Effect Of Thermal Environment Research Articles

Effects of thermal and acoustic environments on human comfort in urban and suburban campuses in the cold region of China.

In this study, we investigated the effects of thermal-acoustic environments on human comfort in a cold region by focusing on Xi'an in China as a representative city. Four typical open spaces were identified within two universities, with one located in an urban area and the other in a suburban area. Surveys were conducted using questionnaires and environmental parameters were measured to assess thermal-acoustic perception. The physiological equivalent temperature (PET) and noise sound pressure levels were employed to measure the thermal-acoustic environments in the four open spaces. The results showed that the neutral PET was 19.1°C in Xi'an from March to May, and the neutral temperature range was 14.9-23.4°C. The preferred temperature was 20.0°C. Acoustic sensation votes were lower in suburban areas than urban areas. Respondents in urban areas exhibited significantly higher sensitivity to the thermal and acoustic environments compared with those in suburban areas. Sensitivity to the thermal environment decreased as the environmental noise levels decreased. The temperature perceived as most suitable increased as the sensitivity to the thermal environment decreased. Acoustic comfort evaluations were generally higher in colder and warmer environments. Warmer environments heightened the sensitivity to the acoustic environment and this effect gradually decreased as the sound pressure levels increased. Thus, based on empirical analyses, we compared the effects of outdoor thermal-acoustic parameters on comfort to provide experimental data support for further outdoor thermal comfort research.

Effects of interactions between thermal and acoustic environments on subjective comfort evaluations in outdoor public spaces

ABSTRACT In this study, five outdoor open areas were selected as the study sites to investigate the effects of thermal and acoustic environments, physical activity levels, and pleasantness on evaluations of the thermal and acoustic comfort in outdoor open spaces. Survey questionnaires and on-site measurements were used to quantitatively assess human thermal and acoustic comfort in outdoor spaces. The following findings were obtained in this study. The acoustic environment affected the thermal sensation, where reducing excessive outdoor noise levels could enhance thermal comfort. Increasing the physiological equivalent temperature amplified the acoustic sensation. Individuals reported the most comfortable acoustic perception outdoors at a physiological equivalent temperature of 30.1°C. Reducing both the thermal and acoustic indices improved the overall comfort to some extent. Decreasing physical activity levels by an appropriate amount enhanced the thermal comfort, acoustic comfort, and overall comfort. Finally, maintaining a sense of pleasantness was conducive to increasing the thermal comfort, acoustic comfort, and overall comfort. In states of moderate and pleasurable feelings (pleasantness level = 0, 1, 2, 3), increased acoustic comfort and pleasantness combined significantly enhanced the thermal comfort.

Nonlinear Forced Vibration of Functionally Graded Graphene-Reinforced Composite (FG-GRC) Laminated Cylindrical Shells under Different Boundary Conditions with Thermal Repercussions

The key aim of this research is to develop an analytical model for the forced vibration of graphene-reinforced composite (GRC) cylindrical shell with viscous damping and thermal environment effects under several boundary conditions. The prescribed mechanical and thermal characteristics of the GRC layer are evaluated utilizing a micromechanical extended Halpin–Tsai technique. Further, the governing equations are determined to be grounded on the shear deformation theory (SDT) with the von Kármán-form in terms of the geometric nonlinearity. The basic nonlinear partial differential governing equation is transformed into a nonlinear ordinary differential equation with the Galerkin-based method. The resulting ordinary governing differential equations are systematically solved based on the multiple scales scheme in order to obtain the nonlinear forced vibration frequency response of the laminated GRC cylindrical shell in the presence of damping impact and subjected to multiple boundary conditions. The validation of the obtained expressions is achieved by comparing them with the available literature data where the comparison revealed a clear consistency between them. Moreover, a parametric investigation is provided to illustrate the impacts of the distribution of graphene layers, elastic foundation coefficients, damping ratios, temperature effects and dimensionless radial excitation amplitude on the forced nonlinear amplitude-frequency ratio responses for a functionally-graded graphene-reinforced composite (FG-GRC)-layered cylindrical shells. The analytical outcomes indicate that the different distribution types of graphene, elastic foundation coefficients, damping ratios, temperature, and radial excitation parameters have a noteworthy impact on the frequency–amplitude behaviors of an FG-GRC-layered cylindrical shell. In addition, the new insights gained from this research might contribute to a deeper understanding of the nonlinear forced vibration responses in subsequent analysis and design techniques for giving appropriate benchmark findings.

Static package design thorough thickness stretching and thermal environment effects for porous micro-scaled plates with piezoelectric nanocomposite patches

Static package design thorough thickness stretching and thermal environment effects for porous micro-scaled plates with piezoelectric nanocomposite patches

Effects of thermal environment on body temperature rhythm and thermal sensation before and after getting into bed: A laboratory study in Shanghai, China

Body temperature rhythm serves as a crucial bridge connecting thermal environment and sleep rhythm. While previous studies have extensively confirmed the significant effects of thermal environment on sleep process, a quantitative exploration elucidating the relationships between sleeping thermal environment and body temperature rhythm has persistently been absent. This research aimed to investigate the persistent effects of three stable thermal environments (16 °C, 20 °C and 24 °C) on body temperature rhythm and thermal sensation during complete sleep process. In a laboratory with strictly controlled environment, 14 participants underwent a continuous four-day sleep experiment over a two-month period. Throughout three distinct phases (pre-bed sitting, awake lying in bed, and sleep after lights-off), core body temperature at gastro-intestinal tract, as well as skin temperature at nine specific locations, were continuously monitored. Concurrently, regular questionnaires were employed to periodically collect data on participants’ thermal sensation. The data confirmed that (1) three hours after lights-off, core-to-skin temperature gradient consistently fluctuated around 2 °C across three conditions, and this observation may aid in elucidating the physiological significance of sleeping thermal environment; (2) thermal environment before getting into bed exerted a significant influence on body temperature rhythm and can further regulate the duration of sleep onset latency; (3) bedding system significantly diminished the impact of thermal environment on body temperature rhythm, and future bedding microenvironment deserves more attention; and (4) existing methods for sleeping thermal sensation evaluation varying degrees of limitation, and a novel prediction method was proposed. In general, this study provided valuable insights for the design and regulation of bedroom thermal environment from a thermophysiological perspective.

Plasma Analyzer for the Chinese FY-3E Satellite: In-Orbit Performance and Ground Calibration

The plasma analyzer (PMA) on the Fengyun-3E (FY-3E) meteorological satellite series is a critical sensor of the space environment monitoring package that is capable of the comprehensive in situ detection of the thermal plasma environment and surface discharge effects. In this paper, we conducted a thorough evaluation of the PMA’s performance and reliability through a combination of ground-based laboratory calibration and in-orbit testing. During the ground-based calibration, the PMA underwent assessments for the energy range, field of view (FOV), and measurement accuracy, and obtained the detection accuracy and the geometric factors. During the in-orbit testing, the PMA successfully obtained the typical distribution characteristics of low-energy ions and electrons in orbital space regions, as well as the precipitating particles in the middle and high latitudes of both hemispheres. Notably, the PMA observed an expansion of the particle distribution in the high-latitude regions during a moderate geomagnetic storm. The results from both the ground-based calibration and in-orbit testing demonstrated that the PMA met the requirements for thermal plasma detection, with reliable and scientifically valid in-orbit detection data. These results provide a crucial foundation for studying spatial weather variations, improving the accuracy of space environment forecasts and enhancing disaster detection and monitoring capabilities.

Effect of thermal environment on the free vibration of functionally graded carbon nanotubes cylindrical-conical shell

This research analyzes the influence of temperature changes on the vibration of single-walled carbon nanotubes (SW-CNTs) composite joined conical-cylindrical shells. The governing dynamic equations of temperature-dependent CNTs with initial thermomechanical stresses are established using the Love shell assumptions and classical shell theory. The initial thermomechanical stresses are derived from the linear membrane approach method. Two possibilities are assumed for the calculation of temperature change: a uniform temperature distribution and steady-state heat transfer by conduction through the thickness of the shell. The initial thermomechanical stresses are determined using the linear membrane approach. The generalized differential quadrature (GDQ) method is used to solve the equations after combining it with continuity conditions between the conical part and the cylindrical part and various boundary conditions. After validating the natural frequency and the different types of temperature distribution with the studies of other researchers, the effects of semi vortex of the cone, the volume fraction, and the type of distribution on the temperature rise are given as the results. The type of temperature distribution has the greatest influence among the parameters.

Parental early life environments drive transgenerational plasticity of offspring metabolism in a freshwater fish (Danio rerio).

Parental experiences can lead to changes in offspring phenotypes through transgenerational plasticity (TGP). TGP is expected to play a role in improving the responses of offspring to changes in climate, but little is known about how the early lives of parents influence offspring TGP. Here, we use a model organism, zebrafish (Danio rerio), to contrast the effects of early and later life parental thermal environments on offspring routine metabolism. To accomplish this, we exposed both parents to either constant optimal (27°C) or environmentally realistic diel fluctuating (22-32°C) temperatures during early (embryonic and larval) and later (juvenile and adult) life in a factorial design. We found significant reduction of routine metabolic rates (greater than 20%) at stressful temperatures (22°C and 32°C) after biparental early life exposure to fluctuating temperatures, but little effect of later life parental temperatures on offspring metabolism. This reduction reflects metabolic compensation and is expected to enhance offspring body sizes under stressful temperatures. These changes occur over and above the effects of parental environments on egg size, suggesting alternate non-genetic mechanisms influenced offspring metabolic rates.

Unravelling the effects of dynamic urban thermal environment on utility-scale floating photovoltaic electricity generation

The utility-scale photovoltaic systems have been widely integrated for sustainable urban development. However, the varying photovoltaic conversion efficiency (PVCE) affected by dynamic urban thermal environment causes uncontrollable uncertainty in electricity generation, which challenges installed-capacity planning and load-balancing operations. To tackle this problem, this study develops a PVCE estimation model containing four hierarchical modules. First, photovoltaic surface temperatures (PVSTs) are retrieved from satellite imagery, and meteorological features are collected to represent the dynamic thermal environment. Second, the contribution of each feature to the PVST estimation is evaluated, referring to the Mean Decrease in Impurity, Permutation Importance, and SHapley Addictive exPlanations. Third, machine learning models using Support Vector Machine, Random Forest, and XGBoost are developed to establish robust regressions between PVSTs and the selected features, enabling an accurate estimation of PVST spatio-temporal heterogeneity. Finally, the spatio-temporally corresponding PVCEs are calculated, resulting in a refined estimation of annual electricity generation. The investigation of four floating PV systems in Singapore found that their PVCEs vary insignificantly throughout the year, which is probably because of its stable climate and the cooling effect of water. The proposed model is simple and effective, demonstrating its impact on PV potential estimation when the urban thermal effect becomes significant.

A Kirchhoff Plate Model for Longitudinal Vibration Analysis of Restrained Nanoplate Including Thermal Effects

This work attempts to apply the Kirchhoff plate theory to find out the vibrational analyses of a nanoplate incorporating thermal effects. The effects of thermal environments on the natural frequency of longitudinal vibration of restrained nanomaterials, especially for restrained nanoplates, have not been investigated, and most of the previous research has been carried out for unrestrained nanoplates. Therefore, it must be emphasized that the vibrations of restrained nanoplate, including thermal effects, are novel and applicable to the nanodevices, in which nanoplates act as the main structure of the nanocomposite. A novel motion and frequency equation are derived using the Kirchhoff plate model. The present study illustrates that a nanoplate’s longitudinal vibration characteristics strongly depend on the temperature change and stiffness coefficients. The numerical results clearly show that the longitudinal natural frequencies of the nanoplate are less than unity for both cases of low and high temperatures. This means that applying the Kirchhoff plate model for restrained nanoplate analysis would lead to an over-prediction of the frequency if the small thermal stress effect is neglected. Finally, the investigation of the restrained and thermal impact on longitudinal vibration of nanoplates may be used as a valuable reference for the application and the design of nanoelectronics and nano-drives devices, nano-oscillators, and nano-sensors, in which nanoplates act as essential elements.

Quantifying the Spatial Heterogeneity Relations Between Thermal Environment Effects and Influencing Factors Based on Geodetector in Central City of Chengdu

To address the current situation that urban thermal environment research lacked comprehensive assessment and analysis from natural-social multidimensional factors, this study analyzed the evolution characteristics of thermal environment effects in the central urban area of Chengdu from 2004 to 2019 based on multi-source data. A total of seven influencing factors of natural and social factors that were highly associated with the urban thermal environment were selected, and the influencing factors of spatial differentiation of land surface temperature (LST) and their interactions were studied by applying Geodetector. The results showed that: (1) the heat island in the central city of Chengdu from 2004 to 2019 was radiating outward from the center, and the spatial development spine of the thermal environment remained in the "southeast-northwest" direction, with a significant shift of the center of gravity of the thermal environment from 2011 to 2019; (2) the average LST from 2004 to 2019 increased from 36.57℃to 40.64℃, and the total area of heat island area increased from 641 km2 to 958 km2. overall, it showed a shift from sub-medium zone and medium temperature zone to sub-high temperature zone and high temperature zone, and the urban heat island effect tended to enhance; (3) the nighttime light intensity had the largest amount of contribution to the spatial differentiation of LST, and social factors had a more important position relative to natural factors in influencing the urban thermal environment but the amount of contribution from natural factors kept increasing.

Effects of thermal environment and air quality on outdoor thermal comfort in urban parks of Tianjin, China.

The comfort level of outdoor thermal environments is affected by several factors. Previous studies of thermal comfort have generally investigated the main microclimatic factors as dependent variables, such as the temperature, wind speed, humidity, and thermal radiation, but the influence of the air quality has rarely been explored. In this study, we acquired meteorological element observations and conducted questionnaire surveys in Peach Blossom Park, Hebei University of Technology, and Xigu Park in Tianjin. We analyzed the effects of the outdoor air quality and thermal environment on the thermal comfort in order to provide a theoretical basis for comprehensive evaluations of the outdoor environment and the mechanism. The results showed that thermal resistance of clothing and ambient temperature followed a negative step change, where people generally reduced the minimum amount of clothing when the temperature exceeded 28 °C. One unit change in the thermal sensation vote (TSV) occurred for every 11 °C rise in the physiological equivalent temperature (PET). The neutral PET was 21.68 °C, and the comfortable PET was about 23 °C. The air quality index (AQI) and air satisfaction were negatively correlated, and satisfaction decreased by 1 unit for every change of 230 AQI. The transitional season was most comfortable when the temperature felt slightly cool (TSV = -0.70). The neutral TSV was 0.507 in the summer and -0.334 in the winter. Air quality had a significant effect on the thermal comfort vote (TCV) (p = 0.0485 < 0.05). The effect of PET on TCV was highly significant (p < 0.01).

Magnetic field and thermal environment effects on sound transmission loss of double-walled cracked piezoelectric cylindrical nanoshells

Based on a non-local strain gradient theory (NSGT), this article analytically studies the sound transmission loss (STL) performance of a special type of double-walled partially cracked piezoelectric nanoshell structures of cylindrical shape undergoing initial electric potential and longitudinal magnetic field. The structure, which includes a specific number of axial and circumferential surface cracks, is struck by a plane wave in a thermal setting. Such cracks have minimal size compared to the nano-shell structure as a whole, minimizing the effects of curvature for this problem. The first-order shear deformation theory (FSDT) is utilized to explain the displacement components, and Hamilton’s concept is applied to obtain the coupled vibroacoustic equations that are used to generate the governing equations of the system for the two crack types, giving us an idea of the resulting structural stiffness in the presence of cracks using coefficients of crack compliance that are derived from the line spring model (LSM). The mechanical and acoustic properties are then checked to see their effect on the system response followed by a series of validation case studies. This evaluation also allows one to optimize a similar structure by selecting appropriate external parameters such as electric voltage, magnetic field intensity, different crack types, nonlocal and strain gradient parameters, variations of temperature, and incident angle of sound waves.

Nanostructure modeling for thermal properties of zigzag carbon nanotubes

In the nanotube design application, the case of dynamic damage is key problem attracted many engineering researchers. The thermal effect on the axial buckling of zigzag double walled carbon nanotubes (DWCNTs) embedded in an elastic medium is investigated in this article based on the nonlocal Timoshenko beam model. The effects of the van der Waals (vdW) forces between inner and outer tubes and the surrounding elastic medium are taken into account based on a Winkler model. Moreover, a modified molecular mechanics model is developed to study the effect of thermal environment on mechanical properties of zigzag double carbon nanotubes, in which the covalent bonds are traded as a truss. It is found that the axial buckling properties of zigzag DWCNTs increase with the increase of the temperature at room or low temperature, while the axial buckling properties of zigzag DWCNTs decrease with the increase of the temperature at high temperature. Moreover, the buckling strain considering the thermal effect is larger than the buckling strain ignoring the effect of temperature change, and increases with the increase of temperature change, which is contrary to the case of high temperature.

Combined effects of thermal and acoustic environments on outdoor human comfort in university campus

Urban outdoor public spaces are complex systems and the thermal and acoustic environments are the two main factors that affect their overall comfort. Many studies have analyzed the effects of the thermal environment and acoustic environment separately from different perspectives, while further research is required to understand the combined effects between two or more factors on the comfort in outdoor public spaces. In this study, we chose a university campus and assessed the combined effects of thermal and acoustic environments on human comfort at several spaces. Results showed that thermal evaluation is mainly affected by PET and acoustic evaluation is mainly affected by LAeq at most of the sites. Apart from that, interactive effects are only significant on TSV at PA, SQ and on OCV at AC. Prediction made by linear regression model revealed that there're obvious discrepancy on both thermal and acoustic evaluation between predictions and actual conditions. For overall comfort evaluations, linear regression analysis suggest that people feel “moderate” under ideal conditions where there're “no thermal stress” and LAeq =50 dB(A). The OCVeq chart analysis showed that the variation trend was separated by 0 with linear and centralized on each side, giving the hints that people judge their overall comfort and discomfort differently. This study concludes that it's possible to predict human comfort based on knowledge about the current thermal and acoustic environment, but due to limitations of this study, the reliability and accuracy requires further researches to confirm.

Evaluating the impact of sky view factor and building shadow ratio on air temperature in different residential and commercial building scenarios: A case study of Beijing, China

The urban building morphology is one of the most important effects of urban thermal environment (UTE). The sky view factor (SVF) is a crucial structure index of buildings and it combines height and density attributes. These attributes have impacts on the air temperature(Tair). However, there are few studies on the association between SVF and Tair across block scales. In this paper, we designed ten scenarios according to the characteristics of Beijing's commercial and residential buildings. Furthermore, we used ENVI-met, a microclimate simulation model, to simulate the Tair in designed scenarios and evaluate the impact of SVF on the Tair of each component. A number of significant observations were noted based on the experimental results: (1) from 10:00 to 17:00, there is a positive correlation between SVF and Tair; from 18:00 to 9:00 the next day, there is a negative correlation between SVF and Tair (2) the relationship between building shadow ratio (BSR) and Tair is not a single negative correlation: at sunrise, BSR is the maximum in a day, but the cooling effect of BSR on Tair is not obvious because of the weak solar radiation. In addition, the arrangement of building directions has a great influence on the relationship between BSR and Tair (3) for the same building scenario, BSR decreases with the increase of SVF (4) the synergistic effect of SVF and BSR on Tair in the daytime can be divided into two periods, the separation time points are 7:00 and 14:00. This study can provide instructions for urban design in optimizing building layout and mitigating the urban heat impact on human health.

Modeling and Free Vibration Analysis of Variable Stiffness System for Sandwich Conical Shell Structures with Variable Thickness

This paper presents modeling and free vibration analysis of variable stiffness system for the truncated sandwich conical shell made of porous aluminum foam core with variable thickness and carbon fiber face sheets under the simply supported boundary condition. The thickness of the core layer varies along the longitudinal direction. Five different types of porosity distribution of the aluminum foam core, which contains Type-X, Type-O, Type-U, Type-V and Type-[Formula: see text] along the direction of thickness, are considered. Considering the effect of thermal environment, we derive the nonlinear dynamic equations based on first-order shear deformation theory and Hamilton’s principle, and obtain the natural frequencies of the system by employing the Galerkin method. The comparison and validation are conducted by contrast with the determined results of the literature. The influences of porosity distribution pattern, porosity coefficient, the total number of layers, temperature increment, semi-vertex angle, the exponent of thickness function, the minimum radius-thickness and length-thickness ratio of the core layer on the natural frequencies, modal and mode shapes are studied comprehensively.

The effect of thermal and cryogenic environments on the impact performance of aluminum-glass fibers/epoxy laminated composites

In this research work, the effect of various environments on the impact properties of fiber metal laminates was investigated. To do so, in the first step, the 2024 aluminum layers were surface modified with the etching method. Then, the various glass fibers/epoxy composites with the configurations of (0°/0°/0°/0°, 90°/90°/90°/90°, +45°/−45°/−45°/+45° and 0°/90°/90°/0°) were sandwiched between two aluminum sheets. In the following, these samples were aged under thermal cycling (between 25 and 100 °C), isothermal aging at the temperature of 100°C, cryogenic cycling (between −196 and 25 °C), and cryogenic isothermal aging at the temperature of −196°C. To understand the effect of various aging methods on the mechanical features of these structures, the Charpy impact test was performed. Also, the failure mechanisms and related phenomena were assessed by visual observations and microstructural investigations. In the first steps of thermal aging, the impact strength of FMLs was improved, which the highest of that being 46.9%. In the higher cycles or exposing times, the impact strength showed reducing trends, due to thermal degradations of the epoxy matrix. The cryogenic cycling in the high cycles reduced the impact strength of FMLs. But in the cryogenic isothermal condition, in some cases, the improvement in the impact strength was seen, which the highest of that being about 43.4%.

Dynamical responses of variable generatrix profile and thickness ceramic-matrix composite shells under electro-thermo-mechanical effects

In this paper, new structures of shells have been proposed with complex profiles and thicknesses varying through the length direction subjected to a thermal environment. The inner and outer surfaces of the shells are bonded to the piezoelectric actuators with changes of various voltages. The nonlinear motion equations of variable generatrix profile and thickness (VGPT) shells are solved to investigate the nonlinear vibration and chaotic responses using the theory of elasticity and Von Karman-Donnell’s geometrical nonlinearity assumption. Four kinds of VGPT shells are combined by two types of complex profiles and two patterns of thickness distribution. The used materials are made of Silicon carbide (SiC) and Borosilicate. Galerkin’s method is applied to solve the systems of differential equations and then the fundamental frequencies and nonlinear dynamic behaviors can be found. The effects of material (coefficient k), geometrical parameters, thickness, piezoelectric layers, and thermal environment on the dynamic responses of VGPT shells are examined and presented in tables and graphs.

CFD Analysis of Solar Greenhouse Thermal and Humidity Environment Considering Soil–Crop–Back Wall Interactions

In the study of solar greenhouses, microclimate, soil, and back walls have an important influence on the greenhouse thermal environment because of their good heat storage and release characteristics. The transpiration of crops makes indoor humidity increase sharply, which is the main factor affecting indoor humidity distribution. Therefore, it is of great significance to grasp the microclimate change law of solar greenhouses and study the coupling effect of thermal and humidity environment. In this paper, based on computational fluid dynamics (CFD), a three-dimensional model of the thermal and humidity environment of a solar greenhouse is established, and the indoor temperature and humidity distribution under the influence of soil, crops, and back walls are considered. The CFD model initialization uses binary fitting functions to fit the temperature distribution of soil, back wall, and air. The distribution law of the temperature field and relative humidity field of the solar greenhouse under three different working conditions is simulated, that is, the insulation is uncovered and the ventilation window is closed during the day (G1), the insulation is uncovered and the ventilation window is opened during the day (G2), and the insulation is put down and the ventilation window is closed at night. (G3). The results show that the simulation results are in good agreement with the actual results under the three working conditions, and this paper can provide a reference for the improvement of the greenhouse structure and environmental regulation.