Changes In Thermal Environment Research Articles

Effects of different environment combinations on the comfort and productivity of researchers in winter

Indoor environmental quality is considered an important indicator of the sustainable development of architecture. It not only reflects the comfort level of occupants in the building but also affects their productivity, particularly in research institutions. However, due to the inherent correlation among various environmental indexes, it is difficult to evaluate the influence of specific physical parameters on the occupant’s comfort and research performance. This paper is based on an experiment conducted in a controlled research office in a pharmaceutical research company in the Northeast of China. The controlled research office was equipped with a radiant floor heating system that supplied heating in winter. We recruited 32 researchers and divided them into four subgroups. Each subgroup of researchers was required to conduct daily research activities under 12 different environment combinations. Data were collected from physical environment measurements, questionnaire surveys and performance tests. The results reflected that under the condition of radian floor heating in winter, changes in thermal, visual and acoustic environments could have a significant influence on occupants’ satisfaction with the environment. However, the research performance was affected only by thermal and acoustic conditions. There was a weak correlation among thermal, visual, acoustic and indoor air quality comfort.

Self-adaptive cooling of chips with unevenly distributed high heat fluxes

• A self-adaptive chip cooling method for high heat fluxes is proposed. • Unevenly distributed high heat fluxes of up to 460 W/cm 2 are effectively removed. • The maximum surface temperature drop amounts to 22.6 K with reduced flow rates. • Coolant flow adapts to local heat fluxes and movable hotspots are cooled effectively. The heat load scenario of a real chip is unsteady and spatially variable and gives rise to regions of concentrated high power. Conventional liquid cooling techniques are always inadequate to tailor the flow distribution to the changing thermal environment and cool the resulting high-heat-flux regions effectively. In this work, the self-adaptive cooling for unevenly distributed high heat fluxes is proposed. It contains a matrix of microfluidic units with integrated thermal-sensitive hydrogel valves. The units are independently controlled and deliver the coolant to where it is needed. A numerical model is developed to investigate the flow and temperature distribution of the cooling unit. By introducing the self-adaptive mechanism, the near-wall flow is enhanced remarkably. Nonuniform heat fluxes of up to 460 W/cm 2 are effectively dissipated by means of the developed self-adaptive cooling method. The maximum surface temperature drop amounts to 22.6 K, meanwhile the total flow rate can be reduced by nearly an order of magnitude. The microfluidic unit array adapts to local heat fluxes by reconfiguring its internal flow-channel structure automatically and thus movable hotspots are elaborately cooled. The self-adaptive cooling scheme offers both effective and smart thermal management for modern electronic devices.

Selection of the gridded temperature dataset for assessment of thermal bioclimatic environmental changes in Amu Darya River basin.

Assessment of the thermal bioclimatic environmental changes is important to understand ongoing climate change implications on agriculture, ecology, and human health. This is particularly important for the climatologically diverse transboundary Amy Darya River basin, a major source of water and livelihood for millions in Central Asia. However, the absence of longer period observed temperature data is a major obstacle for such analysis. This study employed a novel approach by integrating compromise programming and multicriteria group decision–making methods to evaluate the efficiency of four global gridded temperature datasets based on observation data at 44 stations. The performance of the proposed method was evaluated by comparing the results obtained using symmetrical uncertainty, a machine learning similarity assessment method. The most reliable gridded data was used to assess the spatial distribution of global warming-induced unidirectional trends in thermal bioclimatic indicators (TBI) using a modified Mann–Kendall test. Ranking of the products revealed Climate Prediction Center (CPC) temperature as most efficient in reconstruction observed temperature, followed by TerraClimate and Climate Research Unit. The ranking of the product was consistent with that obtained using SU. Assessment of TBI trends using CPC data revealed an increase in the Tmin in the coldest month over the whole basin at a rate of 0.03–0.08 °C per decade, except in the east. Besides, an increase in diurnal temperature range and isothermally increased in the east up to 0.2 °C and 0.6% per decade, respectively. The results revealed negative implications of thermal bioclimatic change on water, ecology, and public health in the eastern mountainous region and positive impacts on vegetation in the west and northwest.Supplementary InformationThe online version contains supplementary material available at 10.1007/s00477-022-02172-8.

Using Local Climate Zones to investigate Spatio-temporal evolution of thermal environment at the urban regional level: A case study in Xi'an, China

The concept of Local Climate Zone (LCZ) classification scheme is an effective tool for quantifying the Urban Heat Island (UHI) effect. However, previous studies of the thermal environment using LCZs mainly focused on the meso‑ to-micro-scale or a single time, and the changes in the regional thermal environment were less considered. Thus, we selected the Xi'an urban spatial agglomeration and used remote sensing images from 2008, 2013, and 2019 to determine the spatial and temporal variations in the thermal environment for statistical analysis and contrast. The results confirmed that: (1) The proportions of low-rise types decreased significantly, and the land use for agglomerations and compacts shows an upward trend. (2) The built-up LCZs had higher land surface temperatures (LST), LCZ 10 (heavy industry) was the highest in all years. (3) The LCZs with LCZ A (dense trees), and LCZ G (water) were associated with slightly lower LSTs, and they helped to cool the city. (4) The LSTs tended to increase from natural to urban areas, before gradually decreasing with distance from the city center to rural areas. These findings may provide reference values for quantitative studies of LCZ classification maps and analyzing dynamic changes in urban surface thermal environments, thereby facilitating the UHI analysis and climate-adapted urban planning.

Local thermal environment and warming influence supercooling and drive widespread shifts in the metabolome of diapausing Pieris rapae butterflies.

Global climate change has the potential to negatively impact biological systems as organisms are exposed to novel temperature regimes. Increases in annual mean temperature have been accompanied by disproportionate rates of change in temperature across seasons, and winter is the season warming most rapidly. Yet, we know relatively little about how warming will alter the physiology of overwintering organisms. Here, we simulated future warming conditions by comparing diapausing Pieris rapae butterfly pupae collected from disparate thermal environments and by exposing P. rapae pupae to acute and chronic increases in temperature. First, we compared internal freezing temperatures (supercooling points) of diapausing pupae that were developed in common-garden conditions but whose parents were collected from northern Vermont, USA, or North Carolina, USA. Matching the warmer winter climate of North Carolina, North Carolina pupae had significantly higher supercooling points than Vermont pupae. Next, we measured the effects of acute and chronic warming exposure in Vermont pupae and found that warming induced higher supercooling points. We further characterized the effects of chronic warming by profiling the metabolomes of Vermont pupae via untargeted LC-MS metabolomics. Warming caused significant changes in abundance of hundreds of metabolites across the metabolome. Notably, there were warming-induced shifts in key biochemical pathways, such as pyruvate metabolism, fructose and mannose metabolism, and β-alanine metabolism, suggesting shifts in energy metabolism and cryoprotection. These results suggest that warming affects various aspects of overwintering physiology in P. rapae and may be detrimental depending on the frequency and variation of winter warming events. Further research is needed to ascertain the extent to which the effects of warming are felt among a broader set of populations of P. rapae, and among other species, in order to better predict how insects may respond to changes in winter thermal environments.

Study on a thermophysiological model for health assessment of showering environment in China

In China, the thermal environment of family showers in old communities is quite different from that of other living spaces, especially when the thermal environment changes drastically during showering, which can easily cause health problems. The human thermal physiological model is an effective tool to predict and evaluate the non-uniform and unstable shower thermal environment and human health risks. In this research, the showering experiment was carried out in a typical bathroom in an old community in China, during which environmental parameters such as air temperature, wall temperature and water temperature of the bathroom during the showering were recorded, and physiological parameters such as skin temperature, core temperature and blood pressure during the whole showering process were detected. Based on the multi-node numerical human body model of Stowljik and a cardiovascular control model with human body temperature as the driving force, a temperature-blood pressure coupling prediction model was established. The validity of the proposed model was examined for blood circulation. This predictive model can accurately reflect changes in physiological parameters and is verified as suitable for the health assessment of showering environment in residential buildings.

Simulation Experiment on Energy Tower Coupled with Buried Pipe System of Ground-source Heat Pump for Cross-season Heat Storage

It is proposed to use energy tower instead of solar collector system to store heat for buried pipe system of ground-source heat pump in summer, so as to solve the problem that soil temperature is too low due to unbalanced cold and heat load of GSHP in cold and severe cold area. The simulation results show that the thermal storage power of energy tower is affected by soil temperature and environmental temperature. The lower the soil temperature, the better the thermal storage effect of energy tower system for soil. The thermal storage power and environmental temperature change in a positive relationship. It is proved that the application of cross-season heat storage is feasible for energy tower coupled with buried pipe system of ground-source heat pump in cold and severe cold area.

Landsat-Based Monitoring of the Heat Effects of Urbanization Directions and Types in Hangzhou City from 2000 to 2020

Rapid urbanization has produced serious heat effects worldwide. However, the literature lacks a detailed study on heat effects based on the directions and types of urban expansion. In this work, a typical city with an extremely hot summer climate, Hangzhou, was selected as a case study to determine the relationships between the urban heat-effect dynamics and spatiotemporal patterns of impervious surface expansion. Based on long-term Landsat imagery, this study characterized the spatiotemporal patterns of urban expansion and normalized surface temperatures in Hangzhou City from 2000 to 2020 using object-based backdating classification and a generalized single-channel algorithm with the help of a land-use transfer matrix, expansion index, and spatial centroids. Relevant policies, industries, and traffic networks were discussed to help explain urban expansion and thermal environment changes. The results demonstrated that in 2020, the area of impervious surfaces covered 1139.29 km2. The majority of the gains were in farmland, water, and forests, and the annual growth rate was 32.12 km2/year beginning in 2000. During the expansion of impervious surfaces, the city warmed at a slower rate, and more thermal contributions came from sub-urban areas. The southeast-oriented expansion of impervious surfaces was the key reason for the spatiotemporal dynamics of the urban heat effects. The dominant urban edge expansion intensified the local heat effects. This research provides a Landsat-based methodology for better understanding the heat effects of urban expansion.

Self-Assembly of Phycoerythrin with Oligochitosan by Electrostatic Interaction for Stabilization of Phycoerythrin.

Phycoerythrin (PE) is a natural water-soluble pigment protein with characteristic phycobilins and is sensitive to thermal and light environmental changes. In this study, PE was extracted from Porphyra haitanensis and PE-oligochitosan complexes (POC) were fabricated by a self-assembly approach. The effects of cationic oligochitosan on the binding interaction, structure, size distribution, and color stability of PE were evaluated. The stoichiometric number n was calculated to be 21.67 ± 2.65 (oligochitosan/PE) and the binding constant K was (6.47 ± 0.48) × 105 M-1. Cationic oligochitosan could electrostatically interact with PE and affect the PE structure by increasing the α-helix content. In addition, high concentrations of oligochitosan led to the formation of dense phycoerythrin protein granules. Moreover, at a reaction ratio of 20.0:1 (oligochitosan/PE), being approximately the predicted stoichiometric number n, the thermal stability (40-80 °C), natural light stability, and ultraviolet light irradiation (254 nm) stability of the POC were improved. This study provides an approach to reduce the susceptibility of PE upon environmental changes by forming a stable self-assembly complex, which will promote the application of PE as a natural pigment protein in food and chemical applications.

Adequate sample sizes for improved accuracy of thermal trait estimates

Abstract Thermal traits, such as upper and lower critical thermal limits, are vital indicators of the vulnerability of populations and species to environmental change. Thus, accurate estimates of these traits are needed to explain biological patterns and forecast responses to the changing thermal environment. However, many thermal trait studies measure relatively few individuals to estimate traits for whole populations or species. To ascertain if, and how, sample size affects the accuracy of reported trait means and variances, we applied a subsampling and equivalency testing approach to empirical and simulated trait data to investigate the accuracy of trait estimates relative to sample size and the skew and variance of the trait distribution in the source population. Simulation results indicated that only 7.9% of the 428 critical thermal limit traits documented in a recent synthesis of thermal trait data reported sufficiently large sample sizes, relative to variance, to ensure confidence in the reported mean trait value with negligible (±0.25°C) error. Greater inter‐individual trait variance in the source population requires a larger number of individuals to be measured to accurately estimate the mean and variance of that trait. This pattern is mitigated somewhat by the tendency of thermal traits to exhibit skew‐normal distributions. As measurements of few individuals from a population are unlikely to provide accurate estimates of thermal traits, the propensity towards small sample sizes in thermal trait studies is concerning. Macrophysiological syntheses often use these data to describe, explain and predict broad‐scale ecological patterns. Thus, insufficient sample sizes in the original studies could diminish the robustness of these patterns and predictions. For future studies, we recommend that preliminary data be used to estimate trait variance and calculate minimum sample sizes. If small sample sizes are unavoidable, larger error around the measured trait mean must be assumed and accounted for in subsequent analyses. A free Plain Language Summary can be found within the Supporting Information of this article.

Changes in the Urban Surface Thermal Environment of a Chinese Coastal City Revealed by Downscaling MODIS LST with Random Forest Algorithm

Changes in the Urban Surface Thermal Environment of a Chinese Coastal City Revealed by Downscaling MODIS LST with Random Forest Algorithm

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.

Contributions of Land Utilization Differences and Changes in Zhongyuan Urban Agglomeration to Regional Thermal Environment

Accelerated urbanization has given rise to sharp environmental changes in urban underlying surfaces, thus changing the regional thermal environment and endangering the ecosystem balance. The thermal environment is complex, and the influence laws of land utilization differences and changes in the thermal environment in different seasons and under different daytime and nighttime conditions are unclear. In this regard, effective measures should be implemented to reduce the regional thermal environmental effect and determine the influence laws of land utilization differences and changes in the regional thermal environment. Zhongyuan urban agglomeration was applied as the study area. Two-year MODIS eight-day synthesized surface temperature product and land utilization monitoring data were obtained by remote sensing and used to analyze the influencing characteristics of different cities and land utilization types on the thermal environment of urban agglomeration from the angles of interannual differences and seasonal differences. During 2010-2018, the area changes in different land utilization types in the study area are significant with decreasing farmland area and increasing forest land and construction land. The farmland and forest land have the most significant influences on the regional thermal environment, where the farmland exerts a warming effect on the regional thermal environment and the forest land exerts a cooling effect. In different seasons and under different daytime and nighttime conditions, the construction land shows a strong warming effect on the regional thermal environment. The contribution indices of Changzhi city and Jincheng city to the thermal environment of the urban agglomeration are negative, so they exert the cooling effect. The warming or cooling role played by Handan city, Liaocheng city, and Xingtai city in the thermal environment is transited under different daytime and nighttime conditions, namely, they exert the warming effect in the day

Differences between EEG during thermal discomfort and thermal displeasure

This study used electroencephalograms (EEGs) to investigate thermal discomfort. The thermal discomfort defined in this study considers both thermal displeasure induced by step-changes and thermal discomfort induced by temperature ramping. A total of 108 people in their 20s and 30s participated in the experiments. The subjects experienced uncomfortable thermal environmental changes and changes in EEG were measured accordingly. The EEG data were divided into four frequency bands, namely; theta (4–8 Hz), alpha (8–13 Hz), beta (13–30 Hz), and gamma (30–40 Hz) waves for analysis. By examining the thermal-displeasure EEGs, we observed that when thermal displeasure was induced by heat, the relative theta power decreased and the relative beta and gamma powers increase. Furthermore, the relative theta power decreased when thermal displeasure was induced by cold. By examining the thermal-discomfort EEGs, we observed that all the EEG power values increase when thermal discomfort results from either heat or cold. Based on these experimental results, the brainwaves can be utilized to increase the prediction accuracy of individual thermal comfort by the conventional comfort model that is based on physical quantities, such as, temperature, humidity, air velocity, metabolic rate, and clothing insulation.

Reliability Evaluation of Photovoltaic System Considering Inverter Thermal Characteristics

The reliable operation of photovoltaic (PV) power generation systems is related to the security and stability of the power grid and is the focus of current research. At present, the reliability evaluation of PV power generation systems is mostly calculated by applying the standard failure rate of each component, ignoring the impact of thermal environment changes on the failure rate. This paper will use the fault tree theory to establish the reliability assessment method of PV power plants, model the PV power plants working in the variable environment through the hardware-in-the-loop simulation system, and analyze the influence of the thermal characteristics of the inverter’s key components on the reliability of the PV power plant. Studies have shown that the overall reliability of bus capacitors, inverters, and PV power plants is reduced by 18.4%, 30%, and 18.7%, respectively, compared to when the thermal characteristics of bus capacitors are not considered. It can be seen that thermal attenuation has a great influence on the reliability of the PV power generation system.

Human thermal comfort under dynamic conditions: An experimental study

Although thermal comfort has been a research topic since the 1960s, some knowledge gaps still affect understanding of the human response to changing thermal environments. To enhance knowledge in this regard, an exploratory study is presented, which aims to understand human response to monotonic thermal variations by describing its relationship with covariates of interest. Thirty-eight participants (29 females, 9 males) worked in an office-like climate chamber and were exposed to dynamic and controlled heating and cooling ramps of the operative temperature with different speeds. Participants' perception, evaluation, preference and acceptability of the indoor thermal environment were recorded by filling in dedicated questionnaires. Additionally, participants could indicate when an uncomfortable event occurred during these temperature ramps by clicking a digital button on a dedicated app. This discomfort event was defined in behavioural terms as the decision to “take action to restore a comfort condition”. Survival analysis was used to study participants’ reactions to the dynamic thermal stimuli. It showed that two distinct mechanisms caused discomfort events due to overheating and undercooling: warm discomfort is driven by the absolute value of the achieved operative temperature, while the relative change in operative temperature mainly causes cold discomfort. Compared to the current recommendations regarding temperature cycles, drifts and ramps, this result shows that current standard recommendations underestimate the risk of thermal discomfort during a cooling process while overestimating it during a heating one. The new knowledge of human reaction to a dynamic thermal environment can lead to more energy-efficient and satisfactory building control strategies.

Maternal cold exposure induces distinct transcriptome changes in the placenta and fetal brown adipose tissue in mice

BackgroundBrown adipose tissue (BAT) is specialized to dissipate energy in the form of heat. BAT-mediated heat production in rodents and humans is critical for effective temperature adaptation of newborns to the extrauterine environment immediately after birth. However, very little is known about whether and how fetal BAT development is modulated in-utero in response to changes in maternal thermal environment during pregnancy. Using BL6 mice, we evaluated the impact of different maternal environmental temperatures (28 °C and 18 °C) on the transcriptome of the placenta and fetal BAT to test if maternal cold exposure influences fetal BAT development via placental remodeling.ResultsMaternal weight gain during pregnancy, the average number of fetuses per pregnancy, and placental weight did not differ between the groups at 28 °C and 18 °C. However, the average fetal weight at E18.5 was 6% lower in the 18 °C-group compared to the 28 °C-group. In fetal BATs, cold exposure during pregnancy induced increased expression of genes involved in de novo lipogenesis and lipid metabolism while decreasing the expression of genes associated with muscle cell differentiation, thus suggesting that maternal cold exposure may promote fetal brown adipogenesis by suppressing the myogenic lineage in bidirectional progenitors. In placental tissues, maternal cold exposure was associated with upregulation of genes involved in complement activation and downregulation of genes related to muscle contraction and actin-myosin filament sliding. These changes may coordinate placental adaptation to maternal cold exposure, potentially by protecting against cold stress-induced inflammatory damage and modulating the vascular and extravascular contractile system in the placenta.ConclusionsThese findings provide evidence that environmental cold temperature sensed by the mother can modulate the transcriptome of placental and fetal BAT tissues. The ramifications of the observed gene expression changes warrant future investigation.

Field study on thermal environment and thermal adaptability of classrooms in Hefei area universities

In order to study the thermal environment and thermal comfort of university classrooms, a long-term on-site study of a university classroom in the Hefei area is carried out by combining questionnaires and on-site data collection. A thermal sensory model applicable to the university classroom in the Hefei area is established, and through analysis it is found that the measured thermal neutral temperature is lower than the predicted thermal neutral temperature under the PMV model, and the corresponding 90% acceptable temperature ranges under the measured and PMV models are 22.0~25.6°C and 17.2-24.9°C respectively. Opening and closing doors and windows and adding and removing clothing are the preferred thermal adaptive behaviors of the subjects when the indoor thermal environment changes.

Calculation method of mean skin temperature weighted by temperature sensitivity of various parts of human body.

Skin temperature is an important physiological parameter, and its calculation methods are varied, and the results are different. At present, the area weighting method is mostly used to calculate the mean skin temperature. However, the skin of various parts of the human body has different degrees of sensitivity to temperature changes. Based on this, this article proposes two calculation methods using the weighting of the cold and heat sensitivity coefficients. This article conducted experiments with different ambient temperatures (18 °C/20 °C/22 °C), clothing thermal resistances (1.10 clo/1.31 clo/1.44 clo), and activity levels (sitting/standing/walking) to obtain the subjects' local skin temperature. And then compared and analyzed the calculation results of the above-mentioned two sensitivity coefficient methods and the traditional area weighting method. The results found that there is no significant difference between the two sensitivity coefficient methods proposed in this article (the absolute difference is up to 0.09 °C, and the relative difference is less than 0.4%), but there is a certain difference with the traditional area weighting method. The ANOVA shows that the deviation is mainly affected by the ambient temperature (P < 0.01), and the thermal resistance of clothing and activity level have no significant effects (P > 0.05). By studying the relationship between mean skin temperature and thermal sensation voting, it is found that when the human skin temperature changes due to environmental temperature changes, the mean skin temperature and thermal sensation calculated by new method have a higher linearity (correlation coefficient R2 > 0.92), and the slope is larger, which can better reflect the influence of thermal environment changes on the human body's thermal sensation.

Heat and moisture transfer of building envelopes under dynamic and steady-state operation mode of indoor air conditioning

Realizing dynamic thermal comfort can help improve building performance. The heat and moisture transfer of the envelope is an important part of building performance. Therefore, this paper takes a typical room in Shanghai as an example and uses simulation software WUFI-PLUS and DELPHIN to study the influence of dynamic/steady-state operation mode of indoor air conditioning on the heat and moisture transfer of the envelope structure. The results show that based on the same thermal comfort, the energy consumption of the full heat load in dynamic operation mode is 73.69% lower than that in steady-state operation mode at 0ACH night ventilation, and it is 65.10% lower at 5ACH night ventilation. And at the same night ventilation condition, the moisture flow through the wall in the dynamic operating mode is smaller than that in the steady-state operating mode. In the case of 0ACH, when the partial pressure difference of water vapor is positive, the moisture transfer capacity in the dynamic operation mode of the indoor thermal environment is 11.7% lower than that in the steady-state operation mode. Therefore, when the partial pressure difference of water vapor is positive, the dynamic change of the indoor thermal environment can reduce the latent heat load of the envelope under the same water vapor pressure difference.