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A numerical study on the effect of column layout on air distribution and performance of column attachment ventilation

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Building Simulation 2021年第4期14卷 1095-1108页

作者： Haiguo Yin Linna Li Rui Wu Yuanyuan Wang Angui Li School of Building Services Science and Engineering Xi’an University of Architecture and TechnologyShaanxiXi’an710055China

Based on the structural characteristics of existing buildings and the disadvantages of current mixed ventilation mode in the application to large space buildings,an original column attachment ventilation(CAV)has been proposed.In this study,the experiment utilized a room space with four columns uniformly distributed in the space to visualize the movement of attached airflow along the cylinder surface and the floor,the numerical technique was employed to study the effects of the column layout(i.e.,uniform,centralized,dispersed,and crossed distribution)on the air distribution of CAV mode in a standard four-column full scale model of a shopping mall.Seven indices,including airflow pattern,air diffusion performance index(ADPI),air temperature distribution,heat removal effectiveness,draught rate(DR),predicted mean vote(PMV),and carbon dioxide(CO2)concentration,were used to assess the ventilation performance.In the CAV mode with a uniform column layout scheme,the experimental results indicated that the air supply flows downward along the wall surface,forming a secondary attachment with the ground and spreading along the floor in a fan radiation flow mode.Further,an“air lake”-like speed and temperature distribution similar to displacement ventilation(DV)was formed in the occupied zone.In all simulation cases,it was found that the average air velocity was less than 0.25 m/s in occupied zone,the effectiveness for heat removal was more significant than 1.0,DR value was less than 20%,the PMV level can also satisfy most people.The average CO2 concentration was around 470 ppm in the occupied breathing zone.These results indicated that the CAV mode could be an efficient air distribution method.They demonstrated the technical feasibility of applying the CAV in the space under different column layout schemes.

关键词： column attachment ventilation air distribution column layout performance evaluation large space buildings

Effect of Different Types of Structural Configuration on air distribution in a Compact Purification Device

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Journal of Donghua University(English Edition) 2020年第6期37卷 483-492页

作者：杨学宾梁乐刘浩刘琳梁珍王方 College of Environmental Science and Engineering Donghua UniversityShanghai 201620China College of Urban Construction and Safety Engineering Shanghai Institute of TechnologyShanghai 201418China School of Energy and Environment Zhongyuan University of TechnologyZhengzhou 450007China

In some old industrial plants,in order to meet the increasingly strict requirements of pollutant emission limits,it is necessary to install the compact filtration and/or purification devices in a given narrow machine room.Different types of structural configuration might influence air distribution inside these devices.The unreasonable air distribution might lead each part of filtration or purification media to operating at largely different air flow rates.Based on a computational fluid dynamics(CFD)model,this study explores the influence of different outlet positions and different upper heights on the flow field inside chamber.The porous medium model is employed to simulate the air flow in porous media.The changing structural configurations include three positioning cases of the outlet opening and eight height cases of the upper chamber.The root mean square is defined as the non-uniformity coefficient to evaluate the uniformity of air flow distribution.The results show that the farther distance between inlet and outlet openings will bring more uniform air distribution,and the increasing height of upper chamber totally trends to exhibit more uniform air distribution.

关键词： structural configuration air distribution uniform air distribution compact purification device coefficient of velocity inhomogeneity

Numerical Simulation of the Effect of air distribution on Turbulent Flow and Combustion in a Tubular Heating Furnace

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Petroleum Science 2005年第1期2卷 44-47页

作者： WangJuan MaoYu LiLihong FacultyofChemicalScienceandEngineering UniversityofPetroleumBeijing102249China

A three-dimension full-size numerical simulation of the effect of air distribution on turbulent flow and combustion in a tubular heating furnace was carried out. A standard k –ε turbulent model, a simplified PDF combustion model and a discrete ordinate transfer radiation model were used. The hybrid grid combining a structured and a non-structured grid was generated without any simplification of the complicated geometric configuration around the burner. It was found that the multistage combustion could reduce and control the peak value of temperature. At the same time, it was concluded that the amount of primary air had little effect on the global distribution of velocity and temperature in the furnace, but a great effect on that around the burner. It is recommended that 45% - 65% of the total amount of air be taken in in primary air inlets in the furnace. All the results are important to optimize the combustion progress.

关键词： Tubular heating furnace turbulent flow combustion air distribution numerical simulation

Adaptive Wall-Based Attachment Ventilation:A Comparative Study on Its Effectiveness in airborne Infection Isolation Rooms with Negative Pressure

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Engineering 2022年第1期8卷 130-137页

作者： Ying Zhang Ou Han Angui Li Li’an Hou Thomas Olofsson Linhua Zhang Wenjun Lei School of Building Services Science and Engineering Xi’an University of Architecture and TechnologyXi’an 710055China Department of Applied Physics and Electronics UmeåUniversityUmeåSE 90187Sweden School of Thermal Engineering Shandong Jianzhu UniversityJinan 250101China

The transmission of coronavirus disease 2019(COVID-19)has presented challenges for the control of the indoor environment of isolation wards.Scientific air distribution design and operation management are crucial to ensure the environmental safety of medical staff.This paper proposes the application of adaptive wall-based attachment ventilation and evaluates this air supply mode based on contaminants dispersion,removal efficiency,thermal comfort,and operating expense.Adaptive wall-based attachment ventilation provides a direct supply of fresh air to the occupied zone.In comparison with a ceiling air supply or upper sidewall air supply,adaptive wall-based attachment ventilation results in a 15%–47%lower average concentration of contaminants,for a continual release of contaminants at the same air changes per hour(ACH;10 h^(-1)).The contaminant removal efficiency of complete mixing ventilation cannot exceed 1.For adaptive wall-based attachment ventilation,the contaminant removal efficiency is an exponential function of the ACH.Compared with the ceiling air supply mode or upper sidewall air supply mode,adaptive wall-based attachment ventilation achieves a similar thermal comfort level(predicted mean vote(PMV)of0.1–0.4;draught rate of 2.5%–6.7%)and a similar performance in removing contaminants,but has a lower ACH and uses less energy.

关键词： Ventilation efficiency air change rate COVID-19 Attachment ventilation air distribution Isolation ward

CFD–DEM simulation of particle deposition characteristics of pleated air filter media based on porous media model

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Particuology 2023年第1期72卷 37-48页

作者： Kaiwen Cheng Jingjing Zhu Fuping Qian Bowen Cao Jinli Lu Yunlong Han School of Civil Engineering and Architecture Anhui University of TechnologyMa'anshan 243002China School of Energy and Environment Anhui University of TechnologyMa'anshan 243002China

In this study, the three-dimensional physical model of pleated air filtration media was simplified to porous media model, and the calculation parameters of porous media were obtained based on experimental data. The model of V-shaped pleated air filter media is constructed, the height of the media pleat is 50 mm and the pleat thickness is 4 mm, the pleat angle is 3.7°. The Hertz-Mindlin contact model was modified by Johnson Kendall Roberts (JKR) adhesion contact model. The deposition process of particles in media was simulated based on computational fluid dynamics (CFD) theory and discrete element method (DEM). Results show that the CFD–DEM coupling method can be effectively applied to the macro research of pleated air filter media. The particles will form dust layer and dendrite structure on the fiber surface, and the dust layer will affect the subsequent air flow organization, and the dendrite structure will eventually form a “particle wall”. The formation of the “particle wall” will prevent the particles from moving further in the fluid domain, which makes area of pleated angle become the “low efficiency” part about the particle deposition. Compared with area of pleated angle, the particles are concentrated in the opening area and the middle area of the pleated to agglomerate and deposit.

关键词： Pleated air filter media CFD-DEM air distribution Deposition characteristics

Direct capture efficiency of range hoods in the confined kitchen space

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Building Simulation 2022年第10期15卷 1799-1813页

作者： Changsheng Cao Wuhao Xie Yunfei Xia Jun Gao School of Mechanical Engineering Tongji UniversityShanghai 200092China

Range hood is a local ventilation device applied widely in residential kitchen for maintaining healthy environment. This study firstly defines the direct capture efficiency (DCE) based on the two-zone model in a confined kitchen space. A mass flux ratio of the secondary captured pollutant to the entrained pollutant from the room zone is proposed for the determination of DCE, where the distribution coefficient is firstly solved, and then its sensitivity analysis on the DCE is carried out. To validate the mass flux ratio and concisely identify the DCE, a virtual purification method that artificially sets the escaped pollutant to zero, is further applied. Compared with the newly developed DCE, the existing indexes, such as contaminant removal efficiency (CRE), total capture efficiency (TCE), fail to differentiate the direct capture from the total capture. Finally, the effects of such factors as makeup airflow pattern, exhaust flow rate, cooking source temperature and the individual occupied/unoccupied on the DCE are fully studied. It is confirmed that different makeup airflow pattern results in distinguished airflow distribution, which makes a significant difference of more than 30% in DCE. Over 50% increase of DCE can be achieved when the exhaust flow rate is increased from 300 to 600 m3/h. About 30% decrease of DCE is observed with the increased cooking source temperature from 100 to 300 °C, and 10% increase of DCE is appeared in the individual occupied case. This reasonable definition and determination of DCE would help to improve the real capture performance of range hoods.

关键词： kitchen ventilation capture efficiency air distribution local exhaust makeup airflow

Thermal sensation and percentage of dissatisfied in thermal environments with positive and negative vertical air temperature differences

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Energy and Built Environment

Energy and Built Environment 2023年第6期4卷 629-638页

作者： Yuxin Wu Sheng Zhang Hong Liu Yong Cheng School of Civil Engineering and Architecture Zhejiang Sci-Tech UniversityHangzhouZhejiang 310018China Joint International Research Laboratory of Green Buildings and Built Environments(Ministry of Education) Chongqing UniversityChongqing 400045China School of Human Settlements and Civil Engineering Xi’an Jiaotong UniversityXi’an 710049China School of Civil Engineering Chongqing UniversityChongqing 400045China

Considering the percentage of dissatisfied due to local thermal sensation(PD LTSV),a vertical air temperature difference(ΔT_(d))threshold of about 3°C was recommended in standards.However,some novel air distribution methods might create large positive(which means the head warmer than the feet,vice versa)or negativeΔT_(d),with no suitable proved criteria to be used.In this study,sixteen subjects were seated in a climatic box placed in a climate chamber to evaluate thermal sensation and percentage of dissatisfied with negative and positiveΔT_(d) in different whole-body thermal conditions.air temperatures were controlled independently at the upper and lower body parts,with 13 different air temperature sets combined with 22°C,25°C,28°C,and 31°C(i.e.-9°C≤ΔT_(d)≤9°C).Results showed that subjects were more thermally sensitive at the upper body and with positiveΔT_(d) than at the lower body or with negativeΔT_(d).The 80%acceptableΔT_(d) range is about-8 to 7°C in overall neutral(TSV=0),-7°C to 6°C in slightly cool(TSV=-0.5)conditions,which is wider than-3 to 3°C in slightly warm conditions(TSV=+0.5).By considering the factors of both TSV andΔT_(d),a new overall percentage of dissatisfied index(OPD P)was proposed.Case studies show that the new OPD P index is more precise and suitable for the evaluations of different air distributions to predict overall percentage of dissatisfied in thermal environments with vertical air temperature difference.

关键词： Vertical air temperature difference Thermal sensation Thermal comfort Percentage of dissatisfied air distribution

Experimental Research on Plasma Induced by TEA CO_2 Laser Propulsion

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Plasma Science and Technology 2008年第2期10卷 203-206页

作者：卢宏程祖海左都罗翟冰洁余亮英朱海红 Division of Laser Science and Technology Wuhan National Laboratory for Optoelectronics-Institution of Optoelectronics Science and Engineering Huazhong University of Science and Technology Wuhan 430074 China

Results in the air-breathing propulsion experiments with a parabolic light craft and a self-made UV-preionized 100 J TEA CO2 laser device are presented. air disturbance and the spectrum of the plasma after the interaction of pulsed laser radiation with the light craft were studied. It was found that the focal length of the parabolic light craft had a significant effect on the air-disturbance. Two shock waves were detected for the longer focal length, while only one shock wave detected for the short focal length. The spectrum of the laser-induced plasma, the distribution of the characteristic lines, and the temporal behaviors of the air plasma were studied in detail. The results showed that, the evolution of the laser-induced plasma lasted 20μs, and the plasma spectrum would reach the maximum intensity at 7μs.

关键词： laser propulsion TEA CO2 laser-induced plasma air distribution

Quantitative analysis of coherent structures affecting instantaneous fluctuation of point-source plumes based on PIV-POD method

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能源与人工环境(英文)

能源与人工环境(英文) 2020年第2期1卷 131-138页

作者： Yukun Xu Xin Wang Fei Wang Bingyan Song Yujie Zhang Chenlu Shi School of Environment and Architecture University of Shanghai for Science and Technology516 Jungong RoadYangpu DistrictShanghai200093China

For an enclosed space like an industrial plant where devices and equipment generate a large amount of heat,the fluctuation characteristics of thermal plume become more crucial.This paper aims to study the unique air distribution of the point-source plume by shutting down all valves in a thermostatic chamber.250 consecutive instantaneous flow fields(in each zone)were measured by a two-dimensional particle image velocimetry(PIV)system at a sampling frequency of 3 Hz to quantify the air distribution of the plume.Based on the experimental data,the indoor instantaneous velocity and vorticity fields were analyzed,and the transient velocity fluctuation characteristics of typical points were discussed.The fluctuation periods of the plume at different heights were ini-tially estimated.Through the proper orthogonal decomposition(POD)analysis,the dominant coherent structures in complex instantaneous flow fields were excavated,and the turbulent kinetic energy of coherent structures was calculated.In addition,POD analysis provided a new method for validating and improving transient numerical simulation models.

关键词： Thermal plume PIV Instantaneous flow field POD air distribution