Homogeneous Heating Research Articles

Heat application in live cell imaging.

Thermal heating of biological samples allows to reversibly manipulate cellular processes with high temporal and spatial resolution. Manifold heating techniques in combination with live-cell imaging were developed, commonly tailored to customized applications. They include Peltier elements and microfluidics for homogenous sample heating as well as infrared lasers and radiation absorption by nanostructures for spot heating. A prerequisite of all techniques is that the induced temperature changes are measured precisely which can be the main challenge considering subcellular structures or multicellular organisms as target regions. This article discusses heating and temperature sensing techniques for live-cell imaging, leading to future applications in cell biology.

Intense pulsed light-induced millisecond selective heat treatment for high-performance silicon anodes

Silicon, which is gaining prominence as a potential anode material, exhibits long-term cycle stability issues owing to volume changes during cycling. This study presents a meticulously designed Si anode that employs intense pulsed light (IPL) technology to simultaneously reduce carbon additives and construct an effective carbon quantum dot (CQD)-derived binder system. IPL, as a light-material interaction technique, offers a novel approach for selective heat treatment with remarkably short processing durations on the order of milliseconds. By comprehensively considering the geometric structure, optical characteristics, and thermal properties of each electrode component, heat transfer bridge (HTB) materials are introduced to ensure a homogeneous depth-directional heat treatment and to minimize binder decomposition in the IPL process. By employing HTB materials, the binder can reach a controlled target temperature for the condensation reaction between poly (acrylic acid) and the CQDs. Simultaneously, higher heat generation in the conductive carbon than in the binder leads to selective additional carbon reduction. This unique approach provides selective heat treatment, which cannot be achieved using conventional methods, resulting in a Si anode with excellent cyclic stability and rate capability. The versatility of the IPL technology is further demonstrated by applying it to relatively inexpensive Si microparticles.

Evaluating crown scorch predictions from a computational fluid dynamics wildland fire simulator

BackgroundCrown scorch—the heating of live leaves, needles, and buds in the vegetative canopy to lethal temperatures without widespread combustion—is one of the most common fire effects shaping post-fire canopies. Despite the ability of computational fluid dynamic models to finely resolve fire activity and buoyant plume dynamics including heterogenous 3D distributions of forest canopy heating, these models have had only limited use in simulating fire effects and have not been used to evaluate crown scorch. Here, we demonstrate a method of evaluating crown scorch using a computational fluid dynamics model, FIRETEC, and validate this approach by simulating the experiments that were used to develop Van Wagner’s 1973 crown scorch model.ResultsThe average scorch height prediction from FIRETEC compares well with the empirical model derived by Van Wagner, which is the most widely used empirical model for crown scorch. We further find that the 3D buoyant plume dynamics from a steady and homogeneous idealized heat source on the ground results in a spatially heterogenous crown scorch pattern reflecting complex heating dynamics that are best represented by percent scorch rather than height of scorch.ConclusionsThe ability of the computational fluid dynamics model to capture variation in crown scorch due to 3D buoyant plume dynamics provides direct links between forest structure, fire behavior, and fire effects that can be used by forest managers and researchers to better understand how fires result in crown damage under various environmental and management scenarios.

Investigation of the effect of rectangular winglet angles on turbulent flow and heat transfer of water/Cu nanofluid in a three-dimensional channel

This numerical simulation studies a homogenous and single-phase nanofluid's turbulent flow and heat transfer behavior in a three-dimensional rectangular microchannel. This study's main purpose is to investigate the use of rectangular winglet angles on flow path and its effect on turbulent flow regime and heat transfer parameters. In the current study, the Reynolds number, winglet attack angle (θ), and twisted angle range (α) (or Pitch angle) from 3000 to 12000, 30°≤ θ ≤ 60°, and 15°≤α ≤ 45°, respectively. Also, Cu nanoparticles with volume fractions of 0–4% are used in water as the base fluid. Results of this study show that heat transfer and flow physics of cooling fluid are affected by the variations of attack angle and winglet twist, and the creation of secondary flows leads to the mixture and deviation of flow. A decrease in the attack angle of the winglet causes the creation of strong vortexes and an increase in Nusselt number and heat transfer. In all investigated situations, with the angle of attack constant, increasing the twist angle can improve the Nusselt number between 11 and 18 percent. Also, increasing the angle of attack of the winglet from 30 to 60° can reduce the Nusselt number by 4–8 percent. The results indicate that changing the winglet angle increases the friction coefficient, and at higher Reynolds numbers, this parameter decreases. Also, by increasing Reynolds number, the ratio of friction coefficient to Nusselt number reduces, leading to the decrease of performance evaluation criterion (PEC).

Conversion of cobalt from spent LIBs to Co3O4 electrode material for application in supercapacitors

ABSTRACT The cathode material of lithium-ion batteries (LIBs) is endowed with valuable metals, such as cobalt. The improper treatment of these batteries pollutes the environment and causes enormous resource waste. Therefore, the recovery of valuable metals from spent LIBs has attracted widespread attention. In this study, Co3O4 electrode materials were prepared by a simple homogeneous precipitation method and heat treatment using a leaching solution of spent LIBs-positive electrode material as the cobalt source. The crystal structure and morphology of the products were examined at different annealing temperatures, and their electrochemical performance was analyzed. The results show that low-temperature annealing contributes to grain refinement. The Co3O4 material prepared at 300°C annealing temperature has a rod-like structure with distinct pores and a specific surface area of 58.98 m2 g−1. Furthermore, electrochemical performance testing reveals that Co3O4 prepared at 300°C displays the best electrochemical performance as an electrode material, with a specific capacitance of 97.93 F g−1 and a cycle retention rate of 79.12% after 500 charge–discharge cycles. These findings demonstrate the feasibility of recycling valuable metal cobalt from spent LIBs cathode materials to produce Co3O4 materials for use as supercapacitor electrode materials, opening up new avenues for the recycling and utilisation of spent LIBs.

Copper - nickel electro-explosive powder feedstocks for extrusion-based additive manufacturing

The average sizes of copper and nickel nano- and microparticles formed at exploding wires in the range of inhomogeneous and homogeneous heating have been established. The average size of nanoparticles grows, and that of microparticles decreases when the value of energy input into wires reaching E ≈ 0,5Es (Es - sublimation energy). While E > 0.5Es the dependence of the average sizes of nano- and microparticles is weakly expressed. The viscosity of feedstocks increases as the proportion of nanoparticles in the powder increases and their size decreases. At equal dispersity and mass content of particles in the polymer, the feedstock viscosity has been found to depend on the adsorption behavior of metals. The analysis of temperature dependence of the feedstock viscosity based on copper and nickel powders has shown that the optimum values of E/Es for one-stage production of micro-nanoparticle powders by the exploding wires lie in the range of 0.4 … 0.7.

Densification, mechanical properties, and oxidation behavior of spark plasma sintered TaB2-SiC-BN composites

TaB2-30 vol% SiC binary and TaB2-SiC-BN ternary composites with varying hexagonal boron nitride (BN) ratios (1–3–5–7–10 vol%) were consolidated by spark plasma sintering at 1650℃ under 40 MPa for 5 min. The densification characteristics, phase formation, mechanical properties, and oxidation behavior of both the TaB2-SiC and TaB2-SiC-BN composites were investigated. No new peaks other than the characteristic peaks associated with the starting materials were observed. Among all compositions, that containing 27 and 3 vol% of SiC and BN, respectively, exhibited the highest densification, ∼99.9 %. Homogeneous heating during sintering due to the thermal conductivity of hexagonal BN, along with the reduction in porosity by BN entering between TaB2 and SiC grains improved the densification behavior of the ternary composites. Besides, the incorporation of BN led to significant improvements also on the fracture toughness, which increased by ∼46 %. In ternary composites, crack deflection and branching were identified to be effective toughening mechanisms. The addition of BN had a negligible effect on Vickers hardness when agglomeration was minimal. The oxidation resistance at 1100 and 1200 °C increased with the addition of BN.

Rapid Microwave Method to Enhance the Characteristics of Fe3O4 and Fe3O4/SiO2 Nanoparticles

The application of nanoparticles can increase the number of products and protect against the deadly effects of industrial processes. Generally, nanoparticle technology offers numerous benefits, including reduced energy consumption and waste generation. Therefore, this study aimed to prepare Fe3O4 and Fe3O4/SiO2 nanoparticles using rapid microwave method. The instruments used for analysis included x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), vibrating sample magnetometer (VSM), scanning electron microscopy-dispersive x-ray (SEM-EDX), and ultraviolet-visible diffuse reflectance spectroscopy (UV-DRS). The combustion process was carried out using a microwave to produce sufficient energy for forming Fe3O4 nanoparticles. The homogeneous heating distribution process in the raw material effectively formed different initial phases and nanoparticle morphologies within a few minutes. The results showed that the application of rapid and efficient microwave provided good monodispersity, uniform core-shell structure, and high magnetization. The calculated optical bandgap values for Fe3O4 and Fe3O4/SiO2 ranged from 1.77–2.33 eV. According to magnetic analysis, Fe3O4 nanoparticles showed superparamagnetic behavior at room temperature with a value of 32–40 emu/g, while Fe3O4/SiO2 powder had 9–23 emu/g. The analysis of SEM-EDX showed that SiO2 had the potential to prevent particle aggregation and stabilize the nanoparticles prepared. Moreover, further study is recommended to modify the product with other materials, such as TiO2, for photocatalysts.

Towards highly homogeneous self-regulating heating of smart nanocomposites

Smart self-regulating heating devices utilising the positive temperature coefficient (PTC) effect have shown great potential in advancing applications across healthcare, soft robotics, and energy-efficient manufacturing. However, achieving homogeneous resistive heating within such temperature self-controllable nanocomposites remains a significant challenge, falling short of meeting the requirements of advanced heating systems. This study explores and evaluates multiple innovative strategies aimed at enhancing the temperature uniformity of PTC nanocomposites. By identifying and analysing the primary physical mechanisms behind the inhomogeneous heating observed in conductive polymer composites, we propose a series of targeted strategies, ranging from customised material formulations to novel electrode configurations. Recycled carbon fibres have also been explored and upcycled as an effective solution for homogenous self-regulating heating. Through a comprehensive analysis of experimental results, the effectiveness of each strategy has been evaluated with a significantly improved temperature uniformity (from 32.6 to 2.7 % variation at 125 °C), providing valuable insights for the design and development of advanced self-regulating heating devices based on conductive polymer nanocomposites, while offering promising prospects for achieving more energy-efficient and uniform heating in various industrial applications.

Homogeneous Heat Transfer During Freeze-Drying Using Cyclic Olefin Polymer Vials

In pharmaceutical freeze-drying processes, batch homogeneity is an important quality attribute. In this context, the edge-vial-effect is a challenging phenomenon. Shortly, this effect describes that vials at the edges of the shelf dry faster and at a higher temperature compared to vials in the middle of the shelf. Studies by Ehlers et al. revealed that this effect mainly origins from the number of neighbor vials cooling each other, which is reduced for vials in corners and edges compared to vials in the middle. Due to the reduced heat transfer in cyclic olefin polymer (COP) vials, the adverse edge-vial-effect should be greatly reduced allowing a better batch uniformity. In this focused study, glass and COP vials are compared regarding this effect on a fully loaded shelf. A reference experiment with vials placed at distance using a specially designed frame is presented as well.

Role of rotational and divergence effects induced by wind turbines wakes on near-ground air warming

Various studies, involving numerical simulations, satellite measurements, and field measurement campaigns, have demonstrated that wind turbine wakes can lead to changes in near-ground air temperature. To investigate these phenomena an Actuator Disk with Rotation (ADR) is implemented within the LES non-hydrostatic atmospheric model Meso-NH and validated using the NewMEXICO wind tunnel measurements and the VERTEX field measurement campaign. The NewMEXICO case allows the aerodynamic validation of the approach, especially the effect of the wake on wind speed components. On the VERTEX case, meteorological effects of wind turbines are studied under various atmospheric stability conditions through the application of homogeneous sensible heat fluxes at the ground level. Results show wake-related warming and cooling near the ground for stable and unstable conditions respectively, and no significant change for neutral conditions. These results show a good tendency agreement with the VERTEX campaign’s measurements. The comparison between an Actuator Disk with No Rotation (ADNR) and an ADR simulation show the dual contribution of the rotation of the wake and the growth of the stream tube on the temperature change in the wake but also on the near-ground air temperature.

Liouville models of particle-laden flow

Langevin (stochastic differential) equations are routinely used to describe particle-laden flows. They predict Gaussian probability density functions (PDFs) of a particle's trajectory and velocity, even though experimentally observed dynamics might be highly non-Gaussian. Our Liouville approach overcomes this dichotomy by replacing the Wiener process in the Langevin models with a (small) set of random variables, whose distributions are tuned to match the observed statistics. This strategy gives rise to an exact (deterministic, first-order, hyperbolic) Liouville equation that describes the evolution of a joint PDF in the augmented phase-space spanned by the random variables and the particle position and velocity. Analytical PDF solutions for canonical models of particle-laden flows serve to establish a relationship between the Langevin and Liouville approaches. Finally, our framework is used to derive a new analytical PDF model for fluidized homogeneous heating systems.

Fabrication of carbon fiber/cement composites with controllable precise patterned structures via facile computerized embroidery

Carbon fibers exhibit good electrothermal performance; however, they break easily during the weaving process. This study used a facile computerized embroidery process to design and fabricate carbon fibers with controllable and precise patterned structures. The obtained carbon fiber/cement composites (CFCs) exhibited excellent electrothermal performance (100 ℃ under 30 V), low energy consumption (400 mW/℃), and homogeneous heat distribution with a unique heating element (carbon fibers) structure. The difference between the maximum and average surface temperatures improved, and the surface heat distributions of the CFCs under different structures were determined using a finite element simulation. CFCs with different complex heat element structures were successfully fabricated, and the mechanism regulating the heat distribution of the CFCs was revealed. Embroidery technology provides a novel strategy for the fabrication of carbon fiber/cement composite materials with a controllable carbon fiber structure, thereby significantly broadening the application of cement composites for electrothermal applications.

Inactivation of Salmonella Typhimurium and Listeria monocytogenes in dairy systems: Effect of fat and food matrix structure under radio frequency heating

The effect of two food intrinsic factors (fat content, matrix structure) on the radio frequency (RF) inactivation of Salmonella Typhimurium and Listeria monocytogenes was investigated in dairy model systems: i.e., liquids with 0.08% and 5.9% fat and gels with 0.08% and 5.9% fat. In the liquid, higher fat content resulted in higher inactivation for both microorganisms. In gels, inactivation rate was higher with the lower fat content, while opposite behaviour occurred for L. monocytogenes above 70 °C. A gel matrix resulted in higher inactivation of S. Typhimurium, while complex temperature-dependent behaviour was present for L. monocytogenes. Sublethal injury was most significant for L. monocytogenes at 5.9% fat content and high temperatures. Overall, fat content and matrix structure impacted the microbial inactivation during RF heating and should be taken into account when designing novel RF heating food decontamination strategies. Industrial relevanceRadio frequency (RF) heating as a food processing technology has seen increased industrial application in recent years. The technology allows a more homogeneous heating of food products and also enables the treatment of low-moisture foods. The increased knowledge on the influence of fat content and food structure on RF thermal inactivation will lead to the development of improved and more efficient treatments.

Numerical investigation of heat transfer and temperature distribution in a Microwave-Heated Heli-Flow reactor and experimental validation

Microwave-heated flow systems (MWFSs), offering improved process control, enhanced product yields, and the potential for scalable and sustainable manufacturing routes, have gained significant popularity in continuously manufacturing nanomaterials and their hybrids. Temperature control in a microwave zone can maintain fine control over the manufactured materials' properties; however, the current state-of-the-art designs lack monitoring of the temperature distribution throughout the flow reactor. Herein, a unique model of numerical estimations of temperature distribution in a microwave-heated system featuring a helical flow milli-reactor, Heli-Flow, is described and validated by experimentally acquired temperature profiles. The proposed numerical model accurately predicts the temperature profile along the Heli-Flow and the steady-state outlet temperature at the MW cavity's exit. The helical design of the reactor promotes homogeneous heating and eliminates orientation-related discrepancies. The maximum outlet temperatures achieved at different microwave powers and FRs align well with expected trends. The modeled temperatures closely match the experimental and analytical measurements, indicating the effectiveness of the simulation approach. This research contributes to understanding temperature distribution in MWFSs and offers insights for optimizing nanomaterial synthesis and other applications.

A Facile Approach to Produce Activated Carbon from Waste Textiles via Self-Purging Microwave Pyrolysis and FeCl3 Activation for Electromagnetic Shielding Applications.

This study aims to convert composite textile structures composed of nonwoven and woven fabrics produced from cotton-jute wastes into activated carbon textile structures and investigate the possibilities of using them for electromagnetic shielding applications. To this end, the novel contribution of this study is that it shows that directly carbonized nonwoven textile via self-purging microwave pyrolysis can provide Electromagnetic Interference (EMI) shielding without any processing, including cleaning. Textile carbonization is generally achieved with conventional heating methods, using inert gas and long processing times. In the present study, nonwoven fabric from cotton-jute waste was converted into an activated carbon textile structure in a shorter time via microwaves without inert gas. Due to its polar structure, FeCl3 has been used as a microwave absorbent, providing homogeneous heating in the microwave and acting as an activating agent to serve dual purposes in the carbonization process. The maximum surface area (789.9 m2/g) was obtained for 5% FeCl3. The carbonized composite textile structure has a maximum of 39.4 dB at 1 GHz of EMI shielding effectiveness for 10% FeCl3, which corresponds to an excellent grade for general use and a moderate grade for professional use, exceeding the acceptable range for industrial and commercial applications of 20 dB, according to FTTS-FA-003.

Numerical Simulation and Sensitivity Analysis Using RSM on Natural Convective Heat Exchanger Containing Hybrid Nanofluids

This work presents a numerical analysis for exploring heat transfer phenomena in an enclosed cavity using magnetohydrodynamics natural convection. Because of the numerous real-world applications of nanofluids and hybrid nanofluids in industrial and thermal engineering developments, hybrid nanofluids are used as fluid mediums in the fluid field. A hexagonal-shaped heat exchanger is taken with two circular surfaces along the middle part. The upright circular surface acts as a homogeneous heat source, while the lower circular surface functions as a heat sink. The remaining portions of the adjacent walls are thermally insulated. The copper (Cu) and titanium dioxide (TiO2) nanoparticles are suspended into water to make a hybrid nanofluid. For solving the corresponding governing equations, the weighted-residual finite element method is applied. To explain the major outcomes, isotherms, streamlines, and many others 2D and 3D contour plots are involved graphically with a physical explanation for different magnitudes of significant parameters: Rayleigh number 103≤Ra≤106, Hartmann number 0≤Ha≤100, and nanoparticle volume fraction 0≤ϕ≤0.06. The novelty of this work is to apply response surface methodology on the natural convective hybrid nanofluid model, to visualize 2D and 3D effects, and to study the sensitivity of independent parameters on response function. Due to the outstanding thermal properties of the hybrid nanofluid, the addition of Cu and TiO2 nanoparticles into H2O develops the heat transfer rate to 35.85% rather than base fluid. Moreover, a larger magnitude of Ra and the accumulation of mixture nanoparticles result in the thermal actuation of a hybrid nanofluid. With greater magnetic impact, an opposite response is exhibited.

Numerical analysis of jet impingement cooling with elongated nozzle holes on a curved surface roughened with V-shaped ribs

Numerical studies were performed in this study to analyze the effect of dimensionless elongated injection holes (G/d = 0.5, 2.0, 4.0, 8.0) on heat and flow characteristics on rib-roughened surfaces with an array of inclined impingement jets. Experimental and numerical data from existing literature were used to validate the numerical solution procedure’s heat transfer and flow characteristics in the semicircular test section. The turbulence equations were solved using the SST k-ω turbulence model by varying the Reynolds number from 5000 to 25,000. The curvature effect and staggered array pattern created an additional stagnation region between adjacent impinging jets on smooth surfaces, leading to a low heat transfer zone. Rectangular cross-sectional V-shaped ribs (VSR) were placed in regions where the stagnation point occurs to eliminate this disadvantage. The effect of different normalized rib heights (Hr/d = 0, 0.2, 0.3, 0.4) and rib angles (α = 30°, 45°, 60°, 90°) on the curved surface was also investigated to increase convective heat transfer performance and achieve more homogenous heat transfer distribution by relatively reducing the effect of thermal stresses. Flow properties, area-averaged and local Nusselt number variations on smooth and ribbed surfaces, and the thermal performance criterion (TPC) were investigated in detail. The results indicated an increase in overall heat transfer and a more evenly distributed measurement region compared to the conventional (unextended jet and smooth surface) jet impingement configuration. The most significant heat transfer enhancement from combining the elongated jets with VSR was 47.23% at Hr/d = 0.2 by reducing the G/d to 0.5. In addition, the highest TPC was determined as 1.07 on the proposed model with G/d = 2.0 and Hr/d = 0.2 at Re = 25,000.

An innovative end-to-end PINN-based solution for rapidly simulating homogeneous heat flow problems: An adaptive universal physics-guided auto-solver

In contemporary heat flow computations, the widespread application of deep learning, specifically Physical Informed Neural Networks (PINN), has been noted. However, existing PINN methods often exhibit limited applicability to specific operational conditions and are hindered by prolonged training times, rendering them unsuitable for engineering scenarios requiring frequent changes in operational parameters. This study addresses the imperative of enhancing the computational efficiency of conventional PINN methodologies and introduces an innovative end-to-end PINN-based solution—Adaptive Universal Physics-Guided Auto-Solver (AUPgAS) for swift simulation of homogeneous heat flow problems. AUPgAS introduces the operational condition as a variable within the neural network, thereby enhancing the model's versatility in addressing homogeneous problems. Simultaneously, AUPgAS refines training accuracy through the incorporation of adaptive sampling methods. The efficacy of this method is demonstrated through validations on two application cases of laminar incompressible flow with viscosity, namely the flow around a cylinder and the flow around two cylinders. After training, the model demonstrates the capability to predict pressure and velocity fields of the flow around a single cylinder in different locations in case Ⅰ, as well as simulate the flow field when the distance between two cylinders rapidly changes in case Ⅱ. Comparative analyses with traditional computational fluid dynamics methods show that the AUPgAS greatly reduces the solution time, the average time taken by the trained AUPgAS to solve for each problem is 3.4 s, which is a significant improvement in efficiency compared to the average time taken by the traditional fluid dynamics methods, which is 910 s. Furthermore, the agreement of the results obtained by AUPgAS with the reference solution is commendable, with a minimum average error of 13.55%. This end-to-end approach presents an innovative and efficient solution for the rapid simulation of homogeneous heat flow problems, offering promising advancements in the realm of engineering computational efficiency.

Stress intensity factors and full-field stresses for a hypocycloid-type crack within a thermo-elastic material

This study focuses on the failure analysis of a hypocycloid-type crack within a thermo-elastic material. Employing the conformal mapping method, analytical continuation theorem, and principle of superposition, the explicit general solution for stress intensity factors (SIFs) associated with an arbitrary-edged hypocycloid-type crack is determined analytically under the influence of remote homogeneous heat flux and mechanical load. The superposition method combines stress functions and SIFs for two distinct loading conditions. The outcomes of the normalized SIFs are affected by the magnitude and orientation of the heat flux and mechanical load. A full-field stress distribution is provided to account for variations in SIFs. Certain combinations of loads lead to maximum SIF values, rendering the system highly vulnerable to damage, while two specific scenarios inhibit crack propagation, thereby reducing the risk of structural failure.