Effect of Substrate Microstructure on Thermocapillary Flow and Heat Transfer of Nanofluid Droplet on Heated Wall

2021 ◽  
Vol 33 (3) ◽  
Author(s):  
Yanni Jiang ◽  
Faxuan Chi ◽  
Qisheng Chen ◽  
Xiaoming Zhou
Keyword(s):  
Heat Transfer ◽  
Thermocapillary Flow ◽  
Heated Wall ◽  
Flow And Heat Transfer ◽  
Substrate Microstructure

Flow and Heat Transfer Characteristics of Supercritical Hydrocarbon Fuel in Mini Channels With Dimples

2017 ◽  
Vol 139 (12) ◽  
Author(s):  
Yu Feng ◽  
Jie Cao ◽  
Xin Li ◽  
Silong Zhang ◽  
Jiang Qin ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Hydrocarbon Fuel ◽  
Fuel Properties ◽  
Heated Wall ◽  
Cooling Channel ◽  
Heat Transfer Characteristics ◽  
Regenerative Cooling ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Cooling Passage

An idea of using dimples as heat transfer enhancement device in a regenerative cooling passage is proposed to extend the cooling limits for liquid-propellant rocket and scramjet. Numerical studies have been conducted to investigate the flow and heat transfer characteristics of supercritical hydrocarbon fuel in a rectangular cooling channel with dimples applied to the bottom wall. The numerical model is validated through experimental data and accounts for real fuel properties at supercritical pressures. The study shows that the dimples can significantly enhance the convective heat transfer and reduce the heated wall temperature. The average heat transfer rate of the dimpled channel is 1.64 times higher than that of its smooth counterpart while the pressure drop in the dimpled channel is only 1.33 times higher than that of the smooth channel. Furthermore, the thermal stratification in a regenerative cooling channel is alleviated by using dimples. Although heat transfer deterioration of supercritical fluid flow in the trans-critical region cannot be eliminated in the dimpled channel, it can be postponed and greatly weakened. The strong variations of fuel properties are responsible for the local acceleration of fuel and variation of heat transfer performance along the cooling channel.

scholarly journals Effect of magnetic field on the steady nanofluid flow past obstacle

2021 ◽  
Vol 22 (3) ◽  
pp. 535-542
Author(s):  
Yacine Khelili ◽  
Rafik Bouakkaz
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Laminar Flow ◽  
Hartmann Number ◽  
Volume Fraction ◽  
Transverse Magnetic ◽  
Heated Wall ◽  
Cylinder Wake ◽  
Flow And Heat Transfer ◽  
Model Transition

The fluid flow and heat transfer of a nanofluid past a circular cylinder in a rectangular duct under a strong transverse magnetic field is studied numerically using a quasitwo-dimensional model. Transition from laminar flow with separation to creeping laminar flow is determined as a function of Hartmann number and the volume fraction of nanoparticle, as are critical Hartmann number, and the heat transfer from the heated wall to the fluid. Downstream cross-stream mixing induced by the cylinder wake was found to increase heat transfer. The successive changes in the flow pattern are studied as a function of the Hartmann number. Suppression of vortex shedding occurs as the Hartmann number increases.

Direct numerical simulation of turbulent flow and heat transfer in a spatially developing turbulent boundary layer laden with particles

2018 ◽  
Vol 845 ◽  
pp. 417-461 ◽  
Author(s):  
Dong Li ◽  
Kun Luo ◽  
Jianren Fan
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Turbulent Flow ◽  
Solid Particles ◽  
Heated Wall ◽  
Wall Region ◽  
Flow And Heat Transfer ◽  
Particle Laden Flows ◽  
Near Wall

Direct numerical simulations of particle-laden flows in a spatially developing turbulent thermal boundary layer over an isothermally heated wall have been performed with realistic fully developed turbulent inflow boundary conditions. To the authors’ best knowledge, this is the first time the effects of inertial solid particles on turbulent flow and heat transfer in a flat-plate turbulent boundary layer have been investigated, using a two-way coupled Eulerian–Lagrangian method. Results indicate that the presence of particles increases the mean streamwise velocity and temperature gradients of the fluid in the near-wall region. As a result, the skin-friction drag and heat transfer are significantly enhanced in the particle-laden flows with respect to the single-phase flow. The near-wall sweep and ejection motions are suppressed by the particles and hence the Reynolds shear stress and wall-normal turbulent heat flux are attenuated, which leads to reductions in the production of the turbulent kinetic energy and temperature fluctuations. In addition, the coherence and spacing of the near-wall velocity and temperature streaky structures are distinctly increased, while the turbulent vortical structures appear to be disorganized under the effect of the particles. Moreover, the intensity of the streamwise vortices decreases monotonically with increasing particle inertia.

Enhanced Cooling of Electronic Components Using Fluid Flow Under High Adverse Pressure Gradient

2015 ◽  
Vol 7 (3) ◽  
Author(s):  
S. Ravishankar ◽  
K. Arul Prakash
Keyword(s):  
Heat Transfer ◽  
Adverse Pressure Gradient ◽  
Circuit Board ◽  
Heated Wall ◽  
Recirculation Region ◽  
Electronic Systems ◽  
Governing Equations ◽  
Galerkin Finite Element ◽  
Flow And Heat Transfer ◽  
Very High

Heat transfer in electronic systems is studied by simulating flow in a two pass channel with the divider representing a circuit board. Bypass holes are introduced on the circuit board to obtain detailed physical insights of the reversed flows in the second pass and thereby improve the cooling effect. The time-dependent governing equations are solved using an in-house code based on Streamline upwind/Petrov-Galerkin finite element method for Reynolds number ranging from 100 to 900. It is observed that stagnant zones are formed in the return path along the upper heated wall due to the formation of primary recirculation region on the divider plate. These stagnant zones are convected downstream by introducing bypass slots thereby enhancing the convective cooling. A parametric study on the location and number of bypass slots reveals that for a particular combination, the flow becomes unsteady thereby the heat transfer is increased. The presence of multiple slot jets also reduces the overall pressure drop required to drive the flow and heat transfer is very high at the point of impingement between the slots.

scholarly journals Analysis of the flow and heat transfer characteristics for MHD free convection in an enclosure with a heated obstacle

2011 ◽  
Vol 16 (1) ◽  
pp. 89-99 ◽  
Author(s):  
S. Parvin ◽  
R. Nasrin
Keyword(s):  
Heat Transfer ◽  
Hartmann Number ◽  
Heated Wall ◽  
Convection Flow ◽  
Heat Transfer Characteristics ◽  
Natural Convection Flow ◽  
Square Enclosure ◽  
Thermal Fields ◽  
Flow And Heat Transfer ◽  
Energy Equations

Finite element method based on Galerkin weighted Residual approach is used to solve two-dimensional governing mass, momentum and energy equations for steady state, natural convection flow in presence of magnetic field inside a square enclosure. The cavity consists of three adiabatic walls and one constantly heated wall. A uniformly heated circular solid body is located at the centre of the enclosure. The aim of this study is to describe the effects of MHD on the flow and thermal fields in presence of such heated obstacle. The investigations are conducted for different values of Rayleigh number (Ra) and Hartmann number (Ha). Various characteristics of streamlines, isotherms and heat transfer rate in terms of the average Nusselt number (Nu) are presented for different parameters. The effect of physical parameter (D) is also shown here. The results indicate that the flow pattern and temperature field are significantly dependent on the above mentioned parameters.

Computational simulations of buoyancy-influenced turbulent flow and heat transfer in a vertical plane passage

2004 ◽  
Vol 218 (11) ◽  
pp. 1385-1397 ◽  
Author(s):  
J Wang ◽  
J Li ◽  
S He ◽  
J D Jackson
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Turbulent Flow ◽  
Computational Study ◽  
Convective Heat Transfer Coefficient ◽  
Vertical Plane ◽  
Heated Wall ◽  
Computational Simulations ◽  
Variable Property ◽  
Flow And Heat Transfer

Computational simulations are reported of some recent experiments on turbulent variable-property mixed convection to air flowing upwards and downwards through a vertical plane passage, one wall of which was uniformly heated. In addition to heat transfer from that wall by convection, there was some radiative heat transfer to the opposite wall. In the experimental study, measurements were made of profiles of velocity and turbulence within the flow, and also local values of convective heat transfer coefficient were determined along the heated wall. The Reynolds number was varied from 44000 down to 7000 and the Grashof number from 3.0 × 108 to 9.0 × 09. To simulate the experiments by computational means, the governing equations for variable-property buoyancy-influenced two-dimensional turbulent flow and heat transfer in Reynolds-averaged form were solved using an elliptic formulation in conjunction with two well-known low-Reynolds-number k-e turbulence models. In this paper, results from the computational study are compared directly with experiment. In general, the observed effects of buoyancy on flow and heat transfer were satisfactorily reproduced but there were some clear discrepancies between the predictions and the experimental results, especially with downward flow under conditions where the influence of buoyancy was strong.

Effect of Axial Heat Conduction on Heat Transfer in Triangular Silicon Microchannels

2008 ◽  
Author(s):  
Yunhua Gan ◽  
Zeliang Yang ◽  
Cheng Yang ◽  
Shuangfeng Wang
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Conduction ◽  
Heated Wall ◽  
Microchannel Heat Sink ◽  
Physical Mechanisms ◽  
Flow And Heat Transfer ◽  
Axial Heat ◽  
Fundamental Physical ◽  
Axial Heat Conduction

In order to study the fundamental physical mechanisms of fluid flow and heat transfer in microchannels, many effects should be taken into account. The effect of axial heat conduction on heat transfer in microchannels is one of the hottest topics. Experimental investigation was carried out to analyze heat transfer characteristics of methanol flowing through microchannel heat sink, which consists of 10 parallel triangular microchannels. Experimental results show that the temperature distribution on the heated wall do not change linearly along the channel, which mainly caused by the axial heat conduction in the wall. The ratio of the power due to the axial heat flux to the Joule heating in the heater, and the axial heat conduction number were used to evaluate the heat conduction effect in the wall. Many factors play important roles in the axial heat conduction, including geometric configuration, material of the wall, and Reynolds number. The experimental study reveals that the axial heat conduction effect is gradually strengthened as the Reynolds number decreases.

scholarly journals A Computational Study on Fluid Flow and Heat Transfer Through a Rotating Curved Duct with Rectangular Cross Section

2021 ◽  
Vol 39 (4) ◽  
pp. 1213-1224
Author(s):  
Rabindra Nath Mondal ◽  
Mohammad Sanjeed Hasan ◽  
Mohammad S. Islam ◽  
Md. Zohurul Islam ◽  
Suvash C. Saha
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Numerical Study ◽  
Flow Patterns ◽  
Transitional Flow ◽  
Heated Wall ◽  
Gradient Force ◽  
Flow And Heat Transfer ◽  
Curved Duct ◽  
Steady Solutions

The understanding of fluid flow and heat transfer (HT) through a rotating curved duct (RCD) is important for different engineering applications. The available literature improved the understanding of the fluid flow and HT through a large-curvature rotating duct. However, the comprehensive knowledge of fluid flow and HT through an RCD with small curvature is little known. This numerical study aims to perform fluid flow characterization and HT through an RCD with curvature ratio 0.001. The spectral based numerical approach investigates the effects of rotation on fluid flow and HT for the Taylor number −1000≤Tr≤1500. A constant pressure gradient force, the Dean number Dn = 100, and a constant buoyancy force parameter, the Grashof number Gr = 500 are used for the numerical simulation. Fortran code is developed for the numerical computations and Tecplot software is used for the post-processing purpose. The numerical study investigates steady solutions and a structure of two-branches of steady solutions is obtained for positive rotation. The transient solution reports the transitional flow patterns and HT through the rotating duct, and two- to four-vortex solutions are observed. In case of negative rotation, time-dependent solutions show that the Coriolis force exhibits an opposite effect to that of the curvature so that the flow characteristics exhibit various flow instabilities. The numerical result shows that convective HT is increased with the increase of rotation and highly complex secondary flow patterns influence the overall HT from the heated wall to the fluid. To validate the numerical results, a comparison with the experimental data is provided, which shows that a good agreement is attained between the numerical and experimental investigations.

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