A Novel Micromixer with Fractal Obstacles Designed Based on Generalized Murray’s Law

2020 ◽  
Vol 18 (3) ◽  
Author(s):  
Jiajia Xu ◽  
Xueye Chen
Keyword(s):  
Reynolds Number ◽  
Flow Behavior ◽  
Mixing Efficiency ◽  
Mixing Performance ◽  
Murray's Law ◽  
Branch Angle ◽  
Murray’S Law

AbstractIn this paper, we designed tree-like branch structures with two levels according to generalized Murray’s law, and set them as obstacles in microchannels. The influence of the mixing performance of the micromixer was studied by changing the geometry sizes of obstacles, the branch angles and the distances between obstacles. The mixing performance of micromixer was analyzed from three aspects, including mixing efficiency, flow behavior, and pressure drop.We designed three different obstacles A, B, and C, the micromixer with obstacle C has the highest mixing efficiency. For the distances of obstacles, the micromixer with smaller distance has the higher mixing efficiency. The micromixer with branch angle of 75° has the highest mixing efficiency in the range of Reynolds number (Re) 0.1 to 150.

Numerical study of a fractal-like tree node micromixer based on Murray’s law

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Hangda Xie ◽  
Xueye Chen
Keyword(s):  
Pressure Drop ◽  
Pressure Range ◽  
Numerical Study ◽  
Mixing Efficiency ◽  
Mixing Effect ◽  
Murray's Law ◽  
Tree Node ◽  
Branch Angle ◽  
Murray’S Law ◽  
The Way

Abstract This article focuses on the influence of fractal-like tree node (FTN) on the mixing efficiency and pressure drop of the micromixer. The mixing efficiency of FTN micromixers with different branch angle δ = 30°, 60° and 90° are compared at six kinds of Reynolds (Res). We can get that the micromixer with δ = 90° has higher mixing efficiency at any Re. The mixing results of the center FTN and the stagger FTN micromixer show that the center FTN has better mixing effect. The angle of FTN and the number of FTN are the key to improve the mixing efficiency. They are also the key to change the pressure drop in the microchannel. The FTN can slow down the pressure drop and maintain the stable pressure drop between two adjacent FTNs. The way to obtain a more stable pressure range is to increase the distance between two adjacent FTN. This provides a reliable reference for maintaining a stable pressure in the microchannel.

A Microfluidic Mixer Fabricated From Compliant Thermoplastic Films

2008 ◽  
Vol 2 (1) ◽  
Author(s):  
N. Paya ◽  
T. Dankovic ◽  
A. Feinerman
Keyword(s):  
Reynolds Number ◽  
Lab On A Chip ◽  
Microfluidic Devices ◽  
Reynolds Numbers ◽  
Mixing Efficiency ◽  
Minimal Amount ◽  
Microfluidic Mixer ◽  
Mixing Performance ◽  
Rapid Mixing ◽  
Microfluidic Flows

Mixing is often crucial to the operation of various microfluidic devices. And the most common objective is rapid mixing between two initially segregated fluid streams in a minimal amount of space. In microfluidic flows characterized by incompressibility and low Reynolds number, however, turbulence is almost entirely absent and mixing generally relies on diffusion. Therefore, based on the properties of the fluids involved, it can take impractically long to achieve high mixing efficiency in some cases. To resolve this problem, this paper demonstrates a novel compliant micromixer made of thermoplastic films for lab-on-a-chip applications. The microfluidic mixer utilizes self-rotation effects to achieve high mixing efficiency at Reynolds numbers below 100. In addition, a possible design is suggested for a thermoplastic voltage-actuated micromixer which can lead to even better mixing performance at Reynolds numbers below 1.

A Comparative Analysis of Mixing Performance of Power-Law Fluid in Cylindrical Microchannels With Sudden Contraction/Expansion

2020 ◽  
Vol 142 (6) ◽  
Author(s):  
A. Banerjee ◽  
A. K. Nayak ◽  
B. Weigand
Keyword(s):  
Pressure Drop ◽  
Power Law ◽  
Flow Behavior ◽  
Geometric Parameters ◽  
Mixing Efficiency ◽  
Flow Behavior Index ◽  
Mixing Performance ◽  
Geometric Configurations ◽  
Wide Range ◽  
Behavior Index

Abstract This paper focuses on the comparative electrokinetic micromixing of non-Newtonian fluid in cylindrical microchannels with surface potential heterogeneity due to sudden constriction/expansion. In numerical simulations, the rheology of the aqueous solution is considered to follow power-law characteristic. Based on the Poisson–Nernst–Planck model, the simulations are performed to investigate the mixing efficiency and pressure drop for constricted and expanded configurations over a wide range of the flow behavior index, potential patch strength, and geometric parameters. The results show that, irrespective of geometric configurations, the mixing efficiency can be improved significantly by increasing the flow behavior index, geometric parameters, and the overpotential patch strength. In addition, it is also revealed that the constricted geometry yields better mixing as compared to the other configuration, but the average pressure drop shows reverse characteristics. Thus, a parametric relationship is tried to be established between mixing efficiency and pressure drop for both these configurations to propose an effective and efficient micromixer, which can produce maximum possible mixing efficiency with minimum pressure drop.

scholarly journals On connecting large vessels to small. The meaning of Murray's law.

1981 ◽  
Vol 78 (4) ◽  
pp. 431-453 ◽  
Author(s):  
T F Sherman
Keyword(s):  
Reynolds Number ◽  
Vessel Wall ◽  
Functional Relationship ◽  
Sectional Area ◽  
Parent Vessel ◽  
Cross Sectional ◽  
Murray's Law ◽  
Murray’S Law ◽  
Flow Velocity Profile ◽  
Large Vessels

A large part of the branching vasculature of the mammalian circulatory and respiratory systems obeys Murray's law, which states that the cube of the radius of a parent vessel equals the sum of the cubes of the radii of the daughters. Where this law is obeyed, a functional relationship exists between vessel radius and volumetric flow, average linear velocity of flow, velocity profile, vessel-wall shear stress, Reynolds number, and pressure gradient in individual vessels. In homogeneous, full-flow sets of vessels, a relation is also established between vessel radius and the conductance, resistance, and cross-sectional area of a full-flow set.

Analysis of mixing performances in microchannel with obstacles of different aspect ratios

2019 ◽  
Vol 233 (5) ◽  
pp. 1045-1051 ◽  
Author(s):  
Bappa Mondal ◽  
Sukumar Pati ◽  
PK Patowari
Keyword(s):  
Reynolds Number ◽  
Pressure Drop ◽  
Aspect Ratio ◽  
Flow Condition ◽  
Schmidt Number ◽  
Mixing Efficiency ◽  
Rectangular Microchannel ◽  
Mixing Performance ◽  
Aspect Ratios ◽  
Flow Through

In this study, the mixing performance and pressure drop characteristics have been numerically analyzed for flow through rectangular microchannel with obstacles in the walls arranged in a staggered manner. Three different aspect ratios (AR) of the obstacles are considered, namely 4:1, 1:1, and 1:4. The effects of aspect ratio of the obstacles on the mixing efficiency and the pressure drop are analyzed and compared with that of the channel without obstacle. The results are presented in terms of Reynolds number (Re) and Schmidt number (Sc) in the following range: 0.2 ≤ Re ≤ 1 and 500 ≤ Sc ≤ 1500. Enhanced mixing efficiency is achieved for the case of microchannel with obstacles and the corresponding pressure drop is also found to be higher. The mixing efficiency as well as the pressure drop is maximum for AR = 1:4 among all the geometries considered in the analysis in same flow condition. Furthermore, for a given configuration of the microchannel the mixing efficiency is governed by the mass Peclet number and, accordingly, the mixing efficiency increases with the decrease in Schmidt number for a given Reynolds number.

Mixing performance of micromixers with fractal obstacles based on Murray's law

2021 ◽  
Author(s):  
Xueye Chen ◽  
Yaolong Zhang ◽  
Xingxing Yu ◽  
Xiangyang Wang ◽  
Xiangwei Zeng ◽  
...  
Keyword(s):  
Mixing Performance ◽  
Murray's Law ◽  
Murray’S Law

Tesla Valves in Micromixers

2014 ◽  
Vol 12 (1) ◽  
pp. 397-403 ◽  
Author(s):  
Chin-Tsan Wang ◽  
Yan-Ming Chen ◽  
Pei-An Hong ◽  
Yi-Ta Wang
Keyword(s):  
Reynolds Number ◽  
Channel Wall ◽  
Simple Structure ◽  
Simulation Analysis ◽  
Mixing Efficiency ◽  
Flow Mechanism ◽  
Chemical Reactors ◽  
Special Flow ◽  
Mixing Performance ◽  
Tesla Valve

Abstract Micromixers are the devices which have the ability to mix liquids uniformly. However, a Tesla valve has the potential for micromixer development because of its simple structure and special flow mechanism. In this study, a numerical simulation analysis of a new Tesla-type micromixer was designed by placing a flow plate into a micromixer, which has a contact angle of 30° with the channel wall. The optimization of the geometric parameter, aspect ratio (AR) and the Reynolds number (Re) effect is discussed. The results show that the optimal geometric parameters of the unit Tesla-type micromixer are θ1 = 45°, θ2 = 30°, A = 0.3 mm, B = 0.22 mm, C = 0.3 mm, D = 0.25 mm, and the mixing efficiency can achieve εmixing = 0.953 by passing three-unit Tesla-type micromixers (inverse-type, Re = 1, AR = 1). The Tesla-type micromixers designed in this study, which have a lower pressure drop and a higher mixing performance at a low Reynolds number, can contribute to the application of biomedical chips and chemical reactors.

Effects of Obstacles on the Mixing Performance in Microchannels

2007 ◽  
Author(s):  
Tae-An Kim ◽  
Youn-Jea Kim
Keyword(s):  
Reynolds Number ◽  
Pressure Drop ◽  
Aspect Ratio ◽  
Lower Layer ◽  
Flow Direction ◽  
Diffusion Path ◽  
Mixing Efficiency ◽  
Convection Flow ◽  
Rectangular Microchannel ◽  
Mixing Performance

The mixing of two or more fluid streams in microchannels needs quite long channel lengths. Therefore, in order to improve the mixing performance, obstacles have been placed in the channel to disrupt flow and to reduce the diffusion path. The disruption to flow velocity field alters the flow direction from one fluid to another. Properly designed geometric parameters, such as layout, angle with main flow direction and aspect ratio of obstacles, will be resulted in improving the mixing performance with only little increase of the pressure drop. In this study, T-type rectangular microchannel is used, which has two inlets with W×H×L = 100×100×100 μm3 and one outlet with W×H×L = 200×100×6950 μm3. Furthermore, the mixing channel has obstacles which are placed with an angle of inclination and with dimensions W×H×L = 10×100×h μm3 on the lower layer. In order to estimate the performance of the mixing, numerical analyses are carried out with water and ethanol. Especially, the diffusion coefficient, D, is set to 10−10 m2/s for simulating two-fluid diffusion-convection flow, the mixing efficiency and the pressure drop of microchannel are investigated with various values of the angle of inclination, aspect ratio (h = αH) of obstacle and Reynolds number. When the flow passes through on the obstacles, rotation flow is observed. This flow pattern is repeated at each cycle. Besides, in each case that obstacles are turned to the center of channel and to the side walls, rotational direction is changed reversely. In case of pressure drop, as the Reynolds number, the angle of obstacle (θ) and the aspect ratio (α) are increased, the pressure drop is also increased. Results show that the ratio between the maximum and minimum of pressure drop is the order-of-magnitude of 1 at Re = 1.667. Results also show that the angle of inclination of obstacles has more influence on the mixing performance than the height of obstacles and Reynolds number.

Heat Transfer for High Aspect Ratio Rectangular Channels in a Stationary Serpentine Passage With Turbulated and Smooth Surfaces

2013 ◽  
Author(s):  
Matthew A. Smith ◽  
Randall M. Mathison ◽  
Michael G. Dunn
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Aspect Ratio ◽  
Flow Behavior ◽  
Reynolds Numbers ◽  
Hydraulic Diameter ◽  
Internal Cooling ◽  
Number Range ◽  
Aspect Ratios ◽  
Parallel Configuration

Heat transfer distributions are presented for a stationary three passage serpentine internal cooling channel for a range of engine representative Reynolds numbers. The spacing between the sidewalls of the serpentine passage is fixed and the aspect ratio (AR) is adjusted to 1:1, 1:2, and 1:6 by changing the distance between the top and bottom walls. Data are presented for aspect ratios of 1:1 and 1:6 for smooth passage walls and for aspect ratios of 1:1, 1:2, and 1:6 for passages with two surfaces turbulated. For the turbulated cases, turbulators skewed 45° to the flow are installed on the top and bottom walls. The square turbulators are arranged in an offset parallel configuration with a fixed rib pitch-to-height ratio (P/e) of 10 and a rib height-to-hydraulic diameter ratio (e/Dh) range of 0.100 to 0.058 for AR 1:1 to 1:6, respectively. The experiments span a Reynolds number range of 4,000 to 130,000 based on the passage hydraulic diameter. While this experiment utilizes a basic layout similar to previous research, it is the first to run an aspect ratio as large as 1:6, and it also pushes the Reynolds number to higher values than were previously available for the 1:2 aspect ratio. The results demonstrate that while the normalized Nusselt number for the AR 1:2 configuration changes linearly with Reynolds number up to 130,000, there is a significant change in flow behavior between Re = 25,000 and Re = 50,000 for the aspect ratio 1:6 case. This suggests that while it may be possible to interpolate between points for different flow conditions, each geometric configuration must be investigated independently. The results show the highest heat transfer and the greatest heat transfer enhancement are obtained with the AR 1:6 configuration due to greater secondary flow development for both the smooth and turbulated cases. This enhancement was particularly notable for the AR 1:6 case for Reynolds numbers at or above 50,000.

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