Papers by Keyword: Micro-Channel

Abstract: The injection molding process of micro plate devices requires several concerns in order to produce a quality output. In part of determining the best parameter settings, among other considerations that need to be taken are the types of plastic materials selected and the mold design. Molding parameters such as packing time, cooling temperature, molding and melting temperatures, packing and injection pressures are the most important factors affecting warpage of the micro plate part. These factors and their interactions were investigated in this research. The effects of processing parameter on the warpage of flat micro devices were analyzed according to the Taguchi method. In this paper, based on the range analysis, the parameter effective sequence was got, as well as the best processing parameters. The molding packing time has the strongest effects on the warpage, and the molding temperature is the secondary parameter. The cooling time has the lowest effects.

Abstract: An experiment-calculated investigation of forced convection of nanofluids based on Al₂O₃ nanoparticles was carried out. The hydrodynamic description and a model of homogeneous nanofluids were used. The homogeneous nanofluids model assumes that the hydrodynamics and heat transfer can be described by conventional Navier-Stokes and heat transfer equations with the physical parameters corresponding to nanofluids. The results showed that this model very well described the experimental data in some cases. However, in some other cases, there are discrepancies between experiment and theory that can be explained by the real heterogeneity of nanofluids and the errors in the experimental determination of thermal conductivity and viscosity of nanofluids.

Abstract: Asymptotic solution for the shear stress distributions and velocity profiles of steady electroosmotic (EO) and magnetohydrodynamic (MHD) flows are obtained in a parallel flat plate microchannel. A fully-developed flow is considered and the fluid obeys a constitutive relation based in a simplified Phan-Thien-Tanner model. The effect of the following dimensionless parameters on the fluid flow control is predicted: the viscoelastic parameter and the Hartmann number. The momentum equation, boundary conditions and the constitutive rheological model are combined to formulating a nonlinear differential equation to solve the shear stress, which is expanded in a regular expansion series in powers of small Hartmann numbers. This limit of small Hartmann numbers and low electrical conductivity in the buffer solution correspond to the range where the electric and magnetic effects can be used to move a charged solution in the flow control and sample handling in biomedical and chemical analysis.

Abstract: Unsteady computations of laminar flow have been performed for two-dimensional configurations of micro-channel equipped with two synthetic jets. The effect of phasing has been investigated at in-phase and 180̊ out-of-phase of the synthetic jet actuators at a fixed operating frequency and oscillating amplitudes. It was shown that the 180̊ out-of-phase configuration of the synthetic jets promotes better and more continuous flow mixing within the channel during the oscillation. This was due to the discrete pattern of vortex forming which disrupts the main channel flow. The 180̊ out-of-phase jet configuration exhibits higher cooling performance compared to the in-phase jet configuration in terms of the reduction in the maximum temperature in the silicon wafer.

Abstract: Numerical investigation of heat transfer enhancement in two-dimensional microchannel heat sink (MCHS) using Al₂O₃-water, CuO-water and TiO₂-water was conducted. The effect of different type of nanoparticles at particle volume concentration of 1%, 2% and 5% on the thermal performance in the MCHS was examined. The thermal performance is increased when nanofluids with high thermal conductivity and low dynamic viscosity was used. As the particle volume concentration increases, the heat transfer performance also improved. The result shows that the heat transfer performance of all the nanofluids used in this study was better than that of pure water. Overall, nanofluids with Al₂O₃-water at 5% particle volume concentration show the best cooling performance.

Abstract: This paper presents a two-dimensional numerical study on the interaction of synthetic jet and the cross flow inside a microchannel. Three different turbulence models namely the standard k-, Shear Stress Transport (SST) and Scale Adaptive Simulation Shear Stress Transport (SAS SST) were tested for their ability to predict the flow structure generated by a synthetic jet. The results are validated against existing experimental data. The SAS SST model was found to give the most realistic prediction of the fluid flow based on the good agreement with experimental data.

Abstract: A numerical study is conducted to predict the effects of physical parameters of a double layer microchannel heat sink on heat transfer. The physical parameters investigated are the channel height and channel width for different flow orientation at the upper and lower channels. For the range of Reynolds number investigated, results show that parallel flow configuration leads to better heat transfer performance than counter flow. Lower thermal resistance can be achieved in a double-layered microchannel heat sink with higher channel height and lower channel width.

Abstract: A fluid dynamics in a micro channel for analytical chemistry and different aspects of this type of flow for specific application has remained a long-acting problem in the last two decades considering its numerus applications in various fields, thus, Surface tension and wall adhesive forces are often used to transport fluid through micro channels in Micro Electromechanical system devices or to measure the transport and position of small amounts of fluid using micropipettes. Here we took the advantages of wall adhesion and surface tension at the air/fluid interface, fluid rises through the channel and study also calculate the velocity, pressure and shape and position of the fluid surface, the model consist of a capillary channel of radius 50μm and a chamber. The study demonstrated that the fluid freely flown into the chamber 2mm/s without using any external mechanism.

Abstract: Nanofluid is a promising coolant for high-heat dissipation electronics device or system. The effect of nanofluids as thermal performances on a rectangular shape microchannel heat sink (MCHS) is analytically studied. Al₂O₃, SiC, and CuO nanoparticles dispersing in water were considered for analysis. A steady, laminar, and incompressible flow with constant heat flux was assumed in the channel. Nanofluids with concentrations of 0.5 to 4.0 vol. % were analyzed at two different inlet velocities of 0.5 m/s and 3.0 m/s. The results showed that highest thermal conductivity enhancement was 12.45% by using SiC-water nanofluids. In the case of Al₂O₃-water and CuO-water nanofluids maximum improvement were 11.98% and 11.36%, respectively for 4.0 vol. % of nanoparticle concentration. Furthermore, nanofluids as a coolant instead of water showed a highest improve of heat flux 8.51% for water-CuO, and 6.44% and 5.60% increase for Al₂O₃-water and SiC-water, respectively. The maximum pumping power found 0.33 W at 3 m/s and 0.0091 W at 0.5 m/s for the same concentration of 4.0 vol. % for all of these nanofluids.

Abstract: A study has been conducted on the heat transfer of various oscillatory frequencies of pulsation flow through a porous channel network subjected to a constant wall heat flux. The surface temperature distributions, pressure drop, unit thermal resistance and local Nusselt number for different oscillatory frequencies were mainly investigated.