Non-uniform Temperature Research Articles

On the influence of optically controlled thermocapillary flow during vertical convective assembly: Origin of remora disk-like patterns

Vertical convective assembly, a cost-effective and efficient colloidal assembly strategy, has garnered interest from a wide range of disciplines, including photonics and sensors. In this work, we reveal the role of nonuniform temperature distribution at the three-phase contact line (TPCL) during the vertical lifting of the substrate from the colloidal suspension. Conventionally, vertical assembly is performed under isothermal conditions, and the possible outcomes are uniform particle deposits and discrete lines based on stick-slip behavior. We demonstrate that exposing the TPCL with a nearly Gaussian-type temperature profile under an optimal lifting speed of 0.8–5 μm/s results in a new kind of particle pattern, which we call remora disk-like assembly, with periodic central thick regions and lamella-kind structures on either side. We generate the required temperature gradient by irradiating the TPCL with a laser beam, whose emission wavelength matches the plasmonic excitation of the nanoparticles used (λ = 532 nm). The nonuniform temperature distribution at the TPCL (ΔT = 13 °C) generates a corresponding thermocapillary flow, which drives the particles toward the TPCL in a gradient manner. We develop a physical model to explain the particle deposition mechanism, the nature of the remora disk assembly, and the asymmetric depinning behavior of the meniscus. Furthermore, by varying the lifting speed, we could tune the morphology and spacing of the patterns. We believe the new insights on the particle dynamics under optically controlled thermocapillary flow could significantly contribute to the fundamental understanding as well as enriching the applied aspects of the vertical lifting-based colloidal lithography.

A prediction method of thermal deformation of near-zero warping sandwich structure under non-uniform temperature field

The thermal deformation of structure in non-uniform thermal environment in space is a critical factor affecting the imaging accuracy of remote sensing satellite. In this study, the thermal deformation theory of near-zero warping sandwich structure under non-uniform temperature field is established. A high-fidelity prediction method based on CT scanning and reconstruction of structural defects is proposed. Thermal deformation experiments show that this method can accurately characterize the ultra-low thermal deformation behavior of the near-zero warping sandwich metastructure, which is significant for the real-time correction of satellite imaging in orbit.

Numerical simulation study of temperature non-uniformity on the surface of array jet impingement cold plate

Numerical simulation study of temperature non-uniformity on the surface of array jet impingement cold plate

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.

Thermo-mechanical behaviour of energy pile considering non-uniform initial ground temperatures

Ground temperature varies along the vertical direction at shallow depths, whose influences on the thermo-mechanical response of energy piles during heating and cooling processes remain unclear so far. This paper aims to fill this gap by performing finite element numerical analysis based on Comsol Multiphysics software, taking energy piles in the Yellow River flooded area as an example. A three-dimensional numerical model is established and is then validated by comparing with published experimental results. Parametric analyses are conducted with a focus on the heat exchange efficiency, temperature distribution, displacement and axial stress of energy piles caused by heating in summer and cooling in winter. It is found that the ignorance of ground temperature variation could lead to: (i) overestimation of the heat exchange efficiency in both winter and summer; (ii) underestimation of pile head displacement in summer and overestimation in winter; (iii) overestimation of the axial stress in summer and underestimation in winter.

Casting Simulation-Based Design for Manufacturing Backward-Curved Fan with High Shape Difficulty

A large-sized backward-curved fan with high shape difficulty was designed, and fan performance was roughly predicted from computational fluid dynamics. Three gating systems of aluminum sand casting were designed to fabricate the fan. The flow pattern and solidification process of molten metal were analyzed by casting simulation. Three types were applied: bottom-up with four gates, bottom-up with ten gates, and top-down with a feeder. The simulation results of the bottom-up with four gates show that a large temperature loss occurs while molten metal flows into thin blades, and there is a temperature range below the liquidus temperature. Due to nonuniform temperature distribution, the solidification pattern is also not uniform. The bottom-up with ten gates shows almost similar flow and solidification patterns but has the effect of slightly reducing the temperature loss of molten metal. The top-down type has a much smaller temperature loss, while molten metal flows into the mold cavity compared to the bottom-up type and has a directional solidification pattern. As the feeder also acts as a riser to compensate for the shrinkage of the thick part, the simulation results regarding porosities are also significantly reduced. The fan cast as a top-down type has soundness without any unfilled parts.

Thermo-elastic analysis for clamped laminated arches subjected to non-uniform temperature boundary conditions

This paper delves into the thermo-mechanical behavior of clamped composite laminated arches exposed to non-uniform thermal environments. Exact solutions for temperature, displacements, and stresses in laminated arches with arbitrary thickness and number of layers are derived based on the theory of thermoelasticity. Given the complexity of the inhomogeneous temperature conditions at the edges, a specialized temperature function is constructed to accurately satisfy the non-homogeneous thermal boundary conditions. On the basis of Fourier’s law of heat conduction and the principle of superposition, the analytical temperature solution is obtained with the transfer matrix method. Clamped support conditions are addressed by incorporating unit pulse functions and Dirac delta functions into the analysis. The state equation is established with displacements and stresses serving as the state variables. According to the continuity conditions at the interfaces and the mechanical conditions on the surfaces of the laminated arch, the exact solutions for displacements and stresses are uniquely determined. The convergence and comparison studies confirm the efficacy and accuracy of the proposed method. Furthermore, three detailed numerical examples are presented to explore the effects of surface temperature, thickness-to-radius ratios, material properties, and layer numbers on the distributions of temperature, displacements, and stresses within the laminated arches.

Comparative analysis of data-driven models for spatially resolved thermometry using emission spectroscopy.

A methodology is proposed, which addresses the caveat that line-of-sight emission spectroscopy presents in that it cannot provide spatially resolved temperature measurements in non-homogeneous temperature fields. The aim of this research is to explore the use of data-driven models in measuring temperature distributions in a spatially resolved manner using emission spectroscopy data. Two categories of data-driven methods are analyzed: (i) Feature engineering and classical machine learning algorithms, and (ii) end-to-end convolutional neural networks (CNN). In total, combinations of fifteen feature groups and fifteen classical machine learning models, and eleven CNN models are considered and their performances explored. The results indicate that the combination of feature engineering and machine learning provides better performance than the direct use of CNN. Notably, feature engineering, which is comprised of physics-guided transformation, signal representation-based feature extraction and Principal Component Analysis is found to be the most effective. Moreover, it is shown that when using the extracted features, the ensemble-based, light blender learning model offers the best performance with RMSE, RE, RRMSE and R values of 64.3, 0.017, 0.025 and 0.994, respectively. The proposed method, based on feature engineering and the light blender model, is capable of measuring nonuniform temperature distributions from low-resolution spectra, even when the species concentration distribution in the gas mixtures is unknown.

Fishing for Ocean Data in the East Australian Current

Knowledge of the three-dimensional structure and variability of ocean temperature is critical for understanding ocean circulation, heat uptake, marine extremes, and the abundance and distribution of marine life. While satellite technology offers near-global coverage of surface ocean temperatures, subsurface observations represent a big gap in the coastal ocean record. Here we present the first results from FishSOOP (Fisheries Ships of Opportunity), Australia’s pilot program that uses commercial fishing gear to collect subsurface ocean data. Since early 2023, temperature and pressure data have been collected through the FishSOOP project across the Australian continental shelf and upper-slope waters. These new data provide insights into the development of marine heatwaves throughout the water column and new understanding of how the East Australian Current interacts with shelf water to produce nonuniform temperature changes. Comparison with the South East Australian Coastal Ocean Forecasting System (SEA-COFS) model indicates potential for improving forecasts of upper ocean heat content and subsurface temperatures by filling large gaps in observational data coverage. FishSOOP already provides a step change in the amount of open access temperature data available as well as ocean information critical to marine industries for operational decision-making, showing the value of using fishing vessels to observe challenging western boundary current regions.

Analytical Solutions for Thermo-Mechanical Coupling Bending of Cross-Laminated Timber Panels

This study presents analytical solutions grounded in three-dimensional (3D) thermo-elasticity theory to predict the bending behavior of cross-laminated timber (CLT) panels under thermo-mechanical conditions, incorporating the orthotropic and temperature-dependent properties of wood. The model initially utilizes Fourier series expansion based on heat transfer theory to address non-uniform temperature distributions. By restructuring the governing equations into eigenvalue equations, the general solutions for stresses and displacements in the CLT panel are derived, with coefficients determined through the transfer matrix method. A comparative analysis shows that the proposed solution aligns well with finite element results while offering superior computational efficiency. The solution based on the plane section assumption closely matches the proposed solution for thinner panels; however, discrepancies increase as panel thickness rises. Finally, this study explores the thermo-mechanical bending behavior of the CLT panel and proposes a modified superposition principle. The parameter study indicates that the normal stress is mainly affected by modulus and thermal expansion coefficients, while the deflection of the panel is largely dependent on thermal expansion coefficients but less affected by modulus.

Design and evaluation of a solar cooker with reused evacuated tube: enhancing thermal efficiency for food cooking

This study presents the design and performance evaluation of a solar cooker utilizing a reused evacuated tube as its primary cooking element. The cooker’s design prioritizes enhancing thermal efficiency through the incorporation of a parabolic reflective surface and high-conductivity materials, aiming to reduce environmental impact by repurposing discarded components. Experimental tests demonstrated that the prototype outperformed alternative designs, including a parabolic dish and a replica of the commercial Haines® parabolic cooker. This represents an approximate 65% improvement in thermal performance, making the proposed design suitable even under cloudy weather conditions. Moreover, the prototype successfully baked a wheat-flour cookie, indicating its viability for practical food preparation. The findings suggest that such solar cookers could serve as an eco-friendly and cost-effective alternative in areas where fossil fuels are expensive or scarce. Limitations, including non-uniform temperature distribution inside the evacuated tube and the durability of reused materials, are discussed. Recommendations for future research include integrating phase-change materials to enhance heat retention and expanding comparative studies to other types of solar cookers.

Research on the Non-Uniform Temperature Field Distribution of Q355B Steel for Grain Storage under Fire Conditions

To reveal the distribution characteristics of the non-uniform temperature field of structural steel under fire conditions, Q355B steel for grain storage was taken as the research object. A multi-channel temperature detection instrument was used to monitor the temperature distribution of Q355B test plate in real time under gas fire, and the distribution characteristics of the non-uniform temperature field of the steel were studied under different heat inputs. The results showed that the temperature changes within 600 mm from the flame point were significant, while the temperature changes beyond 600 mm were not sensitive. The peak temperature Tmax and the heating rate vr at the fire source points of each test plate increased linearly with the increase of heat input Q at the fire source. With the increase of distance d, the variation trend of the time tmax for each test plate to reach the peak temperature in the rolling direction, was the same. As d increased, tmax gradually increased and tended to stabilize. The average cooling rates vd1 and vd2 of each test plate decreased with the increase of d. The temperature distribution patterns of each test plate were the same. The Tmax-d curve of each test plate followed the Boltzmann function distribution, the Q-∆T followed a linear relationship, and the Q-d0 followed an exponential function relationship. By combining the three, a non-uniform distribution model of Tmax-Q temperature field under gas fire was obtained.

Implementation of an Improved 100 CMM Regenerative Thermal Oxidizer to Reduce VOCs Gas

In this paper, an improved 100 CMM regenerative thermal oxidizer (RTO) is implemented for low-emission combustion. The existing RTO system is a cylindrical drum structure that cyclically introduces and discharges VOC gas into and from the rotating disk, and which achieves excellent energy efficiency with a heat recovery rate of more than 95%. However, the drive shaft designed under the RTO combustion chamber increases wear around the rotating shaft due to the load of the combustion chamber and there is a problem that the untreated gas is simultaneously released through the outlet due to the channeling phenomenon of the combustion chamber and the drive shaft. In addition, the combustion chamber, used at a high temperature of 800 °C, may cause serious problems such as rotation stop or explosion due to pollutants, dust accumulation, and thermal expansion in the chamber. Particularly when treating VOCs harmful gasses, RTO performance may be degraded due to the burner’s non-uniform temperature control and unstable combustion function. To solve this problem, first, the design of the combustion chamber rotating plate driving device is improved. Second, when treating high concentration VOC gas, the design of combustion chamber considers a temperature increase of up to 920 °C or more. For this, the diameter of the gas burner is 125 mm and the outlet dimension is set to 650 mm × 650 mm to effectively discharge high-temperature waste heat. Third, the heat storage material in the combustion chamber is composed of a ceramic block with a thickness of 250 mm, and the outer diameter and height of the combustion chamber are set to, 2530 mm and 1875 mm, respectively, to optimize gas residence time and heat insulation thickness. Fourth, we supplement safe operation by applying the trip control algorithm of the programmable logic controller (PLC) panel for failure prediction of RTO and the Edge-IoT-based intelligent algorithm for this. Finally, we evaluate the economic performance of 100 CMM RTO by conducting empirical experiments to analyze changes in VOCs removal efficiency, nitrogen oxide emission concentration, and total hydrocarbon (THC) concentration through 10 CMM design and implementation.

Study on the total pressure and total temperature distortion of axial flow compressor based on different rain ingestion forms

Aero-engines are required to maintain stable operation under adverse weather conditions, such as heavy rain ingestion. Excessive water ingestion can significantly impact the aerodynamic performance of compressor, potentially leading to performance degradation and even stall. Current investigations reveal that rain ingestion causes losses in both total pressure and total temperature, contributing to the overall deterioration of the performance of compressor. However, these theoretical findings lack robust experimental validation, and the precise relationship between total pressure and temperature losses, alongside the heat and mass transfer mechanisms within the two-phase flow field inside the compressor, remains to be fully established. In this study, a comprehensive experimental and numerical investigation is conducted on a 1.5-stage compressor to assess the effects of water ingestion on compressor performance and internal flow characteristics with varying droplet size distributions and liquid water content (LWC). The results demonstrate that key performance indicators, such as total pressure ratio, efficiency, and the compressor’s stable operating range, are influenced by LWC, droplet size, and the spatial distribution of water ingestion at the inlet. Water ingestion induces non-uniformities in both total pressure and total temperature, with the extent of these distortions governed by factors such as droplet size, concentration, and ingestion patterns across different stages of the compressor. Specifically, increasing water ingestion rates and a concentrated droplet distribution exacerbate total pressure distortions, while simultaneously mitigating total temperature distortions due to the saturation of water vapor. Furthermore, the location and extent of the distorted regions are also influenced by these parameters.

Investigation on the Microscale Interaction Characteristics of POSS-Modified Vegetable Insulating Oil Under Nonuniform Temperature and Electric Fields

Investigation on the Microscale Interaction Characteristics of POSS-Modified Vegetable Insulating Oil Under Nonuniform Temperature and Electric Fields

A review on magnetic permeability in heat and fluid flow characteristics: Applications in magnetized shielding

Magnetic permeability as a material property has a significant impact on the characteristics of a heated surface where induction heating or magneto-thermal systems are involved. In the heat and fluid flow mechanism where heat induction is used, magnetic permeability has a significant and crucial impact. Materials-like ferromagnetic materials with high magnetic permeability enhance the eddy current formation and can concentrate the magnetic field during the processes. These eddy currents lead to Joule heating in terms of electric current induced within the conductor by a changing magnetic field. Magnetic permeability also impacts the temperature profile within the material. Materials with extraordinary permeability due to the concentration of magnetic field can cause localized heating. The variable material properties in the presence of localized heating lead to non-uniform temperature distribution throughout the medium. In the magnetohydrodynamics heat and fluid flow region in the presence of magnetic permeability, some materials perform magnetostrictive impacts; therefore, they change shape or size under the influence of a magnetic field. The role of magnetic permeability along the heated surface is multifaceted in the system where an electromagnetic field is involved and affects how heat is generated, distributed, and dissipated. It is pertinent to mention that in the system where the electromagnetic field is involved, the magnetic permeability directly impacts the efficiency and uniform heating. Therefore, the understanding and controlling of magnetic permeability is important to design the systems that rely on exact thermal management, such as in magnetic shielding, magneto-thermal devices, and induction heating.

Intelligent decision-making approach for rapid optimization of double-wall cooling structures under varying cooling demands

Double-wall structures are widely employed for cooling turbine blades. When manufacturing materials and application conditions vary, the design of double-wall structures should be adapted to meet different cooling demands. However, because of inevitable repetitive iterations, conventional evolutionary algorithms exhibit low efficiency in optimizing double-wall structures when cooling demands change. This paper presents a reinforcement learning-based method to optimize double-wall cooling structures facing various cooling demands rapidly. A decision network established a forward mapping from cooling demands to optimized structural designs and was trained using historical decision-making experiences generated from numerical simulations. The historical experiences were quantified uniformly based on the cooling performance gains or losses resulting from changes in geometric parameters. The physical understanding that cooling performance evaluations differ with varying cooling demands was incorporated into the training dataset. The performance of the trained decision network was validated by varying the cooling optimization objectives. Results indicate that the decision network can achieve optimal double-wall cooling units that meet given objectives with a single decision. The decision process took 5 ms, nearly 90 times faster than traditional genetic algorithms. Moreover, a partitioning, multi-cycle application strategy for the decision network was employed to optimize double-wall cooling plates under non-uniform inlet temperature distributions, resulting in a 13.7K reduction in overall average temperature and improved radial temperature uniformity.

Thermal challenges in heterogeneous packaging: Experimental and machine learning approaches to liquid cooling

In recent years, electronic packaging has evolved significantly to meet demands for higher performance, lower costs, and smaller designs. This shift has led to heterogeneous packaging, which integrates chips of varying stack heights and results in non-uniform heat flux and temperature distributions. These conditions pose substantial thermal management challenges, as they can create large temperature gradients, which increase thermal stress and potentially compromise chip reliability. This study explores single-phase liquid cooling for multi-chip modules (MCMs) through a comprehensive experimental and machine learning approach. It investigates the impact of chip spacing, height, fluid flow rate, fluid inlet location, and heat flux uniformity on chip temperature and the thermohydraulic performance of a commercial cold plate. Results show that increasing coolant flow from 1 LPM to 2 LPM decreased thermal resistance by 26 %, with heat losses remaining below 5 %. The left inlet configuration improved temperature uniformity compared to the right, though both yielded comparable thermal performance. Adjusting heater spacing impacted temperature distribution based on inlet position, and lowering one heater by 1 mm raised its temperatures by 15 °C due to increased thermal resistance from thermal interface material. A transient test demonstrated the cold plate’s quick response to power surges, in which there is only a 1 °C spike above steady state. Complementing these findings, an Artificial Neural Network (ANN) model was developed with optimized architecture specifically for the unique challenges of this study. The ANN model was rigorously validated using an independent dataset, achieving highly accurate temperature predictions (R2 = 0.99) within 2.5 % of experimental values, which demonstrates this framework’s potential for optimizing MCM thermal performance.

Experimental study on boiling heat transfer and pressure drop characteristics of hybrid jet microchannel heat sink

Hybrid jet microchannel cooling can improve the non-uniform temperature distribution, significant pressure drop in microchannel, and the uneven heat transfer coefficient in jet impact. The heat transfer and pressure drop characteristics of a hybrid jet microchannel heat sink were investigated experimentally using deionized water as the working fluid. The experiments were carried out under the operating conditions of mass fluxes from 200 ∼ 600 kg/m2s, subcooling degrees from 20 ∼ 40 K, jet-to-target spacings from 1 ∼ 2.5 mm, and outlet pressure of 1 atm. The results show that increasing jet-to-target spacing and mass flux and decreasing subcooling can improve the heat transfer coefficient, and the maximum heat transfer coefficients increase by 58 %, 73 %, and 50 %, respectively. A heat transfer correlation for the hybrid jet microchannel is proposed with a mean absolute error of 6.5 % based on the experimental data. Since large jet-to-target spacing has more expansion space and is closer to the length of the potential core, increasing jet-to-target spacing results in higher critical heat flux at low mass flux. Compared to the heat sink with higher jet-to-target spacing, the pressure drop of the heat sink with the lower one is significantly affected by the mass flux due to the superposition of size effect of the channel and gas–liquid friction. In addition,the slope that pressure drop curves increase with the decrease of jet-to-target spacing rises with the mass flux, while it is not apparent with the subcooling. As the subcooling and jet-to-target spacing rise and the mass flux decreases, the coefficient of performance will increase.

Surface Kinetics and Uniformity Issues in Low-Temperature Epitaxy of Sige and Si:P Layers

Fabrication of the modern Si/SiGe-based devices normally necessitates the application of reduced temperatures (in the range about 550-750 °C) during the growth, which imposes significant kinetic limitations. As a result, the growth rate, layer composition, and dopant incorporation show high sensitivity to the process parameters and even small temperature non-uniformities over the wafer may result in considerable variation of the SiGe layer thickness and composition.In the growth of Si:P layers, the intrinsic Si growth kinetics is supplemented with the influence of the P concentration on the Si:P growth rate that may differ significantly as compared to the undoped Si despite P incorporation in concentrations of 0.1 % and even lower. In addition, the trend of the growth rate variation (increase or decrease) is different at the atmospheric and reduced operating pressures.Under all these inputs, control of the thickness and composition uniformity over the 300 mm wafer becomes challenging and should involve the adjustment of both temperature distribution and process parameters, including zonal distribution of the gas flow rates.To approach the solution of this problem, we have developed models of SiGe growth from SiH4/SiH2Cl2 (DCS) and GeH4 as well as Si:P growth from DCS and PH3 in the atmosphere of hydrogen with possible addition of HCl. The models account for high coverages of the surface with the adsorbed H2 and HCl, resulting in the growth limitation by low density of the free adsorption sites (kinetically limited growth mode). In case of SiGe, the model accounts also for the dependencies of surface kinetic parameters on the Ge concentration in the layer.The models were carefully verified using numerous experimental data on the layer growth rate and composition versus temperature and precursor flow rates. Calculations with the developed models reproduce the effect and facilitate interpretation of the following experimentally observed trends: higher growth rate and lower Ge concentration at elevated temperatures and the opposite tendency at a higher HCl supply. This behavior is explained in terms of stronger kinetic limitations for the Si part of the alloy that weaken with the temperature increase and contribution of the added HCl to the surface site blocking.The strong and non-monotonic dependence of Si:P growth rate on the PH3 supply is attributed to the competition between the adsorbed HCl and P-containing species. Addition of PH3 to the reactive gas mixture results, on the one hand, in additional coverage of the surface with these species but, on the other hand, in removal of the adsorbed HCl from the surface due to its interaction with these species, followed by the formation of volatile products.Next, the developed approaches have been applied to the detailed modeling of the process in widely used industrial reactors to address the uniformity issue in dependence of the operating parameters and reactor settings. In particular, variation of the uniformity for different temperature distributions over the wafer and gas injection parameters will be discussed. Also, conclusions are made on the relative sensitivity of the thickness and composition to possible non-uniformities of the wafer temperature and details of species transport inside the reactor. Figure 1