Constant Ambient Temperature Research Articles

An Arrhenius-Based Simulation Tool for Predicting Aging of Lithium Manganese Dioxide Primary Batteries in Implantable Medical Devices

This article presents a novel aging-coupled predictive thermo-electrical dynamic modeling tool tailored for primary lithium manganese dioxide (Li-MnO2) batteries in active implantable medical devices (AIMDs). The aging mechanisms of rechargeable lithium batteries are well documented using computationally intensive physics-based models, unsuitable for real-time onboard monitoring in AIMDs due to their high demands. There is a critical need for efficient, less demanding modeling tools for accurate battery health monitoring and end-of-life prediction as well as battery safety assessment in these devices. The presented model in this article simulates the battery terminal voltage, remaining capacity, temperature, and aging during active discharge, making it suitable for real-time health monitoring and end-of-life prediction. We incorporate a first-order dynamic for internal resistance growth, influenced by time, temperature, discharge depth, and load current. By adopting Arrhenius-type kinetics and polynomial relationships, this model effectively simulates the combined impact of these variables on battery aging under diverse operational conditions. The simulation handles both the continuous micro-ampere-level demands necessary for device housekeeping and periodic high-rate pulses needed for therapeutic functions, at a constant ambient temperature of 37 °C, mimicking human body conditions. Our findings reveal a gradual, nonlinear increase in internal resistance as the battery ages, rising by an order of magnitude over a period of 5 years. Sensitivity analysis shows that as the battery ages and load current increases, the terminal voltage becomes increasingly sensitive to internal resistance. Specifically, at defibrillation events, the ∂V∂R trajectory dramatically increases from 10−12 to 10−8, indicating a fourth-order-of-magnitude enhancement in sensitivity. A model verification against experimental data shows an R2 value of 0.9506, indicating a high level of accuracy in predicting the Li-MnO2 cell terminal voltage. This modeling tool offers a comprehensive framework for effectively monitoring and optimizing battery life in AIMDs, therefore enhancing patient safety.

Long-term viscoelastic behavior and evolution of the Schapery model for mirror epoxy

Abstract Mirror epoxy, used in its pure form with a resin-to-hardener ratio of 100:50, is emerging as an innovative material widely used in modern flooring. Its appeal lies in its smooth, shiny surface, offering a unique and contemporary aesthetic. However, understanding its long-term viscoelastic behavior is essential to ensure the durability and performance of floor coverings under various conditions of use. This study examines the evolution of the Schapery model for mirror epoxy, focusing on its long-term viscoelastic behavior. Creep tests at constant loads and ambient temperature are carried out in order to numerically determine the static nonlinearity factors g and g 0 formulated in the Schapery model. To validate this model, other relaxation tests at constant deformations are carried out under the same conditions, which allowed us to determine the nonlinearity factors h and h 0 formulated in this model using the same method. A remarkable consistency between the variations in the experimental and numerical values of the model programmed on MATLAB allows us to conclude that the Schapery model describes the real behavior of the mirror epoxy in a satisfactory manner.

Effects of relative humidity on physiology and behavior of laying hens exposed to high ambient temperatures.

This study investigated how different relative humidity (RH) would impact behavior and physiology of laying hens. One hundred-eighty laying hens (Hy-Line Brown), aged 68-week-old (1,908 ± 78g), were exposed to daily ambient temperatures of 30°C with RH set at 25% (RH25), 50% (RH50), or 75% (RH75) for 12h a day (9:00 am to 9:00 pm) from 70 to 74 weeks of age. All hens had been raised at 24°C and 50% RH during 2-week adaptation period. Each RH treatment consisted of 10 replicates with 6 hens each in a completely randomized design. Results indicated that rectal temperature, respiratory rate, and heart rate were increased (P ≤ 0.05) in the RH75 group compared with the RH25 and RH50 groups. Plasma malondialdehyde concentrations were elevated in the RH75 group compared RH50 at 3, 7, and 21 days (P ≤ 0.05) following the RH exposure. Plasma glutathione peroxidase activity was lowered (P ≤ 0.05) in the RH75 group compared with the RH25 and RH50 groups at 21 days. Increasing RH led to decreased feeding behavior but showed a tendency to increase drinking behavior. Wings elevated and panting behaviors were higher in the RH75 group compared with the RH25 and RH50 groups (P ≤ 0.05). In conclusion, these findings suggest that elevated RH at constant ambient temperature could negatively influence the behavior and physiology of laying hens.

Microbiome resilience of three-toed box turtles (Terrapene carolina triunguis) in response to rising temperatures.

The gastrointestinal (GI) microbiome of chelonians (testudines) plays an important role in their metabolism, nutrition, and overall health but the GI microbiome of three-toed box turtles (Terrapene carolina triunguis) has yet to be characterized. How the GI microbiome responds to rapidly rising environmental temperatures has also not been studied extensively in ectotherms, specifically chelonians. In this study, twenty (20) T.c.triunguis were split into control and experimental groups. The experimental group experienced 4.5°C increases every two weeks while the control group stayed at a constant ambient temperature (24°C) through the entirety of the experiment. Before each temperature increase, all turtles had cloacal swab samples taken. These samples underwent DNA extraction followed by 16S rRNA gene sequencing and microbial community analyses. Differences in diversity at the community level in the controls compared to the experimental groups were not statistically significant, indicating microbiome resilience to rapid temperature changes in T.c.triunguis, although some differentially abundant lineages were identified. Interestingly, an amplicon sequence variant belonging to the Erysipelothrix spp. was exclusively enriched in the highest temperature group relative to controls. Overall, our work suggests that there may be an innate robustness to rapid temperature swings in the microbiome of T.c.triunguis which are native to temperate North America. Despite this resilience, Erysipelothrix spp. was enriched at the highest temperature. Phylogenetic analysis of this amplicon variant showed that it is a close relative of Erysipelothrix rhusiopathiae, a pathogen of zoonotic importance associated with both wildlife and livestock.

Dexamethasone administration restored growth in dairy calves exposed to heat stress

Recent evidence indicates that the heat stress loss on the growth performance of calves is associated with the diversion of nutrients to control enteritis and systemic inflammation. In this study, we investigated the impact of heat stress on markers of inflammation, feed use-efficiency, and growth of dairy calves. We hypothesized that dexamethasone, which is known for its immunosuppressive and anti-inflammatory properties, would reduce inflammation and restore the growth of calves exposed to heat stress. Thirty-two Holstein bull calves (body weight (BW) 68.5 ± 1.37 kg; age 3.5 ± 0.5-week-old; mean ± SD) were housed in individual pens in climate-controlled rooms at constant ambient temperature and allowed to adjust to facilities for 5 d before the start of treatments. Calves were randomly assigned to one of 4 treatments (n = 8/treatment) in a 2 × 2 factorial arrangement of environment (ENV, thermoneutral or heat stress) and intervention (INT, saline or dexamethasone) imposed for 5 d as follow: 1) thermoneutral (constant ambient temperature of 20°C 24 h/d) and administration of saline, 2) thermoneutral (constant ambient temperature of 20°C 24 h/d) and administration of dexamethasone, 3) cyclic heat stress (40°C ambient temperature, from 0800 to 1900 h/d) and administration of saline, 4) cyclic heat stress (40°C ambient temperature, from 0800 to 1900 h/d) and administration of dexamethasone. Dexamethasone (0.05 mg/kg BW), or saline (1.2 mL) was administered intramuscularly on d 1 and 3. Upon completion of treatments, calves were euthanized on d 5 to obtain jejunum mucosa samples. Commercial milk replacer, starter grain, and water were offered, and intake was monitored daily. Rectal temperature and respiratory rate were monitored 3 times daily. Blood samples were collected on d 1, 3, and 5 to determine serum pro-inflammatory cytokine concentrations. A section of the jejunum was collected and snap-frozen to determine the concentration of pro-inflammatory markers. Statistical analyses included a mixed model, fixed effects of ENV, INT, consecutive measurements taken over time (d, h, or both), replica, and random effects of calf and error (SAS version 9.4, SAS Institute Inc., Cary, NC). The measurements collected immediately before treatment allocation were included as covariates in the model. An ENV effect showed that heat stress increased rectal temperature (38.72 vs. 39.21°C), respiratory rate (36 vs. 108 breaths/min), and water intake (3.2 vs. 6.6 L/d). The treatments did not affect dry matter intake. An ENV × INT interaction showed that heat stress with saline decreased average daily gain (ADG) by 35% and tended to decrease feed use-efficiency by 36%, but the use of dexamethasone to treat heat stress restored ADG and feed use-efficiency comparable to their basal levels. An ENV × INT interaction revealed that heat stress with saline increased jejunal interleukin (IL)-6 concentration 2-fold, but dexamethasone treatment of heat stress restored jejunal IL-6 concentration to basal levels. The bioenergetic cost of the heat stress-immune pro-inflammatory response ranged between 1.18 and 1.50 Mcal of ME. Overall, the administration of dexamethasone reduced the jejunal concentration of a pro-inflammatory marker and restored the heat stress-associated reduction in growth and feed use-efficiency. The immunomodulation and anti-inflammatory effects of dexamethasone could be part of a homeorhetic change that results in a shift from maintenance functions to support growth on calves exposed to heat stress.

Testing of NMC and LFP Li-ION cells for surface temperature at various conditions

Battery electric vehicles (BEVs) are being considered as a replacement technology for diesel vehicles in underground mining of mineral resources. However, many issues related to BEVs in industrial applications still require more detailed research. One significant topic is the heat load—BEVs' heat emission into the working environment during regular operation. This paper provides an overview of the thermal behavior of NMC and LFP Li-ion cells tested under various conditions, which is an important step in determining the overall heat load of BEVs. The surface temperature of three NMC and one LFP 18650 Li-ion cells was monitored during charging and discharging at four different rates, at constant ambient temperatures of 30 °C and 40 °C. The main results pertain to the cell's thermal behavior during charging and discharging, highlighting the distinctive temperature profiles of NMC and LFP cells.

Comparing Influence of Thermal Effects in Experimental Models - Thermotherapy in Medical Rehabilitation

Introduction: The subject of thermometry and impact of thermal effect on the human body is still a topic known and discussed in medical care. One of the basic methods in clinical diagnosis is the measurement of body temperature. In biological tissues, there are two main types of reactions caused by optical radiation: photochemical and thermal. The effects of radiation exposure depend on its properties and physical parameters, including the amount of absorbed dose and the duration of exposure. In the case of thermotherapy as a therapeutic method, the appropriate choice of radiation type and the selection of physical parameters is a necessary condition for obtaining desired, beneficial therapeutic effects. The aim of the study is to investigate the thermal effect of non-ionizing radiation: infrared (IR), ultraviolet (UV) and electromagnetic field (EMF) induced in short-wave diathermy (MD), measured with classical thermometers and a thermal imaging camera. The thermal effect, as a result of overheating with three different factors: IR, UV, MD; and under the same conditions, is studied. The variation in temperature distribution in different phantoms is evaluated in order to delve into the subject of thermal effect regarding each radiation separately and to consider its suitability for medical diagnosis and therapy.Material and methods: The thermal effect study was carried out on two phantoms. The first phantom F1 - a wooden cuboid (27.0 x 7.0 x 7.5cm) with five holes drilled at 5-cm intervals, into which thermometers were inserted (depth 5 cm). The second phantom - F2 was a biological tissue, the lower part of pork ham cut off along with the bone with fat covering and skin. Phantoms F1 and F2 were treated with an infrared heater (P1), a lamp emitting ultraviolet radiation (P2) and short-wave diathermy (P3); C and irradiation - 20 minutes, temperature measurements at intervals of 5 minutes, i.e. 5, 10, 15 and 20 minutes for the examined factors. During the experiment, temperature measurements were periodically made with the IR Thermal Radiometric Camera MobIR M3. For obtaining reliability of the measurements, the whole trial was repeated 10 times. Before the thermograms were made, two-hour intervals were applied between successive measurements, maintaining a constant ambient temperature of 23C.Results: With regard to UV radiation, there was an increase in the average temperature among the thermometers. This was particularly noticeable in the first thermometer with a 1.9% increase (up to 25.110.29C) above the ambient temperature (24.650.34C) after 15 minutes of measurements. After 20 minutes, the average temperature increase in thermometer 1 was 2.2% (up to 25.180.23C). A temperature increase in subsequent thermometers may be related to thermal conductivity and an increase of ambient temperature. In turn, for IR, an average 1.7% (to 25.160.87C) temperature increase of all thermometers was observed at 15 minutes and at 20 minutes, by 2.9% (to 25.481.35C) compared to baseline temperature (24.750.47\C). Comparing the average temperature of thermometer 1 with the ambient temperature (24.750.49C), the highest increase of 12.8% (to 27.930.69C) was noted after 20 minutes of measurements. In diathermy, after 10 minutes, an increase in the average temperature in thermometer 1 was observed by 2.8% (to 25.690.46C) above the ambient temperature. The highest increase in average temperature was recorded in thermometers 1 and 5 in the 20thminute of measurements.Conclusions: All of the applied methods caused temperature increases in the used phantoms. The temperature distribution in the wooden phantom corresponds to that in the biological tissue for the interaction of infrared radiation (IR) and short-wave diathermy (MD), which was confirmed by thermovision. The increase in the internal temperature of the superheated biological structure corresponds to the increase in the distribution of the phantom’s internal temperature.

Dynamic responses of systemic immunity and splenic inflammation to long-term cyclic high-temperature exposure in growing pullets and laying hens

Two trials were conducted to draw the phase-response curve of productive and immunological variables in heat-exposed layer chickens at different ages (71 to 130 d, and 211 to 270 d). Birds were acclimated to the following conditions for 60 d: constant optimal ambient temperature at 24°C and high ambient temperature at 34°C for 8 h/d (10:00-18:00). Data collection and biochemical measurements were performed every 10 d. In both age ranges, high temperature favored the innate immunity (P < 0.01) at the cost of performance (P < 0.05) during a given period, including the relative abundance of B and T-helper lymphocytes, lymphocyte proliferation ratio (B and T lymphocytes), and serum immunoglobulin contents (IgG and IgM) in the peripheral blood, as well as splenic expression of inflammation-related genes (iNOS, TLR-4, TNF-α, IL-6, and INF-γ). Compared with laying hens, growing pullets showed a time-delayed activation of immune response following heat challenge, and had no immunosuppression up to the end of exposure. Overall, the immune system of layer birds has a trade-off with production tissues in a hot environment, and exhibits distinct age-range-specific responses of acclimatization.

KINETICS OF DRYING OF DISPERSED MATERIAL IN THE APPARATUS OF PERIODIC ACTION WITH FLUIDIZED BED

A theoretical method for calculating a periodically operating fluidized bed dryer is presented based on the zonal method for describing kinetics and an example of calculation is given in relation to the drying of pea grain. In the calculation, it is assumed that the solid phase in the apparatus is completely mixed, and the gas is ideally displaced, the particles have a spherical shape and are the same in size. Accounting for changes in the parameters of the drying agent in the layer is carried out on the basis of the equations of material and thermal balance for the layer with the division of the entire range of changes in the moisture content of the material into a number of concentration zones. The change in the temperature of the dried particles during the process is calculated based on the analytical solution of the linear heat conduction problem at a constant ambient temperature and the condition that moisture evaporation occurs at the surface of the particles (there is no internal evaporation). The calculation is carried out using the method of successive approximations. First, the duration of drying of the material in the concentration zone under consideration is set, then the average air parameters are determined by the height of the layer and by the drying time, and, using these data, by solving the problem of mass conductivity (moisture diffusion), the drying duration in the zone under consideration is determined and compared with the preset one. If there is a significant discrepancy, a second calculation iteration is carried out, taking the drying time found in the first calculation iteration. Calculations are carried out until an acceptable match between the previously accepted and calculated drying time. Then they move on to the second concentration zone, for which they do the same. The total drying time is equal to the sum of the times in the concentration zones. This technique was tested using the example of calculating the drying of pea grains. In the calculations, we used data previously found by the authors on the coefficient of mass conductivity (moisture diffusion), as well as literary reference data on the coefficients of thermal conductivity, thermal diffusivity and heat capacity of this material. Heat and mass transfer coefficients were calculated using criterion equations given in the literature. To select the operating air speed, the speed of the beginning of fluidization was calculated; the operating air speed was taken at a fluidization number of 1.05. The calculation of the Biothermal and mass transfer criteria showed that the thermal problem is mixed (the Biothermal number is 5.81), i.e. the heat transfer process is influenced by both internal and external heat transfer. The problem of mass transfer is purely internal (the modified mass transfer Bio number is 122.5), which was taken into account when calculating the drying time. The calculated drying curve was compared with the experimental one. A diagram of the experimental setup is given and a description of the experiment is given. Satisfactory agreement between the calculated and experimental drying curves indicates the correctness of the calculation method under consideration, which can be recommended for engineering use. For citation: Rudobashta S.P., Zueva G.A., Babicheva E.L. Kinetics of drying of dispersed material in the apparatus of periodic action with fluidized bed. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 6. P. 109-118. DOI: 10.6060/ivkkt.20246706.6968.

A rapid return to normal: temporal gene expression patterns following cold exposure in the bumble bee Bombus impatiens.

Bumble bees are common in cooler climates and many species likely experience periodic exposure to very cold temperatures, but little is known about the temporal dynamics of cold response mechanisms following chill exposure, especially how persistent effects of cold exposure may facilitate tolerance of future events. To investigate molecular processes involved in the temporal response by bumble bees to acute cold exposure, we compared mRNA transcript abundance in Bombus impatiens workers exposed to 0°C for 75 min (inducing chill coma) and control bees maintained at a constant ambient temperature (28°C). We sequenced the 3' end of mRNA transcripts (TagSeq) to quantify gene expression in thoracic tissue of bees at several time points (0, 10, 30, 120 and 720 min) following cold exposure. Significant differences from control bees were only detectable within 30 min after the treatment, with most occurring at the 10min recovery time point. Genes associated with gluconeogenesis and glycolysis were most notably upregulated, while genes related to lipid and purine metabolism were downregulated. The observed patterns of expression indicate a rapid recovery after chill coma, suggesting an acute differential transcriptional response during recovery from chill coma and return to baseline expression levels within an hour, with no long-term gene expression markers of this cold exposure. Our work highlights the functions and pathways important for acute cold recovery, provides an estimated time frame for recovery from cold exposure in bumble bees, and suggests that cold hardening may be less important for these heterothermic insects.

ANFIS-based improved GWO: Rapid prototyping of low-power solar energy system under fast-changing solar radiation conditions

The increasing need for energy, coupled with progress in technology, has emphasized the importance of renewable energy sources around the world. Solar energy systems harness the power of sunlight to generate electricity, offering a renewable and environmentally friendly alternative to conventional energy sources. Maximum Power Point Tracking (MPPT) algorithms are employed to achieve optimal efficiency from the PV systems. This paper introduces a new method for controlling Maximum Power Point (MPP) in battery charging systems using an Adaptive Neuro-Fuzzy Inference System (ANFIS)-based improved Grey Wolf Optimization (ANFIS-GWO) algorithm. The study involves the application and evaluation of the IGWO algorithm under fast-changing solar radiation conditions (1000 w/m2, 600 w/m2, 800 w/m2) and constant ambient temperature (25 °C). An analysis was performed to evaluate the behavior of the system in the laboratory environment using rapid prototyping. The proposed IGWO algorithm demonstrates improved accuracy compared to traditional methods in the current literature. The study aims to enhance the efficiency of MPPT control in photovoltaic (PV) systems, offering a potential solution for optimizing performance in different solar radiation conditions.

Effects of temperature on reproduction and development of Cyanopterus ninghais (Hymenoptera: Braconidae), a larval parasitoid of Monochamus alternatus (Coleoptera: Cerambycidae)

AbstractCyanopterus ninghais (Hymenoptera: Braconidae), a newly discovered gregarious ectoparasitoid, is a promising biological control agent against the third‐fifth instar larvae of the Japanese pine sawyer, Monochamus alternatus (Coleoptera: Cerambycidae). Effects of constant ambient temperatures (17, 20, 23, 26, 29 and 32°C) on the reproduction and development of the parasitoid were determined in the laboratory. Results showed that the pre‐oviposition periods of C. ninghais decreased gradually with increasing temperatures, ranging from 8.5 d (at 17°C) to 3.4 d (at 32°C). Both the parasitism rates and the number of offspring exhibited a parabolic trend in relation to increasing temperatures, with the highest parasitism rate being 80% (at 29°C) and the maximum number of offspring reaching 7.2 (at 26°C). Temperature did not significantly affect the emergence rate and sex ratio of progeny. The duration of each developmental stage was inversely correlated with temperature within the range of 20 to 32°C. The egg‐to‐adult development time was 32.3 d at 20°C and 12.5 d at 32°C. The developmental threshold temperatures for the egg, larva, pupa, and the entire generation were 8.6, 12.6, 12.8 and 12.1°C, respectively, and the effective accumulated temperatures were 34.3, 51.3, 148.9 and 240.0 Degree‐days, respectively. We concluded that temperatures in the range of 26 to 29°C are the most suitable for the development and reproduction of C. ninghais. These findings provide important information for improving the artificial rearing efficiency and field release of this parasitoid under different temperature conditions.

Solder fatigue life modeling of QFN components based on design of experiments

Shorter development times and increasing cost-efficiency make it necessary to predict the reliability of electronic assemblies at an early stage. Within this framework, this work focuses on the influence of load and geometric parameters on the solder fatigue life of Quad Flat No Leads (QFN) components.Following a Design of Experiments (DoE) test plan, the following design parameters affecting the solder fatigue life are investigated: the number of leads and the pitch, the orientation of the component on the Printed Circuit Board (PCB), the constant ambient temperature and the surface strain. A test setup is used in which each parameter can be varied individually.From the resulting lifetimes, a multiple regression model and a physical-based model are derived. The regression model shows a slightly better fit quality due to its higher degree of freedom and is not subject to any physical constraints. The physical-based model is a combination of different proven solder fatigue life models and avoids any overfits which can occur in a regression model. Based on these models, the influence of the parameters on the solder fatigue life and the relationship between the parameters and the solder fatigue life is evaluated.With these results, it is possible to predict the lifetime with respect to mechanical load cases depending on size, orientation and surface strain as well as thermal load. This opens up completely new possibilities in PCB design by significantly improving the quality of solder fatigue life prediction and significantly reducing the restricted areas for component placement.

An experimental study on the measurement of gas diffusivities in un-saturated clay based materials

Gas migration in porous media in the context of nuclear waste disposal is dominated by diffusion. The availability of abundant data on diffusion coefficients of different gases in many clay based materials such as Boom Clay, Opalinus Clay and Callovo-Oxfordian Clays provides a good overview of the rates of gas transport through these different clay rocks [1]. Such formations are being considered as potential host rocks for the disposal of high and intermediate level radioactive wastes across Europe. Diffusion coefficients have been studied with particular interest due to the unavoidable gas generation phase in the nuclear waste repository [2]. However, all the diffusion measurements performed so far have been under fully saturated conditions, with little experimental data on gas diffusivities in partially saturated conditions, which have been hypothesized to exist during the early part of the life cycle of the repository [3]. The objective of the current study is to provide an overview of the effect of desaturation on the rate of diffusive transport of gases in partially saturated clay based materials.&#x0D; The experimental methodology is based on the double through diffusion setup used in previous studies to measure gas diffusivities in saturated clays [1]. However, the setup is modified so as to keep a fixed level of unsaturation in the clay sample. This is done by employing the vapour equilibrium technique, using oversaturated salt solutions in both upstream and downstream reservoirs to maintain a constant relative humidity in the entire setup [4].&#x0D; Preliminary pore network modelling has already shown that the gas diffusivity increases with a decrease in water saturation of the clay material. However, the predicted trend also suggests that this increase is only marginal and should not normally exceed an order of magnitude. This is shown in the figure below.&#x0D; All the diffusion measurements are carried out on synthetic clay samples of dimensions 3.8 cm (diameter) and 2 cm (height). In Table 1, the Sw stands for water saturation. The compositions of the synthetic clay samples (60% clay, 20% sand, 20% silt) have been adjusted so as to most closely mimic the mineralogical compostion of Boom Clay. Synthetic samples are used instead of natural samples like Boom Clay because of their better physical response to drying than Boom Clay.&#x0D; The selected control variable to lower the saturation of the material is suction, which is imposed by changing the relative humidity of the environment using oversaturated salt solutions [4]. Suction can be kept constant given constant ambient temperature and pressure. Thus, the clay sample is conditioned at a certain suction, which in turn leads to desaturation in the range of 70-100% of total saturation depending on the level of suction. For this study, the saturation range has been fixed in between 70-100% of total saturation. This range has been chosen because of what is expected in a real life nuclear waste repository. The first measured diffusion coefficients in two partially saturated samples are shown in Table 1. The initial measurements of gas diffusion coefficients in unsaturated synthetic clays show that the increase in diffusivity of helium is higher than that of argon. Helium is the second lightest known element and has an extremely small molecular size and hence the impact of desaturation on helium diffusivity could be more pronounced than the same for heavier gases.

Application of a fiber Bragg grating temperature sensing method based on support vector regression optimized by a genetic algorithm for the decreasing external ambient temperature case.

We studied the application of the fiber Bragg grating (FBG) temperature sensing method based on support vector regression optimized by a genetic algorithm (GA-SVR) for constant and decreasing external ambient temperature cases by simulation. The external ambient temperature could be retrieved from both the transient FBG wavelength and its corresponding change rate using GA-SVR, before the FBG temperature sensor reached the thermal equilibrium state with the external ambient temperature. FBG wavelengths and their corresponding change rates in the cases of FBG sensor temperatures higher and lower than the external ambient temperature were studied and used to construct the training data set. We found that there exist singularity points in the curves of the wavelength change rate when the FBG sensor temperature is higher than the external ambient temperature in some cases, which is different from the case where the FBG sensor temperature is lower than the external ambient temperature. Its application for sensing the constant and decreasing external ambient temperature in real time was demonstrated with an accuracy of 0.32°C in those two cases. It also indicates that for real applications of this temperature sensing method where the external ambient temperature varies randomly, the FBG sensor temperature changes rather than the external ambient temperature changes play the dominant role. What is more, the demodulation time was decreased to 0.002s, which is approximately 0.05‱ of the time constant of the FBG temperature sensor. In other words, this method makes it possible to realize the external ambient temperature determination using a time smaller than the time constant of the FBG sensor. The high sensing accuracy and fast demodulation speed are crucial for future high-performance real-time FBG temperature sensing.

Thermal performance of a metal hydride reactor for hydrogen storage with cooling/heating by natural convection

Metal hydride (MH) systems can be used for storage in stationary facilities of hydrogen with a high volume density at temperatures and pressures close to ambient ones. Recently, the possibility of using passive heating/cooling systems or regenerative heat exchangers has been studied to improve the energy efficiency of MH systems for hydrogen storage without the need for forced circulation of a heating/cooling fluid. Natural convection of air may be used to passively remove/add heat as required for proper operation of a MH reactor. Under these conditions, the MH reactor can operate at a constant ambient air temperature and be driven by a difference in pressure between the source and the consumer of hydrogen. Since operation of MH systems with natural convective heating/cooling has not been systematically investigated as yet, a tubular MH reactor based on this principle is examined in this paper. Two-thirds of the internal volume of ø25.4 × 1 mm tube is occupied by a composition of LaNi5 and aluminium foam (one linear metre contains 1.1 kg of LaNi5 with a hydrogen capacity of 153 NL H2). Annular fins are used to increase heat transfer to air. Detailed and simplified mathematical models of the systems of this class are proposed and validated. It is shown that acceptable hydrogen charging/discharging rates in such systems are achieved with proper selection of fining characteristics. Charging from a hydrogen source at a pressure of 10 atm and an ambient air temperature of 10 to 30 °C takes 15 min. A reactor with a length of 1 m can desorb almost all stored hydrogen at a minimum outlet pressure of 0.45 bar to feed 30–300 W fuel cells.

Sustainable Greenhouse Covering Materials with Nano- and Micro-Particle Additives for Enhanced Radiometric and Thermal Properties and Performance

This review aims to provide a comprehensive overview of nano- and microscopic materials that can provide thermal radiation insulation without reducing visible light transmittance, thereby reducing heat loss and conserving energy in greenhouses. We also reviewed the radial and thermal properties of greenhouse covering materials. Fillers, colorants, reinforcers, and additives, as well as glass, plastic film, and plastic sheet materials, were discussed. Additionally, by searching for keywords like insulation film, insulation agent, and infrared insulation, compounds based on graphene and fullerene as well as phase transition materials (PCMs) that may be used for radiation insulation, we proposed their potential use in greenhouse covers. They can be divided into semi-transparent photovoltaic (PV) materials, zinc oxide-based film fillers, and silica filter films. We discussed the radiation heat insulation and light transmission characteristics of these materials. Nano-synthesis techniques were also investigated. Based on latest advances in the literature, future developments in the micro- and macroscale synthesis of nanomaterials will enable additional innovations in covering materials for greenhouse structures. A limiting factor, though, was the high sensitivity of PVs to external climatic and meteorological variables. The ability of materials used to make greenhouse covers to control the microclimate, reduce CO2 emissions, use less energy, and increase agricultural productivity, however, cannot be disputed. Similar to this, a thorough examination of the uses of various greenhouse technologies reveals that the advancements also have financial advantages, particularly in terms of reducing greenhouse heating and cooling expenses. The PCMs, which decreased greenhouse-operating costs by maintaining constant ambient temperatures, provide ample evidence of this.

Numerical Simulation of Ventilation in a Confined Space

Numerical simulation of ventilation in a confined space is conducted with different quantities of heat sources and various conditions of the room with a constant ambient temperature of 298K. The velocity streamline plot shows a different air recirculating pattern in the case with the air ventilation system switched off. The room with an extreme condition achieves the highest temperature of T=310K. The lowest temperature is obtained in the case with a relaxing condition where T=Tac=294K. The efficiency of systems reduces when the air conditioner and air ventilation system operate at the same time. The efficiency of the air conditioner increases, and the ambient temperature achieves minimum value when the air ventilation system remains off. The position of the air conditioner is closed to the air ventilation system causing the efficiency of the system to reduce. This is due to the air ventilation system drawing cold air out of the room before convective heat transfer occurs.

Effects of Different Phase Change Material Arrangement on Thermal Management for Lithium-Ion Batteries

The high energy density, low self-discharge, and operating voltages of lithium-ion batteries make them the preferred choice for electric cars. It is crucial to keep the battery pack at operational temperatures in order to avoid thermal runaways because these high energies are being stored in a small area. In this research, a novel passive battery cooling method is presented that makes use of two different phase change materials (PCM) arranged in various ways inside a battery pack. In this study, RT50 and RT60 PCMs are utilized to evaluate the combined thermal performance to that of a single PCM. A variety of configurations for the phase change material are used between battery pack cells, including trans-axial, trans-radial arrangements and compared against the performance of individual PCM. The effectiveness of passive cooling is evaluated in the current study for a variety of layouts that are exposed to external convection circumstances at a constant ambient temperature of 25°C. The transient behaviour of the battery cell temperature and its effects on PCM architecture at various melting stages are investigated in the current work. The heat transmission characteristics and melting phenomenon to suggested phase change materials arrangements is assessed.

Property Improvement of Recycled Coarse Aggregate by Accelerated Carbonation Treatment under Different Curing Conditions

Recycled aggregate (RA) made from waste concrete has inferior fundamental properties, i.e., apparent density, water absorption, mass variation, carbonation ratio, etc., compared to those of natural aggregate (NA), severely restricting its application in practical projects. However, using CO2 to accelerate RA carbonation can effectively improve these properties, and this treatment approach can promote energy savings and sustainable development. The accelerated carbonation curing conditions for RA can significantly impact the modification effect of RA. For this purpose, this paper used recycled coarse aggregate (RCA) as a case study. An accelerated carbonation modification treatment experiment for RCA under different accelerated carbonation curing conditions was carried out, and the effects of relative humidity and CO2 concentration on the apparent density, water absorption, moisture content, mass variation and carbonation ratio of RCA under a constant ambient temperature were explored and quantified. The results indicated that the best-accelerated carbonation curing conditions applicable to this paper’s RCA were confirmed as being an environmental temperature of 20 °C and a relative humidity of 70%, as well as a CO2 concentration of 20%. Under these conditions, the apparent density and water absorption of CRCA are approximately 1.04 times and 75.30% higher than those of RCA, and, in addition, the carbonation ratio for RCA under the optimal accelerated carbonation curing conditions is all higher than others, thus improving the properties of RCA to a certain degree. Finally, in this paper, the variation trends of the RCA property indexes in terms of carbonation time treated by the best accelerated carbonation curing conditions are examined, and the time-varying models for the RCA property indexes during the accelerated carbonation are established.