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Thermal and Physical Performance of Heat Sink for Light-Emitting Diode Improved with Expanded Graphite
摘要： In this study, the fabrication of working expanded graphite based heat sink was carried out as follows. Briefly, the round heat sink were composed of graphite as an active material, Cu and Al as heat transfer enhancement material and resin as a binder. The prepared round heat sinks were characterized by X-ray diffraction and scanning electron microscopy. After chemical intercalation treatment and heat treatment at 673-1073 K, it was clearly seen that the spacing of the interlayers of graphite flakes increased. The metal modified graphite heat sinks in our experiment exhibited a good rate of capability in physical performances. Sample GA10-400 showed a best and most high density, highest thermal diffusivity and thermal conductivity
关键词： Physical performance,Density,Thermal diffusivity and conductivity,Graphite,Heat transfer
更新于2025-09-16 10:30:52
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Process-Structure-Properties-Performance Modeling for Selective Laser Melting
摘要： Selective laser melting (SLM) is a promising manufacturing technique where the part design, from performance and properties process control and alloying, can be accelerated with integrated computational materials engineering (ICME). This paper demonstrates a process-structure-properties-performance modeling framework for SLM. For powder-bed scale melt pool modeling, we present a diffuse-interface multiphase computational fluid dynamics model which couples Navier–Stokes, Cahn–Hilliard, and heat-transfer equations. A computationally efficient large-scale heat-transfer model is used to describe the temperature evolution in larger volumes. Phase field modeling is used to demonstrate how epitaxial growth of Ti-6-4 can be interrupted with inoculants to obtain an equiaxed polycrystalline structure. These structures are enriched with a synthetic lath martensite substructure, and their micromechanical response are investigated with a crystal plasticity model. The fatigue performance of these structures are analyzed, with spherical porelike defects and high-aspect-ratio cracklike defects incorporated, and a cycle-amplitude fatigue graph is produced to quantify the fatigue behavior of the structures. The simulated fatigue life presents trends consistent with the literature in terms of high cycle and low cycle fatigue, and the role of defects in dominating the respective performance of the produced SLM structures. The proposed ICME workflow emphasizes the possibilities arising from the vast design space exploitable with respect to manufacturing systems, powders, respective alloy chemistries, and microstructures. By digitalizing the whole workflow and enabling a thorough and detailed virtual evaluation of the causal relationships, the promise of product-targeted materials and solutions for metal additive manufacturing becomes closer to practical engineering application.
关键词： heat-transfer modeling,additive manufacturing,phase field modeling,integrated computational materials engineering,crystal plasticity,selective laser melting,micromechanical modeling
更新于2025-09-16 10:30:52
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[IEEE 2019 Innovations in Power and Advanced Computing Technologies (i-PACT) - Vellore, India (2019.3.22-2019.3.23)] 2019 Innovations in Power and Advanced Computing Technologies (i-PACT) - Numerical modeling and Simulation of Thermophotovoltaic Cell using COMSOL
摘要： In recent years, Thermophotovoltaics (TPV) have become a hot and essential research area due to the increase in requirement of electrical energy at global level as well as the scarcity on other fossil fuels. TPV is a technology which uses the application of photovoltaic diodes for generating electricity from thermal radiation. This process is generally achieved by using thermal emitters that are heated to a temperature greater than 800o C. In this work, we have designed a circular TPV cell using Silicon Carbide as an emitter and Gallium Antimonide as solar PV cells. The emitter is operated at a heat varying from 1000 K to 2000 K using parametric solver at a regular interval of 100 K. We have analyzed how the heat transfers with surface to surface radiation at a stationary condition. The temperature distribution and electrical power output of TPV cell is also observed. It is observed that the proposed TPV cell produces a maximum of 27000 W/m2 electrical power output at an emitter temperature of 1700 K and solar temperature of 1300 K.
关键词： Solar cell,Electrical energy,Thermophotovoltaic cell,Photovoltaic cell,Heat transfer,Renewable energy
更新于2025-09-16 10:30:52
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Direct Determination of Total Hemispherical Emittance of Perovskite and Silicon Solar Cells
摘要： Because the performance and lifetime of a solar cell is sensitive to its operating temperature, an accurate knowledge of the total hemispherical emittance as a function of temperature is required. Granados et al. report a rapid transient calorimetry for the direct determination of total hemispherical emittance of perovskite and silicon solar cells over their operating temperature.
关键词： total hemispherical emittance,perovskite solar cells,silicon solar cells,transient calorimetry,radiative heat transfer
更新于2025-09-16 10:30:52
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Modeling of laser heating of bi-layered microdomain using the general boundary element method
摘要： Heat transfer processes occurring in 3D bi-layered microdomain subjected to the ultra-short laser pulse are considered. The problem is described by the system of two dual-phase lag equations supplemented by appropriate boundary and initial conditions. The ideal contact condition at the interface between the layers in the case of the dual-phase lag model is formulated in a di?erent way than in the macroscopic Fourier one. To solve the problem the general boundary element method is proposed. In the ?nal part of the paper the examples of computations are presented, and the conclusions are formulated.
关键词： Microscale heat transfer,Dual-phase lag model,Laser heating,General boundary element method
更新于2025-09-16 10:30:52
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[IEEE 2019 Days on Diffraction (DD) - St. Petersburg, Russia (2019.6.3-2019.6.7)] 2019 Days on Diffraction (DD) - Spectrum of Schr??dinger operators with potential waveguides on periodic graphs
摘要： We investigate thermal effects of pulmonary cooling which was induced by cold air through an endotracheal tube via a ventilator on newborn piglets. A mathematical model was initially employed to compare the thermal impact of two different gas mixtures, O2-medical air (1:2) and O2-Xe (1:2), across the respiratory tract and within the brain. Following mathematical simulations, we examined the theoretical predictions with O2-medical air condition on nine anesthetized piglets which were randomized to two treatment groups: 1) control group (n = 4) and 2) pulmonary cooling group (n = 5). Numerical and experimental results using O2-medical air mixture show that brain temperature fell from 38.5 ?C and 38.3 ?C ± 0.3 ?C to 35.7 ?C ± 0.9 ?C and 36.5 ?C ± 0.6 ?C during 3 h cooling which corresponded to a mean cooling rate of 0.9 ?C/h ± 0.2 ?C/h and 0.6 ?C/h ± 0.1 ?C/h, respectively. According to the numerical results, decreasing the metabolic rate and increasing air velocity are helpful to maximize the cooling effect. We demonstrated that pulmonary cooling by cooling of inhalation gases immediately before they enter the trachea can slowly reduce brain and core body temperature of newborn piglets. Numerical simulations show no significant differences between two different inhaled conditions, i.e., O2-medical air (1:2) and O2-Xe (1:2) with respect to cooling rate.
关键词： brain,bio-heat transfer,Pulmonary cooling,piglet,numerical simulation
更新于2025-09-16 10:30:52
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Solar Engineering of Thermal Processes, Photovoltaics and Wind || Selected Heat Transfer Topics
摘要： This chapter is intended to review those aspects of heat transfer that are important in the design and analysis of solar collectors and systems. It begins with a review of radiation heat transfer, which is often given cursory treatment in standard heat transfer courses. The next sections review some convection correlations for internal flow and wind-induced flow. The role of convection and conduction heat transfer in the performance of solar systems is obvious. Radiation heat transfer plays a role in bringing energy to the earth, but not so obvious is the significant role radiation heat transfer plays in the operation of solar collectors. In usual engineering practice, radiation heat transfer is often negligible. In a solar collector, the energy flux is often two orders of magnitude smaller than in conventional heat transfer equipment, and thermal radiation is a significant mode of heat transfer.
关键词： convection,conduction,radiation,solar collectors,heat transfer
更新于2025-09-16 10:30:52
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Solar Engineering of Thermal Processes, Photovoltaics and Wind || Building Heating
摘要： Heat for comfort in buildings can be provided from solar energy by systems that are similar in many respects to the water heater systems described in Chapter 12. The two most common heat transfer fluids are water (or water and antifreeze mixtures) and air, and systems based on each of these are described in this chapter. The basic components are the collector, storage unit, and load (i.e., the house or building to be heated). In temperate climates, an auxiliary energy source must be provided and the design problem is in part the determination of an optimum combination of solar energy and auxiliary (i.e., conventional) energy. Systems for space heating are very similar to those for water heating, and the same considerations of combination with an auxiliary source, boiling and freezing, controls, and so on, apply to both applications.
关键词： solar energy,storage unit,auxiliary energy,collector,heat transfer fluids,heating systems
更新于2025-09-16 10:30:52
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Thermal regulation of PV fa?ade integrated with thin-film solar cells through a naturally ventilated open air channel
摘要： Thermal regulation of photovoltaic fa?ade through passive air channel provides a cost effective measure for improving solar to electrical energy conversion efficiency. This study presents a 2D numerical investigation of the fluid flow and heat transfer characteristics of natural convection driven by buoyancy force inside the passive cooling air channel created by two vertical parallel walls. One wall is heated by absorbed heat by photovoltaic (PV) cells from solar radiation. Numerical solutions for open and closed channel are obtained for the channel of 1.05 m in height and 0.16 m in width, respectively. The natural convective cooling effect on the PV cells for different ventilation strategies were examined considering the surface temperature of PV panels. It is found that the maximum surface temperature reaches 57.1 oC for closed channel, 49.1 oC for opened channel. Opened channel behind the PV panel is an economic way of heat releasing for the benefit of PV power generation. However, other issues such as noise control and cleaning difficulty may also be encountered by fa?ade designers. At the same time, understanding the mechanisms involved in the fluid flow and heat transfer in the channel back the PV panel through examining the pressure distribution along the cavity is required and equally important for the design improvements of PV fa?ade especially for the design of the air channel entrance to lower its pressure drop.
关键词： Ventilated and closed PV facade,Building integrated photovoltaic (BIPV),Convective heat transfer
更新于2025-09-12 10:27:22
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A double raster laser scanning strategy for rapid die-less bending of 3D shape
摘要： Double raster scanning approach to 3D laser forming was investigated to obtain a large deformation with one-step laser irradiation, avoiding repetitive scanning. The magnitude of the deformation during raster scanning was found to be strongly dependent on the overlapping between adjacent passes, which can be controlled by changing their spacing and the beam diameter. Therefore, 3D deformation during raster scanning has been analyzed at various overlap ratios, whose effect on the temperature and strain distribution were discussed. As the heat transfer mode significantly influences the uniformity of the bending process, the variations in bending angles with negative and positive overlapping ratios have also been investigated. The ratio of the longitudinal and lateral curvatures decreased with the increasing overlap ratio. Therefore, the effect of the lateral side is more important for specifying the final symmetry of the part, playing a critical role in bending with higher overlap ratios. In a rectangular part, deformation of the lateral side was found to be more difficult, showing strong dependence on the length of the scanning track, compared with the space of the adjacent passes. Through process characterization, the double raster scanning process has been well understood and proved to be a feasible approach to 3D laser forming of rectangular parts.
关键词： Curvature,Overlap,Laser bending,Heat transfer,Laser forming,Raster scanning
更新于2025-09-12 10:27:22