Effect Of Temperature Variation Research Articles

Effects of climate variability on secondary xylem formation and anatomy in fagus sylvatica trees grown in Denmark

ABSTRACT Tree-ring width chronologies of Fagus sylvatica L. have been studied to understand the growth–climate relationship in Denmark, but there is little evidence of a clear climate signal in such tree-ring width data. In this study, tree-ring width chronologies of F. sylvatica trees growing in an even-aged stand in Denmark over the period 1972–2012 were supplemented with wood density and quantitative wood anatomy variables using the SilviScan-3 combined set-up. The effects of moisture availability and temperature variations on xylem features were investigated. Some xylem features showed stronger associations with drought index (DI) and temperature than ring width. Specifically, the September drought was associated with an increased mean area of the individual fibers in the ring formed the following year. Drought in October resulted in a higher density the following year, probably via increased fiber wall thickness and decreased areas of individual vessels. Further, late summer and early autumn warming increased the vessel density in the following year, but drought reduced their cross-sectional area. By dividing tree rings into ten segments, relationships between wood density and DI could be evaluated at the intra-annual level. In the third segment, wood density decreased with previous year December drought, while the April drought increased the wood density of this segment. Together, the results indicated that xylem formation and anatomy in F. sylvatica seem to be linked to moisture availability and temperature, and that dry and warm conditions affect xylem features differently depending on when they occur relative to wood formation.

Superelastic behavior of novel Ni–Ti–Co shape memory alloys for seismic applications

Abstract Ni–Ti–Co is a new shape memory alloy (SMA) composition that has a higher strength and a lower superelastic temperature range than the traditional binary Ni–Ti SMA composition. In this paper, the superelastic properties of Ni–Ti–Co bars that are important for seismic applications were studied and compared with those of Ni–Ti bars. The superelastic behavior, strength, strain recovery, low-cycle fatigue characteristics, and fracture strains of Ni–Ti–Co and Ni–Ti SMA with different heat treatment strategies and testing temperatures from −40 °C to 50 °C were investigated with seismic applications in mind. The effect of low-cycle fatigue loading and temperature variations on the superelasticity degradation of Ni–Ti–Co SMA were evaluated. The results showed that the yield stress of Ni–Ti–Co SMA at room temperature was 1.41–1.74 times that of the Ni–Ti SMA. Ni–Ti–Co SMA exhibited 100% strain recovery when unloaded from 5% strain in a temperature range from −40 °C to room temperature; while at 50 °C, a residual strain of 0.6% was observed when unloaded from 5% strain. For comparison, the Ni–Ti SMA lost superelasticity when the temperature was reduced to 0 °C. When subjected to low-cycle fatigue loading, the stability of the superelastic behavior (maintaining yield stress, energy dissipation and strain recovery) of Ni–Ti–Co SMA at −40 °C was better than that at room temperature and 50 °C. In particular, the superelasticity of Ni–Ti–Co SMA at −40 °C was superior to that of the Ni–Ti SMA at 0 °C. At −40 °C, the Ni–Ti–Co SMA showed almost no loss in yield stress, damping ratio and recovery strain during the first 100 cycles of fatigue loading. Moreover, from 100th to 471st cycle, at which the fracture occurred, the strain recovery of Ni–Ti–Co SMA showed almost no degradation.

Optimization Model for Climatic Change Impact on the Water Quality of Al-Hilla River, Iraq

Optimization Model for Climatic Change Impact on the Water Quality of Al-Hilla River, Iraq

Effects of Seasonal and Temperature Variations on the Association between Nitrogen Dioxide Exposure and First-Aid Incidence for Neurological Diseases in Shenzhen, China

Effects of Seasonal and Temperature Variations on the Association between Nitrogen Dioxide Exposure and First-Aid Incidence for Neurological Diseases in Shenzhen, China

Compensation of temperature effects on imaging quality of thermal imaging objectives using deep learning techniques

Thermal imaging objectives are made from infrared materials with large thermal expansion coefficients, such as Ge, Si, and ZnSe. When the temperature changes, it leads to variations in the refractive index, curvature radius, and thickness of the lens, causing defocus shifts that degrade the image quality of the thermal imaging system. In this paper, we propose a novel method to compensate for the effects of temperature variations on the quality of thermal imaging objectives by using deep learning techniques. The temperature variations are measured using a thermal sensor. Subsequently, a U-Net network is employed to mitigate the impact of temperature on the imaging quality of the thermal imaging objectives without requiring any optical displacement or replacement of the lens. Simulation results show that the proposed method performs the effectively compensation for the influence of temperature changes on thermal imaging objective over a wide temperature range from -5 °C to 50 °C.

Metabolism Variations in the Bivalve Mollusk <i>Anadara kagoshimensis</i> Tokunaga, 1906 (Bivalvia: Arcidae) under Upwelling Conditions in the Black Sea (Experimental Data)

Studies of the energy metabolism in a bivalve mollusk, the ark clam Anadara kagoshimensis (Tokunaga, 1906), were carried out for the first time under experimental conditions simulating dynamic variations in the seawater characteristics at the stages of development and end of upwelling event in the Black Sea. It was shown that the level of energy metabolism of A. kagoshimensis, while being in the zone of upwelling formation, reduced, on average, by 5% per degree of temperature decrease. During the upwelling relaxation phase (14→26°C), the restoration of the respiration intensity parameters of the clam was slower than expected, with a temperature coefficient Q10 = 1.31. The acidification of the seawater by 1.0 (up to рН 7.2), combined with a temperature decrease (26→20°C), aggravated the negative effect by 25–45%. It has been found that the clam A. kagoshimensis reduces energy expenditure by approximately 60% under upwelling conditions (cold stress and acidification). Consequences of the negative effect of a sharp temperature variation lead to a delay in the metabolism recovery to normal values.

Effects of Physiological-Scale Variation in Cations, pH, and Temperature on the Calibration of Electrochemical Aptamer-Based Sensors.

Electrochemical aptamer-based (EAB) sensors are the first technology supporting high-frequency, real-time, in vivo molecular measurements that is independent of the chemical reactivity of its targets, rendering it easily generalizable. As is true for all biosensors, however, EAB sensor performance is affected by the measurement environment, potentially reducing accuracy when this environment deviates from the conditions under which the sensor was calibrated. Here, we address this question by measuring the extent to which physiological-scale environmental fluctuations reduce the accuracy of a representative set of EAB sensors and explore the means of correcting these effects. To do so, we first calibrated sensors against vancomycin, phenylalanine, and tryptophan under conditions that match the average ionic strength, cation composition, pH, and temperature of healthy human plasma. We then assessed their accuracy in samples for which the ionic composition, pH, and temperature were at the lower and upper ends of their physiological ranges. Doing so, we find that physiologically relevant fluctuations in ionic strength, cation composition, and pH do not significantly harm EAB sensor accuracy. Specifically, all 3 of our test-bed sensors achieve clinically significant mean relative accuracy (i.e., better than 20%) over the clinically or physiologically relevant concentration ranges of their target molecules. In contrast, physiologically plausible variations away from the temperature used for calibration induce more substantial errors. With knowledge of the temperature in hand, however, these errors are easily ameliorated. It thus appears that physiologically induced changes in the sensing environment are likely not a major impediment to clinical application of this in vivo molecular monitoring technology.

Testing the prediction capability of trained models: sildenafil citrate solubility in propylene glycol and 1-propanol mixtures at different temperatures

ABSTRACT This study investigates the thermodynamic characteristics, equilibrium solubility, and solvation dynamics of sildenafil citrate within binary solvent systems composed of propylene glycol and 1-propanol. Utilizing both determination and computational approaches, the solubility patterns of sildenafil citrate were quantitatively assessed, revealing direct proportionality with increments in temperature and the concentration of propylene glycol. A comparative analysis using three distinct mathematical models to represent the solid–liquid phase equilibrium was conducted. Among these, the Jouyban-Acree-van’t Hoff model yielded the most comprehensive correlation by covering the effects of both temperature and solvent composition variations on the solubility, with a mean relative deviation (MRD%) of 6.4%, suggesting a robust alignment between the modelled and experimental solubility data. Previously trained models were tested to predict the solubility of the drug in mono- and mixed-solvents at various temperatures where accurate predictions were obtained with the MRD% of 19.1% (for mono-solvents), 8.1 and 14.4% (for mixed solvent systems).

Effect of temperature variation on bonding properties of magnesium potassium phosphate cement: A multiscale analysis

In magnesium potassium phosphate cement (MKPC) repair work, varying ambient temperatures significantly affect the repair outcomes. To quantitatively characterize the effect of temperature variation on the bonding properties of MKPC, this paper comprehensively explores the issue at multiple levels, evaluating the bonding properties of the combined specimens using double-shear tests, scanning electron microscope tests, and nuclear magnetic resonance tests, followed by quantitatively characterizing the form of interfacial damage using digital image processing of interfaces. Finally, the Pearson correlation coefficient method was employed to analyze the correlation between different scales. The results indicate that, for the MKPC combined specimens, the interface shear bearing capacity slightly decreased at low temperatures and improved back to normal temperature, with a retention coefficient (K) of 0.977. The internal structure was dominated by small holes, whereas at high temperatures, the capacity severely decreased, with K only 0.4, and a large number of large holes and cracks were present internally. The DIP results reveal that the interface damage forms of the combined specimens at low temperatures were dominated by the MKPC-NC interface, which accounted for 76.38 %. At high temperatures, the damage was mostly within the MKPC, with the MKPC interface accounting for 52.06 % of the fracture interface of the specimen. Pearson correlation analysis demonstrates that temperature has a strong relationship with the scale indicators, with an |R| value greater than 0.7. The |R| value between macroscopic performance and microstructure is 0.95, providing strong evidence that macroscopic performance can be characterized by the microstructure.

Thermomechanobiology as a new research field in soft tissues

During intense galloping, the difference in temperature between the external and the central part of an equine superficial digital flexor tendon can be as high as 7°C. Thirty minutes of jogging modifies the temperature in human knee cartilage from 32°C to 37°C. Intrinsic dissipative phenomena related to the viscoelastic behavior of soft tissues have been identified to be primarily responsible for the observed temperature increase, a situation referred to as self-heating in mechanics. While a 5°C increase may be considered negligible from a mechanical point of view in the cartilage at first sight, it can have a significant biological impact. It has been recently proposed that self-heating and the resulting increase of temperature in cartilage following mechanical stimulation can be necessary for its maintenance. This new concept complements the general acceptance that mechanobiology is central to the homeostasis of musculoskeletal tissues. In most biomechanical and biological studies on cartilage or other soft tissues, the temperature is set at 37°C and considered constant, despite human knee cartilage at rest being around 32°C, for example. Therefore, there is a deficit of information on the role and effect of physiological temperature variation induced through mechanical loading in soft tissues, opening a new research avenue that we coin thermomechanobiology.

A Study of the Effect of Temperature on the Capacitance Characteristics of a Metal-μhemisphere Resonant Gyroscope.

Metal-μhemispherical resonant gyros (M-μHRGs) are widely used in highly dynamic navigation systems in extreme environments due to their high accuracy and structural stability. However, the effect of temperature variations on the capacitance characteristics of M-μHRGs has not been fully investigated, which is crucial for optimizing the performance of the gyro. This study aims to systematically analyze the effect of temperature on the static and dynamic capacitances of M-μHRGs. In this study, an M-μHRG structure based on a 16-tooth metal oscillator is designed, and conducted simulation experiments using non-contact capacitance measurement method and COMSOL Multiphysics 6.2 finite element simulation software in the temperature range of 233.15 K to 343.15 K. The modeling analysis of the static capacitance takes into account the thermal expansion effect, and the results show that static capacitance remains stable across the measured temperature range, with minimal effect from temperature. The dynamic capacitance exhibits significant nonlinear variations under different temperature conditions, especially in the two end temperature intervals (below 273.15 K and above 313.15 K), where the capacitance values show local extremes and fluctuations. In order to capture this nonlinear behavior, the experimental data were smoothed and fitted using the LOESS method, revealing a complex trend of the capacitance variation with temperature. The results show that the M-μHRG has good capacitance stability in the mid-temperature range, but its dynamic performance is significantly affected at extreme temperatures. This study provides a theoretical reference for the optimal design of M-μHRGs in high- and low-temperature environments.

Physiological responses to different temperature in the liver of Takifugu rubripes larvae revealed by integrated transcriptomic and metabolomic analyses

Water temperature plays a vital role in shaping the physical conditions crucial for the growth, development and reproduction of fish species. Since limited comprehensive multi-omics analyses exploring the molecular mechanisms of temperature influences on the early life stages of fish. Here, the effects of temperature variations on the growth of Takifugu rubripes, a commercial teleost farmed in Asia were investigated. Nineteen-days-old fugu larvae were subjected to different temperature (15 °C-T15, 20 °C-T20, 25 °C-T25) for 30 days. Liver tissues were harvested at the end of the study for transcriptomic and metabolomic assessments. The T. rubripes larvae in the T15 group showed a significant decrease in total length and body weight compared to the T20 and T25 groups (p < 0.05). 1344, 416, and 2080 differentially expressed genes (DEGs) were identified in T15-vs-T20, T20-vs-T25, and T15-vs-T25 comparisons, respectively. Those DEGs were mainly enriched in metabolic, protein digestion and absorption, steroid biosynthesis, and glycerophospholipid metabolism pathways. 15 DEGs were randomly selected for RNA-seq validation, and the transcriptome results were consistent with the qPCR validation results, illustrating the accuracy of transcriptome sequencing. 340, 238, and 330 significantly different metabolites (SDMs) were identified in positive modes when comparing in T15-vs-T20, T20-vs-T25, and T15-vs-T25, respectively. Additionally, 145, 137, and 159 SDMs were identified in negative modes within the three comparisons. Those SDMs enriched in biosynthesis of secondary metabolites, glycerophospholipid metabolism, linoleic acid metabolism, and metabolic pathways. The integration of transcriptomic and metabolomic analyses indicated that DEGs and SDMs mainly enriched in metabolic pathways. These discoveries provide valuable insights into the effects of temperature on fish larvae in aquaculture, laying a foundation for future breeding approaches aimed at improving the growth of T. rubripes.

System Modeling-Based Investigation of SMR Operations Using Variable T-avg Control for Cost-Effective Electricity Generation in a Grid

Given the importance of nuclear power as low carbon energy source, this study conducted techno-economic evaluation of flexible use (baseload as well as load-following) of small modular reactors (SMRs) in an electric grid. The load-following operation of SMR (SMART-100) was restricted to the use of variable T-avg control, a least disruptive and cost minimizing method of load follow control. A system model was developed to describe the reactivity feedback effects of coolant temperature variations due to electric demand-based turbine load changes. Using the system model, conservative output ranges and maximum ramp rates that allow load-following operation without violating axial offset limits were derived. Assuming the introduction of SMR in Jeju Island in South Korea, a semi-independent grid region, with highly dependency on fossil fuel energy and power imports along with significant renewable energy generation (15–20 %), as a test case, this study evaluated the economic contribution of SMR using LPM to minimize the grid electricity generation costs. The results indicate that in regions with a high penetration of renewable energy in their grid systems, flexible energy generation of SMR can make a significant contribution in reducing electricity generation cost and carbon emissions.

Appraising the corrosion inhibitory efficacy and adsorption mechanism of leaf extract of Datura discolor on low-carbon steel in low pH media via gravimetric experiments and AFM analysis

BackgroundThe study investigated the inhibitory action of Datura discolor leaf extract against the corrosion of low-carbon steel in 0.5 M solutions of three acids. The purpose was to ascertain the effect of extract concentration, immersion time and temperature variation on corrosion inhibitory efficiency, and to relate to existing reports which show that organic molecules in most plant extracts inhibit corrosion. Extraction of the leaves was done by maceration using methanol, and solvent was removed by evaporation to dryness. Classical gravimetric (mass loss) experiments were used, and experimental data were fitted to adsorption isotherm models to ascertain the best approximation. Surface examination of the low-carbon steel substrates was carried out using the atomic force microscope.ResultsInhibitory protective efficiency of extract was found to appreciate with increasing Datura discolor leaf extract concentration at a fixed temperature, with values ranging 77.6–88.8%, 91.35–98.08% and 19.64–44.64% in H2SO4, HCl and HNO3 solutions respectively at 27 °C. Elevation of temperature was found to depreciate the inhibitor efficiency at constant inhibitor concentration. Best isotherm model fitting was obtained with Langmuir model both at 27 °C and 60 °C and in all the hostile media, while Temkin model gave good approximation only at 60 °C and in H2SO4 and HCl solutions only. The negative values of free energy of adsorption (ΔGads0)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$(\\Delta G_{{{\ ext{ads}}}}^{0} )$$\\end{document} suggested that the adsorptive interaction of the inhibitor with the substrate surface was very spontaneous. Values of ΔGads0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Delta G_{{{\ ext{ads}}}}^{0}$$\\end{document} were all consistent, fluctuating between − 16.35 and − 17.63 kJ mol−1 in both H2SO4 and HCl solutions, and between − 9.76 and − 10.25 kJ mol−1 in HNO3 solution, and this suggests that adsorption of the inhibitor molecules occurred via physisorption. Values of the activation energy of the corrosion reaction (Eact)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$(E_{{{\ ext{act}}}} )$$\\end{document} are all < 40 kJ mol−1, suggesting that the inhibition occurred by a physical adsorption mechanism.ConclusionsThe study concludes that Datura discolor crude leaf extract suppressed the corrosion reactions, and the inhibition was found to arise from the physisorptive interaction of the organic molecules with the substrate/solution interface, forming a stabilize inhibitor film on the substrate surface as revealed by the atomic force micrographs.

Analysis of Tubular NF Plants in Scotland Indicates That Summer Temperatures and Redox-Sensitive Elements Are Correlated with Membrane Biofouling and Shortened Useful Life.

We investigate the effects of seasonal variations in water composition and temperature on the performance of two full-scale drinking water treatment plants in Scotland, equipped with tubular cellulose acetate nanofiltration membranes. Multiple environmental and water quality parameters, recorded over a 4.5-year period, were correlated against membrane permeance, cleaning frequency, and useful life. Membrane autopsies enabled the characterization of the foulant composition. Temporal variations in temperature at plant X led to significant biofouling (manifested by permeance losses of 30-50%, and bacteria detected on the membrane surface) during the summer months, when water temperatures exceeded 20 °C and microbiological activity was highest. Plant Y, in contrast, displayed smaller seasonal variations and was operationally stable without significant fouling. A pronounced increase in manganese and iron (up to 200 and 600 μg/L, respectively) in the lake water at plant X in summer was accompanied by elevated content (∼60 mg/m2) of those metals on the membrane surface, which was consistent with lake thermal stratification and metal input from the sediment into the water column. Our work shows that membrane plants in regions supplied by standing surface water bodies, such as plant X, are more vulnerable to biofouling, especially during warmer months.

Studying the effect of ambient temperature variations on perovskite precursor film formation using different antisolvents

This study investigates the sensitivity of two antisolvents to ambient temperature fluctuations during the fabrication of triple-cation perovskite thin films. Chlorobenzene (CB) and ethyl acetate (EA) were employed as antisolvents in the preparation of perovskite solar cells (PSCs) under identical ambient temperature variation conditions. The experimental results reveal that the quality of the perovskite films does not exhibit a consistent trend in response to ambient temperature changes depending on the antisolvent used. When CB was used as the antisolvent, the highest-performing device, produced at an ambient temperature of 18 °C, achieved a power conversion efficiency (PCE) of 19.9 %. In contrast, when EA was employed as the antisolvent, the highest-performing device was fabricated at 25 °C, reaching a PCE of 20.5 %. Furthermore, when the ambient temperature exceeded 30 °C, all films prepared with either antisolvent exhibited significant cracking, indicating that elevated temperatures adversely affect perovskite film formation. To further investigate the mechanism through which ambient temperature affects the film-forming process, antisolvents at varying temperatures were used during perovskite film preparation to simulate transient temperature increases during formation. This study reveals that the impact of ambient temperature variations on perovskite film formation does not exhibit a uniform trend but is significantly influenced by the choice of antisolvent. Moreover, this work offers valuable insights for optimizing the fabrication of high-quality perovskite thin films.

High-Q coupled topological edge state in 1D photonic crystal mirror heterostructure for ultrasensitive thermal sensing

This work explores a novel 1D topological photonic crystal (PC) mirror heterostructure for high-performance thermal sensing. The design leverages a unique coupled topological edge state mode (CTES) exhibiting exceptional light confinement at the interface, characterized by a record-high quality (Q) factor. The study investigates the effects of nematic liquid crystal (NLC) integration and temperature variations to enhance functionality. Two NLC defect configurations are explored: complete replacement of silica layers and localized replacement within one topological PC. In both scenarios, the CTES mode exhibits tunability in frequency and Q factor due to the thermo-optic properties of the NLC. This dynamic control offers advantages for various applications beyond thermal sensing, including filtering and switching. The first NLC configuration achieves an outstanding Q factor of 107, surpassing the intrinsic value. Additionally, it demonstrates exceptional thermal sensitivity (−0.12317 nm/°C) and a remarkable figure of merit (1002.48 °C−1). These superior sensing characteristics are attributed to the strong light localization at the interface and the intensified light-matter interaction facilitated by the NLC. The second configuration offers a trade-off between sensitivity and tunability, exhibiting a Q factor in the 106 range, a sensitivity of −0.05853 nm/°C, and a figure of merit of 86.53 °C−1. This study presents a groundbreaking design for 1D topological PC mirror heterostructures with integrated NLC. This platform holds immense promise for developing high-performance, tunable narrowband filters and ultrasensitive thermal sensors, paving the way for advancements in diverse photonic applications.

An Experimental Study of an Autonomous Heat Removal System Based on an Organic Rankine Cycle for an Advanced Nuclear Power Plant

The present study focuses on the recovery of waste heat in an autonomous safety system designed for advanced nuclear reactors. The system primarily relies on passive safety condensers, which are increasingly integrated into the design of advanced Pressurized Water Reactors (PWRs). These condensers are typically immersed in large water tanks that serve as heat sinks and are placed at sufficient heights to ensure natural circulation. Such a heat removal system can operate for an extended period, depending on the size of the tank. This research is driven by the potential to recover part of the energy stored in the boiling water volume, using it as a heat source for an Organic Rankine Cycle (ORC) system via an immersed heat exchanger. The electricity generated by the ORC engine can be used to power the system components, thereby making it self-sufficient. In particular, a pump replenishes the water tank, ensuring core cooling for a duration no longer limited by the water volume in the tank. An experimental test setup, including a boiling water pool and an ORC engine with an electrical output of approximately several hundred watts, along with an immersed evaporator, was constructed at CEA (Grenoble, France). Several test campaigns were conducted on the experimental test bench, exploring different configurations: two distinct ORC working fluids, cold source temperature variation effects, and relative positioning of the submerged evaporator and heat source within the water tank impact. These tests demonstrated the reliability of the system. The results were also used to validate both the ORC condenser and evaporator models. This article presents this innovative system, which has recently been patented. Moreover, to the best of our knowledge, the investigated configuration of an ORC that includes an immersed evaporator is original.

Nonlinear performance of aerospace face gear-planetary gear transmission system under multi-factors including the effect of temperature

Face gear-planetary gear transmission system combines the advantages of both planetary and face gears. And has enormous advantages in the aerospace field. The meshing of gear teeth generates heat through friction, resulting in thermal deformation and affects nonlinear dynamic characteristics. Exploring the temperature effect on the nonlinear dynamics of the transmission system of face gear-planetary gear is of great significance. Considering the temperature variations effect and time-varying meshing stiffness, tooth side clearance as well as meshing error, a nonlinear dynamic model of the face gear-planetary gear system is established. The nonlinear dynamic characteristics of the system were described by maximum Lyapunov exponent diagram, phase diagram, bifurcation diagram et al. The findings indicate that the effect of temperature variations on the gear system is related to the values of the time-varying mesh stiffness coefficient and mesh damping ratio. When the mesh damping ratio is small, the influence of temperature changes on the bifurcation characteristics of the system is more obvious. As the time-varying mesh stiffness value increases, the temperature rise gradually stabilizes in the range of 15°C to 42°C; Under certain temperature changes, as the meshing damping ratio and time-varying meshing stiffness coefficient increase, the face gear planetary gear system gradually tends to stabilize.

Scrutinizing effect of temperature and pressure variation of a double-pressure dual-cycle geothermal power plant turbines on the temperature profile and heat gain of the heat exchangers

In geothermal power plants with dual pressure cycle technology, the optimisation of turbine inlet parameters depending on the pressure and temperature of the geothermal fluid is a very important parameter affecting the production capacity of such plants. In combined systems, where the second stage (low pressure) is fed by the first stage (high pressure), failure to determine the appropriate operating conditions leads to the problem of not achieving optimum performance. In this context, the study aims to develop a methodology for predicting the performance of the system, based on the geothermal water temperatures entering and leaving the heat exchangers, in order to clearly see the effect of the operations carried out within the scope of optimising the turbine inlet parameters on the system behaviour. In this study, EBSILON® Professional software developed by Steag GbmH was utilised to simulate the determined correlations. The effect of the heat exchangers (preheater, evaporator and superheater) in both stage-1 and stage-2 on the temperature profiles and heat gains were determined at 10–17 bar, 126.5–165 °C for Turbine-1 and 4–8 bar, 84–135 °C for Turbine-2. Optimum turbine inlet temperature and pressure have been determined for maximum heat input and exergy efficiency. In this context, each cycle in the Energy Converter System (ECS) was first simulated by changing the turbine input parameters and then thermal analyses of the system were performed using the performance outputs obtained from the simulation software. For turbine-1, it is observed that heat transfer decreases in stage-1 with increasing pressure and temperature, while heat transfer increases in stage-2 fed from stage-1. After 12 bar and 136 °C, the heat transfer of the ECS started to increase and the maximum heat transfer amount was reached at 17 bar and 155 °C. However, it was determined that the exergy efficiency of the ECS started to decrease after 15 bar and 147.6 °C. For turbine-2, it was found that the increase in pressure and temperature decreases the ECS heat transfer but increases the exergy efficiency. As a result of numerous iterations with EBSILON® Professional software, a maximum exergy efficiency of 50.53% was achieved in turbine-1 (15 bar, 147.6 °C) and turbine-2 (8 bar, 114 °C).