Micro-pin Fin Research Articles

Neural network-based regression for effective parametric study of micro-pin fin heat sinks

Neural network-based regression for effective parametric study of micro-pin fin heat sinks

Machine-learning-based modeling of saturated flow boiling in pin-fin micro heat sinks with expanding flow passages

For high potential flow-boiling-based thermal management systems, to better understand the underlying flow physics and to present an effective predictive approach have critical importance. Different from the existing literature, this study, for the first time, takes the machine learning (ML) algorithms into consideration for flow boiling in expanding type micro-pin-fin heat sinks (ETMPFHS). A new database including saturated flow boiling data in ETMPFHS is obtained for various operational conditions. Mass flux (G = 150, 210, 270 and 330 kg m−2 s−1), inlet temperature (Ti = 40, 49, 58, 67 and 76 °C) and effective heat flux (approximately, qeff″= 241 to 460 kW m−2) are the variable parameters. In this study, advanced ML algorithms including Support Vector Machine (SVM), Artificial Neural Network (ANN), Regression Trees (RT) and Linear Regression (LR) are used. It is concluded that, for flow boiling in ETMPFHS, the ANN emerges as the most effective model for prediction of htp, ΔT, and ΔP, followed by SVM, while RT and LR present poorer results in terms of predictive accuracy and reliability. Trends of predictions of both the ANN and SVM nearly overlap the experimental data; while both the RT and LR show different trends against the experimental results.

Composite microstructured surface with micro-cavities and micro-ditches on micro-pin-fins for enhancing pool boiling heat transfer

In this study, a novel composite microstructured surface with micro-cavities and micro-ditches on micro-pin-fins was designed to enhance pool boiling heat transfer. To reveal the enhancement mechanism of the newly-designed composite microstructured surface, the pool boiling heat transfer performance on four types of microstructured surfaces was investigated in HFE-7100 under different liquid subcooling degrees. The experimental results show that the micro-pin-finned surfaces with micro-ditches at the side walls of each micro-pin–fin can enhance the rewetting ability of the surfaces, thereby enhancing the boiling heat transfer at high heat fluxes and improving the critical heat flux (CHF) in comparison with the base micro-pin-finned surface. Meanwhile, the wickability of the micro-pin-finned surfaces with micro-ditches was found to increase with increasing the number of micro-ditches. Furthermore, by fabricating both micro-cavities and micro-ditches on each micro-pin–fin, the composite microstructured surface with micro-cavities and micro-ditches is capable of not only utilizing the advantage of increasing the nucleation site density through the micro-cavity structures, but also enhancing the rewetting ability of the surface through the micro-ditch structures. As a result, the newly-designed multiscale composite surface can significantly improve the heat transfer coefficient (HTC) and the CHF simultaneously. Quantitatively, the achieved largest HTC and highest CHF are 5.12 W/(cm2·K) and 75.2 W/cm2, respectively, which are 6.24 times and 2.82 times, respectively, as high as those on a smooth surface at the liquid subcooling degree of 35 K.

Multi‐objective optimization of a Fibonacci phyllotaxis micro pin‐fin heat sink

AbstractThere are still significant technical challenges associated with thermal management of electronic devices such as microprocessors. To improve heat dissipation performance of integrated circuits, a new Fibonacci phyllotaxis design of circular micropin fin heat sinks has been developed. To minimize both chip temperature and pumping power, a multi‐objective optimization technique was employed. The effect of design parameters such as phyllotaxis coefficient, pin fin diameter, and pin fin height on response parameters was numerically investigated using the full factorial design of the experiment. Artificial neural network was coupled with MO‐Jaya, to arrive at a Pareto frontier of optimal compromise solutions. The optimal set of design variables were found to be a height of 300 μm, a diameter of 122.6 μm, and a phyllotaxis coefficient of 130 μm with an inlet velocity of coolant 2.263 m/s. The selected optimum design was then investigated numerically, and the outcomes were compared to those predicted by the MO‐Jaya algorithm. The final confirmed response variables were a maximum temperature of 51.6°C and a pumping power of 0.191 W. The results show that the Fibonacci phyllotaxis structure of the micro pin fin heat sink has better heat‐dissipating performance.

Experimental study on the hydrothermal performance of nanofluids-cooled heat sinks with diamond shape micro pin-fin structures

Modern electronic devices with small heat transfer areas have very high heat flux. As a result, high temperatures are attained by these devices. Proper heat dissipation must be done to avoid damaging them. Thus, thermal and hydraulic performance of novel heat sinks with two different diamond-shaped micro-pin-fin (MPF) arrangements, inline and staggered, are experimentally examined. This has not yet been reported in the research literature. Heat sinks (HSS) with dimensions of about 30 mm x 33 mm are fabricated from copper. MPFS are designed with a diamond shape and arranged in inline (DPFHS-I) and staggered (DPFHS-S) layouts. Hydraulic diameters of each flow channel are kept constant at 1.0 mm for DPFHS-I and DPFHS-S. At first, DI water flows through the test section under laminar flow. Reynolds numbers (Re) based on the hydraulic diameter ranged from 100 to 600. Then, SiO2–water nanofluids with various particle volume fractions (ϕ) are tested to determine their potential for heat removal and apparent pressure drop (ΔP) across the heat sink, compared to water. Wall heat fluxes ranging between 10 and 52 kW/m2 are applied. The effects of pin-fin layout, Re, and ϕ on the cooling performance, performance index (PI), and ΔP are examined. Experimental results illustrate that the thermal performance is augmented with increasing Re and ϕ. The DPFHS-S had around 3–10 % higher thermal performance than the DPFHS-I. Experimental data indicated that using nanofluid coolants had a small effect on the ΔP and pumping power. Finally, new correlations for the Nusselt number and ΔP are proposed that are simple and can be used in practical applications. Most of the predicted data lies within ±10 % of the experimental data.

Fluid flow and heat transfer characteristics of a microstructured microchannel heat sink under flow boiling condition

A microchannel heat sink (MCHS) is known as a heat dissipation device from the miniaturized electronic components and devices due to its capability to dissipate high heat flux from smaller surface area. However, the higher pressure drop and the uneven heat removal along the channel length are the noticeable disadvantages of MCHS. Though there are attempts to address these shortcomings, no existing study has been found to study the effect of positions of microstructures (micro-pin fin and blind holes) and combined effect of micro-pin fins and blind holes under flow boiling condition. Therefore, in the present study, an attempt has been made to logically explain the effect of various arrangements and positions of pin fins and blind holes in the selected twenty-four uniformly distributed stations on the thermohydraulic performance of MCHS through numerically predicted results. The objectives of the study have been attained using the following three analyses, flow boiling, (i) with saturated fluid inlet conditions (inlet Re = 500), (ii) with different inlet subcooling (20, 40, and 60 °C), and (iii) with different heat flux conditions (100, 150, 200 and 250 W/cm2). From the study, it is observed that the pin fin enhances heat transfer in single-phase flow and delays the phase change by disturbing the flow. The blind holes act as nucleation sites and help phase change heat transfer. It is also observed that the ratio of single-phase and two-phase length and arrangement of microstructures in these two regions predominately dominate the heat transfer and fluid flow characteristics of the microchannel heat sink. The optimum performance (maximum heat transfer coefficient and minimum pressure drop) is achieved when twelve pin fins are placed in the upstream half and twelve blind holes are located at the downstream half of the channel. However, design improvement is possible through more computational and experimental analysis.

Bidirectional interlayer cooling of 3D chip stack for temperature uniformity enhancement and hotspot mitigation

In this work, bidirectional interlayer cooling with both enhanced temperature uniformity and low flow resistance is proposed for effective 3D chip stack thermal management. Staggered uniform micropin fins and curved entrance and exit regions are elaborately designed. Experimental and numerical studies are carried out to investigate the cooling characteristics under different Reynolds numbers and heat fluxes. In comparison with common interlayer cooling solutions, counter-flow arrangement is achieved between the layers and vertical heat transfer within the chip stack is utilized. Heat fluxes of 300 W/cm2 and 100 W/cm2 are dissipated in the hotspot and background zones respectively. Total thermal resistance of 0.18 K/W is obtained. The maximum decrease in temperature difference is up to 66.2%. Both thermal resistance and coefficient of performance (COP) are considered and compared with the results from previous studies for comprehensive performance evaluation. The maximum COP of 11,523 is reached. The thermal and hydraulic performance advantages of the present design can be verified. The bidirectional interlayer cooling offers new potential for thermal management of 3D chip stack.

Multimodal machine learning for predicting heat transfer characteristics in micro-pin fin heat sinks

As three-dimensional integrated circuit (3D-IC) chip technology advances, thermal management has become increasingly important because of increasing heat flux from thermal stacking. Micro-pin fin-embedded cooling has emerged as a promising solution for 3D-ICs, offering better thermal and hydraulic performance than conventional microchannel heat sinks. It is also easy to integrate into existing 3D-IC structures, such as through-silicon vias between stacks. The utilization of two-phase flow in micro-pin fins further enhances temperature uniformity and improves the heat transfer coefficient by leveraging latent heat. Nevertheless, predicting thermal performance in micro-pin fin heat sinks under boiling conditions remains challenging owing to intricate geometric shapes and diverse operating conditions. The present lack of correlation or theoretical models poses a significant obstacle. To address this problem, our study employed a Multimodal machine-learning (ML) approach, combining image data capturing boiling patterns of two-phase flow and information about geometric shape and operating conditions, to predict heat transfer characteristics in micro-pin fin heat sinks. We utilized experimental data comprising 155 types of boiling heat transfer data with the dielectric fluid FC-72 in two micro-fin shapes directly etched on Si. Four ML algorithms (XGBoost, LightGBM, Multilayer perceptron (MLP), and Multimodal ML) were employed to predict thermal performance. The correlation coefficient analysis before learning revealed the influence of each type of measurement data on the heater surface temperature during two-phase flow. Prediction accuracy was measured using mean absolute percent error (MAPE), and the results were compared in terms of maximum and average temperature depending on the characteristics of each ML algorithm. Overall, the Multimodal approach demonstrated superior capability in predicting temperature distributions with spatial details, surpassing conventional decision-tree algorithms and MLP in performance. When trained with boiling images, the Multimodal ML model achieved remarkable precision, evidenced by a MAPE of 1.81% for the maximum temperature and 0.84% for the average temperature, highlighting its exceptional accuracy in mapping the heated surface temperature profile. By contrast, the traditional MLP model, which lacked training on boiling images, showed diminished accuracy, with a MAPE of 2.54% for the maximum temperature and 1.77% for the average temperature, indicating a comparative shortfall against the Multimodal model results.

Two-Phase Liquid Cooling for High-Power Microelectronics via Embedded Micro-Pin Fin Heat Sink

Two-Phase Liquid Cooling for High-Power Microelectronics via Embedded Micro-Pin Fin Heat Sink

Thermal-hydraulic performance enhancement of modified hexagonal micro-Pin fin heat sinks using rotational configurations

Nowadays, micro-pin fin heat sinks (MPFHSs) have shown promising performance in removing high heat fluxes in small dimensions and are widely used in electronic cooling applications. Among various techniques for thermal–hydraulic enhancement of MPFHSs, geometric design modification has been emphasized in this study, which focuses on investigating the orientation of the micro-pin fins (MPFs) as an overlooked but crucial parameter. To this end, rotational configurations of modified hexagonal MPFs, including co-rotation, alternating rotation, and counter-rotation have been investigated at rotation angles ranging from 0 to 60 degrees. In the numerical study, the copper MPFHS with a heat flux of 50 W/cm2 is cooled using water within the Reynolds number (Re) range of 400 to 1000. The results revealed that the rotation angle of MPFs governs the flow behavior around them. In general, counter-rotation configurations exhibited better thermal performance by providing the possibility of increased fluid mixing and contraction of low-velocity recirculation zones. However, the considerable increase in pressure drop in this configuration may limit its usability in higher Re regimes. By considering the compromise between pressure drop and heat transfer, the counter-rotation configuration with a 30-degree angle was selected as the optimal design. The optimized design results in an increase of approximately 50 % in Nusselt number (Nu) and up to 26.7 % in performance evaluation criteria (PEC). Furthermore, a supplementary experimental study confirmed the numerical results. It demonstrated the remarkable performance of the proposed design in removing heat fluxes ranging from 125 to 250 W/cm2, within the range of Re under investigation.

A novel heat transfer characterization method for a thermal management scheme of 3D-IC chips

A novel surface-modified silicon-based thermal management technology has been proposed for 3D IC architecture in this study. 2 × 2 cm2 double sides polished silicon chips’ surface with micro-fin (MF) and micro-pin fin (MPF) structures have been achieved by applying silicon microfabrication technology of deep reactive ion etching, which is applicable to the interlayer of 3D IC packaging technology. By integrating a mini wind tunnel with Raman spectrometer, the transient thermal property measurement system is originally designed to evaluate the cooling capability of the surface-modified silicon interlayer. Finite Element Analysis was involved to confirm this view by taking fluid dynamics and heat transfer into account. The sample with 100 × 100 µm2 MPF structure expresses the appropriate exponential decay time constant τ (with unit of 1), which is 4.71 and 8.53 under cooling and heating measurement conditions, respectively. This also proved that the combination of Raman thermometry with forced gas flow could be a relevant measurement tool for transient thermal property.

Heat transfer enhancement in multijet micropin fin heat sink

The thermal performance of tiny heat sinks with liquid cooling is being studied in order to solve the issue of electronics cooling. Increasing thermal performance while lowering pressure drop and maintaining a constant substrate temperature is a difficult task. The purpose of this study is to harvest the useful features of combination of microjet and micropin fins and explore the influence of geometrical features on fluid structures and heat transfer. To comprehend and assess the performance of a multijet heat sink with a micropin fin, three-dimensional numerical simulation is used in this inquiry. The three parameters under consideration are, the ratio of the jet diameter to the pin fin diameter (α), which ranges from 1.5 to 6.0; the ratio of the jet diameter to the jet standoff distance (β), which ranges from 0.75 to 1.5; and the pin fin pitch is determined by the ratio of the pin fin diameter to the pitch length (λ), which ranges from 0.1 to 0.8. The grid independence test is done to ensure accuracy in numerical results. The numerical scheme is validated by comparing numerical results with that of experimental results from literature. The results obtained from numerical simulation are analyzed. It has been found that improving heat transfer is not just caused by expanding the contact surface area; fluid structure vortex generation also affects overall thermal performance. Better overall performance is produced at lower values of α, β and higher values of λ. The ideal design parameters are α = 1.99, β = 1.431, and λ = 0.699, according to the optimization of geometrical parameters using a radial basis neural network surrogate model and particle swarm optimization. The jet Reynolds number is found to have no significant impact on the overall performance.

Investigation on the thermal and hydrodynamic performances of a micro-pin fin array heat sink for cooling a multi-chip printed circuit board

Multi-chip printed circuit boards (PCBs) with integrated functionalities are widely used in large servers. This study investigates the thermal design of a PCB with nine different chips by using a micro-pin fin array heat sink. Four types of micro-pin fin arrays, namely, the square-pin fin array (SPFA), round-pin fin array (RPFA), truncated-pyramid-pin fin array (TPPFA), and truncated-conical-pin fin array (TCPFA), are considered, with the TPPFA providing the best thermal and hydrodynamic performances. The fabricated TPPFA heat sink was experimentally studied, achieving a maximum temperature of 63.3 °C, a temperature nonuniformity of 6.5 °C, and a pressure drop of 3.1 kPa at a total heat transfer rate of 540 W. Numerical simulations are conducted to examine the detailed temperature and flow distributions in the heat sink, exhibiting relatively uniform temperatures in the areas with micro-pin fin arrays and beneficial secondary flows in the downstream of the micro-pin fins. Further numerical simulations are performed to reveal the importance of the type of the coolant and the temperature dependence of the thermophysical properties, as well as the validity of the field synergy principle in analyzing the thermal performance of the heat sink considered in this work.

Study of manifold micro-pin–fin heat sinks: application of rhombus-based topologies to organize three-dimensional flows

Study of manifold micro-pin–fin heat sinks: application of rhombus-based topologies to organize three-dimensional flows

Multi-Objective Optimization of Air-Cooled Perforated Micro-Pin Fin Heat Sink Via an Artificial Neural Network Surrogate Model Coupled With NSGA-II

Abstract This research aims to create an artificial neural network (ANN) regression model for predicting the performance parameters of the perforated micro-pin fin (MPF) heat sinks for various geometric parameters and inflow conditions. A three-dimensional computational fluid dynamics (CFD) simulation system is developed to generate dataset samples under different operational conditions, which are specified using Latin hypercube sampling (LHS). An ANN model is first obtained by optimizing the model hyper-parameters, which are then deployed to learn from the input feature space that consists of perforation diameter, perforation location, and inflow velocity. For accurate training of the ANN, the model is trained over a range of uniformly distributed data points in the input feature space. The developed multi-layer model predicted Nusselt number and friction factor with the mean absolute percentage error of 4.45% and 1.80%, respectively. Subsequently, the developed surrogate model is used in the optimization study to demonstrate the application of the surrogate model. A multi-objective non-dominated sorting genetic algorithm (NSGA-II) is used to perform the optimization of the perforation location, diameter, and inflow conditions. Negative of the Nusselt number and friction factor are chosen as objectives to minimize. A Pareto front is obtained from the optimization study that shows a set of optimal solutions. Thermal performance of the perforated MPF is increased between 11.5% and 39.77%. The optimizer selected a significantly smaller hole diameter at a higher location and a faster speed to maximize the Nusselt number and minimize the friction factor.

Temperature drop for CO2 gas flowing through multilayer micro-pin fin arrays

A reasonable theoretical calculation model is established, and an appropriate correlation formula is selected to calculate the flow and heat transfer of CO2 gas flowing through micro-pin fin arrays in a micro-cooler respectively under different working conditions. The inlet pressure of CO2 gas is 1.0 MPa, 1.5 MPa, and 2.0 MPa respectively, and the inlet temperature is 12 °C and 16 °C respectively. The results show that the cold end temperature of the gas decreases with the increase of CO2 gas inlet pressure and the decrease of inlet temperature, and the lowest temperature reaches -29.93 °C. The calculated results have the same trend as the experimental data, and the calculated values are consistent with the experimentally measured values, which demonstrates the calculation model’s logic.

Coupled Electrical–Thermal–Fluidic Multi-Physics Analysis of Through Silicon Via Pin Fin Microchannel in the Three-Dimensional Integrated Circuit

Abstract To solve the thermal management problem in the three-dimensional integrated circuit (3D-IC) with high integration and multilayer, this paper establishes a 3D-IC interlayer microchannel model with various embedded TSV micropin fins to explore the temperature distribution of chips and the flow velocity distribution inside the microchannel. The paper selects the sense amplifier and the half adder as the heat source of the memory and processor in the calculation model. The power densities of the sense amplifier and the half adder are 885 kW/m2 and 1.832 MW/m2 combined with the layout size, respectively. Meanwhile, the effects of the shape and arrangement of TSV micropin fins on the flow and heat transfer characteristics are investigated. The result shows that the 1.2:1 diamond micropin fin microchannel with staggered arrangement has the best overall flow and heat transfer performance. Compared with the basic circular micropin fin with the in-line arrangement, the average Nusselt number of this microchannel is improved by 3.20–3.37 times, and the maximum temperature of chips is controlled at 325.92–312.43 K for Re = 628–1819.

Dynamics of long bubbles propagating through cylindrical micro-pin fin arrays

Dynamics of long bubbles propagating through cylindrical micro-pin fin arrays

Rapid bubble growth within 200 μs in flat microchannels under “hot spot” heating conditions at ultra-high heat fluxes

The two-phase flow boiling in microchannels is an attractive cooling strategy for high-power density electronic/optoelectronic devices, while the exist of sub-millimeter “hot spots” characterized by ultra-high heat fluxes would degrade the reliability and safety for commercial and consumer applications. In this paper, the bubble nucleation and evolution characteristics of subcooled flow boiling in high aspect ratio flat microchannels were experimentally studied with the aid of high-speed visualization and infrared temperature measurement at localized heat fluxes exceeding 1.5 kW/cm2. Dielectric liquid HFE-7100 was used at mass flow rates ranging from 11.1 to 178.2 kg/(m2·s). Results show that the explosive boiling process was accompanied by an approximately linear bubble growth rate of about 20 m/s at about the first half of growth stage, and the time duration for overall bubble growth was less than 200 μs. The bubble nucleation was suppressed dramatically on the smooth bottom surface of the channel even at a localized “hot spot” heat flux above 2.5 kW/cm2. The introduction of staggered short micro-pin fin arrays at the bottom wall significantly lowered the threshold heat flux and onset temperature of bubble nucleation and reinforced the bubble growth to larger sizes. It is attributed to the reduction in the temperature gradient of thermal boundary layer adjacent to the heated wall, and it would be further reduced by increasing the micro-pin fin denseness. Even at quite high superheats on smooth and micro-structured surfaces, the heterogeneous boiling mechanism was proved to still work.

Modified hexagonal pin fins for enhanced thermal-hydraulic performance of micro-pin fin heat sinks

PurposeThis numerical study aims to investigate the modification of the hexagonal pin fin geometry to enhance both the thermal and hydraulic performance of the copper micropin fin heat sink with single-phase water coolant in a laminar regime. The heat sink performance evaluation criteria have been investigated for the parametric effects of vertex angle θ (10–120) and relative length (RL) (0.25–9) of hexagonal pin fins.Design/methodology/approachTo carry out research and reduce the computational cost, only one heat sink unit is simulated and analyzed using periodic boundary conditions on the side walls and includes a hexagonal pin fin and half channel on both sides to reflect the structural characteristics completely. The governing equations are also solved using finite volume method.FindingsThe results reveal that θ = 60 and RL = 1 yield the optimum thermal performance and heat sink performance is significantly influenced by the vertex angle and RL. The modified hexagon geometry improves fluid flow behavior by reducing the volume of the recirculation region behind the pin fin, preventing its effects on the downstream pin fins and restricting the thermal boundary layer development on its straight side. At Re = 1,000, the modified geometry enhances the average Nusselt number by 24.46% and the thermal performance factor by 23.89%, demonstrating the potential of modified hexagonal pin fins to enhance micropin fin heat sink performance.Originality/valuePrior studies suggest using the pin fins with a regular hexagonal cross-section to obtain better thermal performance. However, this comes with a higher pressure drop penalty. The modification of the hexagonal pin fin geometry has been investigated in this numerical study to enhance both the thermal and hydraulic performance of the micropin fin heat sink. Because little attention has been paid to the modification of the regular hexagonal pin fins, as a geometry inspired by natural honeycomb structures, its design optimization is relatively scarce, and a gap was felt in this field.