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Abstract: An extended Gebhart–Block model for large space buildings is proposed in this paper, which is used to predict the vertical temperature distribution of hybrid ventilation. Natural ventilation coupled with air-conditioning is described with a mathematical model. The indoor thermal environment formed by the air-conditioning and the natural ventilation can also be conducted for the potential analysis and optimal use of the natural ventilation. Experiments were carried out in an atrium building in Shanghai Research Institute of Building Sciences. This paper describes aforementioned model, and it is found that the calculation results implying this model agree well with the measurement data. [Copyright &y& Elsevier]

• Ventilation rate and arrangement are crucial to prevent airborne disease in healthcare facilities. • Local ventilation is practical for supply fresh air and diluting contaminants in high-risk areas. • Microplastics emerged as potential virus carriers in indoor environments, warrant further investigations. The prevalence and transmission of airborne infections pose significant challenges to public health, leading to consequential negative impacts. Ventilation strategies are crucial in mitigating airborne infections in healthcare settings, preventing the spread of infectious diseases, thus protecting patients and healthcare workers. While individual studies have explored various aspects of ventilation in healthcare settings, a synthesized overview of the current state of knowledge is lacking. Therefore, this study attempts to bridge the gap by conducting a review and bibliometric analysis based on 198 papers published within the recent decades (1993–2022). The findings will provide a holistic understanding on the innovative interventions and identify areas for future research, thereby contributing to the development of effective guidelines for controlling airborne infections. The co-authorship analysis revealed that China emerged as the main contributor in the current research field due to the keen interest of researchers and the substantial financial support provided by funding agencies. The keyword co-occurrence analysis identified three primary research hotspots within the field, (i) the optimized ventilation strategies for combating airborne infection, (ii) the transition towards the application of computational fluid dynamics (CFD) in analyzing airflow patterns, and, (iii) the characteristics of airborne particles and their impact on infection transmission. The present review highlights the significance of local ventilation as an additional measure to the main ventilation system for enhanced dilution of contaminants in high-risk areas. The transition towards dynamic airflow analysis considered human movement's effect, allowing for more precise assessments and tailored ventilation strategies optimization. The review also underscores the emerging concern of microplastic as an indoor contaminant with potential implications as a virus carrier, emphasizing further research on its behavior and impact on airborne infection transmission. [ABSTRACT FROM AUTHOR]

Abstract: Urban heat island can significantly increase the demand for cooling of buildings in cities. This paper investigates one of the main causes of the urban heat island phenomenon, i.e. reduced city ventilation. Two simple Hong Kong city models with relatively complex terrain were considered here under different atmospheric conditions. A 3D RNG k–ɛ turbulence model was used for modeling turbulence effects. The simulation results showed that the influence of thermal stratification can be significant on city ventilation driven partially by thermal buoyancy. When the wind speed is relatively large, the impact of thermal stratification on air flow in city street canyons is minor. When the wind speed is small relative to the buoyancy force, the airflow in the street canyons is dependent on thermal stratification. When there is an adverse vertical temperature gradient, the greater the instability, the stronger the vertical mixing and the greater the flow rate caused by turbulence. The heat and pollutants can easily accumulate under stable atmospheric conditions when there is only a weak background wind or none at all. [Copyright &y& Elsevier]

Abstract: Energy consumption is an important issue in China. In heating, ventilation and air conditioning (HVAC) systems, more and more commercial buildings use air-to-air heat recovery ventilators as energy saving units for recovering heat from the exhaust air in ventilation systems in current years. In the present paper, critical temperatures of air-to-air heat recovery systems for supermarkets in winter are recommended and discussed for the four cities in different climate zones of China. The analysis shows that the temperature of fresh air in winter can be categorized into three regions, i.e., recovery region, transition region and impermissible recovery region. The results also indicate that the latent heat recovery is not suitable for ventilation energy savings in supermarkets in winter. Meanwhile, the applicability of sensible heat recovery in supermarkets depends on outdoor climate and fresh air flow rate. If a variable rotational speed fan is used to introduce fresh air into the building, heat recovery does always function as planned in winter for all the selected cities except Guangzhou, and most values of the COP are much higher than 2.5. Otherwise, there is the risk of negative impact on building energy savings in all cities except Harbin. [ABSTRACT FROM AUTHOR]

Thermal comfort evaluations in the built environment are essential to occupant's satisfaction and also building energy consumption. Traditionally, thermal comfort has been assessed by Fanger's PMV model that was developed based on extensive laboratory tests. However, it's been found that PMV predictions are not good in field studies, especially in buildings with natural ventilation. In this paper, machine learning (ML) algorithms were used to predicted occupants' thermal comfort votes (TCV) and thermal sensation votes (TSV), using 5512 sets of thermal comfort data collected in naturally ventilated residential buildings in fourteen cities in China. Environmental parameters, personal parameters, climatic types, and adaptive control measures were considered and used as input parameters for the ML model. It was found that environmental parameters (both outdoors and indoors), personal parameters (metabolic rate and clothing insulation), and climatic types all significant affect both TCV and TSV, while adaptive control measures only affect TSV but not TCV. Comparing with established models (PMV, ePMV and aPMV), the ML models had smaller errors in predicting TSV and TCV. Based on these results, we suggest that the ML, especially ANNs model was reliable in predicting occupants' TCV and TSV in naturally ventilated residential buildings, and performed better than traditional thermal balance based models. Moreover, using the new model, we found that acceptable temperature ranges in naturally ventilated buildings were far wider than the ASHRAE adaptive comfort zone, suggesting that appropriate models should be established based on local data. [ABSTRACT FROM AUTHOR]