A Numerical Study of Unsteady Laminar Flow and Heat Transfer Through an Array of Rotating Rectangular Microchannels

Centrifugal microfluidics plays an important role for enabling many novel applications in life sciences. By controlling the rotating frequency, fluids can be handled and controlled without any actual pumps, actuators or active valves, resulting in cost effective and miniaturized techniques for fluid transport, valving, metering, switching, splitting and separation of fluids. In order to get a vivid picture of the underlying physics of centrifugal microfluidics, we have modeled and simulated fluid flow and heat transfer for water flowing through an array of rotating rectangular microchannels. A finite volume technique based on semi implicit pressure based equation (SIMPLE) algorithm has been developed to solve the Naiver-Stokes equations for unsteady laminar flow. The energy equation has been solved by applying repeated thermal boundary conditions at the wall in cross stream direction. The simulations show significant deviation of velocity and temperature profiles for rotating flow than those of non-rotating case. The results are presented for different flow Reynolds number and rotational Reynolds number.

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Effect of wall-mounted V-baffle position in a turbulent flow through a channel

International Journal of Numerical Methods for Heat &amp Fluid Flow ◽

10.1108/hff-06-2018-0270 ◽

2019 ◽

Vol 29 (10) ◽

pp. 3908-3937 ◽

Cited By ~ 9

Author(s):

Younes Menni ◽

Ahmed Azzi ◽

Ali J. Chamkha ◽

Souad Harmand

Keyword(s):

Heat Transfer ◽

Reynolds Number ◽

Stokes Equations ◽

Numerical Study ◽

Rectangular Channel ◽

Simple Algorithm ◽

Two Dimensions ◽

Large Reynolds Number ◽

Constant Property ◽

Content Type

Purpose The purpose of this paper is to carry out a numerical study on the dynamic and thermal behavior of a fluid with a constant property and flowing turbulently through a two-dimensional horizontal rectangular channel. The upper surface was put in a constant temperature condition, while the lower one was thermally insulated. Two transverse, solid-type obstacles, having different shapes, i.e. flat rectangular and V-shaped, were inserted into the channel and fixed to the top and bottom walls of the channel, in a periodically staggered manner to force vortices to improve the mixing, and consequently the heat transfer. The flat rectangular obstacle was put in the first position and was placed on the hot top wall of the channel. However, the second V-shaped obstacle was placed on the insulated bottom wall, at an attack angle of 45°; its position was varied to find the optimum configuration for optimal heat transfer. Design/methodology/approach The fluid is considered Newtonian, incompressible with constant properties. The Reynolds averaged Navier–Stokes equations, along with the standard k-epsilon turbulence model and the energy equation, are used to control the channel flow model. The finite volume method is used to integrate all the equations in two-dimensions; the commercial CFD software FLUENT along with the SIMPLE-algorithm is used for pressure-velocity coupling. Various values of the Reynolds number and obstacle spacing were selected to perform the numerical runs, using air as the working medium. Findings The channel containing the flat fin and the 45° V-shaped baffle with a large Reynolds number gave higher heat transfer and friction loss than the one with a smaller Reynolds number. Also, short separation distances between obstacles provided higher values of the ratios Nu/Nu0 and f/f0 and a larger thermal enhancement factor (TEF) than do larger distances. Originality/value This is an original work, as it uses a novel method for the improvement of heat transfer in completely new flow geometry.

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Experimental and Numerical Study to Enhance of Heat Transfer Coefficient in Air Flow Using Microchannel

Journal of University of Babylon for Engineering Sciences ◽

10.29196/jubes.v26i7.1492 ◽

2018 ◽

Vol 26 (7) ◽

pp. 112-123

Author(s):

Jalal M. Jalil ◽

Ghada A. Aziz ◽

Amjed A. Kadhim

Keyword(s):

Heat Transfer ◽

Heat Transfer Coefficient ◽

Transfer Coefficient ◽

Stokes Equations ◽

Numerical Study ◽

Simple Algorithm ◽

Navier Stokes ◽

Navier Stokes Equations ◽

Flow And Heat Transfer ◽

The Heat Transfer Coefficient

Experimental and numerical study of fluid flow and heat transfer in microchannel airflow is investigated. The study covers changing the cooling of micro-channel for the velocities and heater powers. The dimensions of the microchannel were, length = 0.1m, width = 0.001m, height = 0.0005 m. The experimental and numerical results were compared with the previous paper for velocities up to 20 m/s and heater powers up to 5 W and the comparison was acceptable. In this paper, the results were extended numerically for velocities up to 60 m/s. The numerical solution used finite volume (SIMPLE algorithm) to solve Navier Stokes equations (continuity, momentum and energy). The results show that the heat transfer coefficient increases up to 220 W/m2 oC for velocity 60 m/s.

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Numerical Modeling and Physical Simulation of Vortex Heat Transfer Enhancement Mechanisms Over Dimpled Reliefs

2010 14th International Heat Transfer Conference, Volume 2 ◽

10.1115/ihtc14-22334 ◽

2010 ◽

Cited By ~ 3

Author(s):

Alexander I. Leontiev ◽

Sergey A. Isaev ◽

Nikolai V. Kornev ◽

Yaroslav Chudnovsky ◽

Egon Hassel

Keyword(s):

Heat Transfer ◽

Reynolds Number ◽

Physical Simulation ◽

Stokes Equations ◽

Numerical Study ◽

Narrow Channel ◽

Discrete Models ◽

Navier Stokes ◽

Heat Output ◽

Flow And Heat Transfer

The paper presents a comprehensive analysis of conditions for numerical simulation and physical modeling of convective heat transfer in the vicinity of dimpled surface relief. Contradictory results, unreasonable assumptions, and non-justified conclusions are marked. Based on the analysis of physical experiments the correlation between the predictions and measured data is discussed. Detailed numerical study of turbulent air flow and heat transfer in the narrow channel with three types of dimples (spherical, conic and oval) was carried out. Various mathematical and discrete models, including, those based on solving Reynolds-averaged Navier-Stokes equations (RANS/URANS-SST), and also adaptive scale models (SAS-SST) are compared. The influence of flow parameters (Reynolds number) and geometric sizes (dimple diameter, depth, radius of rounding off of an edge, channel width and height) on local and integral characteristics of flow and heat transfer (total heat output and hydraulic losses) is determined. Special attention is given to reorganizing vortex structures and flow regime (with periodic fluctuations) with increasing relative dimple depth and Reynolds number. For the first time the influence of the scale factor of a constant cross-section channel is detailed. Thermal-hydraulic characteristics of various dimpled reliefs are compared, and the advantage of an oval dimple over a spherical one is shown.

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Laminar Heat Transfer in a Channel With Two Right-Angled Bends

Journal of Heat Transfer ◽

10.1115/1.3246720 ◽

1984 ◽

Vol 106 (3) ◽

pp. 591-596 ◽

Cited By ~ 6

Author(s):

R. S. Amano

Keyword(s):

Heat Transfer ◽

Reynolds Number ◽

Stokes Equations ◽

Numerical Study ◽

Local Heat Transfer ◽

Local Heat ◽

Navier Stokes ◽

Navier Stokes Equations ◽

Flow And Heat Transfer ◽

Long Channel

A numerical study is reported on the flow and heat transfer in the channel with two right-angled bends. The modified hybrid scheme was employed to solve the steady full Navier-Stokes equations with the energy equation. The computations were performed for different step heights created in a long channel. The local heat transfer rate along the channel wall predicted by employing the present numerical model showed good agreement with the experimental data. The behavior of the flow and the heat transfer were investigated for the range of Reynolds number between 200 and 2000 and for step height ratios H/W = 1, 2, and 3. Finally, the correlation of the average Nusselt number in such channels as a function of Reynolds number is postulated.

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Numerical Study of Circular Tube inserted Arc Belt on Fluid Flow and Heat Transfer under Laminar Flow

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.561.460 ◽

2013 ◽

Vol 561 ◽

pp. 460-465

Author(s):

Dong Hui Zhang ◽

Jiao Gao

Keyword(s):

Heat Transfer ◽

Fluid Flow ◽

Laminar Flow ◽

Wall Temperature ◽

Circular Tube ◽

Numerical Study ◽

Resistance Coefficient ◽

Uniform Wall Temperature ◽

Flow And Heat Transfer ◽

Uniform Wall

The objective of this paper is to study the characteristic of a circular tube with a built-in arc belt on fluid flow and heat transfer in uniform wall temperature flows. Numerical simulations for hydrodynamically laminar flow was direct ran at Re between 600 and 1800. Preliminary results on velocity and temperature statistics for uniform wall temperature show that, arc belt can swirl the pipe fluid, so that the fluid at the center of the tube and the fluid of the boundary layer of the wall can mix fully, and plays the role of enhanced heat transfer, but also significantly increases the resistance of the fluid and makes the resistance coefficient of the enhanced tube greater than smooth tube. The combination property PEC is all above 1.5.

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Numerical study of ferrofluid flow and heat transfer in the presence of a non-uniform magnetic field in rectangular microchannels

Heat Transfer-Asian Research ◽

10.1002/htj.21004 ◽

2012 ◽

Vol 41 (4) ◽

pp. 302-317 ◽

Cited By ~ 13

Author(s):

M. Mohammadpourfard

Keyword(s):

Magnetic Field ◽

Heat Transfer ◽

Uniform Magnetic Field ◽

Numerical Study ◽

Rectangular Microchannels ◽

Flow And Heat Transfer

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Experimental Study on Liquid Flow and Heat Transfer in Rough Microchannels

Advances in Condensed Matter Physics ◽

10.1155/2019/1974952 ◽

2019 ◽

Vol 2019 ◽

pp. 1-9

Author(s):

Xuan Zhang ◽

Taocheng Zhao ◽

Suchen Wu ◽

Feng Yao

Keyword(s):

Heat Transfer ◽

Surface Roughness ◽

Reynolds Number ◽

Nusselt Number ◽

Laminar Flow ◽

Cross Section ◽

Liquid Flow ◽

Flow And Heat Transfer ◽

Section Shape ◽

Poiseuille Number

Although roughness is negligible for laminar flow through tubes in classic fluid mechanics, the surface roughness may play an important role in microscale fluid flow due to the large ratio of surface area to volume. To further verify the influence of rough surfaces on microscale liquid flow and heat transfer, a performance test system of heat transfer and liquid flow was designed and built, and a series of experimental examinations are conducted, in which the microchannel material is stainless steel and the working medium is methanol. The results indicate that the surface roughness plays a significant role in the process of laminar flow and heat transfer in microchannels. In microchannels with roughness characteristics, the Poiseuille number of liquid laminar flow relies not only on the cross section shape of the rough microchannels but also on the Reynolds number of liquid flow. The Poiseuille number of liquid laminar flow in rough microchannels increases with increasing Reynolds number. In addition, the Nusselt number of liquid laminar heat transfer is related not only to the cross section shape of a rough microchannel but also to the Reynolds number of liquid flow, and the Nusselt number increases with increasing Reynolds number.

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Axisymmetric Stagnation—Point Flow and Heat Transfer of a Viscous Fluid on a Rotating Cylinder With Time-Dependent Angular Velocity and Uniform Transpiration

Journal of Fluids Engineering ◽

10.1115/1.2375132 ◽

2006 ◽

Vol 129 (1) ◽

pp. 106-115 ◽

Cited By ~ 22

Author(s):

A. B. Rahimi ◽

R. Saleh

Keyword(s):

Heat Transfer ◽

Heat Flux ◽

Reynolds Number ◽

Angular Velocity ◽

Stokes Equations ◽

Time Dependent ◽

Navier Stokes ◽

Navier Stokes Equations ◽

Flow And Heat Transfer ◽

Self Similar

The unsteady viscous flow and heat transfer in the vicinity of an axisymmetric stagnation point of an infinite rotating circular cylinder with transpiration U0 are investigated when the angular velocity and wall temperature or wall heat flux all vary arbitrarily with time. The free stream is steady and with a strain rate of Γ. An exact solution of the Navier-Stokes equations and energy equation is derived in this problem. A reduction of these equations is obtained by the use of appropriate transformations for the most general case when the transpiration rate is also time-dependent but results are presented only for uniform values of this quantity. The general self-similar solution is obtained when the angular velocity of the cylinder and its wall temperature or its wall heat flux vary as specified time-dependent functions. In particular, the cylinder may rotate with constant speed, with exponentially increasing/decreasing angular velocity, with harmonically varying rotation speed, or with accelerating/decelerating oscillatory angular speed. For self-similar flow, the surface temperature or its surface heat flux must have the same types of behavior as the cylinder motion. For completeness, sample semi-similar solutions of the unsteady Navier-Stokes equations have been obtained numerically using a finite-difference scheme. Some of these solutions are presented for special cases when the time-dependent rotation velocity of the cylinder is, for example, a step-function. All the solutions above are presented for Reynolds numbers, Re=Γa2∕2υ, ranging from 0.1 to 1000 for different values of Prandtl number and for selected values of dimensionless transpiration rate, S=U0∕Γa, where a is cylinder radius and υ is kinematic viscosity of the fluid. Dimensionless shear stresses corresponding to all the cases increase with the increase of Reynolds number and suction rate. The maximum value of the shear stress increases with increasing oscillation frequency and amplitude. An interesting result is obtained in which a cylinder rotating with certain exponential angular velocity function and at particular value of Reynolds number is azimuthally stress-free. Heat transfer is independent of cylinder rotation and its coefficient increases with the increasing suction rate, Reynolds number, and Prandtl number. Interesting means of cooling and heating processes of cylinder surface are obtained using different rates of transpiration.

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Numerical study on the effects of variable properties and nanoparticle diameter on nanofluid flow and heat transfer through micro-annulus

International Journal of Numerical Methods for Heat &amp Fluid Flow ◽

10.1108/hff-04-2016-0164 ◽

2017 ◽

Vol 27 (8) ◽

pp. 1851-1869 ◽

Cited By ~ 6

Author(s):

Morteza Heydari ◽

Hossein Shokouhmand

Keyword(s):

Heat Transfer ◽

Shear Stress ◽

Numerical Study ◽

Simple Algorithm ◽

Variable Properties ◽

Temperature Dependent ◽

Constant Property ◽

Content Type ◽

Nanoparticle Diameter ◽

Flow And Heat Transfer

Purpose The purpose of this paper is to evaluate differences between the results of constant property and variable property approaches in solving the problem of Al2O3-water nanofluid heat transfer in an annular microchannel. Also, the effect of nanoparticle diameter on flow and heat transfer characteristics is investigated. Design/methodology/approach Thermo-physical properties of the nanofluid including density, specific heat, viscosity and thermal conductivity are assumed to be temperature dependent. Governing equations are descritized using the finite volume method and solved by SIMPLE algorithm. Findings The results reveal that the constant property assumption is unable to predict the correct trend of variations along the microchannel for some of the characteristics, especially when the range of temperature change near the wall is considerable. In the fully developed region, constant property solution overestimates the values of shear stress near the walls of the microchannel. In addition, the values of Nusselt numbers are different for the two solutions. Furthermore, a decrease in wall’s shear stress has been observed as a result of increasing nanoparticle size. Originality/value This paper reflects that how the friction factor and heat transfer vary along the microchannel in temperature dependent modeling, which is not reflected in the results of constant property approach. To the best of the authors’ knowledge, there is no similar investigation of the effect of nanofluid variable properties with Pr=5 or in annular geometry.

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