Rate Of Temperature Change Research Articles

The experimental implications of the rate of temperature change and timing of nutrient availability on growth and stoichiometry of a natural marine phytoplankton community

AbstractClimate change increases the need to understand the effect of predicted future temperature and nutrient scenarios on marine phytoplankton. However, experimental studies addressing the effects of both drivers use a variety of design approaches regarding their temperature change rate and nutrient supply regimes. This study combines a systematic literature map to identify the existing bias in the experimental design of studies evaluating the phytoplankton response to temperature change, with a laboratory experiment. The experiment was designed to quantify how different temperature levels (6°C, 12°C, and 18°C), temperature regimes (abrupt vs. gradual increase), timings of nutrient addition (before or after the temperature change) and nutrient regimes (limiting vs. balanced) alter the growth and stoichiometry of a natural marine phytoplankton community. The systematic map revealed three key biases in marine global change experiments: (1) 66% of the studies do not explicitly describe the experimental temperature change or nutrient regime, (2) 84% applied an abrupt temperature exposure, and (3) only 15% experimentally manipulated the nutrient regime. Our experiment demonstrated that the identified biases in experimental design toward abrupt temperature exposure induced a short‐term growth overshoot compared to gradually increasing temperatures. Additionally, the timing of nutrient availability strongly modulated the direction of the temperature effect and strength of growth enhancement along balanced N : P supply ratios. Our study stresses that the rate of temperature change, the timing of nutrient addition and the N : P supply ratio should be considered in experimental planning to produce ecologically relevant results as different setups lead to contrasting directions of outcome.

Climate Change-based Estimation of Non-working Days for Construction Plan

Significant global climate change has recently occurred, and an increase in natural disasters is predicted in the future. Currently, climate change, such as heat waves, heavy rain, and typhoons, affects severely vulnerable regions, such as Korea. Consequently, it has various effects on the construction environment and is expected to make a significant difference in the progress of future construction work. Therefore, this study aimed to determine how climate change can affect future construction work restricted by weather conditions and conducted a study on how future construction schedules should be adjusted. After performing a bias correction on the future climate scenarios of CMIP6, the latest scenario released through the Earth System Model (ESM), we compared and analyzed the weather observation data with SSP245 and SSP585. It was calculated how much the rate of temperature change would impact the construction environment in the future. As a result of the analysis, both the SSP245 and SSP585 scenarios show a tendency that As a result of the analysis, both the SSP245 and SSP585 scenarios show a tendency that the number of non-working days (NWD) for construction increases as the period increases from the base. In addition, the results indicated that the number of days of increase for SSP585 was higher than that for SSP245. The number of NWD was found to increase in the future under the SSP585 scenario, which takes extreme climate change into consideration. The construction period calculation is anticipated to undergo significant changes as a result of this outcome, which has a substantial impact on the construction plan and execution.

Mechanical performance analysis of double-block ballastless tracks in intercity railways under temperature and train loads

The coupling effect of environmental temperature and moving train loads significantly impacts the mechanical performance of ballastless tracks on intercity railways. To further explore the thermal performance of double-block ballastless tracks (DBBTs) under complex temperature conditions, an initial test was conducted on a 1/4 geometric scale DBBT model across three temperature scenarios. Following the validation of these experimental results, thermal-mechanical coupling models for two types of DBBTs (unitized and longitudinal) on subgrades with two different boundary constraints were developed. These models aimed to examine their mechanical responses under train speeds ranging from 120 km/h to 200 km/h and their interaction with high daily temperatures. The findings indicate that temperature change rates in the track slab are significantly higher than those in the supporting layer, with the stresses in the limiting groove and supporting layer being the highest and lowest, respectively. The relationship between temperature and stress in the track slab follows a second-order quadratic polynomial. Additionally, measured longitudinal displacement results are smaller than theoretical predictions, especially under dropping temperatures. Furthermore, under all three train speeds, both dynamic stress and displacement are higher in the longitudinal DBBT than in the unitized DBBT. The coupling effect of temperature and moving train loads notably increases the dynamic stress in both types of DBBTs, with a more pronounced effect on the dynamic displacement of the longitudinal DBBT compared to the unitized DBBT.

Comprehensive spatiotemporal evaluation of urban growth, surface urban heat island, and urban thermal conditions on Java island of Indonesia and implications for urban planning

Urban heat island (UHI) and thermal comfort conditions are among the impacts of urbanization, which have been extensively studied in most cities around the world. However, the comprehensive studies in Indonesia in the context of urbanization is still lacking. This study aimed to classify land use and land cover (LULC) and analyse urban growth and its effects on surface urban heat islands (SUHIs) and urban thermal conditions as well as contributing factors to SUHI intensity (SUHII) using remote sensing in the western part of Java Island and three focused urban areas: the Jakarta metropolitan area (JMA), the Bandung and Cimahi Municipalities (BC), and the Sukabumi Municipality (SKB). Landsat imagery from three years was used: 2000, 2009, and 2019. Three types of daytime SUHII were quantified, namely the SUHII of urban central area and two SUHIIs of urban sprawl area. In the last two decades, urban areas have grown by more than twice in JMA and SKB and nearly 1.5 times in BC. Along with the growth of the three cities, the SUHII in the urban central area has almost reached a magnitude of 6 °C in the last decade. Rates of land surface temperature change of the unchanged urban pixels have magnitudes of 0.25, 0.15, and 0.14 °C/year in JMA, SKB, and BC, respectively. The urban thermal field variance index (UTFVI) and discomfort index (DI) showed that the strongest SUHI effect was most prevalent in urban pixels and the regions were mostly in the very hot and hot categories. Anthropogenic heat flux and urban ratio have positive contributions to SUHII variation, while vegetation and water ratios are negative contributors to SUHII variation. For each city, the contributing factors have a unique magnitude that can be used to evaluate SUHII mitigation options.

Transient characterization of the mode switching process in the reversible solid oxide cell stack

Reversible solid oxide cells (RSOCs) is a promising energy storage and conversion technology requiring frequent switching between fuel cell mode and electrolysis mode in practice. Unfortunately, it may cause a large current density undershoot that has irreversible damage to the RSOC. Therefore, understanding the transient behaviors of the RSOC is critical for its efficient and durable operation. A three-dimensional transient model of a 30-cell SOC stack with an external manifold is established. From SOFC to SOEC, the mass transfer lag and slow heat transfer cause the current density of the stack requiring 2500 s to reach a steady state. And the bottom inlet way and the external manifold structure cause differences in the current density, molar fraction and temperature variation with time between different cells. The upper cells show a slower mass transfer rate and undergo greater temperature changes. The inconsistent temperature change gradients and temperature change rates among different cells will inevitably produce changing thermal stresses and bring irreversible mechanical losses to the stack. Similar transient characteristics are observed when switching from SOEC to SOFC. However, it takes longer time (3200 s) to achieve the final steady state.

A novel control strategy to neutralize internal heat source within solid oxide electrolysis cell (SOEC) under variable solar power conditions

The integration of solid oxide electrolysis cells (SOECs) with a photovoltaic (PV) system presents a viable method of storing variable solar energy through the production of green hydrogen. To ensure the safety and longevity of SOEC amidst dramatic fluctuations in solar power, control strategies are needed to limit temperature gradients and rates of temperature change within the cell. Recognizing that the supply of the reactant influences the current, a novel control strategy is developed to modulate internal heat source in the SOEC by adjusting the steam flow rate. The effectiveness of this strategy is assessed through numerical simulations conducted on a coupled PV-SOEC system using actual solar irradiance data. The irradiance data are recorded at two-second intervals to account for rapid changes in solar exposure. The results indicate that conventional control strategies, which increase airflow rates, are inadequate in effectively suppressing the rate of temperature variation in scenarios of drastic changes in solar power. In contrast, our proposed strategy demonstrates precise management of SOEC internal heat generation, thus reducing the temperature gradient and variation within the cell to less than 5 K cm−1 and 1 K min−1, respectively, and maintaining a high electricity-to-hydrogen conversion efficiency of 94.9%.

Cooling characteristics of thermochromic powder modified sand fog seal on asphalt pavement in summer high-temperature environment

Reversible optical response can occur in thermochromic materials with temperature changes, which has great potential in the field of pavement temperature regulation. The thermochromic sand fog seal (TP-SFS) was proposed in this study, which has the functions of pavement repair and temperature control. In this study, different types (red, blue, black) and contents (0 %, 2 %, 4 %, 6 %, and 8 %) of thermochromic powders (TP) were used to prepare TP-SFS. Secondly, the cooling characteristics of different TP-SFS was explored from the perspectives of temperature change rate, cooling temperature, and temperature gradient, based on the designed indoor and outdoor multi-cycle illumination test. Then, the prediction model of the outdoor cooling effect was proposed. In addition, the conservation and environmental benefits of different TP-SFS were calculated according to the empirical formula. It is found that after spraying TP-SFS, the heating rate of pavement decreases and the cooling rate increases. The cooling effect at 2 cm depth of the pavement sprayed with TP-SFS is the most significant, and the temperature gradient of the pavement is reduced. The cooling temperature of the pavement increases with the increase of TP content. In the outdoor environment, the more obvious cooling effect occurs as the process of pavement temperature increases and decreases. Additionally, the reliability of the designed indoor test is high, and the cooling effect of TP-SFS in outdoor environment can be well predicted according to the proposed model. The results of empirical formula calculation show that TP-SFS has a significant effect on delaying rutting development and alleviating urban heat island effect.

Thermal transfer rate is slower in bigger fish: How does body size affect response time of small, implantable temperature recording tags?

AbstractThe recent miniaturisation of implantable temperature recording tags has made measuring the water temperatures fish experience in the wild possible, but there may be a body size‐dependent delay in implanted tag response time to changes in external temperature. To determine whether fish body size affects the response rate of implanted temperature tags, we implanted 20 Salvelinus fontinalis (127–228 mm fork length (FL), 15.1–120.4 g) with temperature recording tags and subjected them to rapid temperature changes (±8°C in less than 2 seconds) in the laboratory. We found that thermal transfer rates, and the lag in temperature tag response rate, was positively correlated with fish size, but the direction of temperature change (colder or warmer) had no significant effect. In fish exposed to a slower rate of temperature change (2°C h−1) implanted tags did not show a response lag. Understanding the limitations of this important technology is crucial to determining the utility of the data it produces and its ability to accurately measure fish thermal experience in the wild.

Monitoring changes in hydric properties of treated stone material with conservation products by time-sequential IR thermography

A methodological approach for a semi-quantitative non-destructive testing (NDT) of the effects on hydric properties after the application of different conservation treatments (commercial ethylsilicate and siloxane compounds with consolidant, water repellent or consolidant + water repellent properties) is presented in this study. The NDT used for this purpose is a simplified method of time-sequential infrared thermography (IRT) on stone (granite and marble, treated and untreated) from the Roman theatre of Merida (Spain), which was listed by UNESCO as World Heritage Site in 1993.As water evaporation modifies temperature intensely, IRT enables monitoring the response of the stone samples during water absorption-evaporation processes. The comparative analysis between treated and non-treated specimens was performed by calculating the rate of surface apparent temperature change (ΔoC/h) value. The capillary rising test, monitored by IRT, clearly showed a different response of the samples treated with water-repellent treatments, proving their efficiency. Samples treated with organosilicic compounds showed a large and rapid drop in apparent surface temperature, indicating that water accesses rapidly.Results from the evaporation test also show this difference. The surface apparent temperature increased immediately in samples with water-repellent treatments, in which water does not enter inside stone, but remains on the surface. Samples with ethyl silicate, again, show a greater difference with respect to untreated samples, taking longer to recover surface apparent temperature, because the water is retained inside the stone for longer.This study proved simplified time-sequential IRT as a reliable technique for assessing the efficacy of conservation treatments applied to stone materials in laboratory.

Thermoregulation of understory birds in lowland Amazonia

Understanding the capacity for thermoregulation is critical for predicting organismal vulnerability to climate change, especially in lowland tropical rainforests, where warming conditions combine with high humidity and limited elevational or latitudinal refugia. Here, I focused on nine species of ground‐foraging insectivorous birds in the genus Myrmoderus, Myrmornis, Hylopezus, Myrmothera, Formicarius and Sclerurus – sensitive forest specialists characterized by recently documented population declines in both disturbed and undisturbed forests. Using high‐resolution data from loggers deployed on birds and their environment, I examined whether and how birds used thermoregulation and whether ambient water provided cooling opportunities. Variation in the rate of temperature change over the diel cycle suggested that all species employed behavioral and physiological thermoregulation, but some patterns differed by species' phylogenetic relatedness. All species warmed hours before their environment at sunrise, then experienced lower temperature increases at midday relative to the ambient thermal flux. These morning warming periods peaked around sunrise for all but Sclerurus rufigularis and constituted the diel temperature change maxima for five of the nine species. Six species exhibited pronounced oscillations in temperature change consistent with regular bathing around sunset, possibly for thermoregulatory or other purposes. This oscillation was the most prominent feature in the diel thermal flux for all three Sclerurus species and, to a lesser extent, for Myrmoderus ferrugineus, Myrmornis torquata and Myrmothera campanisona. Local rainfall reduced ambient temperatures, and birds experienced stronger cooling in the wet season and with higher rainfall intensity. However, rain‐induced cooling events were markedly absent in all three Sclerurus spp. These results highlight the fundamental role of water in avian thermoregulation and suggest that terrestrial insectivores attempt to maintain thermal homeostasis throughout the diel cycle. The observed thermoregulatory behaviors highlight a potentially critical aspect of their vulnerability – thermal regimes are profoundly altered by forest disturbance, climate change, and their combination.

Enhancing thermal performance of energy storage concrete through MPCM integration: An experimental study

Phase change materials melt and solidify at different temperature ranges called Phase change hysteresis. This phenomenon should be understood and evaluated in order to adequately design energy storage concretes for applications. Although many studies have analyzed the phase change process in pure - phase change materials such as paraffin. However, there is not enough information about the Phase change hysteresis of energy storage concrete. In order to realistically reproduce the working condition of concrete. This study explores phase change hysteresis in energy storage concrete slabs, focusing on the impact of microcapsule concentration and temperature change rate on thermal efficiency. Experiments were conducted to analyze the thermophysical properties, particularly observing the variations in specific heat capacity and phase transition temperatures. Results showed that increasing the microcapsule concentration enhances the specific heat capacity and latent heat of phase change, while faster temperature changes intensify hysteresis effects. Compared with the results of previous studies. Phase change hysteresis is more significant due to the pore and complex structure of energy storage concrete that impedes heat transfer. The experimental latent heat values were approximately 75 % of theoretical predictions, likely due to microcapsule damage and microstructural impacts on heat transfer. The study's findings are crucial for optimizing the thermal performance of energy storage concrete.

Conjugate transient flow and thermal analysis of non-isothermal rubber curing process in autoclave system

Autoclave manufacturing under high pressure and elevated temperature was required to vulcanize the rubber compound applied in the aerospace industry. Nevertheless, few works have comprehensively explored the transient effect of flowing factors on curing efficiency, thermal uniformity, and exergy destruction in autoclave processing. In this study, the three-dimensional model and non-isothermal vulcanization of an autoclave with a built-in combustion chamber were solved by combining the finite volume method and the proposed mixed kinetic model, and exergy destruction was determined to estimate the energy consumption using a direct method. Variations in the Reynolds number (Re), gas pressure (P), temperature, rate of temperature change, and Prandtl number (Pr) were analyzed to improve the unstable thermo-vulcanization and reduce energy consumption in autoclave processing. The results demonstrate that increasing the inlet Re can significantly increase the curing rate while decreasing the temperature difference in the rubber area, and a reduction of 41.89 %−46.62 % for the complete vulcanization time is achieved by changing Re from 105 to 2 × 106; however, adjusting P and temperature has only a minor effect on the heat transfer under constant higher Re. Furthermore, changing the rate of temperature change and Pr is also advantageous for optimizing the curing process and reducing exergy destruction. A minimal non-dimensional exergy destruction rate arises for a given P, rate of temperature change, or Pr when the Re is raised. The knowledge gathered from this research could provide a theoretical foundation for reducing energy consumption and boosting productivity during autoclave curing.

Modeling of water gas shift reaction using neural network trained on detailed kinetic mechanisms

For the optimization of a chemical reactor or its control, computational fluid dynamics (CFD) that considers accurate reaction models is effective. Although detailed kinetic mechanisms can accurately predict gas-phase reactions, integrating them with CFD is too computationally expensive. In contrast, global reactions have lower computational costs but significantly reduced accuracy outside of tuned conditions. This study proposes a method for constructing a model using a neural network to predict the reaction rate of water gas shift reaction based on detailed kinetic mechanisms. It includes techniques to avoid unrealistic solutions inherent to detailed kinetic mechanisms and methods to minimize biases in training data. The neural network input was log-transformed concentrations and inverse temperatures, and the output was the logarithm of the absolute value of the reaction rate and direction, enabling the prediction of bidirectional reactions over a wide temperature range. The quality of the dataset significantly impacted the accuracy of the neural network. Using a dataset with less bias in chemical species concentrations, the model achieved accuracy similar to detailed models while facilitating an over 400 times faster computation. The study also discussed the impact of temperature change rate, showing that at about 72 K/min, the detailed kinetic mechanism's solution can be accurately replicated. Still, at 720 K/min, the radical concentration deviates from the quasi-steady state, leading to discrepancies. This study opens up new possibilities for computational methods in the prediction and optimization of chemical reactions.

Development of a novel composite phase change material based on paints and brick for energy storage applications in agricultural greenhouses

This study addresses challenges associated with supercooling, phase separation, and inadequate thermal properties in Na2SO4·10H2O (SSD) by expanding the application of inorganic hydrate salt phase change materials within agricultural greenhouses. A novel composite phase change material, Na2SO4·10H2O-Al2O3 (NAPCM), was successfully synthesized using the vacuum impregnation method. NAPCM was strategically incorporated into paints and hollow bricks, leading to the creation of innovative phase change paint and phase change bricks designed for efficient thermal energy storage in agricultural greenhouses. The investigation revealed the homogeneous dispersion of porous Al2O3 particles in SSD, effectively preventing phase separation in NAPCM and ensuring its durable shape stability. The interaction between SSD and porous Al2O3 remained purely physical, with porous Al2O3 acting as an effective modifier to adjust various thermal properties of SSD. Optimal mass ratio determination for the combination of paint and NAPCM particles resulted in a 9:1 ratio, ensuring the uniform distribution of NAPCM particles within the paint matrix. This achieved a particle size averaging 290.93 μm with no discernible leakage features. The phase change paint exhibited an impressive solid content of 56.62 %, demonstrating exceptional resistance to water, alkali, salt, and abrasion. In thermal plate testing, the phase change paint significantly decelerated the heating rate. Infrared thermal imaging observations depicted circular areas with temperatures notably lower than their surroundings, indicating NAPCM's ability to impede heat absorption during the heating process, thereby reducing the rate of temperature change. The phase change paint also exhibited a slower cooling rate in the cooling test. Simultaneously, phase change bricks demonstrated superior thermal insulation compared to ordinary bricks. Throughout the heat storage phase, the temperature of the phase change greenhouse wall was lower than that of an ordinary greenhouse, while in the heat release phase, it was higher. The phase change greenhouse, relative to its ordinary counterpart, demonstrated superior insulation effects, creating a warm environment conducive to plant growth. This advancement enhances the energy storage performance of agricultural greenhouses, providing a novel solution for improving energy efficiency and environmental sustainability.

Understanding the extent of detectability and heat transfer characteristics of hidden defects on metal-based envelopes

Metal hidden defects can either be due to corrosion or voids. The extent of their detectability and heat transfer characteristics, particularly with light-colored surface paints and assembly configurations, have been less explored. Observing surface thermal contrast and rate of temperature change (RTC) during “long-pulse” excitation can detect hidden defects regardless of the metal type, paint color, and assembly configuration. However, results from the active thermography approach only indicate their presence and not their location and type. Corroded layers have a lower surface temperature and RTC due to faster heat transfer, while pitted layers have a higher surface temperature and RTC.

Biomimetic 3D printing of composite structures with decreased cracking

The development of tissue engineering and regeneration research has created new platforms for bone transplantation. However, the preparation of scaffolds with good fiber integrity is challenging, because scaffolds prepared by traditional printing methods are prone to fiber cracking during solvent evaporation. Human skin has an excellent natural heat-management system, which helps to maintain a constant body temperature through perspiration or blood-vessel constriction. In this work, an electrohydrodynamic-jet 3D-printing method inspired by the thermal-management system of skin was developed. In this system, the evaporation of solvent in the printed fibers can be adjusted using the temperature-change rate of the substrate to prepare 3D structures with good structural integrity. To investigate the solvent evaporation and the interlayer bonding of the fibers, finite-element analysis simulations of a three-layer microscale structure were carried out. The results show that the solvent-evaporation path is from bottom to top, and the strain in the printed structure becomes smaller with a smaller temperature-change rate. Experimental results verified the accuracy of these simulation results, and a variety of complex 3D structures with high aspect ratios were printed. Microscale cracks were reduced to the nanoscale by adjusting the temperature-change rate from 2.5 to 0.5 °C s−1. Optimized process parameters were selected to prepare a tissue engineering scaffold with high integrity. It was confirmed that this printed scaffold had good biocompatibility and could be used for bone-tissue regeneration. This simple and flexible 3D-printing method can also help with the preparation of a wide range of micro- and nanostructured sensors and actuators.

A novel method to eliminate the symmetry dependence of fiber coils for shupe mitigation

It is a well-known fact that interferometric fiber optic gyroscopes (IFOGs) are easily distorted by thermal effects and distortion results in the degradation of the performance of these sensors. Changing the fiber coil geometry, increasing the winding symmetry, adding fiber buffer layers around the fiber coil, using different modulation methods for multifunctional integrated optic chips, and using special types of fibers, such as photonic crystal fibers, are some alternative solutions for preventing this degradation. This paper, theoretically and experimentally, investigates not only how different types of fiber coil winding methods behave under different rates of temperature change but also presents a novel method, to the best of our knowledge, to eliminate the Shupe effect, without violating the simplest IFOG scheme. This method rules out the importance of the winding symmetry epochally and the need of any extra treatment for the fiber coil to increase the thermal performance of the system. Regardless of the symmetry of the fiber coil winding, the rate error due to the Shupe effect can be reduced to about ±0.05∘/\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\pm 0.05^\\circ /$$\\end{document}h for any rate of temperature change with this new method according to the experimental results.

The prevalence and association of measured and perceived indoor air quality, housing characteristics, and residents’ behavior and health

BackgroundIn social housing buildings, poor indoor air quality (IAQ) has been shown to be more prevalent, and residents living in social housing areas are often more vulnerable and susceptible to adverse health effects from IAQ.AimTo examine the state and the association of measured and perceived IAQ, how housing characteristics and residents' behavior are associated with IAQ, and the association with residents' health.MethodThe HOME-Health study is a cross-sectional study among residents living in social housing in Denmark (n = 432). Seasonal measurements examined the IAQ by a 14-day period measuring carbon dioxide (CO2), temperature (TP), relative humidity (RH), and air change rate. Residents' self-reported behavior, comfort, and health were obtained from a structured interview.ResultsThermal discomfort and draught were the most common challenges. During summer, the mean TP was higher, the mean RH was lower, and residents more frequently reported dry air in homes where it was not possible to create cross ventilation. There were a higher mean CO2 and RH when crowdedness increased, particularly during winter. In addition, the proportion of residents reporting dry air was higher when CO2-level was below 1,000 ppm. When the mean RH-level was above 50%, a higher proportion of residents reported experiencing damp air, and when the mean RH-level was below 40% residents more frequently reported dry air. Perception of bad air quality was higher when the mean CO2-level exceeded 1,000 ppm. Additionally, residents reported being most thermally comfortable when the TP was within the range of 20–20.99°C and least comfortable within a range of 22–22.99°C. The residents' perceived experience of impaired IAQ was associated with negative general health symptoms.ConclusionIt is key that homes have the capability to create cross ventilation in order to allow for proper ventilation and to avoid overheating. When evaluating IAQ it is important to not only consider the measured parameters but to also include the residents' behavior and perception of IAQ as these both are related to the actual IAQ and associated health effects.

Thermochromic Hydrogels with Adjustable Transition Behavior for Smart Windows.

With the fast economic development and accelerating urbanization, more and more skyscrapers made entirely of concrete and glass are being constructed. To keep a comfortable indoor environment, massive energy for air conditioning or heating appliances is consumed. A huge amount of heat (>30%) is gained or released through glass windows. Using smart windows with the capability to modulate light is an effective way to reduce building energy consumption. Thermochromic hydrogel is one of the potential smart window materials due to its excellent thermal response, high radiation-blocking efficiency, cost-effectiveness, biocompatibility, and good uniformity. In this work, polyhydroxypropyl acrylate (PHPA) hydrogels with controllable lower critical solution temperature (LCST) were prepared by photopolymerization. The transition temperature and transition rate under "static transition" conditions were investigated. Unlike "static" conditions in which the transition temperature was not affected by the initial and final temperature and heating/cooling ramp, the transition temperature varied with the rate of temperature change under dynamic conditions. The "dynamic" transition temperature of the PHPA hydrogel gradually increased with the increase of the heating rate. It was the result of the movement of the molecular chains lagging behind the temperature change when the temperature change was too fast. The results of the solar irradiation experiment by filling PHPA hydrogels into double glazing windows showed that the indoor temperature was about 15 °C lower than that of ordinary glass windows, indicating that it can significantly reduce the energy consumption of air conditioning. In addition, a wide range of adjustable transition temperatures and fast optical response make PHPA hydrogels potentially applicable to smart windows.

Simulation of Transient Temperature and Clearance after Shutdown of Aeroengine Based on CFD and FEA Coupled Models

It is crucial to comprehend the heat soak phenomenon, which may result in a significant temperature increase after the shutdown followed by a gradual decrease. This could bring potential risks for the engine including oil coking. The temperature change of engine components dictates the clearance after shutdown, while startup strategies are primarily based on this. A simulation strategy, utilizing computational fluid dynamics (CFD) and finite element analysis (FEA) coupled models, is suggested to investigate the transient temperature and clearance after shutdown. The maximum temperature deviation between the simulation result and experimental data are less than 6%. Flow parameters, including velocity and mass flow rate obtained from the CFD result, were applied as boundaries of the FEA model. Based on the FEA model, transient temperature calculations were also conducted for 20 hours after shutdown. The results indicate that the FEA model demonstrates good agreement with the CFD simulation, with a maximum deviation of less than 5% and at only 0.2% of the simulation time. After the engine shuts down, the stator’s temperature change rate is faster than that of the rotor due to better cooling conditions and relatively small heat capacity. Consequently, the seal clearance increases in the initial period after shutdown and then decreases to a minimum value. The nondimensional minimum clearance can be 0.8 times the cold state value at the location of the high-pressure turbine seal.