Heat Transfer Enhancement by Acoustic Streaming in an Enclosure

2005 ◽  
Vol 127 (12) ◽  
pp. 1313-1321 ◽  
Author(s):  
Murat K. Aktas ◽  
Bakhtier Farouk ◽  
Yiqiang Lin
Keyword(s):  
Heat Transfer ◽  
Acoustic Waves ◽  
Numerical Solutions ◽  
Stokes Equations ◽  
Acoustic Streaming ◽  
Standing Waves ◽  
Side Wall ◽  
Temperature Fields ◽  
Vertical Side ◽  
Acoustic Standing Wave

Thermal convection in a differentially heated shallow enclosure due to acoustic excitations induced by the vibration of a vertical side wall is investigated numerically. The fully compressible form of the Navier-Stokes equations is considered and an explicit time-marching algorithm is used to track the acoustic waves. Numerical solutions are obtained by employing a highly accurate flux corrected transport algorithm. The frequency of the wall vibration is chosen such that an acoustic standing wave forms in the enclosure. The interaction of the acoustic standing waves and the fluid properties trigger steady secondary streaming flows in the enclosure. Simulations were also carried out for “off-design” vibration frequency where no standing waves were formed. The effects of steady second order acoustic streaming structures are found to be more significant than the main oscillatory flow field on the heat transfer rates. The model developed can be used for the analysis of flow and temperature fields driven by acoustic transducers and in the design of high performance resonators for acoustic compressors.

Oscillatory Flow Induced Developing Convection in a Shallow Enclosure: Effect of Sinusoidal Bottom Wall Temperature

2020 ◽  
Vol 142 (3) ◽  
Author(s):  
Saeid R. Angeneh ◽  
Murat K. Aktas
Keyword(s):  
Heat Transfer ◽  
Oscillatory Flow ◽  
Stokes Equations ◽  
Control Volume ◽  
Acoustic Streaming ◽  
Fluid Motion ◽  
Side Wall ◽  
Convective Transport ◽  
Bottom Wall ◽  
Mean Flow

Abstract The influence of hydrodynamically developing nonzero mean acoustic streaming motion on transient convective heat transfer in an air-filled rectangular enclosure is studied numerically. The enclosure is two-dimensional with sinusoidal bottom wall spatial temperature distribution. The oscillatory flow under relatively large Womersley number regime conditions is actuated by the periodic vibrations of the enclosure side wall. The side walls of the enclosure are adiabatic, while the top wall is isothermal. The compressible form of the Navier–Stokes equations is considered to predict the oscillatory- and time-averaged mean flow fields. A control-volume method based explicit computational scheme is used to simulate the convective transport in the enclosure. The longitudinal and the transverse temperature gradients strongly affect the flow structure in the enclosure. The mean fluid motion alters the heat transfer behavior compared to the pure conduction.

Natural convection in an enclosure having a vertical sidewall with time-varying temperature

1996 ◽  
Vol 329 ◽  
pp. 65-88 ◽  
Author(s):  
Ho Sang Kwak ◽  
Jae Min Hyun
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Numerical Solutions ◽  
Stokes Equations ◽  
Numerical Study ◽  
Temperature Fields ◽  
Navier Stokes ◽  
Time Varying ◽  
Vertical Sidewall ◽  
Boussinesq Fluid

A numerical study is performed for time-varying natural convection of an incompressible Boussinesq fluid in a sidewall-heated square cavity. The temperature at the cold sidewall Tc is constant, but at the hot sidewall a time-varying temperature condition is prescribed, $ T_H = \overline{T_H} + \Delta T^{\prime} \sin ft $. Comprehensive numerical solutions are found for the time-dependent Navier–Stokes equations. The numerical results are analysed in detail to show the existence of resonance, which is characterized by maximal amplification of the fluctuations of heat transfer in the interior. Plots of the dependence of the amplification of heat transfer fluctuations on the non-dimensional forcing frequency ω are presented. The failure of Kazmierczak & Chinoda (1992) to identify resonance is shown to be attributable to the limitations of the parameter values they used. The present results illustrate that resonance becomes more distinctive for large Ra and Pr ∼ 0(1). The physical mechanism of resonance is delineated by examining the evolution of oscillating components of flow and temperature fields. Specific comparisons are conducted for the resonance frequency ωr between the present results and several other previous predictions based on the scaling arguments.

Numerical Simulation of an Acoustically Driven Resonator With Internal Thin Parallel Plates

2007 ◽  
Author(s):  
Yiqiang Lin ◽  
Bakhtier Farouk
Keyword(s):  
Acoustic Waves ◽  
High Performance ◽  
Numerical Solutions ◽  
Stokes Equations ◽  
Heat Engine ◽  
Temperature Fields ◽  
Thin Plates ◽  
Parallel Plates ◽  
Left Wall ◽  
Thermoacoustic Refrigerators

Heat transfer and flow characteristics in a two-dimensional resonator with inside thin plates due to acoustic excitations are investigated numerically. The effect of the presence of the internal thin plates in the resonators is then studied. Such parallel plates (stacks) have been used in acoustic resonators for developing thermoacoustic refrigerators and thermoacoustic engines. A fully compressible form of the Navier-Stokes equations is considered for the numerical model and an explicit time-marching algorithm is used to track the acoustic waves and energy flux. Numerical solutions are obtained by employing a highly accurate flux corrected transport (FCT) algorithm. In the present model, the acoustic waves are induced by vibrations of the left wall, and the right wall is stationary. By neglecting the effect of side walls, the top and bottom boundary conditions are assumed to be symmetric. No simplifying assumption is made regarding the existence of the acoustic field. The interaction of acoustic standing waves with the internal parallel plates produces a temperature difference between the two ends which can be used for refrigeration or to do work (as a heat engine). The temperature differences are found to be significantly dependent on the location, length and gap of the internal plates. The model developed can be used for the analysis of flow and temperature fields driven by acoustic transducers, as well as in the design of high-performance resonators for thermoacoustic refrigerators and engines.

Jet-to-Plate Distance Effect on Heat Transfer From a Flat Plate to an Impinging Jet at Various Reynolds Numbers

2012 ◽  
Author(s):  
Patricia Streufert ◽  
Terry X. Yan ◽  
Mahdi G. Baygloo
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Reynolds Number ◽  
Flat Plate ◽  
Numerical Solutions ◽  
Stokes Equations ◽  
Local Heat Transfer ◽  
Reynolds Numbers ◽  
Air Jet ◽  
Plate Distance

Local turbulent convective heat transfer from a flat plate to a circular impinging air jet is numerically investigated. The jet-to-plate distance (L/D) effect on local heat transfer is the main focus of this study. The eddy viscosity V2F turbulence model is used with a nonuniform structured mesh. Reynolds-Averaged Navier-Stokes equations (RANS) and the energy equation are solved for axisymmetric, three-dimensional flow. The numerical solutions obtained are compared with published experimental data. Four jet-to-plate distances, (L/D = 2, 4, 6 and 10) and seven Reynolds numbers (Re = 7,000, 15,000, 23,000, 50,000, 70,000, 100,000 and 120,000) were parametrically studied. Local and average heat transfer results are analyzed and correlated with Reynolds number and the jet-to-plate distance. Results show that the numerical solutions matched experimental data best at low jet-to-plate distances and lower Reynolds numbers, decreasing in ability to accurately predict the heat transfer as jet-to-plate distance and Reynolds number was increased.

scholarly journals Flow and Heat Transfer at a Nonlinearly Shrinking Porous Sheet:The Case of Asymptotically Large Powerlaw Shrinking Rates

2013 ◽  
Vol 18 (3) ◽  
pp. 779-791 ◽  
Author(s):  
K.V. Prasad ◽  
K. Vajravelu ◽  
I. Pop
Keyword(s):  
Heat Transfer ◽  
Differential Equations ◽  
Power Law ◽  
Numerical Solutions ◽  
Skin Friction Coefficient ◽  
Temperature Fields ◽  
Shrinking Sheet ◽  
Arbitrary Power ◽  
Keller Box Method ◽  
Flow And Heat Transfer

Abstract The boundary layer flow and heat transfer of a viscous fluid over a nonlinear permeable shrinking sheet in a thermally stratified environment is considered. The sheet is assumed to shrink in its own plane with an arbitrary power-law velocity proportional to the distance from the stagnation point. The governing differential equations are first transformed into ordinary differential equations by introducing a new similarity transformation. This is different from the transform commonly used in the literature in that it permits numerical solutions even for asymptotically large values of the power-law index, m. The coupled non-linear boundary value problem is solved numerically by an implicit finite difference scheme known as the Keller- Box method. Numerical computations are performed for a wide variety of power-law parameters (1 < m < 100,000) so as to capture the effects of the thermally stratified environment on the velocity and temperature fields. The numerical solutions are presented through a number of graphs and tables. Numerical results for the skin-friction coefficient and the Nusselt number are tabulated for various values of the pertinent parameters.

The Uncertainties of Continuum-Based CFD Solvers to Perform Microscale Hot-Wire Anemometer Simulations in Flow Fields Close to Transitional Regime

2016 ◽  
Author(s):  
Masoud Darbandi ◽  
Mohammad Reza Ghorbani ◽  
Hamed Darbandi
Keyword(s):  
Heat Transfer ◽  
Numerical Solutions ◽  
Stokes Equations ◽  
Slip Flow ◽  
Convection Heat Transfer ◽  
Flow Fields ◽  
Transitional Flow ◽  
Hot Wire ◽  
Fixed Temperature ◽  
Cfd Method

In this study, we simulate the flow and heat transfer during hot-wire anemometry and investigate its thermal behavior and physics using the Computational Fluid Dynamics (CFD) tool. In this regard, we use the finite-volume method and solve the compressible Navier-Stokes equations numerically in slightly non-continuum flow fields. We do not use any slip flow model to include the transitional flow physics in our simulations. Using the CFD method, we simulate the flow over hot–wire and evaluate the uncertainty of CFD in thermal simulation of hot-wire in low transitional flow regimes. The domain sizes and the mesh distributions are carefully chosen to avoid boundary condition error appearances. Following the past researches, we do not take into account the conduction heat transfer passing through hot-wire mounting arms in our simulations. Imposing a fixed temperature condition at the face of hot-wire, we simulate the flow over and the heat transfer from hot-wire and calculate the convection heat transfer coefficient and the local Nusselt number values. To be sure of the accuracy of our CFD code, we simulate a number of similar test cases and compare our numerical solutions with the available numerical solutions and/or experimental data.

Three-Dimensional Laminar Natural Convection in a Vertical Air Slot With Hexagonal Honeycomb Core

1990 ◽  
Vol 112 (1) ◽  
pp. 130-136 ◽  
Author(s):  
Y. Asako ◽  
H. Nakamura ◽  
M. Faghri
Keyword(s):  
Natural Convection ◽  
Numerical Solutions ◽  
Transfer Problem ◽  
Three Dimensional ◽  
Convection Heat Transfer ◽  
Side Wall ◽  
Temperature Fields ◽  
Honeycomb Core ◽  
Wall Boundary Conditions ◽  
Laminar Natural Convection

Numerical solutions are obtained for a three-dimensional natural convection heat transfer problem in a vertical air slot with a thin hexagonal honeycomb core. The air slot is assumed to be of such dimensions that the velocity and temperature fields repeat themselves in successive enclosures. The numerical methodology is based on an algebraic coordinate transformation technique, which maps the complex cross section onto a rectangle, coupled with a calculation procedure for fully elliptic three-dimensional flows. The calculations are performed for the Rayleigh number in the range of 103 to 105, for a Prandtl number of 0.7, and for five values of the aspect ratio of the honeycomb enclosure. The average Nusselt number results for the case of a thin honeycomb core are compared with the previously obtained results for a thick honeycomb core with conduction and adiabatic side wall boundary conditions.

Numerical Simulation of the Cooling Process of Cubic Shells

2011 ◽  
Author(s):  
Manabu Okura ◽  
Kiyoaki Ono
Keyword(s):  
Heat Transfer ◽  
Stokes Equations ◽  
Temperature Fields ◽  
Numerical Code ◽  
Navier Stokes ◽  
Cooling Process ◽  
Air Velocity ◽  
Navier Stokes Equations ◽  
The Difference ◽  
The Heat Transfer Coefficient

In order to keep the environment in an air-conditioned room comfortable, it is important to anticipate the air velocity and temperature fields precisely. The numerical code, solving simultaneously the Navier-Stokes equations governing flow field inside and outside the room and the heat conduction equation applying to walls, are developed. The assumption that the heat transfer coefficient between the fluid and the surface of solids is not used. This code is applied to investigate the cooling process of a cubic shell. The computational results agree with the experimental results. We also investigated the same process of the cubic shells whose walls are internally or externally insulated. The difference of the amount of heat transfer will be discussed.

Inertial effect on gas squeeze film for large radius disc excited by standing waves with complex modal shapes

2019 ◽  
Vol 33 (24) ◽  
pp. 1950282 ◽  
Author(s):  
Yi Qiang Fan ◽  
M. Miyatake ◽  
S. Kawada ◽  
Bin Wei ◽  
S. Yoshimoto
Keyword(s):  
Reynolds Equation ◽  
Numerical Solutions ◽  
Stokes Equations ◽  
Standing Waves ◽  
Inertial Effect ◽  
Squeeze Film ◽  
Navier Stokes ◽  
Large Radius ◽  
Navier Stokes Equations ◽  
Sinusoidal Functions

In order to investigate the gas inertial effect on bearing capacity of acoustic levitation on condition of complex exciting shapes, a new kind of numerical model including inertial effect in cylindrical coordinates was proposed. The inertial terms in Navier–Stokes equations are packaged to derive modified Reynolds equations. The amplitudes of standing waves were tested by distance probe in experiment and film thickness equation were reconstructed by sum of the sinusoidal functions. The theoretical and experimental results implied that the inertial effect is strongly related to the exciting modal shapes. It is concluded that the proposal of modified Reynolds equation can provide more optimized numerical solutions to solve the problems about the deviation between theoretical and experimental data.

A Parametric Study on Fluid Flow and Heat Transfer in a Printed Circuit Heat Exchanger

2011 ◽  
Author(s):  
Sang-Moon Lee ◽  
Kwang-Yong Kim
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Numerical Solutions ◽  
Stokes Equations ◽  
Transport Model ◽  
Three Dimensional ◽  
Design Parameters ◽  
Printed Circuit ◽  
Reference Shape ◽  
Shear Stress Transport Model

Numerical analyses for pressure drop and heat transfer in the flow channels of a printed circuit heat exchanger have been performed numerically. Three-dimensional Reynolds-averaged Navier-Stokes equations have been solved in conjunction with the shear stress transport model as a turbulence closure. The numerical solutions are validated with the available experimental results of the reference shape. The effects of two design parameters, namely, the channel angle and the ellipse aspect ratio of the cold channel, on the heat transfer and the friction performance have been evaluated.

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