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Analysis of the factors influencing the airflow behavior in an impinging jet ventilation room

Building Simulation 2021年第3期14卷 749-762页

作者： Xiufeng Yang Xiao Ye Bin Zuo Ke Zhong Yanming Kang School of Environmental Science and Engineering Donghua UniversityShanghai201620China School of Hydraulic Energy and Power EngineeringYangzhou UniversityYangzhou225127China School of Mechanical and Automobile Engineering Shanghai University of Engineering ScienceShanghai201620China

A validated CFD model is employed to predict the airflow behavior in an impinging jet ventilation(IJV)room with cool,isothermal or warm *** using the numerical results,the influences of jet discharge height,supply grille shape and room height on the jet flow behavior as well as the draught discomfort are analyzed for IJV operating in heating *** results indicate that the warm supply jet of IJV rises upward to the ceiling after spreading along the floor for a certain distance due to thermal buoyancy,resulting in a limited dispersion area,while the cool and isothermal jets of IJV always spread along the whole *** IJV is used for space heating,the lower the jet discharge height,the farther the supply air spreads along the floor,and the supply grille shape and room height almost have no effect on the air dispersion *** results also show that the energy-efficient advantage of IJV in its heating mode compared to the mixing ventilation(MV)system is more remarkable in higher ***,there is a risk of draught discomfort in IJV heating rooms and it is recommended to wear socks to avoid this discomfort.

关键词： impinging jet ventilation heating scenario airflow behavior draught discomfort

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Numerical investigation of impinging jet ventilation in ICUs:Is thermal stratification a problem?

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Building Simulation 2023年第7期16卷 1173-1185页

作者： Lei Wang Zhiqiang Wang Sirui Zhu Zhe Zhu Tao Jin Jianjian Wei Institute of Refrigeration and Cryogenics/Key Laboratory of Refrigeration and Cryogenic Technology of Zhejiang Province Zhejiang UniversityHangzhouChina Center for Balance Architecture Zhejiang UniversityHangzhouChina The Architectural Design&Research Institute of Zhejiang University Co LtdHangzhouChina Zhejiang Modern Architectural Design and Research Institute Co LtdHangzhouChina

Intensive care units(ICUs)are the high incidence sites of hospital-acquired infections,where impinging jet ventilation(IJV)shows great *** stratification of IJV and its effect on contaminants distribution were systematically investigated in this *** changing the setting of heat source or the air change rates,the main driving force of supply airflow can be transformed between thermal buoyancy and inertial force,which can be quantitatively described by the dimensionless buoyant jet length scale(l_(m)^(-)).For the investigated air change rates,namely 2 ACH to 12 ACH,l_(m)^(-)varies between 0.20 and *** thermal buoyancy plays a dominant role in the movement of the horizontally exhaled airflow by the infector under low air change rate,where the temperature gradient is up to 2.45℃/*** flow center remains close to the breathing zone of the susceptible ahead,resulting into the highest exposure risk(6.6‰for 10-μm particles).With higher heat flux of four PC monitors(from 0 W to 125.85 W for each monitor),the temperature gradient in ICU rises from 0.22℃/m to 1.02℃/m;however,the average normalized concentration of gaseous contaminants in the occupied zone is reduced from 0.81 to 0.37,because their thermal plumes are also able to carry containments around them to the ceiling-level *** the air change rate was increased to 8 ACH(l_(m)^(-)=1.56),high momentum weakened the thermal stratification by reducing the temperature gradient to 0.37℃/m and exhaled flow readily rose above the breathing zone;the intake fraction of susceptible patient located in front of the infector for 10-μm particles reduces to 0.8‰.This study proved the potential application of IJV in ICUs and provides theoretical guidance for its appropriate design.

关键词： impinging jet ventilation heat sources air change rates respiratory particles lock-up phenomenon

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The impacts of evaluation indices and normalization methods on E-TOPSIS optimization of return vent height for an impinging jet ventilation system

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Building Simulation 2022年第12期15卷 2081-2095页

作者： Chao Qin Shi-Hai Wu Hong-Qiang Fang Wei-Zhen Lu Department of Architecture and Civil Engineering City University of Hong KongHong KongChina School of Architecture and Art Central South UniversityChangshaChina

Stratified air distribution(STRAD)systems have been intensively investigated in recent decades for their energy-saving potential and good indoor air quality ***,the evaluation indices used to optimize STRAD systems and the normalization methods for weight calculation vary from one research to *** study aims to investigate the impacts of evaluation indices on the optimal return vent height of a room cooled by an impinging jet ventilation system(one type of STRAD system).The effects of several widely used normalization methods(i.e.,vector normalization,sum normalization,min-max normalization,and no normalization)on indices weights are *** evaluation indices are cooling coil load(Q_(coil)),energy-saving potential(ΔQ_(coil)),mean age of air(MAA),CO_(2) mass fraction,temperature difference between the head and ankles(ΔT_(0.1-1.1)),predicted mean vote(PMV),predicted percentage of dissatisfied(PPD),and draft rate(DR).The multi-criteria optimization method is the entropy-based technique for order preference by similarity to ideal solution(E-TOPSIS).As a result,the min-max normalization method evens the weight of each index and results in unreasonable relative ***,the raw matrix(i.e.,the normalization is omitted)is suggested for weight *** these indices,ΔT_(0.1-1.1) and PPD play critical ***ΔT_(0.1-1.1),the optimal return vent height changes from mid-level to near-floor,while without PPD,it changes to *** important result is that the Q_(coil) plays the most trivial role,followed by MAA and ***,the optimal return vent height is not determined by energy-saving performance but by performances of thermal comfort.

关键词： evaluation indices normalization method impinging jet ventilation return vent height E-TOPSIS

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