Increase In Final Temperature Research Articles

Influence of the foam-fin structure on the thermal performance of a coupled phase change liquid cooling module

Effective thermal management is key to ensuring the reliable operation of high power electronic equipment. In this study, the strategy of phase transition and liquid cooling coupling applied to transient high power electronic equipment has been examined. In order to improve the performance of the phase changing material (PCM) in temperature control, the effects of the coupling structure have been addressed with a consideration of fin, copper foam (CF), graphite foam (GF), fin-copper foam (FCF) and fin-graphite foam (FGF) structures in heat dissipation. In this study, pure paraffin wax (PPW) was used as phase change material to prepare heat sinks based on the above five structures. The experimental study investigates the impact of different thermal conductivity strategies on temperature control characteristics, with a focus on cold capacity recovery and the combined phase change and liquid cooling, using pure paraffin wax module as a reference. The results have revealed that the fin-foam coupling structure delivers a better PCM performance than the single fin or foam structure. Operating at a heating power of 10 W, 15 W and 20 W, the temperature control time of the FGF structure was increased by 13.6 %∼14.6 % relative to the GF structure. At 15 °C with flow rates of 1 L/min, 1.5 L/min, 2 L/min liquid cooling conditions, the cooling capacity recovery time was reduced by 18.8 %, 17.2 %, 19.7 %, respectively. In the phase-change liquid-cooling coupling temperature control experiment, the final temperature increase in the FGF system was 11.7 °C -15.2 °C lower than that of the GF system under the same water temperature and volume flow for a 50 W heat source. The incorporation of fins also enhanced the thermal conductivity strengthening capability of the copper foam and reduced the cold recovery time. Based on the comprehensive evaluation, the FGF structure demonstrates superior temperature control performance and cold recovery characteristics of PCM, making it an optimal strengthening method. Following closely are the FCF, GF, Fin and CF structures. Compared to pure paraffin modules, these five modules exhibit varying degrees of improvement in temperature control and cold capacity recovery efficiency. This study provides guidance for optimizing heat sink design based on PCM in electronic applications.

Comparative study of the composition and microstructural properties of semi-coke from microwave and conventional pyrolysis of low rank coal

Microwave pyrolysis technology can effectively realize the clean and quality improvement of coal. In order to study the changes of each component of coal in the process of microwave pyrolysis, the d002, La, Lc, combustion reactivity and conductivity of semi-coke after pyrolysis were analyzed by using XRD, TG, conductivity meter and other testing instruments, and the infrared spectra of semi-coke after pyrolysis were finely resolved by using Origin peak-splitting technique, and the composition of the coal gas in the process of pyrolysis and its percentage content were analyzed. The composition and percentage content of gas in the pyrolysis process were analyzed and compared with conventional pyrolysis. The results showed that compared with conventional pyrolysis, microwave pyrolysis can be completed at a lower temperature and microwave pyrolysis is more favorable to the release of volatile components, in which the content of CO and H2 in the gas fraction increased significantly compared with conventional pyrolysis. At the same pyrolysis temperature, the microwave semi-coke has a higher maximum combustion rate temperature than the conventional semi-coke, which is conducive to improving the thermal stability of semi-coke. The orderliness of the semi-coke increased with the increase of pyrolysis final temperature, resulting in the phenomenon of "similar graphitization". The increase in the number of carbon microcrystalline structures generates off-domain electrons, leading to a significant increase in conductivity. Meanwhile, FT-IR peak fitting analysis revealed that the R value inflection point temperature of microwave semi-coke was much lower than that of conventional semi-coke, which further proved that microwave pyrolysis could be accomplished at lower temperatures, and the C value showed a decreasing tendency with the increase of the final temperature of pyrolysis, which indicated that pyrolysis was an effective method to improve the quality of coal. The above analysis shows that compared with conventional pyrolysis, microwave can prepare high stability and high conductivity semi-coke at lower temperature.

Quantifying tissue temperature changes induced by infrared neural stimulation: numerical simulation and MR thermometry.

Infrared neural stimulation (INS) delivered via short pulse trains is an innovative tool that has potential for us use for studying brain function and circuitry, brain machine interface, and clinical use. The prevailing mechanism for INS involves the conversion of light energy into thermal transients, leading to neuronal membrane depolarization. Due to the potential risks of thermal damage, it is crucial to ensure that the resulting local temperature increases are within non-damaging limits for brain tissues. Previous studies have estimated damage thresholds using histological methods and have modeled thermal effects based on peripheral nerves. However, additional quantitative measurements and modeling studies are needed for the central nervous system. Here, we performed 7 T MRI thermometry on ex vivo rat brains following the delivery of infrared pulse trains at five different intensities from 0.1-1.0 J/cm2 (each pulse train 1,875 nm, 25 us/pulse, 200 Hz, 0.5 s duration, delivered through 200 µm fiber). Additionally, we utilized the General BioHeat Transfer Model (GBHTM) to simulate local temperature changes in perfused brain tissues while delivering these laser energies to tissue (with optical parameters of human skin) via three different sizes of optical fibers at five energy intensities. The simulation results clearly demonstrate that a 0.5 second INS pulse train induces an increase followed by an immediate drop in temperature at stimulation offset. The delivery of multiple pulse trains with 2.5 s interstimulus interval (ISI) leads to rising temperatures that plateau. Both thermometry and modeling results show that, using parameters that are commonly used in biological applications (200 µm diameter fiber, 0.1-1.0 J/cm2), the final temperature increase at the end of the 60 sec stimuli duration does not exceed 1°C with stimulation values of 0.1-0.5 J/cm2 and does not exceed 2°C with stimulation values of up to 1.0 J/cm2. Thus, the maximum temperature rise is consistent with the thermal damage threshold reported in previous studies. This study provides a quantitative evaluation of the temperature changes induced by INS, suggesting that existing practices pose minimal major safety concerns for biological tissues.

Multi-centennial evolution of the climate response and deep-ocean heat uptake in a set of abrupt stabilization scenarios with EC-Earth3

Abstract. Understanding long-term committed climate change due to anthropogenic forcing is key to informing climate policies, yet these timescales are still underexplored. We present here a set of 1000-year-long abrupt stabilization simulations performed with EC-Earth3. Each simulation follows a sudden stabilization of the external forcing at the level specified by CMIP6 for historical (1990) or SSP5-8.5 scenario (2025, 2050, 2065, 2080, 2100) conditions, with a final temperature increase ranging between 1.4 and 9.6 K with respect to the pre-industrial baseline. Remarkably, the simulation stabilized at a greenhouse gas (GHG) level close to the present day (2025) exceeds the Paris Agreement goals of 1.5 and 2° warming above pre-industrial in the long term, and only the 1990 simulation leads to a stabilized climate below 1.5° warming. We first focus on the evolution of the climate response at multi-centennial timescales and its dependence on the level of forcing. We note a decrease in the magnitude of the climate feedback parameter at longer timescales. Conversely, simulations with higher forcing exhibit a larger feedback parameter (in magnitude). Subsequently, the evolution of surface warming patterns over multi-centennial timescales is studied. While the response is generally consistent across simulations, some variations, particularly in the South Pacific and at high latitudes, suggest a certain level of state or forcing dependence. The patterns of precipitation change also evolve during the stabilization runs: the drying trends found in the subtropical oceans and in Mediterranean-like hotspots in the SSP5-8.5 scenario tend to be reduced or even reversed. We finally focus on the rate of heat storage in the global ocean, which is the main driver of the climate response at multi-centennial timescales. We find that the rate of warming of the deep ocean is almost independent from the amplitude of the forcing so that most of the additional heat remains in the upper layers at high forcing. This might be due – at least partly – to a decreased ventilation of the deep ocean, caused by changes in the Meridional Overturning Circulation (MOC). These results highlight the importance of studying multi-centennial timescales of climate change to better understand the response of the deep ocean, which will play a crucial role in determining the final state of the climate system once GHG concentrations are stabilized.

Effect of final pyrolysis temperature on the composition and structure of shale oil: Synergistic use of multiple analysis and testing methods

As the focus of research on the pyrolysis mechanism of oil shale shifting towards the molecular level, identifying the effect of pyrolysis temperature on the molecular composition and structure becomes all the more important. In this study, the molecular characteristics of shale oils produced at different final pyrolysis temperatures was compared and analyzed through synergistic use of multiple analysis and testing methods. The results showed that compared with the traditional gas chromatography-mass spectrometry (GC-MS), comprehensive two-dimensional gas chromatography-time of flight mass spectrometry (GC × GC-TOF/MS) has obvious advantages in the characterization of heteroatoms and cycloalkanes. Fourier transform infrared spectrometry (FT-IR) can supplement the deficiency of nuclear magnetic resonance (NMR) in the characterization of oxygen-containing functional groups. With the increase in final temperature, the aromatization reaction of cycloalkanes intensified. Conversely, the degree of alkane branching and carbon chain length decreased. Based upon mutual verification and supplement of various analysis results, a novel method was proposed for the comprehensive molecular characterization of complex liquid fuel oil. According to the advantages and characteristics of different detection methods, synergistic use of multiple methods for different fractions is an important research direction for the molecular characterization of complex liquid fuel oil in the future.

Hydrothermal Treatment of Herb Residue for Solid Fuel Production

Hydrothermal processing is appraised as one of advanced technologies for wet solid waste handling. In this study, herb residue was subjected to hydrothermal treatment. Calorific value, yield, and also proximate analysis of obtained hydro-char were investigated. A cylindrical reactor with an internal volume of 2.5 Litres made of stainless steel and a low-tech component was used in the experiment. The reactor was equipped with a stirrer to ensure heat transfer took place through the entire parts of the solid-water mixture. Solid products were dried by a microwave oven before analysis. The results show that the final temperature, holding time, and solid-water ratio have various effects on the hydro-char yield, calorific value, and proximate analysis of the hydrothermal products. The hydro-char yield decreased with the increase in final temperature and holding time. Meanwhile, the highest hydro-char yield was obtained at the solid-water ratio of ¼. The hydro-char calorific value increased with the increase in final temperature, holding time, and solid-water ratio. The rise in final temperature, holding time, and solid-water ratio resulted in a lower moisture content and volatile matter but higher fixed carbon. Meanwhile, the ash content increased with the solid-to-water ratio.

Thermal safety study of Li‐ion batteries under limited overcharge abuse based on coupled electrochemical‐thermal model

Many fire accidents of electric vehicles were reported that happened during the charging process. In order to investigate the reasons that lead to this problem, this paper studies the thermal safety of Li-ion batteries under limited overcharge abuse. A 3D electrochemical-thermal coupled model is developed for modeling thermal and electrochemical characteristics from normal charge to early overcharge state. This model is validated by experiment at charge rates of 0.5C, 1C, and 2C. The simulation results indicate that irreversible heat contributes most to temperature rise during the normal charge process, but the heat induced by Mn dissolution and Li deposition gradually dominates heat generation in the early overcharge period. Based on this, a threshold selection method for multistage warning of batteries overcharge is proposed. Among them, level 1 should be considered as a critical stage during the early overcharge process due to the deposited lithium starts to react with electrolyte at the end of level 1, where temperature rate increases to 0.5°C min−1 for 1C charge. While the thresholds of levels depend on charge rate and composition of battery. Furthermore, several critical parameters are analyzed to figure out their effects on thermal safety. It is found that the temperature at the end of overcharge is significantly influenced by the change of positive electrode thickness and solid electrolyte interface (SEI) film resistance. The final temperature increases by 17.5°C and 7.9°C, respectively, with positive electrode thickness ranging from 50 to 80 μm and SEI film resistance increasing from 0.002 to 0.03 Ω.

Hydrogen-rich gas production from soybean straw via microwave pyrolysis under CO2 atmosphere

ABSTRACT The experiments on microwave pyrolysis of soybean straw are studied to produce hydrogen-rich gas under CO2 atmosphere in this paper. The microwave power has an important effect on the temperature. The final temperature increases and the time to obtain the highest temperature is shortened with the power increasing. The gas yield, H2 yield and potential H2 yield increase rapidly with the power increasing, and the gaseous yield at CO2 atmosphere is up to 55.70% at 1000 W, and it is higher than N2 atmosphere. The main components of microwave pyrolysis gas product are H2 and CO, the content of syngas (H2+ CO) at CO2 atmosphere is 84.19% at 1000 W, which is more than N2 atmosphere. However, H2/CO ratio is about 0.80 at CO2 atmosphere, which is lower than N2 atmosphere, and H2/CO ratio at CO2 atmosphere is not suitable for the requirements of chemical synthesis. If it is used to synthesize liquid fuels, H2/CO ratio must be adjusted.

Thermal comparison of heavy vehicle wheel assemblies under alpine braking

Overheating brakes cause brake fade, tyre blowouts and vehicle fires, but no study has investigated the influence of wheel configuration or rim material on these catastrophic failures. Laboratory measurements of the transient thermal response of heavy vehicle wheel assemblies to [Formula: see text] of alpine friction braking are presented; comparing brake and tyre temperature when using dual and single wheels with steel and aluminium rims. Under an averaged braking power of [Formula: see text], the final temperature increase of the brake was [Formula: see text] (3.7%) higher when using steel versus aluminium rims. The final increase in maximum tyre temperature was [Formula: see text] (16%) higher when using aluminium versus steel rims and [Formula: see text] (76%) higher when using single versus dual wheels. The greater thermal conductivity and cross-sectional area of the aluminium rims relative to the steel rims reduce the thermal resistance of braking heat flowing into the tyre; leading to higher tyre temperature when using aluminium rims. Dual rims and tyres have larger surface areas than singles which convect more heat to the air at lower temperatures; leading to cooler tyres when using dual wheels. The higher thermal diffusivity of aluminium and lower thermal capacities of single wheels also cause tyre temperature to rise more rapidly than when using steel rims or dual wheels. These results indicate that the risk of tyres overheating (which could lead to blowout) from extended use of the brakes is increased when using single wheels compared to dual wheels and further exacerbated by using aluminium rims compared to steel rims.

Effect of Low-Temperature Pyrolysis of Shenfu Long-Flame Coal on Caking Properties of Coking Coal

Pyrolysis of Shenfu long-flame coal at low temperature has been carried out in a tubular furnace to reduce the influence of the addition of non-caking coal on the caking property of coking coal. The influence of low temperature pyrolysis on the chemical composition and microstructure of Shenfu long-flame coal has been studied. Finally, the effect of low-temperature pyrolysis on the relative Giseeler fluidity and caking index has been investigated by mixing the Shenfu long-flame coal with Taozhuang fat coal in a certain proportion. The experimental results show that the active component content of Shenfu long-flame coal is slightly lower, while the inert component content increases slightly after low-temperature pyrolysis. The maximum mean reflectivity of Shenfu long-flame coal vitrinite group increases with the increase of final temperature of pyrolysis. The surface of long-flame coal tends to be dense and smooth, and the crystal structure of the Shenfu long-flame coal gradually changes to graphite crystal structure. Compared with the simple addition of long-flame coal to coking coal, adding long-flame coal after low-temperature pyrolysis can alleviate the weakening effect of adding non-cohesive material on the caking property of coking coal and therefore improve the quality of coke.

Effects of Radio Frequency Heating Treatment on Structure Changes of Soy Protein Isolate for Protein Modification

The effects of radio frequency (RF) heating treatments with different final temperatures (70, 80, and 90 °C) and electrode gaps (120, 160, and 200 mm) on the structural characteristics of soy protein isolate (SPI) dispersion were investigated. The results showed that RF heating significantly influenced free sulfhydryl groups and surface hydrophobicity of SPI. Free sulfhydryl groups increased with the increase of final temperature. The hydrophobicity of the RF-heated sample was higher than the original SPI without RF treatment. The highest hydrophobicity of the RF-heated SPI was found with electrode gap of 200 mm at 90 °C. RF heating treatment resulted in the reduction of ultraviolet absorption of SPI indicating the change of three-dimensional positions of soy protein but did not modify the protein primary structure of SPI. The Fourier transform infrared spectroscopy showed that hydration of SPI was decreased by RF heating. The self-reassembly from random coil structure to β-sheet structure suggested that RF heating treatment can change the secondary structure of soy protein to be more orderly.

Analytical investigation of process pipe failure in cryo-line; impact of different crack sizes

Safety is important in cryogenic field dealing with liquid or supercritical state helium. Cryolines carrying helium at 4 K temperature level and equipped with thermal compensation devices, like bellows, are prone todevelopment of cracksand its propagation after a number of expansion and contraction. Even after careful design, appropriate material selection and a strict quality control during manufacturing, probability of crack development in the Cryo-line cannot be avoided. An investigative study of failure of process pipe due to the development of crack has been carried out for a long Cryo-line laid in a confined space considering the space between two vacuum barriers is 10 meter. Study shows that minimum temperature of the Outer Vacuum Jacket (OVJ)goes down to 251 K in 540th second andthe minimum temperature of the confined space reaches to 73 K in 37th second. As the crack size reduces, the OVJ pipe temperature approaches to the minimum value in longer time and confined space final temperature increases.

Study on the Pyrolysis Kinetics of HCl-Pretreated Soybean Stalk

To study the influences of the acid-washing on the characteristics of soybean stalk pyrolysis , and search the high-efficiency catalyst for biomass pyrolysis, pyrolysis experiments of soybean stalk pretreated by 0.1mol/L HCl acid solution were performed by nonisothermal thermogravimetric analysis (TGA) at five different heating rates. The results showed the pyrolysis process of HCl-washed soybean stalk can be separated into four stages (water loss, depolymeri-zation and vitrification, thermal decomposition, and carbonization). At the same heating rate, the maximum pyrolysis rate of HCl-washed is larger than untreated soybean stalk, but the corresponding temperature is higher. All the DTG (differential thermogravimetric) curveas appear a smaller shoulder peak respectively. With the heating rate increasing, the main pyrolysis zone of the TG (thermogravimetric) and DTG curves move to the high-temperature direction, and the maximum pyrolysis rate and its corresponding temperature increase too. HCl-wahsed makes the weight loss rate of the final temperature increase 5% approximately. The value area of activation energy of the main pyrolysis area is 140.19~174.59 kJ/mol calculated by the method of Ozawa. The Šatava method inferred the most possible mechanism function of HCl-wahsed soybean stalk is Zhuralev-Lesakin-Tempelman equation, which is three-dimensional diffusion.

Study on the Pore Structure of Oil Shale During Low-Temperature Pyrolysis

In this research, effects of final pyrolysis temperature and heating rates on the pore structure of Huadian oil shale were investigated experimentally. The pore structure of raw and semi-coke samples was measured by the method of low-temperature adsorption of nitrogen. The obtained adsorption/desorption isotherms of these samples were similar and could be categorized as type II isotherms in the IUPAC classification, and all hysteresis loops produced by OS and all semi-cokes are very similar to H3 hysteresis loops. Specific surface area was calculated based on BET equation, and specific surface area distribution and pore size distribution were calculated by BJH method. The analysis results show that final temperature and heating rate are all parameters that influence specific surface area, specific pore volume and the development of mesopores. With the final temperature increase, specific surface and total pore volume initially decrease, then increase in large scale. Meanwhile the peak near 3nm on specific surface area and pore size distribution curves is gradually disappearing, then arise sharply. Lower heating rate favors the development of pores, especially 3nm mesopores. With heating rate increase, specific surface area and total pore volume decrease, and the peak value on specific surface distribution and pore size distribution curves gradually decrease.

Joint posture, volumetric and temperature changes during repetitive hand movements

The study assessed finger and wrist joint motion, temperature and volumetric measurements and reports a qualitative assessment resulting from repetitive industrial hand movements. Participants mimicked a series of industrial repetitive tasks incorporating the following hand movements: wrist flexion/extension task, repetitive grasp/release task; and pinch task. Each task was performed for a period of 5 minutes. Hand temperature and volumetric measurements were reported. Descriptive statistics and ANOVA were performed. Power analysis was performed to determine sample size (0.8) and significance was set at p=0.05. The results indicate that an increase in hand volume is accompanied by an increase in final temperature of the hand. Of the three tasks mimicking an industrial repetitive activity, the repetitive grasp/release task produced the most range of motion (RoM), followed by the wrist flexion/extension task and then the pinch task. From the subjects' perception the wrist flexion/extension task was considered to be the most stressful task.

Effects of Temperature and Heating Rate on the Precipitation of 3C-SiC Islands on 4H-SiC(0001) from a Liquid Phase

Like on 6H-SiC substrates, 3C-SiC islands precipitation was found to be the initial stage of the VLS growth of 3C-SiC layers on 4H-SiC surfaces. This precipitation happens between 1100 and 1200°C with a heating rate of 2.8°C.s-1, without addition of propane. The islands size increases in a similar manner whether the final temperature increases (for a given heating rate) or the heating rate decreases (for a given final temperature). This enlargement can give rise to a complete cubic layer for the highest temperatures or the slowest heating rates. It is suggested that the carbon atoms involved in the enlargement process (after the nucleation) come from the graphite crucible.

Reconstructing P–T paths during continental collision using multi‐stage garnet (Gran Paradiso nappe, Western Alps)

AbstractGarnet–chloritoid‐bearing micaschists from the Gran Paradiso massif (Western Alps) contain evidence of a polymetamorphic evolution. Detailed textural observations reveal that two stages of garnet growth are present in the micaschists, interpreted as: (i) relics of an early metamorphism of pre‐Alpine age and (ii) newly grown Alpine garnet, respectively. Both generations of garnet preserve growth zoning. From thermocalc‐based numerical modelling of mineral assemblages in pressure–temperature (P–T) pseudosections, we infer that garnet 1 grew at increasing temperature and slightly increasing pressure, whereas garnet 2 grew at decreasing pressure and slightly increasing temperature. Estimated P–T conditions are ∼620 °C, 6 kbar for the peak of the pre‐Alpine event, and of 490 °C, 18–20 kbar for the pressure peak of the Alpine event. Modelling of the modal proportion and chemical composition of garnet (i) shows that the subsequent decompression (to 14–15 kbar at 550 °C) must have been accompanied by moderate heating and (ii) does not support a stage of final temperature increase following decompressional cooling. This argues against a late thermal pulse associated with mantle delamination. Preservation of growth zoning in both generations of garnet and the limited amount of diffusive re‐equilibration at the boundary between the two garnets suggests that the rocks were subjected to fast burial and exhumation rates, consistent with data obtained from other internal Alpine units.

Main trends in rectal temperature during sleep. Hypnogram and thermogram.

Changes in sleep state and night-time body temperature were studied in 13 healthy young men. Temperature data showed serial dependence that was removed when considering three main segments of the thermogram: an initial rapid drop between 60 and 140 min after lights off, followed by a slower decrease to the thermal minimum and a final temperature increase until waking. The first segment was fitted by a two-term function, while the other two segments were fitted by linear regression. Temperature data obtained after fitting these models were stationary and used to calculate the fast Fourier transformation and the cross-correlation functions between the hypnogram and the thermogram of each subject. Attaining stationarity has unmasked short oscillations during sleep and some temperature series showed the presence of ultradian oscillations with a period of 90-100 min. Significant cross-correlations between sleep stages and body temperature were found, and the parameters of the two-term function fitted to the first temperature drop were related to the sign of the correlation and to that time series (sleep or temperature) which preceded the other during the night.