Transfer Characteristics Research Articles

Achieving High Performance with Less Energy Consumption: Intermittent Ultrasonic-Mediated Operation Mode for Fe/V Non-Aqueous Redox Flow Battery

Deep eutectic solvents (DESs) have attracted much attention as sustainable electrolytes for redox flow batteries. Despite the tremendous advantages of DES-based electrolytes, their high viscosity property has a negative effect on their mass transfer, limiting current density and power density. The ultrasonic effect has been demonstrated as an efficient strategy to improve mass transfer characteristics. Incorporating ultrasonic waves into a deep eutectic solvent (DES) electrolyte enhances the mobility of redox-active ions, thereby accelerating the reaction dynamics of the Fe(III)/Fe(II) redox pair. This enhancement makes it suitable for use in non-aqueous electrolyte-based redox flow batteries. However, it is necessary to consider the loss of ultrasonic on the internal structure of the battery, as well as the loss of battery component materials and ultrasonic energy consumption in practical applications. Moreover, the continuous extension of the duration of ultrasonic action not only hardly leads to a more significant improvement of the battery performance, but is also detrimental to the energy and economic savings. Herein, intermittent ultrasound is used to overcome the quality transfer problem and reduce the operating cost. Good electrochemical performance enhancement is maintained with a roughly 50% reduction in energy consumption values. The mechanism as well as the visualization of the pulsed ultrasonic field on each half cell has been envisaged through fundamental characterization. Finally, the feasibility of interrupted ultrasonic activation applied to Fe/V RFB using DES electrolytes has been demonstrated, demonstrating similar behavior with continuous ultrasonic operation. Therefore, the interrupted ultrasonic field has been found to be a more effective operation mode in terms of energy cost, avoiding alternative undesirable effects like overheating or corrosion of materials.

Computational role of homogeneous–heterogeneous chemical reactions and a mixed convective ternary hybrid nanofluid in a vertical porous microchannel

Abstract This article mainly scrutinizes the heat transfer and flow characteristics of a mixed convection ternary hybrid nanofluid in a porous microchannel considering the catalytic chemical reaction and nonuniform heat absorption/generation. Using appropriate similarity transformations, the modeled equations are converted into reduced ones and then solved via the Runge–Kutta–Fehlberg 4th/5th order method. To strengthen this analysis, the convection mechanism has been deployed. The effect of pertinent physical parameters on the fluid motion and thermal field is displayed, including some important engineering variables like the Nusselt number, Sherwood number, and drag force. The novel outcomes display that the flow reduces with porous permeability and nanoparticle volume fraction. The temperature of the nanofluid improves with nonuniform heat absorption/generation. The concentration decreases in the presence of both homogeneous and heterogeneous reaction intensities. The heat transfer rate enhances for the Eckert number, and a similar influence on the mass transfer rate is noticed for homogeneous reaction parameters. Further, the drag force declines for the Grashof number. The outcomes show that, in all cases, the ternary hybrid nanofluid shows a greater impact than the nanofluid. The attained findings represent applications in the era of cooling and heating systems, thermal engineering, and energy production.

Optimization of heat transfer in a double lid-driven cavity with isoperimetric heated blocks using GFEM.

This article is concerned with the examination of flow dynamics and heat transfer characteristics in a 1:4 double lid driven cavity in presence of isoperimetric heated blocks of various shapes. The focus is to identify the optimal shape that enhances the heat transfer in a tall cavity. The parametric settings are chosen in such a way that all the convection regimes including natural, forced and mixed convection could be generated. This cavity has lids positioned at the top and bottom, moving in opposite directions along the x-axis. The physical system is represented as a set of coupled partial differential equations incorporating the rheological properties of the power-law fluids (PL). The governing equations in conjunction with various non-dimensional physical parameters are simulated via Galerkin's Finite Element Method (GFEM) on a very fine hybrid grid. The study includes the computation of the Kinetic Energy and Average Nusselt number to determine the optimal shape. It is concluded that the circular block is superior to the other two in terms of heat transmission efficiency.

Heat Transfer Characteristics of Borehole Briquette Samples in Liquid CO2 High-Temperature Steam Synergistic Impact Process

Heat Transfer Characteristics of Borehole Briquette Samples in Liquid CO₂ High-Temperature Steam Synergistic Impact Process

Uncertainty analysis of MHD oscillatory flow of ternary nanofluids through a diverging channel: a comparative study of nanofluid composites

Purpose This study aims to investigate the heat and mass transfer characteristics of a temperature-sensitive ternary nanofluid in a porous medium with magnetic field and the Soret–Dufour effect through a tapered asymmetric channel. The ternary nanofluid consists of Boron Nitride Nanotubes (BNNT), silver (Ag) and copper (Cu) nanoparticles, with a focus on understanding the thermal behaviour and performance across mono, hybrid and tri-hybrid nanofluids. This paper also examines the thermal behaviour of MHD oscillatory nanofluid flow and carries out an uncertainty analysis of the model using the Taguchi method. Design/methodology/approach The governing equations for this system are transformed into coupled linear partial differential equations using non-similarity transformations and solved numerically with the Crank–Nicolson scheme. The impact of temperature sensitivity at three distinct temperatures (5°C, 20°C and 60°C) is incorporated to analyse variations in viscosity and Prandtl number. The study also examines the combined effects of Soret–Dufour numbers and thermal radiation on heat and mass transfer within the nanofluid. Findings The results demonstrate that the inclusion of BNNT, Ag and Cu nanoparticles significantly enhances heat and mass transfer rate, with copper nanoparticles showing superior performance in terms of skin friction and heat transfer rates. The Soret and Dufour effects play critical roles in modulating heat and mass diffusion within tri-hybrid nanofluids. The study reveals that temperature sensitivity alters heat and mass transfer characteristics depending on the temperature range, with pronounced variations at elevated temperatures. The influence of thermal radiation and the Peclet number is found to significantly impact temperature distribution and overall heat transfer performance within the asymmetric channel. Originality/value To the best of the authors’ knowledge, this study is the first to analyse the heat and mass diffusion in a ternary nanofluid composed of BNNT, Ag and Cu nanoparticles, considering porous media, oscillatory flow and thermal radiation within a tapered asymmetric channel. The research extends to a novel examination of temperature sensitivity in mono, hybrid and tri-hybrid nanofluids at varying temperature gradients. Furthermore, a comparative analysis of skin friction and heat transfer rates between copper, alumina and ferro composites is presented for optimising the nanofluid performance.

Rotating twisted tape turbulators and CuO nanofluid synergy: investigating heat transfer characteristics in tubular systems

Rotating twisted tape turbulators and CuO nanofluid synergy: investigating heat transfer characteristics in tubular systems

Design and Development of a Quad mode Circular Millimeter-Wave Patch Antenna for Breast Tumour Size Detection and Localization

In this study, we present the development of an antenna based on millimeter-wave specifically designed for performance in breast tumour detection and localization. A quad – mode circular microstrip antenna is engineered to function at millimeter-wave frequencies of 30 GHz and 40 GHz, focusing on accurate tumor size & location. At 30 GHz and 40 GHz, facilitating effective penetration through breast tissue and enabling precise tumor localization. The differential dielectric characteristics of malignant and normal breast tissues provide the basis for the detection of breast cancers using mm-wave imaging. Using quarter mode circular patch antennas, this method sends and receives pulses that travel through the breast at various points. The tumor's location and size are then determined by receiving the waves from the breast. Due to their strong scattering properties, malignant tumors can be identified by their transfer characteristics in the reflected signals they receive. The study also looks at how the tumor's size and location in relation to the antenna affect detection efficiency. These results suggest that mm wave planar antennas are useful for locating and detecting tiny breast cancers, offering a viable method for breast cancer detection.

Engineering Charge Transfer Characteristics in ZnO NRs/Ag2O NPs p-n Heterojunctions: Toward Highly Efficient and Recyclable Photocatalysts.

Staggered gap p-n heterojunction ZnO nanorods/Ag2O nanoparticles, a paradigm of photocatalysts, were developed via engineering the hydrothermal and coprecipitation method. Under simulated sunlight, the photocatalytic characteristics of ZnO/Ag2O(Zn/A) heterojunctions with varying mole ratios (from 8:1 to 8:4, named Zn/A-1-Zn/A-4) were systematically evaluated through the degradation of methylene blue (MB). The influence of key experimental variables, including photocatalyst concentration, MB concentration, and solution pH, on the photocatalyst performance was further analyzed. The incorporation of Ag2O enhanced visible-light absorption, improved electron-hole separation efficiency, and significantly improved the photocatalytic recyclability of the Zn/A heterojunctions. Additionally, metallic Ag generated during photodegradation was found to enhance the photocatalytic activity further. Kinetic studies indicated that the photocatalytic degradation of MB followed pseudo-first-order kinetics, with the Zn/A-3 heterojunction showing the highest photocatalytic activity, achieving a degradation rate constant (k) of 0.028 min-1. Scavenger experiments confirmed that •OH radicals, holes (h+), and superoxide radicals (•O2-) were the primary reactive species involved in the degradation process. The photocatalytic mechanism was identified as a Z-scheme charge transfer system, facilitating efficient charge separation. Moreover, the Zn/A-3 heterojunction exhibited remarkable recyclability, retaining >91% of the photocatalytic activity after five cycles. This study demonstrates the potential of Zn/A heterojunctions for practical applications in industrial wastewater treatment using solar energy.

Optimization Conditions for High-Power AlGaN/InGaN/GaN/AlGaN High-Electron-Mobility Transistor Grown on SiC Substrate

In this study, we aimed to propose an optimal structure for an AlGaN/InGaN/GaN/AlGaN/SiC HEMT by investigating how the breakdown voltage varies with the thickness and composition of the InGaN layer. The breakdown voltage was shown to be highly dependent on the In composition. Specifically, as the In composition increased, the breakdown voltage rapidly increased, but it exhibited saturation when the In composition exceeded 0.06. Therefore, it is desirable to maintain the In composition at or above 0.06. The variation in breakdown voltage due to thickness was relatively small compared to the variation caused by In composition. While the breakdown voltage remained nearly constant with increasing thickness, it began to decrease when the thickness exceeded 10 nm. Hence, the thickness should be kept below 10 nm. Additionally, as the In composition increased, the subthreshold swing (SS) also increased, but the drain current value was shown to increase. On the other hand, it was observed that the SS value in the transfer characteristics and the current–voltage characteristics were almost unaffected by the thickness of the InGaN layer.

Characteristics of induced magnetic field on the time-dependent MHD nanofluid flow through parallel plates

Abstract The heat transfer characteristics of an unsteady magnetohydrodynamic flow through non-conducting infinite vertical parallel plates are presented in this investigation. The flow is subjected to an induced magnetic field, and the base fluid water contains carbon nanotubes (CNTs), in particular multi-wall carbon nanotubes, to present the behaviour of the nanofluid. The aim is to examine the effect of the applied magnetization and CNT concentration on the heat transport performance of the system. However, suitable transformation rules are adopted for the re-designing of the proposed design model into its non-dimensional form. This transformed system is then solved analytically following the standard transformations. The influence of key parameters, including the Hartmann number (Ha), the angle of inclination of the magnetic field, thermal buoyancy, heat source, and the concentration of CNTs in the nanofluid, on the flow phenomena is analysed. The consequences reveal that the occurrence of the inclined magnetic field affects the flow and heat transfer characteristics significantly. Additionally, the introduction of CNTs to the nanofluid enhances the heat transfer performance due to their unique thermal properties. The study demonstrates that enhanced Ha and CNT concentration augments the heat transfer rate.

Study on the Effect of Heat Transfer Characteristics of Energy Piles

The thermal performance of energy piles equipped with new metal fins to improve heat transmission is examined in this research. The solid heat transfer module of COMSOL Multiphysics was used to create a 2D numerical model of the energy pile, utilizing the energy pile at a field test site in Nanjing as an example. By contrasting the experimental data, the COMSOL Multiphysics model’s correctness was confirmed. After that, a new kind of energy pile fin was created to improve the heat transfer of the pile. The impact of the new fin type on the energy pile’s heat transfer efficiency was assessed, and the temperature change within the soil surrounding the pile before and after the fin was set was examined by contrasting the parameters of pipe configuration, buried pipe depth, and concrete thermal conductivity. The results indicate that after setting the fins to run for 336 h, the temperature of the concrete area increases by 10.8% to 12.3%, and the temperature of the region surrounding the pile increases by 5.3% to 8.7% when the tube diameter is chosen to be between 20 and 40 mm; The fins maximize the heat transfer temperature between the surrounding soil and the concrete, and as the tube diameter increases, the temperature drops. For 336 h of pile operation, the temperature of the concrete may be raised by 10.8% to 12.3% after the fins are set, and the temperature around the pile can be raised by 5.3% to 8.7%. The heat transmission efficiency of the energy pile can be improved by raising the temperature of the soil surrounding the pile through an increase in the concrete’s thermal conductivity; however, the degree of improvement diminishes as the conductivity rises. It is intended that this study will offer insightful information on the best way to design energy pile heat transfer efficiency.

Synergetic Modulation of Electronic Properties of Cobalt Oxide via "Tb" Single Atom for Uphill Urea and Water Electrolysis.

Exploring single-atom (SA) catalysts in hybrid urea-assisted water electrolysis offers a viable alternative to both Hydrogen (H2) generation and polluted water treatment. However, the unfavorable electronic stabilization, low SA content, intrinsically slow kinetics, and imbalanced adsorption-desorption steps are the bottleneck for its scale-up implementation. Herein, a rare-earth Terbium single atom (TbSA) is topologically stabilized on defect-rich Co3O4 (TbSA@d-Co3O4) by Tb─O co-ordination for urea oxidation reaction (UOR) and H2 evolution reaction (HER). Benefitting from the strong TbSA interaction with the d-Co3O4, the TbSA@d-Co3O4 achieves a 10mAcm-2 current density at 1.27V and -35mV for UOR and HER, respectively. Remarkably, when TbSA@d-Co3O4 is applied as a bi-functional catalyst in a two-electrode system, it merely requires 1.22V to acquire 10mAcm-2 with excellent operational stability for 100 h. The hybrid electrolyzer can be successfully empowered by the triboelectric nanogenerator, AA battery, and solar panel with a nominal potential of 1.5V. The mechanistic investigation predicts "TbSA" insertion in d-Co3O4 lowered the potential determining step, attributed to balanced reaction energetics for adsorption-desorption of intermediates and favorable charge transfer characteristics for UOR. This work offers a new paradigm to explore the catalytic properties of rare-earth "f-block" elements to create advanced electrocatalysts via structural modulation.

Computational supported experimental insights in adsorption of Congo Red using ZnO/doped ZnO in aqueous solution

The rapid growth of industrialisation has led to the discharge of harmful effluents into water bodies, severely disrupting the balance of ecosystems. The detection and removal of dyes from wastewater remains a significant challenge. In this study, we report the synthesis of zinc oxide (ZnO) and its doped derivatives through a facile chemical method, followed by comprehensive characterisation and analysis to assess their potential in various applications. The structural properties of the synthesised materials were confirmed by X-ray diffraction (XRD), which verified their crystalline nature and phase purity. Morphological analysis using field emission scanning electron microscopy (FE-SEM) coupled with energy dispersive X-ray analysis (EDAX) revealed well-defined nanostructures and uniform elemental distribution. The adsorption ability of the synthesized adsorbents was investigated through electrochemical methods, cyclic voltammetry and Tafel plots, which demonstrated enhanced conductivity and charge transfer characteristics. Additionally, theoretical studies through molecular modelling and molecular dynamic simulations were employed to elucidate the interactions between Congo red molecules and the surface of the synthesized compounds. Adsorption experiments were conducted to evaluate the efficacy of ZnO and its doped variants as adsorbents. To investigate any structural or functional changes after dye adsorption FTIR and XRD were compared, provided a deeper insight into the adsorption mechanism. This multi-faceted approach highlights the potential of ZnO-based materials for effective wastewater treatment and other environmental applications.

Computational study with neural networks to double diffusion in Prandtl thermal nanofluid flow adjacent to a stretching surface design with numerical treatment

The study focuses on the implementation of neural networks in analyzing the behavior of Prandtl nanofluid near a extending surface in the existence of dual diffusion. The research investigates the merged consequence of thermal and concentration gradients on the fluid flow and heat transfer characteristics using advanced computational techniques. The investigation delves into the phenomenon of double diffusion in the flow of Prandtl nanofluid near a stretching surface (DD-PNSS), employing the Levenberg-Marquardt scheme with Artificial Neural Networks (LMS-ANNs). The application of similarity variables converts the non-linear partial differential equations into non-linear ordinary differential equations. Through the application of the Lobatto IIIa formula in a three-stage process, various data sets are generated for the LMS-ANNs by varying parameters such as the Prandtl fluid parameter ([Formula: see text]), Prandtl number (Pr), Brownian motion parameter (Nb), thermophoresis parameter (Nt), and Dufour-solutal Lewis number (Ld). The range of parameter α is from 2 to 3.5, parameter β from 0.1 to 0.9, Nb is from 0.1 to 0.4, Nt is from 0.1 to 0.7, Le is from 1 to 3 and Ld is from 0.1 to 0.5. The intrinsic behavior of embedded parameters on dimensionless velocity, temperature, solutal concentration, and nanoparticle concentration profiles is graphically evaluated. The proposed LMS-ANNs model is meticulously tested, validated, and trained using a multi-stage approach, and its performance is compared to established references to ensure its reliability. The effectiveness of the suggested LMS-ANNs model is further affirmed through regression analysis, Mean Squared Error (MSE) evaluation, and histogram studies, showcasing an exceptional accuracy level ranging from 10−08 to 10−10, setting it apart from alternative approaches and reference models.

Study on heat transfer law of low temperature oxidation of coal under convection condition

Coal oxidation in the goaf generates heat accumulation influenced by airflow, leading to heat transfer within the porous coal structure. This study experimentally investigates the heat transfer characteristics of coal under convective conditions. A temperature migration rate measurement device was developed, and a formula for calculating the temperature migration rate was derived using the steady-state heat conduction differential equation and experimental data. The study examines the effects of temperature and airflow on the temperature migration rate and heat transfer characteristics. The experimental results indicate that the heat transfer effect of coal at low temperatures is minimal and volatile. As the temperature increases, efficiency improves, and heat transfer stabilizes. Airflow facilitates coal's heat transfer, causing the temperature generated by coal oxidation to concentrate on the downwind side. Additionally, airflow inhibits coal oxidation at low temperatures, while high temperatures promote it. Furthermore, the temperature migration rate of coal decreases with increasing temperature, initially decreases and then increases with rising airflow at low temperatures, whereas the opposite trend is observed at high temperatures.

Numerical Study on Composite Multilayer Insulation Material for Liquid Hydrogen Storage

This study investigated the heat transfer characteristics of composite multilayer insulation (MLI) materials used for the storage and transport of liquid hydrogen at cryogenic temperatures. This research focused on analyzing the effects of thermal boundary temperature, total layer count, and vacuum level on the heat flux through the insulation material. Based on the layer-by-layer model, a heat transfer model of composite MLI was constructed. This research introduces a novel method for analyzing the heat transfer properties of composite MLI in the liquid hydrogen temperature range. Results indicate that heat flux increases with higher thermal boundary temperatures, with the MLI layers near the cold boundary playing a critical role in overall insulation performance. Additionally, numerical analysis was conducted to examine the impact of different material combinations and variations in vacuum level on heat transfer characteristics. Findings reveal that adding spray-on foam insulation reduces heat flux by 20.76% compared to using MLI alone. Furthermore, increasing the total number of MLI layers effectively mitigates heat flux increase, achieving an optimal heat flux of 0.5377 W/m2 with a total of 50 layers.

Effect of forced lateral vibration on flow and heat transfer performance within an annular fuel element

The investigation into the thermo-hydraulic characteristics of fuel elements under forced vibration conditions is of paramount importance in the design and application of offshore nuclear power platforms. This study employs a mathematical model of fluid-solid coupling and applies the theory of multi-field synergy to numerically analyze the flow and heat transfer features in an annular fuel element with internal and external double-sided cooling under forced lateral vibration conditions. The synergistic relationship of each flow field parameter is scrutinized for vibration conditions with frequencies ranging from 0 to 10 Hz and amplitudes from 0.005 to 0.2 m. The results demonstrate that increased amplitude and frequency contribute to enhancing the homogeneity of the temperature and velocity field distributions. Notably, the field synergy angles α, β, ψ, and γ attain minimal values at the gaps (X = 8 mm, X = 25 mm). Furthermore, the variation of vibration frequency and amplitude decreases the mean synergistic angle ψ by 5.14 % and 7.9 % and increases the mean field synergistic angle θ by 23.18 % and 31.21 %, respectively. It indicates that the vibration parameters have the least effect on the synergistic angle ψ and the greatest effect on the synergistic angle θ.

Tunable photo-response in the visible to NIR spectrum range of Germanium-based junctionless nanowire transistor

In this paper, the phototransistor behavior is investigated in the germanium-on-insulator (GeOI)-based junctionless nanowire (JL-NW) transistor under various light conditions. High responsivity and photosensitivity are attributed in the fully depleted regime within the visible and near-infrared bands. The impact of light is also investigated in detail on the electronic and transfer characteristics such as energy bandgap, carrier distribution, electrostatic potential, electric field, generation and recombination rates. Further, the channel doping and thickness are tuned to optimize the optical responsivity. The significant tunability of responsivity is observed with increasing channel thickness. The device exhibits fast optical switching performance, which is further enhanced at higher input light power. Overall, at the nanoscale dimension, our proposed phototransistor demonstrates better detectivity with a significantly smaller illumination area. Thus, the GeOI-based JL-NW phototransistors can be used for imaging (visible wavelength range) and bioimaging (near-infrared wavelength range) applications in advanced technology nodes.

Heat dissipation analysis on the designed inner-outer circulation impingement double-layer microchannel heat sinks with chamfers in power electronic cooling system

This study discusses a new design which utilizes chamfers to further improve the thermal performance of inner-outer circulation impingement double-layer microchannel heat sinks by simulations and experiments manufactured with 3-Dimension printing. In contrast to former designed inner-outer circulation impingement double-layer microchannel heat sinks, inner-outer circulation impingement double-layer microchannel heat sinks with chamfer shows significant advantages in improving overall thermal performance in power electronic cooling. The results of simulation are in good agreement with those of experiment in five 3-Dimensional printing tests. It is demonstrated that the introduction of chamfers is effective in controlling the thermal gradient on substrate of heat sinks, and reducing the peak temperature on substrate of inner-outer circulation impingement double-layer microchannel heat sinks with chamfer as a result. The best performance is presented by a 0.2 mm chamfer located on the corner of the inner-outer circulation shaft in inner-outer circulation impingement double-layer microchannel heat sinks with chamfer. Experimental studies and numerical simulations both indicate that inner-outer circulation impingement double-layer microchannel heat sinks with a 2 mm chamfer significantly enhances heat transfer characteristics. In addition, the average Nusselt number for inner-outer circulation impingement double-layer microchannel heat sinks with a 2 mm chamfer is higher than that of other tests. Moreover, inner-outer circulation impingement double-layer microchannel heat sinks with a 2 mm chamfer performs better than other designs in terms of the overall heat transfer performance, which is significantly better than inner-outer circulation impingement double-layer microchannel heat sinks without chamfers.

Heat Transfer Characteristics of Cryogenically Frozen Kulfi (A Dairy Dessert)

Kulfi was frozen from concentrated milk as well as from reconstituted dry mix with solids content of 60%. The convective heat transfer coefficients during freezing of kulfi by deep freeze and cryogenic methods were determined using one-dimensional transient heat conduction equation. The heat transfer coefficient for cryogenic freezing of kulfi from milk and dry mix concentrates was 210.57 W m-2K-1 and 216.84 W m-2K-1, respectively when compared to 8.33 W m-2K-1 for conventional deep-frozen kulfi. Freezing was achieved in 267 min in deep freeze method, while it reduced to just 185-190 s under cryogenic conditions. The freezing time was predicted using empirical equations, and the prediction accuracies were compared. Cryogenic freezing was nearly 87.66 times faster than deep freezing, and Pham’s model best-predicted the freezing time. Organoleptic evaluation using fuzzy-logic revealed that the order of ranking of quality attributes of kulfi was body and texture (highly important) > melting characteristics (highly important) > flavour and taste (highly important) > colour and appearance (important), and cryogenically frozen kulfi was statistically (p<0.05) superior to conventionally frozen kulfi.