Variable Ambient Temperatures Research Articles

Thermal Stress Analysis of Maxillary Dentures with Different Reinforcement Materials Under Occlusal Load Using Finite Element Method

The purpose of this study was to determine the effect of fiber reinforcement materials on the magnitude of stresses in a critical part of the maxillary denture base under thermal and occlusal load. Thermal stress analyses of the models were carried out using the finite element method. The models consisted of bone, soft tissue, interface gap, and maxillary dentures with and without reinforcements. A concentrated occlusal load of 230 N was applied bilaterally on the molar teeth. A 36 °C reference and 0 °C, 36 °C, and 70 °C variable ambient temperatures were applied to the models. CrCo, unidirectional and woven carbon/epoxy, unidirectional and woven glass/epoxy, and unidirectional and woven Kevlar/epoxy were used as reinforcing materials in the maxillary denture base made of PMMA (polymethyl methacrylate). Stress distributions on the maxillary denture’s midline and lateral line direction were evaluated. Maximum stresses in the incisal notch and the labial frenal notch of the maxillary denture were determined. Failure analysis of reinforcement materials used in maxillary dentures was carried out using the Tsai-Wu index criterion. The results obtained show that the thermal properties of reinforcement materials should be considered as an important criterion in their selection.

The Impact of Variable Ambient Temperatures on the Energy Efficiency and Performance of Electric Vehicles during Waste Collection

The market for electric cars (EVs) is growing quickly, which has led to a diversity of models and significant technological advancements, particularly in the areas of energy management, charging, range, and batteries. A thorough analysis of the scientific literature was conducted to determine the operational and technical parameters of EVs’ performance and energy efficiency, as well as the factors that influence them. This article addresses the knowledge gap on the analysis of ambient temperature-related parameters’ effects on electric garbage trucks operating in particular urban traffic conditions for selective waste collection. To optimize vehicle routes, a computational model based on the Vehicle Routing Problem was used, including the Ant Colony Optimization algorithm, considering not only the load capacity of garbage trucks but also their driving range, depending on the ambient temperature. The results show that the median value of collected bulky waste for electric waste collection vans, depending on the ambient temperature, per route is 7.1 kg/km and 220 kg/h. At a temperature of −10 °C, the number of points served by EVs is 40–64% of the number of points served by conventional vehicles. Waste collection using EVs can be carried out over short distances of up to 150 km, which constitutes 95% of the optimized routes in the analyzed case study. The research contributed to the optimal and energy-efficient use of EVs in variable temperature conditions.

Effect of storage conditions on lignocellulose biofuels properties

This article examines the effects of different storage conditions on selected physicochemical properties of three types of agro-biomass pellets: sunflower husks, wheat straw and hemp hurds, and wood pellets. The tests were carried out in a climatic chamber, which allows simulation of real storage conditions, i.e. conditions with high air humidity and variable (±) ambient air temperatures. The results showed higher degradability of agro-biomass pellets compared to woody biomass. The pellets degraded to a less extent at varying ± temperatures than at high humidity (90% RH). After complete moisture saturation, durability decreases for agro-pellets by an average of 9%, while after freezing and defreezing for sunflower husk pellets and woody pellets durability decreases by 2%, and for hemp hurd pellets by 11%. In contrast, strength-by-dropping index for agro-pellets decreased by 20% after being in the environment (30 °C and 90%RH) and 15% under varying temperature conditions. No change in the energy parameters of all pellets in the dry matter was noted. On the other hand, an increase in the moisture content of pellets when they are stored under different environmental conditions results in a decrease in calorific value.

Experimental simulation of temperature non-uniformity in a loaded container along air cargo supply chain: Mango case study

The cooling time of mango boxes (initial temperature 19 °C) at different positions in a Unit Load Device (ULD) located in a test room of 6 °C was monitored. Plaster mangoes were used due to the high perishability of real mangoes. The influence of box designs (closed and top-open) on the cooling time were studied. Both box designs showed shorter Half-cooling time (HCT) at the bottom than at the top. Closed boxes exhibited more uniform temperatures in the ULD. Heat transfer in closed boxes was primarily conduction, while natural convection played a significant role in top-open boxes. Then, the ULD was exposed to variable ambient temperatures to simulate real conditions in an air cargo supply chain. The results demonstrate that the critical step is the airport tarmac; after 2 h for example, the temperature at the top rose to 50 °C (with external air at 32 °C), resulting in a 10 °C increase in the mangoes in the top box.

Electrical properties of low temperature-sensitive coating sensor for fatigue crack monitoring in steel bridges

Coating sensors are used for high-precision monitoring of fatigue cracks in steel bridges. However, the time-variation temperature has a considerable impact on the monitoring precision of fatigue cracking of steel bridges. This study developed a coating sensor using silver-plated copper powder (conductive filler)/acrylate composites as a sensing layer of a coating sensor to monitor fatigue cracks considering variable ambient temperatures. The synthesis and preparation of the composite were presented, and the microstructures of the coating sensor composites were observed by scanning electron microscopy. The bulk conductivity of the sensing layer at different conductive filler contents was measured by the four-probe method to investigate the effect of the concentration of the conductive filler on the electrical conductivity and temperature sensitivity of the resistivity. Moreover, the fractional change in resistivity (FCR) of the sensing layer was tested over a range of temperatures to investigate the temperature sensitivity of resistivity at different conductive filler contents. Finally, the composite with the lowest temperature sensitivity of resistivity was selected to prepare a coating sensor for fatigue crack monitoring. The composite of the sensing layer with 60 wt% of conductive filler content had the lowest temperature sensitivity of resistivity with a minimum value (5.1%) of FCR. The maximum range of the FCR did not exceed 6.4% under cyclic loading and variation-time ambient temperatures. The temperature variation had minimal effects on the output signal of the coating sensor compared with the output signal variation caused by fatigue cracking. The proposed coating sensor can be used for high-precision monitoring of fatigue cracking in steel bridges under different ambient temperatures.

Finite element modeling of early-age temperature development of in-situ concrete under variable ambient temperatures

The early-age temperature rises in in-situ concrete, caused by the exothermic hydration of cement, poses a significant risk of thermal cracking in concrete structures. This issue is particularly critical in large-scale structures, where thermal cracking can lead to serious structural integrity issues. Therefore, the accurate prediction of the concrete hydration temperature development is paramount for predicting and mitigating early thermal cracking in concrete. However, one of the main challenges in predicting in-situ concrete temperatures is the significant effect of variable ambient temperature on cement hydration rates and concrete heat dissipation. To address this challenge, this paper presents a finite element modeling (FEM) approach that accurately predicts the early-age temperature development of in-situ concrete by adequately considering the effect of variable ambient temperatures. The model integrates the heat of hydration of the cement, the impact of ambient temperature variations, and the heat transfer through the concrete and insulation mould. The cement hydration rate under real-life ambient temperatures is simulated using an Arrhenius-based method, which mathematically adjusts the isothermal calorimetry curves to reflect the actual conditions. Additionally, the study investigates the inhibitory effect of Ground Granulated Blast-furnace Slag (GGBS) on the early hydration temperature of concrete, with experimental tests and FEM simulations conducted on concrete mixes where up to 70% of the cement was replaced with GGBS. The validity of the FEM model was confirmed through comparison with concrete semi-adiabatic tests, demonstrating that the model provides accurate predictions of the temperature development of in-situ concrete. Importantly, the results indicate that the adjusted isothermal calorimetry curves successfully capture the ambient temperature effect on the cement hydration rate. The results provide valuable insights for the design of concrete structures, particularly in preventing early-age thermal cracking.

Variable ambient temperature promotes song learning and production in zebra finches.

Current climate change is leading to increasingly unpredictable environmental conditions and is imposing new challenges to wildlife. For example, ambient conditions fluctuating during critical developmental periods could potentially impair the development of cognitive systems and may therefore have a long-term influence on an individual's life. We studied the impact of temperature variability on zebra finch cognition, focusing on song learning and song quality (N = 76 males). We used a 2 × 2 factorial experiment with two temperature conditions (stable and variable). Half of the juveniles were cross-fostered at hatching to create a mismatch between pre- and posthatching conditions, the latter matching this species' critical period for song learning. We found that temperature variability did not affect repertoire size, syllable consistency, or the proportion of syllables copied from a tutor. However, birds that experienced variable temperatures in their posthatching environment were more likely to sing during recordings. In addition, birds that experienced variable prenatal conditions had higher learning accuracy than birds in stable prenatal environments. These findings are the first documented evidence that variable ambient temperatures can influence song learning in zebra finches. Moreover, they indicate that temperature variability can act as a form of environmental enrichment with net positive effects on cognition.

State of charge estimation of ternary lithium-ion batteries at variable ambient temperatures

Among the factors that affect lithium-ion batteries, ambient temperature has a great influence on the charge and discharge rate, general battery performance, and storage capacity of the battery, hence accurate state of charge (SOC) estimation over a wide range of temperatures is essential and necessary. In this paper, a Second-order Thevenin equivalent circuit model is established with ambient temperature compensation over varying ambient temperature conditions. An improved Fixed Range Forgetting Factor-Adaptive Extended Kalman Filtering (FRFF-AEKF) algorithm with the Saga-Husa Adaptive filter (SHAF) is proposed for the accurate estimation of SOC at variable ambient temperature. The temperatures −10°C, 10 °C, 25 °C, and 40 °C are set to depict low, normal, and high ambient temperatures in which lithium-ion batteries in electric vehicles (EVs) and most electronic devices usually operate. Tests conducted include the hybrid pulse power characterization (HPPC) for obtaining data required for parameterization, and for SOC estimation and verification, the Beijing Bus Dynamic stress (BBDST). The object of the tests was a ternary lithium-ion battery representing those used in electric vehicles (EVs). To improve adaptability, reduced noise, and achieve faster convergence with increased accuracy, the range of forgetting factor is fixed between a variable range of 0.997–1. To verify the performance of the proposed algorithm under varying conditions and different ambient temperatures, the SOC estimation result was compared with that of the adaptive extended Kalman filtering (AEKF) algorithm. The results show that the proposed improved algorithm implemented with the established Second-order Thevenin equivalent model has a 1.1 % better estimation accuracy compared to the results of the AEKF algorithm. This confirms that the proposed method can achieve accurate SOC estimation and is adaptive to variable ambient temperatures.

Investigation and Analysis of Thermoelectrically Cooled CZT Performance

Cadmium zinc telluride (CZT) spectrometers have been considered for objectives and missions with variable ambient temperatures. Spectrometer-grade crystals of various sizes have been studied under conditions as low as −40°C for 2 × 2 × 2 and 5 × 5 × 2-mm3 crystals, and −10°C for 5 × 5 × 5-mm3 crystals for resolution improvement spanning 5.9-, 59.5-, and 122-keV photo peak energies. It is unclear from previously published data if cooling the spectrometer-grade crystals beyond −10°C results in increased resolution improvement or if the effect occurs with higher-energy photo peaks and trends among multiple crystals from the same manufacturer. Therefore, we acquired two CZT crystals from Kromek and cooled them in an insulated box to −25°C. Our measurements were performed every 5°C, and tested with 241Am or 241Am/152Eu mixed sources. The 241Am peaks were compared for both crystals, and the higher-energy resolution changes were explored using the mixed source. Overall, at 59.5 keV, both crystals yielded 3% to 4% resolution improvement for the cooling cycle and 6% improvement during the warming cycle. Resolution performance varied between the two tested crystals, and each had a different temperature where we observed optimum resolution. The 121.8-keV peak resolution improved by 1.2% for the cooling cycle and 3.6% for the warming cycle. There were no discernable resolution increases or changes for the two higher-energy peaks, 224.7 and 334.3 keV, respectively. Slight cooling of the CZT crystals can increase resolution performance by 4% in the lower-energy region.

Waste Heat Driven Multi-Ejector Cooling Systems: Optimization of Design at Partial Load; Seasonal Performance and Cost Evaluation

In this paper, a seasonal performance analysis of a hybrid ejector cooling system is carried-out, by considering a multi-ejector pack as expansion device. A 20 kW ejector-based chiller was sized to obtain the optimal tradeoff between performance and investment costs. The seasonal performance of the proposed solution was then evaluated through a dynamic simulation able to obtain the performance of the designed chiller with variable ambient temperatures for three different reference climates. The optimized multi-ejector system required three or four ejectors for any reference climate and was able to enhance the system performance at partial load, with a significant increase (up to 107%) of the seasonal energy efficiency ratio. The proposed system was then compared to conventional cooling technologies supplied by electric energy (electrical chillers EHP) or low-grade heat sources (absorption chillers AHP) by considering the total costs for a lifetime of 20 years and electric energy-specific costs for domestic applications from 0.10 to 0.50 €/kWhel. The optimized multi-ejector cooling system presented a significant convenience with respect to both conventional technologies. For warmer climates and with high electricity costs, the minimum lifetime for the multi-ejector system to achieve the economic break-even point could be as low as 1.9 years.

Thermodynamic Performance of Adsorption Working Pairs for Low-Temperature Waste Heat Upgrading in Industrial Applications

The present work aims at the thermodynamic analysis of different working pairs in adsorption heat transformers (AdHT) for low-temperature waste heat upgrade in industrial processes. Two different AdHT configurations have been simulated, namely with and without heat recovery between the adsorbent beds. Ten working pairs, employing different adsorbent materials and four different refrigerants, have been compared at varying working boundary conditions. The effects of heat recovery and the presence of a temperature gradient for heat transfer between sinks/sources and the AdHT components have been analyzed. The achieved results demonstrate the possibility of increasing the overall performance when internal heat recovery is implemented. They also highlight the relevant role played by the existing temperature gradient between heat transfer fluids and components, that strongly affect the real operating cycle of the AdHT and thus its expected performance. Both extremely low, i.e., 40–50 °C, and low (i.e., 80 °C) waste heat source temperatures were investigated at variable ambient temperatures, evaluating the achievable COP and specific energy. The main results demonstrate that optimal performance can be achieved when 40–50 K of temperature difference between waste heat source and ambient temperature are guaranteed. Furthermore, composite sorbents demonstrated to be the most promising adsorbent materials for this application, given their high sorption capacity compared to pure adsorbents, which is reflected in much higher achievable specific energy.

Tackling the Tibetan Plateau in a down suit: insights into thermoregulation by bar-headed geese during migration.

Birds migrating through extreme environments can experience a range of challenges while meeting the demands of flight, including highly variable ambient temperatures, humidity and oxygen levels. However, there has been limited research into avian thermoregulation during migration in extreme environments. This study aimed to investigate the effect of flight performance and high altitude on body temperature (Tb) of free-flying bar-headed geese (Anser indicus), a species that completes a high-altitude trans-Himalayan migration through very cold, hypoxic environments. We measured abdominal Tb, along with altitude (via changes in barometric pressure), heart rate and body acceleration of bar-headed geese during their migration across the Tibetan Plateau. Bar-headed geese vary the circadian rhythm of Tb in response to migration, with peak daily Tb during daytime hours outside of migration but early in the morning or overnight during migration, reflecting changes in body acceleration. However, during flight, changes in Tb were not consistent with changes in flight performance (as measured by heart rate or rate of ascent) or altitude. Overall, our results suggest that bar-headed geese are able to thermoregulate during high-altitude migration, maintaining Tb within a relatively narrow range despite appreciable variation in flight intensity and environmental conditions.

Study on dynamic thermal control performance of positive temperature coefficient (PTC) material based on a novel heat transfer model considering internal heat transfer

Positive temperature coefficient (PTC) material is widely used in thermal control due to its unique characteristics. In this paper, a novel heat transfer model of PTC material is proposed with consideration given to the internal heat transfer characteristics of the model which was ignored in the previous model, and it is validated by conducting experiment. Based on this novel heat transfer model, the effects exerted by thermal conductivity, heat capacity and thermal contact resistance on the thermal control of PTC material that have never been studied in previous work are investigated. In this paper, the PTC material with large heat capacity will extend the equilibrium time of the controlled device significantly. Besides, the dynamic thermal control performance of PTC material is verified by carrying out simulation. Herein, thermal control of PTC material under three different ambient temperature conditions is studied. As indicated by the results, PTC material has better thermal control performance under variable ambient temperatures. When the ambient temperature varies periodically with 5 °C amplitude and for a period of more than 300 s, the temperature of controlled device barely changes.

Stabilization of gas turbine unit power

We propose a new cycle air preparation unit which helps increasing energy power of gas turbine units (GTU) operating as a part of combined cycle gas turbine (CCGT) units of thermal power stations and energy and water supply systems of industrial enterprises as well as reducing power loss of gas turbine engines of process blowers resulting from variable ambient air temperatures. Installation of GTU power stabilizer at CCGT unit with electric and thermal power of 192 and 163 MW, respectively, has resulted in reduction of produced electrical energy production costs by 2.4% and thermal energy production costs by 1.6% while capital expenditures after installation of this equipment increased insignificantly.

DETERMINATION OF TEMPERATURE STRESSES AND STRAINS IN METAL SPANS BRIDGES

Purpose. For metal bridges topical study of the stress-strain state arising from the effects of variable temperature extremes of the environment, since the last five years rihayutsya observed significant increases ambient temperatures in summer and decrease in winter. Methodology. Using data from experimental measurements of temperaturedistribution on the surface of the beam-honovyh buildings of metal bridges using an analytical model was calculated thermal stresses and deformations tion arising from a given temperature distribution. Findings. Based on the calculated data revealed that statistically undetectable beams having tension level which reaches 30% of the allowable stress. Originality. For the first time were measured distribut temperature on the surface of metal girders bridges and developed a method for determining the temperature , stresses and deformations of the action variable ambient temperatures. Practical value. The analytical method of determining the thermal stresses and strains may be used byengineers of bridges testing station Railways of Ukraine to install and «Ukravtodor» thermo-stressed state beam spans metal bridges.

RETRACTED: A Simplified Thermal Modelling of Cooling Tower for Optimization of HVAC Systems to Enhance Energy Efficiency

This paper presents a simplified model to analyze the heat flow in Closed Wet Cooling Tower (CWCT). Based on the existing research results and some suitable assumed conditions, we develop a model to simplify the handling of the heat rejection rates under four different input parameters and variable ambient wet-bulb temperatures. The analytical results of the data from different sources demonstrate that the model with the new parameters is accurate enough for the control and optimization of CWCT operation. After validating the accuracy of the model, we also describe the extension of the model for analyzing the energy flows of a CWCT. When the model in combina- tion with the input power model, it may represent the quantitative relationship between energy flow rates and principal input-output variables of the CWCT.

Simulation of Solar Dryer Performances with Forced Convection Experimentally Proved

Abstract The aim of our study is to determine the drying curve and the change rate of drying by solar energy on two plant materials, olive pomace, and colocynth, depending on solar radiation. The dynamics of drying is monitored using an indirect solar dryer operating in forced convection, located at the UDES west of Algiers. We determine the influence of some parameters on the drying kinetics. We used two plant materials according to well-defined quantities which are characterized by different initial moisture content(Mafart P., 1991) .In order to verify the reliabilityof the dryer to dry different products with different humidity, we studied the variation of the solar radiation, drying rate and variable ambient temperatures at the end of work we simulate using a software results in the change of obtaining plans designating the experimental curves obtained after the change of several parameters such as air temperature along the path in the dryer, as well as mass loss and speeds drying products subjected to drying.

High fatty acid oxidation capacity and phosphorylation control despite elevated leak and reduced respiratory capacity in northern elephant seal muscle mitochondria.

Northern elephant seals (Mirounga angustirostris) are extreme, hypoxia-adapted endotherms that rely largely on aerobic metabolism during extended breath-hold dives in near-freezing water temperatures. While many aspects of their physiology have been characterized to account for these remarkable feats, the contribution of adaptations in the aerobic powerhouses of muscle cells, the mitochondria, are unknown. In the present study, the ontogeny and comparative physiology of elephant seal muscle mitochondrial respiratory function was investigated under a variety of substrate conditions and respiratory states. Intact mitochondrial networks were studied by high-resolution respirometry in saponin-permeabilized fiber bundles obtained from primary swimming muscles of pup, juvenile and adult seals, and compared with fibers from adult human vastus lateralis. Results indicate that seal muscle maintains a high capacity for fatty acid oxidation despite a progressive decrease in total respiratory capacity as animals mature from pups to adults. This is explained by a progressive increase in phosphorylation control and fatty acid utilization over pyruvate in adult seals compared with humans and seal pups. Interestingly, despite higher indices of oxidative phosphorylation efficiency, juvenile and adult seals also exhibit a ~50% greater capacity for respiratory 'leak' compared with humans and seal pups. The ontogeny of this phenotype suggests it is an adaptation of muscle to the prolonged breath-hold exercise and highly variable ambient temperatures experienced by mature elephant seals. These studies highlight the remarkable plasticity of mammalian mitochondria to meet the demands for both efficient ATP production and endothermy in a cold, oxygen-limited environment.

Assessing the Efficiency of Palm-Based Insulators for Storage Water Tanks Under Variable Ambient Temperatures

Laboratory and field experiments were carried out, to assess the efficiency of palm-based insulators for storage water tanks under variable ambient temperatures. Palm fronds, palm leaves and their composite were used to wrap pilot water tanks and examine their thermal insulation efficiency. Four arrangements were tested including: double layer of fronds and an inner air gap, double layer of fronds separated by an intermediate air gap, palm leaves and composite of palm leaves sandwiched between two layers of fronds. The insulation efficiency was assessed in laboratory setting under heating-up and cooling-down conditions using the time constant, \({\tau}\) , and compared to a reference unwrapped tank. The insulators were also tested in the field under variable ambient air temperatures. In this case, their efficiencies were assessed considering the relative amplitude ratio of the stored water and ambient air temperatures, in addition to the phase shift between the times of temperature extremes of air and water in the different tanks. The results indicate that the fronds–leaves composite provides better insulation efficiency under heating-up, cooling-down and variable ambient air temperatures.

Heat transfer in phase change materials for thermal management of electric vehicle battery modules

The temperature of battery modules in electric vehicles (EVs) must be controlled adequately to remain within a specified range for optimum performance. In this paper, thermal management of battery modules with phase change materials (PCMs) is investigated experimentally. An electric heater is used to simulate the heat source of a battery cell. Two different PCM designs are investigated: one with a PCM cylinder surrounding the heater, and the other with PCM jackets wrapping the heater. Both configurations exhibit good effectiveness in maintaining the heater within a desired temperature range. This paper also examines the effectiveness of PCM thermal management under variable heating rates and variable ambient temperatures, as well as the effects of buoyancy during PCM melting.