Search Results (1,756)

The innovation in thermal storage systems for solar thermal power generation is crucial for achieving efficient utilization of new energy sources. Molten salt has been extensively studied as a phase change material (PCM) for latent heat thermal energy storage systems. In this study, a two-dimensional model of a vertical shell-and-tube heat exchanger is developed, utilizing water-steam as the heat transfer fluid (HTF) and phase change material for heat transfer analysis. Through numerical simulations, we explore the interplay between PCM solidification and HTF boiling. The transient results show that tube length affects water boiling duration and PCM solidification thickness. Higher heat transfer fluid flow rates lower solidified PCM temperatures, while lower heat transfer fluid inlet temperatures delay boiling and shorten durations, forming thicker PCM solidification layers. Adding fins to the tube wall boosts heat transfer efficiency by increasing contact area with the phase change material. This extension of boiling time facilitates greater PCM solidification, although it may not always optimize the alignment of bundles within the thermal energy storage system. Full article

A solar air heater (SAH) converts solar energy into heated air without causing environmental pollution. It features a low initial cost and easy maintenance due to its simple design. However, owing to air’s poor thermal conductivity, its thermal efficiency is relatively low compared to that of other solar systems. To improve its thermal performance, previous studies have aimed at either enlarging the heat transfer surface or increasing the convective heat transfer coefficient. In this study, a novel SAH with fins and sequentially placed obstacles on the fin surface—designed to achieve both surface extension through a finned channel and enhancement of the heat transfer coefficient via the obstacles—was investigated using computational fluid dynamics analysis. The results confirmed that the obstacles enhanced heat transfer performance by up to 2.602 times in the finned channel. However, the obstacles also caused a pressure loss. Therefore, the thermo-hydraulic performance was discussed, and it was concluded that the obstacles with a relative height of 0.12 and a relative pitch of 10 yielded the maximum THP values among the investigated conditions. Additionally, correlations for the Nusselt number and friction factor were derived and predicted the simulation values with good agreement. Full article

Efficient water heating is essential for wool-washing processes, which demand temperatures above 70 °C. To meet this requirement sustainably, a parabolic trough solar concentrator system is proposed in this paper as an alternative to conventional natural gas systems. The design centers on a water pool constructed from bricks reinforced with an internal steel layer, enhancing heat exchange efficiency. Also, various synthetic oils were analyzed as heat transfer fluids (HTFs) within an immersed heat exchanger, such as Thermia B oil, Heat Transfer Oil 32, biphasic oil, and Therminol vp1 oil. Numerical simulations were performed using ANSYS CFX v19.2 software with the k-ε turbulence model to evaluate the thermal performance and temperature distribution. The results demonstrate the superior efficiency of the solar-powered system, with the steel-reinforced pool achieving optimal water temperatures between 78 °C and 85 °C, exceeding the required threshold for industrial wool washing. Among the various synthetic oils analyzed, Thermia B emerged as the most effective heat transfer fluid, maintaining water temperatures in the range of 75 °C to 85 °C. This superior thermal performance is attributed to its high thermal conductivity and reduced heat loss, ensuring consistent and optimal heat distribution for the wool-washing process. Full article

The construction sector presently consumes about 40% of global energy and generates 36% of CO₂ emissions, making facade retrofits a priority for decarbonising buildings. This review clarifies how ventilated facades (VFs), wall assemblies that interpose a ventilated air cavity between outer cladding and the insulated structure, address that challenge. First, the paper categorises VFs by structural configuration, ventilation strategy and functional control into four principal families: double-skin, rainscreen, hybrid/adaptive and active–passive systems, with further extensions such as BIPV, PCM and green-wall integrations that couple energy generation or storage with envelope performance. Heat-transfer analysis shows that the cavity interrupts conductive paths, promotes buoyancy- or wind-driven convection, and curtails radiative exchange. Key design parameters, including cavity depth, vent-area ratio, airflow velocity and surface emissivity, govern this balance, while hybrid ventilation offers the most excellent peak-load mitigation with modest energy input. A synthesis of simulation and field studies indicates that properly detailed VFs reduce envelope cooling loads by 20–55% across diverse climates and cut winter heating demand by 10–20% when vents are seasonally managed or coupled with heat-recovery devices. These thermal benefits translate into steadier interior surface temperatures, lower radiant asymmetry and fewer drafts, thereby expanding the hours occupants remain within comfort bands without mechanical conditioning. Climate-responsive guidance emerges in tropical and arid regions, favouring highly ventilated, low-absorptance cladding; temperate and continental zones gain from adaptive vents, movable insulation or PCM layers; multi-skin adaptive facades promise balanced year-round savings by re-configuring in real time. Overall, the review demonstrates that VFs constitute a versatile, passive-plus platform for low-carbon buildings, simultaneously enhancing energy efficiency, durability and indoor comfort. Future advances in smart controls, bio-based materials and integrated energy-recovery systems are poised to unlock further performance gains and accelerate the sector’s transition to net-zero. Emerging multifunctional materials such as phase-change composites, nanostructured coatings, and perovskite-integrated systems also show promise in enhancing facade adaptability and energy responsiveness. Full article

The spray evaporation process in the boiler desuperheater involves complex droplet behaviors and fluid–thermal coupling, and its temperature distribution characteristics greatly affect the performance and safety of industrial processes. To better understand the process characteristics and develop the optimal desuperheater design, computational fluid dynamics (CFDs) was applied to numerically investigate the flow and thermal characteristics. The Eulerian–Lagrangian approach was used to describe the two-phase flow characteristics. Both primary and secondary droplet breakup, the coupling effect of gas–liquid and stochastic collision and coalescence of droplets were considered in the model. The plain-orifice atomizer model was applied to simulate the atomization process. The numerical model was validated with the plant data. The spray tube structure was found to greatly affect the flow pattern, resulting in the uneven velocity distribution, significant temperature difference, and local reverse flow downstream of the orifices. The velocity and temperature distributions tend to be more uniform due to the complete evaporation and turbulent mixing. Smaller orifices are beneficial for generating smaller-sized droplets, thereby promoting the mass and heat transfer between the steam and droplets. Under the same operating conditions, the desuperheating range of cases with 21, 15, and 9 orifices is 33.7 K, 32.0 K, and 29.8 K, respectively, indicating that the desuperheater with more orifices (i.e., with smaller orifices) shows better desuperheating ability. Additionally, a venturi-type desuperheater was numerically studied and compared with the straight liner case. By contrast, discernible differences in velocity and temperature distribution characteristics can be observed in the venturi case. The desuperheating range of the venturi and straight liner cases is 38.1 K and 35.4 K, respectively. The velocity acceleration through the venturi throat facilitates the droplet breakup and improves mixing, thereby achieving better desuperheating ability and temperature uniformity. Based on the investigation of the spray evaporation process, the complex droplet behaviors and fluid–thermal coupling characteristics in an industrial boiler desuperheater under high temperature and high pressure can be better understood, and effective guidance for the process and design optimizations can be provided. Full article

This study examines methods to improve the energy efficiency of radiofrequency inductively coupled plasma (RF-ICP) torches for radioactive waste treatment, with a focus on surpassing the typical energy efficiency limit of approximately 70%. To improve energy efficiency and plasma performance, this research investigates the transition from axial gas flow to vortex gas flow patterns using COMSOL Multiphysics software v6.2. Key plasma parameters, including energy efficiency, number of gas vortices, heat transfer, and temperature distribution, were analyzed to evaluate the improvements. The results indicate that adopting a vortex flow pattern increases energy conversion efficiency, increases heat flux, and reduces charge losses. Furthermore, optimizing the torch body design, particularly the nozzle, chamber volume, and gas entry angle, significantly improves plasma properties and energy efficiency by up to 90%. Improvements to RF-ICP torches positively impact waste decomposition by creating better thermal conditions that support resource recovery and potential material recycling. In addition, these improvements contribute to reducing secondary waste, mitigating environmental risks, and fostering long-term public support for nuclear technology, thereby promoting a more sustainable approach to waste management. Simulation results demonstrate the potential of RF-ICP flares as a cost-effective and sustainable solution for the thermal treatment of low- to intermediate-level radioactive waste. Full article

Innovative approaches in hot forging, such as the use of floating dies, which aim to minimise burr formation by controlling material flow, require precise management of die geometry distortions. These distortions, primarily caused by thermal gradients, must be tightly controlled to prevent malfunctions during production. This study introduces a comprehensive thermal analysis framework that captures the complete forging cycle—from billet transfer and die closure to forging, spray-cooling, and lubrication. Two advanced heat transfer models were developed: a pressure- and lubrication-dependent contact heat transfer model and a spray-cooling model that simulates fluid dispersion over die surfaces. These models were implemented within the finite element software FORGE-NxT to evaluate the thermal behaviour of dies under realistic operating conditions. These two new models, contact and spray-cooling, implemented within a full-cycle thermal simulation and validated with industrial thermal imaging data, represent a novel contribution. The simulation results showed an average temperature deviation of just 5.8%, demonstrating the predictive reliability of this approach. This validated framework enables accurate estimation of thermal fields in the dies, and offers a practical tool for optimising process parameters, reducing burr formation, and extending die life. Moreover, its structure and methodology can be adapted to various hot forging applications where thermal control is critical to ensuring part quality and process efficiency. Full article

Medium-deep borehole heat exchanger (BHE) systems represent an emerging form of ground source heat pump technology. Their heat transfer process is significantly influenced by geothermal gradient and soil stratification, typically simulated using segmented finite line source (SFLS) models. However, this approach involves computationally intensive procedures that hinder practical engineering implementation. Building upon an SFLS model adapted for complex geological conditions, this study proposes a comprehensive simplified algorithm: (1) For soil stratification: A geothermally-weighted thermal conductivity method converts layered heterogeneous media into an equivalent homogeneous medium; (2) For geothermal gradient: A temperature correction method establishes fluid temperatures under geothermal gradient by superimposing correction terms onto uniform-temperature model results (g-function model). Validated through two engineering case studies, this integrated algorithm provides a straightforward technical tool for heat transfer calculations in BHE systems. Full article

Under the trend of lightweight and high-efficiency development in industrial equipment, precise regulation of lubrication in gear reducers is a key breakthrough for enhancing transmission system efficiency and reliability. This study establishes a three-dimensional numerical model for high-speed gear jet lubrication using computational fluid dynamics (CFD) and dynamic mesh technology. By implementing the volume of fluid (VOF) multiphase flow model and the standard k-ω turbulence model, the study simulates the dynamic distribution of lubricant in gear meshing zones and analyzes critical parameters such as the oil volume fraction, eddy viscosity, and turbulent kinetic energy. The results show that reducing the oil injection distance significantly enhances lubricant coverage and continuity: as the injection distance increases from 4.8 mm to 24 mm, the lubricant shifts from discrete droplets to a dense wedge-shaped film, mitigating lubrication failure risks from secondary atomization and energy loss. The optimized injection distance also improves the spatial stability of eddy viscosity and suppresses excessive dissipation of turbulent kinetic energy, enhancing both the shear-load capacity and thermal management. Dynamic data from monitoring point P show that reducing the injection distance stabilizes lubricant velocity and promotes more consistent oil film formation and heat transfer. Through multiphysics simulations and parametric analysis, this study elucidates the interaction between geometric parameters and hydrodynamic behaviors in jet lubrication systems. The findings provide quantitative evaluation methods for structural optimization and energy control in gear lubrication systems, offering theoretical insights for thermal management and reliability enhancement in high-speed transmission. These results contribute to the lightweight design and sustainable development of industrial equipment. Full article

The rapid advancement of artificial intelligence continuously increases the demand for high computing power, leading to substantial rises in chip power consumption and heat generation. As a result, efficient thermal management has become essential. Inspired by the placoid scales on shark skin, we designed a bionic microchannel heat sink by introducing biomimetic structures on the inner channel surfaces to enhance heat dissipation. Numerical simulations are performed to investigate thermal behavior under different structural configurations. The results show that the arrangement, number, and inclination angle of the placoid structures significantly influence heat transfer by modifying flow patterns, enlarging the heat transfer area, and altering the thermal boundary layer. Notably, at a flow velocity of 2 m/s, the cooling performance differs significantly between inclination angles of 0° and 17°. Moreover, the influence of different quantities of placoid structures shows a consistent trend across various flow rates. These findings demonstrate that bionic surface structures can effectively improve the thermal performance of microchannel heat sinks, offering a promising strategy for high-performance chip cooling. Full article

Understanding the relationship between deformation behavior and mechanisms at elevated temperatures is of great significance for applications of high-temperature titanium alloys. This study systematically investigates the plastic deformation behavior of Ti65 alloy under both room-temperature and high-temperature conditions through in situ tensile testing, combined with slip trace analysis, crystal orientation analysis, and geometrical compatibility factor evaluation. TEM observations and molecular dynamics simulations reveal that plastic deformation is predominantly accommodated by basal and prismatic slip systems with minimal pyramidal slip contribution at room temperature. However, elevated temperatures significantly promote pyramidal <a> and <c+a> slip due to thermal activation. This transition stems from a shift in deformation mechanisms: while room-temperature deformation relies on multi-slip and grain rotation to accommodate strain, high-temperature deformation is governed by efficient slip transfer across grain boundaries enabled by enhanced geometrical compatibility. Consistent with this, thermal activation at elevated temperatures reduces the critical resolved shear stress (CRSS), preferentially activating 1/3<11–23> dislocations and thereby substantially improving plastic deformation capability. These findings provide critical insights into the temperature-dependent deformation mechanisms of Ti65 alloy, offering valuable guidance for performance optimization in high-temperature applications. Full article

This study describes both experimental and numerical investigations into the heat and mass transfer processes governing the vacuum freeze drying of camel milk, with a specific focus on improving the energy efficiency. A three-dimensional model was developed and solved using the finite element method to simulate temperature evolution and sublimation interface progression during drying. The numerical model was validated against experimental data, achieving strong agreement, with an $R^2$ value of 0.94. A detailed parametric analysis examined the effects of the shelf temperature, sample thickness, and chamber pressure on the drying kinetics and energy input. The results indicate that optimising these parameters can significantly reduce the energy consumption and processing time while maintaining product quality. Notably, reducing the sample thickness to 4 mm shortened the drying time by up to 40% and reduced the specific energy consumption (SEC) from 358 to 149 kWh/kg. These findings offer valuable insights for the design of more energy-efficient freeze drying systems, with implications for sustainable milk powder production and industrial-scale process optimisation. Full article

Land surface emissivity (LSE) is the most critical factor affecting land surface temperature (LST) retrieval. Understanding its variation characteristics is essential, as this knowledge provides fundamental prior constraints for the LST retrieval process. This study utilizes thermal infrared emissivity and hyperspectral data collected from diverse underlying surfaces from 2017 to 2024 to analyze LSE variation characteristics across different surface types, spectral bands, and temporal scales. Key influencing factors are quantified to establish empirical relationships between LSE dynamics and environmental variables. Furthermore, the impact of LSE models on diurnal LST retrieval accuracy is systematically evaluated through comparative experiments, emphasizing the necessity of integrating time-dependent LSE corrections into radiative transfer equations. The results indicate that LSE in the 8–11 µm band is highly sensitive to surface composition, with distinct dual-valley absorption features observed between 8 and 9.5 µm across different soil types, highlighting spectral variability. The 9.6 µm LSE exhibits strong sensitivity to crop growth dynamics, characterized by pronounced absorption valleys linked to vegetation biochemical properties. Beyond soil composition, LSE is significantly influenced by soil moisture, temperature, and vegetation coverage, emphasizing the need for multi-factor parameterization. LSE demonstrates typical diurnal variations, with an amplitude reaching an order of magnitude of 0.01, driven by thermal inertia and environmental interactions. A diurnal LSE retrieval model, integrating time-averaged LSE and diurnal perturbations, was developed based on underlying surface characteristics. This model reduced the root mean square error (RMSE) of LST retrieved from geostationary satellites from 6.02 °C to 2.97 °C, significantly enhancing retrieval accuracy. These findings deepen the understanding of LSE characteristics and provide a scientific basis for refining LST/LSE separation algorithms in thermal infrared remote sensing and for optimizing LSE parameterization schemes in land surface process models for climate and hydrological simulations. Full article

Fluids that exhibit self-rewetting properties, such as aqueous long-chain alcohol solutions, display a unique quadratic relationship between surface tension and temperature and are marked by a positive gradient. This characteristic leads to distinctive patterns of thermocapillary convection and associated interfacial dynamics, setting self-rewetting fluids apart from normal fluids (NFs). The potential to improve heat transfer using self-rewetting fluids (SRFs) is garnering interest for use in various technologies, including low-gravity conditions and microfluidic systems. Our research aims to shed light on the contrasting behaviors of SRFs in comparison to NFs regarding interfacial transport phenomena. This study focuses on the thermocapillary convection in SRF layers with a deformable interface enclosed inside a closed container modeled as a square cavity, which is subject to nonuniform heating, represented using a Gaussian profile for the heat flux variation on one of its sides, in the absence of gravity. To achieve this, we have enhanced a central-moment-based lattice Boltzmann method (LBM) utilizing three distribution functions for tracking interfaces, computing two-fluid motions with temperature-dependent surface tension and energy transport, respectively. Through numerical simulations, the impacts of several characteristic parameters, including the viscosity and thermal conductivity ratios, as well as the surface tension–temperature sensitivity parameters, on the distribution and magnitude of the thermocapillary-driven motion are examined. In contrast to that in NFs, the counter-rotating pair of vortices generated in the SRF layers, due to the surface tension gradient at the interface, is found to be directed toward the SRF layers’ hotter zones. Significant interfacial deformations are observed, especially when there are contrasts in the viscosities of the SRF layers. The thermocapillary convection is found to be enhanced if the bottom SRF layer has a higher thermal conductivity or viscosity than that of the top layer or when distributed, rather than localized, heating is applied. Furthermore, the higher the magnitude of the effect of the dimensionless quadratic surface tension sensitivity coefficient on the temperature, or of the effect of the imposed heat flux, the greater the peak interfacial velocity current generated due to the Marangoni stresses. In addition, an examination of the Nusselt number profiles reveals significant redistribution of the heat transfer rates in the SRF layers due to concomitant nonlinear thermocapillary effects. Full article

The southeastern Hainan Island boasts abundant hydrothermal resources, most of which are exposed as thermal springs. Analyzing the hydrochemical characteristics, hydrochemical evolutionary mechanisms, and material transition of these resources is significant for their exploitation and utilization. This study investigated the Nanping geothermal field in southeastern Hainan Island, using five groups of geothermal water samples collected in 2022, as well as seven groups of geothermal water samples, one group of shallow groundwater samples, and one group of surface water samples taken in 2023. Specifically, this study examined water–rock interactions in the geothermal field using the Gibbs model, ion ratios, chloro-alkaline indices (CAIs), and the sodium adsorption ratio (SAR). Moreover, the mineral transfer process in groundwater was analyzed using inverse hydrogeochemical simulation. The results indicate that in the study area the geothermal water temperatures range from 64 °C to 80 °C, pH values from 8.32 to 8.64, and TDS concentrations from 431 mg/L to 623 mg/L. The primary hydrochemical types of geothermal water in the study area include Cl-Na and Cl·HCO₃-Na, suggesting low-temperature, slightly alkaline geothermal water. The hydrochemical components of geothermal water in the study area are primarily affected by water–rock interactions. Besides the dissolution of silicate minerals and halite, cation exchange reactions contribute greatly to the formation of Na⁺ and K⁺ in geothermal water. Geothermal water receives recharge from the atmospheric precipitation of the Diaoluo Shan area in the northwest of the study area, with the recharge elevation ranging from 967 to 1115 m. The inverse hydrogeochemical simulation results reveal that during the water–rock interactions, silicate minerals, clay minerals, gypsum, and halite dissolve, while quartz and carbonate minerals precipitate. Additionally, these processes are accompanied by cation exchange reactions dominated by the replacement of Na⁺ in surrounding rocks by Ca²⁺ in geothermal water. This study can provide a geological basis for the exploitation, utilization, and management of the Nanping geothermal field. Full article