High Temperature Heat Research Articles

INVESTIGATION OF THE EFFICIENCY OF DIESEL FUEL EQUIPMENT IN NON-TRADITIONAL CONDITIONS

To date, Russian and foreign scientists have proposed many different compositions of MMF, as well as methods of high-temperature forcing. It is known that poor-quality tuning of the FSE leads to an increase in costs up to 30 ... 35%, reduces the resource of the internal combustion engines themselves by 1.5 ... 2 times, and worsens their performance. In general, a mixture of diesel fuel, rapeseed oil and ethanol is characterized as a microheterogenic coarse-dispersed concentrated emulsion of the reverse type - "water in oil", in which the polar dispersed phase is in a non-polar dispersion medium. The fragmentation of the dispersed system can significantly affect the performance characteristics of the FSE. High-temperature heating of DF (over 100 ° C) will undoubtedly have an impact on the value of the cyclic fuel supply and the unevenness of its supply when changing the speed mode of operation due to a decrease in kinematic viscosity. An increase in the thermal stress of the parts of the power supply system can cause abnormal situations, mechanical failures and breakdowns and, as a result, a decrease in the service life of the FSE. The study of the operation of FSE on unconventional fuels and under conditions of thermal forcing of diesel fuel is of particular interest.

Microstructural Evolution and Oxidation Resistance of Fe-30Ni-15Cr Alloy for Internal Combustion Engine Valves Under Long-Term High-Temperature Exposure and Heat Treatment

Iron–nickel-based superalloy is an ideal substitute for the expensive Inconel 625 and Inconel 751 alloys. To elucidate the evolution of the microstructure and properties of Ni30 alloy under different thermal treatment conditions, a systematic study was conducted on the microstructural transformation of the alloy’s strengthening γ′ phase following solution treatment and aging, as well prolonged exposure at 750 °C, and the oxidation behavior of the Ni30 alloy was examined. During prolonged thermal exposure, grain growth occurs mainly in the initial stage, and after 200 h, the prolonged exposure time leads to a significant coarsening of γ′ precipitates, whose area fraction increases by more than 10 times compared to their unaged state. After 100 h of aging, the alloy reaches a peak tensile strength of 1270 MPa and a yield strength of 820 MPa; after 2000 h, the alloy maintains a relatively high strength with a slight decrease in ductility. The oxidation kinetic curve of Ni30 alloy follows the quasi-parabolic oxidation law at 750 °C, and its oxidation rate is consistently lower than 0.1 g·m−2·h−1 throughout the whole oxidation process, which indicates that it has excellent oxidation resistance. The external oxide layer of Ni30 alloy shows a bilayered structure, and no obvious surface porosity or flaking of oxidation products were observed throughout the high-temperature oxidation test. This study not only contributes to the improvement of material properties, but also promotes innovation and development in the field of high-temperature engineering applications that will help to meet the increasingly stringent requirements of high-temperature working environments.

Environmental high temperature (heat stroke) causes articular cartilage damage in vivo and in vitro.

Heatstroke (HS) is gradually becoming a major challenge in the field of global public health with the trend of global warming. In recent years, extreme high-temperature weather events have occurred frequently in the world, which directly led to a significant increase in heatstroke. However, up to now, the potential pathological effects of HS on articular cartilage have not been revealed. Therefore, in our current work, we studied the damage of heat toxicity on chondrocytes in vitro. The results showed that heatstroke reduced the cell activity of chondrocytes and triggered a decrease in mitochondrial membrane potential and oxidative stress response. Further biochemical analysis showed that heatstroke caused chondrocyte PANoptosis. On this basis, we further analyzed the molecular mechanism of HS-induced cartilage damage. The results showed that HS activated ZBP-1-mediated PAN-apoptosis. In vivo, our group further evaluated the impact of HS on articular cartilage. The results showed that heatstroke caused damage to articular cartilage, and immunohistochemistry showed that heatstroke caused damage and programmed necrosis of cartilage tissue. On this basis, we evaluated the alleviating effect of FGF21 on HS-induced chondrocyte damage. The results showed that FGF21 could effectively alleviate the PANoptosis of chondrocytes caused by heatstroke via activating the AMPK signaling (at least partially). In summary, the current research lays a foundation for further exploring the cartilage damage caused by heatstroke.

Experimental investigation on thermal performance of high-temperature flat plate heat pipe for temperature management in confined spaces

Experimental investigation on thermal performance of high-temperature flat plate heat pipe for temperature management in confined spaces

Design, Fabrication, and Performance Optimization of a High-Temperature Thin Film Heat Flux Sensor with a Composite Protective Layer

Design, Fabrication, and Performance Optimization of a High-Temperature Thin Film Heat Flux Sensor with a Composite Protective Layer

Si-doped NASICON-type Li1.4Al0.4Ti1.6(PO4)3 solid electrolytes for enhanced stability and performance of Li-CO2 batteries

Li-CO2 batteries (LCBs) have attracted significant research interest owing to their potential as energy storage devices and their contribution to carbon neutrality. In this study, we synthesized a solid electrolyte using Si-doped Li1.4Al0.4Ti1.6(PO4)3 (LASTP), by incorporating Si into the NASICON-structured LATP. Through Si doping, P in the tetrahedral PO4 units within the NASICON framework is substituted with Si, and bridging oxygen bonds are formed after high-temperature heat treatment The LASTP powder synthesized via a solution-based method exhibited uniform particle size and composition, and the resulting pellet achieved high densification and the formation of interconnected structures. The pellet exhibited an ionic conductivity of approximately 8.8 × 10-4S/cm at 25℃. The LCB utilizing LASTP demonstrated a maximum discharge capacity of 23,887mAh/g and successfully operated for 200 cycles at a current density of 100mA/g with a cut-off capacity of 500mAh/g. The post-cycling analysis of the cathode confirmed the reversible reactions of the LCB. Additionally, comparative post-cycling XPS analysis of LATP and LASTP revealed that Si doping in LASTP mitigated the reduction of Ti4+ to Ti3+, thereby enhancing the chemical stability of the solid electrolyte. Also, the structural stability of the solid electrolyte was enhanced owing to the formation of new bonds, surpassing the cycle performance and full-depth capacity of LCBs using conventional solid electrolytes. The introduction of structurally and chemically stabilized LASTP enabled the realization of long-lasting, high-capacity LCBs.

The Optimal Ratio of the Temperature Differences for Heat Transfer in Evaporator and Condenser

In the design of a refrigeration / heat pump system, the selections of the temperature differences for heat transfer (i.e., in the evaporator it is the temperature difference between the low temperature heat source and the refrigerant, and in the condenser, between the refrigerant and the high temperature heat source) are based on some kind of “rule of thumb”. To be more scientifically in the design, this paper presents the optimal ratio of the temperature differences for heat transfer in the evaporator and in the condenser, from the second law (the entropy or the exergy) analysis. That is the optimal ratio is the ratio of the temperatures of the high-temperature heat source (heat sink) and the low-temperature heat source (heat source). This finding is called “You’s Principle”.

Steady-state thermal-structural analysis of high-temperature heat pipes based on thermal-fluid coupling

Steady-state thermal-structural analysis of high-temperature heat pipes based on thermal-fluid coupling

Experimental Investigation of a Regenerative Kalina Cycle for Electrical Power Generation Using Waste Heat

Kalina cycle is a thermodynamic power cycle uses any waste heat source (low temperature source) to generate electrical power or cooling. Many versions of Kalina cycle exist. In this paper a regenerative Kalina version is designed and constructed. The cycle consists of the following main components: heat recovery vapor generator (HRVG), separator, turbine, condenser, throttling valve, mixer (absorber), heat exchanger and pump. The heat exchanger is used to heat the working fluid coming from the pump before entering the HRVG by the hot saturated liquid (weak solution) coming from the separator. The cycle uses aqua ammonia mixture as the working fluid with different ammonia concentrations. The effect of many operating conditions on cycle performance is studied such as ammonia (NH3) mass fraction (range from 0.85-0.89), low pressure (range from 2-4 bar), and maximum pressure (range from 20-40 bar). The dryness fraction (DF) at separator entrance is kept at 0.3. The results show that the highest thermal efficiency obtained is 12.9% at Pmax=35 bar, Pmin=2 bar, and x=0.85. The highest value of the net power is 0.367 kW at x=0.89 at turbine inlet pressure of Pmax=20 bar. The highest value of exergy efficiency is 28.5% at Pmax=35 bar, Pmin=2 bar. It is noticed that the highest exergy destruction is in the heat recovery vapor generator (HRVG) which is about 48% due to high temperature heat exchange process and low mass flow rate. The exergy destruction is larger at Pmax=35 and x=0.89 than the exergy destruction at Pmax=20 bar and x=0.89.

Techno-Economic Comparative Assessment of High-Temperature Heat Pump Architectures for Industrial Pumped Thermal Energy Storage

Abstract The industrial sector is a key global source of wealth, but it is also recognized as a major challenge toward worldwide decarbonization. Today, the industrial sector requires more than 22% of the global energy demand as thermal energy and produces for this about 40% of the total CO2 emissions. Solutions to efficiently decarbonize the industrial sector are deemed. This work presents a comparative techno-economic performance assessment of a high-temperature heat pump (HTHP) integration within a molten salts (MSs) based power-to-heat system for industrial heat flexible generation. The main system performance is reported in terms of required working conditions and temperature for the heat pump and thermal demand size as well as reduction of the attainable levelized cost of heat (LCoH) against nonflexible electric boiler based systems. The impact of different industrial load profiles, electricity prices, heat pump capital cost, and heat pump real to Carnot efficiency ratio are also presented. The results highlight that the proposed system can be cost-competitive, particularly for thermal demand around 10 MW and waste heat temperatures above 80 °C. Under these conditions, LCoH reductions higher than 15%, with respect to the considered nonflexible electric boiler alternative, are attainable. These LCoH reductions are primarily driven by savings in electrical consumption as high as 30%. This study sets the ground for further power-to-heat techno-economic investigations addressing different industrial sectors and identifies main system and components design strategies, integrations, and targets.

Fracture failure behavior of Al2O3 fabric under the combined interaction of high-temperature heat flow and tensile load

Fracture failure behavior of Al2O3 fabric under the combined interaction of high-temperature heat flow and tensile load

Effect of Oxygen-Enriched Air on Flame Temperature and Emission Characteristics During Hot Producer Gas Combustion in a Modified Cross-draft Gasifier-Burner

ABSTRACT Converting biomass into energy is increasingly recognized as a vital strategy for achieving sustainable energy solutions and mitigating climate change. As global industries shift toward greener alternatives, the use of biomass, such as wood scraps, offers significant potential to reduce net greenhouse gas emissions compared to fossil fuels. Gasification provides a cleaner alternative to traditional combustion methods, particularly for applications requiring high-temperature heat sources, such as ceramics, metal processing, and cement production. This study investigates the optimization of flame temperature during the combustion of synthetic gas produced from a modified cross-draft gasifier and burner by adjusting oxygen-enriched secondary air concentrations, ranging from 21% to 36% by volume. Combustion using 36% oxygen-enriched air achieved a flame temperature of 1,358.3°C, reflecting a 20% increase compared to combustion with standard air (21% oxygen). Further reducing excess oxygen in the exhaust gases led to an additional 4% increase in flame temperature, reaching 1,416.0°C. However, this reduction also resulted in a marked rise in NOx emissions, increasing from 119 ppm to 424 ppm, due to the higher burner temperatures. These findings underscore the importance of balancing oxygen enrichment to optimize combustion performance while managing pollutant emissions, offering a sustainable alternative to fossil fuels for emission-intensive industries.

The Obtaining and Study of Composite Chromium-Containing Pigments from Technogenic Waste

This article provides information on the processing of chromium-containing waste from the Aktobe ferroalloy compounds plant using chemical reagents followed by high-temperature heat treatment for the synthesis of a composite chromite pigment used in the textile industry. This technology was developed for the first time for the purpose of recycling industrial waste and rational use of natural resources. The obtained pigments were analyzed by the X-ray phase of a D878-PC75-17.0 incident beam monochromator and the phase composition of the composite chromite pigment was studied. The thermogravimetric analysis of the composite chromite pigments was performed using a TGA/DSC 1HT/319 analyzer to determine the change in mass with time and temperature. According to the TGA results, the mass loss was determined to be 0.18% of the total mass. The elemental composition of the composite chromite pigment was determined using a JEOL JSM-6490 LV SEM device and the content of chromium oxide (Cr2O3) was determined, which reached up to 50%. The thermodynamic patterns of the processes occurring during the production of chromite pigments were studied using the integrated Chemistry software pack HSC-6. The results of testing printed and processed cotton and composite fabrics by the proposed method showed that the color fastness to washing and wet and dry friction is 4 points and the wear resistance assessment is 4860 and 6485 cycles, respectively. Composite chromite pigment based on technogenic wastes is recommended for use in various coloring compositions, including those used for printing on cotton and composite fabrics.

Evaluation of the Effect of Precursor NMC622@TiO2 Core-Shell Powders Using a Prelithiated Anode from Fig Seeds: Spotlight on Li-ion Full-Cell Performance.

In this study, innovative electrode materials for lithium-ion batteries (LIBs) were developed and characterized, demonstrating significant performance enhancements. Initially, NMC622@TiO2 was synthesized using a wet-chemical method with titanium(IV) ethoxide as the Ti source. Advanced structural investigations confirmed the successful formation of a core@shell structure with negligible cation mixing (Li+/Ni2+) at the NMC622 surface, contributing to enhanced electrochemical performance. Subsequently, carbon-based anode materials were produced from biomass, specifically fig seeds, and subjected to high-temperature heat treatment. The resulting powders exhibited dominant graphitic properties, evidenced by a Raman ID/IG ratio of 0.5. Electrochemical evaluations of both electrode materials were conducted using half-cell configurations. The optimization of the TiO2 coating process was assessed through half-cell performance metrics and diffusion rates calculated from galvanostatic intermittent titration technique (GITT) experiments. The final phase focused on full-cell design, employing a prelithiation strategy for anodes using a direct contact technique. Optimization of the prelithiation process led to the assembly of full cells combining NMC622/prelithiated fig-seed anodes and NMC622@TiO2/prelithiated fig-seed anodes. The results revealed that TiO2-coated NMC622, paired with prelithiated carbon anodes derived from fig seeds, delivered superior performance compared to uncoated NMC622 full cells. This study underscores the potential of biomass-derived carbon anodes and TiO2 coatings in enhancing the efficiency and performance of LIBs.

Thermodynamic Models of Solid Oxide Fuel Cells (SOFCs): A Review

In the delicate context of climate change and global warming, new technologies are being investigated in order to reduce pollution. The SOFC stands out as one of the most promising fuel cell technologies for directly converting chemical energy into electrical energy, with the added benefit of potential integration into co-generation systems due to its high-temperature waste heat. They also offer multi-fuel flexibility, being able to operate on hydrogen, carbon monoxide, methane, and more. Additionally, they could contribute to carbon sequestration efforts and, when paired with a GT, achieve the highest efficiency in electricity generation for power plants. However, their development is still challenged by issues related to high-temperature materials, the design of cost-effective materials and manufacturing processes, and the optimization of efficient plant designs. To better understand SOFC operation, numerous mathematical models have been developed to solve transport equations coupled with electrochemical processes for three primary configurations: tubular, planar, and monolithic. These models capture reaction kinetics, including internal reforming chemistry. Recent advancements in modeling have significantly improved the design and performance of SOFCs, leading to a sharp rise in research contributions. This paper aims to provide a comprehensive review of the current state of SOFC modeling, highlighting key challenges that remain unresolved for further investigation by researchers.

Implementation of an Improved 100 CMM Regenerative Thermal Oxidizer to Reduce VOCs Gas

In this paper, an improved 100 CMM regenerative thermal oxidizer (RTO) is implemented for low-emission combustion. The existing RTO system is a cylindrical drum structure that cyclically introduces and discharges VOC gas into and from the rotating disk, and which achieves excellent energy efficiency with a heat recovery rate of more than 95%. However, the drive shaft designed under the RTO combustion chamber increases wear around the rotating shaft due to the load of the combustion chamber and there is a problem that the untreated gas is simultaneously released through the outlet due to the channeling phenomenon of the combustion chamber and the drive shaft. In addition, the combustion chamber, used at a high temperature of 800 °C, may cause serious problems such as rotation stop or explosion due to pollutants, dust accumulation, and thermal expansion in the chamber. Particularly when treating VOCs harmful gasses, RTO performance may be degraded due to the burner’s non-uniform temperature control and unstable combustion function. To solve this problem, first, the design of the combustion chamber rotating plate driving device is improved. Second, when treating high concentration VOC gas, the design of combustion chamber considers a temperature increase of up to 920 °C or more. For this, the diameter of the gas burner is 125 mm and the outlet dimension is set to 650 mm × 650 mm to effectively discharge high-temperature waste heat. Third, the heat storage material in the combustion chamber is composed of a ceramic block with a thickness of 250 mm, and the outer diameter and height of the combustion chamber are set to, 2530 mm and 1875 mm, respectively, to optimize gas residence time and heat insulation thickness. Fourth, we supplement safe operation by applying the trip control algorithm of the programmable logic controller (PLC) panel for failure prediction of RTO and the Edge-IoT-based intelligent algorithm for this. Finally, we evaluate the economic performance of 100 CMM RTO by conducting empirical experiments to analyze changes in VOCs removal efficiency, nitrogen oxide emission concentration, and total hydrocarbon (THC) concentration through 10 CMM design and implementation.

Assessment of heat storage integration for water vapour compression heat pumps: thermodynamic and techno-economic perspectives

ABSTRACT The integrated system, consisting of a two-stage high-temperature heat pump (HTHP) and thermal energy storage (TES), has been proposed as an effective solution to reduce CO2 emissions in industrial processes effectively. The water vapour HTHP, which can supply heat at 200°C, demonstrated a coefficient of performance (COP) between 4.4 and 7.5. Two different TES systems were introduced: concrete sensible heat storage (SHS) and strontium bromide/water (SrBr2/H2O) thermochemical energy storage (TCES). While the concrete SHS is limited to temperature below 200°C, the SrBr2/H2O TCES can deliver heat between 196°C and 228°C with higher cycle efficiency. The integrated system of HTHP and SrBr2/H2O TCES achieved a net present value (NPV) of €464,559 and €182,374 over a 20-years lifespan, with internal rates of return (IRR) ranging from 15.8% to 23.6%. This HTHP and TCES system has sufficient potential to replace fossil-fuel industrial boilers, leading to significant reduction in CO2 emissions in industrial processes.

Combustion and Emission Characteristics of Methanol–Diesel Dual Fuel Engine at Different Altitudes

Currently, in the two technological approaches for using diesel pilot injection to ignite methanol and partially substituting diesel fuel with methanol, neither can fully achieve carbon neutrality in the context of internal combustion engines. Compression-ignition direct-injection methanol marine engines exhibit significant application potential because of their superior fuel economy and lower carbon emissions. However, the low cetane number of methanol, coupled with its high ignition temperature and latent heat of vaporization, poses challenges, especially amidst increasingly stringent marine emission regulations. It is imperative to comprehensively explore the impacts of the engine geometry, intake boundary conditions, and injection strategies on the engine performance. This paper first investigates the influence of the compression ratio on the engine performance, subsequently analyzes the effects of intake conditions on methanol ignition characteristics, and finally compares the combustion characteristics of the engine under different fuel injection timings. When the compression ratio is set at 13.5, only an injection timing of −30 °CA can initiate methanol compression ignition, but the combustion is not ideal. For compression ratios of 15.5 and 17.5, all the injection timings studied can ignite methanol. Reasonable increases in the intake pressure and intake temperature are beneficial for methanol compression ignition. However, when the intake temperature rises from 400 K to 500 K, a decrease in the thermal efficiency is observed. Particularly, at an injection timing of −30 °CA, both the peak cylinder pressure and peak cylinder temperature are higher, the ignition occurs earlier, the combustion process shifts forward, and the combustion efficiency and indicated thermal efficiency are at higher levels. Furthermore, the overall emissions of NOX, HC, and CO are relatively low. Therefore, selecting an appropriate injection timing is crucial to facilitate the compression ignition and combustion of methanol under low-load conditions.

Performance Analysis of a Water-Injected Twin-Screw Compressor in a High-Temperature R718 Heat Pump

Abstract High-temperature heat pumps with twin-screw compressors and water (R718) as the working fluid show promising potential for providing industrial heat and process steam at temperature levels of up to 200 °C. This paper presents a simulation approach for a two-layered simulation structure of a water-based high-temperature heat pump system including a twin-screw compressor with water-injection. The heat pump process with two-phase steam compression is investigated with respect to various aspects. In addition to controlling the compressor outlet temperature, the evaporation of the injected liquid leads to an increase in the displaced mass flow rate on the sink side of the heat pump. This effect is analyzed in detail for various system operating points using a thermodynamic simulation framework for the R718-based heat pump cycle and a comprehensive compressor model. The main target of the presented paper is the analysis of system performance and the detailed investigation of the interdependencies. Performance of the twin-screw compressor is determined by means of two-phase chamber model simulations. In the chamber model method thermodynamic properties of both injected liquid and steam are calculated based on the conservation equations of mass and energy for the compression process. Adequate sub-models for internal leakage and heat and mass transfer between vapor and liquid phase are applied. Integral results of the compressor simulations are embedded in the heat pump system simulation using a characteristic map. In conclusion, this paper contributes to the understanding of advanced compression technologies in the field of high-temperature heat pumps, offering a detailed examination of a water-injected steam compressor’s applicability and efficiency in a practical system setting.

Metallic wood-based phase change material with superior anisotropic thermal conductivity and energy storage capacity

In this study, metallic wood-based phase change material (MWM) with high performance anisotropic thermal conductivity and energy storage capacity was developed by impregnating wood with myristic acid, and subsequent introducing low melting point alloy (LMA) into the wood through a facile alternating high and low temperature heat treatment. The heat-driven LMA was rapidly squeezed into the cell lumens of the wood so as to effectively inhibit the leakage of the internal myristic acid during melting. Benefited with the well-aligned and hierarchical porous structure, the filled LMA formed a continuous heat transfer network along the highly oriented transport tissue of wood, which could greatly reduce the interfacial thermal resistance and promote heat transfer. Compared with untreated wood, the thermal conductivity of MWM in longitudinal and radial directions were improved by more than 67 % and 75 %, respectively. In addition, it exhibited superior energy storage capability, with the latent heat of 90.23 J/g and 86.42 J/g during melting and solidification. The thermal stability and anti-leakage performance were satisfied. The phase change temperatures, enthalpies and chemical structure of MWM remained unchanged after 100 thermal cycles, demonstrating outstanding cycling reliability. With excellent energy storage performance and favourable thermal conductivity, the prepared MWM shows a promising application in energy saving buildings and solid wood floors.