High Temperature Heat Research Articles

Study on the High Temperature Heat Treatment Process Optimization of Different Sizes High Jc Nb$_{\text{3}}$Sn Wire Produced by WST

Study on the High Temperature Heat Treatment Process Optimization of Different Sizes High Jc Nb$_{\text{3}}$Sn Wire Produced by WST

Enhanced Heat Transfer in Thermoelectric Generator Heat Exchanger for Sustainable Cold Chain Logistics: Entropy and Exergy Analysis

This study investigates the application of thermoelectric power generation devices in conjunction with cold chain logistics transport vehicles, focusing on their efficiency and performance. Our experimental results highlight the impact of thermoelectric module characteristics, such as thermal conductivity and the filling thickness of copper foam, on the energy utilization efficiency of the system. The specific experimental setup involved a simulated logistics cold chain transport vehicle exhaust waste heat recovery thermoelectric power generation system, consisting of a high-temperature exhaust heat exchanger channel and two side cooling water tanks. Thermoelectric modules (TEMs) were installed between the heat exchanger and the water tanks to use the temperature difference and convert heat energy into electrical energy. The analysis demonstrates that using high-performance thermoelectric modules with a lower thermal conductivity results in better utilization of the temperature difference for power generation. Additionally, the insertion of porous metal copper foam within the heat exchanger channel enhances convective heat transfer, leading to an improved performance. Furthermore, the study examines the concepts of exergy and entropy generation, providing insights into the system energy conversion processes and efficiency. Overall, this research offers valuable insights for optimizing the design and operation of thermoelectric generators in cold chain logistics transport vehicles to enhance energy utilization and sustainability.

The effect of the iso‐thermal heat treatment on the microstructure and properties of powder bed fusion‐laser beam AlSi10Mg alloy

The effect of various iso‐thermal heat treatments on powder bed fusion‐laser beam (PBF‐LB) AlSi10Mg alloy has been widely studied; however, a process‐property relationship has not yet been established. In addition, the eutectic Al‐Si network breakdown and coarsening of eutectic Si from low‐to high (200oC–500oC) temperature heat treatment has not been investigated systematically. Therefore, the AlSi10Mg alloy is heat‐treated at 200oC, 300oC, 400oC, and 500oC for various holding times ranging from 0.5 to 32 hours. Uniaxial tensile and hardness tests are conducted, and the microstructure is characterised in detail. A unique approach is adopted for estimating Si solubility where 200oC heat‐treated microstructure data is used to estimate solute trapping due to the high cooling rate in the as‐fabricated state. Furthermore, it was observed that increasing the heat treatment temperature and time reduces the strength and strain hardening rate but increases the tensile elongation up to 400oC heat treatment. Above 500oC, the yield strength increases, and the elongation reduces compared with the 400oC heat treatment owing to the refined Fe containing dispersoid formation at 500oC. The important outcome of this study is heat treatment process‐property contour maps that are useful for fine‐tuning the mechanical properties of PBF‐LB AlSi10Mg alloy for industrial rapid prototyping application.This article is protected by copyright. All rights reserved.

Preparation and Characterization of Bismaleimide-Resin-Based Composite Materials

This study utilized bismaleimide (BMI) resin, reinforced with introduced ether bonds, as a binding matrix, in combination with silicon carbide (SiC), for the fabrication of composite materials. A thorough investigation was conducted to assess the influence of diverse processing parameters on the mechanical properties and high-temperature thermo-oxidative stability of these composites. Experimental results indicate a notable improvement in the mechanical properties of the composites upon the incorporation of ether bonds, in contrast to their unmodified counterparts. The variation in performance among composites with different ratios and molding densities is apparent. Within a certain range, an increase in resin content and molding density is correlated with improved bending strength in the composites. With a resin content of 27.5 vol% and a molding density of 2.31 g/cm3, the composite achieved a maximum flexural strength of 109.52 MPa, representing a 24% increase compared to its pre-modification state. Even after exposure to high-temperature heat treatment, the composites displayed commendable mechanical properties compared to their pre-ether bond modification counterparts, maintaining 74.5% of the strength of the untreated composites at 300 °C. The scanning electron microscopy (SEM) microstructures of composite materials correlate remarkably well with their mechanical properties.

Design and Comparative Analysis of a Renewable Energy Based Rural District Heating System

This research focuses on adapting renewable energy sources for high-temperature rural district heating systems. By utilising Polysun® software, simulations explore combinations of wood chips (biomass), air-water heat pumps, geothermal heat pumps and solar thermal. Emphasising carbon neutrality, the study considers the demand for space heating and domestic hot water. Data acquisition in Middle Franconia involved collecting relevant data from Hotmaps, considering the number of houses, construction year, and heated gross floor area. The study wraps up by presenting optimised models, empowering communities to make emission-effective decisions for sustainable heating solutions. This research contributes significantly to rural heating advancements, promoting energy efficiency and environmental sustainability. In our paper, we suggest solutions for rural energy communities with different technologies to reduce carbon emissions.

Study on the Temperature and Water Distribution of Hot Air in Red Loam Based on Soil Continuous Cropping Obstacles

In recent years, the problematic circumstances of the constant cropping problem in facility crops have become increasingly serious. Compared to chemical disinfection, soil steam disinfestation offers the benefits of environmental protection and being pollution-free, which can effectively reduce the problem of constant cropping in crops. However, during the steam disinfection procedure, a large quantity of liquid water is formed due to the condensation of high-temperature steam, which causes soil pore blockage, seriously affecting the mass and heat transfer efficacy of steam and, thus, affecting the disinfection efficiency. Therefore, to solve this problem, this paper proposes the use of hot air dehumidification to remove excess water from soil pores and achieve the goal of dredging the pores. However, further exploration is needed on how to efficiently remove excess water from different pore structures through hot air applications. Therefore, this paper first used CFD simulation technology to simulate and analyze the hot air flow field, mass, and heat transfer in soil aggregates of different sizes (<2 mm to >8 mm). Then, based on the soil hot air heating experimental platform, research was conducted on the mass and heat transfer mechanism of hot air under diverse soil pore conditions. The results show that as the soil particle size increases from <2 mm to >8 mm, the number of soil macropores also increases, which makes the soil prone to the formation of macropore thermal currents, and the efficiency of hot air heating for dehumidification first increases and then decreases. Among them, the 4–6 mm treatment has the best dehumidification effect through hot air heating, with a deep soil temperature of up to 90 °C and a water content reduction of 6%. The 4–6 mm treatment has a high-temperature heating and dehumidification area of 15–20 cm deep. The above results lay the theoretical foundations for the parameters of hot air heating and dehumidification operations, as well as the placement of the hot air pipe. This paper aims to combine hot air dehumidification technology, for the removal of excess water from soil, and dredging soil pores, ultimately achieving the goal of improving soil steam disinfection efficiency.

Quantitative risk assessment of a spill fire caused by the continuously leaked fuel in a sealed ship engine room

There are a large number of high-temperature heat sources in a ship engine room. Once the oil leakage occurs, it is likely to be ignited and form a spreading and burning spill fire. In this paper, spill fire experiments are conducted in a model-scale ship engine room to investigate their characteristic parameters. The quantitative models of flame height and thermal radiant surface emission power applicable to such fires are verified by the experimental data. Based on that, the classical quantitative risk assessment method is adopted to assess the risk of spill fires using thermal radiation hazard as the main reference, and a detailed framework for quantitative risk assessment of spill fires in ship engine room is established, which includes hazard identification, probability of failure calculation, consequence assessment, and risk quantification. The possible causes of spill fire accidents are briefly analyzed based on the bow-tie model. In cases where thermal threats above the risk threshold for larger leakage rates (70 mL/min), the probability method outperforms the threshold method in terms of accuracy in risk quantification. Additionally, the variation of thermal radiation with combustion diameter is analyzed, and some recommendations for fire emergency rescue are presented.

The impact of interactions between various systems caused by three consecutive years of La Nina events on the abnormal summer high temperatures in China in 2022

In the summer of 2022, like in many other regions of the world, an unprecedented period of continuous high-temperature weather occurred in eastern China. The degree and duration of this event far exceeded normal standards. Between 2020 and 2022, the tropical Pacific experienced the most significant three-year consecutive La Nina event recorded in recent decades. We investigate linkages between these events: the high-temperature response in eastern China and Asia under the background of such La Nina events. Development of summer La Nina events contributed to a high-temperature heat wave during the summer of 2022. Rapid development of these events in the third year exacerbated negative Indian Ocean Dipole phases because of energy accumulation from abnormal easterly winds. The combined effects of the negative Indian Ocean Dipole phase and La Nina provided background field support that strengthened the West Pacific Subtropical High (WPSH) and the Iranian High, leading to high terrestrial temperature anomalies. An empirical orthogonal function (EOF) analysis of the vertical velocity in the middle and low latitudes of the tropical Indian Ocean and the Asian continent reveals the first two empirical orthogonal function modes to be conducive to the strengthening of Walker circulation in 2022. These two main modes jointly reflect the rising movement of the equatorial East Indian Ocean and South China Sea in 2022, and the sinking movement to the west of the Tibet Plateau and eastern China, which was conducive to generating high temperatures in eastern China. Finally, the South Asian High was affected by the La Nina event that lasted for three years, showing a strong trend towards the north, thus making an important contribution to this high temperature.

Investigation on the operating characteristics of a three-phase crystalline energy storage and heating system based on lithium bromide

In the current global energy landscape, energy storage has the potential to become a key technical support for global carbon neutrality. Drawing insights from a comprehensive overview of existing energy storage systems, this paper proposes a three-phase crystalline energy storage and heating system characterized by intermittent operation. The unique thermodynamic property of lithium bromide gifts the system with remarkable energy storage density and heating capacity. To further investigate its operating characteristics, this study employs the Newton iteration method, with energy storage density as a pivotal technical indicator for evaluation. The results reveal that the existence of crystals mainly benefits nighttime heating supply. By adjusting input factors, it becomes evident that increasing the temperature of high-temperature heat source can enhance the heating supply by 16.92 %, which also leads to an increase in energy storage density to 2986.85 MJ/m3. Furthermore, the raising temperature of low-temperature heat source results in a substantial 61.78 % escalation in heating supply. Additionally, the dynamic investment payback period of the system is estimated to be 2.4 years, signifying its economic viability. The findings of this paper can provide valuable theoretical support for the application of crystalline energy storage systems.

Life cycle assessment of post-combustion carbon capture and storage for the ultra-supercritical pulverized coal power plant

In this paper, different emerging post-combustion technologies, i.e., monoethanolamine (MEA), aqueous ammonia, pressure swing adsorption (PSA), temperature swing adsorption (TSA), membrane and calcium looping, were applied to an ultra-supercritical coal-fired power plant for carbon capture. A ‘cradle-to-grave’ life cycle assessment (LCA) was conducted to evaluate the technical performance and environmental impacts of the power plant with six emerging carbon capture technologies. Carbon capture significantly influences the impact categories directly associated with flue gas emission. The application of carbon capture reduced the GWP in the range of 49–75 %. TAP also reduced in the range of 18–51 %. However, the human toxicity potential, eutrophication potential, ecotoxicity potential and particulate matter formation potential increased due to energy and resource consumption in the upstream and downstream processes. For the life cycle water consumption potential, it decreased by 8 % with calcium looping, whereas it increased in the range of 36–75 % with other post-combustion technologies. The highest reduction in GWP and the least reduction in power efficiency was observed in calcium looping because of the high-temperature heat recovery from flue gas and elimination of complex solvent manufacturing. The plant with aqueous ammonia and membrane separation had the second and third highest reductions in GWP. In addition, the lowest values for TAP, FEP, and MEP were obtained in the membrane system. With MEA for CO2 capture, the total GWP value of the plant is slightly higher than these three technologies mentioned above, and the highest HTPc, FETP, and METP can be observed in this case. TSA and PSA have the most significant environmental impacts in most categories due to higher energy requirements.

Liquid metal-enhanced thermoelectric generator for high-temperature thermal harvesting

It is a challenge to achieve high output power of the thermoelectric generator (TEG) for high-temperature waste heat recovery due to the working fluids with low thermal conductivity (such as air) or low tolerance of temperature (water or oil). In this paper, the gallium-based liquid metal (LM) with a high boiling point (>1000 ℃) and thermal conductivity (>20 W/mK) are introduced to significantly enhance heat charging and discharging at the hot/cold sides of TEG. We also developed an electromagnetic induction pumping method for the effective LM-driven flow at high temperatures. A three-dimensional coupling multi-parameter optimization simulation model of LM-based TEG was developed to reveal the internal heat transfer and power generation mechanism for clarifying the impact factors of the performance. The results have shown that the power generation capacity can be effectively improved by increasing the inlet temperature (Thot-in). It is worth noting that the temperature difference (ΔT) of the TEG module is severely limited by the thermal resistance (Rcapacity) of the LM heat capacity, such as, when the flow rate of 2 L/min, the Rcapacity accounts for 90.6 % (0.020 ℃/W). It is easier to achieve a larger open circuit voltage by increasing the height of the thermoelectric leg, but the Pmax is constantly weakened. Compared with Xceltherm 600 and Solar salt, LM heat transfer fluid has more obvious advantages in enhancing the power generation performance of the system. The LM-based TEG experiment platform was established to study heat transfer and power generation characteristics. The results have demonstrated that good consistency was proved by comparing experimental and numerical data. And the Pmax of the LM-based TEG system is 0.16 W/cm2 at ΔT of 136 ℃. LM-based TEG can open new perspectives for broad applications in high-temperature waste heat recovery.

Precision-controlled synthesis of monodisperse starch nanoparticles: Factors affecting the self-assembly kinetics

Enzymatic modification has emerged as a crucial technique for enhancing the physicochemical attributes of starch. In particular, the short-chain glucans (SCGs) obtained from the debranching of native starch has been utilized to produce functional micro- and nano-structures through their inherent self-assembly property. However, a significant challenge remains in controlling the self-assembly kinetics of SCGs, which often results in undesirable heterogeneous structures. This study explores the factors governing SCG self-assembly and their impact on the formation of monodisperse starch nanoparticles (SNPs). We discovered that incomplete removal of the debranching enzyme during SCG self-assembly leads to particle aggregation, with the degree of aggregation dependent on the concentration of remaining enzyme. Furthermore, the initial SCG concentration significantly influences SNP growth; high concentration results in gel-like structures, while lower concentration produces discrete and spherical nanoparticles. Complete dispersion of growth species, SCGs, before self-assembly through appropriate high-temperature heating was found to be critical for uniform nuclei formation, thereby resulting in the production of well-defined nanoparticles. Systematically manipulating these kinetic factors allowed us to fabricate monodisperse SNPs with an average size of 200 nm. This study advances our understanding of SCG self-assembly kinetics, providing valuable insights for the precision-controlled synthesis of starch-based nanoparticles.

Effect of operating conditions on the performance of riser reactor for oxidative coupling of methane

Oxidative coupling of methane (OCM) is characterized by high temperature and strong heat released. A riser reactor is designed for the OCM process to improve gas-solid contacting and heat transfer. This work illustrates the effect of hydrodynamic conditions and feed gas composition on the performance of an OCM riser reactor. The findings suggest that oxidative reactions predominantly occur within the acceleration zone and developed flow zone. Furthermore, at the low superficial gas velocity accompanied by a high solid circulating rate, the C2 yield initially increases in the acceleration zone, followed by a decrease in the developed flow zone and deceleration zone. The optimal operating conditions are a specific region corresponding to the solids holdup ranges from 0.015 to 0.02. Moreover, the C2 yield can be elevated using an appropriate feed mixture.

Comprehensive performance evaluation method of working fluids for high temperature heat pump based on multi-objective optimization

The working fluid has garnered significant attention as a critical factor influencing the efficiency of high-temperature heat pumps. A novel method based on multi-objective optimization has been introduced for assessing the performance of heat pump working fluids. The method enhances the clarity of the objective and flexibility in addressing various operating conditions, which helps to improve the efficiency of working fluid screening, especially for the complex mixture system. This study utilizes eight pure refrigerants as the initial fluid set and evaluates 560 binary mixtures with a 5% composition variation. The NSGA-II algorithm is combined with the theoretical heat pump cycle model to obtain Pareto optimal solutions regarding the mixtures, with the coefficient of performance and volumetric heating capacity as the objective functions. Then the evaluation of the optimal solutions is conducted by considering their flammability, toxicity, environmental performance, and temperature glide properties. Subsequently, a comprehensive performance index is derived. The evaluation reveals the dominant solution set for each pure refrigerant. The findings suggest that the blend R142b/R1233zd(E) with a mass fraction of R142b between 0.15 and 0.25 demonstrates a comprehensive performance index of 0.322–0.350, indicating superior performance during the basic cycle. Furthermore, various cycle configurations have been investigated. In the vapor injection configuration, R600a/R601(0.6/0.4) shows good performance in all aspects except flammability. The mixture R245fa/R601(0.2/0.8) exhibits superior overall performance in the internal heat exchanger configuration. It displays excellent temperature glide matching characteristics and good environmental performance. Nevertheless, it shows suboptimal performance in terms of toxicity and flammability. This approach replaces the previous qualitative comparison-based decision making methods, offering high efficiency and practicality.

An improved laser flash method for thermal conductivity measurement of molten salts

Thermal conductivity measurement of high-temperature heat transfer fluids provides a crucial basis for designing utility-scale thermal systems. Molten salts are promising heat transfer and thermal storage fluids in high-temperature thermal energy storage systems, while the molten salt thermal conductivity obtained in existing studies exhibits large deviations due to the high experimental complexity and unstandardized test procedures. In this work, we improve the conventional laser flash analysis method by proposing a theoretical heat transfer model for multi-layer heat conduction and providing a near-optimal molten salt container design. With water as a test sample, the relative error of thermal conductivity measurement using the improved method is 6.3%. The thermal conductivity of Solar Salt from 250 to 400 ​°C, and of Hitec Salt from 160 to 250 ​°C are measured and compared with the previous work. Both results show that the thermal conductivity increases with the temperature rising. This work will promote the technology standardization for accurately acquiring the thermal conductivity of molten salts or other similar high-temperature heat transfer fluids.

Turbulent flow and heat transfer in a new type of internally torsion-ribbed helical tube

Adding inserts is an effective technique to enhance heat transfer in tubes. In this paper, a new internally torsion-ribbed helical tube is designed to enhance the heat transfer capability and improve the temperature uniformity inside the pipe by adding torsional ribs inside the tube. The flow and heat transfer characteristics of high-temperature heat transfer oil in a straight tube, a common helical tube, and a new internally torsion-ribbed helical tube are numerically compared. The results show that the presence of internally torsional ribs can effectively strengthen the fluid perturbation inside the tube and further weaken the boundary layer, thus improving the heat transfer effect. Moreover, the convergence of strong vortices in the fluid is weakened by 29.3% to 41.2%. The comprehensive heat transfer factor (PEC) of the internally torsion-ribbed helical tube is between 1.1 and 1.2, which is 11.1% to 12.0% higher than that of the common helical tube, and the temperature uniformity TU=0.18% is 72.3% better than that of the common helical tube. These data show that the new helical tube has excellent performance in strengthening heat transfer and preventing carbon deposition and coking caused by high local temperature of high-temperature heat transfer oil.

Preparation of Reduced Graphene Oxide Films with High and Uniform Thickness for Electromagnetic Interference Shielding

Reduced graphene films have attracted widespread commercial interest due to high electrical conductivity toward (EMI) shielding. At present, the preparation path of reduced graphene film is to use graphene oxide (GO) as the raw material through self-assembly and high-temperature heat treatment. However, the thickness of reduced graphene films is not high and uniform because of the higher mobility of the graphene oxide slurry, which destroys the reliability of the membrane in the field of electromagnetic interference shielding. Here, we propose the use of sodium carboxymethyl cellulose (CMC) to increase the viscosity of graphene oxide to prepare reduced graphene films with high and uniform thickness. After modification with sodium carboxymethyl cellulose, the EMI shielding effectiveness (EMI SE) of reduced graphene oxide films stabilized at 91–96 dB at 8–12 GHz, which is higher than pure graphene films. Meanwhile, the addition of CMC does not affect the structure of reduced graphene films. This work broadens the application of reduced graphene films in electromagnetic shielding.

Disodium hydrogen phosphate dodecahydrate/fumed silica composites with high latent heat and suitable phase change temperature for use in building roof

Introducing phase change materials (PCM) with suitable phase change temperature and large latent heat into the application of building roofs is conducive to building energy efficiency, which can reduce indoor temperature fluctuation and improve thermal comfort. In this paper, the optimized disodium hydrogen phosphate dodecahydrate (DHPD) was combined with fumed silica (FS) to prepare a new type of DHPD/FS composites, with a phase change temperature of 41.5 °C, a latent heat of change of 103.46 J/g, and an optimal content of 22.5 % of FS. The leakage experiments proved that there was no leakage of the PCM at this ratio, and after 200 cycles of thermal cycling, the phase change temperature of DHPD/FS composites basically remains unchanged, with good thermal reliability, but the addition of FS will make the material decrease in thermal conductivity, and the thermal conductivity is reduced to 0.19 W·m−1·K−1. Furthermore, the study investigated the application of the encapsulated DHPD/FS composites as a phase change board on the roof. The results indicated that the inclusion of the phase change board improved indoor thermal comfort and demonstrated good thermal performance. When the phase change board was positioned in the top layer, the enhancement of thermal comfort was most optimal.

Stabilization of Ni-YSZ Anodes in Solid Oxide Fuel Cells using an ALD-Grown Aluminum Titanate Interlayer

Abstract The effect of an Al2TiO5 (ALT) interlayer between Ni and YSZ on enhancing the thermal stability of Ni-YSZ solid oxide fuel cell was examined. Atomic layer deposition (ALD) was used to provide precise control of the structure and thickness of the ALT interlayer. The study’s findings demonstrate that a 2 nm thick ALT interlayer deposited by ALD does not adversely affect the cell’s ohmic resistance and effectively prevents Ni sintering and the loss of active area during high-temperature heat treatments. ALT layers thicker than 2 nm, although they enhanced Ni stability, were found to impede oxygen ion transport in the electrode and significantly increase the ohmic resistance of the cell, leading to a decline in performance.

Numerical simulation analysis of high-temperature bent sodium heat pipes

Abstract High-temperature bent heat pipes are safety-level heat transfer components used in heat pipe cooled reactor, and their applications are becoming increasingly widespread. In this study, a comprehensive three-dimensional numerical model was established to evaluate the effects of different bending angles and radii on the performance of high-temperature heat pipes. The model solved for the temperature, pressure, and velocity fields in the wall, wick, and evaporator, considers the compressibility effect of the vapor. The study investigated parameters such as vapor pressure, vapor velocity, radial secondary flow field, wall temperature, wick temperature, and equivalent thermal resistance of powder sintered core sodium heat pipes with bending angles of 45°, 90°, 135°, 180°, and a bending radius under 90°. The results showed that when sodium vapor enters the bent pipe, the vapor flow deviates towards the outer side, resulting in higher vapor pressure at the outer side than the vapor pressure at the inner side, and the generation of radial secondary vortex. This leads to higher temperature in the evaporator and adiabatic sections of the bent heat pipe, while lower temperature in the condenser. Fractal patterns are observed in the outer and inner wall temperature curve in the adiabatic section, with lower temperatures on the inner side and higher temperatures on the outer side. The bent heat pipe exhibits higher equivalent thermal resistance than that of a straight heat pipe, and the equivalent thermal resistance increases with increasing bending angle, and the equivalent thermal resistance decreases with increasing bending radius.