Fast reconstruction of milling temperature field based on CNN-GRU machine learning models.

With the development of intelligent manufacturing technology, robots have become more widespread in the field of milling processing. When milling difficult-to-machine alloy materials, the localized high temperature and large temperature gradient at the front face of the tool lead to shortened tool life and poor machining quality. The existing temperature field reconstruction methods have many assumptions, large arithmetic volume and long solution time. In this paper, an inverse heat conduction problem solution model based on Gated Convolutional Recurrent Neural Network (CNN-GRU) is proposed for reconstructing the temperature field of the tool during milling. In order to ensure the speed and accuracy of the reconstruction, we propose to utilize the inverse heat conduction problem solution model constructed by knowledge distillation (KD) and compression acceleration, which achieves a significant reduction of the training time with a small loss of optimality and ensures the accuracy and efficiency of the prediction model. With different levels of random noise added to the model input data, CNN-GRU + KD is noise-resistant and still shows good robustness and stability under noisy data. The temperature field reconstruction of the milling tool is carried out for three different working conditions, and the curve fitting excellence under the three conditions is 0.97 at the highest, and the root mean square error is 1.43°C at the minimum, respectively, and the experimental results show that the model is feasible and effective in carrying out the temperature field reconstruction of the milling tool and is of great significance in improving the accuracy of the milling machining robot.

Thermal analysis of a reflection mirror by fluid and solid heat transfer method.

High-repetition-rate free-electron lasers impose stringent requirements on the thermal deformation of beamline optics. The Shanghai HIgh-repetition-rate XFEL aNd Extreme light facility (SHINE) experiences high average thermal power and demands wavefront preservation. To deeply study the thermal field of the first reflection mirror M1 at the FEL-II beamline of SHINE, thermal analysis under a photon energy of 400 eV was executed by fluid and solid heat transfer method. According to the thermal analysis results and the reference cooling water temperature of 30 °C, the temperature of the cooling water at the flow outlet is raised by 0.05 °C, and the wall temperature of the cooling tube increases by a maximum of 0.5 °C. The maximum temperature position of the footprint centerline in the meridian direction deviates away from the central position, and this asymmetrical temperature distribution will directly affect the thermal deformation of the mirror and indirectly affect the focus spot of the beam at the sample.

The Impact of pH on Fouling and Related Physicochemical Properties of Skim Milk Concentrate during Heat Treatment Using a Laboratory-Scale Fouling Rig.

The objective of this study was to investigate the effect of pH (6.1, 6.3, 6.5, and 6.7) on heat-induced changes in concentrated skim milk as related to fouling in heat exchangers. Skim milk (30%, w/w, total solids) was recirculated in a laboratory-scale fouling rig at an initial target temperature of 85 °C for 90 min to simulate thermal processing and preheating of evaporated liquid concentrate feeds in dairy processing. This study investigated key changes in relevant physicochemical properties, such as viscosity, particle size, and sedimentation, as major contributors to fouling at lower pHs (6.1 and 6.3). Additionally, protein aggregation and calcium phosphate precipitation were identified as significant contributors to fouling deposits. Possible strategies to mitigate fouling were determined, including optimizing pH and adjusting heat treatment parameters to minimize protein denaturation and mineral deposition. The findings indicate that carefully controlling pH and processing parameters can greatly enhance the efficiency of milk concentration by evaporation and tailor finished product quality. Moreover, this study showed that monitoring of CIP solutions for protein content and turbidity provides valuable information on the intensity of fouling and the efficiency of cleaning.

Automatic Image Analysis Method as a Tool to Evaluate the Anisotropy of Autoclaved Aerated Concrete for Moisture and Heat Transport.

In this article, the results of studies testing the anisotropy of autoclaved aerated concrete in terms of water and heat transport are presented. Using image analysis techniques, a study was conducted on four different samples of concrete produced in the same process. To ensure the comparability of results, the pictures were taken from a fixed distance with the same lens settings trimmed to a set size. Cross-sectional profiles of the material were examined and were arranged in two directions: perpendicular and parallel to the growth direction occurring in the autoclave. For each block, approximately 4750 objects were obtained, with an average of 2700 objects along the wall and 2050 across it. As a result of the comparative analysis, metrics concerning pores, significantly distinguishing the profile direction, were identified. These included the pore area (area), the maximum and minimum distance between points on the perimeter (Feret, MinFeret), lengths of the major and minor axes of the fitted ellipse (major, minor), and the ratio of the area of selection to its convex hull (solidity). As a reference, standard investigations were conducted for moisture transport using the time domain reflectometry setup and for thermal conductivity values using the steady-state heat flow plate apparatus.

Application of Experimental Studies of Humidity and Temperature in the Time Domain to Determine the Physical Characteristics of a Perlite Concrete Partition.

These days, the use of natural materials is required for sustainable and consequently plus-, zero- and low-energy construction. One of the main objectives of this research was to demonstrate that pelite concrete block masonry can be a structural and thermal insulation material. In order to determine the actual thermal insulation parameters of the building partition, in situ experimental research was carried out in real conditions, taking into account the temperature distribution at different heights of the partition. Empirical measurements were made at five designated heights of the partition with temperature and humidity parameters varying over time. The described experiment was intended to verify the technical parameters of perlite concrete in terms of its thermal insulation properties as a construction material used for vertical partitions. It was shown on the basis of the results obtained that the masonry made of perlite concrete blocks with dimensions of 24 × 24.5 × 37.5 cm laid on the mounting foam can be treated as a building element that meets both the structural and thermal insulation requirements of vertical single-layer partitions. However, it is important for the material to work in a dry environment, since, as shown, a wet perlite block has twice the thermal conductivity coefficient. The results of the measurements were confirmed, for they were known from the physics of buildings, the general principles of the formation of heat and the moisture flow in the analysed masonry of a perlite block. Illustrating this regularity is shown from the course of temperature and moisture in the walls. The proposed new building material is an alternative to walls with a layer of thermal insulation made of materials such as polystyrene or wool and fits into the concept of sustainable construction, acting against climate change, reducing building operating costs, improving living and working conditions as well as fulfilling international obligations regarding environmental goals.

Enhanced near-field radiative heat transfer between core-shell nanoparticles through surface modes hybridization.

Core-shell nanoparticles (CSNPs) are widely used in energy harvesting, conversion, and thermal management due to the excellent physical properties of different components. Because of the synergistic interaction between the core and the shell, the thermal radiative properties are expected to be further enhanced. In this work, we achieve near-field radiative heat transfer (NFRHT) enhancement between SiC@Drude CSNPs. Numerical results show that the total heat flux between NPs is 1.47 times and 9.98 times higher than homogeneous SiC and Drude NPs at the same radius when the core volume fraction is 0.76. Surface modes hybridization arising from the interfaces of the shell-core and shell-air contributes to the improved thermal radiation. The effect of shift frequency on the NFRHT between SiC@Drude CSNPs is studied, showing that the enhancement ratio of NFRHT between CSNPs can reach 4.34 at a shift frequency of 1 × 1014 rad/s, which is 38.34 times higher than the previous work. This study demonstrates that surface modes hybridization in CSNPs can significantly improve NFRHT and open a novel path for high-efficiency energy transport at the nanoscale.

On the Nusselt number correlations of tandem surrogate firebrands on a flat surface.

Through the heat-mass transfer analogy, naphthalene sublimation experiments were conducted in a heated-air wind tunnel to study the effects of aspect ratio and dimensionless separation distance on the convective heat transfer coefficients of three tandem naphthalene cylinders. Nusselt number correlations were presented for the individual naphthalene cylinders and the full configuration of three cylinders. In all the cases studied, the Reynolds number had the strongest effect on the Nusselt number followed by the aspect ratio and the dimensionless separation distance. Nusselt numbers were higher for the smaller aspect ratios. For a given Reynolds number and aspect ratio, the Nusselt number increases with the dimensionless separation distance.

Enhancing radiator cooling capacity: A comparative study of nanofluids and water/EG mixtures.

The present study experimentally investigates and compares the performance of a radiator system cooled by a water-ethylene glycol (70:30) based Al2O3-SiO2-TiO2 nanofluid, with that of a radiator cooled by a water/EG mixture. The equal pumping power criterion of the pump with an equal mass flow rate was used for comparison. Mass flow rate and nanoparticle volume fraction on a radiator cooling system and the radiator's capacity have been studied. Five different nanofluids were prepared with different composition ratios of Al2O3-SiO2-TiO2 with a total of 0.45 % nanoparticles. The flowrate changed in the range of 0.02-0.032 kg/s. The results showed that the increase in heat transfer is mainly due to the flow velocity and the nanoparticles added in different proportions to the base liquid. The UA value and enhancement ratio of NF1 compared to EG/W is 14-18.5 %, for NF2 it is 14.9-21.8 %, for NF3 it is 15.1-23.4 %, for NF4 it is 15.6-27.5 %, and for NF5 it is 15.9-30 % at 0.02 kg/s and 0.032 kg/s. According to the experimental study results, nanofluids with low concentrations of nanoparticles can enhance the heat transfer rate up to 30 % as a comparison with water/EG.

Stepwise Curing Induced All-Stretchable Thermoelectric Generator of High Power Density.

In this study, a wearable and highly stretchable organic thermoelectric (TE) generator with a notable power density is developed. A highly stretchable and solution-processable TE/electrode pattern is realized by stepwise-curing elastomeric and conducting network. Significant advances in the TE or electrical properties are obtained for these stretchable patterns through post-activation treatment, which creates long-range charge transport pathways without degrading pre-established elastomeric networks. The TE and electrode patterns are solution-processed to a stretchable template, so that all-stretchable TE generator is realized. The fabricated TE generator maintains 90% of its maximum TE power output at 40% stretching stress and shows a stable TE power output after 200 stretching cycles. The TE generator maintains its stretchability in highly densified patterns, as the highly stretchable TE/electrode patterns enable good stretchability with little aid of the stretchable template. So, the TE generator has a high power density of 0.32 nW cm-2 K-2, one of the highest values among stretchable TE generators to date.

Finite Difference Modeling and Experimental Investigation of Cyclic Thermal Heating in the Fused Filament Fabrication Process.

Fused filament fabrication (FFF) is one of the most popular additive manufacturing (AM) processes due to its simplicity and low initial and maintenance costs. However, good printing results such as high dimensionality, avoidance of cooling cracks, and warping are directly related to heat control in the process and require precise settings of printing parameters. Therefore, accurate prediction and understanding of temperature peaks and cooling behavior in a local area and in a larger part are important in FFF, as in other AM processes. To analyze the temperature peaks and cooling behavior, we simulated the heat distribution, including convective heat transfer, in a cuboid sample. The model uses the finite difference method (FDM), which is advantageous for parallel computing on graphics processing units and makes temperature simulations also of larger parts feasible. After the verification process, we validate the simulation with an in situ measurement during FFF printing. We conclude the process simulation with a parameter study in which we vary the function of the heat transfer coefficient and part size. For smaller parts, we found that the print bed temperature is crucial for the temperature gradient. The approximations of the heat transfer process play only a secondary role. For larger components, the opposite effect can be observed. The description of heat transfer plays a decisive role for the heat distribution in the component, whereas the bed temperature determines the temperature distribution only in the immediate vicinity of the bed. The developed FFF process model thus provides a good basis for further investigations and can be easily extended by additional effects or transferred to other AM processes.

Recent advances of molecular dynamics simulation on bubble nucleation and boiling heat transfer: A state-of-the-art review.

Boiling heat transfer has become increasingly importance in a variety of industrial fields, but it involves chaotic nature phenomena that remain experimentally challenging. From the perspective of nucleation, bubble embryos emerge at the early stage on extremely small time and length scales. Therefore, molecular dynamics (MD) simulation is a popular and useful tool to uncover the distinctive boiling mechanisms at microscale. Recently, such method has yielded meaningful achievements, but there is still elusive on the current status and bottlenecks behind complex boiling processes. In this work, the state-of-the-art studies on bubble nucleation and boiling heat transfer that covers 129 papers up to 2024 have been comprehensively reviewed. Meanwhile, fundamental concepts of MD are briefly introduced, including MD principles, force fields, and determination of nucleation-related parameters. In contrast to microscopic boiling, bubble nucleation stems from the competition between potential and kinetic energies on micro/nano scale. Then, the key factors such as interfacial wettability and mixture component are thoroughly elucidated for bubble nucleation. In addition, both passive and active techniques are systematically discussed to unveil the underlaying mechanisms for boiling heat transfer enhancement. Finally, the ongoing trials needed for MD simulation are identified, together with an outlook for how to address these challenges. This review aims to offer an up-to-date summary of boiling mechanisms and draw more attention to the development of advanced MD techniques.

High-Efficiency Condensation Heat Transfer Interfaces Based on Superwetting Copper Microgroove/Nanocone Structure.

Utilizing superhydrophobic micro/nanostructures to enhance condensation heat transfer (CHT) of copper surfaces has attracted intensive interest in recent years due to its significance in multiple industrial fields including nuclear power generation, thermal management, water harvesting, and desalination. However, superhydrophobic surfaces have instability risk caused by microcavity defect-induced vapor penetration and/or hydrophobic chemistry destruction. Here, we report a superwetting copper hierarchical microgroove/nanocone (MGNC) structure strategy that can realize high-efficiency CHT over a whole range of surface subcooling. By regulating groove width, fin width, groove depth, and nanostructure growth time, we obtain the optimal MGNC structure, where the CHT coefficient is 121% and 107% higher than that of hydrophilic flat surfaces at surface subcooling of 2 and 15 K, respectively. Such remarkable enhancement can be ascribed to the synergy of three interface effects: more nucleation sites for phase-change energy exchanging, thinner condensate films for reducing thermal resistance, and parallel microchannels for timely drainage. Compared with superhydrophobic strategies, our strategy not only can be mass-producible but also has other inherent advantages: no microcavity-induced performance failure risk as well as being free of chemistry modification, which makes the fabrication process simpler and more economic. Hierarchical micropillar/nanocone structure is also fabricated as the contrast sample for highlighting the superiority of the superwetting MGNC structure in enhancing CHT. This work not only enriches research systems of superwettability surfaces but also helps develop high-performance chips' cooling devices and explore more potential applications.

Analysis of Peri-Implantitis Photothermal Therapy Effect According to Laser Irradiation Location and Angle: A Numerical Approach.

In recent years, dental implants have become increasingly popular around the world. However, if the implant is not properly managed, inflammation may occur, and the implant itself may need to be removed. Peri-implantitis is a common inflammation that occurs in dental implants, and various laser treatments have recently been studied to eliminate it. In this study, the situation of removing peri-implantitis using photothermal therapy, one of the various laser treatments, was analyzed theoretically and numerically. The temperature distribution in the tissue for various laser irradiation locations, angles, and power was calculated based on heat transfer theory, and the degree of thermal damage to tissue was analyzed using the Arrhenius damage integral. In addition, the thermally damaged region ratio of inflamed and normal tissue was analyzed using the Arrhenius thermal damage ratio and normal tissue Arrhenius thermal damage ratio to confirm the trend of treatment results for each treatment condition. The results of the study showed that if only the thermal damage to the inflamed tissue is considered, the laser should be angled vertically, and the laser should be applied to the center of the inflamed tissue rather than close to the implant. However, if the thermal damage to the surrounding normal tissue is also considered, it was found that the laser should be applied at 1.0 mm from the right end of the inflamed tissue for maximum effect. This will allow for more accurate clinical treatment of peri-implantitis in the future.

Numerical Investigation of Enhanced Heat Transfer with Micro Pin Fins in Heat Exchangers.

Pin-fin and flat-tube heat exchangers (PFFTHXs) offer a promising alternative to traditional louvered-fin and flat-tube heat exchangers (LFFTHXs), especially when used as evaporators. The streamlined structure of pin fins helps to effectively remove condensate and defrost water. In this study, we conducted a numerical analysis of 60 different pin-fin configurations across three pin diameters to enhance heat transfer in PFFTHXs. Our investigation focused on how pin pitch affects both airflow and heat transfer efficiency. The results show that a closer pin pitch increases both the heat transfer rate per unit area and the pressure drop for a given airflow velocity. We evaluated the overall performance of these configurations using the heat transfer rate per unit frontal area obtained at equivalent fan power levels. The analysis identified optimal configurations for each pin diameter, with the 0.2 mm diameter configuration demonstrating the highest heat transfer efficiency-this was on par with louvered fins but used fewer resources. This makes it an ideal choice for evaporative applications in PFFTHXs.

Modification of the Surface Crystallinity of Polyphenylene Sulfide and Polyphthalamide Treated by a Pulsed-Arc Atmospheric Pressure Plasma Jet.

Atmospheric plasma jets generated from air or nitrogen using commercial sources with relatively high energy densities are commonly used for industrial applications related to surface treatments, especially to increase the wettability of polymers or to deposit thin films. The heat fluxes to which the substrates are subjected are typically in the order of 100-300 W/cm2, depending on the treatment conditions. The temperature rise in the treated polymer substrates can have critical consequences, such as a change in the surface crystallinity or even the surface degradation of the materials. In this work, we report the phase transitions of two semicrystalline industrial-grade polymer resins reinforced with glass fibers, namely polyphenylene sulfide (PPS) and polyphthalamide (PPA), subjected to plasma treatments, as well as the modeling of the associated heat transfer phenomena using COMSOL Multiphysics. Depending on the treatment time, the surface of PPS becomes more amorphous, while PPA becomes more crystalline. These results show that the thermal history of the materials must be considered when implementing surface engineering by this type of plasma discharge.

Analysis of fractionalized Brinkman flow in the presence of diffusion effect.

A vertical plate experiences a dynamic flow of fractionalized Brinkman fluid governed by fluctuating magnetic forces. This study considers heat absorption and diffusion-thermo effects. The novelty of model is the fractionalized Fourier's and Fick's laws. The problem is solved using the constant proportional Caputo derivative and Laplace transform method. The resulting non-dimensional equations for temperature, mass, and velocity fields are solved and compared visually. We explore the influence of various parameters like the fractional order, heat absorption/generation (Q), chemical reaction rate (R), and magnetic field strength (M) through informative graphs. Additionally, we contrast the velocity fields of fractionalized and regular fluids. The visualizations reveal that diffusion-thermo and mass Grashof number enhance fluid velocity, while chemical reaction and magnetic field tend to suppress it. For the interest of engineering, physical quantities such as Sherwood number, skin friction, and Nusselt number are computed. The present study satisfying all initial and boundary condition can be reduced to to previous published work which shows the validity of present work.

Heat flux concentrator based on nanophononic metamaterials.

Heat flux concentrators have important potential applications in thermoelectric generators. In this study, we demonstrated the heat flux concentration characteristic in nanophononic metamaterials using molecular dynamics simulations. The ratio of heat flux (RHF) is used to evaluate the concentration performance, the RHF can reach 1.62. The performance is optimized by varying the height of the nanopillar and the atomic mass of the atoms in the nanopillar. Increasing the atomic mass of the atoms in the nanopillars yields better performance. We found that the main mechanism for concentration is phonon localization in the nanopillar region. Furthermore, when the distance from the surface increases, the low-frequency peak of phonon density of states (PDOS) decreases, the high-frequency peak increases, and the mode participation rate (MPR) transforms from localized to delocalized. This work provides a new design of heat flux concentrator based on nanophononic metamaterials for regulating thermal conduction.

Sensitive Electrochemical and Thermal Detection of Human Noroviruses Using Molecularly Imprinted Polymer Nanoparticles Generated against a Viral Target.

Norovirus (NoV) is the predominant cause of foodborne illness globally; current detection methods are typically expensive, have inadequate sensitivities, and utilize biological receptors with poor stability. Therefore, accurate, cost-effective, and highly stable detection methods are needed to screen for NoV in foods. We developed molecularly imprinted polymer nanoparticles (nanoMIPs) to detect NoV using a small target epitope (12 amino acids) with a solid-phase synthesis approach. The performance of three batches of nanoMIPs with varying monomer compositions (nanoMIP-1, -2, and -3) were compared both experimentally and computationally. Surface plasmon resonance examined nanoMIP binding affinity to norovirus virus-like particles (NoV-LPs), whereby nanoMIP-1 had the lowest KD value of 0.512 µM. This is significant, as traditional targets for generation of norovirus ligands previously reported were generated against drastically larger norovirus capsid segments that have limitations in ease of production. Further, an electrochemical sensor was developed by covalently attaching the nanoMIPs to glassy carbon electrodes. In agreement with our predictions from density functional theory simulations, electrochemical impedance spectroscopy showed a sensitive response toward NoV-LPs for nanoMIP batches tested; however, nanoMIP-1 was optimal, with an excellent detection limit of 3.4 pg/mL (1.9 × 105 particles/mL). Due to its exceptional performance, nanoMIP-1 was immobilized to screen-printed electrodes and utilized within a thermal sensor, where it exhibited a low detection limit of 6.5 pg/mL (3.7 × 105 particles/mL). Crucially, we demonstrated that nanoMIP-1 could detect NoV in real food samples (romaine lettuce) by using electrochemical and thermal sensors. Consequently, the study highlights the exceptional potential of nanoMIPs to replace traditional biological materials (e.g., antibodies) as sensitive, versatile, and highly stable receptors within NoV sensors.

Ultrahigh Subcooling Dropwise Condensation Heat Transfer on Slippery Liquid-like Monolayer Grafted Surfaces.

Rapid and continuous droplet shedding is crucial for many applications, including thermal management, water harvesting, and microfluidics, among others. Superhydrophobic surfaces, though effective, suffer from droplet pinning at high subcooling temperature (Tsub). Conversely, slippery liquid-like surfaces covalently bonded with flexible hydrophobic molecules show high stability and low droplet adhesion attributed to their dense and ultrasmooth water repellent polymer chains, enhancing dropwise condensation and rapid shedding. In this work, linear poly(dimethylsiloxane) chains of various viscosities are covalently bonded onto silicon substrates to form thin and smooth monolayer coated surfaces. The formation of the monolayer is characterized by cryogenic transmission electron microscopy. On these surfaces a very low contact angle hysteresis is reported within wide surface temperature ranges as well as continuous dropwise condensation at ultrahigh Tsub of 60 K. In particular, one of the highest condensation heat fluxes of 1392.60 kW·m-2 and a heat transfer coefficient of 23.21 kW·m-2·K-1 at ultrahigh Tsub of 60 K is reported. The experimental heat transfer performance is further compared to the theoretical heat transfer via the individual droplets with the droplet distribution elucidated via both macroscopic observations as well as environmental scanning electron microscopy. Finally, only a mild decrease in the heat transfer coefficient of 20.3% after 100 h of condensation test at Tsub of 60 K is reported. Slippery liquid-like surfaces promote droplet shedding and sustain dropwise condensation at high Tsub without flooding empowered by the lower frictional forces, addressing challenges in heat transfer performance and durability.

The effect of buoyancy force on natural convection heat transfer of nanofluid flow in triangular cavity with different barriers.

This article aims to investigate the thermophysical properties of viscous nanofluid in the two-dimensional geometry of a triangular cavity containing inverted triangle, square, and rhombus obstacles with different boundary conditions. The boundary conditions of the triangular cavity are investigated in two mechanisms: 1) uniform temperature at the base of the cavity and 2) non-uniform temperature (sinusoidal function) at the base of the cavity. The finite element method was used to solve the governing equations of the viscous nanofluid flow. The effect of flow control parameters on velocity and temperature profile is considered in a wide range of Rayleigh and Prandtl numbers. The innovation of this study is to use different obstacles in the two-dimensional geometry of the triangular cavity and compare their velocity profiles and temperature distribution in different boundary conditions. The results show that in the obstacles used in the triangular cavity, with the increase of buoyancy force and Rayleigh number, the values of velocities increased and caused the formation of vortex flow, and the pattern of velocity vectors in the cavity with the rule of uniform temperature has given a distinctive feature. Also, the application of trigonometric temperature functions in general and sinusoidal temperature functions in particular with high frequency can effectively create a vortex flow and increase the heat transfer rate.