Rate Of Temperature Increase Research Articles

Flame spreading and burning of high- and low-flash point fuels under compressed air foam suppression

Firefighting foam has been widely used as an efficient and clean agent for extinguishing liquid fires. In this work, the flame spreading and burning of 0# diesel and n-heptane fuels were suppressed using pre discharged compressed air foam (half coverage of the pool). The foam can effectively prevent the liquid-phase-controlled flame spreading over diesel, but cannot prevent the gas-phase-controlled flame spreading of n-heptane. In the burning stage, for diesel, in the flame-foam interaction region, internal fuel flow was observed and theoretically investigated. Meanwhile, the foam layer gradually regresses as it is destroyed by the flame, with a smaller regression rate at a higher foam expansion ratio. Furthermore, the global burning rate of diesel slightly decreases compared with that of no foam discharge, but regardless of the foam expansion ratio or thickness. For n-heptane, total burning develops on the no-foam and foam areas, where the temperature increase rate of the foam-covered fuel decreases mainly depending on the initial foam mass, and the reduction of the radiation heat feedback is mainly related to the foam layer thickness. Meanwhile, foam bubbles are prone to coalescence on the n-heptane surface, which reduces the foam stability and allows it to degrade more quickly. This work helps clarify the mechanisms of foam suppression on high- and low-flash point fuel fire and serves as a guide for engineering applications.

Analysis of Macro- and Microphysical Characteristics of Ice Clouds over the Tibetan Plateau Using CloudSat/CALIPSO Data

Utilizing CloudSat/CALIPSO satellite data and ERA5 reanalysis data from 2007 to 2016, this study analyzed the distributions of optical and physical characteristics and change characteristics of ice clouds over the Tibetan Plateau (TP). The results show that the frequency of ice clouds in the cold season (November to March) on the plateau is over 80%, while in the warm season (May to September) it is around 60%. The average cloud base height of ice clouds in the warm season is 3–5 km, and mostly around 2 km in the cold season. The average cloud top height in the warm season is around 5–8 km, while in the cold season it is mainly around 4.5 km. The average thickness of ice clouds in both seasons is around 2 km. The statistical results of microphysical characteristics show that the ice water content is around 10−1 to 103 mg/m3, and the effective radius of ice clouds is mainly in the range of 10–90 μm. Both have their highest frequency in the west of the TP and lowest in the northeast. A comprehensive analysis of the change in temperature, water vapor, and ice cloud occurrence frequency shows that the rate of increase in water vapor in the warm season is greater than that in the cold season, while the rates of increase in both surface temperature and ice cloud occurrence are smaller than in the cold season. The rate of increase in temperature in the warm season is around 0.038 °C/yr, and that in the cold season is around 0.095 °C/yr. The growth rate of thin ice clouds in the warm season is around 0.15% per year, while that in the cold season is as high as 1% per year. The results suggest that the surface temperature change may be related to the occurrence frequency of thin ice clouds, with the notable increase in temperature during the cold season possibly being associated with a significant increase in the occurrence frequency of thin ice clouds.

The Influence of Thermophysical Parameters on Thermal Runaway Characteristics for Pouch-Type Lithium-Ion Batteries

Abstract The thermal variation during the temperature rise process of batteries is closely related to multiple physical parameters. Establishing a direct relationship between these parameters and thermal runaway (TR) features under abusive conditions is challenging using theoretical equations due to complex electrochemical and thermal coupling. In this paper, a high-temperature thermal runaway model of pouch-type lithium-ion battery is established through electrical-thermal coupled approach, demonstrating a good agreement between the simulation and experimental results. The results reveal distinct trends in thermal parameters of the early temperature rise, trigger time for TR and peak temperature during TR process, for varying convective heat transfer coefficient, cell specific heat capacity, cell density and cell thermal conductivity. Across various convective heat transfer coefficients, the rates of temperature increase, moments of TR, and peak temperatures within a battery emerge as the cumulative outcomes of competing processes of the intricate exothermic secondary reactions within the battery, and the heat transfer with the surroundings. Batteries with lower heat capacity exhibit reduced thermal inertia and heightened sensitivity to temperature changes. Alterations in the thermal capacity of a battery wield a profoundly significant impact upon the moment of thermal runaway within the battery. Enhancing the thermal conductivity yields limited improvements in heat dissipation during thermal runaway primarily due to the relatively small geometrical scale of the battery. Results of this paper can provide valuable insights for size optimization design, thermal management system optimization design, thermal runaway safety warning and prevention of Lithium-ion batteries.

Hypothermia and Influence of Rewarming Rates on Survival Among Patients Admitted to Intensive Care with Bloodstream Infection: A Multicenter Cohort Study.

Although critically ill patients with bloodstream infections (BSIs) who present with hypothermia are at the highest risk for death, it is not known how rewarming rates may influence the outcomes. The objective of this study was to identify the occurrence and determinants of hypothermia among patients admitted to intensive care units (ICUs) with BSI and assess how the rate of temperature correction may influence 90-day all-cause case-fatality. A cohort of 3951 ICU admissions associated with BSI was assembled. The lowest temperature measured within the first 24 hours of admission was identified, and among those who were hypothermic (<36°C), the rewarming rate [(time difference between lowest and subsequent first temperature ≥36°C) divided by hypothermia severity (difference between lowest measured and 36°C)] was determined. Within the first 24 hours of admission to the ICU, 329 (8.4%) and 897 (22.7%) subjects had the lowest temperature measurements ranging <34.9°C and 35-35.9°C, respectively. Patients with lower temperatures were more likely to be admitted to tertiary care ICUs, have more comorbid illnesses, have greater severity of illness, and have a higher need for organ-supportive therapies. The 90-day all-cause case-fatality rate was 22.9% overall and was 45.3%, 24.8%, and 19.6% for those with the lowest 24 hours temperatures of <35°C, 35-35.9°C, and ≥36°C, respectively (p < 0.001). Among 1133 hypothermic patients with documented temperatures corrected to the normal range while admitted to the ICU, the median rate of temperature increase was 0.24 (interquartile range, 0.13-0.45)oC/hour. After controlling for the severity of illness and comorbidity, a faster rewarming rate was associated with significantly lower 90-day case-fatality. Hypothermia is a significant risk factor associated with death among critically ill patients with BSI that faster rates of rewarming may modify.

Projections of temperature and precipitation changes in Xinjiang from 2021 to 2050 based on the CMIP6 model.

Xinjiang is one of the most sensitive regions in China in terms of its response to climate change. Against the background of global warming, analyses and predictions using different scenarios for Xinjiang should be conducted. The spatial and temporal distribution characteristics and trends of future temperature and precipitation trends should be considered to provide a scientific basis for the government to respond to future climate change. In this paper, using the CN05.1 dataset and seven models from the sixth phase of the Coupled Model Intercomparison Project, the delta downscaling method is used to predict the temperature and precipitation changes in Xinjiang Province from 2021 to 2050 under the SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5 scenarios. The results show that (1) most models of CMIP6 have a good effect on temperature simulation in Xinjiang, and the mean values as well as the trends of the temperatures expressed by the multi-model ensemble averaging are in good agreement with the observed data and have a high degree of confidence. The observed precipitation increase rate is significantly higher than that predicted by the model, and the simulation results of each model overestimate the precipitation. (2) The mean annual temperatures in the Xinjiang region increase at rates of 0.32°C/10 a, 0.46°C/10 a, 0.47°C/10 a and 0.67°C/10 a, respectively, under the four scenarios. The rates of temperature increase in the four seasons exhibit the following pattern: autumn > summer > spring > winter. (3) From 2021 to 2050, the average annual precipitation in Xinjiang will change at rates of 3.95 mm/10 a, 1.90 mm/10 a, 2.50 mm/10 a, and 8.67 mm/10 a, respectively, under the four scenarios. The precipitation amounts predicted under the different scenarios increase at the slowest rates in winter and at faster rates in spring. Spatially, the precipitation in the whole Xinjiang region under the four scenarios shows an increasing trend. Overall, except for the SSP1-2.6 scenario, the rates of increase in precipitation increase gradually in all seasons during the future period as the emission scenarios increase. Overall, the climate of the Xinjiang region will be characterized by warming and humidification from 2021 to 2050.

In-situ observation of recrystallization of K-doped tungsten sheets using laser reflection

The microstructure of (doped) tungsten sheets is crucial for their mechanical behavior. Within this study, a new method, based on laser reflection, is proposed to in-situ determine the process of (secondary) recrystallization and the resulting grain size of (doped) tungsten sheets under ultra high vacuum conditions. The system introduced here allows to position the reflection setup at a reasonable distance from the sample to further observe the sample temperature via a pyrometer. The main signals of interest are the reflection intensity, the resulting distribution, and changes thereof. Furthermore, the proposed method can be carried out on polished and as rolled surfaces likewise. This novel method makes it possible to determine the secondary recrystallization temperature (TRx) in rolled (K-)doped tungsten sheets within a single non-isothermal annealing procedure. The average surface grain size during isothermal annealing procedures can be evaluated as well. Even though the observations are generally restricted to the surface, in the case of tungsten sheets a sufficient determination of bulk recrystallization kinetics is possible as well. Furthermore, the obtained results show, that the recrystallization temperature can serve as a sufficient measure to describe the recrystallized microstructure. Even for different sample strains, TRx correctly predicts the average grain size resulting for various temperature increase rates. The proposed method provides a simple, coherent, and robust method to evaluate the recrystallization properties of (doped) tungsten sheets within a single measurement.

Study of the feature of the temperature regime of the Mykolaiv and region in the context of the issue of climate change

Climate change is one of the most important and acute environmental problems of our time. It includes a complex of changes, such as rising ambient temperatures, changes in precipitation patterns, rising sea levels, and more frequent extreme weather events. According to the Intergovernmental Panel on Climate Change (IPCC), the average global temperature has risen by about 1.1°C since the late nineteenth century. Projections point to a possible increase of 1.5°C by the middle of this century unless significant measures are taken to reduce greenhouse gas emissions. On the basis of the above, the paper analyzes trends in changes in atmospheric air temperature on the territory of risky agriculture in the South of Ukraine in the Mykolaiv region.The purpose of the study: to determine and substantiate the regularities of changes in the temperature regime of Mykolaiv and Mykolaiv region in the context of climate change.Research results. The values of temperature characteristics for the year and season in Mykolaiv and Mykolaiv region during 1991−2023 are analyzed. In Mykolaiv, about 60-67 days with a negative average daily air temperature and about 32 days with a negative maximum daily air temperature are recorded. The duration of the period with a negative minimum air temperature can be an average of 93 days per year: 64 in winter, 16 in spring and 14 in autumn. At the same time, on a large territory of the Mykolaiv region, autumn is warmer than spring. The average seasonal air temperature is 10.6°C, the average maximum temperature is 15.4°C, and the average minimum temperature is 6.4°C. In the Northern Black Sea region, both maximum and minimum temperatures in autumn are higher than in spring. The dynamics of changes in average annual temperatures in the city of Mykolaiv in the period from 1980 to 2023 are analyzed. A stable linear trend towards a gradual increase in average annual temperatures has been determined. The warmest year for this observation period is 2023, the coldest are 1985 and 1987. It is determined that the rate of increase in average temperature is 0.61°C for every ten years. Maximum temperatures are increasing at a rate of 0.0884°C per year and minimum temperatures are decreasing at a rate of 0.0136°C per year. Every year, the average annual temperature increases by approximately 0.021°С. The largest number of days accompanied by heat stress (up to 90%) is observed in July – August. Thus, changes in air temperature indicate a significant change in the temperature regime of the entire climate system of the region, and the consequences of climate change may be predominantly negative and will intensify in the future.

Microwave self-healing characteristics of the internal voids in steel slag asphalt mixture subjected to salt-freeze-thaw cycles

Microwave heating technology can be used to repair freeze-thaw (F-T) cycle damage and cracks caused by the use of snow melting salts and de-icers in winter. This study utilized three different gradations of asphalt mixtures: AC-13, SMA-13, and OGFC-13, and enhanced their microwave absorption performance with steel slag (SS). The heating uniformity was evaluated through surface and internal temperature tests. Additionally, the mechanisms of damage and healing of the asphalt mixtures under salt freeze-thaw (S-F-T) damage conditions were explored using S-F-T cycles test and X-ray computed tomography scans (CT). The results showed that OGFC-13 exhibits a significantly higher rate of temperature increase compared to the other two types due to its stronger wave absorption capacity. The thermal hysteresis caused by steel slag leads to uneven spatial temperature distribution. The study recommends an optimal microwave heating time of 40 s for SS asphalt mixtures, which has minimal impact on the mixture structure, by defining an evaluation method for the uniformity index and local overheat ratio. After undergoing S-F-T cycles, the porosity of all three asphalt mixtures increased, particularly at the top and bottom of the specimens. Among them, OGFC-13 exhibited the poorest durability under S-F-T conditions, with the S-F-T cycles having a significant impact on medium-sized voids (0.15–0.6 mm). After microwave heating, AC-13 and SMA-13 showed good repair effects, with porosity levels returning to their initial states. For large voids (>2.36 mm) in OGFC, microwave heating may not effectively reduce the number of voids. Additionally, the healing rate of mixture specimens at certain mid-height ranges is higher due to elevated surface temperatures in these areas, making it especially effective in repairing F-T damage. This study shows that microwave heating of SS asphalt mixtures can improve the durability of pavement in cold regions. However, implementation challenges include the need for specialized equipment and potential uneven heating. Future research should explore optimizing microwave heating techniques to minimize local overheating and investigate the long-term performance of microwave-repaired asphalt pavements under various environmental conditions.

Hydrophobic iron oxide nanoparticles: Controlled synthesis and phase transfer via flash nanoprecipitation

Iron oxide nanoparticles (IONPs) synthesized via thermal decomposition find diverse applications in biomedicine owing to precise control of their physico-chemical properties. However, use in such applications requires phase transfer from organic solvent to water, which remains a bottleneck.Through the thermal decomposition of iron oleate (FeOl), we systematically investigate the impact of synthesis conditions such as oleic acid (OA) amount, temperature increase rate, dwell time, and solvent on the size, magnetic saturation, and crystallinity of IONPs. Solvent choice significantly influences these properties, manipulating which, synthesis of monodisperse IONPs within a tunable size range (10-30 nm) and magnetic properties (75 to 42 Am2Kg-1) is obtained.To enable phase transfer of IONPs, we employ flash nanoprecipitation (FNP) for the first time as a method for scalable and precise size control, demonstrating its potential over conventional methods. Poly(lactic-co-glycolic acid) (PLGA)-coated IONPs with hydrodynamic diameter (Hd) in the range of 250 nm, high colloidal stability and high IONPs loadings up to 43% were obtained, such physicochemical properties being tuned exclusively by the size and hydrophobicity of starting IONPs. They showed no discernible cytotoxicity in human dermal fibroblasts, highlighting the applicability of FNP as a novel method for the functionalization of hydrophobic IONPs for biomedicine.

Millimeter wave radiation to measure blood flow in healthy human subjects

Objective.Peripheral Artery Disease (PAD) is a progressive cardiovascular condition affecting 8-10 million adults in the United States. PAD elevates the risk of cardiovascular events, but up to 50% of people with PAD are asymptomatic and undiagnosed. In this study, we tested the ability of a device, REFLO (Rapid Electromagnetic FLOw), to identify low blood flow using electromagnetic radiation and dynamic thermography toward a non-invasive PAD diagnostic.Approach.During REFLO radio frequency (RF) irradiation, the rate of temperature increase is a function of the rate of energy absorption and blood flow to the irradiated tissue. For a given rate of RF energy absorption, a slow rate of temperature increase implies a large blood flow rate to the tissue. This is due to the cooling effect of the blood. Post-irradiation, a slow rate of temperature decrease is associated with a low rate of blood flow to the tissue. Here, we performed two cohorts of controlled flow experiments on human calves during baseline, occluded, and post-occluded conditions. Nonlinear regression was used to fit temperature data and obtain the rate constant, which was used as a metric for blood flow.Main results.In the pilot study, (N= 7) REFLO distinguished between baseline and post-occlusion during the irradiation phase, and between baseline and occlusion in the post-irradiation phase. In the reliability study, (N= 5 with 3 visits each), two-way ANOVA revealed that flow and subject significantly affected skin heating and cooling rates, while visit did not.Significance.Results suggest that MMW irradiation can be used to distinguish between blood flow rates in humans. Utilizing the rate of skin cooling rather than heating is more consistent for distinguishing flow. Future modifications and clinical testing will aim to improve REFLO's ability to distinguish between flow rates and evaluate its ability to accurately identify PAD.

Continuous monitoring of residual water content in boiling water-hydrocarbon emulsions during thermomechanical dehydration

Significant waste resources are generated in the form of water-oil emulsions. These emulsions cannot be effectively destroyed on an industrial scale by traditional methods that rely on the settling of the aqueous phase, and therefore, they accumulate in large quantities. Thermomechanical dehydration, based on the evaporation of the water phase, presents a promising process for recycling such waste. However, within the framework of thermomechanical dehydration, the issue of optimizing energy costs for heating raw materials and controlling the water content in the product arises. Standard methods of determining water content under the boiling conditions of highly stable water-hydrocarbon emulsions are characterized by low efficiency, as they require constant sampling and the involvement of additional equipment and personnel. Consequently, this presents a challenge in predicting and creating an automated thermomechanical dehydration process. Therefore, dynamic curves depicting changes in the water content of these emulsions, depending on the temperature of the boiling liquid, have been obtained. It is proposed to determine the rate of temperature increase (dT/dt) of the boiling emulsion for continuous, real-time monitoring of the residual water content and for recording the moment of complete dehydration. Achieving a boiling emulsion temperature of 130 °C–170 °C (or higher) and/or the rate of temperature increase from 3.0 to 5.5 (or above) indicates the complete dehydration of the emulsion. The proposed method can be implemented in any industrial or laboratory-scale unit for thermomechanical dehydration without significant capital costs. It is based on the use of simple devices consisting of temperature sensors and a computing unit for determining the temperature and rate of heating.

Topography Controls Variability in Circumpolar Permafrost Thaw Pond Expansion

AbstractOne of the most conspicuous signals of climate change in high‐latitude tundra is the expansion of ice wedge thermokarst pools. These small but abundant water features form rapidly in depressions caused by the melting of ice wedges (i.e., meter‐scale bodies of ice embedded within the top of the permafrost). Pool expansion impacts subsequent thaw rates through a series of complex positive and negative feedbacks which play out over timescales of decades and may accelerate carbon release from the underlying sediments. Although many local observations of ice wedge thermokarst pool expansion have been documented, analyses at continental to pan‐Arctic scales have been rare, hindering efforts to project how strongly this process may impact the global carbon cycle. Here we present one of the most geographically extensive and temporally dense records yet compiled of recent pool expansion, in which changes to pool area from 2008 to 2020 were quantified through satellite‐image analysis at 27 survey areas (measuring 10–35 km2 each, or 400 km2 in total) dispersed throughout the circumpolar tundra. The results revealed instances of rapid expansion at 44% (15%) of survey areas. Considered alone, the extent of departures from historical mean air temperatures did not account for between site variation in rates of change to pool area. Pool growth was most clearly associated with upland (i.e., hilly) terrain and elevated silt content at soil depths greater than one meter. These findings suggest that, at short time scales, pedologic and geomorphologic conditions may exert greater control on pool dynamics in the warming Arctic than spatial variability in the rate of air temperature increases.

Effects of energy sectors on the emission of carbon dioxide gas and environmental temperature

ABSTRACT In this paper, we have proposed a nonlinear mathematical model to study the dynamics of atmospheric carbon dioxide ( CO 2 ) and atmospheric temperature due to energy sectors. Energy sector is a major contributor of atmospheric carbon dioxide. We have studied the effects of energy consumption and human population on CO 2 level and temperature. Burning of fossil fuels results in an increase of CO 2 level and temperature. To curb the CO 2 level and temperature, efficient mitigation options are required. Mitigation options, which reduce emission rate of CO 2 , energy consumption rate and rate of increase in temperature, are considered in this model. By taking the efficiencies of mitigation options as control variables, the optimality system is derived. Numerical simulations are carried out to validate our analytical findings. The optimal profiles of control variables are plotted for different values of emission rate of CO 2 , energy consumption rate and rate of increase in temperature. Maximum efficiencies of mitigation options are also plotted against to reduce emission rate of CO 2 , energy consumption rate and rate of increase in temperature. It is found that mitigation cost of implementation of mitigation options can be minimized by implementing more efficient mitigation options.

Effects of landform and building layout on outdoor thermal environment: a case study of mountain villages in severely cold regions

ABSTRACT In the global context of climate change and frequent occurrence of extreme temperature variations, the impact of harsh climates on the outdoor thermal environment in remote, cold, mountainous villages is particularly pronounced, leading to many negative effects. The geoorphology of the village sites and their building layouts are important factors affecting the outdoor thermal environment. Therefore, exploring the spatiotemporal characteristics of these factors is significant for optimizing village construction and improving living environments. In this study, taking Fangjialiang Village in a cold mountainous area as an example, we analysed the outdoor thermal environment from a spatiotemporal perspective through comprehensive field investigations and measurements. The findings obtained are summarized as follows: (1) Landform elements were limited by boundary and azimuth constraints (difference in time temperature decay rate between the valley interior and valley edge area: ΔK = 0.48°C/m). (2) The temperature inversion phenomenon in the valley was significant (the average rate of temperature increase with elevation was 0.037°C/m). (3) The vertical distribution of the temperature was more susceptible to the influence of the difference in elevation inside the village (ρ≈–0.48). The average rate of temperature decrease with elevation is 0.489°C/m. (4) A compact building layout could sustainably weaken the effects of topographic elements (e.g. the average temperature sequenced as: closed internal courtyard (Avg = 14.60°C)> semi-open horizontal village street (Avg = 13.58°C)> fully open space (Avg = 13.11°C)). Therefore, the results of the study further revealed the coordinated relationship between the natural environment and rural settlements, proved the integrated effects of village siting and building layout, and provided useful insights for the construction and living environment optimization of mountain villages.

Heat transfer characteristics of oil receiving and delivering process in crude oil storage tanks

The study used numerical simulation methods to investigate the influence of different oil receiving and delivering cases on the non-uniform physical field within the storage tank. The results showed that the evolution of the physical field can be divided into three stages: diffusion, suppression, and equilibrium. The computational domain was divided into three zones based on the crude oil heating rate: significant influence zone, indirect influence zone, and minimal influence zone, and the indirect influence zone exhibits the most pronounced variations in velocity and temperature. The process of receiving oil with high-flow rate and low-temperature was found to be more conducive to the full use of heat in the tank when the heat exchanging quantity per unit time was the same. The synergistic effect of tubular heating and oil receiving and delivering resulted in a 21 % higher average temperature increase rate than the sum of the two processes. Finally, the study quantitatively described the linear relationship between the average temperature in each region and factors such as oil inlet velocity, oil receiving temperature, oil receiving and delivering time, and heating tube temperature, providing theoretical guidance for process planning in actual oil storage tank receiving and delivering.

Insights into the Mechanical-Structural-Energetic Responses of RDX Nanoparticles from Molecular Dynamics Simulation.

When the particle size of energetic materials is reduced to the nanoscale, significant changes occur in their properties and behavior. In this work, compression processes of three RDX nanoparticles (A, B, and C) were simulated using ReaxFF-lg. The mechanical, structural, and energetic responses of RDX nanoparticles during compression were revealed and characterized. Simulations reveal that the compression process of the nanoparticles can be divided into three stages: elastic stage, primary damage stage, and sustained damage stage. The temperature increase rate in the elastic phase is much lower than in the primary damage phase. In addition, we found that the smaller nanoparticle B presents a smaller elastic modulus and compressive strength, and it has a slower rate of temperature increase during the primary damage phase. Compared to cuboidal nanoparticles (A and B), the spherical nanoparticle C tends to absorb less energy during the elastic stage and exhibits slower damage rate during the primary damage stage. This is a key factor contributing to the low sensitivity of spherical nanoparticles.

Variation of temperature increase rate in the Northern Hemisphere according to latitude, longitude and altitude: the Turkey example

Global climate change notably influences meteorological variables such as temperature, affecting regions and countries worldwide. In this study, monthly average temperature data spanning 73 years (1950–2022) were analyzed for 28 stations in the city centers across seven regions of Turkey. The station warming rates (SWR) were calculated for selected stations and the overall country using Singular Spectrum Analysis (SSA) and Least Square Polynomial Fit (LSPF) methods. The temperature trend in Turkey exhibited a decline until the late 1970s, followed by a continuous rise due to global warming. Between 1980 and 2022, the average SWR in Turkey was found to be 0.52 °C/decade. The SWR was determined to be the lowest in Antakya (0.28 °C/decade) and the highest in Erzincan (0.69 °C/decade). The relationship between SWR and latitude, longitude, altitude, and distance to Null Island (D2NI) was explored through linear regression analysis. Altitude and D2NI were found to be the most significant variables, influencing the SWR. For altitude, the correlation coefficient (R) was 0.39 with a statistically significant value (p) of 0.039. For D2NI, R, and p values were 0.39 and 0.038, respectively. Furthermore, in the multiple regression analysis involving altitude and D2NI, R and p values were determined to be 0.50 and 0.029, respectively. Furthermore, the collinearity analysis indicates no collinearity between altitude and D2NI, suggesting that their effects are separated in the multiple regression.

Study of heat transfer and hydrodynamic processes in a full-size thermosyphon installation under the influence of solar radiation with coolant

Abstract This article discusses the theoretical background and results of the study of heat exchange and hydrodynamic processes occurring in a thermosiphon installation. One of the important characteristics of the operation of thermosiphons is their ultimate heat transfer capacity, the calculation of which allows us to create a reliable, highly efficient heat exchange device. For optimal design and improvement of the technical and economic indicators of a thermosiphon installation, it is necessary to develop and improve scientifically based methods for calculating the processes occurring in the elements of its design. The purpose of the experimental part of the work was to test the selected theoretical model and more accurately determine the physical picture of the processes occurring in full-scale thermosiphon installations by measuring not only integral, but also local characteristics of the installation. There is intense heating of the liquid in the collector in the first half of the day (from 11 to 13 hours) and a slowdown in the rate of increase in temperature at the outlet of the collector in the second half of the day. A drop in the level of solar radiation in the second half of the day does not lead to a significant decrease in the temperature at the outlet of the collector, which is obviously explained by an increase in the temperature of the liquid at the inlet to the collector during the period under consideration. The presence of a long period of lag in the increase in the temperature of the liquid at the inlet to the collector compared to the temperature at the outlet is associated with the inertia of thermal processes in the system. The time interval from the beginning of the experiment to the beginning of the increase in the temperature of the liquid at the inlet to the collector coincides with the period of a single circulation of the liquid in the system.

The Comparison A-Optimal and I-Optimal Design in Non-Linear Models to Increase Purity Levels Silicon Dioxide

One of the obstacles that arise in optimal design is the non-linear model. The relationship between temperature factors and the temperature increase rates with the purity of silicon dioxide (SiO2) forms a non-linear pattern. Determining the optimal design for a non-linear model is relatively more complex than a linear model because it requires additional information in its information matrix. Therefore, this issue necessitates further research on optimal design in non-linear models. This study uses the polynomial Taylor approach to approximate the non-linear equation through a linear equation using the appropriate optimal design methods, namely A-Optimal and I-Optimal criterion. The point search algorithm used was variable neighborhood search, this algorithm searches for design points by exploring several different neighborhood structures. These two methods were chosen to compare the characteristics and performance of the designs produced, aiming to obtain an optimal design to improve SiO2 purity (non-linear case) using the same algorithm, VNS. The research results showed that the design pattern produced by the A-Optimal design formed three temperature groups, namely the minimum temperature of 800°C - 820°C, the middle temperature of 850°C, 860°C, and the maximum temperature of 900°C, with varying temperature increase rates in the design area. The design pattern produced by the I-Optimal design formed a full quadratic pattern, namely the minimum temperature of 800°C and the maximum temperature of 900°C, with varying temperature increase rates in the design area. The I-Optimal design demonstrated the best performance (most optimal) in the aspect of prediction variance compared to the A-Optimal design across all alternative points in this study to improve SiO2 purity.

Pyrolysis kinetics of waste ryegrass under nitrogen and air atmosphere

To investigate the pyrolysis reaction of ryegrass, we conducted a simultaneous thermal analysis using thermogravimetric(TG) analyzers. This involved obtaining data through Thermogravimetry (TG), Derivative Thermogravimetry (DTG), and Differential thermal analysis (DTA) techniques. The experiments were conducted under dynamic nitrogen and air atmospheres at different heating rates. The kinetic parameters of ryegrass pyrolysis were determined using the Kissinger method, the Flynn-Wall-Ozawa (FWO) peak conversion rate approximate equivalence method, the Flynn-Wall-Ozawa (FWO) equal conversion rate method, and the Škvára-Šesták (S–S) method. It provides a theoretical basis for the reuse of ryegrass resources. The findings indicated that the pyrolysis temperature of ryegrass increased with the accelerated rate of temperature increase in both atmospheres. The average weight loss rate of pyrolysis of ryegrass in the air atmosphere (92.27 %) is higher than that compared to that in a nitrogen atmosphere (86.11 %). Additionally, the temperature required for complete decomposition is lower in the former case. The FWO peak conversion rate approximation equivalence approach and the FWO equal conversion rate method do not apply to the solution of the pyrolysis activation energy of ryegrass. The pyrolysis activation energy for the two decomposition stages, as calculated by the Kissinger method, is 165.73 and 185.86 kJ/mol−1 in the air atmosphere, and 219.99 and 277.02 kJ/mol−1 in a nitrogen atmosphere, respectively. The activation energy and mechanism function of ryegrass pyrolysis calculated by using the S–S method are as follows: [−ln(1−α)]2, 119.79, 104.31, 95.75, and 91.93 kJ/mol−1 in air atmosphere, (1−α)−1, 176.64, 67.89, 61.15, and 54.25 kJ/mol−1 in nitrogen atmosphere, respectively. The activation energy of ryegrass pyrolysis, as determined by both the Kissinger method and S–S method, was found to be higher under an air atmosphere compared to a nitrogen atmosphere.