The effect of oxygen supply and oxygen distribution on single-head tunnel with different altitudes under mixed ventilation

Hypoxia plays a major role in limiting the construction of the high-altitude mine. Understanding the effect and the distribution of diffused oxygen supply at different altitudes is the premise for the design of a mine with oxygen supply system and the full utilization of oxygen resources. For the optimal design of an oxygen supply mode and ventilation system, a multi-component fluid model of the diffused oxygen supply of a single-head tunnel was developed. This study reveals the variation law of the average oxygen mass fraction at different altitudes. The relationship between the distance from the heading face and the oxygen mass fraction at each altitude was fitted. The results show that the distribution of oxygen mass fraction in a single head tunnel at different altitudes presents a similar trend of increasing first and then decline. In addition, the change of the average oxygen mass fraction with the increase of altitude is not linear, and the dispersion loss is larger in high-altitude areas. The largest oxygen enrichment area is distributed at the altitudes of 4000–4500 m. This study provides theoretical support for improving the hypoxic environment of high-altitude metal mines excavation work.

How community medical facilities can promote resilient community constructions under the background of pandemics

Nowadays, urban and community resilience have become the core issues of urban theoretical research and construction practices. While there are many studies on climate change, natural hazards and environmental pollution, relatively less attention has been paid to public and human health. However, the current COVID-19 pandemic, which is a major global public health crisis, is posing severe challenges to the resilience of cities and communities in the context of high-mobility, high-density and high-intensity, as well as expands the connotation of community resilience to public health. To compensate for the lack of current research, this study examined the characteristics of community medical facilities in response to pandemics at urban, community and individual multi-spatial scales based on a thorough review of current research and relevant practice. It also emphasized the significant role played by community medical facilities in improving resilient community constructions in the face of large-scale public health emergencies. These characteristics were fully utilized to explore ways to build and govern the ‘resilience' of communities in the future, help people to survive better as well as develop in complex and changeable external environments.

Guidance to assess ventilation performance of a classroom based on CO2 monitoring

Since the COVID-19 pandemic, the ventilation of school buildings has attracted considerable attention from the general public and researchers. However, guidance to assess the ventilation performance in classrooms, especially during a pandemic, is still lacking. Therefore, aiming to fill this gap, this study conducted a full-scale laboratory study to monitor the CO2 concentrations at 18 locations in a classroom setting under four different ventilation regimes. Additionally, a field study was carried out in two Dutch secondary schools to monitor the CO2 concentrations in the real classrooms with different ventilation regimes. Both the laboratory and field study findings showed that CO2 concentrations varied a lot between different locations in the same room, especially under natural ventilation conditions. The outcome demonstrates the need of monitoring the CO2 concentration at more than one location in a classroom. Moreover, the monitored CO2 concentration patterns for different ventilation regimes were used to determine the most representative location for CO2 monitoring in classrooms. For naturally ventilated classrooms, the location on the wall opposite to windows and the location on the front wall (nearby the teacher) were recommended. For mechanically ventilated classrooms, one measurement location seemed enough because CO2 was well-mixed under this ventilation regime.

Source apportionment and health risk assessment of indoor volatile organic compounds

In extremely cold areas with long winter months and exceptionally cold weather, classrooms are inadequately ventilated, resulting in the continuous accumulation of indoor air pollutants that may endanger human health. This article uses adsorption tube sampling-thermal desorption-gas chromatography mass spectrometry to analyze the type and concentration of volatile organic compounds (VOCs) in the classroom. The source analysis and health risk assessment were performed, and the real-time concentration of total volatile organic compounds (TVOC) was computed using the multifunctional ventilation. The result shows that the air in the classroom contains 25 kinds of VOCs. Among them, the carcinogenic risk value of seven kinds of VOCs (3.40 × 10-5) exceeds the acceptable risk value (1 × 10-6) given by the U.S. Environmental Protection Agency (US EPA). There are 17 kinds of VOCs that pose a certain non-carcinogenic risk to the human body. After quantitative analysis by the principal component analysis (PCA) and the characteristic quantity concentration ratio method, human activities, furnishings, outdoor penetration, etc., were found to be main sources of VOCs in the classroom. In addition, TVOC concentration is directly proportional to class time. In winter, classrooms in severely cold areas must take necessary measures to reduce the concentration of VOCs and ensure students' health.

Measurement of indoor environmental parameters and analysis of the condensation phenomenon in urban utility tunnels

Condensation is a major issue in the safe operation of utility tunnels. To address the condensation problem, the indoor air temperature, relative humidity (RH) and surface temperature in an urban utility tunnel in Jining were continuously measured, and the condensation conditions were surveyed and analysed. The results indicated that under natural ventilation conditions, the air temperature in the comprehensive cabin varied from 23.4°C to 24.5°C, the RH fluctuated between 86.4% and 95.3%, and the corresponding air dew point temperature (DPT) remained in the range of 22.2°C–22.9°C. The surface temperature of the water supply pipeline ranged from 17.8°C to 18.5°C, which was far lower than the DPT in the tunnel, resulting in serious condensation. A water supply pipeline with an anti-condensation design was developed based on environmental test data. A 25-mm-thick rubber plastic sponge insulation layer was used to thermally insulate the water supply pipeline, preventing further dew condensation. Furthermore, mechanical ventilation had little effect on reducing the RH in the tunnel and may actually cause dew condensation; therefore, a ventilation control mode was proposed in this study. These results are expected to provide basic data for further research and reference for the safe management of utility tunnels.

Impacts of light direction and window properties on students’ perceptual evaluations in design studios

This study aimed to determine how light direction, window proximity and window dimensions could affect students' perceptual evaluations in design studios. The design studios of the Nuh Naci Yazgan University in Kayseri were selected as the research setting. The ‘semantic differential scale’ composed of 10 adjective pairs was used for determining subjects’ perceptual evaluations of design studios having two different window dimensions. According to the results obtained, when making drawings, right-handed students who received light from a window on the left side were determined to perceive the physical environmental factors of design studios more positively compared to students who received light from a window on the right side. In addition, students sitting near a window in design studios were observed to generally perceive the physical environmental factors more positively than those sitting in the middle close to the window, in the middle away from the window and inside. Furthermore, students who sat in an area with floor to ceiling window were determined to perceive the place more positively compared to those who sat in an area with parapet to ceiling window. These results generally confirmed that light direction, window proximity and window dimensions in design studios are effective on students’ perceptual evaluations.

The importance of the calculation of angle factors to determine the mean radiant temperature in temperate climate zone: A university office building case

Thermal comfort depends on four environmental (air velocity, relative humidity, air temperature, mean radiant temperature) and two personal (clothing insulation and metabolic rate) parameters. Among all parameters, the mean radiant temperature (tr) is the most problematic variable in thermal comfort studies due to its complexity. Measurement methods, calculation methods and assumptions are mostly used to obtain the tr. Researchers mainly prefer to obtain the tr via measurement methods or assumptions due to their easiness compared to the calculation methods. Besides, some researchers use constant values of angle factors in calculation methods. However, using constant values is not proper for every indoor environment, and it causes wrong estimations in the tr and thus the thermal comfort. This paper gives the importance of calculation of angle factors, with an example of a university office building in temperate climate zone, according to the ISO 7726. The angle factors of the room were calculated for a seated occupant from the centre of gravity in three different locations and compared with the constant angle factors. The results indicate that a significant difference (MAPE of 1.02) was found in the tr values, which were obtained by calculation of constant values of angle factors.

Annual thermal performance assessment of a regenerative evaporative cooling system under different climate conditions in Mexico

A numerical heat and mass transfer model with thermophysical properties dependent on the temperature, humidity ratio and atmospheric pressure was developed. The numerical model was verified and validated against literature, and it showed good agreements. The pseudo-transient model provides a low-cost computational tool to evaluate the potential and performance of a dew point evaporative cooling system for a wide range of extreme climate conditions (BWh, BSh, Cw and Aw from Köppen classification). A parametric analysis of different operational and design conditions in the evaporative cooler was conducted. Results show that there is an optimal channel length for given climatic conditions. The Dew-point evaporative cooling (DPEC) system showed that the best thermal performance corresponds to the climate very arid (Hermosillo – BWh) with 4018 comfort hours (83.1%) followed by the climate arid (Monterrey – BSh) with 3470 comfort hours (90.9%), the mild climate (Puebla – Cw) with 295 comfort hours (100%) and the warm climate (Cancun – Aw) with 3452 comfort hours (62.3%). Finally, an engineering correlation for constant atmospheric pressure and channel length was obtained ([Formula: see text] of 93%).