Rate Of Temperature Increase Research Articles

Multi-objective optimization of the dual-pressure organic Rankine cycle system based on the orthogonal design method under different external conditions

The dual-pressure organic Rankine cycle (DPORC) system can obtain a better temperature match between the heat source and working fluid due to the existence of two evaporation processes, which can significantly improve the utilization rate of the heat source and reduce the irreversible loss. Firstly, single-objective optimization of the DPORC system is conducted based on the orthogonal design method with thermal efficiency, exergy efficiency, electricity production cost (EPC) and annual emission reduction (AER) as the performance indicators, respectively. Then, multi-objective optimization of all performance indicators is carried out based on the comprehensive scoring method. Finally, the contribution rates of the operation parameters and the optimal working conditions under different external conditions are investigated. The results show that condensation temperature, high-pressure evaporation temperature and turbine isentropic efficiency are the most critical parameters for system comprehensive performance. When heat source temperature is 170 °C, thermal efficiency, exergy efficiency, EPC and AER under the optimal working conditions are 11.91%, 48.46%, 2.71 × 10−2$/kWh and 11.17 × 105kg, respectively. With the increase of heat source temperature, condensation temperature and turbine isentropic efficiency always have an important influence on system comprehensive performance. The contribution rates of high-pressure evaporation temperature and low-pressure evaporation temperature increase and decrease, respectively. Better comprehensive performance can be obtained by using HC working fluid.

Evaluating deformation in FRP boat: Effects of manufacturing parameters and working conditions

Abstract Fiber-reinforced plastic (FRP) is utilized in the fabrication of the primary structures of FRP boats. A majority of these structures are produced using molds. Subsequently, these products often experience deformation upon being released from the mold, as well as when they are exposed to high temperatures. Hence, it is crucial to carry out experimental investigations and evaluations related to the deformation of laminated composite structures. The specimens, which are in the form of L-shapes and curve-shapes, are constructed using unsaturated polyester resin and fiberglass material. The study focuses on two independent variables, namely the percentage of hardeners and the temperature during the manufacturing process. The output factor under examination is deformation, which is measured on these specimens. Subsequently, all of the specimens are subjected to varying levels of temperature using an oven as the working condition. The deformation is further assessed based on the experimental findings and regression equation. The results indicate that as the rate of hardener and temperature increase, the level of deformation decreases. Additionally, it was observed that when the temperature rises from 500 to 800°C, the specimens with initial deformation values that are either too high or too low undergo rapid changes. Moreover, the experimental equations can be utilized to predict the values of deformation or input factors.

Numerical study of positive temperature coefficient heating on the lithium-ion battery at low temperature

The performance of lithium-ion batteries may decline at cold temperatures, leading to reduced capacity and electrolyte freezing. To ensure proper operation of energy storage stations in cold regions, heating methods must be designed to maintain batteries at 283.15 K while limiting the temperature difference to less than 5 K. Theoretical analysis and simulation of a battery heating method were conducted using a 22 Ah lithium iron phosphate battery as the research object at 253.15 K. A heating method was designed using Positive Temperature Coefficient (PTC) aluminum plate heaters. Results showed that under the condition of an ambient temperature of 253.15 K and a discharge rate of 1 C, five 120 W PTCs could increase the peak temperature to 283.46 K at 1000 s. The heating method was further optimized by changing the PTC number (2, 3, and 4) and size (corresponding to 120%, 100%, 80%, and 60% of the lithium-ion battery dimensions), and it was found that by using 3 PTC heating plates with 80% size, the maximum temperature could be increased to 289.85 K and the average temperature difference was 4.82 K at 1000 s, meeting the needs of battery operation. The heating method was shown to be effective in rapidly increasing the battery temperature at lower ambient temperatures (243.15, 253.15, and 263.15 K), increasing the rate of temperature increase by 32.4% at 243.15 vs 253.15 K and 45.2% at 263.15 K.

CFD–DEM Simulation of Heat Transfer and Reaction Characteristics of Pyrolysis Process of MSW Heated by High-Temperature Flue Gas

Pyrolysis is a promising disposal method for municipal solid waste (MSW) due to the high-value utilization of the organic components of MSW. Traditional indirect heating has low heat transfer efficiency and requires an increase in the heat exchange area. In this study, a refined numerical simulation model for the pyrolysis of four typical MSW components with high-temperature flue gas was established to study the influence of flue gas on the heat transfer and reaction characteristics of MSW. The temperature distribution and particle size change in different components were obtained, and the effects of flue gas temperature and velocity on the pyrolysis process were analyzed. It was found that the temperature difference of the four components along the bed height direction was about 1.36–1.81 K/mm, and the energy efficiency was about 55–61%. When the four components were uniformly mixed, the temperature increase rates of each component were similar during the pyrolysis process. As the flue gas temperature increased, the amount of gas consumption decreased and the energy efficiency increased. When the flue gas velocity increased, the flue gas consumption increased and the energy efficiency decreased. The research results are of great significance for the promotion and application of pyrolysis technology to MSW with high-temperature flue gas.

Drivers of rising monthly water temperature in river estuaries

AbstractRiver estuaries are habitats for a variety of organisms, including many temperature‐sensitive species; water temperatures in estuaries are affected by several factors as they are influenced by both terrestrial and marine environments. Therefore, understanding the factors that influence river estuaries are essential for environmental management. However, no information exists on temperature change at high temporal resolution and over a wide area; moreover, the relationship with environmental factors has not yet been clarified. Here, we have described the actual status of water temperature change in riverine estuaries and its relationship with environmental factors for a wide area of the Japanese archipelago. Our results indicated that 217 of 294 rivers showed a significant monthly increase in water temperature. The average annual change in rates of water temperature increase was the highest in October at 0.090°C yr−1 and lowest in February at 0.068°C yr−1. Furthermore, snowfall, air temperature increase, sea water temperature, and land use were identified as factors increasing the rate of water temperature increase. Factors influencing the increase in river estuarine water temperature varied from month to month—with meteorological factors being the strongest influencers from spring to fall, and anthropogenic factors in winter. Our findings emphasize the importance of considering not only meteorological and oceanographic phenomena, but also anthropogenic influences and topographic features to understand the pattern of water temperature changes in river estuaries.

Numerical investigation of heat transfer characteristics of supercritical CO2 and water flow in 2D self-affine rough fractures

In recent years, efforts to maximize natural energy utilization have focused on harnessing energy from hot dry rocks (HDR) using supercritical carbon dioxide (SCCO2) or water as the heat transfer fluid. This study aims to enhance comprehension and evaluate the heat extraction performance of enhanced geothermal systems (EGS) by exploring the influence of various inlet velocities and fracture widths on the flow and heat transfer of SCCO2 and water within a rough single fracture in granite. This study utilized a 2D self-affine fractal function to create a rough-fractured rock with fractal properties in a φ50 × 100 mm granite sample. Investigating under 8 MPa conditions, we employed the thermophysical properties of SCCO2 and water to analyze the flow and heat transfer characteristics within the rough rock fractures. The results indicate the following: (1) Higher inlet velocities and wider fracture widths result in a broader temperature reduction range within the surrounding rock matrix for both SCCO2 and water. (2) Increasing the inlet flow velocity of SCCO2 and water leads to wider fracture widths, resulting in lower temperatures at the outlet end of the fracture. As the inlet flow velocity increases from 0.01 m/s to 0.04 m/s, the rate of temperature increase at the outlet can reach up to 19.8 % compared to water. (3) SCCO2, unlike water, exhibits significant reverse vortices at locations where the fracture surface morphology experiences substantial fluctuations. This behavior may be an indirect consequence of SCCO2’s higher velocity, with the direct cause being SCCO2’s lower viscosity and density than water. (4) Among the four conventional fluid thermodynamic parameters, specific heat capacity has the most significant impact on total energy flux rate (TEFR).

Dynamic Constitutive Model and Deformation Mechanism of 2219 Aluminum Alloy Based on the Dynamic Interruption Recovery

Dynamic compression and interruption‐recovery experiments are carried out to investigate the dynamic adiabatic and isothermal deformation behavior of the 2219 aluminum alloy at various strain rates (0.001–5000 s−1). The results of the experiments show that adiabatic temperature increase and strain rates have an impact on the compression behavior of 2219 aluminum alloy. The yield strength is strongly associated with strain rates, demonstrating an evident strain rate hardening effect. The increase in adiabatic temperature is the key factor contributing to the decline in adiabatic strain hardening rate. According to microstructural analysis, the adiabatic shear band is first detected with strain rate of 3200 s−1 along the loading direction. At a strain of 30.3%, cracks begin to appear, and shearing fractures occur with a strain rate of 5000 s−1 in the direction of 45°. Finally, the Johnson–Cook constitutive model is modified with the strain rate reinforcement terms corrected and an adiabatic softening term added to reflect the isothermal and adiabatic compression behaviors. The improved model is better at describing the strain rates affect the behavior of isothermal and adiabatic deformation.

Simulation study to select optimal solid oxide fuel cells heat-up pattern from single, dual co-flow, and dual counter-flow alternatives

ABSTRACT To facilitate power generation, it is necessary to subject solid oxide fuel cells (SOFCs) to a heating process. The introduction of hot gases into the gas flow channels of fuel cells is a widely employed technique for heating purposes. Hot gases can be introduced into one channel (single-channel heating) or two channels (dual-channel heating). Dual-channel heating can have co- and counter-flow patterns. Despite the existence of several heating patterns in the literature, a comparative analysis of these patterns has not been conducted. This study uses a numerical approach to compare various heating patterns, focusing on the objectives of heat-up time, temperature gradient, and energy consumption. The findings indicate that the co-flow pattern demonstrates superior performance in terms of temperature gradient and heat-up time. However, the counter-flow pattern is more favorable in terms of energy consumption. Upon considering all the objectives concurrently through a multi-objective planning approach, the co-flow pattern, characterized by a temperature increase rate of 1 K s−1 and a gas velocity of 10 m s−1, emerges as the most optimal heat-up plan. This particular plan results in a heat-up time of 685 s, a temperature gradient of 337 K cm−1, and an energy consumption of 3856 J.

Thermal Storage Performance of a Shell and Tube Phase Change Heat Storage Unit with Different Thermophysical Parameters of the Phase Change Material

The thermal storage performance of shell and tube phase change heat storage units is greatly influenced by the thermophysical parameters of the phase change material (PCM). Therefore, we use numerical simulations to examine how the thermal storage capability of shell and tube phase change heat storage units is affected by thermophysical parameters such as specific heat capacity, thermal conductivity, and latent heat of phase change. The findings indicate that while the rate of temperature increase and the rate of the PCM melting both slow down as specific heat capacity increases, the overall heat storage increases. Within the specified range of parameters, the average rate of heat storage increases by approximately 4% for every 50% increase in specific heat capacity. The PCM’s rate of temperature rise slows down and its overall heat storage capacity rises throughout the middle stage of the phase change heat storage process as the latent heat of phase change grows. The average heat storage rate increases by approximately 6% and 22% for every 50% increase in latent heat and thermal conductivity, respectively. Notably, when the thermal conductivity is enhanced by a factor of 1.5, the average heat storage rate experiences an almost 50% increase. The thermal conductivity of the PCM has a negligible impact on total heat storage. The choice and use of the PCM in shell and tube phase change heat storage heat exchangers has a theoretical and empirical foundation thanks to this work.

Influence of electrode placement depth on thermal performance of electrically conductive concrete: Significance of threshold voltage for long-term stability

Snow and ice accumulation on pavements pose formidable challenges for transportation agencies in cold regions, resulting in diminished traffic speed, traffic flow, and heightened accident risk during winter. While electrically-conductive concrete (ECON) heated pavement systems (HPS) have emerged as an ecologically-sound and cost-effective snow and ice-removal solution, a lack of identification of critical design parameters for ECON HPS impedes the development of precise design criteria for this technology. This research endeavors to comprehensively elucidate the heating process of electrically-conductive concrete (ECON) slabs and to scrutinize how the depth of electrode placement influences thermal performance. The investigation reveals that the electrode-concrete interface zone serves as the predominant heat source for ECON HPS, and if shallower electrode placement depths are used, the surface temperature increase rate of ECON slabs is enhanced, optimizing cost-effective operation. The study also establishes a threshold voltage level for ECON slabs, beyond which significant changes in electrical properties yield relatively ineffective temperature increase rates. The study found 16 VAC and 425 W/m² to be threshold values for the specific ECON slab system studied. These compelling findings offer valuable insights for future ECON slab design and implementation, ensuring efficient and practical snow-removal applications and benefiting transportation agencies and the broader community.

Features of heat transfer and phase-change on a pinned surface at pulse heat release

An experimental study was conducted of the boiling characteristics of water subcooled to the saturation temperature during pulsed heating on a smooth surface with a technical roughness of up to 5 μm and on a modified surface with cylindrical pins 200 μm in height and diameter, located at the nodes of a rectangular grid with a step of 400 μm, with an upward flow with a pressure of 0.29 MPa and an average flow velocity of 0.52 m/s. It was found that at an initial water temperature of 110°C for a modified surface, the rate of increase in the heater temperature is lower, and the onset time of nucleation is the same as for a smooth surface. For an initial water temperature of 80°C and an average temperature increase rate of about 5000 K/s, it was experimentally shown that the bubbles on the modified surface are larger, but their number and the share of the area occupied by them are significantly lower than on a smooth surface.

Experimental Study on Effect of Temperature Characteristics on Upper Rack According to Type and Arrangement of Combustibles in Logistics Facilities

As part of a study to establish a performance-based fire-response design and evaluation method for logistics facilities, an experimental rack was manufactured, and the temperatures at the top of the combustible material during a rack fire were measured. The temperature time and temperature flame length relationships were established. Based on the variation in – – temperature with the arrangement of the combustibles, the rate of increase in heat flow through the vertical flue was higher when the combustibles were doubled than when they were single, indicating that the increased rate of the flame and flume was more than twice that of a single combustible. Based on the type of combustible, CEP exhibited a significantly higher rate of temperature increase than CUP. In the case of the CUP, when arranged in one stage and one row, the fire intensity was weak in the early stage of the fire; therefore, it was possible that the upper sprinkler head did not respond. In addition, the correlation between the flame length and temperature during the initial fire was relatively high (R<sup>2</sup> = 0.93).

Observational study of peripheral skin temperature changes following spinal anaesthesia for caesarean birth

BackgroundSpinal anaesthesia is widely used in obstetric anaesthesia practice but there is limited knowledge about the development of sympathetic blockade following spinal anaesthesia for caesarean birth. This study investigated the characteristics of sympathetic blockade by measuring peripheral skin temperature changes in the feet of patients given spinal anaesthesia for elective caesarean birth. MethodsA prospective observational study was conducted involving 60 eligible parturients scheduled for elective caesarean birth with spinal anaesthesia. Skin temperature probes were attached to the dorsum of both feet, and temperature measurements were recorded every minute. The dose of spinal anaesthesia given, and other relevant patient data, were collected. ResultsAll participants had successful spinal anaesthesia. Following spinal anaesthesia, a sustained rise in skin temperature of both feet was observed, indicating the presence of sympathetic blockade. The maximum rate of temperature increase occurred between 6 and 15 min after the intrathecal injection and plateaued from 22 min after the injection. Control participants did not show any changes in foot temperature. ConclusionsThis study demonstrates that successful spinal anaesthesia for caesarean birth results in a consistent and reliable rise in skin temperature of the feet that is evident after six minutes from intrathecal injection. The observed temperature changes provide indirect objective evidence of bilateral sympathetic blockade. Measurement of feet skin temperatures may serve as an additional objective indicator of successful spinal anaesthesia, along with tests of lower limb motor block and sensory block height. These findings contribute to the understanding of sympathetic blockade during spinal anaesthesia.

Analysis of Factors Affecting the Preparation of Mullite Whiskers from Silica-Rich Slag and Application Studies.

This paper presents an in-depth comparative study of the effects of different molten salt systems, catalyst additions, preparation temperatures, temperature rise rates, and holding times on the properties of mullite whiskers during their preparation process, as well as exploring the enhancement of the toughening effect of mullite whiskers on ceramics. The morphology, crystal structure, and composition of the whiskers were analyzed via SEM, XRD, TG, strength tests, etc. The results show that the best-performing mullite whisker was prepared with an aluminum sulfate molten salt system, with the addition of aluminum fluoride catalyst at 4%, a temperature increase rate of 5 °C, a temperature increase up to 850 °C, and a holding time of 5 h, and its aspect ratio reached 20.64. By adding different contents of mullite whiskers and comparing the toughness strengths and wear rates of the silicon carbide ceramics, it was found that the toughness strength of the ceramics was improved by more than 16.5% and the wear rate was lower than 0.4% when the addition of mullite whisker was more than 3%.

Research on the Improvement of Lithium-Ion Battery Performance at Low Temperatures Based on Electromagnetic Induction Heating Technology

As the major power source for electric vehicles (EVs), lithium-ion batteries (LiBs) suffer from the degradation of technical performance and safety at low temperatures, which restricts the popularization of EVs in frigid regions. Thus, this study developed an extremely fast electromagnetic induction heating system in order to improve the poor performance of LiBs in cold weather. An electrochemical–thermal coupling model (ETCM), validated against the experimental results of charge and discharge, which successfully predicted LiB voltage, temperature, and other physical characteristics at various ambient temperatures, was established in COMSOL Multiphysics 6.0 as a development tool for evaluating the heating effect of the system. When the copper coil is subjected to a SAC (sinusoidal alternating current) of 8 A and 50 Hz, the LiB can be heated from 243.15 to 293.15 K within 6 min with an instantaneous temperature increase rate of 0.263 K/s and a homogeneous temperature distribution. The results of the capacity calibration, cyclable lithium detection, and HPPC simulation show that the heating method can visibly increase the Li+ concentration inside the active particle, and there was only a tiny concentration gradient on the surface of the particle. In addition, the internal resistance was approximately a quarter of that without heating; therefore, both the discharge energy and specific power boost were two times higher than the original level. Compared to the normal charge–discharge cycles at 293.15 K, the capacity retention of the LiB only decreased by 0.23% after 60 consecutive heating cycles, so the heating method can balance the temperature rise, work capacity, and LiB health. Furthermore, the improvements in the thermal insulation condition and material thermal conductivity are two feasible ways to optimize the temperature-increase effect.

Thermal Tolerance of Spotted Sea Bass (Lateolabrax maculatus) and Pearl Gentian Grouper (Epinephelus fuscoguttatus Female × E. lanceolatus Male) in Different Environmental Temperatures

Seawater cooling is the most common way to cool down nuclear power plants. However, the thermal drainage of nuclear power plants results in sharp rises in local seawater temperatures and, therefore, affects fisheries and ecologies. Therefore, evaluating the thermal tolerance of marine organisms not only provides further insight into their biological characteristics but also holds significant importance for the site selection and construction of nuclear power plants. This study investigated the thermal tolerance of spotted sea bass (Lateolabrax maculatus) and pearl gentian grouper (Epinephelus fuscoguttatus female × E. lanceolatus male) using the critical thermal maximum method. The environmental temperatures for spotted sea bass and grouper in spring, summer, autumn, and winter were 21.6/23 °C, 26.5/25.9 °C, 25.0/25.9 °C, and 14.5/16.6 °C, respectively. Under four seasonal conditions, different temperature rise rates of +2 °C, +4 °C, +6 °C, and +8 °C per hour were set. The maximum critical temperature, initial lethal temperature, absolute lethal temperature, and semi-lethal temperature were recorded for both fish species. The results show that the rates of temperature increase did not affect the thermal tolerance of either fish species. In all seasons, the fish experienced rapid death once they reached the initial lethal temperature. However, there was a significant correlation of season with thermal tolerance in both fish species. For spotted sea bass, the semi-lethal temperature in summer reached about 40 °C, while in winter it was about 35 °C. For pearl gentian grouper, the semi-lethal temperature in summer reached about 40 °C, while in winter, it was about 38 °C. These results remind us that these two fish species have a limited ability to adapt to rapid temperature rises, but appropriate acclimation temperatures can effectively improve their thermal tolerance. Therefore, it is necessary to further consider the potential impacts on these fish species during the site selection and construction process of nuclear power plants.

Risk Assessment of Freezing–Thawing Hazards in the Daxing’anling Forest Region

The Daxing’anling forest region represents a crucial forestry hub in China and confronts some of the nation’s most severe freezing–thawing hazards. This study delved into the temporal trends and spatial distributions of various parameters related to freezing and thawing, including air temperature, ground surface temperature, freezing index, thawing index, and freezing–thawing frequency. Furthermore, this study assessed and delineated freezing–thawing hazards within the research area. The findings revealed a rapid increase in air temperature and ground surface temperature within the Daxing’anling forest region yet a lower rate of increase in ground surface temperature compared to Northeast China. Latitude had the strongest influence on mean annual air temperature, mean annual ground surface temperature, air freezing index, air thawing index, ground surface freezing index, ground surface thawing index, air freezing–thawing frequency, and ground surface freezing–thawing frequency, followed by longitude and elevation. Overall, freezing index, and air freezing–thawing frequency increased from south to north, whereas mean annual air temperature, mean annual ground surface temperature, air thawing index, ground surface thawing index, and ground surface freezing–thawing frequency decreased from south to north. The assessment outcomes underscore the importance of closely monitoring freezing–thawing hazards in regions north of the 50th parallel.

Investigation on coal/coal gangue mixtures co-combustion via TG-DSC tests, multicomponent reaction model, and artificial neural network

Coal gangue (CG) is the main hazardous solid waste produced during coal mining activities; it increases the combustion risk of coal/coal gangue (C/CG) mixtures. In the present work, the combustion characteristics, interactions, combustion reaction model, and kinetic parameters of C/CG co-combustion were investigated under seven different mixing ratios. Thermogravimetric data revealed that the mixture of 70 % coal and 30 % CG exhibited the most strongest synergistic effect and heat release capability, whereas that with 30 % coal and 70 % CG showed the most strongest inhibitory effect. Additionally, a multicomponent combustion reaction model for coal/CG mixture co-combustion was established. We found that the three-component combustion reaction model could appropriately describe the combustion process of C/CG mixtures. Furthermore, as the CG ratio increased to 90 %, the reaction participation of volatile and inorganic matter gradually increased, whereas that of organic matter gradually decreased. The impact of CG content on the activation energy of the reaction system depends on the conversion rate. Finally, the temperature-increasing rate, mixing ratio, and finishing temperature were considered as the import data, artificial neural network (ANN) prediction was performed based on the thermogravimetric data, results show ANN-42 (3 × 9 × 17 × 1) model was the most appropriate for predicting the co-combustion of coal/CG mixtures.

Flexible multiwalled carbon nanotubes/cellulose nanofibers membrane with rapid temperature increasing induced by interface strengthening

Towards advanced electrical heaters with superior Joule heating property, high electrical conductivity has always been critical issue. Herein, in addition to the commonly recognized factor of electrical conductivity, we proved that the composite interface poses significant effect on temperature increasing as electrical heaters. Specifically, direct fluorination utilizing F2/N2 was applied to selectively decorate the outer walls of multiwalled carbon nanotubes (MWCNTs) while keeping the inner tube intact, which was followed by compositing it with cellulose nanofibers (CNFs) to prepare F-MWCNTs/CNFs flexible membrane. Due to the enhanced electrostatic interaction at the interface and stronger phonon vibrational coupling, interfacial phonon diffusion was significantly improved, which facilitated a higher temperature increase rate in the F-MWCNTs/CNFs membrane compared to the unmodified MWCNTs/CNFs membrane when subjected to an electric field. This unique interfacial effect holds promise for the development of high-performance electrical heaters with rapid response.

Effect of temperature-rising inhibitor on the hydration and performance of cemented paste-filling material

The addition of a temperature-rising inhibitor (TRI) to aeolian sand paste materials (ASPM) to produce paste-like filling mining materials can solve multiple problems. First, it may alleviate the environmental problems caused by solid waste treatment in mines to achieve sustainable use of solid waste. Second, It may solve the problem of rapid temperature rise in mines caused by the rapid heat release during filling body hydration. Therefore, this study explored the hydration of an ASPM with different TRI contents and its mechanical properties, setting time, and microstructure. The results show that at TRI contents of 0–1.0%, the peak heat-release rate of the ASPM is reduced by 16.0%, the early hydration heat release is reduced by 14.2%, and the delay of the heat-release peak is more prominent. TRI inhibits the hydration of ASPM primarily within 7 d, which reduces the early strength of the ASPM by a maximum of 43.4%. However, with the increase in age, the strength difference gradually decreases, and TRI even becomes beneficial for the development of strength in later stages. In addition, the high content of TRI has a significant retarding effect on ASPM hydration. The temperature rise test shows that TRI can reduce the temperature increase rate and delay the peak temperature increase rate, which can effectively solve the problem of concentrated heat release by backfill. This paper provides a theoretical basis for the application of TRIs in cemented paste backfill.