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As electronics become more powerful and compact, laminated microchannel heat sinks (MCHSs) are essential for handling high heat flux. This study aims to optimize the MCHS design for improved heat dissipation and structural strength. An orthogonal experiment was established with the average surface temperature of the heat source as the evaluation metric, and the optimal structure was determined through simulation. Finally, cooling uniformity, fluidity, and performance evaluation criterion (PEC) analyses were carried out on the optimal structure. It was determined that the optimal combination was the triangular cavity microchannel (MCTC), with a microchannel width of 0.5 mm, a microchannel distribution density of 60%, and the presence of surface undulation on the microchannels. The result shows that the optimal structure's peak inter-layer stress is just 34.8% of its longitudinal tensile strength. Compared to the traditional parallel straight microchannel (MCPS), this structure boasts an 8.6 K decrease in the average surface temperature and a temperature variation along specific paths that is only 9.9% of that in traditional designs. Moreover, the optimal design cuts the velocity loss at the microchannel entrance from 75% to 59%. Thus, this research successfully develops an effective optimization strategy for MCHSs. [ABSTRACT FROM AUTHOR]

Technological advancements necessitate efficient electronic heat management, driving the need for effective cooling solutions. This study investigates the application of MXene-based nanofluids across varying concentrations in microchannel heat sinks to enhance electronic cooling performance. Utilizing numerical simulations, we analyze nanofluid concentrations, flow dynamics, and performance evaluation criteria (PEC) using an Eulerian model to characterize the inhomogeneous flow properties. Concentrations ranging from 0.01 to 0.04 vol% are incrementally examined, with validation against experimental data to ensure accuracy. Key findings reveal that at a Reynolds number (Re) of 300, a 0.04 vol% nanofluid fraction yields a 20.1% reduction in thermal resistance compared to pure water. Moreover, at Re 1000, the heat transfer coefficient improves by 29.4% compared to the 0.04 vol% concentration. These results underscore the potential of MXene nanoflakes as adequate heat sink working fluids for electronics cooling. Applications of this research extend to various electronic devices and systems requiring efficient cooling mechanisms. By leveraging MXene nanofluids, manufacturers can enhance thermal management in microelectronic components, such as integrated circuits, LEDs, and power electronics. Additionally, this study's insights can inform the design and optimization of cooling systems in high-performance computing, automotive electronics, and aerospace applications, where heat dissipation is critical for maintaining device reliability and performance. [ABSTRACT FROM AUTHOR]

Rectangular microchannel heat sinks (MCHS) are widely used to cool high-heat-flux electronic devices. However, previous studies focused mainly on MCHS with uniform channels (UCs). This study considers a microchannel heat sink with non-uniform channels (NUCs). A mathematical model is developed based on energy equations and the Darcy flow principle. Explicit expressions for total thermal resistance and coolant pressure drop are derived using the thermoelectric analogy. Experiments and numerical simulations are performed to verify the mathematical model. As non-uniformity increases, total coolant pressure drop decreases but at the cost of higher thermal resistance. The overall performance of NUCs is better than that of UCs because of their lower ratio of pumping power to cooling power. Heat transfer performance of NUCs changes little for more than 120 channels and depends mainly on channel arrangement. A multi-objective optimization is conducted to minimize the thermal resistance and pumping power of an NUC. An optimal NUC saves 64% pumping power compared with a conventional UC for the total thermal resistance of 0.1°C/W, indicating that the use of non-uniform channels could be very helpful to reduce the flow resistance of MCHS. [ABSTRACT FROM AUTHOR]

This study focuses on enhancing the performance of microchannel heat sinks (MCHSs) through the incorporation of longitudinal rectangular-sided grooves in conjunction with standard designs such as rectangular microchannels and converging microchannels. The aim is to improve hydrothermal properties, including fluid flow and the reduction in the pressure drop. The study explores the augmented heat transfer achieved by employing a higher-thermal-conductivity fluid along with the use of these grooves to disrupt the thermal boundary layer and induce secondary flow. Utilizing a 3D numerical model based on the finite element approach, investigations are conducted on a copper heat sink with slight variations in both hydraulic diameter and conjugated heated area. Silver/water nanofluid with different volume fraction values (0, 0.025, 0.05 and 0.075) is employed. Comparative analysis of pressure drops among conventional MCHS and other designs, namely rectangular with side rectangular grooves, converge (CMCHS) and converge with side rectangular grooves (CMCHS-WSRG) microchannel heat sinks, reveals that an increase in nanofluid volume concentration results in elevated pressure drop across all models. The design of RMCH and CMCHS without side rectangular grooves is shown to decrease the fluid flow pressure drop by 12.5 and 33.35%, respectively. Additionally, the study indicates that the average temperature of the heat sink base in CMCHS-WSRG is lower than in other designs. A comparison of the hydrothermal performance factor of the three models with the standard MCHS demonstrates that RMWSR grooves exhibit higher hydrothermal performance due to their larger conjugated heated area. The use of CMCHS-WSRG generates a higher velocity distribution compared to other designs. In conclusion, the incorporation of longitudinal rectangular grooves is found to enhance the hydrothermal performance of MCHS. [ABSTRACT FROM AUTHOR]

Copyright of Light Industry Machinery is the property of Light Industry Machinery Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Refrigeration is the property of Journal of Refrigeration Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The high-power laser diode (HPLD) has witnessed increasing application in space, as the aerospace industry is developing rapidly. To cope with the space environment, optimizing the heat-dissipation structure and improving the heat-dissipation ability via heat conduction have become key to researching the thermal reliability of the HPLD in space environments. Based on a theoretical analysis of the HPLD, a simulation model of the HPLD was constructed for numerical simulation, and it was found that the maximum temperature and thermal resistance of lasers were efficaciously decreased by changing the packaging position of laser bars. The packaging position of the bars and the cutting angle of the microchannel heat sink (MCHS) were determined based on the light-emitting angle of the light-emitting unit and the internal structure of the MCHS. The internal structure of the MCHS was optimized through a single-factor experiment, an orthogonal experiment, and the combination of neural networks and genetic algorithms (GAs), using three key structural parameters, namely the MCHS ridge width, W1, the channel width, W2, and the channel length, L1. After optimization, the performance of the MCHS was obviously improved. Finally, an analysis was carried out on the applicability of the optimized MCHS to bars with a higher power. [ABSTRACT FROM AUTHOR]

The microchannel heat sink with periodically arranged triangular cavities and arc‐shaped ribs (MC‐ARTC) is investigated numerically under the conditions of Reynolds number 147–736. The effects of triangular cavities and arc‐shaped ribs on velocity, pressure, and temperature distribution in the channel are analyzed in comparison with a rectangular microchannel heat sink, microchannel heat sink with arc‐shaped ribs, and microchannel heat sink with triangular cavities. The results show that the triangular cavity and the arc‐shaped rib have important effects on the flow and heat transfer characteristics in the microchannel heat sink. Both rib and cavity can cause a change in fluid flow direction and disturb the development of the flow boundary layer. The fluid flow and heat transfer characteristics of microchannels are improved. Among the four microchannels, the MC‐ARTC has the optimum comprehensive performance for the combined effect of the rib and cavity. Relative cavity width (β $\beta $) and relative rib height (θ $\theta $) are also defined to study the effects of cavity width (Wt ${W}_{{\rm{t}}}$ = 89–200 μm) and rib height (Ha ${H}_{{\rm{a}}}$ = 8.9–28.9 μm) on the flow and heat transfer characteristics. It is found that the heat transfer of MC‐ARTC is enhanced with increasing Wt ${W}_{{\rm{t}}}$ and Ha ${H}_{{\rm{a}}}$, while lead to higher pressure drop. When β $\beta $ and θ $\theta $ are 252 and 249 μm, respectively, the comprehensive performance factor (Pf ${P}_{{\rm{f}}}$) of MC‐ARTC reaches 1.76. [ABSTRACT FROM AUTHOR]

The reliable functioning of next-generation electronic devices within their temperature limits is contingent upon the efficient removal of high heat flux. Interfaces between the device, heat spreaders, and heat sink contribute significantly to thermal resistance in conventional chip packages. The elimination of interface resistances can lead to a noteworthy decrease in overall thermal resistance by incorporating the heat sink directly into the heat-generating device. The current study involved the manufacturing, simulation and experimentation of a micro channel heat sink. The micro channel assembly is manufactured with dimensions of 50 × 50 × 3 mm. The length of micro channel is 35 mm having height and width of 0.2 mm with 58 channels. The experimentation and numerical simulation was done with considering the various parameters like mass flow rate, heat flux, and inlet temperature of nanofluid. The microchannel heat sink improved electronic device thermal performance in fabrication, experimentation, and numerical simulation. The heat sink lowered device temperatures and prevented overheating. Nanofluid at 0.3% volume and at a mass flow rate of 8 m/s, the heat transfer coefficient reaches a maximum value of 13,693.00 W/m2 K at input temperature of 35 °C. The comprehension of the heat sink's performance was enhanced subsequent to the simulations, which unveiled the fluid flow characteristics and heat transfer mechanisms within the microchannels. [ABSTRACT FROM AUTHOR]

Microchannel heat sinks (MCHSs) are advanced cooling systems used in various applications such as electronics cooling, thermal management of high-power microprocessors, and microelectronic devices. These heat sinks are designed to efficiently dissipate heat generated by electronic components to maintain optimal operating temperatures and ensure device reliability. Employing appropriate fins within MCHSs is a crucial strategy to enhance heat removal efficiency. Since few investigations have been performed on the simultaneous thermo-hydraulic features in microchannels with Tesla valves, this research addresses this gap by suggesting that the microchannels of a heat sink be reinforced with novel Tesla valve-shaped fins. Tesla valves are designed to offer different levels of resistance depending on the flow direction. This characteristic allows for selective control of pressure drop and heat transfer efficiency by simply switching the flow direction. Utilizing Tesla valve-shaped fins is an almost new approach that differentiates the current research from conventional designs. The advantage of this structure is that under different circumstances, depending on whether more heat transfer is required or less pressure drop (ΔP), the flow direction can be changed, and the maximum efficiency of the MCHS can be accessed. The other innovative aspect of this study lies in the integration of artificial neural network (ANN) models to optimize the efficiency of MCHSs equipped with Tesla valve-shaped fins. The simulations were conducted to characterize the flow and thermal features of the MCHS. Then, these data were used as the benchmark for training the ANN models. Four ANN models were introduced to anticipate the Nusselt number (Nu) and ΔP in each forward and reverse direction. The divider's acute angle (α), the divider's obtuse angle (β), and the divider's radius (R) were selected as the input data. Multi-objective optimization and genetic algorithms were used to achieve the optimal conditions. In the optimal thermal design (Setting 2: MCHS with fin variables of α = 60 β = 180, and R = 80 μm in reverse flow direction), the overall performance had a significant enhancement of 57.1 % compared to the device lacking fins. Furthermore, in Setting 2, the overall performance of the MCHS and its diodicity experienced notable improvements of approximately 12.1 % and 38.5 %, respectively. Implementing the parameters of Setting 5 (MCHS with fin variables of α = 60, β = 152.32, and R = 73.10 μm in forward direction) during fin production resulted in a notable enhancement of about 41.1 % in the device's overall performance.

Owing to their high compactness, high-pressure resistance and superior heat transfer capability, compact heat exchangers and microchannel heat sinks are an integral part and play an important role in advanced hydrogen energy systems. In such miniaturized devices, numerous unit channels are typically installed in the core region between the inlet and outlet manifolds, resulting in fluid flow maldistribution which affects the thermal performance of the device. This review focuses on single-phase flow maldistribution and its effects on the thermal performance of miniaturized devices under typical thermal boundary conditions. An exhaustive literature review reveals that a popular belief within this research field is that lower flow maldistribution improves thermal performance. As a result of this belief, a large number of experimental studies were conducted under adiabatic condition. Further, methods developed to mitigate maldistribution were used regardless of the thermal boundary conditions. However, quantitative comparisons between these studies reveal that the relationship between maldistribution and thermal performance is non-linear, as maldistribution does not invariably cause negative effects and can even enhance the thermal performance under certain circumstances if properly utilized. None of the existing parameters adequately reflect this complex relationship. Finally, countermeasures against maldistribution are recommended depending on the specific thermal boundary conditions, and future research needs are outlined.

The improvement of the cooling performance of liquid‐cooled microchannel heat sinks used for densely packed electronic circuits is sorted via passive techniques like tuning substrate or coolant properties. We propose a design for enhancing heat sink performance by simulataneously modifying the channel geometry and tuning the fluid rheology. By modeling the coolant as a power law fluid, its rheological behavior is varied ranging from shear‐thinning to shear‐thickening, alongside Newtonian fluid. We introduced tapering to the middle wall that separates the bottom and top channels of a double layered microchannel heat sink (DL‐MCHS), causing both channels to converge. This convergence not only increases the flow velocity within the downstream microchannel but also reduces the apparent viscosity of the shear‐thinning fluid being subjected to shear, resulting in enhanced thermal and hydraulic performance. We analyze the results from both the first and the second law of thermodynamics context, demonstrating that a tapered DL‐MCHS with shear‐thinning fluid outperforms a straight partition wall DL‐MCHS with Newtonian coolant. However, we also discovered that extreme tapering compromises thermodynamic viability, but by fine‐tuning the extent of tapering, we inferred that a DL‐MCHS with shear‐thinning fluid can become viable with little compromise in the thermal performance. [ABSTRACT FROM AUTHOR]

In topology optimization of the microchannel heat sink, the minimum width of flow channels are constrained by the mesh size. To reduce the constraint of finite element mesh on the optimized structure, this paper proposes a mesh adaptive strategy which consists of finer ground mesh and coarser adaptive mesh for the heat sink design. The nodes of adaptive mesh are selected from ground mesh based on the structure of current iteration. The physical fields are solved on adaptive mesh, and design variables are updated on ground mesh. Besides, hyperparameters are introduced to control the adaptive degree, and their influence on optimized results is analysed in detail. Numerical experiments with simplified two-layer thermal-fluid model and parametric level set method show that the developed method outperforms traditional uniform mesh and is able to save large amounts of computing resources. [ABSTRACT FROM AUTHOR]

Copyright of International Journal of Engineering Transactions B: Applications is the property of International Journal of Engineering (IJE) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this study, three-dimensional modeling of a pulsating heat pipe is carried out, and the effect of physical and geometrical parameters such as filling ratio (FR), transverse distance (Z), and the number of loops (N) on its performance is investigated. In this study, it is assumed that the heat pipe is embedded in the microchannel heat sink, and its boundary condition is the thermal condition in the microchannel heat sink. The volume of fluid (VOF) multiphase flow model is used in the current numerical analysis. For the PHP, four different filling ratios (FR = 40, 50, 60, 70%), four transverse distances (Z = 2, 5, 8, 18 mm), and four numbers of loops (N = 1, 2, 3, 4) are considered, and the results will be compared with each other. It is shown that PHP with FR = 60% has the best performance. Also, comparing different values of transverse distance, Z = 18 mm has the lowest thermal resistance. The results show that by embedding a 4-loop PHP, the thermal resistance of MCHS decrease from 0.0268 to 0.0221 K/W, which indicates a 21.27% increase in the thermal performance of the microchannel heat sink compared to the basic design (without PHP). [ABSTRACT FROM AUTHOR]

The present study presents the recent research progress on enhanced heat transfer in microchannel heat sinks for cooling media. It describes the mechanisms behind enhanced heat transfer using nanofluids, liquid metals, and latent heat functional fluids. Furthermore, it explores various factors that affect the heat transfer performance of nanofluids, such as nanoparticle types, volume fractions, and temperatures. Additionally, it discusses methods to increase the heat transfer coefficient of liquid metals and analyzes how wall materials of microcapsules, phase-change materials, and mass fractions of microcapsules influence the heat capacity of latent heat functional fluids. Moreover, this study highlights the limitations of these three cooling media and proposes corresponding improvement measures. These findings provide valuable guidance for selecting appropriate cooling media in high heat flux equipment. [ABSTRACT FROM AUTHOR]

In this study, the effect of the presence of a pulsating heat pipe on the geometrical parameters of the microchannel heat sink will be investigated. The embedding of a pulsating heat pipe (PHP) in the solid part of the microchannel heat sink (MCHS) increases the cooling performance of the MCHS and reduces the maximum temperature of the electronic piece. A numerical investigation of MCHS equipped with a PHP is investigated and compared with an optimized conventional MCHS without PHP. The inverse problem solution approach is used to optimize the geometric parameters of the MCHS. The geometrical variables in the optimization process are N (number of channels), α (aspect ratio of the channel), and β (width ratio of the channel to pitch). The pumping power is considered a constraint and is tried to reach the minimized objective function (thermal resistance (R)). Results show that the optimal values of geometrical and physical parameters change from N = 100, α = 13.9, β = 0.6, R = 0.0268, in conventional MCHS to N = 120, α = 14.3, β = 0.7, R = 0.0231 in MCHS with PHP. At this point, the system's thermal performance improved by 16.02% compared to the previous optimal state. [ABSTRACT FROM AUTHOR]

As electronics become more powerful and compact, laminated microchannel heat sinks (MCHSs) are essential for handling high heat flux. This study aims to optimize the MCHS design for improved heat dissipation and structural strength. An orthogonal experiment was established with the average surface temperature of the heat source as the evaluation metric, and the optimal structure was determined through simulation. Finally, cooling uniformity, fluidity, and performance evaluation criterion (PEC) analyses were carried out on the optimal structure. It was determined that the optimal combination was the triangular cavity microchannel (MCTC), with a microchannel width of 0.5 mm, a microchannel distribution density of 60%, and the presence of surface undulation on the microchannels. The result shows that the optimal structure’s peak inter-layer stress is just 34.8% of its longitudinal tensile strength. Compared to the traditional parallel straight microchannel (MCPS), this structure boasts an 8.6 K decrease in the average surface temperature and a temperature variation along specific paths that is only 9.9% of that in traditional designs. Moreover, the optimal design cuts the velocity loss at the microchannel entrance from 75% to 59%. Thus, this research successfully develops an effective optimization strategy for MCHSs.

This research presents a surrogate model and computational fluid dynamic analysis-based multi-objective optimization approach for microchannel heat sinks. The Non-dominated Sorting Genetic Algorithm is suggested to obtain the optimal solution set, and the Kriging model is employed to lower the simulation's computational cost. The physical model consists of a coolant chamber, a mainstream chamber, and a solid board equipped with staggered Zigzag cooling channels. Five design variables are examined in relation to the geometric characteristics of the microchannel heat sinks: the length of inlet of the cooling channels, the width of the cooling channels, the length of the "zigzag", the height of the cooling channels, and the periodic spanwise width. The optimal geometry is established by choosing the averaged cooling effectiveness and coolant mass flow rate which enters the mainstream chamber through the microchannel heat sinks as separate objectives. From the Pareto front, the optimal microchannel heat sinks structures are obtained. Three optimized results are studied, including the maximum cooling effectiveness, minimum coolant mass flow rate, and a compromise between the both objectives; a reference case using the median is compared as well. Numerical assessments corresponding to the four cases are performed, and the flow and cooling performance are compared. Furthermore, an analysis is conducted on the mechanisms that impact the ideal geometric parameters for cooling performance. [ABSTRACT FROM AUTHOR]

The poor heat dissipation of LED light sources limits their applications in plant factories. This paper combines a microchannel heat sink (MHS) with circular concave cavities and ribs with the water irrigation system of an LED plant factory to develop water-cooled LEDs. By using this approach, four types of MHSs were designed: circular concave cavities (circular), circular concave cavities and single-sided ribs (circular-single), circular concave cavities and odd-symmetric ribs (circular-odd), and circular concave cavities and double symmetric ribs (circular-double). The influence of the arrangement of circular concave cavities and ribs on the flow and heat transfer performance was numerically investigated by ANSYS Fluent 21.0 R1. Corresponding MHSs with circular concave cavities and ribs were manufactured, and an experimental platform was built to experimentally verify the numerical results. The results showed that a circular concave cavity in the microchannel caused the fluid to form a secondary flow, which led to the continuous destruction and reconstruction of the flow and thermal boundary layer in the microchannel. This contributed to heat and mass transfer, while the presence of ribs altered the flow direction of the fluid and enhanced mass and heat transfer within the cavities. The pressure drop at the inlet and outlet of the MHS increased in the case of circular concave cavities and ribs as the inlet flow rate increased. Compared with MHSs with circular concave cavities, the ribs increased the pressure drop at the inlet and outlet. The inlet and outlet pressure drop of MHS with circular concave cavities and double-symmetric ribs was the highest, followed by MHS with circular concave cavities and odd-symmetric ribs, and the smallest was the MHS with circular concave cavities and single-sided ribs. As the inlet flow rate increased from 10 ml/min to 60 ml/min, the pressure drop between the inlet and outlet of the MHS with circular concave cavities increased from 22.54 Pa to 165.98 Pa (an increase of 143.44 Pa); the pressure drop of the MHS with circular concave cavities and single-sided ribs increased from 24.72 Pa to 187.31 Pa (an increase of 162.59 Pa); the pressure drop of the MHS with circular concave cavities and odd-symmetric ribs increased from 27.92 Pa to 212.12 Pa (an increase of 184.20 Pa) and that of the MHS with circular concave cavities and double symmetric ribs increased from 29.32 Pa to 221.21 Pa (an increase of 191.89 Pa). Under the same inlet flow rate and LED chip input power, the cooling water outlet temperature of MHS with circular concave cavities and double symmetric ribs was the highest, followed by MHS with circular concave cavities and odd-symmetric ribs, MHS with circular concave cavities and single-sided ribs, and MHS with circular concave cavities was the lowest. These results indicated that the heat transfer performance of MHS with circular concave cavities and double-symmetric ribs was the best, followed by MHS with circular concave cavities and odd-symmetric ribs, and MHS with circular concave cavities and single-sided ribs. The MHS with circular concave cavities had the worst heat transfer performance. The outlet temperature of the MHS with concave cavities and ribs reaches the highest value at the inlet flow rate of 30 ml/min. At this flow rate, the outlet temperature is 343.89 K for the MHS with circular concave cavities, 344.73 K for the MHS with circular concave cavities and single-sided ribs, 346.53 K for the MHS with circular concave cavities and odd-symmetric ribs; and 347.58 K for the MHS with circular concave cavities and double symmetric ribs. [ABSTRACT FROM AUTHOR]

A microchannel heat sink (MCHS) is a potential solution for chip and battery thermal management. The new microchannel structure is beneficial for further improving the thermal-hydraulic performance of MCHSs. Inspired by leaf veins, six new channel structures were designed, and the effects of the channel structures (three parallel structures named PAR I, II, and III and three pinnate structures named PIN I, II, and III), channel depths (0.4, 0.8, and 1.6 mm), and heat fluxes (20, 50, and 80 kW/m2) were investigated via numerical simulation. The cooling medium was water, and the heating area was 40 × 40 mm2. Both PAR II and PIN III exhibit superior overall performance, characterized by the highest Nusselt number and the lowest heating wall temperature. Moreover, PIN III demonstrates the lowest standard deviation in heating wall temperature, while PAR II exhibits the lowest friction factor. The greater the channel depth is, the larger the solid–liquid contact area is, leading to a reduced wall temperature at the interface under identical conditions of inlet Reynolds number and heating wall heat flux. Consequently, an increase in the Nusselt number corresponds to an increase in the friction factor. The maximum value and standard deviation of the heating wall temperature increase with increasing heat flux, while the Nusselt number and friction factor remain unaffected. The overheating near the two right angles of the outlet should be carefully considered for an MCHS with a single inlet–outlet configuration. [ABSTRACT FROM AUTHOR]

AbstractThis study employs a numerical simulation approach to investigate the heat transfer performance of elliptical microchannel heat sinks (MCHS) with varying aspect ratios (AR) of the elliptical cross-section. The convective heat transfer behavior of water and water-based nanofluids containing CuO nanoparticles at different volume fractions within the MCHSs is examined. The research results indicate that at Re = 600, as the AR of the elliptical cross-section increases from 1:1 to 1.75:1, the thermal performance of the MCHS improves by 5.33%. Furthermore, with an increase in the volume fraction of nanofluid from 0 to 0.75%, the convective heat transfer coefficient of the nanofluid increases by 11.87%. Compared to the circle MCHS using water as the coolant, the MCHS with an elliptical cross-section with an AR of 1.75:1 and a nanofluid volume fraction of 0.75% can reduce the maximum temperature of the chip by 9.78%. [ABSTRACT FROM AUTHOR]

Higher density heat flux is the major cause of damage to the electronic component; therefore, cooling such components are of the utmost importance to operate in a safe zone and to increase their life. For this purpose, Microchannel heat sinks (MHSs) are among the most practical methods for dissipating unwanted heat. In this regard, the novel lozenge-shaped pin-fins in the flow passage of the microchannel heat sink (MHS) have been designed and proposed to achieve higher cooling performance. Aspect ratios (λ = 0.30, 0.39, 0.52, 0.69, 1.00) of several lozenge-shaped pin-fins have been used into the design of MHS to investigate their impact on heat transmission and fluid flow characteristics. A three-dimensional model of MHS with a lozenge-shaped has been generated and simulated numerically in the following range of Reynolds numbers, starting from 100 to 900. Heat transmission and flow characteristics have been presented and discussed in detail. It has been found that introducing lozenge-shaped pin-fins in MHS has greatly improved cooling performance. The highest improvement in Nusselt number has been observed when aspect ratio (λ) of lozenge-shaped pin-fins was 1.00. The Nusselt number have been varied in the following ranges of 6.96–12.34, 6.97–12.72, 7.01–13.62, 7.09–14.43, and 7.12–15.26 at λ = 0.30, λ = 0.39, λ = 0.52, λ = 0.69, and λ = 1.0, respectively. In addition, a study of the thermohydraulic performance of the proposed lozenge-shaped pin-fins in the MHS found that this design is an effective means of lowering operating temperature. [ABSTRACT FROM AUTHOR]

AbstractTo enhance heat transfer coefficient, decrease pressure penalty, and improve wall temperature uniformity, a twisted blade-like fin with low-drag airfoil section is proposed in this study. The flow and heat transfer performances of microchannels with the fins are numerically investigated at Re = 50–700. Results show that the novel fins improve the heat transfer (Nu/Nu0) significantly with a small pressure penalty (f/f0), and thus show an excellent comprehensive thermal performance (TP). The ranges of Nu/Nu0, f/f0 and TP are 1.16–4.76, 1.51–2.36, and 1.01–3.58, respectively. The TP of TAMCHS reaches 3.58, exhibiting an increase of 46.7, 37.7, 22.6, and 16.6% compared to four models in previous study. The reduced pressure penalty is attributed to the streamlined configuration, and the improved heat transfer coefficient is attributed to the normalwise secondary flow stimulated by the twisted fins, which enhances heat transfer in the upper portion of the channel. Compared to a smooth microchannel heat sink (SMCHS), the major advantages lie in the significant reduction of sidewall temperatures and notable improvement in temperature uniformity on the top and bottom walls. The average and maximum wall temperature are reduced by 48.1 and 49.0 °C at most, respectively, and the greatest decline of wall temperature gradient is 55.0 °C. [ABSTRACT FROM AUTHOR]

Despite numerous studies on nanofluids in microchannel heat sinks (MCHSs), they are not yet commercialized due to long-term stability issues and high maintenance costs. Therefore, this study explores the impact of nanofluids and nanoparticle clustering on single-phase convective heat transfer inside microchannels under laminar conditions. Water and commercially available water-based nanosuspensions, including Al 2 O 3 -water (30–60 nm), TiO 2 -water (5–30 nm), and polystyrene-water (50 nm), are circulated through silicon MCHS having rectangular channels integrated into a closed flow loop. To assess the in situ and real-time nanoparticle clustering during heat transfer experiments, Light Extinction Spectroscopy (LES) is applied as a non-intrusive measurement technique on nanofluids without any fluid sampling. Our findings reveal the appearance of nanofluid discoloration with no measurable increase in heat transfer coefficient. This unexpected change is attributed to the interplay of abrasion, erosion, and corrosion phenomena, likely triggered by the clustering of nanoparticles within the silicon microchannels—a novel insight into the complex dynamics of nanofluid behavior (an increase in the De Brouckere mean diameter from 11 nm to 107.3 nm over a 2.5 h period for TiO 2 nanoparticles). The resulting material loss could not be mitigated by altering the nanoparticle material, which may impede heat transfer enhancement under tested conditions. [ABSTRACT FROM AUTHOR]

A novel framework has been employed in various contemporary studies, to enhance heat transfer in heat exchangers through microchannels. A microchannel heat exchanger (MCHE) is a miniature heat exchanger that can address issues such as rapid increases in heat flux in small spaces, storage space constraints, and the need for compact, lightweight heat exchangers. Four perspectives were used in the qualitative literature analysis: working fluid, flow disruption, microchannel material, and microchannel cross section. The findings revealed that various working fluids (air, water, refrigerants, oil, and nanofluids) are employed in microchannel heat exchangers (MCHE) and microchannel heat sinks (MCHS); however, almost all studies have shown that nanofluids as working fluids in microchannels exhibit better thermal behavior than other fluids. Enhanced thermal performance can be achieved by adding flow disrupters (wavy channels, ribs, dimples, and baffles). Based on several applications, various materials, including aluminum (Al), copper (Cu), silicon (Si), stainless steel, silver (Ag), and various other metals, are used for MCHE & MCHS construction. However, owing to the thermal property limitations and oxidation behavior of metallic materials researchers have used ceramic microchannels to avoid these problems. The outcomes of the present review suggest that microchannel-based applications have come a long way away, but there are still barriers to addressing the needs of heat transfer in modern industries, such as the prevalence of the use of conventional rectangular shapes, water-based working fluids, metals as construction materials, and numerical techniques. Based on a literature survey, the authors suggest that rectangular wavy microchannels made of ceramic material using Al2O3–water as a nanofluid have better hydrothermal behavior than any other microchannel. [ABSTRACT FROM AUTHOR]

The high-power laser diode (HPLD) has witnessed increasing application in space, as the aerospace industry is developing rapidly. To cope with the space environment, optimizing the heat-dissipation structure and improving the heat-dissipation ability via heat conduction have become key to researching the thermal reliability of the HPLD in space environments. Based on a theoretical analysis of the HPLD, a simulation model of the HPLD was constructed for numerical simulation, and it was found that the maximum temperature and thermal resistance of lasers were efficaciously decreased by changing the packaging position of laser bars. The packaging position of the bars and the cutting angle of the microchannel heat sink (MCHS) were determined based on the light-emitting angle of the light-emitting unit and the internal structure of the MCHS. The internal structure of the MCHS was optimized through a single-factor experiment, an orthogonal experiment, and the combination of neural networks and genetic algorithms (GAs), using three key structural parameters, namely the MCHS ridge width, W1, the channel width, W2, and the channel length, L1. After optimization, the performance of the MCHS was obviously improved. Finally, an analysis was carried out on the applicability of the optimized MCHS to bars with a higher power.

The present trend of miniaturization in various electronic devices has caused higher heat generation per unit area. Dissipation of highly concentrated heat from these devices is essentially required to ensure their safe and prolonged use. Therefore, consistent efforts are made to upgrade the cooling technology to meet the current requirements. The microchannel heat sink (MCHS) has gained much attention due to its inherent property of a higher surface area-to-volume ratio. The thermo-hydraulic performance of MCHS has been further improved by several methods including active and passive techniques. In this work, a comprehensive review of the literature is presented to discuss the prominent design modifications done in the MCHS to enhance the heat dissipation capacity using single-phase fluid flow. It was commonly observed that heat transfer enhancement usually occurs at the cost of pressure drop penalty and other flow complications; therefore, relevant parameters have been discussed to evaluate the design’s efficacy.

In modern technology, anticipating the optimal thermal performance in microchannel heat sinks (MCHSs) is a vital response to overheating challenges in high-performance electronic devices. The Response Surface Methodology (RSM) application presents an innovative way of modeling such equipment's behavior. In the current study, an MCHS with pin fins was chosen to examine the Nusselt number (Nu) and pressure drop (ΔP). Using two RSM models and multi-objective optimization, the study tried to discern the optimal values of the responses in the MCHS. The RSM models examined three key parameters: length, installation angle, and the spacing between pin fins. The interactive impacts of independent parameters and their consequent effect on the responses were also explored. The RSM models attained exceptional predictive accuracy, with the determination coefficient values of 0.9946 and 0.9986 for Nu and ΔP, respectively. The working fluid applied in the present work was water with an inlet temperature of 288 K and a Reynolds number of 300. Besides, the constant heat flux of 100 W/cm2 was exposed to the bottom wall of the MCHS. In pursuit of an optimal MCHS design that maximizes Nu while minimizing ΔP, the study employed the relative efficiency index (η) parameter. Considering heat transfer and ΔP in the pin-fin MCHS, the optimal design showed an impressive improvement of about 64.5 % compared to the fin-free heat sink. Moreover, the study provided Pareto optimal points for Nu, ΔP, and η, adding depth to understanding the complex trade-offs within the investigated MCHS.

The ever-increasing demand for electronic systems to enhance their performance and processing speed has exponentially increased their heat generation, especially those containing microstructures with reduced surface area. Tackling these complex thermal management challenges creates an urgent need to design and model compact efficient cooling systems. In this investigation, a unique design of a microchannel heat sink with sinusoidal and absolute sinusoidal wavy walls with/without nanofluid is proposed. Heat transfer enhancement and fluid flow characteristics are numerically investigated by developing a two-dimensional finite element model for Reynolds numbers 5, 100, and 500. The periodicity of the wavy section and the different volume fractions of silver nanoparticles ranging from 0 to 4% in water are further considered. The entropy generation is analyzed using the Bejan number. The findings revealed that while the entropy generation rises in the absolute sinusoidal channel, it has a better heat transfer performance by 10.3%, 15.8%, and 16.6% than a straight microchannel for the ascending Reynolds numbers. Interestingly, the channel's heat transfer and thermal efficiency decrease when an unnecessary number of sinusoidal periods are used. The thermal efficiency improves by 3.35% compared to the straight microchannel by employing only one absolute sinusoidal wavelength along the channel.

Recently, the advantages of microchannel and micro pin-fin heat sinks for cooling have become clear. This study delves into the effects of hybrid designs on electronic chip cooling by combining microchannel and pin-fin patterns. The research contrasts the performance of a straight microchannel heat sink (Case Ⅰ), circular pin-fin (Case Ⅱ), straight-circular pin-fin-straight (Case Ⅲ), and oblique grooved straight-circular pin-fin-oblique grooved straight (Case Ⅳ). Results show that Case Ⅳ's Nu number reaches 61 at Re = 1250, surpassing Case Ⅰ, Case Ⅱ, and Case Ⅲ by 517 %, 32 %, and 235 %, respectively. Case Ⅳ also has the highest pressure drop. The study calculates each Case's performance evaluation index (ƞ), highlighting the balance between enhanced Nu numbers and pressure drops. Case Ⅳ's ƞ is notably higher than Case Ⅱ and Case Ⅲ. To achieve a more uniform thermal distribution across the entire heat sink, the orientation of the oblique grooves is modified in Case Ⅳ, resulting in a new design labeled Case Ⅴ. While Cases Ⅳ and Ⅴ have similar Nusselt numbers, Case Ⅴ's design ensures consistent temperature distribution, reducing hotspot risks on the chip.

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Optimization algorithms have significantly evolved because of advancements in computational capacity. This increase aids in the availability of data to train various artificial intelligence models and can be used in optimizing solutions for electronic chip cooling. In the current study, such a microchannel heat sink (MCHS) is optimized using a Boron Nitride Nanotube (BNN)-based nanofluid as a coolant. Thermal resistance and pumping power are chosen as the objective functions, while geometric parameters such as the channel aspect and width ratio are used as the design variables. Multi-objective multiverse optimizer (MOMVO), an evolutionary algorithm, is used to optimize both objective functions, which are minimized simultaneously. The primary objective of this study is to study the applicability of such advanced multi-objective optimization algorithms, which have not previously been implemented for such a thermal design problem. Based on the study, it is found that the optimal results are obtained with a population size of only 50 and within 100 iterations. Using the MOMVO optimization, it is also observed that thermal resistance and pumping power do not vary significantly with respect to the channel aspect ratio, while pumping power varies linearly with the channel width ratio. An optimum thermal resistance of 0.0177 °C/W and pumping power of 10.65 W are obtained using the MOMVO algorithm. [ABSTRACT FROM AUTHOR]

ObjectiveTo meet the efficient thermal management needs of electronic devices such as ships and underwater vehicles, this study focuses on the constructal design of a tree-shaped microchannel disc heat sink with wavy walls. MethodA design prototype of the heat sink with wavy walls is first proposed. Based on constructal theory, the amplitude and wavelength of the wavy walls are designed under the constraints of fixed heat sink volume and fixed microchannel volume by maximizing the comprehensive performance evaluation criteria (PEC) while considering both heat transfer and flow pressure drop. ResultsThe results show that the wavy walls increase the heat transfer surface areas and generate vortices in their cavities, effectively reducing the maximum temperature. When the inlet Reynolds number is fixed at 700, 900 or 1100 respectively, the maximum temperature is reduced by 13.5 K by increasing the amplitude of the wavy walls, while the pressure drop increases significantly; and the maximum temperature is reduced by 4.7 K by reducing the wavelength of the wavy walls, while the pressure drop increases slightly. There are optimal amplitudes that raise the comprehensive performance evaluation criteria to extreme values for given larger wavelengths, while the comprehensive performance evaluation criteria increase monotonously as the amplitude increases for given smaller wavelengths. ConclusionWavy walls can significantly improve the thermal performance of tree-shaped microchannel disc heat sinks, and the use of constructal design can realize optimal geometric constructs with optimal comprehensive performance evaluation criteria.

Recently, hybrid nanofluids have been outlined to enhance the cooling performance of microchannel heat sinks (MCHSs) and increase the heat dissipation rate in electronic devices. However, comparative assessments of hybrid nanofluids (HNFs) and water as coolants for MCHSs in terms of their hydrothermal performance and irreversibility characteristics are scarce. The present study aims to numerically assess the hydrothermal performance and entropy generation characteristics of various hybrid nanofluids in an MCHS for cooling a central processing unit (CPU). COMSOL Multiphysics software is used to solve the governing equations of a three-dimensional conjugate heat transfer model using the finite element method. The reduced graphene oxide decorated with cobalt oxide nanocomposite (rGO–Co3O4) and Fe3O4-coated MWCNT (MWCNT–Fe3O4) HNFs with temperature-dependent thermophysical properties and wide range of concentrations (0% ≤ φ ≤ 0.2%) are considered. The simulations are performed under constant Reynolds number (300 ≤ Re ≤ 1500) and constant flow rate (5.42 cm3/s ≤ Q ≤ 27.12 cm3/s) conditions. The results show that increasing the values of φ at a fixed Re significantly enhances the heat transfer coefficient; reduces the CPU temperature, thermal resistance, and total entropy generation; and improves temperature uniformity. However, the pressure drop and pumping power increase significantly. No significant enhancement is achieved when the HNFs are used instead of water at a constant flow rate, and a noticeable pumping power is obtained under all studied conditions. In conclusion, MWCNT–Fe3O4 HNF exhibited better combined thermohydraulic performance than the rGO–Co3O4 HNF.

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

Efficient microchannel cooling is the key to the development of microelectronics. The key to solving this problem is the geometry of the microchannel heat sink and the thermophysical properties of the fluid. We combined the cantor fractal principle with the microchannel heat sink to design a new type of three-dimensional microchannel structure. Thermal resistance is treated as a single objective function, and the simulated annealing process is utilized to minimize it and achieve satisfying results. When the Reynolds number (Re) = 100, the aspect ratio of the microchannel entrance (B / h), the aspect ratio of the Cantor fractal baffle (a / b) and the ratio of the width of the entrance of the microchannel to the length of the mixing unit (B / λ) are optimized. The important factors that affect the thermal resistance of the microchannel are the size and spacing of the baffle. Then the pressure drop and heat transfer under different Res were analyzed. The study found that the structure of the groove and baffle based on the cantor fractal principle will cause chaotic flow and greatly enhance the heat transfer performance. Compared with the reference microchannel, the comprehensive heat transfer coefficient PEC is greater than 1, the thermal resistance is reduced by 19.82%. Advanced working fluids and channel structures can be used to improve the heat transfer performance of the microchannel heat sink. The Cantor fractal principle with microchannel heat sinks have been combined to design a new three-dimensional microchannel structure. Thermal resistance as a single objective function and minimize it using a simulated annealing process will achieve satisfactory results. [ABSTRACT FROM AUTHOR]

ObjectivesThis study seeks to improve the thermal management technology of electronic devices through constructal optimization design. MethodsFirst, the 3D flow and heat transfer numerical model of a hybrid microchannel heat sink is established, and the volume ratio and relative position of its single-sided internal fins are fixed. Constructal optimization is then performed, for which the height-to-width ratio h/w and spacing distribution of fins ε are taken as the design variables, and the minimization of the temperature gradient uniformity factor in the solid region of the heat sink is taken as the objective. The exhaustive method and genetic algorithm are subsequently performed. ResultsThe results show that both the exhaustive method and genetic algorithm can find the minimum value of the temperature gradient uniformity factor and corresponding optimal construct, and the temperature gradient uniformity is improved by up to 13.30% compared to that of the finless microchannel heat sink. The relative difference in the obtained minimum objective function value between the exhaustive method and ten genetic algorithm schemes is no more than 0.92%. ConclusionsThis study provides new optimization design results for the research and development of heat sinks for electronic devices.