bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of Ventilation And Decentralized Purification on Pollutant Control in Urban Highway Tunnels without Exhaust Shaft
Authors: He Dapeng , Yue Zhen , Zhang Yindong , Xie Fei , Chang Moning , Dong Qiwei , Liu Yemin , Shao Xiaoliang , Li Xianting
Published: August 2022

Limited by multiple factors, such as land use planning, landscape coordination and environmental standards, the ventilation conditions of the urban highway tunnels are insufficient, and therefore the joint control of ventilation and purification becomes a necessary solution. In this study, the effect of number, location of decentralized purification equipment, and the tunnel ventilation rate on pollution in the tunnel are studied using one-dimensional calculation. The results show that the arrangement of purification equipment can reduce the design ventilation rate to a certain extent. When purification equipment is arranged, the maximum NO2 concentration can be reduced by up to 30.9%, and the average NO2 concentration can be reduced by up to 18.2% compared with that without purification. The purification equipment arranged in the rear section of the tunnel is conducive to reducing the concentration of pollutants at the exit, while the arrangement in the middle section of the tunnel is conducive to reducing the average concentration of pollutants in the tunnel.
Research on the Ratio between the Convection and Radiation Heat Exchange Amount of the Face and Head of Manikin in the Thermal Comfort Condition
Authors: Yang Xinwei , Wang Lihui , Bai Xinhui , Ma Changjiang , Ma Jianan , Zhu Jialiang
Published: August 2022

In this paper, the radiation heat exchange coefficient of the exposed parts of human body is firstly obtained through pre-experiment, which is used to separate the total output heat exchange amount of the manikin. Then the heat exchange amount of manikin under different airflow organizations of personal ventilation, mixed ventilation and seat ventilation are respectively studied. The value of convection heat exchange and radiation heat exchange of the face and head of human body are compared. And variable conditions are studied for different air temperatures and volumes. It is concluded that when the supply air temperature changes between 22? and 30°C with human body thermally comfortable, the total heat exchange of the face and head changes from 38 W/m2 to 137 W/m2, and the range of the radiation heat exchange amount is 26 W/m2 to 67 W/m2. The convection heat exchange amount changes between 6 W/m2 and 110 W/m2, and the ratio of radiation heat exchange to convection heat exchange changes from 0.5 to 6.7.
Simulation study of heat transfer characteristics of a biomimetic honeycomb CO2 gas cooler
Authors: Zhang Yujia , Wang Zhihua , Li Guichen , Wang Fenghao
Published: August 2022

CO2 air source heat pumps are widely used because of their advantages of energy saving, high efficiency and clean. Gas cooler is one of the key components of CO2 heat pump system, while its heat transfer effect will affect the energy efficiency of the whole system. In order to improve the heat transfer efficiency, a biomimetic honeycomb gas cooler is proposed in this paper, the steady-state simulation model of the biomimetic honeycomb gas cooler is established by using MATLAB software, and the reliability of the model is verified by literature data. In addition, the heat transfer performance of the biomimetic honeycomb gas cooler is compared with that of the tube-in-tube gas cooler. The results showed that, under the same working condition, compared with the tube-in-tube gas cooler, the outlet temperature of the biomimetic honeycomb gas cooler with 1st, 2nd and 3rd level increased by 9.7°C, 25.4°C and 27.3°C, and heat transfer can be increased by 55.5%, 205.4% and 220.6% respectively. This research is helpful to provide the reference for the design and optimization of this type of gas cooler, and is conducive to the popularization of CO2 air source heat pump.
Analysis of Regulation Characteristics in Acceptable Thermal Comfort Zone under Cooling Conditions
Authors: Zhai Yingxian , Ma Lie , Liu Meng , He Yujie , Zhou Chengdong , Xie Xin , Dai Longkang , Liu Huan
Published: August 2022

Residents mainly set the temperature at the range of 25°C to 27°C under cooling conditions. However, they may feel uncomfortable after staying a period in a steady-temperature environment. To make themselves more comfortable, residents will change their postures and even regulate the temperature. To analyze the regulation characteristics, this study combined thermal environment testing, questionnaire survey, video collection, and data mining methods to collect the thermal environment and comfort background, posture, and temperature regulation characteristics. The results showed that Mean Thermal Sensation Vote gradually deviated from neutrality and tended to be cooler even though the thermal environment and thermal comfort were both within the acceptable zone. 12 typical posture regulations were captured and divided into 3 categories: head (face) postures, trunk postures, and limb postures. Head (face) postures were the concentrated expression of adaptive postures (80%). Although the total posture frequency remained unchanged, the head (face) postures gradually increased, which reflected the increase in discomfort. The temperature regulations accounted for nearly 25%. Most people (90%) regulated the temperature at 1 °C with the frequencies of once or twice, and they preferred to set the temperature up than down. In the first 3 hours, there would be a regulation peak every 20 or 30 minutes, while the regulation decrease after 3 hours.
A review of heat stress evaluation indices in extremely hot environments
Authors: Feng Guohui , Zang Yan , Sun Jialin , Liu Yuhan
Published: August 2022

Selecting appropriate evaluation indices to evaluate extremely hot environments has become an urgent problem to ensure the safety of workers’ lives and improve labor productivity. The objective of this review is to compare relevant evaluation indices for assessing heat stress and to analyze the more effective ones applicable to the industrial environment by considering each one together. Based on extensive research on existing literature and relevant international standards, this paper introduces the definitions of heat stress and its influencing factors. Based on the actual needs of workers, analyze the existing heat stress indices from a practical standpoint, and summarize the definitions, advantages, and limitations of each index. As a result, this paper emphasizes that the relevant thresholds of thermal indices should be appropriately adjusted to suit different industrial environments. The hazards of extreme work environments can be reduced by developing new indices, charts, or related strategies. This review will provide a solid theoretical foundation for environmental control schemes for harsh working situations.
Study on prediction model of thermal sensation under local draft in low pressure environment
Authors: Ge Baowei , Wang Haiying , Xu Zan , Li Jiankai , Chen Dongyang
Published: August 2022

Local draft experiments were conducted to establish the overall thermal sensation prediction model under low pressure environment. Head, chest, hand, and ankle were exposed to local airflow under three pressure environments: 1 atm, 0.87 atm, and 0.74 atm, respectively. The skin temperature was measured and the subjective questionnaires were collected. The results showed that in cooler environment, the mean skin temperature decreased with the decrease of pressure, and people maybe more sensitive. When the environmental pressure decreased, the overall thermal sensation decreased correspondingly. Compared with the normal pressure condition, as the pressure decreased, the weight of local thermal sensation on overall thermal sensation changed a little. The weight of chest decreased while the weight of hands increased. When exposed to local draft, the four body parts showed similar influence on the overall thermal sensation under lower pressure conditions. Based on influence of pressure, temperature, and local draft speed, the overall thermal sensation prediction model for each body part was established respectively. The results indicated that the predicted values were highly correlated with the measured values. The models could be used to predict thermal sensation of people who are exposed to local draft in low pressure environment.
Experimental study on the thermal comfort and physiological responses of the elderly in unstable environments
Authors: Zhang Zixuan , Wu Yuxin , Liu Hong , Li Baizhan , Kosonen Risto
Published: August 2022

In this study, the investigators used comparative experiments in order to study the age differences and the effects of temperature changes on physiological responses. Firstly, This paper analyzed the thermal sensation differences and the trend of changes in the design working conditions in different age groups. The researchers found that the thermal sensation of elderly people was lower than that of young people in the hot environment and higher than that of young people in the cold environment. On this basis, the heart rate changes of the elderly in the dynamic environment and the differences with the young people were studied. The results showed that the heart rate of the elderly and the young people increased with the increase of temperature in the temperature rise condition, but there was no significant difference between the two groups. In the temperature drop condition, the heart rate decreased with the decrease of temperature. Finally, an equation was developed to quantitatively predict heart rate parameters. The equation predicts human heart rate by ambient temperature, and the results show that the least square error of the prediction equation for elderly people is 46, while the average difference between the actual and predicted values is 1.2. Therefore, it is recommended to use the proposed heart rate prediction equation when predicting the healthiness of heart rate in elderly people.
The effect of diffuse ceiling ventilation air supply on human thermal comfort under radiant asymmetry
Authors: Yuyao Guo , Shuaixing Xu , Yawen Gai , Bin Yang
Published: August 2022

Sidewall radiant heating creates a non-uniform thermal environment. In office buildings, it is important to know how to supply fresh air to reduce radiant asymmetry without causing draft. As a solution, diffuse ceiling ventilation (DCV) is used to supply fresh air into a sidewall radiant heated room. 20 subjects (10 males and 10 females) were recruited and subjective assessments were obtained. The results show that under the influence of sidewall radiant heating, there are differences in the subjects’ requirements for airflow and wall temperature on both body sides. Skin temperature and thermal sensation of the same body parts decrease differently when the subjects move away from the radiant heating panels, especially in forearms, shanks and feet. DCV airflow with low supply momentum interacts with thermal plume formed by radiant heating panels.
A questionnaire investigation on people’s sleep and health in constant temperature and humidity environment in China
Authors: Yu Huili , Chen Liping , Liang Shimin , Hu Songtao , Liu Rujin
Published: August 2022

In recent years, constant temperature and humidity air-conditioning systems have been widely used and promoted in residential buildings all over the world. At the same time, the influences of long-term stable indoor environment on people’s lives, especially on sleep quality and health, have attracted wide attention. Therefore, in this paper, a questionnaire investigation on people’s sleep and health in constant temperature and humidity environment was carried out in China. By comparing the questionnaire investigation results from the users of constant temperature and humidity air-conditionings with unused, it could be found that people living in constant temperature and humidity houses have better performance in sleep quality, but worse health condition. These results suggested that constant temperature and humidity air-conditioning had an effect on human bodies. The findings can also inform future study on the role of thermal environment on sleep and health.
Field study on thermal environment and adaptation of workers in winter
Authors: Xu Zan , Wang Haiying , Ge Baowei , Li Jiankai , Sun Lin
Published: August 2022

In order to analyze the thermal environment and its influence on workers’ thermal adaptation, a field study was conducted in a rubber factory during winter. Indoor and outdoor environmental parameters were measured and subjective questionnaire surveys were collected. The study was conducted from November to January the next year. During the survey, indoor temperature was in the range of 12.6 to 21.7°C and indoor air velocity ranged from 0.15 to 0.3 m/s. The clothing insulation during heating period was between 0.85-0.9 clo, while it was between 1.21-1.33 clo during pre-heating period. The estimated metabolic rate was around 2-2.2 met. Analysis showed that the thermal sensation vote (TSV) was higher than that predicted by PMV. The neutral temperature difference between TSV and PMV was 4.8°C. The thermal comfort and thermal adaptation of workers in winter were systematically analyzed and a thermal adaptive model was proposed. Basis on the adaptive model, the comfort temperature range of workers was suggested.
Review of continuous adjoint method for inverse design of indoor thermal environment
Authors: Zhao Xingwang , Yin Yonggao
Published: August 2022

The continuous adjoint method has been used in the indoor environment for more than ten years, but it has not been widely used up to now. This paper describes the current state of the continuous adjoint method and presents an overview of the continuous adjoint method for inverse regulation of the indoor environment from different aspects, including the inverse identification accuracy, inverse identification efficiency, inverse identification function, and globally optimal.
Thermal environment characteristics of large space building with stratified air conditioning based on Block-Gebhart model during the cooling season
Authors: Miao Yufeng , Huang Chen , Yang Tong , Ma Jingsi , Wang Xin , Wang Fei
Published: August 2022

The thermal environment of large space building with stratified air distribution is characterized by its obvious gradient of vertical temperature, and the stratified air conditioning load (SACL) is closely related to the thermal environment. The Block-Gebhart (B-G) model in summer is established for an actual large space building which has two stratified air distribution (STRAD) systems. One system is the air supply nozzles (ASN) arranged at middle sidewall, the other is the half-cylinder diffusers (HCD) arranged at low sidewall. In order to quickly calculate the air temperature of unoccupied zone (ATUZ), two regression equations for the air temperature gradient under the conditions of two STRAD systems were proposed. Considering six factors, the B-G model was used to calculate 648 cases and the two equations were obtained by multiple regression analysis. Through the field measurement in summer, in three cases of ASN system, the mean absolute error (MAE) between predicted and experimental values of ATUZ was 1.4°C, and the mean absolute percentage error (MAPE) was 4.5%; in three cases of HCD system, the MAE was 1.0°C and the MAPE was 3.0%. The results of this study establish the foundation for the calculation of SACL.
Analysis of Indoor Thermal and Humidity Environment of Radiant Cooling Coupled with Attached Jet System
Authors: Zhuang Zhaoyi , Lv Chaoqun , Yang Xiu , Shen Wenzeng , Shao Wei , Zhang Chuntian
Published: August 2022

The radiant cooling combined with attached jet air supply system is a temperature and humidity independent control system. Radiant cooling panels are used to bear the indoor sensible heat load, and the attached jet air supply is used to bear the indoor humidity load. Numerical simulation method is used to study the changes of indoor relative humidity and dehumidification efficiency of radiant cooling panels installed on ceiling and wall, as well as the advantages and disadvantages of all three systems taking into consideration the radiant cooling coupled with wall attached jet air supply with deflectors in terms of comfort. The results show that the attached jet has good adhesion to the cooling panel and will not leads to condensation; the dehumidification efficiency of wall attached jet is relatively poor; at the height of 0.1m, the thermal comfort of wall radiant cooling system is the best; at the height of 0.7m, the wall radiant cooling system with deflector is the best; in the working range of 1.1 ∼ 2.4m, the wall radiant cooling system is better than the ceiling radiant cooling system with or without deflector.
Analysis of dehumidification method and discussion on improvement measures in solar greenhouse
Authors: Lu Hemei , Lei Wenjun , Tai Chuanmin , Ye Junbao , Qi Xinye , Zhang Linhua , Wang Xiaolong
Published: August 2022

The solar greenhouse is a passive agricultural facility building which can realize the anti-seasonal production. The main enclosure structure of solar greenhouse is composed of thermal insulation wall, thermal insulation roof and daylighting shed film. The transmittance of sunlight is an important index affecting the healthy growth of plants in solar greenhouse. After testing, the difference between the solar radiation intensity received through the greenhouse film and the outdoor solar radiation intensity during a day has large fluctuations. The reason for this phenomenon is that the humidity in the greenhouse is large, and there is condensation on the greenhouse film, which seriously affects the transmittance of sunlight. The dehumidification methods commonly used in solar greenhouses are summarized, and their advantages and disadvantages are analyzed in this paper. In addition, the problems existing in the current dehumidification methods are discussed. In view of the characteristics of the solar greenhouse that the high temperature needs ventilation and cooling during the day and the low temperature at night needs to supplement heat, a composite ventilation system with anti-condensation, heat storage, cooling and dehumidification is proposed, and its performance is analyzed.
Correlating indoor and outdoor temperature and humidity in megacities in China
Authors: Yang Mengya , Lei Hao
Published: August 2022

Since people spend much more time indoors, indoor conditions may be better indicators of personal exposure than outdoor. Several studies have explored the associations between indoor and outdoor temperature, humidity in USA or in tropical regions. Few studies examined these associations in China. In this study, we collected the daily indoor temperature and relative humidity (RH) in 1577 household in four megacities across temperate and subtropical regions in China, from March 2017 to July 2018. We use Pearson correlation analysis to examine their correlations with outdoor. We found that the correlation between indoor and outdoor RH was stronger in Northern China (r=0.76 V.S. r=0.58), while the correlation between indoor and outdoor temperature was stronger in Southern China (r=0.92 V.S. r=0.80). In the winter-spring months, there was no statistically significant linear relationship between indoor and outdoor temperature. However, the correlation between indoor and outdoor RH in high urbanized regions in winter-spring was stronger than that in low urbanized regions (r=0.85 V.S. r=0.70). This may be due to the comment use of air conditioning and ground heating in the high urbanized regions. This study provides insight for assessing the indoor-outdoor environment correlations in China.
Exploration on The Characteristics of Natural Ventilation in Bedrooms and Its Determination Method
Authors: Huang Chen , Zhang Jialing , Zhang Qinhou , Zou Zhijun , Zhou Lele , Miao Yufeng
Published: August 2022

In this paper, the CO2 (carbon dioxide) exhaled by indoor occupants was used as the tracer gas, and the variation of indoor CO2 concentration in the whole day was observed. Among the 454 samples, 114 and 345 valid samples were screened out which can be used to calculate the daytime and night ventilation rate by the tracer gas method through the sectioning method. The results indicated that seasonal differences in daytime average ventilation are greater than night average ventilation. The highest daytime- average ventilation was found in autumn, next was summer, there was the lowest ventilation in winter. According to the necessary fresh air rate when sleeping at night, night average ventilation rate of 30.1% of samples met the standard. The ventilation rates of different building characteristics were analyzed, residential location, construction age, living floor, room size, window structure, indoor dampness, and window opening habits were all included. The results revealed that the window opening habits was the most significant factor for natural ventilation. Both daytime and night average ventilation rate are basically in the ratio of 2:1 when the windows are opened and closed. moreover, there was higher impact of outdoor climate on daytime average ventilation when window was closed. Significant impact of window structure and indoor dampness on night average ventilation was observed when window was opened. Present study proposed the measurement and determination methods of ventilation when daytime activities of occupants were happened
Optimization research on indoor ventilation mode of cave dwellings in northern Shaanxi
Authors: Liu Zongxin , Ji Changfa , Zhang Pengju , Zhang Huan
Published: August 2022

Cave dwelling is a characteristic residential building in northern Shaanxi. It is not only a masterpiece created by local residents in accordance with nature and local cases, but also meets the requirements of green ecology and sustainable development. In order to understand the influence of ventilation on the indoor environment of cave dwellings in northern Shaanxi, a representative traditional cave dwelling was selected as the research object. Based on the meteorological data in Yan'an and the actual measurement of indoor and outdoor thermal parameters, the methods of theoretical analysis, field testing and numerical simulation were adopted to study the indoor airflow distribution of cave dwellings under different ventilation methods, the results show that: the cave dwellings in northern Shaanxi have good thermal insulation performance, and the indoor temperature fluctuation is small; the relative humidity in the cave dwelling is relatively high, which is opposite to the trend of temperature change; reducing the humidity is the ventilation of the cave dwelling. The main task; the indoor wind speed is too small to form effective ventilation. Adjusting the size of the skylight can improve the natural ventilation in summer to optimize indoor ventilation. Through optimization analysis, when the size of the skylight is 0.5m*0.5m, the indoor airflow velocity changes between 0 and 0.3m/s, the ventilation efficiency is high, and the ventilation effect is high. Good, there will be no eddy current in the room, which can effectively remove moisture and enhance lighting, which can provide a basis for the opening of ventilation skylights in new local caves. Effectively improve indoor heat and humidity environment.
Variation of Indoor Airflow Patterns under Dynamic Outdoor Wind Conditions in Large Space Naturally Ventilated Buildings
Authors: Lv Yuling , Yao Huimin , Li Ang , Shen Xiong
Published: August 2022

Understanding Indoor Airflow Patterns (IAPs) helps control air contaminants in large naturally ventilated buildings (NVBs). However, the effect of random and unpredictable changes in outdoor wind conditions (OWC) is a major contributor to the variation in IAPs in the NVBs, making the IAP uncontrollable. This study presents the results of field measurements and numerical simulation in a NBV to study the IAP variation characteristic under the dynamical OWC. The OWC data monitored in real time was processed with Kalman Filtering (KF) and the gradient method to decompose the data prior to being entered into the CFD solver. The trend was similar between the simulated and measured data of a full size NVB. In addition, the distribution of internal turbulence intensity varied widely depending on the spatial locations and time intervals. The variation in speeds in the vicinity of windbreaks greatly affected the variation in IAP on a certain frequency scale. The results not only prove that CFD simulation to be an efficient tool for the prediction of time-averaged IAP, but also initialize efficient measures for the control of IAQ in dynamic OWC of large space NVBs.
Study on ventilation performance of inclined solar chimney coupled with indoor heat source
Authors: Lin Congtong , Lei Yonggang
Published: August 2022

The study of ventilation air distribution of the building with built-in heat source and set inclined solar chimney is carried out through 3D numerical simulation. The synergistic effect of thermal plume formed by internal heat source and solar chimney effect is analyzed. The effects of different solar radiation intensity I, heat flow density W at the surface of the internal heat source and structural parameters (including the height of the internal heat source from the ground h and the mezzanine inlet spacing b) on the indoor natural ventilation performance of the building are investigated.
Improving Indoor Multiphysics Prediction with Local Measurements Based on Data Assimilation
Authors: Qian Weixin , Liu Jing , Tang Ming , Gao Hu
Published: August 2022

Accurately mastering the distribution of multi-physical field is an important prerequisite for rationally formulating building environment construction scheme. In practical engineering projects, sensor monitoring can obtain more accurate environmental state parameter values. However, due to the constraints of investment cost, spatial limitations and other factors, the number of on-site measured monitoring points is limited. On the contrary, CFD simulation can obtain global distribution information of the physical field, but the uncertainty of parameters such as boundary conditions seriously affects the reliability of simulation results. In view of the above problems, based on Ensemble Kalman Filter (EnKF), which is a sequential data assimilation algorithm, a technical framework for accurate indoor multiphysics simulation is established. We evaluated the performance of this method with reduced-scale model experiments, verifying that the simulation errors can be significantly reduced. The proposed method has a positive impetus for realizing the global monitoring of the physical field of the building space.
PIV experimental study of airflow structures in a multi-slot ventilation enclosure with opposed jets
Authors: Wang Congcong , Gao Xuening , Li Jiayu , Chen Hongbing
Published: August 2022

The airflow structure of enclosure directly affects the spread of COVID-19 and is also closely related to indoor air quality, thermal comfort of personnel, and building energy consumption. Although a large number of studies on the airflow field have been conducted under mixing and displacement ventilation with a single air inlet in rectangular rooms. However, to the best of the authors knowledge, only a limited number of studies have dealt with airflow structures in a multi-slot ventilation enclosure with opposed jets. Therefore, this paper uses PIV to study the velocity and entropy of unstable airflow field in a multi-slot ventilation enclosure with opposed jets under isothermal and non-isothermal conditions. And this paper presents due to the collision of the jets to form two large-scale eddies, the airflow field structure being unstable. In the region without air supply inlets and exhaust outlets, a large-scale vortex is formed in the airflow field, resulting in high information entropy of the flow field. The thermal plume suppresses the large-scale flow field structure and increases the small-scale flow field structure.
PIV Measurement and Simulation of Building Thermal Plume under No-wind Conditions
Authors: Zhang Tiantian , Han Dongliang , Tan Yufei , Liu Jing
Published: August 2022

To investigate the buoyancy characteristics of building façades, this study deals with experimental and numerical investigations on building façade flow and temperature field in different façade temperature conditions with different height-aspect ratio of building facade. PIV measurements are conducted in a static wind platform for obtaining the mean velocity, the vertical velocity and the horizontal velocity around the building surface. To simulate the plume characteristics accurately, this study adopt three numerical model and compared the numerical results with the PIV experimental data. The result indicated that the simulation result of the RNG k-ε model best agreement with experimental data. Analysis of numerical results indicated that the wind speed kept increasing in the vertical direction, while the wind speed first increased and then decreased in the horizontal direction. The air temperature tended to be constant in the vertical direction, but air temperature first drooped sharply and tended to be constant in the horizontal direction. As the heat flow density increases, the building facade plume strength increases. When the wall heat flow increases from 100W/m2 to 200 W/m2, the maximum velocity of the wall increases by 1.6 m/s and the temperature increases by 15 °C.
Experimental study on multi-robot 3D source localization in indoor environments with weak airflow
Authors: Chen Axiang , Zhang Boyuan , Cai Hao , Wei Ling , Liao Yu , Zhou Bin
Published: August 2022

The purpose of this paper is to provide a new method for solving the problem of the 3D source localization in indoor environments with weak airflow by the experimental study on the multi-robot method. For this purpose, we developed a 3D MRO (mobile robot olfaction) system consisting of three mobile robots. The gas sensor carried with each robot has a moving range of 0.5 m to 1.5 m on the Z-axis. A total of 60 experiments were conducted to validate and compare the standard whale optimization algorithm (SWOA) and the standard particle swarm optimization (SPSO) methods in a 7.65 m×4.1 m experimental area with two source heights (0.75 m and 1.05 m). For two source heights, the success rate and localization step of the SPSO method are 56.7% (17/30) and 31.4 steps, respectively. In addition, the success rate and localization step of the SWOA method are 80% (24/30) and 32.9 steps, respectively. These results show that the SWOA method has strong application potential in indoor environments with weak airflow.
Evaluation of fast fluid dynamics with different solving schemes on scalar transport equation for predicting indoor contaminant concentration
Authors: Zhou Pengzhi , Wang Haidong , Dai Yuwei , Huang Chen
Published: August 2022

Predicting the transport of indoor pollution can assist designer to optimize ventilation mode of room. However, the high computational cost restricts the wide implementation of computational fluid dynamics (CFD) technique to predict indoor contaminant concentration. This study evaluated three potential numerical methods with scalar transport equation to resolve this dilemma which were combine fast fluid dynamics (FFD) and different solving schemes on scalar transport equation. To test the performance of three potential numerical methods, the conventional PISO algorithm was also employed to compare. A threedimensional ventilation case with experimental data of indoor CO2 concentration was adopted. The results show that the FFD with iterative scheme of scalar transport equation could predicting indoor CO2 concentration efficiently. The numerical method with semi-Lagrangian method and iterative scheme for predicting indoor air contaminant concentration could obtain satisfactory results at large time step size.
Determination of the discharge coefficient through vent driven by a non-Boussinesq plume in an emptying filling box
Authors: Liu Yang , Huang Zhongwei , Huang Lan
Published: August 2022

The effect of high buoyancy forces due to density contrast between the fluids on either side of the vent on the discharge coefficient Cd is taken into account in the laboratory. Salt water experiments are conducted at small scale in a large fresh water tank with saline to generate buoyancy force. In non-Boussinesq cases, a larger discharge parameter Γd at the vent may make plume-like flow contract further with a smaller value of the discharge coefficient. A nearly twofold time in the non-dimensional form for draining light fluid fully out of the space is observed comparing with time predicted with a constant value of Cd = 0.6 for simple draining flows. A displacement flow theoretical model with virtual source correction at the initial position of an internal source is developed to reveal a time-dependent movement of the layer interface, and the oscillatory amplitude of the interface overshooting during the transient period is found to depend on the two dimensionless geometrical parameters Λ and Θ.
Numerical Simulation of Gas-Liquid Two-Phase Leakage of R-290 Refrigerant in Split Air Conditioner
Authors: Zhang Qianru , Liu Yuhong , Zhao Jinchi , Wang Xin
Published: August 2022

R290 as a refrigerant has significant advantages of low cost, high energy efficiency, and more environmental protection, but the leakage will form a hazardous area inside the indoor unit and the room where the concentration exceeds the lower flammable limit of propane. In this paper, we focus on the gas-liquid two-phase leakage of R-290 indoor air conditioner at the evaporator, and use Computational Fluid Dynamics (CFD) method to numerically simulate the refrigerant leakage dispersion at three air conditioning supply volumes of 178.2 m3/h, 342 m3/h and 576 m3/h, and analyze the indoor velocity distribution and concentration distribution. The results show that the trajectory of the refrigerant jet changes under different air supply volumes, and the simulation results show that the spatial extent of the combustion explosion limit is mainly distributed at the air conditioning leak and the air conditioning outlet. Vortices were formed in the local area above the propane leakage port and then spread.
Predicting Unsteady Indoor Temperature Distributions by POD-DNN
Authors: Wei Chenghao , Ooka Ryozo , Zhang Bingchao , Zhou Qi
Published: August 2022

In this study, to predict unsteady temperature distributions, POD-DNN was utilized, where DNN was trained to predicted coefficients of POMs. Two strategies, flatten POD-DNN and nested POD-DNN were compared. The flatten POD-DNN provided high accuracy if training data is sufficient, but otherwise very inaccurate. The nested POD-DNN roughly predicted the development of temperature fields even training data was small. The results showed their different sensitivities to the training data size.
Numerical Study on the Periodicity of Urban Heat Dome Flow
Authors: Zhang Yan , Fan Yifan
Published: August 2022

Under calm conditions where the background synoptic wind is weak or absent, the difference between city and rural temperature allows natural convection to develop. The turbulent circulation is also referred as urban heat island circulation or urban heat dome flow. The coupling of buoyancy, inertia, and vertical stability induces a natural periodicity in the urban heat dome flow. The periodicity in urban heat dome flow is often neglected in previous urban heat dome flow research. In this article, a high-precision CFD numerical method is applied, and the city is treated as a homogeneous flat plate with a specific shape. First of all, the real atmosphere model (around 20 km in length scale) are established and validated with water tank experiments. Convergent inflows at lower level and divergent outflows at upper levels can be observed. Then, the instantaneous 3D flow field distribution is analyzed, and the periodicity of the upper outflow region (fout) after reaching the quasi-steady state is determined. Finally, cases with different city diameters (D), regional heat flux (H0), and ambient potential temperature gradients (∂θ/∂z) are designed and solved. A quantitative description of periodicity (fout) and its relationship to buoyancy (B0), inertia (Ud) and vertical stability (N) is presented.
Study on the characteristics of airflow at the top of the building with parapet
Authors: Yang Changqing , Liu Yubo , Liu Zhiyong , Li Angui , Qiao Lingmin , Song Bingye
Published: August 2022

The presence of the roof structure affects airflow patterns around the building. The recirculation area formed in the roof area is different from the original due to the presence of parapets and billboards. So the traditional formula no longer applies. Pollutant gases emitted by buildings can accumulate in recirculation areas, causing air short circuits and polluting indoor air. However, studies on the flow characteristics of building roofs with parapets are still lacking. In this paper, cfd simulation is used to study the influence of parapets of different heights and summer thermal effects on airflow. The results show that as the height of the parapet increases, the size of the vortex generated at the top also increases gradually. As the temperature difference between the top and the air increases, that is, the Ri increases, the vortices formed on the top will decrease significantly and the amount of reduction is not linear with the temperature difference.
Experimental analysis of single-sided natural ventilation and interunit dispersion in scaled 2D street canyons
Authors: Dai Yuwei , Zhang Fuyao , Xu Dongmei
Published: August 2022

Interunit dispersion problems have been studied previously mainly through on-site measurements, wind tunnel tests, and CFD simulations. In this study, a scaled outdoor experiment was conducted to examine the interunit dispersion characteristics in consecutive two-dimensional street canyons. Tracer gas (CO2) was continuously released to simulate the pollutant dispersion routes between the rooms in street canyons. The reentry ratio was analyzed to reveal the interunit dispersion of the rooms in the street canyons. This study provides authentic airflow and pollutant dispersion information in the street canyons in an urban environment.
Assessment and Mitigation of Infection Risk Caused by a Coughing Person
Authors: Kilpeläinen Simo , Lestinen Sami , Kosonen Risto
Published: August 2022

The recent COVID-19 pandemic has increased public awareness of the importance of clean indoor air. Many studies have been conducted on how virus-like particles propagate in indoor environments, and how their spreading could be constrained. In this study, we assessed how the infection risk caused by a coughing person behaves in a meeting room. We analysed how well different protective measures (face masks, visors, air purifiers, partitions) can reduce the risk. The room had a floor area of 21 m2 and was furnished with a conference table with seating for six people. The room was equipped with a mixing ventilation system providing fresh air at a rate of 36 l/s, or 1.7 l/s·m2. The supply air temperature was 17°C and the room air temperature 23°C. The coughing person was realized by a cough/sneeze machine Ch3st developed by CH Technologies, USA. Paraffin oil was aerosolized with a BLAM nebulizer from the same company and released in bursts by the cough machine to emulate real coughs. A breathing thermal manikin (PT Teknik, Denmark) was used as the exposed person. Two TSI 3330 OPS optical particle sizers were used to assess the particle concentrations. There were 14 test cases in total. A case with no protective equipment was used as the reference. During each measurement, 21 coughs were released into the test room and the particle concentrations were monitored at one-second intervals from the exposed person’s breathing zone and from the infector’s workstation. Each cough reaching the exposed person produced a sharp peak in the particle concentration and the number of these peaks was used to assess the effectiveness of each protection measure. The distance between the opposite workstations was 120 cm. The results indicate that masks and visors on the infected person, and partitions, are effective protective measures against cough-based pathogens. Air purifiers and personal protection on the exposed person had little effect.
The motion law of aerosols produced by human respiration under the action of thermal plume in ventilated room
Authors: Wu Songlin , Wang Hanqing , Li Chengjun , Liu Qiuxin
Published: August 2022

To investigate the human exhaled particle motion law under the effects of the thermal plume in a ventilated room, a three-dimensional model of a typical double ward was created. The Large Eddy Simulation was utilized to study the effects of thermal plume of different intensities on particle diffusion, and the removal effects of varied ventilation rates on particles during displacement ventilation were simulated. The results show that the thermal plume formed by a human model at varied room temperatures has a consistent distribution law, and particle diffusion distance and velocity are positively linked with plume intensity. Lower ventilation rates are preferable for particle-removal in the reasonable ventilation mod
Numerical Investigation on the Effect of Ventilation on the Distribution of Phthalate Esters in the Residential Environment
Authors: Wu Sijing , Kang Lingyi , Li Runjie , Wang Xinke , Zhou Xiaojun
Published: August 2022

Semi-volatile organic compounds (SVOCs), such as phthalates and brominated flame retardants, is a kind of emerged pollutants due to wide application in indoor environment. Certain indoor SVOCs have been found to be associated with various adverse health effects, attracting large attentions of researchers. Due to relatively low vapor pressure, SVOCs are easily adsorbed on various surfaces including particles. Therefore, airborne SVOCs are always simultaneously presented in the gas-phase and particle-phase. Ventilation is an important means to improve indoor air quality. Different forms of indoor air distribution will affect the distribution of indoor pollutants and further affect the exposure to the human body. Therefore, in this paper, we selected Di (2-ethylhexyl) phthalate (DEHP) as the target compound and employed computational fluid dynamics (CFD) technique to simulate the emission of DEHP and the concentration distribution with different phases in a modeled room. Euler-Lagarian model is applied to simulate flow field, particle tracks and UDF (user defined function) was implemented to describe the dynamic adsorption of DEHP by the suspended particles. Furthermore, the effect of location of vent and airflow rate on indoor fate of DEHP were discussed and the effect of particle age on indoor fate of DEHP was also investigated.
Establishment of Pollutant Concentration Model for Laminate Flooring Based on the Coupling Effects of Time and Temperature
Authors: Yu Liang , Guo Yanchun , Liu Zijia
Published: August 2022

Modern people are entering the third period of pollution, marked by indoor air pollution. The aim of this paper is to investigate the relationship between decorative materials and the pollution concentrations of typical indoor pollutants such as HCHO, C6H6 and VOC, using a combination of qualitative and quantitative methods. The environmental test chamber method is used to carry out the experimental measurement of the laminate flooring, and the numerical analysis is carried out according to the test release concentration and environmental parameters. The Levenberg-Marquardt optimization algorithm was selected to develop a first-order exponential (ExpDec1) mathematical model based on the concentrations of HCHO, C6H6 and VOC released from laminate flooring at different temperatures. The results show that the model predicts the characteristics of HCHO, C6H6 and VOC concentrations with time and temperature and there is a positive correlation between environmental parameters and release concentration, with correlation coefficients of 0.993, 0.925, 0.856, 0.992, 0.906 and 0.879 between measured and predicted values, and slopes of regression lines of 0.993, 0.932, 0.872, 0.994, 0.916 and 0.893. There is good consistency between measured and predicted values. The model provides a necessary basis for in-depth study of this issue and a solid evidence foundation for air quality.
Study on Indoor Air Radon Measurement in a University in Shanghai
Authors: Ni Haoquan , Pan Minyi , Yin Yanmei , Chen Jingyu , Zou Zhijun , Li Hao , Sun Chanjuan , Su Chunxiao
Published: August 2022

With the improvement of people's requirements for living environment, the effect of indoor radon radioactivity on health has been widely concerned. In this paper, taking a university in Shanghai as an example, indoor radon concentration and its related environmental parameters were measured in some of its rooms to understand the level of indoor radon concentration on its campus. The results showed that the average concentrations of student dormitory, office buildings, and academic buildings were 14.79±9.15 Bq/m3,22.67±5.72 Bq/m3, and 12.55±6.71 Bq/m3 respectively. Indoor radon was positively correlated with indoor temperature and humidity, and ventilation was also an effective method to reduce indoor radon.
Study on the change of indoor and outdoor air quality with height in high-rise buildings during the initial heating period
Authors: Zhou Peitao , Fan Yuesheng , Zhang Xin , Wang Huan , Niu Bowen
Published: August 2022

The indoor and outdoor pollutant concentrations of a high-rise building in Xi’an was tested and analyzed during the initial heating period in this paper. Also the relationship between indoor and outdoor pollutant concentration, building height and outdoor meteorological parameters in different periods was an-alyzed at the same time. Compare and analyze the ratio of indoor and outdoor particle concentration (I/O value) in different time periods. The results showed that during the test period, the concentration of partic-ulate matter reached the highest value at noon and the lowest value after dusk. The I/O value tends to de-crease with the increase of the building height, but at some moments there is a situation where the I/O value is greater than 1. The research results of this paper can provide a theoretical basis for indoor particulate control and architectural design of high-rise buildings.
Effects of carbon dioxide exposure on human cognitive abilities in an enclosed workplace environment
Authors: Cao Xiaodong , Li Pei , Zhang Jie , Pang Liping
Published: August 2022

In this study, fifteen participants were exposed in an enclosed environmental chamber to investigate the effects of elevated carbon dioxide (CO2) concentration on their cognitive abilities. Three CO2 conditions (1500 ppm, 3500 ppm, and 5000 ppm) were achieved by constant air supply and additional ultra-pure CO2. All participants received the same exposure under each condition, during which they performed six cognitive tests evaluating human perception, attention, short-term working memory, risky decision making, and executive ability. During each exposure condition, the reaction time (RT) test, speed perception test, visual search (VS), 2-back test, balloon analogue risk test (BART), and Stroop test were successively conducted with rest intervals of approximately 13min. The results showed that there was no statistically-significant difference in the performance of RT tests, speed perception test, and 2-back test. This indicated that the elevated CO2 concentration below 5000 ppm did not affect the participants’ perception and short-term working memory. However, significant increase of response time was observed in the VS test, BART, and Stroop test at 5000 ppm compared with lower exposure concentrations. The slower reaction reflected the negative effects of elevated CO2 concentration on human visual attention, risky decision making, and executive ability. The findings suggest that work performance could be negatively affected by the exposure to CO2 at the current occupational concentration limit.