Papers by Keyword: Heat Sink

Abstract: In this work, we present a numerical study of mixed convection flows around large-scale heat sinks. It is based on the Cascade Lattice Boltzmann Method (LBM) for values of the Rayleigh number, in transitional regime, in the range 5×10⁷≤Ra≤5×10⁸ and for a Reynolds value fixed at Re=1000. The study is carried out in a rectangular cavity of dimension H subjected to periodic thermal and dynamic boundary conditions on its vertical walls. Two heat sources of (L', l', H/2) with a hot temperature T_h, are placed on the bottom wall of the cavity to simulate heat sinks. Fresh air (for cooling these heat sinks) is injected at a temperature T_c< T_h from the bottom of the cavity through two openings of length L''. The hot air is extracted through an opening (2L'' long) managed on the upper horizontal wall. The preliminary results, presented in this paper, are in the form of streamlines, isotherms and thermal profiles in the range of the Rayleigh number considered. Heat transfer is studied in terms of the average Nusselt number calculated over the entire surface of the two heat sources.

Abstract: Al-25%Si has excellent fluidity, which allows for the casting of heat sinks with thin and tall fins. During recycling, the content of impurities such as Fe, Cu, and Mg increases. The effect of these impurities on the fluidity of the alloy was investigated. The results show that the influence of impurity elements on fluidity is small. JIS ADC12 is a popular aluminum alloy that is more economical than Al-25%Si. Si was added to ADC12 to reach a 25% Si content, producing an economical Al-25%Si. The fluidity of Si-added ADC12 was almost the same as that of Al-25%Si. Heat sinks with fin heights of 50 mm, fin top thicknesses of 0.5 mm, and a draft angle of 0.5°, were cast using the Si-added ADC12. The molten metal filled the cavity, but solidification cracks occurred when the fin top thickness was 0.5 mm. When the fin top thickness was increased to 1 mm, solidification cracks did not occur.

Abstract: A heat sink is a cooling device that transfers the dissipated heat away from electronics to the surroundings. The testing method presented in the paper applies the nonequilibrium thermodynamic analysis of heat sink cooling curves. Here, the heat sink temperature time course is measured by using a thermal imager. The used thermal imager Flir T-640 takes single shots with recording of images. The proposed method validation test was performed on a selected heat sink. By analyzing the heat sink cooling curves, it is possible to obtain courses of the heat power and the heat sink surface to ambient thermal resistance. The presented testing method also enables a thermal analysis to distinguish between the convective and radiative components of heat transfer.

Abstract: This study investigates an enhancement of carbon-based materials, including multi-walled carbon nanotubes (MWCNTs) and graphite, through Ion Assisted Reaction (IAR) and metal nanoparticle deposition using Physical Vapor Deposition. The IAR process employed Ar⁺ ion beams in reactive gas environments, effectively introducing hydrophilic functional groups such as hydroxyl (-OH) and carboxyl (-COOH) on the MWCNT surfaces. This modification significantly improved dispersion behavior of the treated MWCNTs, particularly in non-polar solvents like N-Methyl-2-pyrrolidone (NMP). Results indicated that the treated MWCNTs demonstrated a slower sedimentation rate compared to untreated samples, with enhanced stability over 120 minutes in NMP. Graphite was modified with copper nanoparticles on its surface using magnetron sputtering in PVD system, leading to a uniform distribution of the modified graphite in matrix. SEM analysis revealed that this modification enhanced the surface roughness of the graphite, facilitating stronger interfacial adhesion with polymer epoxy resin. Composites incorporating these nanoparticle-coated graphite fillers (NPP graphite) exhibited superior thermal and mechanical properties. For instance, a 15% increment in thermal conductivity was observed in epoxy resin composites containing NPP graphite compared to those with untreated graphite. This improvement was attributed to the metallic Cu nanoparticles acting as thermal bridges, effectively transferring heat within the composite matrix. Mechanical properties were evaluated by blending modified fillers into polymer matrices, including polyvinyl chloride (PVC) and polyethylene (PE), with filler concentrations varying from 5 vol% to 15 vol%. Tensile testing and SEM analysis of the fractured surfaces indicated that NPP graphite composites achieved uniform dispersion, reduced agglomeration, and improved interfacial bonding. This study demonstrates that physical surface modification techniques such as IAR and PVD effectively overcome limitations associated with conventional chemical methods. This approach not only improves the dispersion and interfacial adhesion of carbon-based fillers but also enhances their thermal and mechanical performance.

Abstract: Nowadays, air coolers are extremely utilized at industrial and vital fields. Based on this significance, the paper exhibited the general concept of thermal and mechanical design of an air cooler heat exchanger model via COMSOL MULTIPHYSICS and Exchanger Design Rating (EDR) to obtain the most optimal thermal and operation conditions for boosting the heat exchanger efficiency. This was reached from the advantage of the integration between simulation software COMSOL MULTIPHYSICS and EDR have been used to enhance the operating and mechanical factors of the air cooler heat exchanger. The preference for using COMSOL and EDR are related to several factors, most notably the type of application to be simulated and detail level available for simulation. A simulation model of the air cooler was developed in EDR software and provided noteworthy results. Specifically, one of the marked outcomes is an increase of the overall heat transfer coefficient of 253.9 W/m².K in case 1 and 279.5 W/m².K in case 2 when compared to the baseline scenario of the as-built air cooler. The mechanical improvement proposed from the results of case 2 showed that it is possible to reduce the number of fans used by reducing the air flow rate by about 26%. At the same time, it provides the same thermal acting by cooling natural gas from 51°C to 37°C. Thus, reducing the amount of energy consumed by 61%, this is interested from an economic view point. A simulation of sample air cooler was carried out in COMSOL MULTIPHYSICS. With respect toward the results, a suitable design for the heat sink was reached, which provides acceptable thermal performance.

Abstract: Understanding heat transfer phenomena is crucial in high-power amplifiers to keep components within safe operating temperatures. This article investigates the GaN Power Amplifier (PA) thermal analysis for the optimum design of the heatsink. GaN PAs are roughly separated into junction, package, and heat sink layers to calculate the junction’s transient thermal response. It has been proven that allowing individual components to operate at temperatures over their maximum rated junction temperatures significantly reduces the system's operational reliability as a whole. This analysis investigates two different heat sinks for the optimum case temperature (T_case) for these different PAs. These PAs are operating S-band (2-3.4 GHz) and C-Ku-band (5-18 GHz) with drain efficiency of 60-65% and 9-22%, respectively. The design analysis of the heat sink for optimal performance is explored in this work.

Abstract: The aim of this study is to analyze the phase change material cooling performance integrated into heat sink experimentally. a paraffin wax as phase change material is used in this experiment and it placed under the heat sink with thickness 30mm , various power input at 11W,13W and 15W used in this experiment to generate heat at different levels also several fan speed at 15m/s,2.5m/s and 3.4m/s. the surface temperature of the heat sink is monitored over the time to evaluate the phase change material thermal performance . From the results ,temperature drop and the time lag in case of without PCM compared to with PCM shows the effect of cooling of adding PCM under low and high speeds of heat removal. It found that inclusion of PCM into heat sink with forced convection shows high temperatures drop up to 18 °C.

Abstract: In the present work, an experimental investigation has been made to analyze the performance of microchannel heat sink under transient operating conditions. The transient analysis has been made by estimating the response time for different input heat flux and coolant mass flow rate. Analysis has been made for rectangular cross-section microchannels fabricated on a copper block of size 25.7 × 12 × 10 mm³. Twelve (12) numbers of microchannels are fabricated in the copper block. The width and depth of individual channels are 400 μm and 750 μm respectively. Performance analysis has been made for both single phase and flow boiling conditions of the coolant flow using deionized water as coolant. Experiments have been performed for coolant mass flux (G) range of 90 - 250 kg/m²s and input heat flux (q) range of 20 - 300 kW/m² respectively. It has been observed that at constant input heat flux, response time decreases with the increase in coolant mass flux during single phase cooling. However this trend is not strongly followed during the two-phase or flow boiling cooling condition.

Abstract: The paper presents a study about thermal behavior of heat sink - power thyristor assembly. The models of power thyristor and the model of heat sink were modeled in SolidWorks. These models have been used in simulations. We take into consideration different conductor materials for heat sinks and different thermally conductive pastes. A thermal analysis has been performed for different places of power module on heat sink. In our study, we have taken into consideration the influence of the different materials of heat sink in heat dissipations. The results of performed simulations realized with Solid Works are presented in the paper.

Abstract: This research presents an experimental investigation on the heat transfer performance and pressure drop characteristics of a heat sink with miniature square pin fin structure using nanofluids as coolant. ZnO-water nanofluids with particle concentrations of 0.2, 0.4 and 0.6 vol.% are used as working fluid and then compared with the data for water-cooled heat sink. Heat sink made from aluminum material with dimension around 28 x 33 x 25 mm (width x length x thickness). The heat transfer area and hydraulic diameter of the each flow channel is designed at 1,565 mm² and 1.2 mm respectively. Uniform heat flux at the bottom of heat sink is achieved using an electric heater. The experimental data illustrate that the thermal performance of heat sink using nanofluids as coolant is average 14% higher than that of the water-cooled heat sink. For pressure drop, the data show that the pressure drop of nanofluids is a few percent larger than that of the water-cooled heat sink.