Adaptive-rational thermal comfort model: Adaptive predicted mean vote with variable adaptive coefficient

Transmission mitigation of COVID-19: Exhaled contaminants removal and energy saving in densely occupied space by impinging jet ventilation

The pandemic of COVID-19 and its transmission ability raise much attention to ventilation design as indoor-transmission outstrips outdoor-transmission. Impinging jet ventilation (IJV) systems might be promising to ventilate densely occupied large spaces due to their high jet momentum. However, their performances in densely occupied spaces have rarely been explored. This study proposes a modified IJV system and evaluates its performance numerically in a densely occupied classroom mockup. A new assessment formula is also proposed to evaluate the nonuniformity of target species CO₂. The infector is assumed as the manikin with the lowest tracer gas concentration in the head region. The main results include: a) Indoor air quality (IAQ) in the classroom is improved significantly compared with a mixing ventilation system, i.e., averaged CO₂ in the occupied zone (OZ) is reduced from 1287 ppm to 1078 ppm, the OZ-averaged mean age of air is reduced from 439 s to 177 s; b) The mean infection probability is reduced from 0.047% to 0.027% with an infector, and from 0.035% to 0.024% with another infector; c) Cooling coil load is reduced by around 21.0%; d) Overall evaluation indices meet the requirements for comfortable environments, i.e., the temperature difference between head and ankle is within 3 °C and the OZ-averaged predictive mean vote is in the range of -0.5 - 0.5; e) Thermal comfort level and uniformity are decreased, e.g., overcooling near diffuser at ankle level. Summarily, the target system effectively improves IAQ, reduces exhaled-contaminant concentration in head regions, and saves energy as well.

Outdoor thermal stress changes in South Korea: Increasing inter-annual variability induced by different trends of heat and cold stresses

Changes of thermal environment can lead to unfavorable impacts such as a decrease of thermal stratification, increase of energy consumption, and increase of thermal health risk. Investigating changes in outdoor thermal environments can provide meaningful information for addressing economic and social issues and related challenges. In this study, thermal environment changes in South Korea were investigated using a nonstationary two-component Gaussian mixture model (NSGMM) for air temperature and two thermal comfort indices. For this, the perceived temperature (PT) and universal thermal climate index (UTCI) were employed as the thermal comfort index. Thermal comfort indices were computed using observed meteorological data at 26 weather stations for 37 years in South Korea. Meanwhile, trends of thermal comforts in the warm and cool seasons were simultaneously modeled by the NSGMM. The results indicate significant increasing trends in thermal comfort indices for South Korea. The increasing trends in thermal comfort indices both the warm and cool seasons were detected while the magnitudes of the trends are significantly different. This difference between the magnitude of trends led to an increase in mean and inter-annual variability of thermal comfort indices based on PT, while an increase of mean and decrease of inter-annual variability were observed based on the UTCI. Moreover, the annual proportion of the category referring to days in comfort based on the results of PT has decreased due to the different trends of thermal comfort indices in the warm and cool seasons. This decrease may lead to an increase of thermal health risk that is larger than what would be expected from the results considering the increasing trend of the annual mean temperature in South Korea. From this result, it can be inferred that the thermal health risk in South Korea may be more adverse than what we originally expected from the current temperature trend.

Comprehensive Assessment of Thermal Comfort and Indoor Environment of Traditional Historic Stilt House, a Case of Dong Minority Dwelling, China

The stilt house is one of the most representative of Chinese architecture among national minority traditional dwellings, most of which are located in mountainous regions whose climate is characterized by hot summers and cold winters. Moreover, it is widely distributed in Southeast Asian countries, such as Thailand, Laos, Cambodia, etc., as well as tropics like Hawaii, Guam. These kinds of dwellings have unique architectural aesthetics as well as high climate adaptability. However, because of their remote locations and rapid disappearance in urbanization, few studies have focused on their real indoor environment and thermal comfort. More studies were engaged in their architectural aesthetics and space patterns. In this study, based on the measurement and evaluation of residential natural lighting, ventilation, air quality, and thermal comfort in traditional stilt Dong village houses, the air temperature, humidity, CO2 and PM2.5 concentrations, wind speed, direction, and other variables are monitored and analyzed. Results show that the inhabitants have a higher thermal comfort adaptation than urban residents under natural ventilation. Meanwhile, the humidity of Dong stilt dwelling can reach a satisfactory level within 24 h except for the morning period. The satisfaction of the acoustic environment needs to be improved via reasonable structural maintenance.

Extended predicted mean vote of thermal adaptations reinforced around thermal neutrality

Predicted mean vote (PMV) is a prevailing thermal comfort model adopted by thermal comfort standards. To extend its ability in explaining thermal adaptations, the PMV is multiplied by an extension factor. However, the original extended PMV (ePMV) cannot account for thermal adaptations around thermal neutrality, resulting in deviation around thermal neutrality, therefore, is unable to predict thermal sensation around thermal neutrality accurately. Given the unusual importance of thermal sensation around thermal neutrality for energy-efficient provision of indoor thermal comfort, this study modifies the ePMV to reinforce thermal adaptations around thermal neutrality by adding a thermal neutrality factor. The modified ePMV is quantified by explicitly expressing the extension factor and the thermal neutrality factor as functions of field datasets of the PMV, thermal sensation vote (TSV), and ambient temperature. The modified ePMV is validated to improve thermal sensation prediction effectively (by up to 73%), particularly for prediction around thermal neutrality with the TSV between -0.5 and 0.5, by mitigating deviation around thermal neutrality for different types of buildings under various climate conditions around the world. Moreover, the modified ePMV is explicitly formulated and, therefore, convenient for practical applications.