Heat Sink Design Research Articles

Model Predictive PI Circulating Current Control for Modular Multilevel Converter

Significant circulating currents in the modular multilevel converter (MMC) increase system losses and complicate heat-sink design. Conventional PI and PR controllers can achieve steady-state error adjustment, but are sensitive to parameter changes and model uncertainty, heavily relying on coordinate transformations and careful design of model parameters. Model predictive control (MPC) has the characteristics of simple design, good robustness, and excellent dynamic response; however, it encountered the complexity of adjusting weighting factors. This paper proposed circulating the current model predictive proportional integral control (MPPIC) method in abc reference frame. This hybrid control solution utilized the predictive model and traditional PI algorithm to combine the advantages of nonlinear and linear control. Compared with existing suppression methods, this method avoided complex mathematical operations and a selection of weight coefficients, was easy to implement, and can effectively suppress circulating currents under different modulation ratios. Simulations were conducted on MATLAB/Simulink to verify the effectiveness of the proposed control strategy. MPPIC can not only distinctly suppress the circulating currents, but also reduce the overall voltage fluctuation of sub-modules capacitors under different modulation ratios, and had almost no any adverse effect on the performance of MMC.

Multi-objective topology optimization and thermal performance of liquid-cooled microchannel heat sinks with pin fins

The optimized structures for the liquid-cooled microchannel heat sinks with different pin-fin arrays were designed via using the topology optimization method for the better performance, including minimization of the flow energy dissipation and the average temperature of the bottom surface, aiming to facilitate the more efficient design of microchannel heat sink for electronic chips’ cooling. The heat transfer and flowing performance was simulated with steady-state incompressible Navier-Stokes equation and the energy equation. Based on the rational approximation of material properties (RAMP) method, the mathematical optimization model for heat sink was established according to the multi-objective function. The Galerkin finite element method (GFEM) was employed to calculate the flow and heat transfer system. Furthermore, the globally convergent method of moving asymptotes (GCMMA) was adopted to deal with the mathematical optimization problem as the optimization method. The entropy generation analysis and comprehensive heat transfer factor were employed to evaluate the performance of the conjugate heat transfer problem of 3D microchannel heat sinks with various pin-fin structures. The calculation results reveal that the multi-objective optimal structure has good heat transfer performance, and the temperature distribution of the optimized structure is more uniform. As the same pumping power, the comprehensive heat transfer efficiency of the optimized inline and staggered pin-fin arrays increases by 31.20% and 32.18% compared to the smooth rectangular channel. Compared with the cylindrical pin-fin configuration with the same heat transfer area, the entropy generation rates of the optimized inline and staggered pin-fin configurations decrease by 4.67% and 4.25%, respectively. The results can provide theoretical basis and application support for the electronic chip cooling technology.

Design of a 22-kW Transformerless EV Charger With V2G Capabilities and Peak 99.5% Efficiency

This paper outlines the design process of a high-efficiency (99.5% peak) transformerless DC EV fast charger in conjunction with relevant UL standards on conducted harmonics and leakage current. The topology is a non-isolated transformerless design which allows for the elimination of the additional transformer volume and losses that are present in galvanically isolated topologies. Methods for calculating optimal switching frequency and inductance to minimize loss as a function of chosen switching device and power level are provided. Filter sizing and component values are chosen in conjunction with the previously determined optimal switching frequency and inductance. Heatsink design rationale are then derived. Experimental efficiency, switching waveforms, and output voltage and current quality results are provided. Industrial topology feasibility is shown through experimental adherence to relevant UL, IEC, IET, and IEEE standards.

Local hydrothermal characteristics and temperature uniformity improvement of microchannel heat sink with non-uniformly distributed grooves

In order to improve the temperature uniformity of bottom walls, a novel design of microchannel heat sink with From-Sparse-To-Dense embowed grooves (MC-FSTD) was proposed as well as a comparative one with From-Dense-To-Sparse embowed grooves (MC-FDTS). The local hydrothermal characteristics and temperature distribution variance of bottom wall of microchannel heat sinks were numerically investigated for Reynolds number (Re) ranging from 100 to 800. The results showed that the denser grooves led to lower flow velocity, lower local friction factor and higher local pressure as well as the lower bottom wall temperature (Tw) and higher local Nusselt number (Nuz). The local Nusselt number and the bottom wall temperature of MC-FSTD were 2.17 times higher and 9.1K lower than that of MC-SC at z = 10 mm, respectively. MC-FSTD also had the most uniform temperature of the bottom wall and the corresponding temperature variance was 6.42 times lower than that of MC-SC at Re = 795.38. The heat transfer entropy generation rate and the total entropy generation rate of MC-FSTD were also the lowest with an acceptable friction entropy generation rate. Finally, the effects of the decreasing magnitude (Li) of the distance between two adjacent grooves on the local hydrothermal characteristics and temperature uniformity of MC-FSTD were explored and the total entropy generation rate was further reduced to 5.22 × 10−4 W/K at Li = 0.015 mm and Re = 795.38.

Multi-level Reliability-Based Design Optimization (RBDO) study for electronic cooling: Application of heat sink based on multiple phase change materials enhanced with carbon nanoparticles

Phase change materials represent efficient performances in the thermal management field. However, the low thermal conductivity poses a serious restraint for electronic cooling applications. Recently, the use of multiple phase change materials and the dispersion of nanoparticles are the most recommended techniques to improve the performance of the heat sink. In this study, a developed heat sink filled with multiple phase change materials (PCMs) enhanced with carbon nanoparticles was proposed. First, a parametric study was carried out to determine the optimal pair of phase change materials and nanoparticles. Then, deterministic design optimization and various reliability-based design optimization methods are performed. The optimization and reliability problems are solved by coupling the MATLAB optimization toolbox and the ANSYS Finite Element Model. The optimization-reliability results prove the efficiency of the Robust Hybrid Method in proposing a reliable and optimal heat sink design filled with multiple nano-enhanced phase change materials. The temperature is reduced by 25 % (16,5 °C) and the discharge time is reduced by 8,69 % (14 min) compared to the baseline heat sink.

Thermal analysis and optimization of metal foam PCM-based heat sink for thermal management of electronic devices

Efficient thermal management in electric devices is highly essential for ensuring the reliability and durability of electronics. This study aims to investigate the thermal performance and optimization of metal foam PCM-based heat sink for thermal management units. Different design parameters, such as PCM types (RT31, RT42, and RT55), metal foam porosities (85%, 90%, and 95%), and metal foam materials, are studied to determine heat sink optimal parameters, considering various critical temperatures: 40 °C, 50 °C, 60 °C and 70 °C. The volume-averaged method is used to simulate the heat transfer, phase change, and fluid flow within the heat sink unit. Heat transfer between PCM and metal foam is established using a thermal non-equilibrium model. The results show that the usage of metal foam is conducive to the thermal performance enhancement of heat sinks. Among the three parameters, PCM types show a considerable effect on thermal performance of heat sinks, e.g., the maximum operation time of heat sinks with RT31 is about 5 times that of heat sinks with RT55 for the critical temperature of 40 °C. Among all the cases, heat sinks using RT31 and aluminum foam perform optimally, which can achieve the optimal design of heat sinks.

MMC-based heat sink topology optimization design for natural convection problems

The optimal design of heat sink using Moving Morphable Components (MMC) is presented for natural convection problems. The topology optimization design of the heat sink has a heavy computational burden. For one thing, the multi-physics model is a fully coupled nonlinear system, and for another, a large number of degrees of freedom (DOF) of the design variables are involved in the optimization process. The governing equations of the multi-physics model are composed of the incompressible Navier-Stokes equations related to velocity and pressure and the heat transfer equation related to temperature. A reduced-order model that simplifies physical quantities is introduced to reduce the number of state variables, and the Gaussian Seidel iteration algorithm is used to further reduce computing scale. Compared with the density-based topology optimization, the MMC-based topology optimization shows similar heat sink design through fewer design variables and good heat dissipation performance. In addition, the heat sink structure with fully explicit boundary information is obtained. The numerical results show that the number of components and the lower bounds of the components have an effect on the heat dissipation performance. As the number of components increases, the heat dissipation performance improves. However, when the number of components reaches a certain level, the heat dissipation performance reaches saturation. Moreover, the higher the processing accuracy of the mechanical equipment, the smaller the lower bounds of the components that can be designed, and the better the heat dissipation performance.

Geometrical effects of pins in a center cleared heat sink on thermal management of electronic systems

Thermal management of electronic components is becoming popular due to the extensive applications of electronic components in modern machines and automobiles. Natural convection heat transfer is preferred for electronic cooling in the unavailability of power supply or where high energy efficiency is desirable. Pin fin heat sinks offer effective cooling of such electronic devices even with the natural convection mode. Center-cleared pin-fin heat sinks offer better thermal management of a heated surface compared to conventional pin-fin heat sinks. The present work numerically investigates the thermal characteristics of center cleared solid cylinder, solid tapered, hollow tapered, and perforated hollow tapered pin fin heat sinks under natural convection. The numerical results are discussed in the form of steady state base temperature, heat transfer coefficient, mass-multiplied thermal resistance, volumetric heat dissipation rate, and effectiveness of different pin fin heat sink designs under varying power input from 2.15 to 10.75 W. The minimum mass-multiplied thermal resistance (RThM) is found to be 0.11 K.kg/W and the maximum volumetric heat dissipation rate is 1750.3 KW/m3 corresponding to the perforated hollow tapered pin fin heat sink design.

A bioinspired programmable Self-Organization approach for designing additively manufactured heat sinks

Heat sinks are pivotal components for enormous energy conversion and storage systems. While extensive efforts have been devoted to heat sink design, it is still substantially challenging to obtain heat sink structures that synergize the flow field and temperature field for high thermohydraulic performance. This study proposed a bioinspired programmable self-organization approach followed by systematic experimental and numerical evaluations, to design air-cooled heat sinks. Compared with baseline regular pin–fin arrays, the optimized heat sinks counterintuitively show a remarkable increase of Nusselt number by up to 60% and a dramatic decline of friction factor by up to 40%, which is induced by the improved velocity uniformity, larger contact area and lower form drag. This novel self-organization approach integrated with additive manufacturing potentially provides a powerful framework for future heat sink design.

Numerical Investigation on Thermal Performance of Plate-Fin Heat Sink Designs Subjected to Parallel and Impinging Flow

The electronic industry has been working for decades to improve the cooling efficiency of heat sinks by creating more advanced, efficient cooling technologies. However, heat dissipation remains the major problem in this highly competitive sector. Plate-fin heat sinks with and without fillet profiles were investigated and two new proposed designs for plate-fin heat sinks with half-round pins attached to the fin were developed in this study. Numerical analysis was performed using ANSYS FLUENT R21 to evaluate the thermal performance of the proposed designs. For the element optimization, the grid independency test was performed to obtain the optimal number of elements. A constant heat flux of 18.750 kW/m2 was applied at the bottom plate of heat sinks as the input parameter and two different flow directions e.g., impinging flow and parallel flow at various mass flow rate was also applied to study the base temperature, thermal resistance and Nusselt number of these designs. The study has shown that plate-fin heat sinks with fillet profile and corrugated half-round pins (PFHS 4) subject to parallel flow and plate-fin heat sinks with fillet profile and symmetrical half-round pins (PFHS 3) subject to impinging flow exhibit better thermal performance over other configurations. Hence, these design configurations have a potential to be applied in the future.

Experimental study of topology optimized, additively manufactured microchannel heat sinks designed using a homogenization approach

Topology optimization generates complex geometry heat sink designs having intricate features well-suited for fabrication by additive manufacturing. In particular, a homogenization approach to topology optimization creates microchannel heat sink designs wherein the material porosity distribution corresponds to microstructures of varying dimensions, thereby eliminating the need to penalize the porosities to achieve binarized solid/liquid designs. This approach is inherently able to take into consideration the capabilities and limitations of available additive manufacturing processes as the types of microstructures can be user-defined. The current study is the first to fabricate and experimentally test microchannel heat sink designs that are topology optimized using the homogenization approach. To this end, a multi-objective optimization is performed to generate a series of Pareto optimal designs that minimize pressure drop and thermal resistance. The effect of the grid resolution is investigated. The resulting topology optimized designs are found to have different geometries and performances with different grid cell sizes because this impacts the physical dimensions of the microstructures. A series of pin fin arrays with different grid cell sizes and fin thicknesses are fabricated using Direct Metal Laser Sintering of AlSi10Mg. The additively manufactured surfaces have high roughness which creates connections between pin fins with small gap sizes and creates tortuous flow paths. The smallest pin fin that consistently survived the fabrication process is ∼0.25 mm thick and hence series of topology optimized microchannel heat sinks with a 0.5 mm grid cell size are additively manufactured. The pressure drop and thermal resistance of the fabricated heat sinks are experimentally characterized, and the measured results lie on the Pareto optimality curve predicted by the topology optimization algorithm. This work demonstrates that the homogenization approach to topology optimization generates high-performance microchannel heat sink designs that can be achieved using available additive manufacturing processes.

Human body heat-driven thermoelectric generators as a sustainable power supply for wearable electronic devices: Recent advances, challenges, and future perspectives

Thermoelectric generators are devices that directly convert heat flux or the temperature difference between two hot and cold surfaces into electricity. With the advancement of the Internet of Things (IoT) technology and the development of wearable and portable devices, the issue of providing a sustainable power source is one of the main challenges in the development path of these tools. Creating electric power by harvesting the waste heat from the human body is one of the effective solutions in this way. For this reason, the development and improvement of the technology of wearable thermoelectric generators have received much attention recently. Due to the low-temperature difference between the two sides of wearable thermoelectric generators and the high thermal resistance between the skin and the heated surface of these modules, the performance of these systems is highly dependent on their structural parameters and environmental factors. In this paper, it has tried to review all the previous studies regarding the impact of structural factors (such as the matching of internal and external thermal resistances, geometrical parameters of the module, design of heat source and sink, and flexibility of thermoelectric module) and environmental parameters (including the effect of ambient air temperature and humidity, skin temperature, and the interaction of power consumers with thermoelectric modules). Based on the studies, it seems that in optimizing the performance of wearable thermoelectric generators (WTEGs), it is necessary to consider the effect of the human body's thermoregulatory responses, such as skin temperature and sweating rate. The change in skin temperature directly affects the performance of WTEGs, and the change in sweating rate can also affect the thermal resistance between the skin and the hot plate and overshadow the matching of thermal resistances during operation.

Sobol sensitivity analysis and multi-objective optimization of manifold microchannel heat sink considering entropy generation minimization

Manifold microchannel (MMC) heat sink has been widely employed as an efficient scheme for high heat flux cooling of electronic devices. The parametric optimization design of the MMC heat sink is the key factor that directly determines the thermal management performance. In this study, Sobol global sensitivity analysis is firstly applied to quantitatively evaluate the effects of four geometric design parameters and inlet volume flow rate on the MMC heat sink performance. A multi-objective optimization method combining space filling method, Back-Propagation Neural Network and NSGA-II is then established to minimum the thermal resistance, total pumping power and total entropy generation of MMC heat sink, in which TOPSIS method based on entropy weight is developed to select the best compromise solution from the Pareto-optimal solutions. Finally, the overall performance among different optimal solutions is compared to identify the effectiveness of the optimization results. The results show that the obtained optimum design parameters can provide more than 67% reduction in power consumption without scarifying thermal performance compared with the MMC heat sink published in the journal “Nature” by Erp et al. in 2020. In addition, the best compromise solution can be recommended as selectable for designer because it shows the best performance, which can boost the heat flux beyond 1000 W/cm2 with pumping power consumption 0.236 W. These results are of great significance to the design of advanced MMC heat sink for cooling electronic devices.

Heat transfer characteristics of thermally and hydrodynamically developing flows in multi-layer mini-channel heat sinks

In this study, a novel type of air-cooled heat sink is proposed, which consists of several layers of mini-channels. In this design, the hydraulic diameter is smaller than in conventional types of heat sinks, such as plate-fin heat sinks, and consequently, the achievable heat transfer rates are higher. To predict the cooling performance of this heat sink, an innovative analytical method is proposed, results from which are complemented by an extensive number of numerical simulations of the simultaneously developing flows, thermally and hydrodynamically, inside a rectangular channel of the heat sink. The results of the analytical method are compared against two- and three-dimensional simulations and good agreement is found, while from the simulations, correlations are proposed for the Nusselt number in these flows. Finally, the performance of the proposed heat sink is compared to a plate-fin heat sink. This comparison reveals that entropy generation in the latter is around 27% higher than in the former, and suggests a promising advantage of the proposed heat sink design.

Thermal performance analysis of aluminum, copper, and graphene nanoplatelets-doped nanocomposite heat sinks manufactured via stereolithography

The increase in the performance of electronic components causes more heat increase, which leads researchers to different products and different production methods for the heat sink (HS) designs used to cool them. This study focuses on the production of an HS with features such as faster production, lower cost, lighter production, and faster design by trying a new production method. In this study, four different geometries of the nanocomposite heat sink (HS) were successfully produced by stereolithographic. Three different nano-powders (nano-aluminum, nano-copper, and graphene-nanoplatelets) were added to the resin at a rate of 0.5% by weight. The produced 16 different nanocomposite HSs were analyzed for characterization. It was determined that they could be produced with a homogeneous distribution. The characterization of the produced nanocomposite HSs was analyzed. In addition, experimental and simulated findings were examined in terms of thermal performance. Experimental and simulation data have shown that angled and channel heat sinks have a superior design. Nanocomposite heat sinks doped with graphene performed much better than others. Nanocomposite heat sinks performed up to 6.5% better than pure resin heat sinks. Including the geometry effect, the performance rises to 10.7%, which means that the maximum junction temperature (Tj,max) of an LED lamp can be improved by about 11%. Thus, a smaller or lighter product option has come to the fore. This production technique may also be used to create complex heat sinks or thermal interface materials (TIM) for special applications. When limiting variables are eliminated, it will be feasible in the future to build HSs that are more effective.

Topological optimization of flow-shifting microchannel heat sinks

Efficient thermal management is required for electronic devices that generate multiple different spatially nonuniform thermal workloads during operation. Conventional heat sinks route coolant to all potential heat-generating regions of an electronic component which may result in unnecessarily broad dispersion of the coolant to regions that are sometimes inactive. To fully utilize flow for multiple potential thermal workloads, a “flow-shifting” design approach is proposed. A flow-shifting heat sink has multiple inlets, where the flow path from each inlet is optimized for cooling of a specific workload or heat map. Only the inlet corresponding to the active operating workload is open at a given time, while the rest of the inlets are kept closed until the operating workload changes, allowing a majority of the flow to be properly utilized for cooling the active heat map. This has the potential to allow many different optimal heat sinks to be simultaneously encoded into a single structure but brings forth a complex design problem to optimize the internal fluid flow pathways. A multi-objective topology optimization algorithm is implemented in this work for flow-shifting heat sink design generation. Microchannel heat sink designs are generated for a demonstration case involving two workloads. Designs optimized for flow-shifting between two inlets are compared to a benchmark that is optimized with only a single inlet. Pareto optimality curves, as well as the associated heat sink designs, are created that weigh between the thermal resistances of the two workloads. The flow-shifting designs are predicted to have lower thermal resistance under both workloads compared with every benchmark heat sink design generated along the Pareto optimality curve. Investigation of two designs selected from the Pareto curve showed that the flow-shifting heat sink achieved 10.7% and 6.8% lower thermal resistance at the two workloads relative to the benchmark. The flow-shifting approach is superior as it utilizes more flow rate for cooling the active heated region. The flow-shifting approach thereby allows for fixed heat sink structures that can be topologically optimized for many different possible heat maps and actively respond to changes in workload.

Influence of extended surface area of heatsink on heat transfer: design and analysis

PurposeLight emitting diode (LED) has been the best resource for commercial and industrial lighting applications. However, thermal management in high power LEDs is a major challenge in which the thermal resistance (Rth) and rise in junction temperature (TJ) are critical parameters. The purpose of this work is to evaluate the Rth and Tj of the LED attached with the modified heat transfer area of the heatsink to improve thermal management.Design/methodology/approachThis paper deals with the design of metal substrate for heatsink applications where the surface area of the heatsink is modified. Numerical simulation on heat distribution proved the influence of the design aspects and surface area of heatsink.FindingsTJ was low for outward step design when compared to flat heatsink design (ΔT ∼ 38°C) because of increase in surface area from 1,550 mm2 (flat) to 3,076 mm2 (outward step). On comparison with inward step geometry, the TJ value was low for outward step configuration (ΔTJ ∼ 6.6°C), which is because of efficient heat transfer mechanism with outward step design. The observed results showed that outward step design performs well for LED testing by reducing both Rth and TJ for different driving currents.Originality/valueThis work is authors’ own design and also has the originality for the targeted application. To the best of the authors’ knowledge, the proposed design has not been tried before in the electronic or LED applications.

Surrogate Model-Based Heat Sink Design for Energy Storage Converters

As forced-air cooling for heat sinks is widely used in the cooling design of electrical and electronic equipment, their thermal performance is of critical importance for maintaining excellent cooling capacity while reducing the size and weight of the heat sink and the equipment as a whole. This paper presents a method based on the combination of computational fluid dynamics (CFD) simulation and surrogate models to optimize heat sinks for high-end energy storage converters. The design takes the thermal resistance and mass of the heat sink as the optimization goals and looks for the best design for the fin height, thickness and spacing, as well as the base thickness. The analytical and numerical results show that the thermal resistance and mass of the heat sink are reduced by the proposed algorithms, as are the temperatures of the heating elements. Test results verify the effectiveness of the optimization method combining CFD simulation with surrogate models.

Cooling performance in a minichannel heat sink with different triangular pin-fins configurations

With the continuous progress of automotive new energy technology, the motor has become an important part of the power system, and the heat dissipation of insulated-gate bipolar transistors (IGBT) determines the reliability of the power system. Minichannel structure can be added to the thermal management system of new energy vehicles to improve the heat transfer capacity. Due to the growth of the boundary layer in the smooth minichannel flow channel, the cooling performance improvement was limited. Pin-fins and rib structures were used to break the boundary layer and increased the heat transfer area to enhance the heat transfer capacity. In this study, a numerical simulation model of minichannel with triangular pin-fins with different rotation angles was established and calculated using the SST k-omega method. The temperature field, velocity field, pressure, and vortex distribution under different configurations were discussed in detail. The jet area formed by the prism wall and the side wall of the minichannel would impact the wall and reduce the growth of the boundary layer. However, the stagnation area generated in the center and corner will reduce the improvement of heat transfer capacity. The thermo-hydraulic characteristics of different configurations at different Reynolds numbers (Re), such as Nusselt number (Nu), Darcy friction resistance coefficient (f), and performance evaluation criterion (PEC), were analyzed. As Re increased, the best and worst configurations changed, the best configuration changed from the 90°–120° structure to the 120°–120° structure, and the worst configuration changed from the 75°–60° to the 60°–60° structure. When the Re = 663, the influence of the front and rear rotation angle on the cooling performance was explored. When the rotation angle was closer to 60°, the cooling performance of the minichannel was better. And the closer the rotation angle was to 120°, the cooling performance was better. This has a reference effect on the design of minichannel heat sinks.

Hypervapotron heat sinks in ITER plasma-facing components—Process qualifications and production control toward series production

The hypervapotron heat sink designs have been adopted in the ITER plasma-facing components, namely for the Enhanced Heat Flux First Wall panels and Divertor Dome Plasma-Facing Units. The outcomes of recent discussion among the Domestic Agencies and ITER Organization on requirements for the qualifications and production controls are reported. In addition, the paper summarizes the hypervapotron design, manufacturing technology, and urgent R&D tasks identified in the discussion.