Wavy Microchannel Research Articles

Numerical study on flow and heat transfer in a novel symmetric sinusoidal wavy microchannel heat sink with rectangular rib prisms

To enhance thermal and overall performances, a novel microchannel heat sink (SSW-RP) was devised by integrating symmetric sinusoidal wavy sidewalls with rectangular rib prisms within the channels. A numerical comparative study was conducted to explore heat transfer mechanism in channels by investigating the flow and heat transfer characteristics of SSW-RP in comparison with those of smooth straight microchannel (MC), smooth straight microchannel with rectangular rib prisms (MC-RP), and symmetric sinusoidal wavy microchannel (SSW). The results show that the addition of rib prisms makes the fluid flow into wave peaks, reducing and even eliminating vortices from wave peaks of the symmetric sinusoidal wavy microchannel, thus significantly improving heat transfer performance. The new design SSW-RP had the highest relative Nusselt number, which reaches 4.16 at Re = 800. Further, the hydrothermal performance sensitivity of SSW-RP to the relative width (α) and length (β) of rib prisms is studied, and the best overall performance factor of SSW-RP finally can be achieved up to 1.88 at α = 0.35, β = 0.4 and Re = 800.

Effects of anisotropic permeability on EMHD nanofluid flow and heat transfer in porous microchannel with wavy rough walls

This theoretical study thoroughly examines the complexities of fluid flow and heat transfer within microfluidic devices by employing anisotropic porous media with wavy walls. The effect of anisotropic permeability and electromagnetohydrodynamics (EMHD) on nanofluid transport is examined in a wavy microchannel under a constant pressure gradient. The nonlinear coupled governing equations for electric double-layer potential, velocity, temperature, and nanoparticle volume fraction are solved numerically using shooting techniques with the Runge–Kutta method. The numerical results are validated with the asymptotic analytical solutions. We explore the impact of parameters like the Hartmann number, Darcy number, and joule heating on nanofluidic flow. The interplay between anisotropic permeability ratio and angle significantly influences flow, temperature profiles, and nanoparticle volume fraction. Reduction in nanoparticle concentration is attributed to constrained entry into the porous medium due to elevated anisotropic permeability. Frictional heating, influenced by the Forchheimer inertial effect, enhances temperature and induces slug flow at low Darcy numbers. The Nusselt number peaks at low Darcy numbers with an anisotropic angle of φ=π/2, experiencing a minimum when φ=0. These findings deepen our understanding of the role of anisotropic permeability in shaping fluid flow and heat transfer in microfluidic systems influenced by EMHD effects.

Numerical study of combined phase change material and water cooling in hybrid wavy microchannels for HCPV cell

HCPV cells are known for their high efficiency in converting sunlight into electricity. However, this increased efficiency also generates higher levels of heat, posing a risk of cell damage. Therefore, the study proposes the combination of a phase change material (CPCM) and liquid flow in hybrid wavy microchannels to ensure stable temperature within the high-concentration photovoltaic (HCPV) cells. A three-dimensional numerical model has been developed to capture the thermal behavior of PCM integrated with water cooling in a microchannel heat sink. The comparison and analysis involved contrasting cases with phase change material (PCM) and cases without PCM. The PCM cases were studied at Reynolds number (Re) 100, while the cases without PCM were investigated at Reynolds numbers of 100 and 200. Three distinct types of PCM were employed, specifically OM 32, Rt 35, and PA - SA/EG. The various microchannel geometries under consideration included Raccoon, wavy, and hybrid wavy microchannels. The results showed that using both PCM and water cooling in a microchannel is preferable over using only water cooling. The outcomes reveal that employing PCM 3 (CPCM) in conjunction with the raccoon wavy microchannel design, there is an 11.61% reduction in the maximum pressure drop, along with a decrease of 6.58% in the maximum solid substrate temperature. Moreover, this configuration attains the highest electrical efficiency, reaching 39.32%.

Enhanced thermo-hydraulic performance with two-phase flow boiling in wavy microchannel heat sink – A numerical investigation

This article demonstrates that using a wavy microchannel instead of a smooth microchannel can enhance thermal and hydraulic performance in both single and two-phase flow. Various performance parameters such as Nusselt number (Nu), friction factor (f), performance factor (PF), and enhancement factor (EF) are estimated for different wavy microchannels with varying waviness and amplitudes. The two-phase heat transfer coefficient (HTC) varies significantly with heat flux, particularly due to nucleate boiling. The heat transfer improvement with a wavy microchannel is evident with the highest values of the Nusselt number ratio (Nutp/Nusp = 2.35), PFwavy = 1.4, and EF = 1.88 achieved at specific operating conditions (heat flux = 100 W/cm2, mass flux = 188 kg/m2s, amplitude = 0.1 mm, wavelength = 1 mm). However, as mass flux, heat flux, and amplitude increase and wavelength decrease, the Nusselt number ratio Nutp/Nusp, PF, and EF decline due to the pressure drop penalty outweighing the benefits of heat transfer enhancement. The article also explores different designs of wavy microchannels for mitigating hot spots, including one with a decreasing wavelength along the flow direction and another with a shorter wavelength in the middle. However, these designs are more suitable for single-phase flow.

AC Electrothermal Effect Promotes Enhanced Solute Mixing in a Wavy Microchannel.

For liquids used in biological applications, a smaller diffusion coefficient results in a longer mixing time. We discuss, in this endeavor, the promising potential of the AC electrothermal (ACET) effect toward modulating enhanced mixing of electrolytic liquids with higher convective strength in a novel wavy micromixer. To this end, we develop a modeling framework and numerically solve the pertinent transport equations in a three-dimensional (3D) configuration numerically. By benchmarking the developed modeling framework with the experimental results available in this paradigm, we aptly demonstrate the maximum temperature rise, flow topology, species concentration field, and mixing efficiency in the proposed configuration for a set of parameters pertinent to this analysis. We find that the maximum temperature increase in the wavy micromixer, owing to the electrothermal effect, is less than 10 K even for the higher strength of the applied voltage, implying nondegradation of biological substances within the liquid sample. We report that the formation of significant lateral flow closer to the electrodes leads to a highly three-dimensional ACET flow field, which has a significant impact on the mixing efficiency for the range of diffusive Peclet numbers considered. We also report that the wave amplitude of the mixer, when intervening with the diffusive Peclet number, strongly impacts the mixing efficiency. As witnessed in this endeavor, for the smaller diffusive Peclet number, the mixing efficiency increases with amplitude, while the effect becomes the opposite for the higher Peclet number. The results of this study seem to provide an adequate basis for the design of a novel micromixer intended for enhanced solute mixing in realistic microfluidic applications.

Thermal performance of microchannel heat sink integrated with porous medium, slip coefficient and phase change material and machine learning approach

In this study, the thermal performance (TP) of the microchannel heat sink (MCHS) under the influence of the slip coefficient on the microchannel wall, the use of porous medium (PM) and phase change material (PCM), and the changes in the geometrical parameters and the shape of the microchannel have been discussed. The flow and energy equations were solved using the finite volume method. The validation of the melting process, slip coefficient, and porous medium with the previous literature demonstrate the high accuracy of the numerical solution, with the difference between the results being <8 %. The results indicate that using a wavy microchannel can improve TP by approximately10.6 % and 5 % compared to smooth and converging microchannels. Additionally, using non-Newtonian fluids with a power characteristic of 0.53 leads to improved TP about 2.8 % by reducing shear stress compared to Newtonian fluids. Furthermore, the presence of slip on the microchannel wall influences the flow pattern, resulting in reduced convection resistance and improved TP about 3.2–3.8 %. The highest TP was observed at a slip coefficient of 0.00001. Incorporating PM in the microchannel (either in the center or around it) can enhance TP by approximately 8–15 % compared to the base state, with greater improvements observed when PM is placed around the microchannel. The type of PM material and the porosity coefficient significantly impact TP. Varying the cross-sectional shape of the microchannel (square, rhombus, and triangle) has a substantial effect on improving TP compared to a circular cross-section, with the highest TP (with a 71 % increase) observed in microchannels with a square cross-section. Lastly, the use of PCM and PM on the active surface leads to a significant TP improvement of over 80 % compared to the base state. Using the Group Method of Data Handling algorithm, thermal resistance was estimated with an R-square value of 0.94 to validate the available data.

Fluid flow and heat transfer behavior of a liquid based MEMS heat sink having wavy microchannels integrating circular pin-fins

MEMS heat sink having wavy microchannels integrating circular pin-fins for cooling of microelectronic chips is proposed and analyzed in this work; the pin-fins are placed at the valleys and peaks of the wavy structure. The pumping power and thermal resistance of the proposed MEMS heat sink is higher and lower than that of MEMS heat sink having straight microchannels. At Reynolds number of 250, the maximum temperature of the microelectronic chip, generating 106 W/m2, when using the proposed MEMS heat sink is only 0.77 of that when using MEMS heat sink having straight microchannels; this ratio lowers to 0.6 at Reynolds number of 1250. The thermal resistance of the proposed MEMS heat sink is only 0.72 and 0.43 of that of the MEMS heat sink having straight microchannels at Reynolds numbers of 250 and 1250, respectively. Regarding the pumping power of the proposed MEMS heat sink, it is higher than that of the MEMS heat sink having straight microchannels by 2 and 3.7 at the lowest and highest Reynolds numbers, respectively. This work also analyzes the contribution of geometric features on the behavior of the proposed MEMS heat sink in terms of maximum temperature of the microelectronic chip, thermal resistance, and pumping power as well as that of microchannel employed in the proposed MEMS heat sink in terms of Poiseuille and Nusselt numbers. Maximum temperature of the microelectronic chip and thermal resistance decrease along with increase in pumping power with increase in amplitude, diameter of pin-fins, and hydraulic diameter of microchannel as well as with decrease in wavelength. Poiseuille and Nusselt numbers increased with rise in amplitude, diameter of pin-fins, and hydraulic diameter as well as decrease in wavelength. In addition, experiments have been conducted on two designs of the proposed MEMS heat sink to generate data for purposes of validating the model. The experimental data are compared with data from simulations and the difference between the two are within the uncertainty of experimental data thereby validating the model.

Electrothermal transport of water conveying copper, silver and alumina nanoparticles through a vertical wavy microchannel

This study emphasizes the significance of optimizing heat transmission, energy conversion, and thermal management in electronic devices, renewable energy systems, and emerging technologies like thermoelectric devices and energy storage systems. The aim is to enhance heat transfer efficiency for improved performance and lifespan of electronic equipment. The research utilizes a mathematical flow analysis to study a water-based ternary nanofluid’s flow and thermal characteristics in a vertical microfluidic channel driven by peristalsis and electroosmosis. The ternary-hybrid nanofluid (THNF), comprising copper, silver, and alumina nanoparticles dissolved in water, is examined considering induced magnetic fields. The study delves into fluid flow, heat absorption, and mixed convection, using Debye–Hückel, lubrication, and long wavelength approximations. Results show that THNF exhibits superior heat transmission compared to pure water. Increasing solid volume fraction of nanoparticles decreases THNF’s temperature. Induced magnetic fields impact the system. This research could influence thermal pipe heat sinks and bioengineered medical devices design.

Analysis and optimization of thermo-hydraulic characteristics of phase change slurry in wavy MCHS with porous fins based on RSM and desirability methods

In this study, the hydromechanical and diathermanous characteristics of microencapsulated phase change material (MPCM) slurry in wavy microchannel heat sink (MCHS) with porous fins are investigated by using two–phase mixture and Dacry–Brinkman–Forchheimer models. Based on the finite volume method (FVM) and response surface methodology (RSM), 54 cases considering 6 structural parameters are carried out. The correlations of Nusselt number (Nu) and friction factor (f) in straight and wavy microchannels with phase change slurry and porous fin designs are creatively proposed and unified. The maximum deviations between the actual and predicted values of Nu and f are 13.24% and 14.21%, respectively. In addition, the effects of radiator's parameters on Nu and f are emphatically discussed and analyzed by using three-dimensional surface diagram. It reveals that within the range of parameters tested, wavy amplitude (A) has the most obvious effect on responses, while channel aspect ratio (α) has the least impact on them. Moreover, the interactive effects between the five structural parameters are significant and complex, as one factor influences the impact of another on responses. Finally, the optimal parameters are obtained by desirability method with the goal of maximum Nu and minimum f. The results indicate that the overall performance of optimized configuration improved by 48.6% over the initial design. Our results may provide helpful guidance for the optimization design of MCHS, as significant improvement in heat transfer coefficient is expected to save substantial operating costs.

Interplay of geometry and shape-engineered-nanoparticles for efficient thermal performance in forced convection-based electronic cooling

Efficient and lightweight heat sinks for microelectronic cooling are pivotal for developing energy-efficient next-generation devices with huge processing power and significant heat dissipation over small scales. Microchannel heat sinks offer a solution not only for cooling electronics but also in applications of energy harvesting, defense, and biomolecular dynamics. An accurate understanding of transport phenomena at these scales can guide us toward minimizing frictional losses and thermal entropy for efficient thermal management. In this study, we numerically investigate the hydrothermal characteristics of a wavy microchannel heat sink integrated with nanofluids containing nanoparticles of different shapes. Our primary objective is to enhance thermal performance by studying the effects of four distinct nanoparticle shapes: spheres, cylinders, platelets, and blades. The nanoparticle concentration is varied within the range of 0.02–0.08, while the Reynolds number is set within the laminar regime (200–800). By decoupling the different contributions to system entropy and exergy, we aim to gain insights into the underlying physics behind thermal performance enhancement using shape-based nanofluids. Our findings reveal a significant increase in convective heat transfer coefficient, up to 50.63%, as well as notable exergy savings of up to 65.56%.

Thermo-hydraulic performance of solid/porous compound wavy microchannel heat sink with various angle of slanted passage

Microchannel-based heat sink is used to transfer huge amount of heat from electronics devices since last four decades, which is one of the best heat exchanger so far. In this study, a solid porous compound wavy microchannel heat sink (MCHS) with different angles of slanted passage has been evaluated with the help of commercial ANSYS fluent software at Reynolds number of 50 to 300 and compared with sinusoidal channel heat sink (SCHS). Fluid flow through porous fins is solved by Darcy–Forchheimer flow models and the thermo-hydraulic performance of MCHS is solved using finite volume approach. The walls and fins are made of copper, and the operating fluid is pure water. The impacts on secondary flow slanted passage with different angles (e.g. 30D, 45D, 60D, 75D, and 90D) in compound wavy channels are scrutinized. It is observed that as the slanted passage angle decreases in the compound wavy channel, heat transfer performance is significantly enhanced as well as pressure drop penalty decreases when compared to the SCHS. This is due to the increased effective fluid mixing by the dean vortices through secondary flow slanted passage at the crest and trough as well as permeation effect on the porous zone. The highest performance factor of 102.19% is calculated for solid/porous compound wavy microchannel heat sink (CWMC) 30D slanted passage heat sink at Reynolds number of 150. Hence, CWMC heat sink with secondary flow slanted passage have an ability to improve the cooling rate of microelectronics components.

Numerical Investigation of Fluid Flow and Heat Transfer in High-Temperature Wavy Microchannels with Different Shaped Fins Cooled by Liquid Metal.

The microchannel heat sink has been recognized as an excellent solution in high-density heat flux devices for its high efficiency in heat removal with limited spaces; however, the most effective structure of microchannels for heat dissipation is still unknown. In this study, the fluid flow and heat transfer in high-temperature wavy microchannels with various shaped fins, including the bare wavy channel, and the wavy channel with circular, square, and diamond-shaped fins, are numerically investigated. The liquid metal-cooled characteristics of the proposed microchannels are compared with that of the smooth straight channel, with respect to the pressure drop, average Nusselt number, and overall performance factor. The results indicate that the wavy structure and fin shape have a significant effect on the heat sink performance. Heat transfer augmentation is observed in the wavy channels, especially coupled with different shaped fins; however, a large penalty of pressure drops is also found in these channels. The diamond-shaped fins yield the best heat transfer augmentation but the worst pumping performance, followed by the square-, and circular-shaped fins. When the Re number increases from 117 to 410, the Nu number increases by 61.7% for the diamond fins, while the ∆p increases as much as 7.5 times.

Enhancement of battery thermal management system using a novel structure of hybrid liquid cold plate

Battery thermal management system (BTMS) is a crucial component of electric vehicles (EVs) as it ensures optimal operating temperature of battery cells, which is critical for battery safety and performance. Among various cooling methods, liquid cooling is the most reliable owing to its high heat transfer coefficient and low power consumption. In this study, a liquid cold plate (LCP) suitable for different ambient conditions was developed, with optimized power consumption and without pre-cooling the coolant. We investigated six different microchannels, including straight, wavy walls, and metal foam-embedded microchannels, in three different ambient conditions (20 °C, 25 °C, and 35 °C) at various coolant mass flow rates (ranging from 2.5 to 17 kg/s). Our results showed that the wavy walls microchannel reduced the maximum temperature by 4–6 °C, depending on the wave amplitude. Additionally, using fully embedded metal foam microchannels resulted in a 14 °C decrease in the maximum temperature compared to that of straight microchannels, while the temperature difference of the battery module remained within an acceptable range. We also found that a thick layer of metal foam in the vicinity of the microchannel walls decreased the battery module temperature by up to 4 °C while reducing the pumping power, especially at low coolant flow rates. Deploying the wavy microchannel reduced the pumping power between 50 and 73%, while a thin layer of metal foam caused a 50% decrease in pumping power.

Dynamic patterns of electroosmosis peristaltic flow of a Bingham fluid model in a complex wavy microchannel

The purpose of this paper is to present a rigorous analysis of streamline patterns and their bifurcation to a viscoplastic Bingham fluid model that involves heat and mass transfer in an electroosmotic flow through a complex wavy microchannel. The Bingham fluid act as a solid medium in the core layer, which divides the channel into three distinct sections utilized to model the problem as a switched dynamical system between these zones. To track multiple steady states (stagnation points) and related trapping phenomena, we perform both analytical and numerical bifurcation analysis of each subsystem with respect to different physical effects such as electrical double layer thickness and Helmholtz-Smoluchowski velocity. The key feature of the technique presented here is its ability to reveal the peristaltic transport characteristics of the Bingham fluid model in the presence or absence of symmetric flow properties. The primary novelty here is the ability to regulate the location and stability of the equilibrium points in the domain of interest. This leads to the detection of global bifurcations that reflect important dynamic elements of the model. Our results highlighted a new category of complex behavior that controls transitions between qualitatively different transport mechanisms, as well as a class of non-classical trapping phenomena.

Optimization for dense location and geometrical parameter of wavy microchannel to improve temperature distribution

In this article, a new locally denser sinusoidal wavy microchannel is proposed to improve the uniformity of temperature distribution. The influence of dense location and geometrical parameters, that is, wavelength (λ 3 = 600–1600 μm) and amplitude (A 3 = 40–200 μm), waviness factor γ (0.04–0.2) are studied by numerical simulation. Results show, compared with rectangular microchannels, dense wavy microchannels can effectively enhance heat transfer with a larger pressure drop penalty of 53.5–152.6%, but only 29.6–79.9% of locally denser wavy microchannels. Besides, it’s found that dense location influences severe heat transfer performance, but less for pressure drops. Heat transfer performance of downstream dense wavy microchannel is best, and the maximum temperature is reduced by 23 K under Re = 348. But the upstream dense type increases the maximum temperature difference than wave microchannel. Under the same pumping power, the thermal resistance of downstream dense wavy microchannel is reduced by 46% and 20% than straight microchannel and wavy microchannels. Decreasing wavelength and increasing wave amplitude could enhance heat transfer, and the effects become weaker. But the pressure drop is significantly increased. The best overall thermal performance is found for downstream dense wavy microchannel with γ = 0.12 of A 3 = 120 μm and λ 3 = 1000 μm, in which thermal resistance is reduced 48.6% under same pumping power.

Examining the impact of inlet header configurations on wavy microchannel heat sinks

Examining the impact of inlet header configurations on wavy microchannel heat sinks

Unsteady flow of hybrid fluid via peristaltic pumping in wavy micro-channel under electric and magnetic field effects: An application of Hall device and slip boundary

Aim of study In the current analysis, the blood is used as a viscoelastic fluid and manipulated with an electromagnetic field because of its magnetic features. Furthermore, blood is considered as a non-Newtonian fluid that is productive in nano- and micro-scales transport. To study the performance of hybrid fluids, a selection of nanofluids is examined with a Jeffrey fluid (blood) which is doped with [Formula: see text] and [Formula: see text] nanoparticles. Mathematical formulation The long wavelength assumption, lubrication theory and Debye–Huckel linearization are employed. Analytical solutions of flow equations are implemented in Mathematica by using integration technique. The impacts of considered parameters on the flow are computed. Combined influence of Hall device, momentum, and thermal slips is observed on various flow features. Outcomes Magnitude of the velocity goes on decreasing by increasing magnetic and viscoelastic parameters. The wavy behavior is predicted in the graphs of pressure gradient due to the complex nature of peristaltic walls. Enhancing the viscoelastic effects and concentration of nanoparticles results in reduction of magnitude of the pressure gradient. Heat transfer of hybrid fluid is larger in steady state flow as compared to the unsteady state. The heat source/sink parameter has remarkable impacts on enhancement of heat transfer phenomena of viscoelastic hybrid fluid. Applications The present investigation is relevant to electromagnetic hybrid liquid micropump manufactures and emerging nano-physiological technologies.

Condensation flow visualization, heat transfer, and pressure drop in printed circuit heat exchangers with straight and wavy microchannels

This study experimentally investigated the condensation flow visualization, heat transfer, and pressure drop characteristics of R1234ze(E) and R32 in printed circuit heat exchangers (PCHEs) with straight and wavy microchannel geometries. The effects of the microchannel geometries and refrigerants on the condensation flow, heat transfer, and pressure drop characteristics were investigated. Three flow patterns, namely, the nondisturbance annular, annular, and plug flows, were observed in the straight microchannels, whereas only annular and plug flows were observed in the wavy microchannel. A thin liquid film was observed to form on the inner arc of the wavy microchannel in the plug flow region. The overall heat transfer coefficient and pressure drop of the PCHE with the wavy microchannel were, respectively, 11% and 18% higher than those of the PCHE. The overall heat transfer coefficient and pressure drop of R1234ze(E) were 29% lower and 42% higher, respectively, than those of R32.

Liquid cooling of microelectronic chips using MEMS heat sink: Thermohydraulic characteristics of wavy microchannels with pin-fins

Liquid cooling of microelectronic chips using MEMS heat sink: Thermohydraulic characteristics of wavy microchannels with pin-fins

Optimal design of wavy microchannel heat sinks based on prediction and multi-objective optimization algorithm

In this paper, the multi-objective optimization of wavy microchannel heat sinks is performed by combining numerical calculation, prediction algorithm and genetic algorithm. In numerical calculation, the fluid-solid conjugate heat transfer of heat sinks with different parameters are simulated in Fluent. On this basis, the variable parameters and objective parameters are used to complete the training of neural network model, which aims to achieve accurate prediction of objective parameters. Finally, the multi-objective genetic algorithm is applied to find the Pareto front according to different requirements on the foundation of the prediction model. Results show that the coefficient of determination of the neural network models are all greater than 0.85, which proves that the prediction model has a high accuracy. The Pareto fronts are obtained by non-dominated sorting genetic algorithm (NSGA-II) with different objective parameters and they reveal that the channel with the optimal performance corresponds to a larger channel width or Reynolds number. In addition, it is also found the dimensionless temperature difference is correlated with Nusselt number.