Wavy Channel Research Articles

Numerical investigation of hydrothermal performance and entropy production rates of rGO-CO3O4/H2O hybrid nanofluid in wavy channels using discrete phase model

This work investigates numerically the turbulent hydrothermal performance and the entropy production rate (EPR) of rGO-CO3O4/H2O hybrid nanofluid “reduced-graphene oxide/cobalt oxide (rGO-CO3O4) nanoparticle with water as a base fluid” flow in two-dimensional straight, serpentine, and furrowed wavy channels. Both discrete phase and k−ω models were used in ANSYS Fluent package to simulate the turbulent hybrid nanofluid flow based on the finite volume method. The effect of Reynolds number (5.0×103≤Re≤3.0×104), nanoparticle volume ratio (0≤VR≤0.2%), amplitude (0.2≤A*≤0.6), and wavelength (0.7≤λ*≤1.4) on the hydrothermal and EPR were examined. The results revealed that the average Nusselt number (Nu), pressure drop (dP), and EPR due to the viscous dissipation in terms of viscous entropy production rate (VEPR) in wavy channels are higher than that of the straight channel and decrease with increasing λ*. However, the opposite is the case for EPR due to temperature gradient in terms of thermal entropy production rate (TEPR). The normalized (referencing straight channel) dP,Nu, TEPR, and VEPR in the serpentine wavy channel at Re=1.5×104, λ*=0.7 and A* = 0.2 are 16.83, 1.59, 0.76, and 5.93, respectively. The corresponding values at Re=1.5×104, λ*=1.4 and A* = 0.2 are 7.70, 1.34, 0.85, and 3.67, respectively. Furthermore, Nu,dP, and VEPR increase with increasing A*. However, the opposite is the case for TEPR. Finally, the thermal effectiveness number due to geometry modification (Igeo) obtained from combined first and second thermodynamic laws shows that the wavy channels are more effective compared with the straight channel.

Examining the effect of backward/forward-facing wavy channels on the thermohydraulic performance of a printed circuit heat exchanger under the laminar flow regime

The printed circuit heat exchanger (PCHE) has been used in many important engineering applications because of its advantages, including its small size and high efficiency. This study aims to enhance the thermohydraulic characteristics of the PCHE by using new channels characterised by a three-dimensional flow path. These proposed backward/forward-facing wavy channels (BFFWCs) are a combination of a wave path in the horizontal plane and a U-shape path in the vertical plane. Under laminar water flow on both sides of the PCHE, a numerical study was conducted to assess the thermohydraulic characteristics of the proposed PCHEs with various wave amplitudes for channels and angles of attack for six models of BFFWCs on the basis of the conventional PCHE. The evaluation parameters that were adopted are the Nusselt number, friction factor, thermohydraulic performance criterion, and PCHE's effectiveness. Two models of the PCHE were manufactured and tested—one for the straight channels and the other for the proposed channels—to verify the accuracy of the numerical simulation results by comparing them with the experimental outcomes. Results indicated that the three-dimensional flow path has a positive influence on enhancing the heat transfer rate of the exchanger, with a slight increase in the pressure loss. The Nusselt number and friction factor increase with increasing wave amplitude and angle of attack. Compared with conventional PCHE, the maximum improvement in the Nusselt number is as much as 71 % and 78 % for model 3 (amplitude = 0.8 and angle of attack = 30°) and model 6 (amplitude = 0.8 and angle of attack = 60°). The thermohydraulic performance of model 3 was better than that of model 6. The maximum obtained thermohydraulic performance criterion reaches about 1.43 and 1.40 for models 3 and 6, respectively.

Investigation of dissipative heat transfer and peristaltic pumping on MHD Casson fluid flow in an inclined channel filled with porous medium

A theoretical investigation is performed for free convective peristaltic pumping of a Casson fluid through an inclined porous wavy channel. The flow is subjected to uniform magnetic field in the transverse direction. In addition, the energy equation contains porous and viscous dissipation effects. The governing flow problem is modeled for Casson fluid with the help of conservation laws of mass, momentum, and energy under the long wavelength assumption. Using a regular perturbation method, we obtained the analytical expressions for the axial velocity, temperature, pressure rise per one wavelength, and heat transfer rate. The consequences of various effects on the flow quantities are demonstrated in the form of graphical representations and discussed in detail. The findings reveal that the rise in the thermal Grashof number and permeability parameter leads to an increment in the velocity and thermal fields. The heat transfer rate strengthened when the Casson parameter and magnetic parameter were increased. The pressure rise exhibits an enhancing trend for the Brinkmann number and permeability parameter. Further, we observed a decreasing behavior on streamlines for increasing magnetic field strength. Moreover, the obtained findings are applicable to a variety of fields in the bioengineering and medical sciences, such as targeted drug delivery, heart-lung machines, MRI, cancer therapy, power conversion devices, and micromanufacturing processes.

Computation insight of modified thermal distribution of hybrid nanofluids in complex wavy channel: A comparative thermal approach for different nanofluid models

Computation insight of modified thermal distribution of hybrid nanofluids in complex wavy channel: A comparative thermal approach for different nanofluid models

Experimental and numerical study on heat transfer performance of wavy channel heat sink with varying channel heights

Today, electronic device cooling is a significant challenge that has been addressed by utilizing heat sinks with various designs. The numerical and experimental investigation of changes in the wavy channel heat sink height is carried out to improve the performance. As a novelty, the heat sink's height remains constant to assess how open space above the channels affects the performance. The work aims to assess the impact of various heat fluxes and flow rates on temperature, Nu number, flow, and velocity; meanwhile conducting a non-dimensional analysis. At the flowrate of 6.94cm3/s, once the channel's height was reduced to 10 mm, the highest temperature decreased by 7.84%, while by the decrement of height to 7 and 4 mm, it witnessed 14.14% and 23.81% rises, respectively. The local Nusselt number for 10 mm height and 19.56cm3/s flow ranges between 127.47 and 106.53 in 5.17 W/cm2 heat flux. The flow with higher dimensionless velocity is dispersed throughout the open area above the heat sink, once the 12.7 mm height is reduced to 10 mm. The performance evaluation criterion of the system is determined by considering the ratio between Nu number and friction factor, which is obtained between 1.08 and 1.22 for 10 mm channel height. Thus, the 10 mm wavy channel height can be suggested for cooling electrical equipment.

Performance characteristics on up-scaling vacuum membrane distillation modules

Large-scale CFD studies are currently lacking in membrane distillation due to high computational overhead. This study utilizes a validated CFD model for vacuum membrane distillation and reduces the order of the model to enable prototype scale simulations. Different module designs were considered: a baseline flat sheet membrane module, a spacer-filled channel, a wavy channel, and a wavy channel with embedded stiffeners. Different lengths (330 mm, 660 mm, and 990 mm) were studied to simulate lab to prototype upscaling. Large Eddy Simulations were run in the laminar (Re 900) and turbulent (Re 3600) flow regimes. For Re 900, cases with geometric alterations (wavy membrane, spacer-filled channel) locally outperformed the baseline case within the first 330 mm before axial temperature polarization equilibrated the performance between the baseline and altered channels. The improvement in local performance was seen over the whole 990 mm length at Re 3600, culminating in a 35–40 % flux improvement versus the baseline at Re 3600 versus a 0–35 % difference at Re 900. Axial temperature polarization was mitigated using heat injection, showing a 5 % flux drop as length tripled compared to a 20–27 % decline. Higher operational Reynolds numbers should be considered cautiously for increasing pressure drop and violating the liquid entry pressure limit for wetting.

Effect of non-uniform heating on conjugate heat transfer and entropy generation characteristics within a partially filled porous corrugated channel

The persistence of the present numerical investigation is to evaluate the thermal and total entropy generation characteristics of flow within a partially filled porous wavy channel with finite wall thickness subjected to non-uniform wall heat flux. The average Nusselt number and the total entropy generation increase with the permeability value of the porous medium (Da) irrespective of asymmetric wall heat flux amplitude and wavelength as well as with the variation in thickness ratio and thermal conductivity value of the solid substrate. However, the total irreversibility decreases for a high Darcy number value when the phase angle between the applied heat fluxes is varied. Moreover, the average Nusselt number decreases up to a critical value of phase angle followed by a gradual increment for Da = 10−5 and 10−3, respectively. On the contrary, the reverse trend can be seen for Da = 10−1. The optimal choice of nonuniform heat flux amplitude, wavelength, and phase angle for a high heat transfer rate with minimum irreversibility generation is found to be 10 W/cm2, 5 mm, and 180°, respectively for a thickness ratio of 0.5 and thermal conductivity value of 646.07 W/m·K independent of Darcy number.

Heat transfer enhancement by electrohydrodynamics in wavy channels

The present study numerically investigated the heat transfer process occurred in a wavy channel enhanced by electrohydrodynamics (EHD). The mechanisms of the EHD-enhanced heat transfer in wavy channels differ from those in a straight channel. An advantageous position for single electrode is proposed to be above the peak of wave in a continuous wavy channel. Strategies for aligning multielectrodes in the EHD-enhanced continuous or discontinuous wavy channels are proposed based on interpretation on the simulation outcomes for single electrode. The ratio of horizontal section length to wave length (l/λ) significantly affects the heat transfer enhancement, unlike the case in continuous wavy channel (l/λ = 0). The optimal electrode arrangement for continuous wavy channels is inappropriate for discontinuous wavy channels, the electrodes should be placed above the junction of wave and horizontal section. The design criteria are proposed for enhanced heat transfer performance in discontinuous wavy channels with multiple electrodes: the electrode spacing should be as large as possible to minimize the barrier effect when the ratio l/λ < 0.15; however it is beneficial to reduce the electrode spacing when the ratio l/λ > 0.15.

Radiative heat transfer on the peristaltic flow of an electrically conducting nanofluid through wavy walls of a tapered channel

Present analysis deals with the characteristics of radiative heat on the peristaltic flow of nanofluid through wavy walls of a tapered channel. Peristaltic flows within the pumping process arise in the region having lower to higher pressure region. Assumption of velocity slip along with the convective boundary condition energizes the thermal system as well as the flow phenomena. However, the combined effect of Brownian motion and thermophorsis due to the cross-diffusion effect affects the flow properties. One of the significant applications of the flow is that the blood pumping in the human body. It acts as a vehicle through the liquid that past through the wavy channels walls contacting liquids expands in its length due to the dynamical rush. However, solution of the transformed governing flow phenomena is obtained by employing approximate analytical technique known as Variation Parameter Method (VPM). The characteristics of the parameters involved in the system are presented via graphs. Present outcome warrants that, the significance of magnetic strength and flow through the permeable medium may favours to enhance the pumping procedure as the pressure gradient lower down in the non-Darcy medium found to be one of the important observations. Further, significant enhancement in the fluid temperature and concentration profile is exhibited due to the consideration of the convective conditions i.e. the augmentation in the thermal and solutalBiot numbers respectively.

Forced convection of non-Newtonian nanofluid in a sinusoidal wavy channel with response surface analysis and sensitivity test

A numerical study on the forced convection of water-Cu power-law non-Newtonian nanofluid in a wavy channel has been done. The temperature of the horizontal walls is larger than that of the input fluid. The governing equations are solved by the SIMPLE algorithm-based finite volume method. The effects of pertinent parameters power-law index, Reynolds number, and nanoparticle volume fraction have been varied. The obtained results are presented in terms of the local and average Nusselt number (Nu) for the rate of heat transfer, streamlines, and isotherms. The correlation for the average Nusselt number is obtained using the Response Surface Analysis (RSM) for the flow parameters. The relationship between input parameters and output was observed by plotting the response surface and contours that were obtained by RSM. The sensitivity of the output response to all the input parameters is also observed. This study concludes that heat transfer enhanced in wavy channels by adding nanoparticles and increasing the Reynolds number. It is also observed that shear-thinning non-Newtonian nanofluids can be more effective in heat transfer enhancement than shear-thickening fluids.

Particle focusing in a wavy channel

It is known that inertial lift forces can lead to particle focusing in channel flows; yet oscillatory straining effects have also been suggested as a mechanism for particle focusing in wavy channels. To explore the synergy between these two mechanisms, we analytically and experimentally investigate the focusing behaviour of rigid neutrally buoyant particles in a wavy channel. We decompose the particle-free channel flow into a primary Poiseuille flow and secondary eddies induced by the waviness. We calculate the perturbation of the particle on the particle-free flow and the resulting lateral lift force exerted on the particle using the method of matched asymptotic expansions. This yields a zeroth-order lift force arising from the Poiseuille flow and a first-order lift force due to the waviness of the channel. We further incorporate the inertial lift force into the Maxey–Riley equation and simulate particle trajectories in wavy channels. The interactions between the zeroth-order lift force and the particle-free flow largely determine the focusing locations. Experiments in wavy channels with varying amplitudes at channel Reynolds numbers ranging from 5 to 250 are consistent with the predictions of the focusing locations, which are mainly governed by the channel Reynolds number as well as the competition between the inertial lift and the oscillatory straining effects.

Thermohydraulic performance of ammonia, isopropanol, water and nanofluids as cooling fluid for lithium-ion 1C and 3C rating batteries

Cooling Lithium-ion batteries of different C ratings receive excellent attention amongst researchers in thermal management. The present study proposes to investigate the thermohydraulic performance of a wavy channel and compare the finding with the conventional straight channel. The full Navier Stokes equations and the energy equation were solved numerically using the finite element technique. Water is the cooling liquid used in the simulation. The flow is laminar and steady state. It is found that the average Nusselt number is higher as the waviness of the channel wall increases. The average Nusselt number for the wavy channel case was increased by up to 31% compared to the straight channel configuration. Also, the performance evaluation criterion increases by 23% compared to straight channel configuration. Thus, allowing the fluid to absorb more heat. However, at the expense of the pressure drop, the performance evaluation criterion is higher for the wavy wall channel mode than the straight channel wall. Amongst all fluids studied in this paper, including water, ammonia, isopropanol, Ammonia binary mixture and TiO2 nanofluid at different concentrations, ammonia is the most suitable liquid for cooling.

A New Integrated GDL with Wavy Channel and Tunneled Rib for High Power Density PEMFC at Low Back Pressure and Wide Humidity.

Proton exchange membrane fuel cells (PEMFCs) have garnered significant attention due to their high efficiency and low emissions. However, PEMFC always suffers mass transfer and water management in performance improvement. Herein, an integrated gas diffusion layer (GDL) with wavy channel and micro-tunneled rib is designed and prepared to achieve faster and gentler mass transfer and excellent water management capability by laser engraving. Outstandingly, the new integrated GDL can use the back pressure of air as low as 0 and 50kPa to respectively achieve 80% and 90% of fuel cell performance realized under pure oxygen. Such high performance is mainly due to the turbulent flow caused by wavy channel and express removing pathway of liquid water provided by micro-tunneled rib. Moreover, the new integrated GDL also shows wide humidity tolerance from 40% to 100% and a very high specific volume power density of 16,300W L-1 due to the thin thickness of new integrated GDL. This new integrated GDL is expected to be widely used in PEMFC and other energy conversion devices.

Entropy generation of Al2O3/water nanofluid in corrugated channels

The flow of nanofluids in a corrugated channel has been shown to have a significant impact on heat transfer performance, and has therefore become an important area of research. The ob- jective of this paper is to understand the thermal behavior of Al2O3/water nanofluid in a sinu-soidal and square channel and to identify ways to optimize heat transfer performance in such configurations. For this purpose, a numerical simulation was conducted using ANSYS-Fluent software 16.0 on entropy generation and thermo-hydraulic performance of a wavy channel with the two corrugation profiles (sinusoidal and square). The analyses were carried out under laminar forced convection flow conditions with constant heat flux boundary conditions on the walls. The influence of various parameters, such as particle concentration (0–5%), particle di-ameter (10nm , 40nm and 60nm), and Reynolds number (200 &lt; Re &lt; 800) on the heat transfer, thermal, and frictional entropy generation, and Bejan number was analyzed. Moreover, the distribution of streamlines and static temperature contours has been presented and discussed, and a correlation equation for the average Nusselt number based on the numerical results is presented. One of the most significant results obtained is that the inclusion of nanoparticles (5% volume fraction) in the base fluid yielded remarkable results, including up to 41.92% and 7.03% increase in average Nusselt number for sinusoidal and square channels, respectively. The sinusoidal channel exhibited the highest thermo-hydraulic performance at Re= 800 and φ= 5%, approximately THP= 1.6. In addition, the increase of nanoparticle concentration from 0% to 5% at Re= 800 and dnp= 10nm, diminishes the total entropy generation by 28.39 % and 22.12 % for sinusoidal and square channels, respectively, but when the nanoparticle diameter decreases from 60nm to 10nm at ϕ= 5% and Re= 800, the total entropy generation in the sinusoidal channel decreases by 34.85%, whereas in the square channel, it decreases by 20.05%. Therefore, rather than using a square channel, it is preferable and beneficial to use small values of nanoparticle diameter and large values for each of ϕ and Re in the sinusoidal wavy channel. Overall, the study of nanofluid flow in a wavy channel can provide valuable insights into the behavior of nanofluids and their potential applications in a variety of fields, including manufacturing, energy produc-tion, mining, agriculture, and environmental engineering.

Thermal performance of copper-distilled water nanofluid in a wavy channel

This paper carried out an experimental study to synthesize and characterize copper water based nanofluid. To do so nanoparticles were fabricated by using one-step pulsed Nd: YAG laser ablation method under ambient conditions. Copper substrate was ablated for the duration of 25 min to ensure enough volume fraction of nanoparticles inside the host fluid. Energy dispersive spectroscopy (EDS) and scanning electron microscopy were done. The morphology of the nanoparticles seems to be homogeneous. The size distribution analysis resulted in the average size of 100 nm. Also, UV–Vis spectroscopy analysis was done for four months to investigate the stability of the synthesized nanofluid. It is observed that the nanofluid is not enough stable for more than one month. On the other hand, numerical simulations were done employing Ansys Fluent software to study thermal behavior of copper nanofluid in a corrugated channel. It is observed that higher volume fraction of nanoparticles leads to the higher heat transfer rate. Also, in this study, hydrophobic wavy wall with a constant temperature was considered as a hydrodynamical approach to enhance the heat transfer rate. It is concluded that hydrophobicity contributes to the increment of Nusselt number up to 45 percent in laminar flow. Meanwhile, Discrete phase method, which attribute to the Eulerian Lagrangian approach, was simulated. Outcomes indicated that DPM method can be trusted by less than 2% error in laminar flow.

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.

Flow and heat transfer in a meandering channel

Fluid flows occur due to internal or external forces such as wind, gravity, pressure gradients, side-wall motion, MHD, and free convection. This study examines how meanders impact heat transfer by studying the behavior of viscous fluid flow with streamwise vortices in a sinusoidal wavy meandering channel of non-uniform radius. The study simplifies the motion and energy equations governing the fluid flow using novel transformations and a regular perturbation method. By plotting graphs for different parameter values, such as Pr, Re, and Ec, it reveals that decreasing the wavelength leads to flow separation near the channel surface. However, the stream moves forward with a sudden meander disturbance, causing the flow to become rectilinear and independent of vertex-generating centrifugal forces. The study identifies a stream function using standard and established relations. The fluid flow patterns and temperature distribution behavior are shown in various plots, highlighting the significant impact of meanders on fluid flow.

Numerical study on flow distribution of supercritical CO2 in multiple channels of printed circuit heat exchanger

The printed circuit heat exchanger (PCHE) is a promising candidate in the application of the supercritical CO2 Brayton cycle. The flow maldistribution of PCHE is a practical issue due to the multi-channels in the core region, which may affect the performance of PCHE in the operation. Therefore, in this paper, the flow distribution and thermohydraulic characteristics of PCHE with three different channel configurations including the straight channel, wavy channel, and airfoil channel are investigated. The flow non-uniformity with two types of headers (free manifold and straight rib manifold) is compared among the three configurations under different mass flow rates. Based on the results, it is found that the core region of PCHE with larger flow resistance shows better flow uniformity and heat transfer performance. And the header structure is of great significance to the flow distribution based on the analysis of flow vector contours. Therefore, a modified manifold, with bent fins and airfoil fins, is proposed to improve the flow maldistribution of PCHE. Compared to the free manifold and straight rib manifold, the flow non-uniformity of the modified manifold is reduced by 39.4% and 61.8%, respectively; and the overall performance is averagely increased by 5% and 8.5%, respectively. Hence, it is recommended that the designers adopt the modified manifold for the performance improvement of integrated PCHE.

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.

THE IMPACT OF FLOW CONFIGURATION ON OVERALL HEAT TRANSFER COEFFICIENT OF MINI CHANNEL HEAT SINK

The primary objective of this study is to investigate how the formation of flow impacts the thermal the heat sink's performance and temperature distribution at its base. To achieve this, two distinct channel models, namely the model with a straight channel A and the model with a wavy channel B, are employed to manipulate the flow configuration being analyzed. Additionally, the inlet as well as exit positions were altered by placing the entry at the center of the heat sink. The numerical results are obtained through the utilization of a 3D analysis, specifically ANSYS Fluent. The present research compares numerical results with experimental data obtained from a literature search. Findings of this comparison indicate that the numerical and experimental outcomes are in good alignment. Additionally, the results show that the flow arrangement significantly affects temperature and pressure drop distribution. Despite these facts that the configuration involving a pair of inlets and outlets enhances temperature uniformity and reduces pressure drop. According to the study, the newly proposed models exhibit superior Overall Performance Factor (OPF) compared to the traditional model. Model [A] demonstrates an average OPF of 1.9, whereas model [B] achieves an average OPF of 1.26. Furthermore, the decreased pressure drop provides a superiority of 34% to model [A] over model [B].