Heat Characteristics Research Articles

Diversified characteristics of the dissipative heat on the radiative micropolar hybrid nanofluid over a wedged surface: Gauss-Lobatto IIIA numerical approach

The present examination focuses on the Falkner-Skan flow of micropolar hybridized nanofluid via a wedge surface. The proposed study examines thermal radiative fluxing and heat dissipation in hybridized nanoparticle aqueous solutions. Simulations of uni-directional radiative transport in optically dense fluids use Rosseland's diffusion model. This study created a Cu-TiO2/water hybrid nanofluid by mixing Cu and TiO2 nanomolecules with H2O. Partial differential equations from Naiver-Stokes theory are used to generate the regulating flow phenomena, then convert them into ordinary differentiation equations using an appropriate similarity approach. Additionally, the three-stage Lobatto IIIA method is used to compute the formulae. Calculations are done using MATLAB's built-in bvp5c function. We found that increasing material characteristics slows fluid flow because micropolar nanofluids minimize drag. These alterations alter fluid flow and boost temperature. However, boosting thermal radiation and Eckert number slows heat movement but improves temperature profiles. Much prior research ignored thermal radiative fluxing and heat dissipation in the aqueous solution of hybrid nanomolecules (Cu and TiO2) in Falkner-Skan micropolar flow via a wedge surface. Tables show wall frictional factor and Nusselt quantity results. Micropolar fluid characteristic decreases velocity but increases micro-rotational velocity. Power-law parameters, volume fractions, radiation, heat source, and Eckert amount affect thermal contours.

Scalable, High‐Yield Monolayer MXene Preparation from Multilayer MXene for Many Applications

MXene (Ti3C2Tx) is renowned for its exceptional conductivity and hydrophilicity; however, the low yield of monolayers hinders its industrial scalability. Herein, we present a strategy to substantially enhance the monolayer yield by disrupting the hydrogen‐bonding cage confinement of multilayer MXene using high‐temperature ultrasound, challenging the conventional belief that monolayer MXene can only be prepared at lower temperatures. At approximately 70 °C, the weakened hydrogen bonding between the oxygen‐containing terminal groups of multilayer MXene and surrounding water molecules weakens the hydrogen‐bond cage confinement. This enables ultrasonic cavitation to generate more microbubbles that penetrate the interlayers of multilayer MXene, resulting in gentle and thorough delamination into larger monolayer nanosheets. Achieving up to a 95% yield in just tens of minutes, these nanosheets exhibit properties comparable to those produced by traditional ice‐bath methods. Furthermore, the high‐concentration MXene ink produced on a large scale using this high‐yield approach exhibits excellent printing and processing capabilities, and the corresponding products showcase superior infrared stealth and Joule heating characteristics. This work addresses a key technical bottleneck in MXene production, paving the way for its extensive technological and industrial applications.

Scalable, High-Yield Monolayer MXene Preparation from Multilayer MXene for Many Applications.

MXene (Ti3C2Tx) is renowned for its exceptional conductivity and hydrophilicity;however,the low yield of monolayers hinders its industrial scalability. Herein, wepresent a strategy to substantially enhance the monolayer yield by disrupting thehydrogen-bonding cage confinement of multilayer MXene using high-temperature ultrasound,challengingthe conventional belief that monolayer MXene can only be prepared at lower temperatures. At approximately70 °C, the weakened hydrogen bondingbetween the oxygen-containing terminal groups of multilayer MXene and surrounding water molecules weakensthe hydrogen-bond cage confinement. Thisenables ultrasonic cavitation to generate more microbubbles thatpenetrate the interlayers of multilayer MXene,resultingin gentle and thorough delamination into larger monolayer nanosheets.Achieving up to a 95%yield in just tens ofminutes,these nanosheets exhibit properties comparableto those producedbytraditional ice-bath methods. Furthermore, the high-concentration MXene ink produced on a large scale using this high-yield approachexhibits excellent printing and processingcapabilities, and the correspondingproducts showcase superior infrared stealth and Joule heating characteristics. This work addresses a keytechnical bottleneck inMXene production, paving the way for its extensive technological and industrial applications.

Defect identification of nano-cementitious composites, using statistical analysis of thermal images

Carbon-based nanomaterials have diverse applications, including in electronics, energy storage, and environmental remediation. Current research aims to enhance the multifunctionality of construction materials by integrating cement with carbon-based nanomaterials known for their high thermal and electrical conductivity. However, nano-cementitious composites may develop internal defects due to the agglomeration of nanomaterials during fabrication. This study aims to utilize the heat characteristics of nano-cementitious composites for detecting internal defect. Test specimens were prepared by incorporating 1 wt% Multi-Walled Carbon Nanotubes (MWCNTs) into the cement paste. Internal defect sizes were defined from 5 % to 25 % of the specimen's area and were positioned in the center of the specimen. A heat generation test was conducted to capture thermal images and temperature data. Quantitative analysis followed, examining the correlation between defect size and temperature through statistical analysis of the thermal images, using skewness to assess this correlation. The results of the skewness analysis indicated a linear correlation with defect size. A parametric study was conducted to analyze the impact of the number of pixel data on skewness, and it was derived that at least 1500 pixel data are required. Consequently, this study concludes that internal defects in nano-cementitious composites can be detected and their sizes can be inferred through the linear relationship between defect size and skewness.

Non-linear charged dS spacetime and its thermodynamics and Schottky Anomaly

Abstract In this paper, firstly, the conditions and existence region for the coexistence of the black hole and cosmological horizons in Non-linear charged dS (NLC-dS) spacetime are discussed, subsequently, the thermodynamic quantities for which the boundary conditions are satisfied in spacetime in the coexistence region of the two horizons are discussed, and the effective thermodynamic quantities in the NLC-dS spacetime in the coexistence region with two horizons are presented. Based on these, the heat capacity in the coexistence region with two horizons is addressed, the behavior of the heat capacity in the NLC-dS spacetime in the aforementioned region is found to exhibit the characteristics of Schottky specific heat. In order to investigate the intrinsic reason of the heat capacity in spacetime, regarding the two horizons in the NLC-dS spacetime as two distinct energy levels, consequently, the microscopic particles at different horizons exhibit disparate energies. Using the heat capacity relationship between the two-energy level in an ordinary thermodynamic system, the heat capacity in dS spacetime is discussed, it is observed that the behavior of the heat capacity is analogous to that of the two-energy levels in an ordinary thermodynamic system. The number of microscopic particles in the two-level system is approximated by comparing the maximum value of the heat capacity of the system with the maximum value obtained by treating the two horizons in the NLC-dS spacetime as a two-energy-level system of two distinct energies. This conclusion reflects the quantum properties of the coexistence region with two horizons in the NLC-dS spacetime. It provides a new avenue for further study of the thermodynamic properties of black holes and the quantum properties of de Sitter spacetime.

Исследование новых биполярных систем для радиочастотной абляции

Radiofrequency ablation (RFA) is a minimally invasive way to treat cancer. The main problem of RFA is insufficient heating volume. The aim of the work is to create new electrode systems to improve heating characteristics by increasing the number of electrodes operating in bipolar mode. Studies were carried out on a four-channel installation ‘METATOM-3’. The number of dual electrodes varied from 1 to 8. The results of thermal fields obtained with such electrode systems are presented. Potato, whose structure changes when heated up to 60°C, was used as a simulator of biological tissue for the first time, which allows visualising the volumetric picture of the thermal field. To investigate the temperature distribution in the heating volume, a thermal imaging study of the tissue simulators was also carried out. It was found that the increase in the number of electrodes and transition to bipolar mode make it possible to eliminate the need for switching and increase the uniformity of the resulting heating, which is evident from the results of thermal imaging study.

Study of hybrid nanofluid flow in a porous medium over an exponentially stretching sheet under Joule heating and thermal radiation: Finite difference

The significant purpose of present investigation of the behavior of a nanofluid's in magneto-hydrodynamics (MHD), mass transfer, Joule heating, and boundary layer transfer characteristics over an exponentially stretching sheet in a porous medium and thermal radiation effects. The article's goal is to look at the fluid flow and heat transmission characteristics from a sheet of hybrid nanoparticles. The partial differential equations (PDEs) that were derived for the mathematical model were converted using the proper similarity transformation into ordinary differential equations (ODEs). The hybrid nanofluid composed of 97 % of ethyl glycol (EG) and the volume concentration of Magnetite (Fe3O4) and Copper(Cu) are ranging from 0.5 % to 2.5 % both respectively. The effects of thermal radiation, stretching rate, Joule heating, porous medium permeability, and nanoparticle volume fraction on the flow and heat transmission properties are investigated by numerical simulations using the finite difference method (FDM). The analysis reveals that the inclusion of nanofluids enhance the thermal conductivity and enhance the heat transfer rate. Additionally, the influence of variable viscosity on the flow behavior and thermal characteristics are examined graphically. The effects of variable viscosity and thermal conductivity are examined, as it has significance in optimizing system under various thermal and magnetic effects. This study offers a pathway to develop more efficient thermal management solutions, by contributing to technological advancement and energy saving. The key findings of present study reveal that the temperature profile rises significantly due to Joule heating effects. The Nusselt number reveal an improvement of about 12 % when the volume fraction of nano particles is increased by 1–4 % indicating the enhancement in heat transfer efficiency. Similarly, the velocity profile was influenced by porous medium permeability as 11 % increase in porosity result a 18 % decrease in velocity profile.By using parametric research, the role of physical parameters in determining the local skin-friction coefficient, temperature, nanoparticle volume percentage, and longitudinal velocity profiles, local Nusselt number, and local Sherwood number are thoroughly examined. A graphic representation of the velocity, temperature, and concentration distribution findings is presented.

Design and multiperformance evaluation of the ternary azeotrope separation process via extractive distillation based on different extractants

Resource utilization and sustainable wastewater treatment have received widespread attention because of their efficient use of energy. In this study, an ethanol (EtOH)/ethyl tert-butyl ether/water ternary azeotropic system was used to explore the separation efficiency of various extractants. The relative volatility, toxicity, and process modeling of extractants were analyzed to provide a theoretical basis and practical guidance for screening the optimal extractant among nine commonly used extractants. Extractive distillation (ED) was optimized for six processes with a focus on total energy consumption (TEC) and total annual cost (TAC). The ED-EtOH process was the most economical, whereas the extractive ED-DMSO process had the lowest TEC. After heat integration (HI) treatment, the TAC and TEC of each process were reduced, among which HI-ED-EtOH and HI-ED-glycerol (GLY) had the best and lowest economy, respectively. Although high-boiling point and high latent heat extractants (such as GLY and EtOH) increase the heat demand and operating costs, their high latent heat characteristics can effectively recycle heat energy during the HI process. The optimal balance between economy and energy consumption was determined through multi objective optimization considering the physical and chemical properties, environmental impact, and adaptability of extractants.

Characteristics of heat and mass transfer in moist air-ionic liquid desiccant bubbly systems: Parametric assessment of regeneration performance

Ionic liquids (ILs) have recently become an increasingly popular working medium for liquid-desiccant deep dehumidification as applied to low-humidity industries and, in particular, the use of IL desiccants in bubble columns regeneration has been proven to be an effective way to promote their deep dehumidification potential. The present work considers a moist air-IL desiccant bubbly deep dehumidification/regeneration system, focusing specifically on the heat and mass transfer characteristics of regeneration in bubble column. An experimental apparatus is constructed and used to explore the effects of key operating parameters (i.e., liquid height H, superficial velocity vs, solution temperature Ts) on regeneration performance. Furthermore, a semi-analytical model of bubbly regeneration heat and mass transfer is developed and used to perform parametric assessments. The results indicate that elevating the liquid height, as well as higher superficial velocities and solution temperatures all contribute to improved regeneration rates, each with distinct influencing mechanisms. A higher superficial velocity enhances the volumetric transfer coefficient through a combined effect (i.e., gas–liquid specific interfacial area, heat and mass transfer coefficients). The effect of the solution temperature on the volumetric transfer coefficient is mainly reflected in the heat and mass transfer coefficient as determined by the transfer potential difference, while the hydrodynamics play a relatively minor role in the system of interest. Bubbly regeneration differs from deep dehumidification in terms of the volumetric transfer and heat/mass transfer coefficients. Notably, the Lewis number of bubbly regeneration is generally between 0.6–1. In practical applications, it is necessary to consider the air-side pressure drop, droplet entrainment, and low-grade thermal energy utilization. Under recommended conditions (e.g., H = 0.3 m, vs = 3.0 cm/s, Ts = 60 °C), a regeneration rate of 49 g/h and moisture effectiveness of 79 % can be achieved. This study provides guidance for the design of moist air-IL desiccant bubbly deep dehumidification/regeneration systems.

COMSOL-Based Simulation of Microwave Heating of Al2O3/SiC Composites with Parameter Variations

The process of microwave heating involves the coupling of multiple physical phenomena, specifically including the distribution of the electromagnetic field in the resonant cavity. The electromagnetic effect generates heat and encourages the transfer of heat inside the material. In this numerical study, a 3D computer model of microwave heating of Al2O3/SiC composites using a multimode microwave heating chamber was established based on the simulation software COMSOL Multiphysics 5.6, and the symmetry treatment of the model was carried out, which effectively reduced the amount of model calculations and accurately analyzed the microwave heating characteristics of the samples. The analysis of the microwave heating characteristics of the sample was mainly preformed from the perspective of the electric field distribution in the resonant cavity, the sample heating rate and the sample heating uniformity, and then it was determined how the microwave source power and sample mold selection affect the temperature and electric field parameters of the sample. After experimental verification, the error between the simulation results and the temperature parameters obtained from the actual experiments is less than 2%. This study contributes to further understanding the heating behavior of Al2O3/SiC composites in complex multimode microwave heating environments and can be used to control the dynamic parameters during microwave heating in order to improve the heating rate and heating uniformity of samples.

Growth, optical and thermal properties of YbxSm1-xCa4O(BO3)3 crystals

YbxSm1-xCOB (x = 0.1, 0.2) crystals were grown by the Bridgman method for the first time. The purpose of this paper is to evaluate the application prospect of Yb:SmCOB crystal in quasi-parametric chirped pulse amplification (QPCPA) and frequency-doubling laser. The phase structure, thermal properties and optical properties of Yb:SmCOB were studied, and the density of states of SmCOB crystal was calculated by first-principles. The effective segregation coefficient Keff of Yb0.1Sm0.9COB and Yb0.2Sm0.8COB crystals are 0.89 and 0.88, respectively. The thermal diffusivity and thermal conductivity of Yb:SmCOB decrease with increasing temperature. The specific heat increases with the increase of temperature and eventually tends to be constant. The specific heat of Yb:SmCOB crystal is greater than 0.70 J/(g·K) at room temperature. The transmittance of Yb:SmCOB crystal reaches 87 % in the range of 500 ∼ 900 nm. With the increase of Yb3+ doping concentration, the UV absorption cut-off edge is red shifted. The frequency doubling emission peak of Yb:SmCOB crystal at 490 nm was measured by 980 nm laser. Yb:SmCOB has the characteristics of high transmittance and high specific heat, and has application potential in laser frequency doubling and QPCPA.

Heating pattern and effects of built-up land in response to influencing factors: A statistical estimation of 172 Chinese cities

The increase of the land surface temperature (LST) caused by an urban expansion poses a great threat to the humanity and society. However, the heating characteristics of built-up land and the environmental impacts on these mechanisms remain poorly understood over large areas. Therefore, the change trend (k) and structural distribution of LST during the process of increasing the built-up area in 172 cities in China was quantified. Using correlation analysis and statistical methods to analyze the correlation and possible driving characteristics of influencing factors (climate, topography, land use type, and soil) on k. The results indicated that k varied from −5.955 to 8.240 and showed a spatial characteristic of small in the northwest and large in the southeast. The research emphasized the heating difference of built-up land varied significantly in cities with different natural environmental conditions, with the maximum difference reaching 6 °C. The heating mechanism of built-up land under the interference of influencing factors was explained from the perspective of land surface heat flux, and the mitigation strategies for urban temperature were proposed. Besides, the threshold for the impact of environmental factors on the heating of built-up land was found, which provides a reference for environment-adapted urban design and planning standards tailored by considering the specific characteristics of each city.

Experimental Study on the Combined Heat Storage and Supply of Air/Water-Source Heat Pumps

As the application of renewable energy becomes increasingly extensive, heat pump technology with renewable energy as the heat source is achieving good results. Air-source heat pumps and water-source heat pumps can be widely used in cold areas. In this work, an integrated combined storage and supply system of an air-source heat pump and a water-source heat pump was studied, and the heating characteristics of the system at the beginning, middle, and end of the heating period were examined. It was found that, when the outdoor temperature of the system was very low, the efficiency of the combined storage and supply system reached the highest value of 2.57 when the source-side water tank was kept at 30 °C, and the performance of the combined storage and supply system was better than that of the air-source heat pump and the water-source heat pump in cold regions. Meanwhile, the independent storage of the air-source heat pump and the combined storage and supply system can be used for heating at the beginning and end of the heating period.

Experimental and numerical investigation of the influence of varying micro-channel width on flow and heat transfer uniformity

This study integrates experimental and numerical methods to investigate the heat transfer and flow characteristics of microchannel heat sinks with varying width distributions. Water is used as the working fluid and laminar flow model is applied for simulation. Specifically, ten different width distribution structures were designed, including uniform-width configurations and nine non-uniform-width structures (I to IX) with progressively refined intermediate channel widths. Numerical simulations were employed to analyze the flow and heat transfer behaviors, and experimental validations were conducted on both the uniform-width structure and structures II, IV, V, VI, and IX. Results indicate that in uniform-width channel structures, the pressure drop and mass flow rate in intermediate channels exceed those in side channels, resulting in uneven temperature distribution at the base. Conversely, refining the intermediate channel widths under constant total width promotes more uniform flow and wall temperature distributions. A Performance Evaluation Criterion for Non-uniform Channels (PECNC) was introduced to identify the optimal structure. Ultimately, structure VI, characterized by continuously refined intermediate widths, emerged as the optimal design for achieving uniform temperature distribution. A mathematical expression for calculating the optimal microchannel width distribution conducive to uniform temperature distribution was also established.

Two-Stage Robust Optimization of Integrated Energy Systems Considering Uncertainty in Carbon Source Load

Integrated Energy Systems (IESs) interconnect various energy networks to achieve coordinated planning and optimized operation among heterogeneous energy subsystems, making them a hot topic in current energy research. However, with the high integration of renewable energy sources, their fluctuation characteristics introduce uncertainties to the entire system, including the corresponding indirect carbon emissions from electricity. To address these issues, this paper constructs a two-stage, three-layer robust optimization operation model for IESs from day-ahead to intra-day. The model analyzes the uncertainties in carbon emission intensity at grid-connected nodes, as well as the uncertainty characteristics of photovoltaic, wind turbine, and cooling, heating, and electricity loads, expressed using polyhedral uncertainty sets. It standardizes the modeling of internal equipment in the IES, introduces carbon emission trading mechanisms, and constructs a low-carbon economic model, transforming the objective function and constraints into a compact form. The column-and-constraint generation algorithm is applied to transform the three-layer model into a single-layer main problem and a two-layer subproblem for iterative solution. The Karush–Kuhn–Tucker (KKT) condition is used to convert the two-layer subproblem into a linear programming model. A case study conducted on a park shows that while the introduction of uncertainty optimization increases system costs and carbon emissions compared to deterministic optimization, the scheduling strategy is more stable, significantly reducing the impact of uncertainties on the system. Moreover, the proposed strategy reduces total costs by 5.03% and carbon emissions by 1.25% compared to scenarios considering only source load uncertainty, fully verifying that the proposed method improves the economic and low-carbon performance of the system.

Research on performance of porous scaffold-based getter activated by induction heating and its application in MEMS device

Non-evaporable getter (NEG) is widely used in vacuum packaging. However, there are two main contradictions. Firstly, the contradiction between bonding temperature of the device and activation temperature of the getter results in the getter being activated first and then packaged, and cannot be repeatedly activated, which seriously reduces the adsorption capacity and life of the getter. Secondly, the contradiction between the small package volume and the large adsorption capacity, how to integrate large adsorption capacity getter in a small space is a tricky problem. In view of the above contradictions, a porous scaffold-based getter activated by induction heating was proposed in this paper, results show that when nickel plating is used as the induction heating layer, the temperature can quickly rise to 700 °C within 10 s, and 1 μm Ti getter can be fully activated for 7 min. The good periodicity of the temperature curves proved that the nickel layer has good repeatable heating characteristics. In addition, the adsorption performance of the getter was tested and characterized at device level. The device level characterization of optical deflection method proves the effectiveness of induction heating to activate getter, which lays a foundation for the application of getter on MEMS devices.

Heat and moisture transport characteristics in permafrost embankment under seasonal rainfall

Heat and moisture transport characteristics in permafrost embankment under seasonal rainfall

Microwave Heating Characteristics on Lipid Quality in Sterilized Rainbow Trout (Oncorhynchus mykiss) Using Designed Heating Processing.

The aim of this study was to simulate microwave heating characteristics to investigate the lipid quality in rainbow trout, including the impact of the heating rate, maximum temperature, and thermal processing level on the extent of lipid oxidation and on the fatty acid extraction coefficient. Increasing F0 from 3 to 6 min improved fatty acid retention at high heating rates but led to a decrease in the measured results at low heating rates. Elevated thermal processing levels and maximum temperatures were observed to intensify the oxidation. At F0 = 3 min, an increase in maximum temperature led to an increase in the total lipid extraction coefficient but a decrease in the fatty acid extraction coefficient. However, an increase in maximum temperature resulted in a decrease in both extraction coefficients when F0 was 6 min. The coefficient spectra of fatty acid extraction obtained from the microwave and traditional heat treatments showed nonparallel trends, confirming the presence of non-thermal effects during microwave thermal processing. In conclusion, compared to conventional heat treatment methods, microwave processing has significant potential for enhancing the lipid quality of ready-to-eat rainbow trout products and effectively reducing production costs.

Investigation of the heating characteristics of turbulent non-premixed gas combustion in the industrial-scale walking beam type reheating furnace

Oxygen-enriched combustion is widely used in industrial furnaces. To elucidate the multi-physics properties of reheating process, this study numerically explores the flow and combustion characteristics of syngas oxygen enrichment combustion in an industrial-scale walking beam type reheating furnace. The findings demonstrate that gas flow patterns at the furnace inlet primarily encompass the billet periphery, enhancing heat transfer efficiency. Oxygen-enriched combustion achieves lower temperature differences, higher heating temperature and CO2 emissions. Additionally, increasing levels of oxygen enrichment correlates with elevated temperatures, though the increments diminish progressively. Specifically, temperatures at the outlet of the preheating section range from 1100 K to 1200 K, with the middle region of the heating section displaying slightly lower temperatures compared to the areas adjacent to the burner. High temperature zones are primarily concentrated around the burners in soaking and heating sections. In terms of heating temperature and thermal uniformity, 30 % oxygen-enriched condition yields superior performance, evidenced by higher heating temperatures and reduced temperature differentials. Moreover, oxygen-enriched combustion enlarges CO2 emissions, with a 124.5 % enhancement observed. The lowest NO emission content at the outlet occurs during combustion with 21 vol% air and 45 vol% oxygen enrichment, however, these values remain relatively high. The insights derived from this study provide a foundational framework and guiding principles for furnace design and optimization of multi-gradient oxy-enriched combustion.

Multi-physical field analysis based on a multi-material mode stirrer and interlayer for microwave processing fluid

Microwave technology is widely recognized for its efficiency in the chemical, food and energy industries, and has attracted great attention due to its ability to induce both thermal and non-thermal effects. However, the use of microwave reactors often leads to thermal runaway phenomenon. To address this challenge, a multi-material mode stirrer has been integrated with a microwave reactor structured with an interlayer, and the materials of mode stirrer and interlayer inner wall have been changed to address issues related to temperature uniformity. The combined effects of multi-material mode stirrer and different material inner walls on the microwave heating characteristics have been studied by using the evaluated coefficient of temperature variation (COV) and the mean fluids temperature. It is discovered that: (1) the effect of mode stirrer on heating characteristics depends on its material and the coefficient of temperature variation of Aluminum-Alumina mode stirrer is reduced by 44 %; (2) under the action of mode stirrer, the corundum inner wall can improve the heating efficiency, but the glass inner wall has a poor effect on it; (3) changing the structure materials of the microwave reaction kettle has little effect on the heating efficiency and the combination of Polyethylene-Aluminum mode stirrer and silicon carbide inner wall can improve the heating uniformity.