Microchannel miter bend effects on pressure equalization and vortex formation (original) (raw)

A review of single-phase pressure drop characteristics microchannels with bends

Journal of Mechatronics, Electrical Power, and Vehicular Technology, 2021

Microfluidic use in various innovative research, many fields aimed at developing an application device related to handling fluid flows in miniature scale systems. On the other hand, on the use of micro-devices for fluid flow the existence of bends cannot be avoided. This research aims to make a comprehensive study of fluid flow characteristics through a microchannel with several possible bends. This study was conducted by comparing Reynolds number versus pressure drop in a serpentine microchannel to gain bends loss coefficient. The result showed that the fluid flow with Re 100 did not affect the pressure drop, but on the Reynolds number above that, the pressure drop was increased along with the appears of vortices in the outer and inner walls around the channel bends which causes an increase in an additional pressure drop. The other finding shows that the reduction in diameter bend tube can increase the pressure drop.

Modeling the Effect of Channel Bends on Microfluidic Flow

The bends of different angles have many applications in microfluidic applications and it is very important to understand the flow behavior in these microbends. This paper presents the modeling of the flow behavior in micro bends of various angles in order to meet with implementation of expected flow behavior. As the sharp-angle-bends are very rare in actual applications due to their higher pressure loss and disturbance to the original laminar flow, this paper presents the results on analysis of microchannel with different bend angles. A series of rectangular microchannels with the dimensions in the range of 200µm and with the bend angles of 45°, 60°, 75°, 90°, 120°, 135°, 150° and 180° have been modeled using finite element method. The fluid characteristics such as flow rate and pressure loss have been established. The results also show that the flow separation and recirculation occur when the flow passes through the convex corner of the bend and becomes more critical as the bend an...

DEVELOPING FLOW IN THE INLET REGION OF BIFURCATIONS IN MICROCHANNELS WITH SYMMETRIC ANGULATION

Proceedings of the 10th CONEM, 2018

The aim of this work is to evaluate the behavior of the velocity fields and predict the length of the not fully developed flow region, in the inlet of symmetric bifurcations of rectangular sectioned microchannels. An equation found in specialized literature, developed for prediction in conventional and thin curved tubes, was tested. This formulation was adapted for microtubes. Three experimental micro-devices were utilized, each fork with a larger side and a thinner side. The channel widths, flow rates and bifurcation angles were varied. Flowing were simulated via finite difference method and the lengths of the region were measured and compared to the values calculated through the proposed equation. The obtained results allowed to conclude that the equation predicts with good accuracy the length of the region of flow development, for a range of angles between 30 and 60 degrees. For the case of flow variation, it was possible to conclude that it predicted with good coincidence of results flow rates between 1.39x10E-10 m3/s and 5.56x10E-10 m3/s. In dimensional terms, bifurcations with outlets widths smaller than 200 microns have shown the best agreement. The applicability of the equation for asymmetric bifurcations is recommendable to be tested in future works.

Prediction and Measurement of Pressure Drop of Water Flowing in a Rectangular Microchannel

This paper presents experimental results of pressure drop measurement and prediction of water flowing through a copper rectangular microchannel with a hydraulic diameter of 437 µm. The aim of this work is to identify discrepancies between experimental data and macrochannel theory. An inlet temperature of 60 o C was kept constant at the channel entrance and the experiments were performed with Reynolds numbers (based on the mean velocity and hydraulic diameter) ranging up to 4500. The results show that the pressure drop prediction agrees with the theory. However, the trend of Poiseuille number with the Reynolds number was not constant for laminar flow. This could be due to the entrance effect. Moreover, the friction factor theory could predict the experimental data for turbulent flow. Thus, in this experiment, the theory for flow in macro passages is still applicable.

Influence of elasticity on the vortical structures formed in micro-channels geometries

The paper is dedicated to the experimental studies and numerical simulations of homogeneous fluid flows in the micro-channels. The aim of the present study is to investigate and model vortical structures and flow separation phenomena in two different micro geometries: (i) T-channels of trapezoidal section with small aspect ratio width/depth, and (ii) Y-bifurcation with a square cross-section. The first geometry is used to study the flow rate influence on the possible appearance of micro-vortices located at the edges of the trapeze in the vicinity of the corner. The second geometry is investigated in relation to the vortex formation at the junction, if the flow rate distribution between the branches is not symmetric. One of the main goal of the work is to determine the influence of elasticity concentration on the topology of the vortical structures, respectively to establish a critical threshold of elasticity which determines qualitatively changes in the flow pattern. The tested flui...