E. Salcedo

Bio: E. Salcedo is an academic researcher from National Autonomous University of Mexico. The author has contributed to research in topics: Combined forced and natural convection & Reynolds number. The author has an hindex of 4, co-authored 5 publications receiving 33 citations.

Experimental study on laminar flow over two confined isothermal cylinders in tandem during mixed convection

Abstract: An experimental investigation of laminar aiding and opposing mixed convection is carried out using particle image velocimetry (PIV) to assess the thermal effects on the wake of two isothermal cylinders of equal diameter in tandem array placed horizontally and confined inside a vertical closed-loop downward rectangular water channel. The buoyancy effect on the flow distributions are revealed for flow conditions with Reynolds number based on cylinder diameter of R e = 100 and 200, blockage ratio of B R = D / H = 0.3, aspect ratio of A R = W / D = 5, pitch-to-diameter ratio of σ = L / D = 3, and values of the buoyancy parameter (Richardson number) in the range −1 ≤ R i ≤ 3. In this work, the interference effects on the complex flow features are presented in the form of mean and instantaneous contours of velocity and vorticity. In addition, separation angles, wake structure, recirculation bubble lengths, time traces of velocity fluctuation, Strouhal number and vortex shedding modes of the two-cylinder system are obtained as a function of the Richardson number. In this arrangement, the results indicate that the effects of the Reynolds number are very pronounced, and that the vortex shedding patterns exhibit a strong dependence on R i . We also show the modulation effect of the channel walls on the three-dimensional flow under varying thermal buoyancy, and the results reported herein demonstrate how the flow structure, wake behavior and vortex shedding pattern are entirely different from that behind a single circular cylinder under wall confinement and thermal effects.

Numerical investigation of mixed convection heat transfer from two isothermal circular cylinders in tandem arrangement: buoyancy, spacing ratio, and confinement effects

Abstract: This paper presents a two-dimensional numerical study for mixed convection in a laminar cross-flow with a pair of stationary equal-sized isothermal cylinders in tandem arrangement confined in a channel. The governing equations are solved using the control volume method on a nonuniform orthogonal Cartesian grid, and the immersed boundary method is employed to identify the cylinders placed in the flow field. The numerical scheme is first validated against standard cases of symmetrically confined isothermal circular cylinders in plane channels, and grid convergence tests were also examined. The objective of the present study was to investigate the influence of buoyancy and the blockage ratio constraint on the flow and heat transfer characteristics of the immersed cylinder array. Using a fixed Reynolds number based on cylinder diameter of $$Re_{D} = 200$$ , a fixed value of the Prandtl number of $$Pr = 7$$ , and a blockage ratio of $$D/H = 0.2$$ , all possible flow regimes are considered by setting the longitudinal spacing ratio ( $$\sigma = L/D$$ ) between the cylinder axes to 2, 3, and 5 for values of the buoyancy parameter (Richardson number) in the range $$-1\le Ri\le 4$$ . The interference effects and complex flow features are presented in the form of mean and instantaneous velocity, vorticity, and temperature distributions. The results demonstrate how the buoyancy, spacing ratio, and wall confinement affect the wake structure and vortex dynamics. In addition, local and average heat transfer characteristics of both cylinders are comprehensively presented for a wide range in the parametric space.

Unsteady mixed convection heat transfer from two confined isothermal circular cylinders in tandem: Buoyancy and tube spacing effects

Abstract: In this work, two-dimensional numerical simulations are carried out to investigate the unsteady mixed convection heat transfer in a laminar cross-flow from two equal-sized isothermal in-line cylinders confined inside a vertical channel. The governing equations are solved using the vorticity-stream function formulation of the incompressible Navier–Stokes and energy equations using the control-volume method on a non-uniform orthogonal Cartesian grid. The numerical scheme is validated for the standard case of a symmetrically confined isothermal circular cylinder in a plane channel. Calculations are performed for flow conditions with Reynolds number of Re D = 200, a fixed value of the Prandtl number of Pr = 0.744, values of the buoyancy parameter (Richardson number) in the range − 1 ≤ R i ≤ 4 , and a blockage ratio of B R = D / H = 0.3 . All possible flow regimes are considered by setting the pitch-to-diameter ratios ( σ = L / D ) to 2, 3 and 5. The interference effects and complex flow features are presented in the form of mean and instantaneous velocity, vorticity and temperature distributions. In addition, separation angles, time traces of velocity fluctuation, Strouhal number, characteristic times of flow oscillation, phase-space relation between the longitudinal and transverse velocity signals, wake structure, and recirculation length behind each cylinder have been determined. Local and space-averaged Nusselt numbers for the upstream and downstream cylinders have also been obtained. The results reported herein demonstrate how the flow and heat transfer characteristics are significantly modified by the wall confinement, tube spacing, and thermal effects for a wide range in the parametric space.

Unsteady Mixed Convection from Two Isothermal Semicircular Cylinders in Tandem Arrangement

Abstract: In this chapter, two-dimensional mixed convection heat transfer in a laminar cross-flow from two heated isothermal semicircular cylinders in tandem arrangement with their curved surfaces facing the oncoming flow and confined in a channel is studied numerically. The governing equations are solved using the control-volume method on a nonuniform orthogonal Cartesian grid. Using the immersed-boundary method for fixed Reynolds number of ReD 1⁄4 uDD=υ 1⁄4 200, Prandtl number of Pr 1⁄4 7, blockage ratio of BR 1⁄4 D=H 1⁄4 0:2 and nondimensional pitch ratio of σ 1⁄4 L=D 1⁄4 3, the influence of buoyancy and the confinement effect are studied for Richardson numbers in the range −1 ≤Ri ≤ 1. Here, uD is the average longitudinal velocity based on the diameter of the semicylinder. The variation of the mean and instantaneous nondimensional velocity, vorticity and temperature distributions with Richardson number is presented along with the nondimensional oscillation frequencies (Strouhal numbers) and phase-space portraits of flow oscillation from each semicylinder. In addition, local and averaged Nusselt numbers over the surface of the semicylinders are also obtained. The results presented herein demonstrate how the buoyancy and wall confinement affect the wake structure, vortex dynamics and heat transfer characteristics.

Numerical investigation on buoyancy and inclination effects on transient mixed convection in a channel with discretely heated plane symmetric contraction-expansions

Abstract: In this work, transient mixed convection in a channel with discretely heated plane symmetric contraction-expansions at the mid-channel section emulating electronic components is studied numerically. The facing walls of the obstructions are isothermal, the other bounding walls of the constriction and the channel have non-adiabatic walls. The impact of changes in the cross section and their corresponding sensitivity to duct orientation on the overall flow and thermal evolution in space and time is analysed for fixed Prandtl number of P r = 7 , Reynolds number in the range 100 ≤ Re ≤ 1000, channel inclination of 0 ∘ ≤ Γ ≤ 90 ∘ , and different values of buoyancy strength (Richardson number). Results indicate that as the duct approaches the horizontal configuration, buoyancy strength reduces and higher threshold values of the Richardson number are required to induce instability. Also, depending on the parametric set, the flow and temperature distributions can experience an oscillatory behavior associated to variations in size of a complex vortical structure that occupies the spatial region near the partial blockage and that extends to downstream positions of the latter. Numerical predictions demonstrate how the blockage height affects the wake structure and vortex dynamics, and the effects of the Prandtl number and heat losses to the channel walls on the evolution of the flow and heat transfer response are presented and discussed in detail.

Numerical Heat Transfer And Fluid Flow

Abstract: Thank you for reading numerical heat transfer and fluid flow. Maybe you have knowledge that, people have search numerous times for their favorite books like this numerical heat transfer and fluid flow, but end up in infectious downloads. Rather than reading a good book with a cup of coffee in the afternoon, instead they cope with some malicious virus inside their computer. numerical heat transfer and fluid flow is available in our digital library an online access to it is set as public so you can get it instantly. Our books collection spans in multiple countries, allowing you to get the most less latency time to download any of our books like this one. Merely said, the numerical heat transfer and fluid flow is universally compatible with any devices to read.

On the relationship of Effective Reynolds number and Strouhal number for the laminar vortex shedding of a heated circular cylinder

Abstract: The laminar vortex shedding of airflow behind a circular cylinder with different heating temperatures was experimentally investigated with emphasis on the relationship of wake frequency and the Reynolds number. A new method to generate the two-dimensional parallel vortex shedding for the heated cylinder was developed and tested. An “effective Reynolds number” that employs a kinematic viscosity computed from an “effective temperature” is used to account for the temperature effects on the vortex shedding frequency. The present result shows that the frequency data could be successfully collapsed with the effective temperature computed by Teff=T∞+0.28(TW−T∞) for a wide range of cylinder temperatures, T∞ and TW being the free-stream temperature and cylinder surface temperature, respectively. Moreover, the relationship between Strouhal number and effective Reynolds number was found to be “universal.” The physical interpretation of Teff and the applicable region of the St–Reeff curve are discussed.

Constructal Design of triangular arrangements of square bluff bodies under forced convective turbulent flows

Abstract: Present numerical work consists on geometric evaluation of turbulent, transient, two-dimensional, incompressible and forced convective flows over triangular arrangements of square bluff bodies of size D employing Constructal Design. The main purpose is to evaluate the influence of the geometry of the arrangement over drag coefficient (CD) and Nusselt number (NuD), i.e., multiobjective problem. It is also investigated the influence of array configuration over fluid dynamic and thermal behavior of the flow. The problem has two constraints: cross-sectional area of bodies (3D2) and occupation area of the array (6D × 6D) and two degrees of freedom: SL/D and ST/D (ratios between longitudinal and transversal pitchs and size of the bodies). For all simulations, Reynolds and Prandtl numbers are constant (ReD = 22,000 and Pr = 0.71). Time-averaged conservation equations of mass, momentum and energy are solved with Finite Volumes Method. Closure of turbulence is solved with RANS SST – κ-ω modeling. Results showed a strong influence of design over fluid dynamic and thermal performance of the problem, as well as, multiplicity of scales and patterns of turbulent flows. Moreover, the optimal multi-objective configuration was the same reached for fluid dynamic purpose, showing the dominance of this purpose in the present investigation.

Influence of mixed convection laminar flows on the geometrical evaluation of a triangular arrangement of circular cylinders

Abstract: The present numerical study performs a geometrical evaluation of a triangular arrangement of circular cylinders subjected to transient, two-dimensional, incompressible, laminar, and aiding mixed convective flows by means of Constructal Design. It is investigated a multiobjective problem: maximize Nusselt number (NuD) and minimize drag coefficient (CD). In order to investigate the influence of buoyancy forces over design of the arrangement of cylinders five different Grashof numbers (GrD) are studied leading to different Richardson numbers: Ri = GrD/ReD2 = 0.1, 0.5, 1.0, 5.0 and 10.0. For all simulations, constant Reynolds and Prandtl numbers (ReD = 100 and Pr = 0.71) are considered. For geometric evaluation, the problem is subjected to two constraints (cross-sectional area of three cylinders and an occupation area for the arrangement) and two degrees of freedom (the ratio between the longitudinal pitch and cylinder diameter (SL/D) and ratio between the transversal pitch and cylinder diameter (ST/D)). In numerical simulations, the conservation equations of mass, momentum and energy are solved using Finite Volume Method (FVM). Results showed that buoyancy forces in mixed convective flows have strong influence over design of the studied cylinders arrangement. For instance, the effects of ST/D and SL/D over CD and NuD changed significantly for different Ri evaluated. Concerning the multiobjective evaluation, for Ri = 0.1 (forced convective flows) intermediate ratios of ST/D and SL/D, different from that achieved for the isolated purposes, conducted to the best multiobjetive performance, while for Ri = 10.0 (natural convective flows) the best shape is the same reached for the thermal objective, i.e., the multiobjective analysis for natural convective flow was guided by thermal purpose.

Numerical study of convective heat transfer from tube bank in cross flow using nanofluid

Abstract: In this paper, laminar convective heat transfer of Al2O3 -water nanofluid flow over tube banks under constant wall temperature conditions has been numerically investigated. The circular-tube banks with staggered arrangement are considered in this study. The governing equations have been solved using finite volume approach based on SIMPLE technique in body-fitted coordinates. The numerical simulations have been conducted for Reynolds number ranging from 100 to 600 with nanoparticles volume fraction ranging from 0 to 0.05. The effect of longitudinal pitch, transverse pitch and nanoparticle concentration on the streamwise and temperature contours, average Nusselt number, friction factor and thermal-hydraulic performance factor have been investigated and discussed. Results showed that the best performance is obtained at longitudinal pitch ratio of 1.5, transverse pitch ratio of 2.5 and nanoparticles volume fraction of 5% over the ranges of Reynolds number.