空气源热泵供热系统,增设了保温层和除霜模式。同时,研究评估了建筑供热系统的热负荷,以最小二乘法修正热泵的实际效能。并借助光伏供电方式协调了空气源热泵的能耗,结合供热系统的整体效益优化了供热控制系统。研究结果显示,光伏辅助的空气源热泵平均供热量可以达到23.74 kW,在模拟环境下的整体节能效益为77.19%~83.26%,相较于传统锅炉供热节能效益提升了59.24%。可见改进供热系统在同等制热效果下表现出更高的节能效益。因此,改进供热设计在节能效果上具有更高效的节能效果,为建筑供暖提供了一种环保节能的供热方式。

城轨车辆主供风单元减振方案及实车效果分析

某城市地铁6号线项目中,制动系统前期选用活塞式主供风单元,出现了安装点上方车厢地板振感较大的问题,为此,在新项目设计初期尝试采用有油螺杆式主供风单元。文章通过对主供风单元吊装结构分析,结合轨道交通行业常用减振方案的性能特点,系统性探讨、总结了城轨车辆主供风单元减振器布置形式及设计选型原则,并结合有限元仿真及实车试验对本项目减振方案进行效果验证,以期改善前期项目车厢地板振动异常问题。研究结果表明:选用有油螺杆式主供风单元减振方案对机组振动传递降低明显,主供风单元吊挂安装点及车内地板处的振动加速度均处于较低水平(<0.315 m/s^(2))。

厨房通风工程的设计要点分析

针对厨房的通风工程的设计问题,文章从勘察设计的三大设计阶段展开,分析了厨房工程的土建预留条件、设备的选型与布置、厨房内的气流组织问题,提出了厨房通风工程的设计要点,以提高厨房通风工程设计的合理性,改善厨房的环境卫生和厨师工作区的空气品质,为类似厨房通风工程的设计提供一定参考。

Analysis and Modeling of Wangqing Oil Shale Drying Characteristics in a Novel Fluidized Bed Dryer with Asynchronous Rotating Air Distributor

In order to replace the conventional distributor, a novel asynchronous rotating air distributor, which can optimize the drying ability of fluidized bed and strengthen the drying performance of oil shale particles, is creatively designed in this study. The rotating speed of the asynchronous rotating air distributor with an embedded center disk and an encircling disk is regulated to achieve the different air supply conditions. The impacts of different drying conditions on the drying characteristic of Wangqing oil shale particles are studied with the help of electronic scales. The dynamics of experimental data is analyzed with 9 common drying models. The results indicate that the particles distribution in fluidized bed can be improved and the drying time can be reduced by decreasing the rotating speed of the embedded center disk and increasing the rotating speed of the encircling disk. The drying process of oil shale particles involves a rising drying rate period, a constant drying rate period and a falling drying rate period. Regulating the air distributor rotating speed reasonably will accelerate the shift of particles from the rising drying rate period to the falling drying rate period directly. The two-term model fits properly the oil shale particles drying simulation among 9 drying models at different air supply conditions. Yet the air absorbed in the particles' pores is diffused along with the moisture evaporation, and a small amount of moisture remains on the wall of fluidized bed in each experiment, thus, the values of drying simulation are less than the experimental values.

基于Airpak的空调送风方式对室内热环境影响分析

空调房间内气流组织的好坏决定着室内空气的质量,因此营造合理气流组织是空调设计的重要组成部分。改善室内空气品质(IAQ,Indoor Air Quality)依赖于有效的通风换气和合理的气流组织。本文利用Airpak对某办公室三种空调送风方式的温度场、PMV-PPD(Predicted Mean Vote-Predicted Percent Dissatisfied)值进行模拟分析,研究结果说明位于中间顶部顶送侧回的空调系统的气流组织效果最佳,从而为改善空调房间的热环境设计提供了方法和理论依据。

Numerical Analysis of Influencing Factors on Temperature Field and Airflow Distribution of the Displacement Ventilation System

Indoor air quality and thermal comfort are important features of indoor environment. In this paper, a numerical simulation based on the k-ε model of CFD is used to analyze factors such as loading, exterior-protected construction, blowing-in rate that play an important role in the temperature field and airflow field of the displacement ventilation system. Exterior-protected construction has little influence on indoor temperature distribution of displacement ventilation systems and the influence is limited only in a small area near the external wall when the indoor heat source is the main cooling load.The height of a room has little influence on indoor temperature field, and the temperature gradient of active region is basically unchanged. In the system combined with a displacement ventilation system and a cooling system, the height also has little influence. When the cooling load is high,the indoor heat source creates a strong convective plume, which will make the average indoor air age lower, the ventilation efficiency higher and the elimination of pollutant easier. Air supply rate plays an important role in displacement ventilation systems. The increase of air supply rate that can be realized by increasing the air supply velocity and enlarging the area of air inlet will increase the mass capability of the system and diminish the vertical temperature gradient. From the comparison between simulations and experiments, it is concluded that this simulation are creditable.

基于Airpak的被动房办公室地送风数值模拟研究

被动房仅依靠新风换气机实现通风和热回收,能大幅度降低建筑能耗,且办公室作为工作人员长时间停留场所,增强室内通风效果具有重要意义。本文主要研究了地送风出风口与排风口的不同数量及不同位置对被动房办公室气流组织的影响。利用Airpak软件对被动房办公室地送风进行数值模拟,得到室内气流组织的温度场及速度场,并采用PMV-PPD对室内人员热舒适性及空气品质进行了评价。在通风效果方面,对被动房办公室的地送风设计进行了优化。