Composite Heat Sink Research Articles

Heat Transfer Enhancement for On-Chip Cooling Application Using Novel Composite Heat Sink—Comparative Numerical Study

This study investigates the enhancement of thermal performance of a composite heat sink (CHS). The novelty is that instead of embedding a conventional heat pipe at the bottom of base plate of the heat sink, a series of microheat pipes (MHPs) are embedded above, in such a manner that it replaces the solid fin arrangement. With this novel idea, the comparison of thermal performance of novel CHS with embedded MHP and micro-oscillating heat pipe (MOHP) is carried computationally using ANSYS-FLUENT-2019R1. The parametric study is carried out by varying the heat input in evaporator section and the convective condition in condenser section in accordance with the single fin of heat sink, and additionally different fill ratios in both MHP and MOHP are also considered. The thermal resistance modeling is used to calculate the effective total thermal resistance of the novel CHS using the volume averaged properties. The average temperature variation in single MOHP is found to be more which results in better performance than single MHP. The lowest thermal resistance of single MOHP is 0.827 K/W and single MHP is 0.969 K/W for 3.2-W distributed heat input and 35-W/ m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ·K convective condition. The total thermal resistance of novel CHS is more efficient than the conventional heat sink with solid fins by an average of 64.7% and 72.3% for MHP and MOHP, respectively, at considered maximum convective condition. Finally, the thermal resistance of novel CHS with MHP or MOHP is compared with the previously investigated CHS which seems to have enhanced heat transfer.

A silicon-diamond microchannel heat sink for die-level hotspot thermal management

• A silicon-diamond microchannel heat sink is introduced for microprocessor cooling. • Heat sinks are evaluated at various flow rates, heating conditions, and hotspot sizes. • The proposed design exhibits an excellent die-level hotspot mitigation capability. • A substantial improvement in performance is obtained at the same pumping power. • An extended diamond zone over the hotspot shows further performance enhancement. A novel microchannel heat sink with an excellent die-level hotspot mitigation capability has been introduced for electronic cooling applications. The basic concept of the proposed composite design is based on the dissimilarity in the thermal conductivities of materials. The microprocessor area was divided into multiple zones of different heat fluxes and the heat sink was developed using dissimilar materials for each zone. Silicon was used for the low-heat-flux zone and diamond with substantially higher thermal conductivity (ten times higher than silicon) was used for the high-heat-flux zone. The non-composite design was completely made of silicon with the same geometric parameters. A comprehensive numerical analysis of the composite heat sink was carried out and the results were compared with that of the non-composite heat sink. Both heat sink designs were assessed at various flow rates, heating schemes, and hotspot sizes. The thermal resistance, temperature non-uniformity, and pumping power were calculated to assess the performance of both heat sinks. The proposed design exhibited a substantial performance enhancement without any increase in the pressure drop or pumping power. Besides, the composite design was analyzed by varying the diamond zone size while keeping the hotspot size fixed which showed further enhancement in its performance.

Numerical investigation of different nozzle-jet distributions based on chessboard high-topology composite heat sink

Numerical investigation of different nozzle-jet distributions based on chessboard high-topology composite heat sink

Temperature Distribution Analysis of Composite Heat Sink (Pin Fin) by Experimental and Finite Element Method

Design of machine components plays a vital role in the field of Engineering where it includes the shape of component, size, applied loads, position and materials used. Due to the applied loads namely static, thermal and combined loads etc., the component undergoes stresses and deformations which affect the life of component and also the system. The Finite Element Method (FEM) is a numerical tool used for solving problems of engineering and mathematical problems in the fields of structural analysis, heat transfer, fluid flow, mass transport etc., For problems involving complicated geometries, loadings and material properties, it is generally not possible to obtain analytical solutions. These solutions generally require the ordinary or partial differential equations. Because of the complicated geometries, loadings and material properties, the solution can’t be obtained easily. So, in FEM the complicated shape of the component is divided in to small entities called elements. Element characteristics are studied and then all the elements are combined to make a single system of component. In the present work, Experiments have been conducted to find the temperature distribution within the pin fin made of composite metals and steady state heat transfer analysis has been carried using a finite element software ANSYS to test and validate results. The temperature distribution at different regions of pin fin are evaluated by FEM and compared with the results obtained by experimental work. The results are in good agreement and thus validated.

Phase Change Material Heat Sink for Transient Cooling of High-Power Devices

This paper reports a heat sink that uses a composite phase change material (PCM) made from a copper foam infused with a Field's metal eutectic alloy that melts at 60°C to achieve both high cooling and the ability to buffer transient temperature spikes. We integrate this composite PCM heat sink with circuit board mounted gallium nitride (GaN) devices that dissipate heat flux as large as 50 W/cm2. To design the PCM heat sink and understand its behavior, we developed a three-dimensional finite element method (FEM) simulation of the integrated assembly. We fabricated and characterized five composite PCM heat sink devices, where each device had a different PCM thermal buffer. The thermal buffers had varying Cu volume fraction and thickness. The PCM heat sinks were integrated with top-cooled or bottom-cooled GaN devices on printed circuit boards. Measurements of PCM heat sink performance showed that during phase change, the device junction temperature was reduced by 10-20°C compared to a solid Cu reference heat sink, depending on the device heating power which was as high as 6 W. The PCM heat sink cooling time was increased by up to 2X compared to a solid Cu heat sink of the same geometry. Finally, we developed and validated a reduced order resistance-capacitance (RC) circuit model that can guide the design of future PCM heat sinks. This work demonstrates the potential for PCM heat sinks to be integrated with high power GaN devices and shows methods for the design and modeling of PCM heat sinks.

Experimental study on temperature field of civil airplane wheel and brake

In this paper, a set of the temperature field experimental method of civil aircraft wheel and carbon-carbon composite heat sink material is established. The heat absorption performance of the carbon-carbon composite heat sink and the heat dissipation performance of the wheel structure were characterized by this method. Using this method, the temperature field experiment of the wheel and brake device of a civil aircraft is carried out, and the test working conditions of the temperature field of the civil aircraft are established, the curves of temperature change with time during normal braking, taxiing braking and cooling are obtained, and the maximum temperature and heat dissipation characteristics are obtained.

Experimental Investigation of Composite Phase Change Material Heat Sinks for Enhanced Passive Thermal Management

AbstractPhase change materials (PCMs) are effective at storing thermal energy and are attractive for use in electronics to smooth temperature peaks during periods of high demand; however, the use of PCMs has been somewhat limited due to the poor thermal properties of the materials. Here, we propose a design for a tunable composite PCM heat sink for passive thermal management in electronic systems and develop an improved test platform to directly compare performance between different designs and PCMs. The composite design leverages high conductivity pathways, which are machined into aluminum heat sinks, and back-filled with PCMs. Two package sizes are considered with several internal fin structures. All designs are evaluated using a test platform with realistic power profiles, controlled interfacial loading, and in situ temperature measurement. The composite PCM heat sinks are benchmarked against solid aluminum packages of the same size. This study focuses on three commercially available PCMs. Performance is evaluated based on (1) the time it takes the test heater chip below each composite PCM package to reach the cut-off temperature of 95 °C and (2) the period of a full melt-regeneration cycle. A range of heat fluxes are considered in this study spanning 6.8–14.5 W cm−2. The isokite design with PlusICE S70 extends the time to reach 95 °C by 36.2% when compared to the solid package, while weighing 17.3% less, making it advantageous for mobile devices.

Experimental and numerical investigations on the effect of porosity and PPI gradients of metal foams on the thermal performance of a composite phase change material heat sink

This paper reports the results of an experimental and numerical study on the thermal performance of a metal foam based composite phase change material (PCM) heat sink cylindrical in shape with porosity and PPI (pores per inch) density gradients. Studies are conducted on different configurations of composite PCM made of an open-cell aluminum metal foams with porosities of 0.9, 0.94 and 0.97 and PPI of 8, 14 and 20 encapsulated with n-eicosane as the PCM. Experiments are carried out on the PCM heat sink heated from the bottom for different configurations of metal foams with a uniform porosity and non-uniform porosity created with layer wise arrangement of metal foams from the bottom to the top. Complementary three-dimensional numerical simulations have been conducted using the enthalpy porosity methodology with a non-thermal equilibrium model to understand the melting and solidification dynamics of PCM while melting (charging) and solidification (discharging) respectively. Heat sink configurations with uniform porosity, and porosity gradient created with bi-layer arrangement of metal foams have been simulated numerically. Further, the numerical simulations have been extended to study heat sink configurations containing metal foams with uniform PPI density and PPI density gradient. From the results, it is seen that the case of non-uniform variation in porosity (decreasing from the bottom to the top) with constant PPI density and the case of non-uniform PPI density (increasing from the bottom to the top) with constant porosity show superior performance up to 28 and 45% over the heat sink configurations with uniform porosity and PPI density respectively in the charging cycle in terms of the time to reach a setpoint temperature. From the numerical simulations, it is seen that the melt fraction of PCM significantly changes the convection velocity cells, which affects the melting dynamics of PCM. Additional numerical simulations have been conducted on PCM heat sink with non-uniform porosity (i.e. decreasing porosity from the bottom to the top) and non-uniform PPI density (i.e increasing PPI density from the bottom to the top) gradients created with three layers (tri-layer) of metal foams. The results show that the PCM heat sink with non-uniform porosity and non-uniform PPI density gradients created with tri-layer metal foams have almost the same performance as a bi-layer metal foam with enhancement ratio up to 4 and 4.4 times respectively over the base line case (i.e. PCM heat sink without metal foams). In the discharging cycle, it is seen that the porosity and PPI gradients do not have any effect on the thermal performance of the heat sink.

An experimental study on flow boiling heat transfer of HFO1336mzz(Z) in microchannels-based polymeric heat sinks

This paper presents the development, evaluation and comparison of the performances of two microchannels-based polymeric heat sinks, manufactured with pristine polyacetal (POM) and with a POM-matrix composite filled with a volumetric fraction of 10% of multi-walled carbon nanotubes (MWCNTs). The thermo-hydraulic performance of both heat sinks was evaluated during flow boiling of refrigerant HFO1336mzz(Z) in multi-microchannels, for effective footprint heat fluxes up to 21.2 kW/m2, mass velocities varying from 100 to 300 kg/m2s, saturation temperature of 31 °C and inlet subcooling of 1 °C. Average heat transfer coefficients and pressure drops up to 2640 W/m2K and 1.5 kPa were achieved, respectively. The increase of the heat transfer coefficient and pressure drop were verified with rising the heat flux for both heat sinks. Fixing the average vapor quality, the average heat transfer coefficient and pressure drop increase with increasing mass velocity. The composite heat sink presented higher pressure drop and average heat transfer coefficient, which is associated with the higher surface roughness and mainly to the higher thermal effusivity of the composite in comparison with the pristine polymer. The addition of 10% of MWCNTs implied on temperature reductions at the base of the heat sink up to 22 °C.

Experimental Examination on Forced Convection Heat Transfer in laterally Perforated finned Metal Matrix Composite Heat Sink

Day by day a huge measure of research is proceeding to discover the cooling solutions for electronics including various applications for CPU, LED coolers, relay cooling frameworks. The serious issue including electronic parts cooling is the structure of heat sinks and their compatibility with the electronics for the predefined applications. Likewise, the quick-paced progressions in computing driving for the production of superior processors with incorporated complex circuits for which the cooling turned into a troublesome task which became challenging the existing market. This study targets building up a metal matrix composite (MMC) heat sink for low coefficient of thermal expansion (CTE) in electronic parts. Aluminum nitrate (AlN) takes like 12.5% (wt/wt) and mixed Aluminum (Al) to form metal matrix composite (MMC) prototype heat sinks. Prototype metal matrix composite (MMC) properties were evaluated experimentally. The modeling of the laterally perforated finned heat sink (LA-PFHS) is done Solid-works. The sinks are fabricated by using CNC machining. Two configurations of circular piercings on the fins are used in which the diameter and the spacing between piercings vary. In a rectangular insulated duct, the experimental analysis on the three metal matrix composite (MMC) heat sinks was performed under the phenomenon of forced convection at varying heat fluxes and at ambient conditions of temperature 30°C, pressure 101.326 KPa and 45% humidity. From 1.0 m/s to 4.0 m/s wind velocities and with an interval of 1 m/s the experimentation were carried out. Results show that the model III prototype metal matrix composite (MMC) heat sink proposed in this study shows a decrease in thermal resistance (Rth) by 50.51 %.

A novel composite pinfin heat sink for hotspot mitigation

A power-efficient composite pinfin heat sink has been introduced to mitigate the temperature non-uniformity in a microprocessor with heterogeneous heat flux distribution. The proposed composite design was evaluated numerically, and its performance was compared with a non-composite design. The concept utilizes the difference in thermal conductivities of different metals to develop an efficient cooling solution. The heat sink was divided into two zones (hotspot zone and background zone) according to the heat flux distribution. Copper and aluminum were selected for the hotspot and background zones, respectively. The non-composite heat sink was designed with exactly the same geometric parameters, however, aluminum was used for the background as well as the hotspot zone. Both designs (composite and non-composite) were analyzed at different flow rates and heating conditions. The temperature non-uniformity, temperature rise, thermal resistance, and pumping power were evaluated to compare their thermohydraulic performances. The composite heat sink showed substantial enhancement in the thermal performance without any change in the pumping power.

Experimental study on the heat transfer performance of a gallium heat sink

Phase change thermal storage technology has received considerable attention in the thermal management of electronic devices. Unfortunately, the efficiency using paraffin is too low to meet the heat dissipation requirements of high power devices. In this work, gallium is selected as the phase change material, and the melting mechanism of gallium heat sink in spatial distributions is examined by experiment. Results show that the heat transfer efficiency of regions in the Y-cross section near the heating surface and in the X-cross section near the upper surface of the gallium heat sink are better than other regions. The average effective thermal conductivity of the gallium heat sink reaches 71.97 W/(m·K). The natural convection promotes the overall melting rate, but it results in the inefficient heat transfer in the middle melting stage and worse heat transfer in the later melting stage. Compared with the copper foam/paraffin composite heat sink in the same size, the overall and most of melting time of the gallium heat sink is reduced by 55.5% and 56.0%, respectively. At the same thermal storage capacity, the volume and weight of the gallium heat sink are reduced by 67% and 18%, respectively, compared with the copper foam/paraffin composite heat sink.

Composite Heat Sink Material for Superconducting Tape in Fault Current Limiter Applications.

We enhanced the performance of superconducting tapes during quenching by coating the tapes with various composites, with regards to the application of such coated systems in superconducting fault current limiters. In composition of the coating, we varied the type of epoxy matrix, the content of ceramic filler particles and the use of reinforcement in order to optimize the thermal and the mechanical stability of the coated tapes. By this way modified superconducting tapes were able to reduce the maximum temperature 170 °C of not modified superconducting tape to 55 °C during the quench with electric field up to 130 V m−1.

Stress analysis of divertor plasma-facing component designs using tungsten particle-reinforced copper composite heat sink

The W-Cu composites are considered as advanced heat sink material for plasma-facing components, depending notably on the reduced macroscopic coefficient of thermal expansion compared with monotonic Cu materials. One class of such W-Cu composite materials is W particle-reinforced Cu composites which can be joined to pure tungsten parts as plasma-facing armor. After heat flux tests with 20 MW/m2 and with a target of 500 cycles, it is found that fracture occurred after around 100 cycles either on the side of W-armor or on the interface between W-armor and W-Cu composite heat sink. In this work, the stress as well as temperature processes during the cyclic heat flux loadings have been investigated with finite-element method for two designs with W-Cu composite materials, and compared with the former design with W-armor and CuCrZr-heat sink. Possible causes for the fracture have been proposed.

Numerical investigation on integrated thermal management via liquid convection and phase change in packed bed of spherical low melting point metal macrocapsules

This paper is dedicated to investigate the integrated cooling modality that the spherical low melting point metal (LMPM) macrocapsules were introduced and filled as phase change material (PCM) into a convective cooling heat sink. The fluid-solid heat transfer process coupled with phase change in the packed bed was numerically calculated based on the local thermal non-equilibrium theory and the effective specific heat capacity model which were validated in advance by conceptual experiments. The thermal management ability of composite heat sink packed with spherical LMPM-PCM macrocapsules under typical operating conditions has been revealed. In addition, the influences of different stacking patterns of LMPM particles, particle diameter and inlet velocity on the heat transfer enhancement in the packed bed were comprehensively investigated, respectively. It is found that compared with convective cooling heat sink alone, the composite heat sink filled with LMPM-PCM macrocapsules presents excellent thermal management performance. The temperature increment of heat source in the pulse heat load is reduced by 73.4%, which fully demonstrates the advantages of filling spherical particles. Besides, the Orthoclinal Stacking method achieves the largest volumetric heat transfer coefficient among different stacking patterns of equal-diameter spherical LMPM-PCM macrocapsules. What is more, the plateau duration of the solidification is gradually shortened with the decreasing diameter of the spherical LMPM-PCM macrocapsules and the increasing inlet velocity, which is advantageous for the system to quickly rehabilitate to normal operating temperatures during the de-pulse stage. Overall, this novel integrated cooling modality is proven to be a powerful and practical way to sustain extreme thermal management challenge.

Application of tungsten–copper composite heat sink materials to plasma-facing component mock-ups

The exhaust of power and particles is currently considered as one of the ultimate challenges in view of the design of a power producing magnetic confinement thermonuclear fusion device, like DEMO. One predominantly challenging aspect in this regard is the design and manufacture of divertor target plasma-facing components (PFCs) that have to sustain substantial particle, heat and neutron fluxes during fusion operation. With respect to the design of highly loaded actively cooled PFCs, copper (Cu) alloys are currently regarded as state-of-the-art structural heat sink materials (HSM). However, it has been underlined that the use of Cu alloys in PFCs implies issues mainly due to the behaviour of these materials under neutron irradiation characterised by a pronounced loss of ductility at lower and a loss of strength at elevated temperatures. These operating temperature limitations impose a strong constraint on the design of divertor PFCs and have regarding DEMO in the literature been termed a high impact design engineering risk. Against this background, the development of tungsten–copper (W–Cu) composites as potentially advanced HSMs for highly loaded PFCs was pursued by the authors during recent years. The progress of these developments is discussed in the present paper in terms of results of high-heat-flux tests conducted on PFC mock-ups that comprised W–Cu composite material heat sinks. Overall, the results of these tests indicate that W–Cu composites can indeed be regarded a viable class of advanced materials for the heat sink of highly loaded PFCs.

Thermal management of a semiconductor laser array based on a graphite heat sink.

Thermal analysis of a semiconductor laser array is carried out by establishing a packaging structure model of the array based on the use of copper as the base heat sink. A novel composite heat sink structure for a high-power semiconductor laser array with copper-implanted graphite microholes is proposed. The relationship between the location and quantity of microholes and the junction temperature of the semiconductor laser array is analyzed by numerical simulation. The packaging structure is found to effectively reduce the temperature generated by the semiconductor laser array in the process of operation, and the highest temperature is reduced by 4.52K. Since the laser diode bar is composed of multiple emitters, the temperature of the intermediate emitters is higher than that of the edge emitters. The structure of the graphite heat sink is optimized to improve the temperature uniformity of the semiconductor laser array emitter. Without changing the parameters of the semiconductor laser array device, the temperature difference is calculated, and a reduction from 7.68 to 2K is shown.

Thermal performance of modified polymeric heatsinks as an alternative for aluminum in heat rejection systems

Many studies have been conducted to obtain a viable alternative for metallic compartments in heat exchangers. The present research has been conducted to distinctly reveal the performance characteristics of polymer based composite materials as heat transfer medium. Various prototypes of polymeric fins with different volume fractions for multiwalled-carbon nanotubes, copper as components, and high density polyethylene (HDPE) as a matrix, were fabricated and stacked around copper pipes as an air/water finned-pipe heat exchanger. The thermal performance of each case was tested and compared with those of aluminum fins under the same conditions in a miniature mechanically pumped cooling loop (MPCL). Results indicate that for the airside, the difference between total heat transfer rates of the aluminum heat sink increased more rapidly than that of polymeric cases at the beginning, and became constant when a certain Reynolds number is reached. Further, for the best case of new composite heat sinks, a 451% and 52% enhancement in thermal conductivity and heat rejection were achieved, respectively, compared with the pure HDPE. The thermographic method also was used for better visual comparison among the materials. Finally, numerical simulations using ANSYS Fluent, indicated consistency with the experimental results of heat distribution for each case.

Three-Dimensional Printing of Abrasive, Hard, and Thermally Conductive Synthetic Microdiamond–Polymer Composite Using Low-Cost Fused Deposition Modeling Printer

A relative lack of printable materials with tailored functional properties limits the applicability of three-dimensional (3D) printing. In this work, a diamond-acrylonitrile butadiene styrene (ABS) composite filament for use in 3D printing was created through incorporation of high-pressure and high-temperature (HPHT) synthetic microdiamonds as a filler. Homogenously distributed diamond composite filaments, containing either 37.5 or 60 wt % microdiamonds, were formed through preblending the diamond powder with ABS, followed by subsequent multiple fiber extrusions. The thermal conductivity of the ABS base material increased from 0.17 to 0.94 W/(m·K), more than five-fold following incorporation of the microdiamonds. The elastic modulus for the 60 wt % microdiamond containing composite material increased by 41.9% with respect to pure ABS, from 1050 to 1490 MPa. The hydrophilicity also increased by 32%. A low-cost fused deposition modeling printer was customized to handle the highly abrasive composite filament by replacing the conventional (stainless-steel) filament feeding gear with a harder titanium gear. To demonstrate improved thermal performance of 3D printed devices using the new composite filament, a number of composite heat sinks were printed and characterized. Heat dissipation measurements demonstrated that 3D printed heat sinks containing 60 wt % diamond increased the thermal dissipation by 42%.

Cooling power and characteristic times of composite heatsinks and insulants

Thermal energy storage materials for transient thermal management applications must exhibit large energy storage densities as well as large cooling/heating power densities. The latter property has proven difficult to quantify on a materials basis because it depends on extrinsic effects. Here, we apply a previously defined cooling power figure of merit, a measure of a material’s intrinsic capacity to absorb a transient heat pulse, to analyze composite phase change material heatsinks and insulants. The results demonstrate important limits on the effects of high- and low-conductivity component volume fractions, orientations, and the critical lengthscales of individual components. Champion composites are predicted to have up to 5 times greater figure of merit than pure high-conductivity materials and up to 30 times greater figure of merit than pure phase change materials. Furthermore, composites consisting of insulating materials containing dispersed phase change materials are predicted to exhibit an order of magnitude increase in their characteristic response time. These results demonstrate the utility of the cooling power figure of merit to design compact high power and energy density heatsink and insulant materials.