bluuebunny/crossref_metadata_2025 huggingface dataset:
Ethylene distribution and ventilation strategies of apple cold storage
Authors: Zhao Ximei , Nan Xiaohong , Wu Qunfei , Zhang Lei
Published: August 2022

Ethylene is a kind of plant hormone that may affect storage quality of fruit and corresponding ventilation strategies of cold storage. The purpose of this study was to explore the emission characteristics of ethylene and put forward ventilation strategies to reduce ethylene concentration. A real 230 t cold store for apples in Fufeng County of China was taken as the research object, Gas Chromatograph analysis (GC analysis) was applied to test ethylene concentration in the cold room, it was found that the indoor ethylene release rate peak appeared at 70 d. A 3-D, unsteady, incompressible and viscous numerical calculation model was developed and the component transport model was applied to numerically study the complicated phenomenon of heat transfer and mass transfer in the cold storage room. The results show that the ethylene concentration formed a tendency of diffusion from the apple zone to the air zone, and the highest ethylene concentration did not appear in the center of the apple zone, but appeared near the bottom of the apple zone. Furthermore, the air cooler was recommended to be running during ventilation for shorter ventilation time of 40 min and better temperature stability for cold storage.
Theoretical Study on Unsteady Temperature Field and Heat Regulating Zone for Earth-air Heat Exchanger
Authors: Che Jigang , Li Angui , Li Jiaxing , Guo Jinnan , Xu Hong
Published: August 2022

The earth-air heat exchanger (EAHE) play an important role in building energy efficiency. Most of the previous studies have adopted numerical simulation and experimental methods, and Theoretical research was rarely used. The theoretical analysis method has clear mathematical physical meaning. Due to the few theoretical analysis methods used, there were no general criteria for the value of heat-regulating zone. The inaccurate value of the heat regulating zone will cause calculation errors or waste unnecessary computing resources. In this research, the calculation formula of the unsteady temperature field of the EAHE was derived and the calculation correlation of value of the heat regulating zone was also given. The results show that the derived calculation formula of the unsteady the dimensionless airflow of EAHE is in good agreement with the experiment, and calculation correlation of the value of the heat regulating zone is suitable for various engineering. This research provides a theoretical basis for the design and application of tunnel ventilation and a correlation formula for the value of the heat regulating zone.
Crowd infection and its prevention strategy in a subway station based on social force model
Authors: Yao Meng , Huang Huiming , Wang Lina , Yang Kang , Cui Haihang , Chen Li , Zhou Min
Published: August 2022

With the development of society, crowds in public buildings are dense, and the subsequent spread of diseases in places with high population density has attracted widespread attention. In the real situation, the spread of the disease has its complexity, such as the influence of factors such as the movement of people and the intervention of external measures, so it is necessary to further refine the description of the process of infection transmission. Based on the social force model, this article focuses on the impact of microscopic crowd movement in public places on the dynamics of infection. Taking a typical pedestrian exit process in a subway station as an example, we numerically simulated the infection problem among small-scale people in public places, observed the impact of pedestrian movement characteristics on infection transmission, put forward corresponding prevention and control measures, and verified the effectiveness of the measures.
An Improved Method for Determining The Interface Height of Smoke Layer in A Tunnel Fire
Authors: Xiong Kang , Liu Fang , Weng Miaocheng
Published: August 2022

Smoke layer interface height is an important parameter in fire safety science. In this paper, two methods are proposed on the basis of integral ratio method and the least squares method. a series of experiments were conducted in a 1:10 scale model tunnel for determining the smoke layer interface height in tunnel fire. The interface height of the smoke layer determined by the new methods have been compared with other existing approaches, including integral ratio method, least squares method, N-percentage rule. The comparison results show that the results of the least squares method based on the transition layer can be relatively reasonable and agree well with the visual observations for all experimental condition. In addition, the usage scenarios and considerations of the N-percentage rule were also discussed.
Research on the Prediction of Energy-saving Potential of Traffic Tunnel Based on BP Neural Network
Authors: Zhengye Wang , Tong Ren , Hong Zhang
Published: August 2022

Accurate grasp of underground building environmental temperature and humidity and cooling and heating loads is the basis for energy-saving analysis, ventilation and air conditioning system design and operation control. In order to come up with a method that can quickly and accurately predict the environmental temperature and humidity and energy-saving potential of underground power station traffic tunnel, this paper takes Xiangyou pumped storage power station traffic tunnel as the research object and designs a BP neural network model for traffic tunnel temperature and relative humidity prediction with respect to the main environmental influencing factors. Comparing with the test data, it is verified that the model has high prediction accuracy. At the same time, the prediction model was used to calculate the energy saving potential of traffic tunnel ventilation. The results showed that the relative error of predicting the energy saving potential of traffic tunnel in summer was less than 2% and in winter was less than 0.3%. This prediction method can obtain the traffic tunnel air temperature and humidity and ventilation energy saving potential simply and accurately, so that the design can be developed in the direction favorable to the energy saving of underground buildings.
Study on internal structure optimization of drying Chamber of Sludge drying equipment
Authors: Ren Xiaofen , Chen Qidong
Published: August 2022

Aiming at the problem of uneven distribution of velocity field in the drying chamber of JKFF series low-temperature closed cycle sludge drying equipment, the influence of internal structure change of drying chamber on air distribution was studied by numerical simulation. Fluent software is used for simulation, through the analysis of three factors affecting the internal structure of the oven, such as the position of the blower, the spacing of the mesh belt layer and the size of the aperture of the nylon mesh belt. The results show that it is better to put the air blower inside the heat pump than to put the air blower outside the bottom of the oven. When the spacing between the second and third layers is 240mm, the overall air distribution in the drying room is the best; By comparing and analyzing 9 combined working conditions of mesh belt aperture size, it is concluded that when the aperture size of the first and second layer mesh belt is 2mm×2mm, and the aperture size of the third layer mesh belt is 1.5mm×1.5mm, the air distribution in the oven reaches the best state.
Influence of air distribution modes in civil air defense basement on carbon dioxide concentration distribution in wartime
Authors: Wang Zongwei , Gao Qingfei , Li Xianming , Qiao Lihua , He Weijia , Wang Haijian , Liu Wenjie
Published: August 2022

In order to protect the living environment and effectively control the harmful gas composition in the basement of civil air defense in wartime, this paper studies the pollutants of a civil air defense basement project in Jinan by CFD numerical simulation technology, and simulates the CO2 concentration distribution under three different air distribution forms in civil air defense. The results show that when the second-class shelter reaches the high-density population environment, the air conditions under the distribution form of side air supply and upper air return of the building meet the living conditions of the shelter personnel. The average CO2 concentration is 7200 ppm, but the central area forms a pollutant concentration area with an area of about 14.3%, and the highest concentration is 17000 ppm, which affects the physiological function of the shelter personnel. The CO2 concentration distribution simulated by the air distribution modes of upper air supply, side air return and upper air supply, lower air return is more uniform, and the average pollutant concentration is 6000 ppm and 5500 ppm. The air distribution effect of upper air supply and lower air return is the best, where the CO2 concentration is 23.6% lower than that of side air supply and upper air return scheme and 8.3% lower than that of upper air supply, side air return outlet scheme. The CO2 concentration distribution is uniform and there is no pollutant aggregation point. Under the special conditions of wartime, the air distribution of upper air supply and lower air return with uniform air outlet layout is more conducive to pollutant control.
Influence of draft curtain height on smoke exhaust effect in a large area metro depot
Authors: Yang Shi , Liu Huiqiang , Xu Desheng , Li Yanfeng
Published: August 2022

The metro depot area has the characteristics of large area and high storey and the smoke diffusion under fire conditions in these areas are more complicated. It is important to investigated smoke exhaust effect which is closely related to the safety of firefighters. FDS (Fire Dynamics Simulator) numerical simulation method was adopted to investigate the influence of draft curtain height on the performance of smoke exhaust fan which were installed on the inside wall of the metro depot area. The curtain heigh was set as 0.5m,1.0m,1.5m,2.0m,2.5m,3.0m respectively. The propagation of fire smoke, the concentration of CO2 at the exhaust outlet and the exhaust efficiency was analyzed. For the smoke vents set on the side wall, the height of the draft curtain would have greatly influence on the smoke exhaust efficiency. As the height of the draft curtain increases, the spread distance of smoke in the horizontal direction becomes short.it is beneficial to improve the exhaust efficiency of the fan on side wall. The research results could provide references for the fire protection design of the subway depot area.
Research and optimization of acoustic environment in ordinary classrooms of middle school
Authors: Li Shangzhi , Zeng Li , Qiu Shuting , Sun Hongfa , Xiang Zhifeng
Published: August 2022

A good classroom acoustic environment will contribute to teachers’ health and students’ learning. Comfortable acoustic environment requires suitable reverberation time, sufficient loudness, uniform sound field distribution, high language clarity, and no acoustic defects such as echo and acoustic focusing. In this study, the optimization strategy of acoustic environment is proposed through the investigation, field testing and numerical simulation analysis of a middle school classroom in Wenzhou under different ventilation conditions. The results show: the key factors affecting the classroom acoustic environment are outdoor activity noise, corridor noise, and classroom teacher-student activity noise. Through optimization, the quality of classroom acoustic environment is improved significantly. Classroom reverberation time (intermediate frequency) decreased from 1.5s to 0.7s; ALC decreased from 9.65% to 4.75%; STI increased from 0.534 to 0.664. The research results provided reference for acoustic design of secondary school classrooms in the future.
Measurement of the convective heat transfer coefficient of the human body in the lift-up design
Authors: Zhou Siqi , Niu Jianlei
Published: August 2022

So far, the research on the convective heat transfer coefficient (hc) in outdoor thermal comfort has mainly employed CFD simulation and wind tunnel experiments, which are difficult to fully restore the complex microclimate wind environment. In the traditional thermal comfort model, the influence of turbulence intensity (TI) on the hc might be underestimated. This study aims to measure the hc of the human body surface in the outdoor environment. A thermal manikin was placed in a lift-up building. The ambient wind speed ranged from 0.5m/s to 4m/s, with the TI ranging from 4% to 55%. The experimental results show that under the same wind speed, the difference in hc between high and low TI can be up to 15%. Based on that, the regression formula for predicting hc related to wind speed and TI was proposed. This experimental study supplements the lack of field measurement of hc in outdoor thermal comfort research, which is helpful to improve the accuracy of the outdoor thermal comfort model.
The effect of local thermal sensation on overall thermal sensation in older people under warm conditions: a chamber room study
Authors: Chen Minzhou , Velashjerdi Farahani Azin , Kosonen Risto , Kilpeläinen Simo , Lestinen Sami
Published: August 2022

Global aging and climate warming have made scholars begin to pay attention to the thermal comfort of the elderly. The deterioration of the function of body organs and systems caused by aging affects the thermoregulatory system of the elderly, resulting in a narrowing of their thermoregulatory range. To ensure their thermal comfort, personalised thermal comfort systems can be used, for example. When designing a system or selecting equipment, the impact of local thermal sensation on the overall thermal sensation needs to be considered. Most of the existing studies are based on young people, however, the local thermal sensation of the elderly may not be consistent with that of the young. This study recruited 26 Finnish older adults to conduct a series of human thermal comfort experiments under warm conditions in a climate chamber. The local and overall thermal sensations of the elderly were analyzed, and the weights of the influence of different parts on the overall thermal sensation of the elderly were obtained. The study found that the head and torso had a greater impact on the overall thermal sensation in a warm environment.
A winter case study on synergy effect of temporal and spatial alliesthesia in temporarily occupied spaces
Authors: Li Zhe , Yang Bin , Zhou Bin , Wang Faming
Published: August 2022

Temporarily occupied space (TOS) is defined as a conditioned space in which most of occupants stay for less than a certain period (e.g., 40 min). Base on the concept of TOS, specific application scenarios for transient and non-uniform thermal environments were explored by chamber tests. In the study, human subjective assessments were obtained from 16 subjects (8 males and 8 females). The synergy effect of temporal and spatial alliesthesia in TOS was quantitatively analyzed, which could achieve energy efficient thermal comfort. The synergy effect extended human thermal comfort under lower neutral temperature.
Gender differences in the effects of perceived control on thermal response during summer
Authors: Lu Dongyu , Yan Haiyan , Shi Fangning , Sun Zhen
Published: August 2022

Perceived control is considered one of the influencing factors that affect the thermal satisfaction and comfort of indoor occupants. In order to explore the relationship between human gender in thermal response and perceived control and conduct in-depth research, field research was conducted on 1186 occupants in a college dormitory in Jiaozuo (the cold region of China). The perceived control vote was divided into four scales from “ no control ” to “ complete control ” . Through collation and analysis of the data obtained, we found that with improved perceived control, females ’ discomfort is significantly reduced, which is lower than males’. Therefore, there are significant gender differences in the impact of perceived control on the thermal response, which can be explained by individual differences in physiological regulation. Similarly, there are body type differences in perceived control. This research can provide support for the adaptive model and provide a new perspective for further research on individual differences in adaptive psychological adjustment.
Thermal response test analysis of adults and preschoolers under radiant floor heating environment in a hot-summer and cold-winter area
Authors: Liu Na , Liu Dong , Wu Xiaozhou , Wang Jun , Wen Jialan
Published: August 2022

The subjective and objective thermal comfort evaluations of adults and preschoolers in radiant floor heating rooms in a hot-summer and cold-winter area are tested in this article, and the thermal response of the two groups of subjects are analysed using a differential analysis method. The thermal response characteristics of subjects wearing winter clothing with a thermal resistance of 1.02 clo and maintaining a sitting posture were studied at different locations in the office building and different indoor temperatures by combining the characteristics of hot-summer and cold-winter area and the characteristics of office buildings. The results show that when the indoor temperature varies, there was a significant difference in the local skin temperature of the calf of the two groups of subjects (P<0.05). Preschoolers have a more intense overall thermal sensation vote than adults due to the difference in metabolic rate. Different groups of people’s overall thermal sensation vote were linearly correlated. The overall thermal sensation vote of the subjects is linearly related to the indoor operative temperature. The PMV-PPD model is used as the thermal sensation evaluation standard, and there is a considerable difference between the subjective appraisal of preschoolers’ thermal sensations. The PMV-PPD model is not suitable for preschoolers.
On the use of wearable face and neck cooling fans to improve occupant thermal comfort in warm indoor environments
Authors: Yang Pengfei , Yang Bin , Yao Huangcheng , Wang Faming
Published: August 2022

Face and neck cooling has been found effective in improving thermal comfort during exercise in the heat despite the fact that the surface area of human face and neck regions accounts for only 5.5% of the entire body. Presently very little documented research has been conducted to investigate cooling the face and neck only to improve indoor thermal comfort. In this study, 16 subjects (8 males and 8 females) used two highly energy efficient wearable face and neck cooling fans to improve occupant thermal comfort in two warm indoor conditions (30 and 32 °C). Results showed that both cooling fans could significantly reduce local skin temperatures at the forehead, face and neck regions. Local thermal sensation votes at the face and neck and the overall thermal sensation votes decreased obviously at 30°C and 32°C. Both cooling fans could raise the acceptable HVAC temperature setpoint to 32.0 °C, which will significantly reduce the energy consumption of HVAC.
Local environment control of the open visitor corridor within a large space exhibition hall of site museum
Authors: Huang Xingyu , Luo Xilian , Chang Bin , Gu Zhaolin
Published: August 2022

Site museum is a kind of special public building constructed at the original place where the historical sites were unearthed, in which the unearthed relics are preserved and exhibited. The environmental control of such buildings is usually face with the problems of high energy consumption and disturbance between relics and visitors since the relics and visitors sharing the same indoor space. Local environment control is an efficient way to reduce energy consumption and achieve personalized air supply. In this research, a novel local ventilation system for the visitor corridor in winter, by combining displacement ventilation and air curtain, was proposed. Experimental tests of the system were conducted in an experimental hall with both tourist corridor and relics preservation. The results show that the visitor corridor was successfully local heated with average temperature higher than 16°C when both the displacement ventilation system and air curtain were switched on. The environmental temperature meets thermal comfort standards for short-term stay. The air curtain could efficiently prevent the infiltration of cold air and provide a warm air layer to cover the occupied area, such that thermal plume of the displacement ventilation was effective restrained.
Improving Indoor Thermal Environment of Residential Buildings Under Typical Space Heating Methods in Xinjiang, China
Authors: Wang Rong , Ma Jiali , Li Jun , Peng Wei
Published: August 2022

In order to improve the thermal environment of residential buildings in winter for Xinjiang, this research conducted a field test and a survey of residential buildings under typical heating methods. The results show that the indoor temperature and humidity are dynamically changing, and the variation of central heating and gas wall-mounted furnace fluctuated less than that of coal heating. Furthermore, the thermal environment evaluation shows that the thermal comfort level under gas wall-mounted furnace heating are the highest, which belongs to category Ⅰ. For the central heating and coal stove, only 12% and 26% of buildings achieve to category Ⅱ. Moreover, it is found that the acceptable temperature range of coal furnace heating residents can be as low as 19.5°C, while that of central heating and gas wall-mounted furnace heating is 20.3°C~25.7°C, which relate to the clothing insulation of residents under different heating methods. In addition, all residents almost have the same habit of window opening behaviour during heating period, and 72% of residents open windows for ventilation. Correspondingly, 62% of residents feel dry during heating season, which induce xerosis cutis, dry mouth and other uncomfortable symptom, and can be improved by using humidifier, planting plants and so on.
Field Measurements of Bedroom Environment in Winter and Summer on Qinghai-Tibet Plateau
Authors: Zhang Haodong , Lan Li , Yan Yan , Kang Mengyuan
Published: August 2022

Field measurements of the bedroom environment on Qinghai-Tibet Plateau was conducted by continuously measuring the air temperature, relative humidity, and CO2 concentration in the bedrooms of 197 residents (100 in winter and 97 in summer) for 7 days. And the daily environmental controls of residents were recorded. The results showed that the night-time thermal environment in bedrooms on the Qinghai-Tibet Plateau was more warmer and wetter in summer than in winter, but the CO2 concentration was lower in winter. On both winter and summer nights, drops in air temperature, relative humidity and CO2 concentration in the bedrooms were found when doors or windows were opened, increases in relative humidity and CO2 concentration in bedrooms were found when there were more occupants in the bedrooms. This study also found there was a greater reduction of CO2 concentrations when doors or windows were opened in the bedrooms of multiple occupants compared to the bedrooms of a single occupant. And on winter nights, the humidity increase in the bedrooms caused by the action of the humidifier was not affected by the status of doors and windows.
A numerical study on natural ventilation promotion and control in experimental house with fluid diode window
Authors: Hu Hong , Kikumoto Hideki , Zhang Bingchao
Published: August 2022

The objective of this study is to investigate the effects of installing a fluid diode window (FDW) in buildings to promote natural ventilation by controlling ventilation paths. An FDW is a porous plate with an internal structure that provides varying resistance to airflow depending on the flow direction. An FDW was installed in the bathroom of an experimental house to prevent polluted air from flowing into the adjacent multipurpose room during ventilation. Computational fluid dynamics simulations with a steady Reynoldsaveraged turbulence model and tracer gas method were performed to evaluate the performance of the FDW. The results show that an open window or FDW in the bathroom reduced the concentration and increased the ventilation rate. In the same wind direction at which the airflow exits through the window or FDW, it flows out at almost the same volumetric flow rate. In the cases where the airflow enters the bathroom through the window or FDW, the effect of preventing backflow from the bathroom window to the multipurpose room can be observed when the FDW was utilised, resulting in a reduction or even prevention of the gas entering the multipurpose room.
Multi-factor optimization of energy performance in naturally ventilated building: a case study of office building in hot summer and cold winter climate
Authors: Li Cong , Chen Youming , Zou Quan
Published: August 2022

Nowadays, building energy consumption is responsible for 30% to 40% of total energy usage in many countries. The energy performance of each building is related to many factors. Most of them are determined in design stage. Meanwhile, natural ventilation is one of the most potential passive energy conservation, especially in hot summer and cold winter climate zone. This study aims to figure out how to make the most of natural ventilation in building energy conservation in hot summer and cold winter climate zone. By comparing different building design plans, this study try to provide a method to help find the best-optimized building parameters design solutions. Six main factors are selected, including: building orientation, exterior wall masonry, window wall ratio, shading overhang depth, binds slat angel(include the situation when there is no blinds at all), exterior window structure. A seven-layer office building in hot summer and cold winter zone is modelled and simulated in Energyplus. Two building running plans are compared: (a) the air conditioning system is always on during office occupancy time; (b) the air conditioning system is off when natural ventilation can guarantee thermal comfort inside the building. The results shows, plan (b) saves more than 40% energy on different building parameters designs comparing to plan (a).
Impact of non-uniform heat flux on ventilation performance of solar chimney
Authors: Cai Yang , Huang Xiaoyan , Hong Binghua , He Jianwei , Zhao Fuyun
Published: August 2022

Solar chimney (SC) is an effectively practical way to enhance building natural ventilation through thermal buoyancy force, which is induced due to the temperature difference between indoor and outdoor air temperatures. The ventilation performance of solar chimney directly depends on the heat flux distributions and values in the absorbed plate. Recently, many researches have been done on the thermal performance of solar chimneys under uniform heat flux. However, the uniform heat flow distribution cannot reflect the uneven characteristics of the solar radiation. There are few studies focused on the flow characteristic and thermal performance of solar chimneys under non-uniform heat flux distributions. In this paper, a two-dimensional numerical model of solar chimney integrated building is firstly established to explore the natural ventilation performance under non-uniform heat flux distributions. The numerical simulation is conducted to predict the flow and heat transfer characteristics in the room as well as in solar chimney. Subsequently, the effects of the location of the vent are analyzed to evaluate the performance of the solar chimney system. Finally, a comparison between the ventilation performance of solar chimney under the uniform heat flux and the non-uniform heat flux distributions is presented, and the thermal and flow structures of the solar chimney integrated building are further illustrated simultaneously. Research results show that the ventilation performance of solar chimney is closely related to its heat flux distribution, and the inhomogeneity of the heat flux of solar chimney will decrease the ventilation performance of the building. In addition, the position of the vent have highly influence on the flow structure and thermal performance for the solar chimney as well as the building. This paper will provide theoretical basis and technical approach for the improvement of the performance of the solar chimney, especially for the nonuniform heat flux distribution.
Study on ventilation optimization design method of rural residential buildings in Guanzhong——A case study of red brick house project in Ezi village, Xianyang
Authors: Shang Luxuan , Gao Bo , Wang Xiaojie
Published: August 2022

Guanzhong region of Shaanxi province has a continental monsoon climate of warm temperate zone, with hot in summer and cold in winter. Therefore, the strategies of traditional houses dealing with wind environment are mainly ventilation in summer and wind protection in winter. Due to the limitation of technical and economic conditions, winter heating has always been the core problem of rural houses, so people usually adopt a relatively closed space layout to strengthen the windproof performance of buildings, but also lead to poor indoor ventilation in summer.With the development of social economy, rural residents have higher requirements for living quality, so it is very important to improve ventilation efficiency in summer under the condition of ensuring wind protection in winter. Taking the red brick house project in Ezi village of Xianyang as a practical case, in order to improve indoor wind pressure ventilation and thermal pressure ventilation efficiency, the project introduces double-height space and skylight that commonly used in urban buildings into rural houses, providing reference for the construction of similar residential buildings in Guanzhong area.
Fast Fluid Dynamics Simulation of the Airflow Around a Single Bluff Body
Authors: Jiejie Huang , Li Ruibin , Liu Zhanpeng , Zhao Yi , Feng Lu , Wu Yan , Gao Naiping
Published: August 2022

Fast and accurate simulation of the outdoor airflow distribution is important for studying urban microclimate. In this paper, two pressure-correction schemes (i.e., NIPC and NSPF) for solving the N-S equation item by item are implemented in OpenFOAM and their differences from the PISO algorithm in simulating the airflow around a single 1:1:2 bluff body are analyzed. The RNG k-ε turbulence model is chosen to study the airflow disturbance, while the second-order discretization scheme of Gauss limitedLinear is used to solve the advection term in the N-S equation. The results show that the NIPC can accurately predict the main airflow characteristics around the bluff body, while the NSPF cannot predict the recirculation region on its top. The two pressure-correction schemes underestimate the TKE distribution on the top and leeward sides of the bluff body when applying the RNG k-ε turbulence model, and the maximum relative error is about 30%. However, they are consistent with the results of the PISO algorithm under the same conditions. The two schemes are about 2.5-3.0 times faster than the PSIO algorithm when run on a CPU, and the NSPF is about 12% faster than the NIPC scheme.
A Model Based on Markov Chain for Prompt Prediction of the Airborne Gaseous Pollutant Transport in Aircraft Cabins
Authors: Wei Yun , Zhang Tengfei
Published: August 2022

Prompt prediction of the airborne gaseous pollutant transport is important to design a safe and comfortable air environment in an aircraft cabin. This paper proposes a model based on Markov chain to fulfill the task, in which the gaseous pollutant can be released from a source with an arbitrary profile. The model first obtains the airflow field by CFD to construct a transport probability matrix of the gaseous pollutant, then predicts the concentration field at each time step when an impulse is released at the known source location using the transport probability matrix. Finally, detailed trace of the pollutant released from the source with an arbitrary profile can be reproduced by linear superposition. The above strategy is applied on a two-dimensional aircraft cabin with gaseous pollutant released from one passenger for 2s. Results show that the proposed model is able to correctly predict the gaseous pollutant transport in only a few minutes. More than 90% of the computing time can be saved comparing with that from CFD without sacrificing much accuracy.
Numerical investigation of the effects of environmental conditions, droplet size, and social distance on interpersonal droplet transmission in a deep urban street canyon
Authors: Fan Xiaodan , Zhang Xuelin , Hang Jian , Weerasuriya A. U.
Published: August 2022

This study investigated the interpersonal droplet transmission between a healthy and an infected person in a deep and narrow street canyon using Computational Fluid Dynamics (CFD) simulation. The CFD simulations modelled various droplet sizes (Dp), background wind speeds (Uref), relative humidity (RH), and social distances (D) to estimate their effects on interpersonal droplet transmission. The results revealed noticeably opposite effects of these factors. For example, small background wind moved droplets upward and suspended them in the air for a longer time while high wind speeds distributed droplets in the street canyon with few of them retained in the air. Relative humidity had a trifling impact on dispersing small droplets (10μm, 25μm, 50μm), whereas it significantly modified the dispersion of large droplets, especially in small background wind speeds. Furthermore, small droplets travelled longer distances in dry air and were either deposited on the surrounding buildings’ walls or suspended in the air. In contrast, larger droplets in moist air rapidly deposited on the ground or the infected person’s body. In dry air, 45% of large droplets were inhaled or suspended in the air, exposing pedestrians to contaminated droplets. Large social distances significantly diluted the small droplets but increased the infection risk from large droplets because of the complex interaction of the ambient airflow and the gravity. It is recommended to keep social distances of 2 m and 4 m for pedestrians in deep urban street canyons in Windy condition and Calm-Wet condition, respectively.
Study on wind environment of semi-open space in hot-arid and hot-humid climate zones in rural areas
Authors: An Li , Yan Haiyan , Chen Xingyi
Published: August 2022

To explore the coupling effect of open space temperature and air velocity in hot-arid and hot-humid climate regions in rural China, 1690 valid data were obtained by long-term field tests and questionnaires were carried out in hot-arid and hot-humid regions. Results indicated that when the operative temperature is below 33.5 °C, the mean thermal sensation decreases with the increase of air velocity in the hot-humid region. When the operative temperature rose to greater than 33.5 °C, the mean thermal sensation could be significantly reduced only when the air velocity is over 1.0 m/s. However, increasing air velocity in hot-arid regions can significantly improve the thermal sensation. In addition, residents in hot-humid regions were more willing to increase airflow than those in hot-arid regions. These results support the theory of climate adaptation and can provide a reference for the design of semi-open space buildings in rural regions.
Research on the influence of outdoor wind environment on the operation characteristics of outdoor units of air conditioners in winter
Authors: Zhang Pengju , JI Changfa , Liu Zongxin , Wang Zhanrong
Published: August 2022

Variable Refrigerant Volume multi connected air conditioning system is widely used in high-rise and super high-rise buildings because of its convenient control, flexible layout and installation and energy saving. However, for high-rise and super high-rise buildings, the outdoor wind environment has a significant impact on the installation, layout and operation performance of Variable Refrigerant Volume multi connected air conditioning system outdoor units. In this paper, the numerical simulation method is used to study the variation characteristics of inlet and exhaust temperature and speed of outdoor unit under different outdoor wind speed and wind direction in winter when the inclination angle of outdoor unit shutter of Variable Refrigerant Volume multi connected air conditioning system is 0 °, ± 30 °, ± 45 ° and ± 60 ° respectively. The results show that in winter, the air inlet and exhaust outlet should avoid the outdoor wind direction as much as possible. When there is no wind outside or the wind speed is 4m/s, the shutter angle should be maintained between 30 ° and 45 °. When the outdoor wind speed is 2m/s, the shutter angle should be maintained at about 30 °.
Numerical study of climate characteristics on the residential scale energy balance based on some typical cities
Authors: Liu Zhanpeng , Li Ruibin , Wu Yan , Gao Naiping
Published: August 2022

The energy balance of residential blocks in different climate zones is simulated and analysed. The influence of climate characteristics on the residential-scale energy budget is clarified, and the temporal evolution patterns of sensible heat flux, latent heat flux and heat storage flux in the surface energy balance are obtained. From the perspective of residential blocks energy distribution, ENVI-met simulation software is used to explore the laws of climate characteristics on the change of residential scale energy balance during summer and winter in three representative cities of typical climate zones in China.. Though surface energy balance simulations, vertical surfaces are found to be a significant source of net radiation received by settlements for northern regions and horizontal surfaces for southern regions. Most of the net radiation absorbed by the residential blocks during the day is transferred to the atmosphere in the form of sensible heat fluxes.
Experimental evaluation of the airborne infection probability in ventilated office room at different supply airflow rates
Authors: Lipczynska Aleksandra , Bivolarova Mariya P. , Guo Linxuan , Kierat Wojciech , Melikov Arsen K.
Published: August 2022

The impact of the supplied airflow rate on the distribution and exposure of exhaled airborne pathogens in a room with mixing ventilation was studied. Experiments were conducted in a field laboratory at three supply airflow rates: 20, 40, 60 L/s. Two breathing thermal manikins were used to resemble infected and susceptible occupants. Nitrous oxide (N2O) was dosed into the air exhaled by the infected manikin to simulate the emission of infectious aerosols. N2O concentration was measured in the air inhaled by the susceptible manikin. The measured data were used to calculate infection probability by modified Wells-Riley model. The highest infection probability of 4.3-5.1%, obtained in the case of 20 L/s, decreased with increasing the supply airflow rate. The decrease slowed with the increase of the supply flow. The calculated infection probability based on the tracer gas concentration in the inhaled air of the exposed manikin was in all studied cases higher than the infection probability obtained in the occupied zone and the exhaust. The infection probability based on the tracer gas concentration in the inhaled air of the exposed manikin was up to 65% higher than the infection probability calculated by the Wells-Riley method, which assumes complete room air mixing.
The effect of air supply rate on indoor infection probability in mixing ventilation
Authors: Su Wei , Yang Bin
Published: August 2022

SARS-Cov-2 has caused enormous damage to society and put human health at a hazardous level. Optimizing air distribution patterns is one of the most useful manners to minimize the infection risk of susceptible individuals. Mixing ventilation is widely used, but the effect of air supply rate on indoor infection probability has not been studied yet. Three air supply rates, including 576, 864 and 1152 m3/h were adopted to study this problem in a simulated room, with dimensions of 5m×5m×2.7m. The Computational Fluid Dynamics (CFD) method was used to consider indoor flow fields under three cases.

The infection probability was calculated by the revised Wells-Riley model. The results showed that the overall infection probability decreased as the air supply rate increased. Meanwhile, the infectious air exhaled by the infector would flow along with the supply airflow in a certain direction, resulting in a nonuniform distribution of infection probability in the room. Increasing air supply rate and optimizing workstation layout may be two useful manners to reduce infection probability in mixing ventilation rooms.
Assessment on the expectation for built environment usage and its influencing factors during the pandemic
Authors: Jiao Jiao , Liu Jianlin , Xie Yongxin
Published: August 2022

A vital question of how citizens expect to use the built environment is not fully addressed. This study aims to contribute to this question from the indoor and outdoor usage expectation. The potential influencing factors are examined via survey along with the meteorological data obtained from weather bureau. This study provides that the current location and the duration of indoor-stay serve as the influencing factors of the indoor and outdoor usage expectation. The indoor and outdoor usage expectation has an obvious influence on the thermal sensitivity of thermal environment. People who expect to use the outdoor environment showed the least thermal sensitivity, 42.3% weaker than those who do not expect to use. These findings help providing further understanding of the citizens’ thermal expectation and their thermal responses during the post-pandemic period.
Numerical Study of the Influence of Bedside Curtains on Human Exhaled Contaminants Distribution in a Two-bed Ward
Authors: Gong Jiafu , Chen Min
Published: August 2022

Bedside curtains are widely used in multi-bed wards to protect the privacy of patients. However, it may change the distribution of airflow and lead to cross infection. A numerical approach is applied to investigate contaminant distribution in a two-bed ward with downward ventilation. Tracer gas such as CO2 is applied to simulate the exhaled contaminants by two lying patients. The contaminant concentration distributions with and without bedside curtains are compared. The results show that bedside curtains have great impacts on the airflow throughout the ward, which leads to a significant difference in the trajectory of expiratory flow between patients. Without curtains, the supply air can reach almost all the ward except the aera bed 1. Curtains mounted without grille almost completely block the airflow to bed 1, most of the airflow along with the continuous air supply of the whole ward without passing through bed 1, while the exhaled flow of patient 2 is blocked by the curtain, which cannot be directly returned to the outlet, but is affected by the eddy current caused by fresh air and spread to the end of bed 2. The expiratory airflow of patient 1 will also spread to the whole ward, which will lead to cross-infection. Most of the supply air can pass through the grille on the upper part of the curtain to reach the upper space of bed 1, and a small part of the airflow is blocked and bounced by the curtain. The exhaled flow of patient 2 follows the bounced air back to the faces of patient 2, and then follows the supply air throughout the whole ward. Expiratory airflow of patient 1 moves upward at first and then spread to the whole ward along with the supply airflow. The study can provide a reference for wards to construct a healthy indoor environment.
Study on acquired infection of patients in waiting space of fever clinic
Authors: Liu Shuo , Wang Ying , Lu Yiran , Li Yifan , Wang Yi , Liu Li
Published: August 2022

Since the COVID-19 outbreak, high numbers of patients with respiratory symptoms flock to fever clinic, cause overcrowding. Due to relatively densely populated space and the existing ventilation strategy, lead to space environment bearing capacity lose efficacy. The patients in waiting space are faced a high risk of cross infection. Thus, it must be strictly controlling the personnel density and fresh air dilution level, prevent SARS-COV-2 transmission though aerosols. This study takes the fever clinic of 3A Grade Hospital case, based on the monitoring results of CO2 concentration and the transport of exhaled pathogenic aerosols, predict the waiting patient’s cross infection risk in crowded space. Computational fluid dynamics simulations and agent social force behaviour model were used. When the number of fever clinic reaches the upper limit of theoretical capacity, under the three ventilation types, average exposure risk in different areas of waiting space were studied. Results show that when the infector is located at the front of the waiting corridor (upwind direction of natural ventilation), when there is only natural ventilation, the difference of average intake fraction in the three areas of waiting space is small, that is, the correlation between distance and exposure is small. Our results also show that when ceiling air conditioner ventilation and natural ventilation are coupled, the dilution effect is significantly lower than that of natural ventilation in the front and rear area, and higher than only run mechanical ventilation.
Characteristics of aerosol dispersion in isolation wards under the mixing and perforated ceiling air supplying ventilation strategies
Authors: Niu Guang , Wang Feifei , Yang Hanlin , Xu Xinhua
Published: August 2022

In this paper, a numerical simulation study of the airflow organization and aerosol diffusion process in a typical isolation ward is carried out to explore the effects of mixing ventilation (MV) and perforated ceiling air supplying ventilation (PCV) strategies on aerosol diffusion and deposition in the ward. Furthermore, the effects of aerosol particle size (5μm, 20μm) and aperture ratio of perforated plate on aerosol distribution were studied in this paper. The simulation results show that: compared with the MV case, PCV results in a more uniform flow field and temperature field in the ward, and can increase the discharge speed of aerosol particles, which can effectively reduce the risk of cross-infection among medical staff; by counting the proportion of aerosol deposition, discharge and suspension on each surface in the ward, it can be found that small-sized aerosol particles (5μm) are more likely to diffuse and suspend in the ward under the influence of the flow field, while large-sized aerosol particles (20μm) are more likely to be deposited on the ground and on the bed under the influence of gravity; when using PCV, reducing the porosity of perforated plate can accelerate the deposition and discharge of aerosol particles, reduce the suspension of particles in the ward, and reduce the risk of virus infection in the air．