Efficient Heat Research Articles

A thorough analysis of surfactant addition effects on the thermophysical properties and stability of nanofluids

AbstractResearchers are mainly suggesting that optimizing the heat efficiency of thermal apparatus by dispersing nanoparticles into the foundation fluid will boost its heat efficiency in boiling sectors. Many investigators conduct research on factors such as fluid properties, bubble growth and bubble dynamics, heater surface effect, and so forth. However, the problem of deficiency in stability created by nanoparticle sedimentation or agglomeration into the base fluid over time has restricted practicable applications, which has drawn considerable attention in recent years. To overcome that, many researchers used a common technique, the addition of stabilizing agents like surfactants/additives into the nanofluids (NFs) to achieve stability. Understanding the behavior of surfactants in NFs and their effect on various important physical properties of the working fluid is required. In this review, firstly discuss the impact of adding surfactants on the stability of an aqueous solution. Additionally, it provides a concise assessment of how the inclusion of surfactants affects different thermal physical characteristics like interfacial tension, viscosity, and thermal conductivity of aqueous solutions or NFs. Finally, it outlines the primary obstacles and challenges encountered by researchers that continue to be areas of focus for future investigations concerning NFs containing surfactants.

Current Control in Field-Excited Flux Switching Machines: No-Load Induced Voltage Impact Based on the Winding Connection

Micro and mild hybrid electric vehicles can make a significant contribution to reducing emissions and mitigating the environmental impact. Electric machine designs with fewer or no rare-earth permanent magnets will play an important role in the adoption of hybrid solutions. Doubly salient reluctance machines exhibit a simple structure, robust mechanical strength, excellent fault tolerance, and a wide range of speed regulation, which makes them suitable for in-wheel applications. Particular emphasis should be placed on flux-switching machines with wound-field excitation, which offer great operating flexibility, efficient heat dissipation, and power density of up to 4.8 kW/kg. This paper introduces a wound-field flux-switching machine designed for in-wheel applications, featuring individual field current control. The machine has individual access to each of the field coils. The primary objective of this research is to enhance the machine's operational versatility by enabling multiple configurations of the machine, adjusting the way the field-coils are connected. Firstly, a comparison of the armature no-load induced voltage is made for field coils connected in both series and parallel. Additionally, an assessment of the impact of open-circuit failures in one and two adjacent field coils is conducted. Finally, a current control strategy is proposed to effectively manage each individual field coil.

Modeling an Electrolyzer in a Graph-Based Framework

We propose a linear electrolyzer model for steady-state load flow analysis of multi-carrier energy networks, where the electrolyzer is capable of producing hydrogen gas and heat. For our electrolyzer model, we show that there are boundary conditions that lead to a well-posed problem. We derive these conditions for two cases, namely with a known and unknown heat efficiency parameter. Furthermore, the derived conditions are validated numerically. Moreover, we investigate the extensibility of our model by including nonlinear models from electricity, gas, and heat. In this setting, we derived boundary conditions based on our previous findings. Due to the involvement of nonlinearity, it is a challenge to prove that the boundary conditions lead to a well-posed problem. Therefore, we simulated the electrolyzer connected with an electricity, gas, and heat system. Additionally, we considered a known and unknown heat efficiency parameter. The numerical results support that the linear electrolyzer model is solvable in a multi-carrier energy network.

Ethylene Glycol-Based Oxide Tri-Hybrid Nanofluid Flow over a Curved Riga Permeable Medium for the Impact of Thermal Radiation

In various industries, for advanced cooling, electronic device thermal management, and solar thermal systems ethylene glycol (EG)-based nanofluids are presented as efficient heat transfer agents. The proposed oxide tri-hybrid nanofluids comprising multiple oxide nanoparticles, i.e., Al2O3, TiO2 and SiO2 have significantly enhanced thermal properties and stability compared to mono and binary nanofluids. The current investigation aims at the transportation of heat characteristics of an EG-based tri-hybrid nanofluid over a curved Riga surface filled with a porous substance. The study focuses on thermal radiation effects. Moreover, the Riga plate is a magnetic device with alternating electrodes and magnets that provide a significant electromagnetic forcing mechanism for flow behavior. The designed mathematical model with their dimensional form needs transformation to their corresponding dimensionless form with the utility of similarity rules. Further, a numerical technique based on shooting is employed for the solution of the model for the attainment of physical factors. The physical properties of these factors are presented briefly through graphs followed by a comparative analysis.

A Novel Method by Three Slot Coupling Holes Alternate Working to Improve Microwave Heating Uniformity

ABSTRACTMicrowave heating is a booming technology in the food industry that has gained attention for its outstanding benefits. However, the problem of uneven heating remains a persistent challenge in practical applications. To solve this problem, this study presents a novel microwave heating method that improves heating uniformity by generating a rotating electric field. However, unlike traditional methods, it does not rely on physical rotation. To illustrate the method succinctly, a structure with three center‐symmetric coupling slots was designed. The cyclic activation of these slots results in an effect similar to a port in rotation, generating a dynamic electric field in the resonant cavity so that the microwave energy is absorbed more uniformly. To validate the proposed method, a corresponding multiphysics field simulation model is developed. The heating process was simulated and analyzed by deeply coupling Maxwell's equations with heat conduction equations. Moreover, a well‐established system was built for physical experimental validation. The results show that the proposed method surpasses the traditional single‐port fixed‐position heating with a 79.3% improvement in heating efficiency and a 17.2% improvement in heating uniformity.

Influence of multi-stage infrared heating on the efficiency and uniformity of asphalt pavement hot in-place recycling

To enhance heating uniformity and efficiency in the hot in-place recycling process of asphalt pavements, a multi-stage infrared intermittent heating method is developed through the creation of a physical and mathematical model for collaborative heating, analyzed using the finite element simulation software. This method is compared with a traditional single-step heating approach, with a focus on evaluating heating effects under various parameter configurations. Findings indicate that continuous and single-step intermittent infrared heating can cause asphalt pavement ignition and coking, resulting in severe asphalt aging. In contrast, multi-stage intermittent heating reduces maximum pavement surface temperatures as quenching intervals increase, though at the cost of prolonged total construction time and reduced heating efficiency. For two-step intermittent heating, a consistent cyclic heating period lowers the peak pavement temperature and reduces the heating time but significantly lengthens the total construction duration, thus impacting the overall efficiency. When assessing the construction quality, heating rate, efficiency, and energy consumption, the multi-stage intermittent heating method 1 demonstrates superiority over alternative approaches.

Experimental study on the influence of gas injection on Flashing in open natural circulation systems under stable boundary conditions

As an efficient passive heat exchange system, natural circulation systems are widely used in various fields, including passive containment cooling system in nuclear power plants. Flashing is the most common two-phase flow state in natural circulation systems. To enhance the circulation capacity and stability of natural circulation systems, this study conducts experiments on the effects of gas injection on flashing two-phase flow using water and air as mediums. The research analyzes the impact of different gas injection positions and volumes on the flow rate, flow pattern, flow instability, and void fraction of the flashing flow. The results indicate that gas injection enhances the circulation flow rate of the loop and improves system stability. The further the gas injection position is from the upstream of the flashing point, the better the enhancement effect on the circulation flow rate. As the gas injection volume increases, the circulation capacity of the loop strengthens; however, once a certain injection volume is reached, the circulation capacity no longer increases, with a maximum enhancement of up to 80% in circulation flow rate. The introduction of gas injection leads to significant fluctuations in the axial distribution of the void fraction in the rising section, but has a negligible effect on the bubble fraction at the exit of the rising section. The paper analyzes the pressure drops and driving force fractions in the rising section before and after gas injection, and presents the mechanisms by which different gas injection positions and amounts affect the flow in the loop. These findings provide important insights for enhancing and stabilizing natural circulation systems, contributing to improved design and operation of passive safety shell cooling systems.

Biofeedback control of photosynthetic lighting using real-time monitoring of leaf chlorophyll fluorescence.

Optimizing photosynthetic lighting is essential for maximizing crop production and minimizing electricity costs in controlled environment agriculture (CEA). Traditional lighting methods often neglect the impact of environmental factors, crop type, and light acclimation on photosynthetic efficiency. To address this, a chlorophyll fluorescence-based biofeedback system was developed to adjust light-emitting diode (LED) intensity based on real-time plant responses, rather than using a fixed photosynthetic photon flux density (PPFD). This study used the biofeedback system to maintain a range of target quantum yield of photosystem II (ΦPSII) and electron transport rate (ETR) values and to examine if the adjustment logic (ΦPSII or ETR-based) and crop type influence LED light intensity. The system was tested in a growth chamber with lettuce (Lactuca sativa) 'Green Towers' and cucumber (Cucumis sativus) 'Diva' to maintain six ETR levels (30, 50, 70, 90, 110, 130 μmol·m-2·s-1) and five ΦPSII levels (0.65, 0.675, 0.7, 0.725, 0.75) during a 16-hour photoperiod. The ETR-based biofeedback quickly stabilized the target ETR within 30-45 minutes, whereas the ΦPSII-based system needed more time. The system adjusted light intensities according to target values, acclimation status, and crop-specific responses. For example, to maintain a target ETR of 130 μmol·m-2·s-1, the gradual increase in ΦPSII over time due to light acclimation allowed the required PPFD to decrease by 35 μmol·m-2·s-1. Lettuce showed higher photosynthetic efficiency and lower heat dissipation than cucumber, leading to higher PPFD adjustments for lettuce. This biofeedback system effectively controls LED light, optimizing photosynthetic efficiency and potentially reducing lighting costs.

Study on the thermal control performance of lightweight minimal surface lattice structures for aerospace applications

With the rapid evolution of aerospace technology and the increasing complexity of space environments, the demand for lightweight, thermally insulated, and highly efficient heat dissipation materials in aircraft equipment has surged. This study addresses this critical need by investigating Triply Periodic Minimal Surface (TPMS) lattice structures, offering a novel design approach to enhance spacecraft thermal management under extreme temperatures. Our work introduces a methodology to quantitatively assess the thermal insulation and heat dissipation performance of various lightweight lattice sandwich structures. We constructed implicit function models of low volume fractions, including Gyroid, Diamond, Primitive, and IWP, and conducted experiments using an active cooling setup under controlled heating conditions at 300 °C. Key findings reveal that, at flow velocities ranging from 0.25 to 1.5 m/s, the Diamond model exhibited the highest convective heat transfer coefficient, surpassing the Gyroid, Primitive, and IWP models by 6.9 % to 427.3 %, 87.1 % to 485.6 %, and 1.5 % to 98.7 %, respectively. Conversely, at velocities between 1.5 and 3.75 m/s, the Gyroid model demonstrated superior heat exchange performance, improving by 14.6 % to 67.2 %, 73 % to 167.7 %, and 9 % to 64.8 % compared to the Diamond, Primitive, and IWP models. During thermal insulation tests at temperatures from 200 to 400 °C, the Diamond model showed the best insulation effect, while the Primitive model performed poorly. Based on the experimental data, we established empirical relationships between the Nusselt number, friction coefficient, and Geometric Surface Ratio (GS). These findings not only underscore the significant potential of TPMS lattice structures in aerospace applications but also provide a robust theoretical framework and practical guidelines for achieving efficient thermal management in lightweight aerospace manufacturing.

Design and Control Strategies for a 25 kW LLC Converter with a Wide Output Voltage Range Comprising Distributed Core Transformers

Abstract This paper presents the design and experimental validation of a 25 kW LLC converter for a 50 kW electric vehicle (EV) fast charging system (FCS) module, emphasizing a broad output voltage range. The resonant network of the LLC converter is analyzed to ensure optimal operational efficiency, and the half-bridge control method is explored to accommodate extensive voltage range. The converter features a distributed core transformer, focusing on the evaluation of connection methods for enhanced power density and efficient heat dissipation. Based on these analyses, an LLC converter optimized for efficient operation was developed. Experimental verification on a 25 kW testbed confirms the effectiveness and validity of the proposed design and control methods, demonstrating their substantial applicability for high-power EV charging.

Three-dimensional analysis of turbulent twin-swirling jets onto a heated rectangular prism in a channel

Purpose The purpose of this study is to investigate the impact of swirling jet flow on the cooling performance of a heated rectangular prism placed within a channel. The primary aim is to explore the influence of varying aspect ratios (AR) of the prism and different fluid Reynolds numbers (Re) on the cooling efficiency. Design/methodology/approach The numerical analysis is performed using a finite volume-based solver, which incorporates the large eddy simulations (LES) turbulence model. The setup consists of twin 45° swirling jets directed at isothermally heated bodies, with water used as the cooling medium. The rectangular prism is oriented perpendicularly to the channel flow direction, positioned one unit distance from the inlet. This study examines three distinct aspect ratios (AR = 0.5, 1 and 1.5) and a range of Reynolds numbers (6000 = Re = 20000). Findings The results indicate that cooling efficiency improves as the aspect ratio decreases and the Reynolds number increases. Higher Reynolds numbers enhance jet impingement and turbulent mixing, which are crucial for efficient heat transfer. Conversely, lower Reynolds numbers lead to diminished impingement and reduced cooling efficiency. Increasing the Reynolds number from 6000 to 20000 elevates the average Nusselt number by 35% (for AR = 0.5) and up to 45% (for AR = 1.5). It was observed that lower aspect ratios produce superior cooling effects due to intensified localized jet interactions. Originality/value This research significantly contributes to the fields of fluid dynamics and thermal engineering by elucidating the influence of swirling jet flows on the cooling of heated surfaces. The findings offer valuable insights for optimizing the design and performance of cooling systems across various industrial applications.

Precession modulates the poleward expansion of atmospheric circulation to the Arctic Ocean

Under sustained global warming, Arctic climate is projected to become more responsive to changes in North Pacific meridional heat transport as a result of teleconnections between low and high latitudes, but the underlying mechanisms remain poorly understood. Here, we reconstruct subarctic humidity changes over the past 400 kyr to investigate the role of low-to-high latitude interactions in regulating Arctic hydroclimate. Our reconstruction is based on precipitation-driven sediment input variations in the Subarctic North Pacific (SANP), which reveal a strong precessional cycle in subarctic humidity under the relatively low eccentricity variations that dominated the past four glacial-interglacial cycles. Combined with climate model simulations, we highlight that precession drives meridional shifts in the northern rim of the North Pacific Subtropical Gyre (NPSG) and modulates the efficiency of heat and water vapor transfer to the SANP and Arctic regions. Our findings suggest that projections of a northward shift of the NPSG in response to future global warming will lead to wetter conditions in the Arctic Ocean and enhanced sea-ice loss.

Phase-resolved Hubble Space Telescope WFC3 Spectroscopy of the Weakly Irradiated Brown Dwarf GD 1400 and Energy Redistribution–Irradiation Trends in Six White Dwarf–Brown Dwarf Binaries

Abstract Irradiated brown dwarfs offer a unique opportunity to bridge the gap between stellar and planetary atmospheres. We present high-quality Hubble Space Telescope/Wide Field Camera 3/G141 phase-resolved spectra of the white dwarf–brown dwarf binary GD 1400, covering more than one full rotation of the brown dwarf. Accounting for brightness variations caused by ZZ Ceti pulsations, we revealed weak (∼1%) phase-curve amplitude modulations originating from the brown dwarf. Subband light-curve exploration in various bands showed no significant wavelength dependence on amplitude or phase shift. Extracted day- and nightside spectra indicated chemically similar hemispheres, with slightly higher dayside temperatures, suggesting efficient heat redistribution or the dominance of radiative escape over atmospheric circulation. A simple radiative and energy redistribution model reproduced the observed temperatures well. Cloud-inclusive models fit the day and night spectra better than cloudless models, indicating global cloud coverage. We also begin qualitatively exploring atmospheric trends across six irradiated brown dwarfs, from the now complete “Dancing with the Dwarfs” white dwarf–brown dwarf sample. The trend we find in the dayside/nightside temperature and irradiation levels is consistent with efficient heat redistribution for irradiation levels less than ∼109 erg s−1 cm−2 and decreasing efficiency above that level.

Calculation and structural analysis of total factor energy efficiency in high carbon sectors

High carbon sectors (agriculture, industry, construction, and transportation) contribute nearly 85% of carbon emissions, highlighting the urgent need for transitioning towards cleaner energy structures in these sectors. This study utilizes the undesirable SBM model to assess TFEE (total factor energy efficiency) across the total sector and high carbon sectors. It decomposes TFEE from an energy structural perspective into coal, oil, natural gas, and electric heat efficiencies. Using a variance-like decomposition model, it analyzes TFEE at two levels to examine how changes in specific sectors and energy categories affect total sector TFEE. From 2010 to 2021, China’s total sector TFEE increased from 0.542 to 0.676, with electric heat and coal identified as critical factors limiting TFEE improvements. Among the four high carbon sectors, construction exhibited a significant increase in TFEE, agriculture showed a steep rise, the industry demonstrated a U-shaped trend with a turning point in 2015, and transportation experienced a slight decline. TFEE exhibits a descending order among sectors, with agriculture ranking highest, followed by construction, industry, and transportation. Similarly, the total factor efficiencies of energy types show a hierarchical structure, with oil being the most efficient, followed by electric heat, natural gas, and coal. Construction dominates TFEE changes at the sectoral level, contributing 58.87%, while coal contributes over 30% at the energy category level. The decomposition results for each province further indicate that both sectoral structure and energy structure significantly impact the changes in TFEE, and this influence also exhibits regional heterogeneity.

Low-Foaming/Aeration and Low-Traction Electric Drivetrain Fluid (EDF) Solutions for High-Speed E-Mobility

The use of electrically driven drivetrains is increasing for passenger cars and light-, medium-, and heavy-duty trucks. Off-the-shelf automatic transmission fluids (ATFs) are still being used as electric drivetrain fluids (EDFs). EDFs are trending toward lower viscosity for better energy efficiency and better heat transfer capacity, while satisfying all the other challenging requirements, such as gear/bearing scuffing/wear protection, oxidative stability, copper corrosion, and coating/seal material compatibility. In this paper, we will highlight the importance of low foaming, low aeration, and low traction coefficient which are critical for the performance of the EDF during high-speed applications, measured using metrics such as energy efficiency, heat transfer capacity, and longer oil drain interval.

Mathematical Modeling of High-Energy Shaker Mill Process with Lumped Parameter Approach for One-Dimensional Oscillatory Ball Motion with Collisional Heat Generation

This study presents an advanced mathematical model for the high-energy shaker mill process, incorporating thermal interactions among the milling ball, shaker mill vial, and the air contained within. Unlike previous models focusing solely on the ball’s temperature, this research emphasizes the heat produced by impacts and the thermal exchange among all three components. Incorporating these thermal interactions allows the model to provide a more comprehensive depiction of the energy dynamics within the system, leading to more precise predictions of temperature changes. Utilizing a lumped parameter method, the study simplifies complex airflow dynamics and non-uniform temperature distributions in the milling system, enabling efficient numerical analysis. Hamilton’s equations are extended to include supplementary state variables that account for the internal energies of both the vial and the air, in addition to the thermomechanical state variables of the ball. High-energy milling techniques are essential in mechanochemical synthesis and various industrial applications, where the optimization of heat transfer and energy efficiency is crucial. Numerical simulations computed using the Bogacki–Shampine integration algorithm significantly align with experimental data, confirming the model’s accuracy. This comprehensive framework enhances understanding of heat transfer in one-dimensional ball motion, optimizing milling parameters for better performance. The mathematical model facilitates the computation of heat production due to collisions, based on operational parameters like shaking frequency and amplitude, thereby allowing for the anticipation of chemical reaction activation potential in mechanochemistry.

Evaluation of stability, optical properties, and thermal performance of innovative TiO2/FeVO4 Ethylene Glycol hybrid nanofluids

Abstract The effectiveness of direct absorption solar collectors (DASCs) is limited due to the low photothermal conversion efficiency and poor heat transfer qualities of traditional fluids. One potential solution to address this problem is the development of innovative technologies to enhance the solar absorption ability and thermal conductivity of conventional fluids. New generation nanofluids where nanosized particles are dispersed in base fluids like water or ethylene glycol (EG) have attracted interest within diverse solar technologies owing to their superior optical and thermal properties. This study presents a novel TiO2/FeVO4/Ethylene glycol (TFV/EG) nanofluid which exhibits significant solar absorption and thermal stability characteristics. A thorough characterization of the samples was conducted utilizing X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Raman Spectroscopy, High-Resolution Transmission Electron Microscopy (HRTEM), nitrogen adsorption-desorption isotherms and Thermogravimetric Analysis (TGA). The stability, optical and rheological characteristics of TFV nanofluids were also examined. The study’s outcomes indicated that the integration of TFV nanoparticles into ethylene glycol (EG) markedly improved its optical absorption, especially at a concentration of 0.8 g/l TFV, which demonstrated robust absorption in the UV-visible light spectrum. Long-term stability assessments indicated sedimentation for all TFV concentrations following 65 days. A substantial 270% enhancement in thermal conductivity in comparison to EG base fluid was noted at 0.8 g/l TFV reaching 0.83 W·m⁻¹·K⁻¹. All nanofluids exhibited shear-thinning behavior, a hallmark of non-Newtonian fluids. The suggested TFV/EG represents a notable category of nanofluids that exhibited improved thermal performance and stability, rendering them very advantageous for efficient DASCs.

Exploring Efficient and Energy-Saving Microwave Chemical and Material Processes Using Amplitude-Modulated Waves: Pd-Catalyzed Reaction and Ag Nanoparticle Synthesis

This study investigated the impact of a 10 kHz amplitude-modulation (AM) wave from a semiconductor microwave generator on the heating of ultrapure water and electrolyte aqueous solutions containing NaCl. It also examined the effects of AM waves on the yields of 4-methylbiphenyl (4-MBP) in the heterogeneous Suzuki–Miyaura coupling reaction, which was conducted in the presence of palladium nanoparticles supported on activated carbon (Pd/AC), as well as their influence on the growth rate during silver nanoparticle synthesis. Applying AM waves, typically used in telecommunications, enhanced heating efficiencies and improved product yields in both the chemical reaction and nanoparticle growth. Irradiating with microwaves under AM conditions allowed it to reduce power output while still achieving target yields and growth rates, even at the same temperatures without AM. This indicates the potential for highly efficient and energy-saving microwave processes in chemical reactions and material synthesis.

Investigation on the Heating Effects of Intra-Tumoral Injectable Magnetic hydrogels (IT-MG) for Cancer Hyperthermia.

Capacitive-based radiofrequency (Rf) radiation at 27 MHz offers a non-invasive approach for inducing hyperthermia, making it a promising technique for thermal cancer therapy applications. To achieve focused and site-specific hyperthermia, external material is required that efficiently convert Rf radiation into localized heat. Nanomaterials capable of absorbing Rf energy and convert into heat for targeted ablation are of critical importance. In this study, we developed and evaluated an intra-tumoral injectable magnetic hydrogel (IT-MG) composed of Superparamagnetic Iron Oxide Nanoparticles (SPIONs) impregnated in low molecular weight Hyaluronic Acid (HA) forming HA-SPIONs. Our systematic investigation revealed that HA-SPIONs exposed to Rf radiation produced significant temperature increases, reaching up to 50 °C. Further testing in tissue-mimicking phantom models showed consistent heating, with temperatures stabilizing at 43oC, ideal for localized hyperthermia. The ability of HA-SPIONs to act as an efficient localized heating agent when exposed to 27 MHz Rf radiation, reaching apoptosis-inducing temperature has not been previously reported. In conclusion, synergistic effects of IT-MG in both in-vitro and tumour mimicking phantom model demonstrates improved and localized hyperthermia facilitating adjuvant cancer treatment. &#xD.

A field study on thermal comfort and adaptive behaviour of university open-plan offices in severe cold regions of China

ABSTRACT This study investigates the thermal comfort and adaptive behaviours of occupants in open-plan office spaces at a university located in Northeast China, a region characterized by severely cold winters with an average temperature ≤−10°C in the coldest month. The research focuses on the interaction between buildings and occupants from an indoor environmental quality perspective, contributing to the field of occupant-centric building design and operation by studying thermal comfort, adaptive behaviour, and energy-efficient heating strategies in severe cold regions. By employing field measurements and a subjective questionnaire survey, we summarized the environmental factors contributing to thermal discomfort and their respective weights. The results reveal that air temperature, radiant asymmetry caused by envelopes, and relative humidity are the three most significant factors, with weights of 0.376, 0.209, and 0.194, respectively. Furthermore, a fuzzy comprehensive evaluation method was employed to determine the thermal neutral operating temperature (22.5°C) and the acceptable operating temperature range (19.5°C to 25.5°C). Based on the analysis of occupant behaviour characteristics and preferences, a suitable winter heating setting is proposed for open-plan university offices. These findings support the development of more accurate building performance simulations and inform strategies for low-energy building management in severe cold regions.