Conventional Heat Sink Research Articles

Design of heat sinks for wearable thermoelectric generators to power personal heating garments: A numerical study

To mitigate climate change attributed to the built environments, there have been tremendous efforts to improve air conditioning systems in the buildings. The possibility of harvesting body heat as a renewable energy source to power a wearable personal heating system is investigated. The aim of this study is to integrate a wearable personal heating system with a thermoelectric generator (TEG) that harvests the body heat which is used to convert it into electricity. Moreover, the interaction between the TEG configuration and power output is studied. The power generation of TEG system is obtained by COMSOL Multiphysics software. The simulation results concluded that all the four proposed heat sink configurations can improve the power output of the wearable TEG at 1.4 m/s and 3m/s compared to that of the reference model. Furthermore, the perforated and trapezium shapes of heat sinks have a significantly better performance in comparison to conventional heat sinks.

Enhancing thermal-hydraulic performance of counter flow mini-channel heat sinks utilizing secondary flow: Numerical study with experimental validation

Continual growth of hydraulic and thermal boundary layers along stream wise direction in conventional straight fin mini-channel heat sink (MCHS) causes gradual deterioration of their thermal performance. To enhance thermal-hydraulic performance by breaking and re-development of the boundary layers, this research aims to introduce a novel water cooled inter-connected counter flow mini-channel sink (ICMCHS). Two inter-connectors (ICs) were positioned transversely between two counter flow mini-channels (CMCs) which segmented the flow domain into three zones (zone 1–3). Secondary flow was generated through the ICs utilizing the pressure difference of the adjacent CMCs resulting in disruption of the hydraulic and thermal boundary layers. To examine the effect of the ICs location and width on the thermal-hydraulic characteristics of the counter flow mini-channel heat sink (CMCHS), the present numerical studies were carried out for nine different cases (case 1–9) by varying ICs width from 1 mm to 1.5 mm and ICs location from 4 mm to 9 mm. A corresponding conventional CMCHS was chosen as the base case in contrast to the newly proposed ICMCHS. Experiments were also carried out for CMCHS to validate numerical results, and excellent agreement was found between measured values and the corresponding numerical results. At the lowest considered Re (Re = 150), a maximum value of Performance Evaluation Criterion (PEC) was achieved to ~1.22 for the highest length of zone 1 and 3 and the lowest ICs width (case 7), whereas at the highest Re (Re = 1044), the maximum PEC value (~1.42) was recorded for the intermediate length of zone 1 and 3 and the highest ICs width (case 6).

Numerical investigation on hydraulic and thermal characteristics of micro latticed pin fin in the heat sink

Micro pin fin heat sinks are an indispensable component in high-power electronic devices that are intended to enhance the device's thermal performance. In this study, the combination of conventional pin fin and lattice structure are used to propose a new design of micro latticed pin fin. The thermal performance and the impacts of the flow states and morphological types on the new design are investigated through fluid-thermal coupled numerical approach.The results reveal that overall pressure loss shows a slight improvement by using the latticed pin fin when compared with a solid pin fin. However, only a cubic body-centered-cubic pin fin has a positive influence on hydraulic and thermal performance, using a vertex cube achieves the opposite results. In terms of weight reduction, using the latticed pin fin can reduce the volume of the heat sink by approximately 14%-17%. Considering both pressure loss and Nusselt number (Nu), the improvement of the thermal-hydraulic performance index (η) of the BCC-PF (cubic body-centered-cubic pin fin) heat sink is more than 140% compared with the conventional pin fin heat sink.

Millimeter-Wave Phased-Array Antenna-in-Package (AiP) Using Stamped Metal Process for Enhanced Heat Dissipation

This letter presents an unprecedented stamped metal antenna-in-package (AiP) concept for millimeter-wave multiple-input–multiple-output (MIMO) and phased array applications. The stamped metal antenna containing an aperture dually functions as an efficient heat sink. Moreover, the presented antenna topology can be mass-produced using a stamping technology, which is widely used for conventional heat sinks. The ground wall of the proposed antenna encompassed by the dielectric substrate, which is thermodynamically equivalent to a cooling medium, is connected to the shield structures to guide the convection heat emitted by the radio frequency integrated circuits (RFICs) and discharges this heat into free space. Details of the proposed AiP topology are discussed, and the parametric effects of the key design factors are quantitatively analyzed. To verify the proposed AiP, the optimized design is fabricated using standard printed circuit board (PCB) and press technology. The fabricated 1 × 8 subarray features an impedance bandwidth of 700 MHz with a center frequency of 28.5 GHz and a measured gain of 13.78 dBi. Computational fluid dynamics results ascertain that the proposed stamped metal AiP effectively discharges the heat emission generated from the RFICs.

Enhancement thermoelectric generators output power from heat recovery of chimneys by using flaps

This study proposes a new and effective way to improve waste heat recovery from chimneys using thermoelectric generators cooled by natural convection heat sinks. A modified heat sink equipped with a flap fixed at the top of its base is used instead of only the conventional heat sink. A three-dimensional model is presented and solved by using ANSYS Fluent and ANSYS Mechanical for the complete setup. The model simulates completely the heat transfer phenomenon surrounding the first three heat sinks as part of a column of thermoelectric generator modules covering a vertical chimney wall. Also, it simulates the thermal-electric phenomenon inside the thermoelectric generator to predict the thermoelectric generators output power at different operating conditions. The impact of flap's dimensions and material (conductive and non-conductive) on the thermoelectric generator performance is studied. The flap's depth varies from 14 to 50 mm and height from 20 to 35 mm. This modified heat sink achieves about 64% increase in the thermoelectric generators cooling rate, yielding an increase in their output power by 129%. Results prove that sing the proposed modified heat sink in cooling thermoelectric generators (passively) maintains the system simplicity with no running cost and performs more than double its performance.

A new passive PV heatsink design to reduce efficiency losses: A computational and experimental evaluation

The efficiency of photovoltaic systems is decreased when its operating temperature increases, which can affect the performance in arid climatic conditions. In this work, a new passive cooling system for photovoltaic panels is presented, with the aim of reducing its operational temperature and preventing a reduction in its electrical efficiency in unfavorable environments. With this aim, a series of 3D models of heatsinks were designed. The systems were evaluated through simulating normal operational conditions using CFD software. Prototypes of the models with the best performance regarding level and distribution of temperature were built for experimental evaluation. The use of a segmented aluminum sheet was proposed; allowing a better airflow, and therefore, improved cooling under high irradiance conditions. Numerical simulation results showed improved in temperature distribution and a reduction of up to 9.4 °C in the most effective heatsinks. Experimental results were in close agreement, achieving a reduction of around 10 °C during peak irradiance. Results of this work support the use of the integration of PV and passive cooling systems to reduce efficiency losses under real operating conditions, where there is a multidirectional nature of airflow, which may not be favorable for a conventional heatsink with a continuous channel design.

Experimental and numerical investigation of liquid-cooled heat sinks designed by topology optimization

In order to study the relationship between the thermal-hydraulic performances and the layout of cooling channels designed by topology optimization from the engineering perspective, two types of topology optimization problems are studied. The first is the flow distribution problem that is to achieve the minimization of power dissipation under the flow rate quality constraints, and the second is the heat exchange maximization problem that is to achieve the optimal thermal performances under the constant input power constraint. Then the optimized heat sinks together with a conventional S-shaped channel heat sinks are manufactured and their thermal-hydraulic performances are investigated both numerically and experimentally. The results reveal that the flow distribution design can provide the lowest hydraulic resistance while the heat exchange maximization design can keep the thermal resistance to a minimum. The proposed design method can be used as a tool to provide cooling solutions to the thermal management of high heat flux electronic components.

Improvements in Performance of a Self-Similarity Heat Sink Through Structure Modification

A self-similarity heat sink (SSHS) exhibits better overall performance than a conventional heat sink whereas although serious flow maldistribution still occurs. A modification to a conventional SSHS is proposed to overcome this disadvantage and obtain a more uniform heat transfer. Straight fins on the cover plate were replaced by zigzag fins to form a smaller incidence angle of fluid from the inlet manifold to the overflow channels, and the inlet manifold with constant cross-section was changed to a tapered inlet manifold to restrict excess flow to the downstream end of the inlet manifold. Numerical analysis was subsequently conducted to verify the modification. The results showed that the modification scheme successfully addressed the disadvantage of flow maldistribution of the original SSHS. Effects of the incidence angle on flow and heat transfer inside a single unit were analyzed at flow rates of 0.58–1.73 kg/h. The optimal incidence angle was found to be in the range of 20°–25°. For an entire SSHS with this optimal design, uniformity in flow distribution and heat transfer was significantly improved compared with original design, although the pressure drop increased slightly.

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.

Numerical analyses of hybrid jet impingement/microchannel cooling device for thermal management of high concentrator triple-junction solar cell

An efficient cooling arrangement is mandatory to achieve a higher net output power from the high concentrator photovoltaic structures in addition to extending their lifetime. In the current study, five new heat sink designs for a jet impingement/microchannel hybrid cooling scheme were investigated and compared with a conventional jet impingement cooling scheme. These designs consisted of an arrangement of rectangular fins at the streamwise length of the heat sink. This resulted in a stepwise decrease in the corresponding channel width and hydraulic diameter. A comprehensive three-dimensional thermal and structure model was developed to investigate the capability of the proposed designs in terms of reduction of the cell temperature besides enhancement of the temperature uniformity. Based on the results, the hybrid cooling scheme exhibited promising cooling ability compared to the conventional jet impingement scheme. The results of the present study show that the hybrid cooling scheme is effective cooling system and it achieved the utmost possible reduction of solar cell temperature, under high solar concentration ratio of 1000 suns where the solar cell temperature reduces to 55 °C. When the inlet mass flow rate was increased to 50 g/min under the same conditions, a corresponding reduction in the cell temperature from 67.3 to 55 °C was observed for Case 4 of the hybrid scheme designs. In addition, there was a decrease from 82.3 to 63.2° C for Case 1 of the conventional jet impingement heat sink (HS). Under the hybrid cooling scheme, the electrical efficiency of the cell improved to 39.7% when the inlet mass flow rate was equal to 50 g/min for Case 4. Exergy analysis revealed that the hybrid scheme achieved an overall exergy efficiency of 53.5% at inlet mass flow rate of 25 g/min.

Experimental investigation of flow boiling heat transfer performance in zigzag microchannel heat sink for electronic cooling devices

This study proposes an improved microchannel heat sink with offset zigzag cavities to enhance boiling performance. Flow and heat transfer characteristics are experimentally investigated via a microscale boiling heat transfer visualization system using acetone as the working fluid. At mass fluxes of 285, 402, and 684 kg/(m2·s) and heat fluxes of 1.31–80.26 W/cm2, the effects of heat and mass fluxes on flow pattern, heat transfer, wall temperature, and pressure drop of zigzag microchannel heat sink are analyzed and compared with conventional rectangle microchannel heat sink. Results show that the fluctuating amplitude first increases and then decreases with the increment of heat fluxes, thereby causing a quasi-steady and unstable boiling with small fluctuations. Instability becomes increasingly severe for the nucleate boiling area moves toward the inlet and flow reversal intensity increases with heat fluxes under low heat flux. With heat flux increased furtherly. The proportion of steam in the channel increases to reduce fluctuations. Compared with the rectangular microchannel, the zigzag microchannel evidently enhances heat transfer characteristic with lower wall temperature at the onset of nucleate boiling (ONB), higher heat transfer coefficient (HTC) and critical heat flux (CHF) and improves boiling stability by suppressing flow reversal and reducing two-phase pressure drop. The mechanism of zigzag microchannel enhancement boiling performance can be attributed to (1) the improved disturbance of the working fluid, which enhances forced convective boiling heat transfer and mitigates bubble coalescence and flow reversal strength; (2) the continuously developing liquid film and improved wettability maintain a stable liquid film evaporation and delay partial dry out. Increase in mass flux can improve CHF and reduce pressure drop albeit with high wall temperature of ONB. The local HTC is enhanced, except for the low heat fluxes, because the bubbles are condensed by liquid and cannot grow to absorb heat at low heat fluxes.

Performance Evaluation of a Loop Thermosyphon-Based Heatsink for High-Power SiC-Based Converter Applications

Thermal management system (TMS) of a power converter directly dictates the available power rating, power density, semiconductor module reliability, and its operating lifetime. For the latest-generation wide bandgap (WBG) semiconductor device-based converters, it is challenging to extract the generated heat from the devices due to smaller die area as compared to its silicon (Si) counterparts. In this paper, the thermal performance of a new loop thermosiphon-based TMS for silicon carbide (SiC) semiconductor device-based power conversion system is presented. The working principle and design of the TMS are shown, and the performance of the designed TMS in both transient and steady-state conditions of power dissipation is evaluated. Furthermore, an accurate thermoelectrical model of the TMS is presented, and the circuit parameters are quantified by experimental results. This analysis helps to estimate the device junction temperature in real time during converter operation. Moreover, detailed simulations are carried out with the derived TMS thermal model to evaluate its performance at low fundamental frequencies at rated currents. The experimental results and the simulation studies indicate that the TMS offers a low thermal resistance and can extract a large amount of heat without increasing the device junction temperatures beyond their rated values. Furthermore, the designed TMS is able to maintain the junction temperature ripples at low fundamental frequencies within small values, which helps to increase the lifetime of the power modules significantly, as compared to conventional heatsinks.

Lightweight, Superelastic Yet Thermoconductive Boron Nitride Nanocomposite Aerogel for Thermal Energy Regulation.

Conventional three-dimensional (3D) thermal conductors or heat sinks are normally bulky solids with high density, which is cumbersome and not portable to satisfy current demands for soft and flexible electronic devices. To address this issue, here, a lightweight, superelastic yet thermally conductive boron nitride (BN) nanocomposite aerogel is designed by a facile freeze-drying method. The attained aerogel constituting of tailored interconnected binary inorganic-organic network structure exhibits low bulk density (6.5 mg cm-3) and outstanding mechanical performances for compression, clotting, and stretching. Meanwhile, the aerogel has promising thermal stability and high thermal conductivity over wide temperature ranges (30-300 °C), validating the application even in extremely hot environments. Moreover, the aerogel can serve as a lightweight and elastic heat conductor for the enhancement of thermal energy harvest. Interestingly, during alternate strain loading/unloading under heating, the superelasticity and the anisotropy of thermal conductive transduction make the aerogel enable the elastic thermal energy capture and dynamic regulation. Therefore, our findings provide a potential use for the thermally conductive aerogel in future green energy applications.

Numerical Investigation of an Innovative Metal Structure in a PCM Based Heat Sink

Numerical simulations were performed to examine the time-dependent melting in a PCM enclosure with two designs of conductive metal fins: a baseline design with conventional heat sink fin structure and a topologically optimized innovative structure. Two orientations of the PCM enclosures were investigated to characterize the orientation effects on the behaviours of PCM melting. The proposed simulation model was firstly validated by the published experimental results. The simulated device temperature, material phases and flow fields within the PCM enclosure developed under different operating conditions were presented and discussed. The simulation results showed that the optimized design generally outperformed the baseline design by obtaining a lower device temperature and alleviating the effects of orientations. At q = 50,000W/m2, the optimized design achieved a maximum temperature reduction of 8°C under Orientation 1 and 2.5°C under Orientation 2 in comparison to the baseline during the main stage of PCM melting. It was suggested that the promoted heat transfer performance by the optimized design was attributed to the improved heat diffusion capability as well as the intensified natural convection provided by its innovative metal structure.

A novel micro-channel heat sink with trapezoid drainage for enhancing condensation heat transfer of dielectric fluid

This study experimentally investigates the condensation of dielectric fluid HFE-7100 in a micro-channel heat sink with the hydraulic diameter of 1.21 mm. Tests are conducted at a fixed pressure of 110 kPa, with vapor mass quality (xin) ranging from 0.1 to 0.9, mass fluxes (G) from 150 to 250 kg·m−2·s−1, inclined angle (θ) from −90° to +90°. A novel trapezoid drainage design is proposed to enhance the condensation heat transfer by effectively entraining condensation film. When G is lower than 200 kg·m−2·s−1, the two phase heat transfer coefficient (htp) for the trapezoid drainage design exceeds the conventional rectangular micro-channel heat sink by 10–26% while the corresponding pressure drop is about 22–45% lower. When G is increased to 250 kg·m−2·s−1, the drainage design can still dramatically decrease the pressure drop, however, it shows a negative effect on htp when the xin is greater than 0.2. With inclined arrangements, the pressure drop would dramatically increase due to gravity effect. Besides, at the conditions of θ = −45° and −90°, the trapezoid drainage channel can improve the htp by 43–45% when G is lower than 200 kg·m−2·s−1. On the contrary, with the arrangement of θ = +45° and +90°, the trapezoid drainage channels may decrease the htp by 8–15%. This phenomenon is especially pronounced at a high xin. In addition, the heat transfer enhancement and deterioration are both analyzed based on stress distribution at vapor phase and condensation film.

Experimental investigation of heat transfer and flow characteristics in finned copper foam heat sinks subjected to jet impingement cooling

The rapid development of electronic devices has made it necessary to develop novel and innovative thermal management solutions. This paper experimentally investigated the heat transfer and flow characteristics of three new finned copper foam heat sinks subjected to the impingement cooling by rectangular slot jet and axial fan. The effects of heat sink height (H, 15, 30, 45, 60 mm), the pore density of the inserted copper foam (PPI, pore per inch including 10, 20, and 30) and the gas flow Reynolds number (Re, varying from 2053 to 12737), were systematically investigated. Two kinds of conventional finned heat sinks, with 8 and 22 fins but without copper foam, were also tested for comparison. Experimental results reveal that inserting copper foam positively improves the thermal performance of finned heat sinks subjected to jet impingement. In addition, the thermal performance of finned copper foams with 20 PPI and 30 PPI even exceeds that of a conventional finned heat sink with 22 fins at a low height such as 15 mm, showing a great potential to replace traditional finned heat sinks. However, inserting metal foams leads to a much larger pressure drop than those of conventional finned heat sinks. From this work, finned copper foams are characterized by a better heat transfer performance than a conventional heat sink with the same number of fins. Even with increased flow resistance, finned copper foam heat sinks still have application prospects in some limited and narrow spaces where pump power consumption is not the dominant consideration.

Experimental investigations on heat transfer in a new minichannel heat sink

We report experimental investigations carried out on a new minichannel heat sink (nMCHS) comprising four compartments, each equipped with inlet and outlet plenums for coolant and rectangular minichannels with two miter bends in each channel. For comparison, the performance of a conventional minichannel heat sink (cMCHS) comprising minichannels of same hydraulic diameter as that of the channels in new heat sink was also studied. Reynolds number had a stronger influence on Nusselt number in nMCHS than that in conventional. The experimental data (Reynolds number range from 175.02 to 553.40; pumping power range from 4.47E-3 to 1.89E-1 W) reveals that the total thermal resistance was appreciably reduced in the new heat sink, due to higher heat transfer coefficients caused by developing nature of the flow. The coolant distribution in the new minichannel heat sink contributed to a significant reduction (60%) in substrate temperature gradient.

Effects of structural parameters on fluid flow and heat transfer in a serpentine microchannel with fan-shaped reentrant cavities

A three-dimensional numerical model has been conducted to study the laminar flow and heat transfer characteristics in serpentine microchannel with different geometric fan-shaped reentrant cavities for Reynolds number ranging from 150 to 980. The microchannel has the width of 0.1 mm and depth of 0.2 mm in the rectangular cross-section. The geometric parameters of fan-shaped reentrant cavities examined in this paper are 0.04058 mm for the width (Wc), 0.0084–0.02029 mm for the height (Hc) and 0.04058–0.12174 mm for the spacing (Sc).This study firstly presents the comparison of the thermal and hydraulic characteristics of serpentine microchannel with fan-shaped reentrant cavities with the conventional microchannels heat sink. Then the effects of fan-shaped cavities on velocity contour, temperature distribution and secondary flow features in such microchannel heat sinks are given. It is apparent that the fan-shaped cavities can effectively reduce the flow resistance and improve the temperature distribution uniformity. The effects of developed non-dimensional variables on the frictional pressure drop, average Nusselt number and the relationship between thermal resistance and pumping power in the novel channel are investigated. Compared with rectangular serpentine channel, heat transfer is enhanced for all cases and flow resistance is decreased besides Re = 980 and Hc/Wc = 0.2887. The best performance of serpentine microchannel with fan-shaped reentrant cavities is found at Sc/Wc = 3 and Hc/Wc = 0.2887.

1-D two-phase flow analysis for interlocking double layer counter flow mini-channel heat sink

Mini and micro-channel heat sinks with two-phase flow boiling are considered as one of the promising cooling methods due to their ability to efficiently manage high heat flux heat dissipation. However, it is characterized by a significant decrease in the heat transfer coefficient of the liquid deficient portion where the quality of flow is increased by the boiling in the channel. The heat transfer coefficient at which the wall dry-out occurs sharply decreases, which can cause a large temperature gradient in the direction of flow. Such a dry-out condition may correspond to the critical heat flux state, and a drastic decrease in cooling performance is inevitable. To alleviate the temperature gradient increase and to improve the cooling performance, the two-phase counter flow mini-channel heat sink with interlocking double layer structure has been proposed. The proposed mini-channel heat sink was designed based on the commercial IGBT module size and numerically analyzed by applying 1-D two-phase flow in each counter flow direction. Two-phase boiling heat transfer correlation and momentum equation were solved to calculate the pressure drop and analyze the cooling performance benefits of proposed counter flow heat sink. The applied analysis method was extended to the single-phase counter flow situation and the results were compared with two-phase flow case. From the results of the analysis, it was confirmed that the counter flow heat sink can obtain a more uniform temperature distribution than the conventional unidirectional heat sink. The non-uniformity of the temperature distribution due to the uneven flow rate of the parallel channels can be improved by applying the counter flow configuration.

Development of a Thermally Aware-Compact Model With an Optimized Heat Sink for FinFETs

In this letter, we develop a compact thermal model that can predict changes in the threshold voltage and drain current because of the junction temperature, Δ $T_{J}$ , and its effect on a circuit performance by using circuit simulators. In addition, we propose a thermally aware layout methodology for FinFET-based digital circuits. Although heat sinks (called “via pillars”) are generally used for heat dissipation in FinFETs, these features increase the parasitic capacitance and power consumption. Therefore, we propose an optimized heat sink that is only on the critical node (showing high activity and drain–source voltage, $V_{DS}$ ) and uses high metal stacks up to metal 5. With the optimization of this heat sink, we observe that the $T_{J}$ of a 4-input NAND gate can be reduced about 3.2% while the oscillation frequency of an 11-stage ring oscillator can be increased about 12%, compared to conventional heat sinks.