Flow Characteristics of Aluminium Oxide Nanofluids

2009 ◽  
Author(s):  
Vanessa M. Egan ◽  
Patrick A. Walsh ◽  
Edmond J. Walsh
Keyword(s):  
Pressure Drop ◽  
Flow Rate ◽  
Volume Fraction ◽  
Relative Viscosity ◽  
Flow Characteristics ◽  
Aluminium Oxide ◽  
Nanoparticle Size ◽  
Rotational Viscometer ◽  
Volume Fractions ◽  
Viscosity Measurements

The current study is an investigation in the flow characteristics of aluminium oxide nanofluids. Relative viscosity measurements are obtained for varying volume fractions using both a rotational viscometer and an experimental setup designed for pressure drop measurements in tubes. The effect of nanoparticle size and preparation method is also investigated as predispersed nanofluids of nominal particle size 10nm and 50nm are compared with each other and with a fluid mixed from Al2O3 nanopowder. Volume fractions of between 1% and 7% were tested. The first method employed to obtain viscosities is based on the Hagen-Poiseuille equation for laminar pipe flow, where pressure drop measurement and flow rate measurements are used to determine relative viscosities of various nanofluids samples. Viscosity measurements were also obtained for a number of solutions on a rotational viscometer and compared to the latter and existing models available in the literature. Overall, it was found during experimentation that the relationship between pressure and flow rate for the various nanofluids was linear indicating that the fluids were Newtonian in nature. An increase in viscosity was recorded for increasing volume fraction; however this was seen to be negligible for volume fractions lower than 1%. Overall it was also seen that both methods of determining relative viscosity were in good agreement. There was not a clear indication of the effect of nanoparticle size on the relative viscosity however the nanofluids formulated from purchased Al2O3 powder resulted in a considerably lower relative viscosity when compared to both nanofluids purchased pre-dispersed from suppliers.

Experimental Investigation of Effect of Tip Coolant Ejection on Internal Flow Characteristics Within a Realistic Blade Coolant Channel

2013 ◽  
Author(s):  
Jian Pu ◽  
Zhaoqing Ke ◽  
Jianhua Wang ◽  
Lei Wang ◽  
Hongde You
Keyword(s):  
Experimental Investigation ◽  
Reynolds Number ◽  
Pressure Drop ◽  
Turbine Blade ◽  
Flow Rate ◽  
Flow Characteristics ◽  
Reynolds Numbers ◽  
Flow Ratio ◽  
Lp Turbine ◽  
Mass Flow Ratio

This paper presents an experimental investigation on the characteristics of the fluid flow within an entire coolant channel of a low pressure (LP) turbine blade. The serpentine channel, which keeps realistic blade geometry, consists of three passes connected by a 180° sharp bend and a semi-round bend, 2 tip exits and 25 trailing edge exits. The mean velocity fields within several typical cross sections were captured using a particle image velocimetry (PIV) system. Pressure and flow rate at each exit were determined through the measurements of local static pressure and volume flow rate. To optimize the design of LP turbine blade coolant channels, the effect of tip ejection ratio (ER) from 180° sharp bend on the flow characteristics in the coolant channel were experimentally investigated at a series of inlet Reynolds numbers from 25,000 to 50,000. A complex flow pattern, which is different from the previous investigations conducted by a simplified square or rectangular two-pass U-channel, is exhibited from the PIV results. This experimental investigation indicated that: a) in the main flow direction, the regions of separation bubble and flow impingement increase in size with a decrease of the ER; b) the shape, intensity and position of the secondary vortices are changed by the ER; c) the mass flow ratio of each exit to inlet is not sensitive to the inlet Reynolds number; d) the increase of the ER reduces the mass flow ratio through each trailing edge exit to the extent of about 23–28% of the ER = 0 reference under the condition that the tip exit located at 180° bend is full open; e) the pressure drop through the entire coolant channel decreases with an increase in the ER and inlet Reynolds number, and a reduction about 35–40% of the non-dimensional pressure drop is observed at different inlet Reynolds numbers, under the condition that the tip exit located at 180° bend is full open.

scholarly journals Haemorheology in dilute, semi-dilute and dense suspensions of red blood cells

2019 ◽  
Vol 872 ◽  
pp. 818-848 ◽  
Author(s):  
Naoki Takeishi ◽  
Marco E. Rosti ◽  
Yohsuke Imai ◽  
Shigeo Wada ◽  
Luca Brandt
Keyword(s):  
Red Blood Cells ◽  
Intrinsic Viscosity ◽  
Blood Cells ◽  
Volume Fraction ◽  
Relative Viscosity ◽  
Shear Plane ◽  
Constitutive Law ◽  
Stable Mode ◽  
Volume Fractions ◽  
Wide Range

We present a numerical analysis of the rheology of a suspension of red blood cells (RBCs) in a wall-bounded shear flow. The flow is assumed as almost inertialess. The suspension of RBCs, modelled as biconcave capsules whose membrane follows the Skalak constitutive law, is simulated for a wide range of viscosity ratios between the cytoplasm and plasma,$\unicode[STIX]{x1D706}=0.1$–10, for volume fractions up to$\unicode[STIX]{x1D719}=0.41$and for different capillary numbers ($Ca$). Our numerical results show that an RBC at low$Ca$tends to orient to the shear plane and exhibits so-called rolling motion, a stable mode with higher intrinsic viscosity than the so-called tumbling motion. As$Ca$increases, the mode shifts from the rolling to the swinging motion. Hydrodynamic interactions (higher volume fraction) also allow RBCs to exhibit tumbling or swinging motions resulting in a drop of the intrinsic viscosity for dilute and semi-dilute suspensions. Because of this mode change, conventional ways of modelling the relative viscosity as a polynomial function of$\unicode[STIX]{x1D719}$cannot be simply applied in suspensions of RBCs at low volume fractions. The relative viscosity for high volume fractions, however, can be well described as a function of an effective volume fraction, defined by the volume of spheres of radius equal to the semi-middle axis of a deformed RBC. We find that the relative viscosity successfully collapses on a single nonlinear curve independently of$\unicode[STIX]{x1D706}$except for the case with$Ca\geqslant 0.4$, where the fit works only in the case of low/moderate volume fraction, and fails in the case of a fully dense suspension.

THE EFFECT OF DIFFERENT LOCATIONS OF TRACHEAL STENOSIS TO THE FLOW CHARACTERISTICS USING RECONSTRUCTED CT-SCANNED IMAGE

2012 ◽  
Vol 12 (04) ◽  
pp. 1250066 ◽  
Author(s):  
NASRUL HADI JOHARI ◽  
KAHAR OSMAN ◽  
ZULIAZURA MOHD SALLEH ◽  
JUHARA HARON ◽  
MOHAMMED RAFIQ ABDUL KADIR
Keyword(s):  
Pressure Drop ◽  
Flow Rate ◽  
Tracheal Stenosis ◽  
Flow Behavior ◽  
Flow Characteristics ◽  
Flow Conditions ◽  
Inlet Flow Rate ◽  
Exhaled Air ◽  
Scanned Image ◽  
The Right

The presence of tracheal stenosis would alter the flow path of the inhaled and exhaled air and subsequently changed the flow behavior inside the trachea and main bronchi. Therefore, it was our aim to investigate and predict the changes of flow behavior along with the pressure distribution with respect to the presence of stenosis on the tracheal lumen. In this study, actual CT scan images were extracted for flow modeling purposes. The images were then reconstructed to mimic the effect of different stenosis locations. This method overcomes the problem of the absence of actual images for different tracheal stenosis locations. The flow was subjected to different breathing situations corresponding to low, moderate and rigorous activities. The results showed that for flow over the stenosis farthest from the bifurcation, the pressure drop was insignificant for all breathing situations. At the same time, the inlet flow rate at the bifurcation showed less air flows into the right lung as compared to healthy flow conditions. On the other hand, for the flow over stenosis closest to the bifurcation, the pressure drop near the bifurcation area was very significant at high flow rate.

Numerical Study of Forced Convection of Nanofluids in a Microchannel Heat Sink

2008 ◽  
Author(s):  
Parisa Vaziee ◽  
Omid Abouali
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Sink ◽  
Volume Fraction ◽  
Numerical Study ◽  
Heat Removal ◽  
Al2o3 Nanoparticles ◽  
Microchannel Heat Sink ◽  
Particle Volume ◽  
Volume Fractions

Effectiveness of the microchannel heat sink cooled by nanofluids with various particle volume fractions is investigated numerically using the latest theoretical models for conductivity and viscosity of the nanofluids. Both laminar and turbulent flows are considered in this research. The model of conductivity used in this research accounts for the fundamental role of Brownian motion of the nanoparticles which is in good agreement with the experimental data. The changes in viscosity of the nanofluid due to temperature variation are considered also. Final results are compared with the experimental measurements for heat transfer coefficient and pressure drop in microchannel. Enhancement in heat transfer is achieved for laminar flow with increasing of volume fraction of Al2O3 nanoparticles. But for turbulent flow an enhancement of heat removal was not seen and using higher volume fractions of nanoparticles increases the maximum substrate temperature. Pressure drop is increased with using nanofluids because of the augmentation in the viscosity and this increase is more noticeable in higher Reynolds numbers.

scholarly journals Peristaltic transport of a two-layered fluid in a catheterized tube

2012 ◽  
Vol 39 (4) ◽  
pp. 291-311
Author(s):  
Amit Medhavi ◽  
U.K. Singh
Keyword(s):  
Pressure Drop ◽  
Linear Relationship ◽  
Layer Thickness ◽  
Friction Force ◽  
Flow Rate ◽  
Tube Wall ◽  
Flow Characteristics ◽  
Tube Size ◽  
Friction Forces ◽  
Catheter Size

The flow of a two-layered Newtonian fluid induced by peristaltic waves in a catheterized tube has been investigated. The expressions for the flow characteristics- the flow rate, the pressure drop and the friction forces at the tube and catheter wall are derived. It is found that the pressure drop increases with the flow rate but decreases with the increasing peripheral layer thickness and a linear relationship between pressure and flow exists. The pressure drop increases with the catheter size (radius) and assumes a high asymptotic magnitude at the catheter size more that the fifty percent of the tube size. The friction forces at the tube and catheter wall posses characteristics similar to that of the pressure drop with respect to any parameter. However, friction force at catheter wall assumes much smaller magnitude than the corresponding value at the tube wall.

Heat Transfer and Pressure Drop Simulation of CO2-Hydrate Mixture in Tube

2017 ◽  
Vol 25 (01) ◽  
pp. 1750005 ◽  
Author(s):  
Benedict Prah ◽  
Rin Yun
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Volume Fraction ◽  
Flow Characteristics ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Mixture Flow ◽  
Heat Transfer Coefficients ◽  
Two Phases ◽  
Energy Equations

The formation of CO2 hydrate during CO2 transportation presents a complex two-phase flow within tube. A two-dimensional CFD model for CO2 hydrate mixture flow in tube is derived based on the Eulerian multiphase flow modeling approach in which the two phases consist of CO2 gas and CO2 hydrate particles. A coupled Eulerian multiphase and nonisothermal flow model without phase-change is developed based on COMSOL Multiphysics built-in application modes. The model couples the mass, momentum, and energy equations for the two phases to solve the temperature and flow characteristics of the CO2 hydrate mixture flow in tube. CO2 hydrate particles are found to settle down during flow even under high velocity operation. The pressure drop increased linearly with inlet volume fraction from 1.29[Formula: see text]kPa for 0.1–5.2[Formula: see text]kPa for 0.5, and the related overall heat transfer coefficients of the CO2 hydrate mixture computed from the model ranged from 980 to 4000[Formula: see text]W/m2K with variation of CO2 hydrate volume fraction.

Numerical investigation on turbulent convective heat transfer of nanofluid flow in a square cross-sectioned duct

2019 ◽  
Vol 29 (4) ◽  
pp. 1432-1447 ◽  
Author(s):  
Gülbanu Şenay ◽  
Metin Kaya ◽  
Engin Gedik ◽  
Muhammet Kayfeci
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Friction Factor ◽  
Flow Characteristics ◽  
Constant Heat Flux ◽  
Ansys Fluent ◽  
Square Duct ◽  
Content Type ◽  
Volume Fractions ◽  
Darcy Friction Factor

Purpose The purpose of this study is to numerically investigate the heat transfer enhancement by using two different nanofluids flow throughout the square duct under a constant heat flux (500 × 103 W/m2). Design/methodology/approach In numerical computations, ANSYS Fluent code based on the finite volume method was used to solve governing equations by iteratively. Water, Al2O3-water and TiO2-water nanofluids were used for different flow velocities changing 1 m/s to 8 m/s (i.e. Reynolds number varying from 3,000 to 100,000). Findings The results were compared with results published previously in the literature and close agreement was observed especially considering Dittus and Boelter correlation for water. It was found that from the obtained results, increasing flow velocity and volume fractions of nanoparticles has caused to increase Nu number for all cases. Besides, variations of pressure drop, Darcy friction factor are presented graphically and discussed in detail. The results are consistent with a deviation of 1.3 to 15 per cent with the results of other researchers. Originality/value The effects of the Re numbers and volume fractions of nanoparticles (0.01 ≤ Φ ≤ 0.04) on the heat transfer and fluid flow characteristics such as average Nu number, pressure drop (ΔP) and Darcy friction factor (f) were investigated.

Motion of a deformable capsule through a hyperbolic constriction

1994 ◽  
Vol 279 ◽  
pp. 135-163 ◽  
Author(s):  
Anne Leyrat-Maurin ◽  
Dominique Barthes-Biesel
Keyword(s):  
Pressure Drop ◽  
Flow Rate ◽  
Stokes Equations ◽  
Flow Characteristics ◽  
Quantitative Information ◽  
Maximum Energy ◽  
Centre Of Mass ◽  
Intrinsic Properties ◽  
Constant Flow Rate ◽  
Reynolds Number Flow

A model for the low-Reynolds-number flow of a capsule through a constriction is developed for either constant-flow-rate or constant-pressure-drop conditions. Such a model is necessary to infer quantitative information on the intrinsic properties of capsules from filtration experiments conducted on a dilute suspension of such particles. A spherical capsule, surrounded by an infinitely thin Mooney-Rivlin membrane, is suspended on the axis of a hyperbolic constriction. This configuration is fully axisymmetric and allows the entry and exit phenomena through the pore to be modelled. An integral formulation of the Stokes equations describing the flow in the internal and external domains is developed. It provides a representation of the velocity at any location in the flow as a function of the unknown forces exerted by the boundaries on the fluids. The problem is solved by a collocation technique in the case where the internal and external viscosities are equal. Microscopic quantities (instantaneous geometry, centre of mass velocity, elastic tensions in the membrane) as well as macroscopic quantities (entry time, additional pressure drop or flow rate reduction) are predicted as a function of the capsule intrinsic properties and flow characteristics. The results obtained for a capsule whose initial diameter is larger than that of the constriction throat show that the maximum energy expenditure occurs when the particle centre of mass is still upstream of the throat (typically 1 diameter away), and is thus due to the entry process. For large enough or rigid enough capsules, the model predicts entrance or exit plugging, in agreement with experimental observations. It is then possible to correlate the variation of the pore hydraulic resistance to the flow capillary number (ratio of viscous to elastic forces) and to the size ratio between the pore and the capsule.

Energy Transfer Enhancement Inside an Annulus Using Gradient Porous Ribs and Nanofluids

2020 ◽  
Vol 142 (12) ◽  
Author(s):  
Hamid Reza Talesh Bahrami ◽  
Ehsan Aminian ◽  
Hamid Saffari
Keyword(s):  
Heat Transfer ◽  
Porous Media ◽  
Pressure Drop ◽  
Volume Fraction ◽  
Reynolds Numbers ◽  
Relative Height ◽  
Transfer Enhancement ◽  
Volume Fractions ◽  
Flow Reynolds Number ◽  
Maximum Volume Fraction

Abstract Porous media and nanofluid utilization are two passive heat transfer improvement tools, which have been employed extensively in recent years. Porous media with gradient properties result in both a higher effective thermal conductivity and better local convective heat transfer because of conducting the flow to the desired regions. In this study, distinct porous ribs are located on the internal border of an annulus. Four different conditions are considered for permeability change of ribs, including the minimum and maximum Darcy numbers and linearly increasing or decreasing variation in the radial direction, called LIV and LVD, respectively. In the first step, effects of porous rib relative height, porous rib porosity, and flow Reynolds number on the thermal efficiency and pressure drop are investigated. The results show that the configuration with Da = LVD and W/Rh = 0.25 has the maximum performance number PN = 2, that is the Nusselt improvement over pressure drop increment. Porous ribs arrangement with W/Rh = 0.25 and the minimum porosity (ɛ = 0.9) give the best PN. In the next step, the effects of nanoparticle addition with different volume fractions to the base fluid in different Reynolds numbers are investigated. In this step, porous rib relative height is set to W/Rh = 0.25. The results show that the maximum volume fraction has the highest heat transfer enhancement (about 2–2.5 times) but the lower volume fractions have higher PNs (PN ≈ 2.5 at ϕ = 1% and Re = 500).

scholarly journals Relative Pressure Drop Model for Hydrate Formation and Transportability in Flowlines in High Water Cut Systems

Energies ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 686
Author(s):  
Trung-Kien Pham ◽  
Ana Cameirao ◽  
Aline Melchuna ◽  
Jean-Michel Herri ◽  
Philippe Glénat
Keyword(s):  
Pressure Drop ◽  
Oil And Gas ◽  
Produced Water ◽  
Volume Fraction ◽  
Hydrate Formation ◽  
Flow Characteristics ◽  
High Water ◽  
Relative Pressure ◽  
Gas Hydrate Formation ◽  
Water Cut

Today, oil and gas fields gradually become mature with a high amount of water being produced (water cut (WC)), favoring conditions for gas hydrate formation up to the blockage of pipelines. The pressure drop is an important parameter which is closely related to the multiphase flow characteristics, risk of plugging and security of flowlines. This study developed a model based on flowloop experiments to predict the relative pressure drop in pipelines once hydrate is formed in high water cutsystems in the absence and presence of AA-LDHI and/or salt. In this model, the relative pressure drop during flow is a function of hydrate volume and hydrate agglomerate structure, represented by the volume fraction factor (Kv). This parameter is adjusted for each experiment between 1.00 and 2.74. The structure of the hydrate agglomerates can be predicted from the measured relative pressure drop as well as their impact on the flow, especially in case of a homogeneous suspension of hydrates in the flow.

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