This work presents a numerical investigation of natural convection heat transfer in a zigzagged square enclosure fitted with circular baffles and filled with a radiative SWCNT-water nanofluid. The effects of baffle geometry, including radius and inter-distance, as well as the role of lateral wings, are analyzed to optimize the thermal performance of the system. The governing equations are solved using COMSOL Multiphysics based on the finite element method, incorporating magnetic field and thermal radiation effects. The results reveal that accounting for nanoparticle radiation enhances heat transfer by up to 40%, while enlarging the baffle radius from 0.05 to 0.1 increases convective exchange by 16.6%. In contrast, strengthening the magnetic field reduces heat transfer by approximately 34.4%. Furthermore, equipping the baffles with lateral wings improves heat transfer efficiency by 23.8% compared to the classic design. The study identifies an optimal baffle inter-distance of D=0.4, which maximizes convective heat transfer. These findings provide useful design guidelines for improving the efficiency of nanofluid-based heat sinks.

Reducing energy consumption across all sectors is both an ecological and economic imperative. Energy losses often manifest as heat dissipation, which reduces the energy efficiency of the system. This increase in junction temperature necessitates effective thermal management to maintain the high performance of the lamp. In this study, we conducted a thermal analysis of two heat sinks with different fin geometries, incorporating a Peltier module between the chip and the fins, and compared their performance in cooling an LED lamp.

The global development of LED lighting in all applications for both public and indoor lighting establishes a very important lever for reducing the carbon impact by significantly reducing energy consumption. Smart lighting will therefore constitute an essential lever in the smart city of tomorrow. The latter is more sustainable and less energy-intensive than other light sources, contributing towards the Sustainable Development Goals set forth by the United Nations (SDGs 7 and 11). With its ease of integration, ergonomics, lightness, and high quality of light, this innovative light source has two major qualities: its energy efficiency and its long service life. However, poor thermal management has catastrophic effects on these two essential criteria. This necessarily requires optimizing thermal management and heat sinks. In some cases, thermal models and simulations can lead to considerable calculation times because they implement many parameters. This work therefore aims to reduce the number of these simulations by applying the method of experimental designs (Taguchi) and analysis of variance (ANOVA) to simulations intended to optimize the dissipation of LED luminaires. We applied the method to a simple finned heat sink model for a unit input power and then to a concrete case of a high-power LED. The control parameters and their respective contributions in the proposed model were studied. The ANOVA results corroborated the conclusions of the Taguchi method, demonstrating a strong agreement between these analytical methods, in which the temperature was adjusted by identifying optimal combinations of parameters. The fields of application relevant to this study include both indoor lighting (false ceiling) and confined spaces with severe sealing constraints such as car headlights or the optical blocks of urban luminaires.

In this work, we analyze numerically, using Comsol Multiphysics®, the influence of four parameters (the power of the lamp, the ambient temperature, the angle of inclination of the lamp and the number of holes in the lamp cavity) on the evolution of the junction of a LED heat sink placed in a multi-hole cavity using a fractional factorial plan. Taking into account the results obtained, we optimize our model using the Minitab® manipulation software. Thus, a Pareto analysis (ANOVA) is carried out and a mathematical model is deduced to estimate the junction temperature of the LED lamp as function to the controlled parameters. The different influencing factors and especially the relative amplitude of their effect on the temperature of the LED chip could thus be calculated and demonstrated. If the electric power supply of the LED remains the first factor of impact on the temperature, the other parameters as well as the number of holes, the angle of inclination or the ambient temperature could thus be prioritized in order of influence.

This paper presents the results of a numerical investigation by design of experiments of the thermal management of a symmetrical rectangular heat sink for LED lighting placed in a cavity with asymmetrical conditions at its opening. Our mathematical model is validated by an experiment we carried out for an LED placed in a cavity. According to the proposed design of experiments (24 factorial designs), we analyzed, by simulation modeling using COMSOL Multiphysics®, the influence of the different controllable parameters (the position A and width C of the openings, the inlet air velocity B, and the cavity height D) on the evolution of the junction temperature in order to optimize the thermal management of the proposed LED lamp. Using Minitab® manipulation software, a Pareto analysis and an analysis of variance (ANOVA) were carried out, and mathematical models were deduced to estimate the optimal junction temperature and the convective heat transfer coefficient of the proposed radiator and the surrounding air as a function of the controlled parameters. It was found that the position of the opening is the most influential factor on the junction temperature, with a contribution of 93.46%, followed by the factors velocity and width of the opening, with low contributions (3.22% and 1.24%). We also observe that the height of the cavity and the interactions (A × C, A × D, B × C, B × D, C × D) have no significant influence on the junction temperature.

The present study details a numerical model of a positive DC corona discharge operating in dry air under atmospheric pressure. A coaxial geometry is considered, which is representative of configurations found in devices like electrostatic precipitators and electrohydrodynamic (EHD)driven air movers. The model consists of a central wire electrode ($100 \mu \mathrm{m}$ radius) to which a potential of 10 kV is applied, and a grounded concentric electrode separated by a 10 cm gap. The primary objective is twofold: first, to analyze the spatial distribution of charged particles and the electric field, and second, to provide insight into how these plasma properties constitute the driving force for the EHD phenomenon known as ionic wind. This work lays the essential groundwork for modeling the resulting gas flow by precisely calculating the EHD body force $\left(\mathbf{f} \_\mathbf{E H D}=\mathbf{\rho E}\right). { }^{\prime \prime}$

Ionic wind, also referred to as electrohydrodynamic (EHD) airflow, represents a promising solution for compact and silent thermal management of electronic devices. This study presents a detailed numerical investigation of a needle-to-plate ionic wind generator applied to the cooling of a heated plate representative of high-power LED modules. Fully coupled electrostatics-transport of diluted species-laminar flow-heat transfer model is developed using COMSOL Multiphysics in a two-dimensional domain. Activating the ionic wind reduces the maximum plate temperature from 454.40 K to 444.25 K, corresponding to a temperature reduction of 10 K. The EHD-induced airflow reaches velocities of $1.5-2 \mathrm{m} / \mathrm{s}$ near the impingement region, leading to effective localized hotspot mitigation rather than global heat removal. Parametric analyses highlight the influence of applied voltage, electrode spacing, needle height, and dissipated power. The numerical results are consistent with previously reported experimental and numerical studies, confirming the relevance of ionic wind cooling for localized thermal management in electronic systems.

Recently, thermal management of LEDs lamps has become increasingly essential due to the widespread integration of LEDs in smart lighting applications. In this work, we focus on the thermal analysis of convective heat transfer using a honeycomb heat sink designed for LEDs lamp cooling. Three different heat sink geometries were examined: an aluminum-filled honeycomb radiator, a hollow honeycomb radiator, and a hollow honeycomb radiator incorporating a phase change material (PCM) layer. The results obtained from numerical simulations using COMSOL Multiphysics (R) showed that the third heat sink geometry, when employed in short-duration lighting applications, led to a 25% reduction in temperature for a 20W power lamp. We also determined the optimal operational time, during which the temperature drop is maximum. Moreover, we observed that the integration of a PCM-filled honeycomb radiator in cyclic lighting applications (involving on/off cycles and high/low power settings) significantly mitigates temperature rise in the lamp by leveraging the PCM's heat storage capacity. This approach effectively prevents thermal shocks, ensures prolonged LEDs performance, and contributes to energy savings in the lighting sector. By addressing the thermal management challenges associated with LEDs lamps through innovative heat sink designs and the utilization of PCM, our research offers valuable insights for enhancing the overall performance and efficiency of LED lighting systems.

Ionic wind generation is a good candidate for cooling high power LED lights because it is both quiet, with no moving mechanical parts and very energy efficient. This preliminary work relates to a simulation of the corona discharge of a wire and two plates in air under atmospheric pressure. The results for the same structure are compared with previously published experimental work for ionic wind and temperature and are in good agreement. The use of a narrow diameter wire which achieves a positive corona discharge in air leads to the base plate of an electrode is shown. Hydrodynamics and electrostatics are taken into account in this model. The simulation presented concerns steady-state regimes with the discharge maintained with 9 kV applied to the inner electrode while the outer electrode is grounded. The inconvenient is the lack of a rigorous comparison with experimental airflow, air velocity and current-voltage result. These results are important because they are used as a method of cooling the heat sink of the high-power light-emitting diode, as verified in this work, and also to develop this effect for practical purposes. The dependence of the cooling efficiency on the distance between the plates and the wire was studied.

Plasma actuators generated by surface dielectric barrier discharge are developed for controlling flow in aeronautics applications. This research studies the simulation of cold plasma discharge at atmospheric pressure coupled with compressible fluid dynamics using COMSOL Multiphysics 5.4. Modeling of dielectric barrier discharge in air at high voltages is carried out in two dimensions. The development of electric field and space charge density are discussed in several cases to determine the discharge regime. Non-thermal plasma generates tangential ionic winds at the surface during corona discharge. The results are validated by the experimental results of the literature. The maximum electric wind velocity above the actuator grows linearly with the applied voltage, and simultaneously, the horizontal extension of the discharge grows with the applied voltage. The induced electrohydrodynamic force augments with the applied voltage amplitude, reaching saturation at higher voltages. Moreover, as the voltage rises, the discharge becomes filamentary, inducing a higher number of streamer pulses. Hence, the power consumption discharge increases abruptly as the voltage rises. In addition, the efficiency increases at higher voltage amplitudes and with the dielectric thickness. Our findings give a clear description of physical atmospheric plasma parameters in the surface discharge mechanism and the efficiency of the actuator plasma.

Thermal management of light emitting diodes (LEDs) packages is indispensable to maintain lower operating temperature. The present paper reports a numerical analysis of 45W LEDs module. Two forms of substrate and chips are compared. Results show that circular chips mounted on circular substrate provide lower junction temperature of the package thanks to the elimination of slide effects. Moreover, the disposition of chips is studied. In fact, junction temperature decreases by 8.72% when the pitch increases from 1 to 14 mm in the rectangular design, and it decreases by 7.46% when increasing the pitch from 1 to 12 mm in the circular design. However, it is found for both rectangular and circular configurations that the chips spacing causes a temperature difference between chips of the same package. The latter does not affect the light output but it causes a significant difference of chips lifetime: a difference of 1354 h between central and outer chips is noted with rectangular configuration, and 1331 h with circular configuration. This may cause a drop of the light output of the lamp when central chips fail and result in an optical discomfort for users.

Despite the continuous progress of its technology, thermal management of Light Emitting Diode packages (LEDs) still the key of their good performances and long lifetime. In this paper, a numerical analysis of 45WLEDs array is developed using COMSOL Multiphysics®. The PCB LED Board and the heat sink have circular forms. Thirty-six chips are arranged on the PCB following three circles around a central one. The spacing between them is the studied parameter used to highlight its effect on thermal and optical properties of the package. Results show that junction temperature decreases considerably when increasing the spacing from 1 to 12mm. However, it is found that smaller chips spacing causes a temperature difference between chips in the same package. Despite it does not affect strongly the light output, the temperature difference between chips causes a significant difference of chips lifetime in the same package, and causes a reduction of the amount of light produced when central chips fail.

With LED lighting systems, 70% of the energy consumed is lost in thermal form. It would be possible to increase the efficiency of the system by converting this wasted thermal energy into light. Some proposals using Peltier modules have been made. This article is interested in the limits of these solutions by evaluating the drop in the luminous efficiency of the LED system induced by the thermal effects generated by the addition of the Peltier module compared to the potential gain in terms of electrical power produced.

In this research, we studied the performance analysis of inductively coupled radiofrequency plasma "RF-ICP" torch used in multi-material processing. A 2D numerical model built with COMSOL Multiphysics was used to study the discharge behavior and evaluate the overall efficiency transmitted into the plasma system. The temperature and velocity flow of the plasma were investigated. The numerical results are consistent with previous experimental studies. The temperature and velocity profiles are represented under a wide range of RF power and for different sheath gas flow rates. With increasing power, the radial peak temperature typically shifts towards the wall. The resistance of the torch rises whereas the inductance diminishes with increasing RF power. The overall dependency of the coupling efficiency to the RF power is also estimated. The stabilization of the plasma flow dependency to the sheath swirl flow was investigated. The incorporation of Helium (0.02%) into an Argon gas was established to minimize the energy lost in the sidewall. The number and spacing of induction coil numbers affects the temperature and flow field distribution. A valuable approach to designing and optimizing the induction plasma system is presented in the proposed study. The obtained results are fundamental to specify ICP torch design criteria needed for multi-material processing.

Plasma parameters of radiofrequency discharge generated at low pressures in an argon-oxygen mixture addressed for biomedical surface sterilization have been optimized. Numerical results illustrate the density distributions of different species and electron temperatures during the electrical discharge process. The current discharge acting in the abnormal range decreases at higher oxygen gas flow rates. The temperature of electrons drops with pressure while it rises by adding oxygen. Nevertheless, electron density displays an adverse trend, exhibited by the electron’s temperature. The average particle density of the reactive species is enhanced in Ar/O2 compared to He/O2, which ensures a better efficiency of Ar/O2 in sterilizing bacteria than He/O2. The impact of oxygen addition on the discharge mixture reveals raised oxygen atom density and a reduction in metastable oxygen atoms. A pronounced production of oxygen atoms is achieved at higher frequency domains. This makes our findings promising for biomedical surface sterilization and leads to optimal parameter discharges used for sterilization being at 30% of oxygen gas ratio and 0.3 Torr pressure.

A three-dimensional numerical modelling of a time-dependent, turbulent thermal plasma jet was developed to synthetize silicon nanopowder. Computational fluid dynamics and particle models were employed via COMSOL Multiphysics®v. 5.4 (COMSOL AB, Stockholm, Sweden) to simulate fluid and particle motion in the plasma jet, as well as the heat dependency. Plasma flow and particle interactions were exemplified in terms of momentum, energy, and turbulence flow. The transport of nanoparticles through convection, diffusion, and thermophoresis were also considered. The trajectories and heat transfer of both plasma jet fields, and particles are represented. The swirling flow controls the plasma jet and highly affects the dispersion of the nanoparticles. We demonstrate a decrease in both particles' velocity and temperature distribution at a higher carrier gas injection velocity. The increase in the particle size and number affects the momentum transfer, turbulence modulation, and energy of particles, and also reduces plasma jet parameters. On the other hand, the upstream flame significantly impacts the particle's behavior under velocity and heat transfer variation. Our findings open the door for examining thermal plasma impact in nanoparticle synthesis, where it plays a major role in optimizing the growth parameters, ensuring high quality with a low-cost technique.

One of the practical solutions for mastering and reducing energy consumption on the one hand and protecting the environment on the other hand, is to use more effective lamps. LED lamps are the most efficient artificial light source. LED lamps have good performance. However, these electroluminescent diodes can suffer thermal dissipation problems since over than 70% of the energy supplied to the LED transformed into heat. The objective of this paper was to develop suitable cooling systems for A LED lamp. This is involving the use of heat dissipation device (either passive or active devices) such as the thermoelectric components and heatsinks.

Thermal management of light-emitting diodes (LEDs) for lighting is essential to ensure better performance since 7%-85% of its injected power is converted into heat. To increase the heat transfer rate, a heat sink is used to facilitate the natural convection heat transfer phenomenon. Thus, visualization of thermal flow around its heat sink is a powerful technique for developing conceptual models. In this paper, we compare the numerical results found by simulation with Comsol Multiphysics® using a rectangular heat sink with experimental visualization of the natural convection obtained by Schlieren imaging technique and then processed by Matlab®. Results show that this optical technique can be a promising technology to quantify thermal properties of the light source.

This paper presents a CFD study of ion wind generated airflow which is corona discharge induced flow at the tip of a curved electrode and represents a new cooling method for light emitting diodes (LEDs). The details of a numerical study of the natural convection around the radial radiator with a central pole for the 200 W LED have been examined. The effect of input current and interelectrode distance has been analyzed. We found that the optimal plate wire distance is about 17.5 mm where the velocity in the measuring point is maximum and that beyond 7 mm the velocity is inversely proportional to the applied voltage which minimizes the cooling of LED.