Thermal Environment Effect Research Articles

Vibration studies of an axially moving epoxy-carbon nanofiber composite beam in thermal environment—Effect of various nanofiber reinforcements

Free vibrations of an axially moving multiscale composite beam in thermal environment are analyzed. The beam material is epoxy resin with variously reinforced and randomly oriented or aligned in electric field carbon nanofibers (CNFs). To describe the thermomechanical properties of the beam material, published dynamic characteristic of stationary multiscale composites were taken into consideration. Using the frequency–temperature equivalence principle, the nanocomposite material of the beam is modeled using four-parameter fractional rheological model. The dynamic characteristics of the multiscale polymer beam in the frequency domain made it possible to determine the partial equation of motion of the axially moving beam. The Galerkin method is used to solve the governing partial differential equation. The effects of various nanofiber reinforcements of randomly oriented, and aligned in electric field fibers at different temperatures, on the free vibration of the axially moving beam are investigated.

A method based on elitist genetic algorithm for calibrating the thermo-physical surface indicators: Its principles, validation and application to bioswales

Pavement is closely linked to the hydrological characteristics of the surface, which affects the infiltration and retention of surface runoff, leading to changes in thermo-physical surface indicators such as surface albedo, surface emissivity, volumetric heat capacity, thermal diffusivity, average soil temperature and surface humidity. Green drainage facilities, particularly bioswales, can mitigate runoff and improve microclimates by altering the flow path of water and thermo-physical surface indicators. While the thermo-physical indicators of artificial pavement surfaces such as sand, asphalt, cement, brick and stone have been studied and applied, those of bioswales have yet to be thoroughly investigated, and there is a dearth of scientific evaluation methods for their thermal effect. In this study, a genetic algorithm-based method for calibrating thermo-physical surface indicators was established, and its reliability was validated by comparing the thermo-physical indicators of asphalt pavement surfaces with existing literature. Two bioswales covering 200 m2 were designed and constructed, and their surface air temperature (1.5-meter from the surface) was monitored under irrigating and non-irrigated scenarios, and the thermo-physical indicators of two bioswales surface were determined. The temperature of bioswales in relevant literature was calculated by using the calibration results, and compared with the measured air temperature. The calibration method exhibited an error range of −9.6% to + 4.3%, and the surface temperature error resulting from the application of calibration parameters was 0.9133 to 0.9338. By establishing a method for determining the thermo-physical indicators of surface pavement and obtaining the thermo-physical indicators of bioswale surfaces using the surface temperature data, this study provides essential support for evaluating the thermal environment effect of bioswales.

Nonlinear vibrations of multiscale composite beams on a nonlinear softening foundation

This paper describes a new approach to evaluate the instability of beams on a softening elastic foundation. The basis of this approach is solving a nonlinear frequency problem. The beam is made of multiscale composite materials based on carbon nanotubes (CNTs) and long fibers. Homogenization methods are utilized in a sequential process to obtain the effective material properties of these composites. Furthermore, the thermal environment's effect on the beam's response is examined. Reddy's third-order shear deformation theory approximates the induced displacements in the composite beam. Also, the kinetic and strain energies of the beam are calculated based on the von Kármán nonlinear strains and linear thermoelasticity theories. A recently reported Lagrangian nodal weak formulation (LNWF) method is implemented to obtain the linear and nonlinear stiffness and mass matrices governing the beam's vibrations. The modified coefficients for nonlinear stiffness matrices are obtained using the residual Galerkin method across time. Finally, the nonlinear natural frequencies are calculated by employing the iterative displacement control strategy. In the results section, in addition to examining various parameters on nonlinear free vibrations, the effect of these parameters on the displacement required for the loss of stability of the beam placed on the softening foundation is also examined.

Thermal Environment Effect of Landscape Ecological Pattern and Dynamic Analysis of Pattern Evolution

The obvious characteristics of urban thermal environment and heat island effect have brought a series of negative effects on urban ecosystem structure and residents' health. Scholars at home and abroad have conducted basic researches on urban thermal environment, but there is a lack of researches on areas with rapid urbanization and many interference factors. There are few researches on measures or suggestions to improve urban thermal environment and heat island effect from the perspective of ecological sustainable development. To this end, this paper conducts a study on thermal environment effect of landscape ecological pattern and dynamic analysis of pattern evolution. This paper, based on the radiative transfer equation method, carries out back calculation and back analysis on the parameters of urban surface temperature to obtain the dynamic characteristics of urban thermal ecological landscape pattern. By combining the obtained urban surface temperature with the landscape index, this paper analyzes the internal change of urban surface thermal ecological landscape pattern. Through the spatial characteristics of the barycenter of urban thermal environment effect, the expansion and development trend of urban thermal environment effect is revealed. Then based on Moran'sI coefficient, the whole spatial correlation of urban thermal environment effect and the degree of spatial aggregation in local areas are analyzed. Finally, the corresponding experimental results and analytical results are given in combination with the experiments.

Thermal comfort differences between urban villages and formal settlements in Chinese developing cities: A case study in Shenzhen

Rapid urbanization has changed the urban spatial form, which directly leads to the emergence of urban informal settlements, and the impact on ecological environment is manifested as the obvious deterioration of urban thermal environment. The thermal environment of informal settlements, which are called urban villages in China, is seriously deteriorated. In the process of urban renewal, we should pay attention to the thermal environment effect of urban villages and promote the sustainable development of cities. However, at present there are few studies on the differences of thermal comfort among urban settlements. Taking Shenzhen as an example city, this paper distinguished several scopes such as urban villages, formal settlements and non-urban areas, then analyzed the pattern characteristics of urban thermal comfort by using the Modified Temperature and Humidity Index (MTHI), and finally explored the spatial relationship between thermal comfort and various environmental factors through spatial regression models. The results show that (1) thermal comfort has significant spatial autocorrelation and the thermal environment centers are clustered in built-up areas of Shenzhen city. The overall MTHI of urban villages is relatively the highest, and the dominant thermal comfort level in summer is sultry and hot. (2) According to the Spatial Error Model, the green space coverage represented by NDVI has the strongest mitigation effect on urban thermal comfort, and the building density has an obvious aggravating effect on the muggy environment. Both of them have more obvious effects on the thermal comfort of informal settlements. (3) The current thermal environment of urban settlements cannot be ignored, especially in urban villages. In the process of urban renewal, heat dissipation should be considered emphatically. Increasing urban green area and decreasing building density will help to improve urban thermal environment. The study can provide suggestions for urban renewal from the perspective of improving thermal environment.

Spatiotemporal Evolution of the Urban Thermal Environment Effect and Its Influencing Factors: A Case Study of Beijing, China

Rapid urbanization has led to significant changes in land surface temperature (LST), which in turn affect the urban thermal environment effect and the health of residents. Exploring the causes of the urban thermal environment effect will provide guidance for promoting sustainable urban development. The spatiotemporal evolution of the urban thermal environment effect within the sixth ring road of Beijing was analyzed by inversion of remote sensing data to obtain the LST in 2004, 2009, 2014, and 2019. In addition, based on multivariate spatial data, we applied the standard deviation ellipse (SDE), spatial principal component analysis (PCA), and other methods to analyze and identify the relationships between the urban thermal environment effect and its influencing factors. The results show that from 2004 to 2019, the spatial distribution of urban development and LST within the sixth ring road of Beijing were closely related, the heat island area showed a small increasing trend, and differences in the thermal environment effect between different administrative regions in different periods were obvious. The main factors affecting the urban thermal environment effect were urban construction intensity, vegetation and water bodies, socioeconomic activities, and geomorphology. It is noteworthy that human factors had a greater impact than natural factors. Among them, the positive effect of the normalized difference impervious surface index (NDBBI) and the negative effect of the fractional vegetation cover (FVC) were the most prominent. This study provides theoretical support for mitigating the urban thermal environment effect and promoting sustainable urban development.

Method of calculating land surface temperatures based on the low-altitude UAV thermal infrared remote sensing data and the near-ground meteorological data

The continuous urbanization has greatly changed the underlying surfaces, which leads to great impacts on the urban thermal environment. The land surface temperatures (LSTs) have gained considerable attention as a typical indicator for studying the urban thermal environment. Accounting for the deficiency of existing calculation methods in calculation principle of LSTs from the low-altitude thermal infrared remote (TIR) sensing data, this study proposes a method to retrieve the LSTs at a block scale with high temporal and spatial resolution for the effective evaluation of micro urban thermal environment. Thus, the thermal infrared radiation transmission equation is rewritten according to the actual thermal infrared transmission process. The final calculation form of LSTs is given, in which the multi-source data is employed. Ultimately, to verify the accuracy of this method in calculating the LSTs, an application case is designed. The results indicate that the temperature differences between the calculated LSTs and the measured LSTs ranges from -1.73 K to 1.45 K, and the absolute accuracy of the method is 0.09 K based on the correctly obtained multi-source data. This method is available for the quantitative analysis of the urban thermal environment and urban heat island effect at a block scale.

Evaluation of urban green space in terms of thermal environmental benefits using geographical detector analysis

Urban green space (UGS) plays an indispensable role in urban spaces, providing important ecological services to compensate for natural environment functions damaged by rapid urbanization. Understanding the impact of the UGS landscape pattern on its environmental benefits in order to evaluate UGS quality is critical for increasing its use efficiency. Previous studies have frequently constructed evaluation indexes based on subjective assessment of UGS landscape patterns using principal component analysis, factor analysis, and other methods without combining the actual environmental benefits in a complex urban environment. We investigated the changes in land surface temperature (LST) under different UGS landscape patterns, which can help clarify the urban thermal environment effect of UGS, and constructed a comprehensive index, the Green Environmental Benefit Index (GEBI), for UGS evaluation. Our results show that: (1) spatial allocation and configuration of UGS impact LST at both landscape and class levels, and the impact varies significantly with different vegetation types and landscape patterns. (2) The influence of each pair of driving factors on UGS thermal environmental benefits is mutually enhanced, indicating that urban greening can be improved across multiple dimensions. (3) UGS evaluation based on GEBI is objective and compelling, where alleyways of the inner-city were identified as areas in need of greening optimization in the study area. Revealing more details of the UGS landscape pattern, this study can help to construct a scientific and objective evaluation model and provide a reference for urban greening optimization and planning.

Multi-objective optimization design for windows and shading configuration: considering energy consumption, thermal environment, visual performance and sound insulation effect

Multi-objective optimization design for windows and shading configuration: considering energy consumption, thermal environment, visual performance and sound insulation effect

Ruminal volatile fatty acid absorption is affected by elevated ambient temperature

The objective of this study was to investigate the effect of short-term elevated ambient temperature on ruminal volatile fatty acid (VFA) dynamics and rumen epithelium gene expression associated with the transport and metabolism of VFA. Eight ruminally cannulated Holstein heifers (200 kg) were used in a factorial, repeated measures experiment with two treatments and two periods. During the first period, animals were provided with feed ad libitum and housed at 20 °C. During the second period, one group (HS) was housed at 30 °C and fed ad libitum. The other group (PF) was housed at 20 °C and pair-fed to match the intake of the HS group. During each period, animals were kept on treatment for 10 day, with sample collection on the final day. In the second period, indicators of heat stress were significantly different between PF and HS animals (P < 0.05). There was a thermal environment effect on butyrate production (P < 0.01) that was not associated with feed intake (P = 0.43). Butyrate absorption decreased in HS animals (P < 0.05) but increased in PF animals (P < 0.05) from period 1 to period 2. There was a feed intake effect on BHD1 expression (P = 0.04) and a tendency for a thermal environment effect (P = 0.08), with expression increasing in both cases. Expression of MCT4 was affected by feed intake (P = 0.003) as were all NHE genes (NHE1, NHE2, and NHE3; P < 0.05). These results indicate that with low feed intake and heat stress, there are shifts in rumen VFA dynamics and in the capacity of the rumen epithelium to absorb and transport VFA.

Contribution of Spatial Heterogeneity and Temporal-Spatial Change of Ecosystems to the Thermal Environment of Tourist Destinations: A Case Study of Sichuan-Chongqing Region, China

Tourism development activities affect the structure and functions of ecosystems directly triggering changes in the thermal environment of tourism destinations and raising a need for sustainable development of the tourism industry. Using the 2005–2015 moderate resolution imaging spectroradiometer (MODIS) data on the land surface temperature combined with the land use data, the urban thermal environment contribution index (CI) of prefecture-level cities and ecosystem types corresponding to the study area in Sichuan-Chongqing region were quantitatively calculated under various seasonal and diurnal conditions in terms of the scales of administrative divisions and ecosystem types. The characteristics of the roles played by different cities and ecosystem types to contribute to the thermal environment of the metropolitan region were summarized, and the differences and changes in the corresponding contribution intensity of various ecosystem types were measured. The results indicate the following: (1) Different cities play different roles as the sources and sinks with respect to the thermal environment in the daytime and nighttime. Based on the diurnal differences of the contribution indices, cities can be divided into three types: the day-night heat source type, the day-sink and night-source type, and the day-night heat sink type. (2) The farmland and the grassland ecosystems are the most important source and sink landscapes in the thermal environment of the Sichuan-Chongqing Region, respectively. (3) The region is affected by the spatial arrangement of the internal ecosystems and its own development conditions, and, consequently, there are significant temporal-spatial variations and role transitions between heat source and heat sink regarding the contribution of different ecosystem types to the thermal environment of individual cities. It is important to scientifically regulate the thermal environment effect on tourism destinations and maintain the comfort and sustainable development through identifying the source and sink ecosystems of the thermal environment, controlling the quantity and spatial arrangement of the heat source ecosystems, and fully enabling the cooling effect of the heat sink ecosystems.

Experimental study on a loop thermosyphon cooling system in data centers using CO2 as a working Fluid, especially thermal environment and energy-saving effect

This study focused on the working condition of a loop thermosyphon cooling system for data centers using carbon dioxide as a coolant. Carbon dioxide has two main advantages compared with traditional working fluids. First, carbon dioxide is more environmentally friendly, because it causes no harm to the ozone sphere, and its global warming effect is lower than that of Freon coolants. Second, carbon dioxide exhibits better heat transfer characteristics than Freon coolants. However, carbon dioxide’s working pressure is much higher than that of Freon coolants. In this study, carbon dioxide is used as a coolant in a loop thermosyphon cooling system in data center and its working condition, including the the inner thermal environment of the data center is studied. Furthermore, the working condition of Freon R410A is compared with that of carbon dioxide. The results show that the heat transfer characteristics of carbon dioxide are better than those of R410A, and the use of carbon dioxide is more economically beneficial. The experimental results provide an important reference and guiding value for engineering applications of carbon dioxide.

The influence of morphological characteristics of green patch on its surrounding thermal environment

In order to explore the influence of morphological characteristics of green patches on its surrounding thermal environment, the remote sensing image data of Taiyuan City was used as the basic data source, and the temperature field under the influence of morphological characteristics of green patches was simulated by CFD technique. The dimensionless parameter of relative temperature change rate was introduced as the index of thermal environment effect. From the existing shape index reflecting the patch characteristics, the indicators of the green patch affecting the surrounding thermal environment were screened out, and the corresponding quantitative relationship between them was established. Based on the statistical analysis of patch shape index and thermal environment effect index, it is pointed out that the deviation degree for equivalent perimeter of patch is positively correlated with the relative change rate of temperature reflecting thermal environment effect. Meanwhile, the smaller area of green space can be used to improve local microclimate. The introduction of CFD technology into the study of urban thermal environment provides a basis for exploring the key parameters to improve the ecological environment benefits of urban green space and determining the shape control index of patch in green space planning and design. On the other hand, the simulation function of CFD technology is used to optimize green space design, which has better significance to guide production practice.

Relationship between forest city landscape pattern and thermal environment: A case study of Longquan City, China.

The differentiation characteristics of landscape pattern affect the urban thermal environment. In this study, temperature characteristics of nine types of landscape in a national forest city, Longquan City, were analyzed by temperature inversion method and spatial analysis. The landscape pattern analysis method was used to explore the correlation of landscape metrics and the thermal environment from 1 km to 3.5 km. The results showed that the high and sub-high temperature zones of Longquan City were distributed in northeast-southwest, mainly composed of urban and rural residential areas. The low and sub-low temperature zone were mainly distributed in the northwest and southeast areas, mainly composed of public welfare forests. By calculating the mean land surface temperature of each landscape type in the area below 700 m above sea level, the temperature of coniferous forest, broadleaf forest, conifer-broadleaf forest, bamboo forest and water was relatively low, whereas that of shrub land, other forest land, cultivated land and construction land was relatively high. Through the analysis of landscape pattern and thermal environment, it was found that the class pattern index was more practical than the landscape pattern index. The correlation between thermal environment effect and construction land distribution reached 0.835, coniferous forest land, broadleaf forest land, coniferous-broadleaf forest land and water were the second, up to -0.5 to -0.4. The cooling effects of different forest types vaied across different spatial scales. Broadleaved forests and coniferous-broadleaved forests were more conducive to cooling at large scales. The larger the area and volume stock of forest land, the more likely it had the lowest land surface temperature.

Influence of ambient temperature on the modulation transfer function of an infrared membrane diffraction optical system.

In this paper, we present a model that analyzes the influence of the temperature on the modulation transfer function (MTF) of an infrared membrane diffraction optical system. Based on the physical imaging mechanism of diffractive optical systems, the imaging characteristics of the diffraction optical system are characterized by using diffraction efficiency. Then we establish the corresponding calculation model and MTF analysis model based on scalar diffraction theory. In particular, considering the material properties of flexible membrane optical elements and thermal environment effect, the Zernike polynomials are used to establish the thickness distribution model of the membrane diffractive optical components combined with the finite element analysis. After that, we modify the MTF calculation model of diffraction optical system and accordingly propose the model of the infrared membrane diffraction optical system. Finally, we present some experimental results for a 2-m infrared membrane diffraction optical system. The results show that when the temperature is -40°C and wavelength band is 80nm at the center field of view, the diffraction efficiency is reduced to 81%, and MTF at 75 lp/mm is reduced to 0.12. And when the temperature is -40°C at edge field of view, the efficiency at center wavelength is reduced to 71%, and MTF at 75 lp/mm is reduced to 0.02. The established model and method can be used to estimate the imaging performance of a space infrared membrane diffractive telescope and provide theoretical guidance for the processing algorithm and imaging system design.

Nanomechanics model for properties of carbon nanotubes under a thermal environment

This paper proposes a modified molecular mechanics model in which the covalent bond is treated as a beam element, and a theoretical prediction of the thermal environment effect on the elastic properties of single-walled carbon nanotubes (SWCNTs) is reported. The influence of the temperature on Young’s modulus of both armchair and zigzag SWCNTs is investigated. The study shows that the moduli decrease with the increase in temperature, but Poisson’s ratio is not dependent on the temperature. The temperature-dependent Young’s modulus increases with the increase in tube diameter. According to the principle of elasticity theory and energy consistent theory, a temperature-dependent continuum shell model of strain energy is also established. It is found that the deviation between the potential energy of carbon nanotubes and the strain energy of a continuum shell is significantly reduced based on the molecular mechanics model proposed in this study.

The Spatial Patterns of Land Surface Temperature and Its Impact Factors: Spatial Non-Stationarity and Scale Effects Based on a Geographically-Weighted Regression Model

Understanding the spatial distribution of land surface temperature (LST) and its impact factors is crucial for mitigating urban heat island effect. However, few studies have quantitatively investigated the spatial non-stationarity and spatial scale effects of the relationships between LST and its impact factors at multi-scales. The main purposes of this study are as follows: (1) to estimate the spatial distributions of urban heat island (UHI) intensity by using hot spots analysis and (2) to explore the spatial non-stationarity and scale effects of the relationships between LST and related impact factors at multiple resolutions (30–1200 m) and to find appropriate scales for illuminating the relationships in a plain city. Based on the LST retrieved from Landsat 8 OLI/TIRS images, the Geographically-Weighted Regression (GWR) model is used to explore the scale effects of the relationships in Zhengzhou City between LST and six driving indicators: The Fractional Vegetation Cover (FVC), the Impervious Surface (IS), the Population Density (PD), the Fossil-fuel CO2 Emission data (FFCOE), the Shannon Diversity Index (SHDI) and the Perimeter-area Fractal Dimension (PAFRAC),which indicate the vegetation abundance, built-up, social-ecological variables and the diversity and shape complexity of land cover types. Our findings showed that the spatial patterns of LST show statistically significant hot spot zones in the center of the study area, partly extending to the western and southern industrial areas, indicating that the intensity of the urban heat island is significantly spatial clustering in Zhengzhou City. In addition, compared with the Ordinary Least Squares (OLS) model, the GWR model has a better ability to characterize spatial non-stationarity and analyze the relationships between the LST and its impact factors by considering the space-varying relationships of different variables, especially at the fine spatial scales (30–480 m). However, the strength of GWR model has become relatively weak with the increase of spatial scales (720–1200 m). This reveals that the GWR model is recommended to be applied in the analysis of UHI problems and related impact factors at scales finer than 480 m in the plain city. If the spatial scale is coarser than 720 m, both OLS and GWR models are suitable for illustrating the correct relationships between UHI effect and its influence factors in the plain city due to their undifferentiated performance. These findings can provide valuable information for urban planners and researchers to select appropriate models and spatial scales seeking to mitigate urban thermal environment effect.

The thermal environment effect on the comfort of electronic factory worker

In this paper, thermal comfort issues of the operators working on one of the electronics companies in the evaporator area are observed. The objective of this study is to reduce Percentage of Dissatisfied (PD) of operators in an effort to improve the work productivity. PD is predicted using CBE Thermal Comfort Tool by measuring the thermal variables around the evaporator area and by calculating the Heat Stress Index (HSI). The operator productivity is analyzed by Wet Bulb Globe Thermometer (WBGT) Work-Rest Chart. The PD of operators before and after improvement is compared. The results showed that the average temperature around the operators area at evaporator station is high with average WBGT of 33,6°C. HSI value is 51.95 indicating that the effect of 8-h exposure is severe strain with work impact is health threat for unit operators and acclimatization is necessary. The PD value is 96% indicating that almost all operators feel uncomfortable at work. These indicate that the thermal environment should be improved. The proposed improvement is by installing water cooled and sprayed into the evaporator area. This installation is able to reduce HSI and PD by more 70% and more 60%, respectively. These findings indicate that improving the thermal environment will be able to improve working comfort which will further affect the level of work productivity.

某中規模ビルにおける省エネルギー改修に関する研究 （第2報）建物外皮改修後における冬期室内温熱環境測定と改修効果

某中規模ビルにおける省エネルギー改修に関する研究 （第2報）建物外皮改修後における冬期室内温熱環境測定と改修効果

The Impact of Water on Microclimate in Lingnan Area

In this paper, the micro-climate of waterfront landscape in Lingnan area is analyzed by numerical simulation. The water scale in the waterfront landscape of Lingnan area are studied. The quantitative analysis and qualitative analysis are used to analyze the relationship between water scale and climate factors like wind speed and air temperature, and the influence of water scale on the micro-climate in waterfront landscape are studied furtherly. The results show that water scale has a significant effect on the micro-climate of the waterfront environment in, which is beneficial to adjust temperature and humidity in micro-climate. The thermal environment effect of water area including cooling and moistening is more obvious than that of water depth changing. The area and depth of the water have a regulating function of regional climate in a certain extent.