Thermal Environment Research Articles

Field Investigation on the Thermal Environment and Comfort of People Exercising in a Fitness Center

A favorable thermal environment in fitness centers is important to attract more members and is beneficial to the health of exercising people. The purpose of this study was to research the actual thermal environment of a typical fitness center in different seasons and the thermal requirement of exercising people. A field investigation covering winter, spring, and summer was conducted. The environmental parameters were measured. Subjective questionnaires involving individual information, clothing insulation, thermal sensation, etc., were collected. Participants’ heart rates were tested to estimate their metabolic rate (MR). A total of 740 valid questionnaires were collected. The results showed that a scissors gap existed between the predictive mean vote (PMV) and the thermal sensation vote (TSV) for the exercising people. For the higher MR group, there was a separation between the TSV and thermal preference vote, e.g., most participants would not prefer to cooler or warmer thermal environment when they felt hot or cold. The CO2 concentration changed greatly among seasons and the distribution in the fitness center was not uniform. With mechanical ventilation, the CO2 concentration in summer was the lowest. In other seasons it became much higher due to limited natural ventilation. However, subjective response to indoor air quality showed no significant difference among seasons. The participants felt more satisfied to the overall thermal environment in the transition season. The results can be referenced in the thermal environment management in fitness centers during seasonal changes.

Green space-building integration for Urban Heat Island mitigation: Insights from Beijing's fifth ring road district

In this research, we delve into the complex arrangement of urban landscapes, where green spaces and buildings are not merely co-existing but are interwoven into a cohesive fabric that shapes the thermal environment. Our approach transcends the conventional methods of analysis, which typically isolate the roles of greenery or built environments. Instead, we adopt a synergistic perspective that recognizes the collective influence of these landscape constituents on the urban thermal pattern. Key insights are: (1) A linear decrease in average land surface temperature with increasing green space coverage is observed. However, substantial temperature variations (up to 8 °C) within the same coverage interval highlight the significant impact of built-up pattern on thermal conditions; (2) High Building Height and Floor Area Ratio, and low Building Coverage Ratio and Sky View Factor, are linked to cooler temperatures in areas with up to 50 % green space; (3) The study suggests that low-temperature areas can inform the adjustment of built-up patterns in high-temperature areas, offering a strategy for thermal environment optimization within specific green space coverage intervals. This research contributes insights into the integrated planning of green spaces and buildings, with implications for urban development and renewal initiatives aiming to enhance the urban thermal environment.

Construction of Al/Ti₃C₂Tₓ composites via electrostatic self–assembly for visible–infrared camouflage applications

Attaining the equilibrium of subdued luminance, low visible light reflectance, and high infrared reflectance constitutes a formidable challenge in the realm of visible–infrared camouflage. Here, an electrostatic self–assembly method was proposed to fabricate the Al/Ti₃C₂Tₓ (AT) composite. The synergy between Ti3C2Tx’s favorable optical properties and significant conductivity of Al powder grants the AT composite excellent visible–infrared camouflage capabilities. At a mass ratio of 4:1 for Al powder to Ti3C2Tx (AT–4), the composite displays a gray coloration, achieving a 40 % reduction in visible light reflectance and an emissivity value of 0.28. Such properties enable the AT–4 composite to effectively blend into various thermal environments, showcasing its superior infrared camouflage capabilities. Additionally, incorporating Ti3C2Tx layers significantly boosts the local electric field in the composite, enhancing photon–material interactions and consequently reducing its visible light reflectance. This work offers valuable insights for the development of advanced materials with integrated visible–infrared camouflage capabilities.

Resiliency evaluation of sheltering in a net-zero energy house during summer power outage

This study examines the growing issue of power outages caused by natural disasters and proposes the use of net-zero energy houses (ZEH) as a safe alternative to traditional shelters. A ZEH, equipped with an independent energy system, can maintain essential living standards such as thermal comfort and 24-hour air conditioning during a summer power outage, reducing the risk of heatstroke. The research tested a ZEH in Japan, confirming its ability to support critical household appliances like refrigerators, lighting, and water heaters for up to 72 h. This demonstrates the ZEH's potential for offering safe, comfortable shelter during emergencies while addressing problems like poor sanitation and lack of privacy found in typical shelters. The experimental ZEH is located in Shizuoka, Japan, is a steel structure, and has a floor area of 110.94 m2 and overall heat transmission coefficient (UA) of 0.48 W/m2·K. The ZEH was equipped with a 5.1 kW photovoltaic system and 5.6/11.2 kWh storage battery (BT), which produced an output of up to 2.0/4.0 kVA. A ZEH with a 5.6 kWh BT can provide for ventilation and living/dining room/kitchen air conditioning (AC), refrigerator, television, lighting, mobile phone charging, rice cooker, microwave, electric kettle, and heat pump water heater during a 72-h power outage. The ZEH with a 11.2 kWh BT can also provide bedroom AC and high-load home appliances for lunch and dinner, in addition to a 5.6 kWh BT. The use of AC in a self-supporting circuit maintained the thermal environment at a low heat stroke risk.

Energy retrofits: Factors affecting a just transition to better indoor air quality

In comparison with other European countries, Ireland has a disproportionately high number of poorly performing energy-inefficient buildings. Consequently, Ireland has one of the most ambitious energy retrofit programmes in Europe. The aim of this study was to evaluate the impact of deep energy renovation measures i.e. (replacement of heating system and upgrade to building envelope) on indoor air quality, thermal comfort and ventilation in a sample of primarily social housing in Ireland. A mixed methods approach including measurement of indoor air quality and a thermal comfort questionnaire survey was employed. Indoor concentration measurements of PM2.5, carbon dioxide, formaldehyde, and radon along with measurements of air temperature and relative humidity were made (N=14). Occupants (n=56) completed a thermal comfort questionnaire survey pre- and post-retrofit. Data collection ran from autumn 2020 until autumn 2023.Thermal comfort improved post-retrofit along with occupant satisfaction with the indoor thermal environment and heating-systems. Post-retrofit, higher bedroom CO2, and higher PM2.5 concentrations were recorded in both living areas and bedrooms. Occupant behaviours e.g. blocking wall vents were significant predictors of poorer ventilation while smoking indoors was related to higher concentrations of PM2.5. In general, homes that had mechanical ventilation systems installed were better ventilated. Underventilation, as indicated by visible condensation or mould was observed in half of the social homes surveyed and reported by questionnaire respondents (26 %). Tailored communications to occupants regarding the important role of ventilation and indoor air quality is required as part of retrofit to optimise impacts on IEQ.

Optimization of indoor thermal environment for high-altitude sentry buildings with attached ventilation based on proper orthogonal decomposition

The low-oxygen and severe cold climate characteristics of high-altitude regions significantly impact individuals' physiological health and thermal comfort inside buildings, especially for sentry buildings where the enclosure is fully exposed to the outdoors. This study aimed to optimize the indoor environment for high-altitude sentry buildings with attached ventilation. Firstly, the optimal location of exhaust outlets and oxygen sources in the heating mode of high-altitude sentry buildings was studied, and it showed high performance in terms of thermal comfort and energy efficiency. Additionally, the POD method and interpolation methods were applied to expand the sample dataset and identify the optimal combination of attached ventilation parameters and oxygen supply concentration, creating a comfortable, oxygen-enriched environment within the sentry buildings while also considering energy efficiency. The results indicate that when the optimization objective is weighted towards thermal comfort, the percentage of dissatisfied (PD) and the draught rate (DR) values under the optimal scheme are reduced by 82 % and 46.6 %, respectively, compared to previous studies. However, when the emphasis is on energy efficiency in environmental optimization, the air supply energy under the optimal scheme has a 64.4 % reduction compared to previous research results. When considering both optimization objectives simultaneously, the PD and DR values under the optimal scheme are reduced by 35.9 % and 96.9 %, respectively, compared to previous research results. These results demonstrate significant improvements in both thermal comfort and energy efficiency relative to our previous study.

Comparative study of outdoor thermal comfort: Residents vs. tourists at Xi'an Ming Dynasty Ancient city wall scenic area

This study explores the thermal perceptions and comfort of residents and tourists at the Xi'an Ming Dynasty Ancient City Wall Scenic Area, addressing a gap in comparative outdoor thermal comfort studies in historical settings. Meteorological measurements and questionnaires collected between July 2019 and March 2021 analyze physical, individual, social, and psychological factors influencing thermal sensation, comfort, and acceptability across seasons. The RayMan model calculates Physiological Equivalent Temperature (PET), with data analyzed using SPSS 27.0. Results show Neutral PET (NPET) values of 17.1 °C for residents and 18.6 °C for tourists, and Preferred PET (PPET) values of 18.4 °C and 20.8 °C, respectively. Thermal Acceptability Ranges (TAR) are 13.5 °C–26.7 °C for residents and 15 °C–24.1 °C for tourists. Whether the measurement space contains water sources significantly affects temperature and humidity, while vegetation impacts wind speed. Physical factors predominantly affect perceptions, with individual factors becoming more important for tourists in winter. The findings provide insights for optimizing the thermal environment in scenic open spaces to enhance the comfort of both residents and tourists.

Identification of Thermal Environment Networks in the Wanjiang Urban Agglomeration Based on MSPA and Circuit Theory

Identification of Thermal Environment Networks in the Wanjiang Urban Agglomeration Based on MSPA and Circuit Theory

Sustainability Optimization Method of Built Environment with Integrated Physical Environment and Virtual Perception Simulation: A Case Study of Campus Open Space

High-quality built environments significantly enhance residents’ health, urban livability, and sustainability. However, the lack of precise pre-evaluation of designs and user perceptions during the design phase often results in suboptimal improvements. This study proposes a method for evaluating and optimizing design schemes based on multidimensional physical environment simulations and virtual perception, using a university campus as a case study. Initially, we establish simulation models for sound, wind, thermal, and light environments and analyze the current state of virtual perception in the campus environment. Subsequently, we integrate the evaluation results of the physical environment and virtual perception to identify three priority intervention areas and develop corresponding design strategies. Finally, we reapply the method for pre-evaluation of the design schemes and further optimize the designs. The results show that the optimized schemes receive positive feedback in virtual perception evaluations. This study leverages the combined use of multidimensional physical environment simulations and VR technology to create an immersive virtual environment with measurable physical perception experiences, providing a new approach for guiding the sustainability of built environments.

Thermal Comfort and Restorative Benefits of Waterfront Green Spaces for College Students in Hot and Humid Regions

Global climate change presents a serious threat to the sustainable development of human society, highlighting the urgent need to develop effective adaptation strategies to mitigate the impact of climate-related disasters. Campus waterfront green spaces, integral to the blue-green infrastructure, have been demonstrated to facilitate stress recovery. However, in hot and humid regions, severe outdoor thermal conditions may impair students’ mental and physical health and cognitive function, leading to symptoms such as increased stress, anxiety, and depression. This study examined the influence of outdoor thermal environments on health recovery by selecting three different waterfront green spaces in this climate: Space A (medium water body, sky view factor (SVF) = 0.228), Space B (large water body, SVF = 0.808), and Space C (small water body, SVF = 0.292). The volunteers’ thermal comfort and the restorative benefits of these spaces were evaluated via the perceived restorativeness scale (PRS), heart rate (HR), and electrodermal activity (EDA). We found variations in the neutral physiological equivalent temperature (PET) across the spaces, with values of 28.1 °C (A), 28.9 °C (B), and 29.1 °C (C). The lowest skin conductance recovery rate (RSC) at 0.8811 was observed in Space B, suggesting suboptimal physiological recovery, despite higher scores in psychological recovery (fascination) at 15.23. The level of thermal comfort in this hot and humid region showed a negative correlation with the overall PRS score, the “being away” dimension, and heart rate recovery (RHR). At a lightly warm stress level, where PET increased from 31.0 to 35.7 °C, RSC peaked between 1.45 and 1.53 across all spaces. These insights provide guidance for urban designers and planners in creating waterfront green space designs that can improve the urban microclimate and promote thermal health, achieving sustainable health.

Impact of Loss Mechanisms on Linear Spectra of Excitonic and Polaritonic Aggregates.

The presence of loss mechanisms governed by empirical timescales can profoundly affect the dynamics in molecular systems, leading to changes in their spectra. However, incorporation of these effects along with the system's interaction with the thermal dissipative environments proves to be challenging. In this work, we demonstrate the possibility of utilizing the recently developed path integral Lindblad dynamics (PILD) method to study the linear spectra of molecular aggregates. PILD presents a uniquely powerful simulation technique for retaining the effects of the vibrations in a numerically exact manner through the Feynman-Vernon influence functional while incorporating the effects of losses in an empirical manner using the Lindbald master equation. As illustrations of this technique, we provide examples taken from chiral excitonic and polaritonic aggregates for which we simulate both the absorption spectra and circular dichroism (CD) spectra. We demonstrate that the effect of loss on particular states can differ not just on the basis of the symmetries of the state but also on the basis of complicated "interactions" of the structured dissipative environments with the system and its loss mechanisms. Due to the different selection rules between the absorption and CD spectra and the relative intensities and broadening of the peaks, the two linear spectra together give an interesting insight into the contributions of the various eigenstates to the correlation functions. While the focus here is on linear spectroscopy, it should be possible in the future to use PILD to study multidimensional spectra under loss mechanisms as well.

The Mechanism of Street Spatial Form on Thermal Comfort from Urban Morphology and Human-Centered Perspectives: A Study Based on Multi-Source Data

The influence of street spatial form on thermal comfort from urban morphology and human-centered perspectives has been underexplored. This study, utilizing multi-source data and focusing on urban central districts, establishes a refined index system for street spatial form and a thermal comfort prediction model based on extreme gradient boosting (XGBoost) and Shapley additive explanations (SHAP). The results reveal the following: (1) Thermal comfort levels display spatial heterogeneity, with areas of thermal discomfort concentrated in commercial zones and plaza spaces. (2) Compared to the human-centered perspective, urban morphology indicators correlate strongly with thermal comfort. (3) The key factors influencing thermal comfort, in descending order of importance, are distance from green and blue infrastructure (GBI), tree visibility factor (TVF), street aspect ratio (H/W), orientation, functional diversity indices, and sky view factor. All but the TVF negatively correlates with thermal comfort. (4) In local analyses, the primary factors affecting thermal comfort vary across streets with different heat-risk levels. In high heat-risk streets, thermal comfort is mainly influenced by distance from GBI, H/W, and orientation, whereas in low heat-risk streets, vegetation-related factors dominate. These findings provide a new methodological approach for optimizing urban thermal environments from both urban and human perspectives, offering theoretical insights for creating more comfortable cities.

Modeling Urban Temperature Using Measurements from Mobile and Stationary Monitoring Stations

Heat waves are occurring more frequently worldwide as global warming continues, and urban heat islands can threaten conventional life in cities. Measuring, analyzing, and simulating weather data at fine spatial and temporal scales are essential to prevent and reduce the damage caused by extreme heat waves. In urban environments, handling complex micrometeorological situations using current meteorological stations and global simulation models (e.g., weather research forecasting models) is challenging. In this study, the thermal environments of urban areas were measured using a mobile meteorological measurement platform. Both mobile and stationary datasets were incorporated into the meteorological modeling process to simulate the spatial and temporal distribution of temperature. Additionally, various mobile observation implementation scenarios for temperature modeling were examined. We compared simulation combinations with the temperature field generated from the total dataset to obtain a better sampling campaign and properly incorporate mobile data scenarios. When collecting mobile data, it is important to consider spatial features to improve the efficiency of sampling programs. This can substantially reduce the cost of mobile data collection, together with the sensor error bound.

Driving factors of summer diurnal surface thermal environment in subtropical coastal cities: a Shenzhen case study

Driving factors of summer diurnal surface thermal environment in subtropical coastal cities: a Shenzhen case study

Fatigue life assessment and verification of turbine joints: current status and prospects

The research status of fatigue life assessment technology for turbine joint structures is introduced. The progress, shortcomings and development trends of existing research are discussed from the aspects of multi-field load analysis, crack initiation life assessment, crack propagation simulation and test technology. The evaluation methods of service life and damage tolerance of turbine joint structures are discussed in detail. The results show that the existing analysis and test methods can basically realize the fatigue life assessment of turbine joints, but due to various limitations, the engineering applicability needs to be improved urgently. Robust load reduction analysis methods, life assessment methods based on physical mechanisms and data-driven, load history-related crack propagation life assessment methods and test technologies under complex thermal environments are still needed to establish a fatigue life assessment and verification system for advanced aero-engine turbine joint structures.

An energy-environment coupled simulation framework for multi-scale and multi-facet evaluation of data center

This paper focuses on analyzing the thermal environment and optimizing energy consumption in data centers, which has largely omitted from previous studies. The thermal environmental of data centers is simulated and analyzed by utilizing the established “server-rack-room” multi-scale heat transfer numerical model. Based on this, the coupling simulation model of thermal environment and energy consumption in data centers is proposed to explore the relationship between them, and the corresponding optimization strategy is put forward. The energy consumption simulated by energy-environment coupled model and non-coupled model can reach a discrepancy of over 30 %, which indicates that the thermal environment impacts the power consumption of the data center significantly. Besides, the effect of several operational parameters of air conditioning system on the thermal environment and energy consumption of data center is analyzed. Through the particle swarm optimization algorithm, the optimal system parameters, which meet the requirements of thermal environment and lead to the lowest energy consumption, are found for typical cities in different climatic regions. The recommended settings include the supply air temperature of about 24 ∼ 26 ℃, the air supply volume of 8 m3/s, and the temperature difference of about 3.5 ℃ between the supply air temperature and the supply chilled water temperature. Under the optimized parameter setting, the highest temperature of server decreases to below 71 ℃, and the energy saving rate is more than 6 %.

Assessing the Impact of Vertical Greenery Systems on the Thermal Performance of Walls in Mediterranean Climates

This study investigates the impact of vertical greenery systems (VGSs) applied to several typical wall configurations on indoor thermal conditions in a building module situated in the Mediterranean climate of Catania, Italy. By means of dynamic simulations in TRNSYS vers.18, the research compares the thermal behavior of walls made of either hollow clay blocks (Poroton) or lava stone blocks against a lightweight wall setup already in place at the University of Catania. The primary focus is on evaluating the VGSs’ capability of reducing peak inner surface temperatures and moderating heat flux fluctuations entering the building. The findings indicate that adding an outer vertical greenery layer to heavyweight walls can decrease the peak inner surface temperature by up to 1.0 °C compared to the same bare wall. However, the greenery’s positive impact is less pronounced than in the case of the lightweight wall. This research underscores the potential of green facades in enhancing the indoor thermal environment in buildings in regions with climates like the Mediterranean one, providing valuable insights for sustainable building design and urban planning.

Multi-omics analysis reveal the fall armyworm Spodoptera frugiperda tolerate high temperature by mediating chitin-related genes

Climate change facilitates the rapid invasion of agricultural pests, threatening global food security. The fall armyworm Spodoptera frugiperda is a highly polyphagous migratory pest tolerant to high temperatures, allowing its proliferation in harsh thermal environments. We aimed to demonstrate mechanisms of its high-temperature tolerance, particularly transcriptional and metabolic regulation, which are poorly understood. To achieve the aim, we examined the impact and mechanism of heat events on S. frugiperda by using multiple approaches: ecological measurements, transcriptomics, metabolomics, RNAi, and CRISPR/Cas9 technology. We observed that several physiological indices (larval survival rate, larval period, pupation rate, pupal weight, eclosion rate, and average fecundity) decreased as the temperature increased, with the 32 °C treatment displaying a significant difference from the control group at 26 °C. Significantly upregulated expression of genes encoding endochitinase and chitin deacetylase was observed in the chitin-binding, extracellular region, and carbohydrate metabolic process GO terms of hemolymph, fat body, and brain, exhibiting a tissue-specific pattern. Significantly enriched pathways (e.g., cutin, suberin, and wax biosynthesis; oxidative phosphorylation and cofactor biosynthesis; diverse amino acid biosynthesis and degradation; carbon metabolism; and energy metabolism), all of which are essential for S. frugiperda larvae to tolerate temperature, were found in metabolites that were expressed differently. Successful RNA interference targeting of the three chitin-related genes reduced gene expression levels and larval survival rate. Knockout of the endochitinase gene by using the CRISPR/Cas9 system significantly reduced the relative gene expression and increased sensitivity to high-temperature exposure. On the basis of our findings, theoretical foundations for understanding the high-temperature tolerance of S. frugiperda populations and latent genetic control strategies were established.

Adaptive shading: How microclimates and surface types amplify tree cooling effects?

Shading is the most critical process in tree cooling. Although the influence of tree features on shade supply has been extensively studied, the efficiency of shade performance in diverse environments remains poorly understood. The latter is crucial, as urban areas are highly heterogeneous, and local microclimates and land cover heterogeneity are among the most perceptible and observable aspects. We randomly selected several typical tree patches in Beijing to explore whether and how tree-shade efficiency varies with these factors. We used temporal variations as a proxy to study the impact of microclimatic heterogeneity on tree shade efficiency by comparing sunny and cloudy conditions, as well as different times of the day. In addition, we investigated the differences in shading efficiency over various surfaces by comparing pairs of regular urban surfaces (asphalt, concrete, permeable brick, and grass). We found that tree shade significantly improved the local thermal environment, but its effectiveness varied with the environmental conditions. Tree shading resulted in a higher cooling efficiency under greater external thermal stress. In addition, the cooling efficiency was greater on surfaces with higher temperatures. We also identified a notable characteristic of tree shading for cooling: the thermal environment beneath the tree shade tends to stabilize at a relatively constant value across various external conditions. These results provide practical guidelines for optimizing tree layouts in highly heterogeneous urban environments and enhancing limited tree resources for more effective and economical improvement of urban thermal conditions.

Analysis of the Interplay between Indoor Air Quality and Thermal Comfort in University Classrooms for Enhanced HVAC Control

While aspects of indoor environmental quality, such as thermal comfort, indoor air quality (IAQ), acoustic, and visual comfort, are usually studied separately, their interactions are crucial yet often overlooked. Understanding how these factors influence each other is essential for a comprehensive perception of the indoor environment. This paper investigates the relationship between indoor air quality (IAQ) and thermal comfort using an extensive field investigation conducted in university classrooms during the heating season, collecting 712 samples of subjective responses correlated with environmental measurements. Key findings reveal significant correlations between subjective responses related to the thermal environment and those related to air quality. Perceived control over the thermal environment shows stronger correlations with IAQ responses than with thermal responses, particularly with perceived ventilation (r = 0.41), COVID-19 risk (r = 0.28), and air quality (r = 0.28). Additionally, environmental parameters demonstrate stronger correlations with thermal responses than with IAQ responses. Higher CO2 concentration is associated with increased thermal sensation and decreased thermal preference and perceived control. Conversely, IAQ responses remain relatively stable with changes in indoor operative temperature. The difference between the operative temperature to which the occupants are exposed and their expressed neutral temperature widens as CO2 concentration rises, indicating a reduced adaptive capacity of occupants which is associated with increasing CO2 levels. These insights are crucial for providing HVAC system management strategies that consider the interaction between different aspects of IEQ, aiming to improve occupants’ well-being and reduce energy consumption.