Liquid-cooled Microchannel Heat Sink Research Articles

Secondary flow through lateral passages to improve hydrothermal performance of liquid-cooled microchannel heat sinks

This study proposes a simple cost-effective concept to improve hydrothermal performance of liquid-cooled microchannel heat sinks utilized in high power density electronics. It consists of parallel microchannels comprising interdigitated cavities on sidewalls interconnected using lateral passages. With suitable misalignment of cavities in adjacent microchannels, secondary flow forms in lateral passages which can improve the heat sink performance. Different cavity shapes are chosen and hydrothermal performances are compared with that of a simple straight-channel heat sink. 3D numerical simulations are performed on a model consisting of a Gallium Nitride substrate as the heat source, a Silicon heat sink, and liquid deionized water as the coolant considering temperature-dependent thermophysical properties of Silicon and water. Compared to the base case, heat sink with prismatic cavities and lateral channels has the largest shrinkage of hotspot area and reduces hotspot temperature by 1.6 °C at Reynolds number of 160. This configuration enhances the average Nusselt number by 20.2% at the same Re. Moreover, implementing backward cylindrical cavities with lateral channels improves the Coefficient of Performance and Performance Enhancement Factor by 31.7% (at Re=40) and 22.7% at (Re=160), respectively. At the end, performance improvements proposed in the previous works are provided within an itemized review table.

Liquid Cooled Microchannel Heat Sink Based Peltier Solar Atmospheric Water Generator

To maintain the high RH value near dry air vent, increase the efficiency of Peltier with proper ventilation that is to make the heat escape easily, to provide more surface area for heat sink to cool down the air more effectively. Mass of the body is reduced, and durability is improved. RH value is maintained with the help of dry air vent. We can get benefits from a liquid cooled micro channeled heat sink which needs only a little space. It is suitable for the high flux heat dissipation and also gives a better result compared to generic convection method. It is used without reacting with the body frame. It is portable with help of 12V DC solar 10W. This system solves water scarcity in rural areas. We can especially use at hill stations as the humid conditions are the best.

Topology optimization of microchannel heat sinks using a homogenization approach

Topology optimization for heat sink devices typically relies on penalization methods to ensure the final designs are composed of strictly solid or open regions. In this work, we formulate a homogenization approach wherein the partial densities are physically represented as porous microstructures. This formulation allows design of thermal management components that have sub-grid features and leverages additive manufacturing techniques that can produce such partially porous regions within the build volume. Topology optimization of a liquid-cooled microchannel heat sink is presented for a hotspot over a uniform background heat input. The partial densities are represented as arrays of pin fins with varying gap sizes to achieve sub-grid-resolution features. To this end, the pin fins are modeled as a porous medium with volume-averaged effective properties. Height-averaged two-dimensional flow and non-equilibrium thermal models for porous media are developed for transport in the pin fin array. Through multi-objective optimization, the hydraulic and the thermal performance of the topologically optimized designs is investigated. The pin fin thickness is chosen based on the minimum reliable printing feature size of state-of-the-art direct metal laser sintering machines, and the gap sizes between the pin fins are optimized. The resulting topologies have porous-membrane-like designs where the liquid is transported through a fractal network of open, low-hydraulic-resistance manifold pathways and then forced across tightly spaced arrays of pin fins for effective heat transfer. The effects of the grid resolution and the initial design guess on the resulting topologies and performances are reported. The topologically optimized designs are revealed to offer significant performance improvements relative to the benchmark, a straight microchannel heat sink with features optimized under the same multi-objective cost function. The work demonstrates that representing partial densities as porous microstructures results in nearly resolution-independent performance at sufficiently-small grid sizes through the use of sub-grid features.

Heat Transfer Rate Optimisation of Ionanofluid Based Heat Sink Using ANSYS

Heat dissipation of various electrical and electronic devices has been a significant concern in the current years of modernisation. Many researchers proved that a liquid-cooled microchannel heat sink (MCHS) is an effective way of removing high heat load. Due to ionic liquids’ unique properties such as negligible volatility, non-flammability, high thermal stability, and ionic conductivity, this liquid is combined with nanofluids to synthesise a new class of potential fluids termed Ionanofluids (ionic liquid-based nanofluids). In this research, a numerical simulation of fluid flow and heat transfer characteristics of MWCNT (Multiwalled Carbon Nanotubes) based Ionanofluids as a coolant in a rectangular-shaped microchannel heat sink is analysed. The Two-step method is used for preparing the studied Ionanofluids consisting of 0.5 wt.% of MWCNT nanoparticles ultra-sonicated with a mixture of propylene glycol and 1-Butyl-3-methylimidazolium chloride ([Bmim][Cl]-ionic liquid) fluids. Copper micro channelled heat sink comprising 1 m channel height, 25 μm of channel diameter, and 0.7 m channel width is modelled and simulated with ANSYS-Fluent. The results showed that the heat transfer coefficient increases about 11.4% while the thermal resistance decreases about 15.18% by using the proposed ionanofluids with the concentration of 0.5 wt.% at Re=2000 compared with that of an MCHS with propylene glycol. Moreover, the pressure drop along the studied MCHS increased up to a maximum of 30 kPa for higher heat gradients. Ionanofluids decreased the thermal resistance and temperature difference between the heated surface of the MCHS and Ionanofluids inlet to a greater extent when validated with pure base fluid and previous studies. From the simulated results, a better cooling performance is observed with Ionanofluids compared to pure propylene glycol (PG) for the proposed microchannel heat sink.

Hydrothermal and entropy generation specifications of a hybrid ferronanofluid in microchannel heat sink embedded in CPUs

The objective of this numerical work is to evaluate the first law and second law performances of a hybrid nanofluid flowing through a liquid-cooled microchannel heatsink. The water-based hybrid nanofluid includes the Fe3O4 and carbon nanotubes (CNTs) nanoparticles. The heatsink includes a microchannel configuration for the flow field to gain heat from a processor placed on the bottom of the heatsink. The effects of Fe3O4 concentration (φFe3O4), CNT concentration (φCNT) and Reynolds number (Re) on the convective heat transfer coefficient, CPU surface temperature, thermal resistance, pumping power, as well as the rate of entropy generation due to the heat transfer and fluid friction is examined. The results indicated higher values of convective heat transfer coefficient, pumping power, and frictional entropy generation rate for higher values of Re, φFe3O4 and φCNT. By increasing Re, φFe3O4and φCNT, the CPU surface temperature and the thermal resistance decrease, and the temperature distribution at the CPU surface became more uniform. To achieve the maximum performance of the studied heatsink, applying the hybrid nanofluid with low φFe3O4and φCNT was suggested, while the minimum entropy generation was achieved with the application of nanofluid with high φFe3O4and φCNT.

CFD analysis of a nanofluid-based microchannel heat sink

Effective thermal management is a key for the continuous development of electronics, which are characteristics of modern life. It has a great effect on the lifetime, durability and reliability of these systems. A liquid-cooled microchannel heat sink is a compacted cooling part that used to provide better heat dissipation rates and low temperatures in electronic components. Nanofluids have been introduced as effective coolants to be employed in this type of heat sink to increase the heat dissipation rate. However, a comparative assessment of the thermal performance between commonly used nanofluids and water as coolants for microchannel heat sinks is still lacking. For this purpose, a computational fluid dynamics (CFD), non-isothermal, three-dimensional detailed model has been developed to simulate and analyze the fluid flow and heat transfer physiognomies. The results show that examining performance parameters as functions of Reynolds number is misleading since the thermophysical properties are different among each coolant, and that employing nanofluids in a microchannel heat sink is impractical as water is cheaper and safer.

Increasing the efficiency of a Peltier device by assessing the thermal performance of liquid-cooled microchannel heat sinks

Water is, arguably, Earth's most valuable and vital resource. Devices that extract water from the atmosphere have been intensely researched as a means of harvesting potable water in environments where it is otherwise scarce. One such device is a Thermoelectric Cooler (TEC); a device that utilises the Peltier effect to cool a system. TECs are a promising solution for atmospheric water generation (AWG) over their competitors due to their simplicity and refrigeration capabilities. Despite these advantages, TECs are still considered mostly inefficient as they demand relatively high costs and energy consumption. This meta-analysis focuses on optimising the efficiency of small-scale Peltier devices. It explores the means of optimising the liquid cooled heat sink by using a specific flow field microchannel configuration such that less pumping power is required to push the coolant and more energy can be saved. A combination of optimal operating current of the Peltier device and of a novel flow liquid-cooled microchannel heatsink configuration with bifurcated fins using Galinstan as a coolant promises a significant increase in water production per unit of energy consumption for the AWG system.

Thermohydraulic analysis of a new fin pattern derived from topology optimized heat sink structures

This paper presents a new fin pattern for liquid-cooled microchannel heat sinks. It is derived from topology optimized heat sink structures reported in our previous paper. The new fin pattern is composed of two types of fins, oblique fin and trapezoidal fin, and they are arranged in a semi-wavy manner. Numerical simulation is implemented to examine its heat transfer and fluid flow characteristics in detail. A flow phenomenon that is similar to Dean’s vortices is observed and results in enhanced flow mixing. The non-continuous fin pattern also avoids growth of thick boundary layers as they are initiated at the leading edges of each fin. Furthermore, size optimization based on the response surface method is performed to balance the heat transfer enhancement and pressure drop penalty. The new fin pattern is then compared with five other commonly used fin designs and shows the best performance in the studied flow range.

Topology optimization of liquid-cooled microchannel heat sinks: An experimental and numerical study

Electronics cooling is always a critical challenge for its small profile and high heat flux. Various microchannel heat sinks have been proposed in literature to achieve reliable and energy efficient cooling effect. They are mainly different patterned fin shapes originated from researchers’ experience. In this paper, we present the process of designing liquid-cooled microchannel heat sink fin geometries based on a numerical method, topology optimization. The optimization model is developed to find designs that satisfy heat transfer requirement with low pressure drop penalty. It is implemented based on a derived accurate 2D model with minimizing pressure drop as objective and average junction temperature as a constraint. Parameter study for different velocities and junction temperature constraints is performed. The optimized structures are then post processed under geometry constraints and analyzed by 3D CFD simulation. Size optimization is implemented on conventional straight channel heat sinks, which serve as the benchmark cases. Moreover, an experimental test loop is built to validate the 3D simulation of topology optimized heat sinks and straight channel heat sinks. The performance comparison shows that the topology optimized heat sinks could save up to 50.9% pumping power under the same thermal performance requirement. Detailed CFD analysis is then engaged to examine their thermohydraulic characteristics and reveal the reasons for their superior performance.

Enhancement of Hotspot Cooling With Diamond Heat Spreader on Cu Microchannel Heat Sink for GaN-on-Si Device

The diamond heat spreader has been directly attached between the test chip and the Cu microchannel heat sink for thermal performance enhancement of the GaN-on-Si device. In the fabricated test vehicle, the small heater is used to represent one unit of transistor. Experimental tests have been conducted on the fabricated test vehicle to investigate the performance. Two types of simulation models have been constructed in COMSOL, considering the multiphysics features and temperature-dependent material properties. The submodel in conjunction with the main model is constructed to predict the thermal performance of the GaN-on-Si structure. The heating power, which is concentrated on eight tiny heaters of size 350 $\,\times\,$ 150 $\mu{\rm m}^{2}$ , is varied from 10 to 50 W. With the diamond heat spreader attached to the liquid-cooled microchannel heat sink, the maximum heater temperature can be reduced by 11.5%–22.9%, while the maximum gate temperature can be reduced by 8.9%–18.5%. Consistent results from the experimental and simulation studies have verified the enhancement of the hotspot cooling capability using directly attached diamond heat spreader.

Solving Thermal Issues in a Three-Dimensional-Stacked-Quad-Core Processor by Microprocessor Floor Planning, Microchannel Cooling, and Insertion of Through-Silicon-Vias

The electronics industry is heading toward the three-dimensional (3D) microprocessor to cope with higher computing workloads. The 3D stacking of the processor and the memory components reduces the communication delay in multicore system-on-a-chip (SoCs), owing to reduced system size and shorter interconnects. The shorter interconnects in a multicore system lowers the memory access latencies and contributes to improvements in memory access bandwidth. The shorter interconnects in stacked architectures also enables small drivers for interconnections which further reduce interconnection-level-energy dissipations. On the down side, the 3D-stacked architectures have high thermal resistance, which in conjunction with poor thermal management techniques, poses a thermal threat to the reliability of the device. This paper establishes the significance of the microprocessor floor planning and single-phase microchannel cooling for solving the thermal issues arising in the 3D-stacked-quad-core processor. The 3D-stacked-quad-core processor considered in this study comprises of symmetric nonuniformly powered quad-core processor, liquid-cooled microchannel heat sink, dynamic random access memory (DRAM), thermal interface material (TIM), and heat spreader. The electrical through-silicon-vias (TSVs) between the processor and DRAM serve as interconnects, while the thermal TSVs reduce the internal thermal resistance. The effective cooling of the 3D-stacked-quad-core processor depends on the TSVs, quad-core layout and the optimized design of the microchannel heat sink for the desired coolant. The microchannel cooling of the 3D-stacked processor is done both by planar flow and impingement flow. The thermal efficiency of the cooling techniques is evaluated on the basis of hot spot temperature, hot spot spread, and number of hot spots.

Fast Thermal Analysis on GPU for 3D ICs With Integrated Microchannel Cooling

Effective thermal management for 3D integrated circuits (3D ICs) is becoming increasingly challenging due to the ever-increasing power density and chip design complexity; traditional heat sinks are expected to quickly reach their limits for meeting the cooling needs of 3D ICs. Alternatively, the integrated liquid-cooled microchannel heat sink has become one of the most effective solutions. In this paper, we present fast multigrid and block tridiagonally preconditioned graphics processing unit (GPU) based thermal simulation algorithms for 3D ICs. Unlike the CPU-based solver development in which existing sophisticated numerical simulation tools (matrix solvers) can be readily adopted and implemented, GPU-based thermal simulation demands more effort in the algorithm and data structure design phase, and requires careful consideration of GPU's thread/memory organization, data access/communication patterns, arithmetic intensity, as well as its hardware occupancies. As shown by various experimental results, our GPU-based 3D thermal simulation solvers can achieve more than 360× speedups over the best available direct solvers and more than 35× speedups over the CPU-based iterative solvers, without loss of accuracy.

Design and Optimization of Single-Phase Liquid Cooled Microchannel Heat Sink

Semiconductor devices for demanding automotive applications generate a large amount of heat (>100 Wcm2). These high power devices can be cooled off very effectively by liquid coolant flowing through the microchannel heat sink. Microchannel heat sinks are very attractive because of their compactness, light weight, and large surface-to-volume ratio. Higher surface-to-volume ratio results in enhanced cooling performance. In this paper, a systematic robust analytical method is presented for design and optimization of single-phase liquid cooled microchannel heat sink. Effects of various design parameters such as eccentricity and footprint of heat source or device, thickness of the heat sink base, channel aspect ratio, number of microchannels or fins, coolant flow rate, and thermal conductivity of heat sink material on heat sink thermal resistances and pressure drop are delineated. Finally, analytical results are compared with experimental data and good agreement is obtained. The analytical method helps to reduce the design cycle time and time-to-market significantly.

On-Chip Thermal Management With Microchannel Heat Sinks and Integrated Micropumps

Liquid-cooled microchannel heat sinks are regarded as being amongst the most effective solutions for handling high levels of heat dissipation in space-constrained electronics. However, obstacles to their successful incorporation into products have included their high pumping requirements and the limits on available space which precludes the use of conventional pumps. Moreover, the transport characteristics of microchannels can be different from macroscale channels because of different scaling of various forces affecting flow and heat transfer. The inherent potential of microchannel heat sinks, coupled with the gaps in understanding of relevant transport phenomena and difficulties in implementation, have guided significant research efforts towards the investigation of flow and heat transfer in microchannels and the development of microscale pumping technologies and novel diagnostics. In this paper, the potential and capabilities of microchannel heat sinks and micropumps are discussed. Their working principle, the state of the art, and unresolved issues are reviewed. Novel approaches for flow field measurement and for integrated micropumping are presented. Future developments necessary for wider incorporation of microchannel heat sinks and integrated micropumps in practical cooling solutions are outlined

A novel valveless micropump with electrohydrodynamic enhancement for high heat flux cooling

Integrated microchannel cooling systems, with micropumps integrated into microchannels, are an attractive alternative to stand-alone micropumps for liquid-cooled microchannel heat sinks. A new micropump design capable of integration into microchannels and especially suited for electronics cooling is presented. It combines induction electrohydrodynamics (EHD) with a valveless nozzle-diffuser micropump actuated using a vibrating diaphragm. A comprehensive numerical model of the micropump has been developed to study the combined effect of EHD and valveless micropumping. The numerical model has been validated using theoretical and experimental results from the literature. The flow rate achievable from the new micropump is presented and the effect of several key parameters on the micropump performance investigated.

Single-phase liquid cooled microchannel heat sink for electronic packages

The study of a single-phase liquid cooled microchannel heat sink for electronic packages is reported. Two flip chip ball grid array packages (FCBGA) with different chip footprints, 12 mm × 12 mm and 10 mm × 10 mm, were used for high heat flux characterizations. A liquid-cooled aluminum heat sink with finned base dimensions of 15 mm (L) × 12.2 mm (W) populated by microchannels was designed and fabricated. The microchannel heat sink was assembled onto the chip, using a thermal interface material to reduce the contact thermal resistance at the interface. The measured junction to inlet fluid thermal resistances ranged from 0.44 to 0.32 °C/W for the 12 mm chip under the test flowrate range. The higher thermal resistance range from 0.59 to 0.44 °C/W was obtained for the 10 mm chip due to the higher heat spreading resistance at the heat sink base. An analytical method that takes into account the simultaneous developing flow in microchannel heat sinks is developed to predict the pressure drop and thermal resistance. The calculations agree well with the measured pressure drop and thermal resistances. The respective thermal resistance elements are also analyzed and presented.

Integrated micro heat sink for power multichip module

Today, more and more compact converters with high current are required. The thermal environment is a key point to meet these requirements: the heat sink must be integrated as closely as possible to heat sources. Liquid-cooled microchannel heat sinks are very efficient and well adapted to the cooling of power components. Thus, a high-performance micro heat sink was made and tested under a power multichip module. First, the principle of the microchannel heat sink and a three-dimensional approach are presented. Then, a prototype and results are described. Composed of eight insulated gate bipolar transistor chips, the prototype has a current rating as high as 1200 A.