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A Particle Strength Exchange Method for Metal Removal in Laser Drilling
摘要： A meshfree Particle Strength Exchange (PSE) method is developed for metal removal in a simplified laser drilling problem. To this end, the problem of transient state heat transfer is solved by exerting a static laser beam with a Gaussian intensity distribution, as the external heat source. The proposed PSE scheme is a fully Lagrangian approach, which is straightforward to implement as compared to alternative meshfree methods currently adopted in the state of the art. The performance of the PSE method in solving the heat transfer problem at hand is assessed through a case-study on single-pulse laser heating of a metal workpiece. The simulation results are finally verified against both numerical and experimental data available in the literature, demonstrating the suitability of the proposed approach in addressing the thermal issues of complex manufacturing processes.
关键词： Heat transfer,PSE,Meshfree methods,Laser drilling
更新于2025-09-12 10:27:22
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An algorithm for designing a cooling system for photovoltaic panels
摘要： Solar energy is an abundant source of energy for generating electricity. One of the main challenges in using solar energy is that solar photovoltaic (PV) panels are typically used in regions where solar radiation is high; consequently, the temperature of the panels will increase, and the efficiency of the panels will decrease. Adding cooling tubes to the PV panel is a possible approach to cool it down. To design such cooling systems, CFD simulations may be used; however, this approach tends to be time-consuming. In this paper, we report a new algorithm for designing straight cooling tubes. The algorithm can be used to determine important design parameters such as tube center-to-center length, diameter of the tube, and the minimum tube length needed to achieve a desired outlet temperature. The accuracy of the algorithm was tested using real-world data (including various ambient temperatures and solar radiations) and the maximum temperature difference between desired outlet temperature and CFD simulation for the designed cooling system was found to be 1.7oK.
关键词： Solar energy,Conjugated heat transfer,Design algorithm,Renewable energy,PVT,Cooling system
更新于2025-09-12 10:27:22
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Performance Improvement of Trough Concentrating Photovoltaic Thermal System: A Review
摘要： This paper presents an overview on the performance improvement of trough concentrating photovoltaic thermal system by optimizing different components and operating parameters of the system and has been put forwarded. Initially, the performance of four types of solar cell arrays was studied, in that triple junction GaAs cells possessed good performance characteristics. Subsequently the importance of increasing the concentrator reflectivity for improving the performance of TCPV/T system is presented by increasing the mirror reflectivity from 0.69 to 0.92 and consequently the maximum power of the cell array got increased. Then, the role of receiver shape like rectangle and triangle for the maximum utilization of solar radiation is also presented.
关键词： Concentrator reflectivity,GaAs,PV cells,trough collector,Heat transfer
更新于2025-09-12 10:27:22
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Enhanced Physical and Thermal Performance of Expanded Graphite-Based Heat Sink for LED Radiator
摘要： An experimental study was carried out to investigate the heat transfer characteristics of Cu and Al–modified expanded graphite heat sinks. In this study, the heat sinks were composed of expanded graphite as an active material, Cu and Al as heat transfer enhancement material and resin as a binder. Graphite with high purity was obtained via treated with different amount of Na2CO3. The as-prepared heat sinks were characterized by XRD, pH, SEM, electrical resistivity, bending strength and thermal analysis. The metal Al modified expanded graphite composite heat sink in our experiment exhibited a good rate of capability in physical and thermal performances. Sample GA5-300 showed highest thermal diffusivity and thermal conductivity.
关键词： Expanded graphite,Heat transfer,Thermal diffusivity and conductivity
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Periodic Amplification of Radiative Heat Transfer
摘要： The thermal excitation of materials with a periodic heat flux or temperature modulated in time is a reliable and accurate tool usually applied to determine thermal properties, through techniques such as thermoreflectance, photothermal radiometry, 3ω, photoacoustics, thermal-wave resonant cavity, etc. Moreover, over the past years, the control of heat flux has been improved by means of phase-change materials (PCMs), whose internal structures are strongly driven by their temperature, which results in significant variations of their thermal, optical, and electrical properties. Thermochromic materials (VO2, nitinol) or superconductors are examples of such PCMs, where the material can be either in an insulator phase, with low thermal/electrical conductivity and high emissivity, or in a metallic one characterized by a high thermal/electrical conductivity and low emissivity. This metal-insulator transition (MIT) occurs at the critical temperature of each PCM and can therefore be used to tune the heat currents that the PCM exchanges with the environment, which paves the wave for novel applications.
关键词： radiative heat transfer,metal-insulator transition,thermochromic materials,thermal excitation,phase-change materials
更新于2025-09-11 14:15:04
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Radiative Heat Transfer in Two-Dimensional Cylindrical Medium Coupled with BRDF Surface
摘要： For radiative heat transfer analysis and temperature measurements, the surface is usually assumed to be blackbody, diffuse, or specular, which may cause obvious errors under actual working conditions. The bidirectional reflectance distribution function (BRDF), which is considered as a relatively strict approach for characterizing a real surface, has been adopted in heat transfer analysis. In this study, two BRDF models—the Minnaert model and the Torrance and Sparrow model—are applied to investigate the effects of different boundary conditions on the radiative heat transfer. Additionally, the distribution of ratios of energy scattered by the medium or reflected by the boundary surface method is extended to solve the radiative transfer in a two-dimensional graded-index medium coupled with BRDF surfaces in a cylindrical coordinate system. The results show that greater deviation of the BRDF surface from the diffuse characteristics yields a larger difference of the radiative heat flux and intensity distributions between the BRDF and the diffuse surface. The radiative heat flux deviation reaches 12.78%, and more significant differences exist in the radiative intensity along some directions under different boundary conditions. The specular reflection plays a leading role at high reflection angles. However, the increased scattering ability can weaken the influence of the reflection of the BRDF on the radiative intensity distributions.
关键词： radiative heat transfer,graded-index medium,Torrance and Sparrow model,Minnaert model,BRDF surface,cylindrical medium
更新于2025-09-11 14:15:04
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[IEEE 2019 10th International Workshop on the Analysis of Multitemporal Remote Sensing Images (MultiTemp) - Shanghai, China (2019.8.5-2019.8.7)] 2019 10th International Workshop on the Analysis of Multitemporal Remote Sensing Images (MultiTemp) - Comparison between Field-Measured and Multitemporal Modeled Temperature for Firn Compaction Modelling in Taishan Station, Antarctica
摘要： In Antarctic ice sheet, firn compaction corrections should be applied to the elevation changes estimated from multi-year satellite altimetry to reduce components without mass change contribution. Firn compaction rate is mainly affected by firn temperature and density in the vertical column during the yearly and decadal scale compaction processes and it’s essential to account for these two parameters in the firn compaction modelling. In this paper, we solved the temperature along depth and time given initial and boundary conditions based on published physical principles and both our experimental software and an open-source package. We have performed a comparison analysis between the modeled and field temporal temperature profiles at the Taishan Station, East Antarctica. The mean temperature differences of the results with the 12-hour and 1-month time steps are -0.36 K and -0.45 K, and the standard deviations are 1.7 K and 3.2 K, respectively. The temperature modelling process is a part of the firn compaction correction estimation modeling.
关键词： firn compaction modelling,multitemporal modeled temperature,heat transfer,Taishan Station
更新于2025-09-11 14:15:04
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Conceptual design of a high-efficiency heat transfer circular-conical-frustum laser amplifier with amplified divergent beams
摘要： Two problems exist in the repetition rate laser system with the cylindrical laser amplifier–its inability to offer the gain required for the injected seed in the low-energy stage of the laser system, and its failure to achieve efficient heat dissipation under high gain and high repetition rate. This paper proposes a new conceptual design of a laser amplifier with a circular-conical-frustum gain medium and corresponding configuration scheme for energy storage. Under the influence of its higher field synergy, the capacity of heat dissipation possessed by the system with a frustum gain medium can be increased by 10–25% and the average temperature at the steady state can be reduced by 2–4°C. With the amplified spherical wave, the energy extraction efficiency can be improved by 5% in the low-gain state and 15% in the high-gain state, and it can be further increased by 20% under the new configuration scheme of energy storage. Thus, it can be concluded that this new configuration of laser amplifier is more suitable than cylindrical amplifier and plays an important role in miniaturizing the laser system at high repetition rate.
关键词： Divergent Beams,Field synergy,Extraction efficiency,Circular-conical-frustum,Heat transfer
更新于2025-09-11 14:15:04
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Potential of water natural circulation coupled with nano-enhanced PCM for PV module cooling
摘要： This paper introduces a new photovoltaic module passive cooling system that works with natural cooling water circulation. The heat was removed from cooling water by a PCM-based cooling system. A special zig zag geometry of PCM container was considered to increase the heat transfer surface. At the ?rst stage of experiments, a composed oil consisting of 82 wt% coconut oil and 18 wt% sun?ower oil was used as PCM. Then, in order to increase the performance of heat transfer between PCM and cooling water, the composed oil was mixed with Boehmite nanopowder (0.009 (w/w)). The cooling performance of the composed oil and nano - composed oil was assessed by monitoring the temperature and the generated electrical power of the panel at various radiation intensities. The results reveal the reliability of the proposed system for cooling of the PV module without need to any pumping system. Moreover, the results show that using nano - composed PCM is more ef?cient than the plain one. The highest increase in the maximum produced power relative to the reference case were obtained in the presence of nano - composed oil, which were 44.74, 46.63, 48.23% at the radiation intensities of 410,530,690 W/m2, respectively.
关键词： Photovoltaic,PCM,Natural circulation,Passive cooling,Boehmite nanoparticles,Heat transfer
更新于2025-09-11 14:15:04
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Efficient thermal finite element modeling of selective laser melting of Inconel 718
摘要： In the powder bed fusion process, an accurate prediction of the transient temperature field of a part is essential to calculate the subsequent thermal stress evolution and microstructure propagation in that part. The experimental method is time-consuming and expensive since the temperature field is controlled by many process parameters. Numerical heat transfer models can be used to estimate the temperature field at any time point. However, traditional numerical simulation schemes are not suitable for the layer-wised fabrication process due to the extremely high computational cost. The computational cost mainly relies on the element number and time step size. This research provides a new efficient and part-level simulation scheme based on an open-source finite element library, which is able to adaptively refine and coarsen the mesh and solve finite element equations with multiple processors in a parallel way. Here, a new mesh strategy that aims to reduce the element number while keeping the solution accuracy is developed. The simulation speed is 12× to 18× faster compared with the traditional simulation scheme depending on the scale of the simulated domain and number of processors. Simulation results have been compared with the experimental results of an Inconel 718 component. It is shown that the testing point in the simulation experiences the same thermal cycles of the same point in the experiment. This simulation scheme can also be used to optimize the process parameters such as scanning pattern, scan velocity, and layer thickness and can be easily extended to other additive manufacturing processes.
关键词： Selective laser melting,Finite element method,MPI,Heat transfer,Adaptive mesh
更新于2025-09-11 14:15:04