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Laminar film condensation heat transfer on a vertical, non-isothermal, semi-infinite plate  [PDF]
Jian-Jun Shu
Physics , 2014, DOI: 10.1007/s13369-012-0272-8
Abstract: This paper gives similarity transformations for laminar film condensation on a vertical flat plate with variable temperature distribution and finds analytical solutions for arbitrary Prandtl numbers and condensation rates. The work contrasts with Sparrow and Gregg's assertion that wall temperature variation does not permit similarity solutions. To resolve the long debatable issue regarding heat transfer of non-isothermal case, some useful formulas are obtained, including significant correlations for varying Prandtl numbers. Results are compared with the available experimental data.
Velocity Boundary Layer Analysis of a Flat Plate Heat Exchanger in Laminar Flow: A Case Study
M. Mirdrikvand,B. Roozbehani,S. I. Moqadam,A. C. Roshan
Engineering, Technology & Applied Science Research , 2012,
Abstract: In this article, a behavioral analysis of velocity boundary layer in a flat plate heat exchanger in laminar flow condition through CFD simulation using FLUENT software is done. The main objective of this study is to determine the velocity vectors between the flat plates of the heat exchanger. In addition, wake occurrence, differences of velocity at different surfaces between plates, angles of velocity vectors and the effect of wake phenomenon on the shear stresses exerted on the plates are discussed in detail. The study graphically illustrates results based on fluid’s behavior by a 3D and 2D simulation with air and water as cold and hot streams that affect plate’s situation and its hydro dynamical operations. Consequently, some important design features regarding wake point occurrence and pressure loss are investigated. In addition, eddy current and reverse flows in the wake area and the angles of the velocity vectors are described.
Second Law Analysis of a non-Newtonian Laminar Falling Liquid Film Along an Inclined Heated Plate  [PDF]
Rama Subba Reddy Gorla,David M. Pratt
Entropy , 2007, DOI: 10.3390/e9010030
Abstract: The second law analysis of heat transfer of a non-Newtonian, laminar fallingliquid film along an inclined heated plate is investigated. The upper surface of the liquidfilm is considered free and adiabatic. Velocity and temperature profiles are obtainedanalytically and used to compute the entropy generation number (N s), irreversibility ratio (Φ) and the Bejan number (Be) for several values of the viscous dissipation parameter(Br -1), viscosity index (n) and the dimensionless axial distance (X). The Bejan numberincreases in the transverse direction and decreases as the viscous dissipation parameter(BrΩ -1) increases. The numerical results show that the Bejan number decreases as theviscous dissipation parameter (BrΩ -1), Peclet number (Pe) and the viscosity index (n)increase.
Primitive variable approach to calculate separation point in laminar boundary layer along a flat plate  [PDF]
Md. Tanvir Rahman Faisal,A. K. M. S. Islam
Journal of Engineering and Applied Sciences , 2006,
Abstract: Primitive variable approach has been used to model the Navier Stokes Equation. This is the method by which one can see what is going on in boundary layer. In the present work that primitive variable approach is considered to calculate incompressible, steady state laminar boundary layer along a flat plate with different flow conditions. This approach uses implicit finite difference method which consists of replacing the partial derivatives with respect to flow direction by finite differences. As a result the partial differential equations are approximated by ordinary differential equations. This method is capable of solving any flow problem for which the boundary layer equations remain valid. This implicit finite difference scheme is advantageous comparing to explicit finite difference scheme because the results are unconditionally stable regardless the step size. In the present work, the method is used to compute accurately the separation points of flow.
Visualization of a Laminar Necklace Vortex System in Front of a Vertical Rectangular Plate on a Ground Wall  [PDF]
Yasuhiro Nakahara, Hidemi Yamada
Journal of Flow Control, Measurement & Visualization (JFCMV) , 2015, DOI: 10.4236/jfcmv.2015.32008
Abstract: Various properties of a necklace vortex system formed around a rectangular plate standing vertically on a flat ground wall were investigated by visualizations produced by injecting fluorescent dye into a water channel flow. As a result, it was found that the necklace vortex pattern had three steady systems depending on the Reynolds number Reh, the relative height h/δ of the rectangular plate compared with the laminar boundary layer thickness and the aspect ratio w/h. As it is expected that the aspect ratio of the rectangular plate will typify the projected area configuration of various three-dimensional bodies, the aspect ratio is varied widely from 0.5 to 7.0. The transitional boundaries of Reh and h/δ in the 2-vortex, 4-vortex and 6-vortex systems for each aspect ratio decreased when w/h < 3.0, and increased when w/h ≥ 3.0 as w/h increased. The x-direction length of the main vortex position XV1/h was almost constant when w/h < 3.0, and decreased when w/h ≥ 3.0 as Reh increased. Then, the separation length r1/h increased when w/h < 3.0 and Reh < 1000, and became almost constant when w/h ≥ 3.0 and Reh ≥ 1000 as w/h and Reh increased. Moreover, the increase of r1/h is notably rapid when w/h < 3.0.
Measurements of the Rate Capability of Various Resistive Plate Chambers  [PDF]
M. Affatigato,U. Akgun,B. Bilki,F. Corriveau,B. Freund,N. Johnson,C. Neubueser,Y. Onel,J. Repond,L. Xia
Physics , 2015,
Abstract: Resistive Plate Chambers (RPCs) exhibit a significant loss of efficiency for the detection of particles, when subjected to high particle fluxes. This rate limitation is related to the usually high resistivity of the resistive plates used in their construction. This paper reports on measurements of the performance of three different glass RPC designs featuring a different total resistance of the resistive plates. The measurements were performed with 120 GeV protons at varying beam intensities
Effect of Magnetic Field on Entropy Generation Due to Laminar Forced Convection Past a Horizontal Flat Plate  [PDF]
Mohammed Q. Al-Odat,Renhe A. Damseh,Moh\'d A. Al-Nimr
Entropy , 2004, DOI: 10.3390/e6030293
Abstract: Magnetic field effect on local entropy generation due to steady two-dimensional laminar forced convection flow past a horizontal plate was numerically investigated. This study was focused on the entropy generation characteristics and its dependency on various dimensionless parameters. The effect of various dimensionless parameters, such as Hartmann number (Ha), Eckert number (Ec), Prandtl number (Pr), Joule heating parameter (R) and the free stream temperature parameter (θ∞) on the entropy generation characteristics is analyzed. The dimensionless governing equations in Cartesian coordinate were solved by an implicit finite difference technique. The solutions were carried out for Ha2=0.5-3, Ec=0.01-0.05, Pr=1-5 and θ∞=1.1-2.5. It was found that, the entropy generation increased with increasing Ha, Ec and R. While, increasing the free stream temperature parameter, and Prandtl number tend to decrease the local entropy generation.
Laminar Horseshoe Vortices Upstream of a Short Cylinder Normal to a Flat Plate
Rodríguez y Domínguez, Marcos Matthaeus;Romero-Méndez, Ricardo;De Lange, Dirk Frederik;Hernández-Guerrero, Abel;
Ingeniería mecánica, tecnología y desarrollo , 2011,
Abstract: a flow visualization experiment was performed in order to characterize the laminar horseshoe vortex system that appears upstream of the ?unction of a short cylinder and a single flat plate parallel to the flow direction. the experiments were performed in a water tunnel and the technique used for flow visualization was laser illumination of seeded particles whose traces were captured using long exposure photograph. geometrical and flow parameters, such as reynolds number and height-to-diameter ratio of the cylinders, are varied during the experiments and the appearance of the flow regimes is determined as a function of these parameters. the behavior of vortex systems is analyzed. additional to the types of horseshoe vortex systems reported in investigations with tall cylinders, a chaotic type of vortex system was observed for this case. this chaotic horseshoe vortex system occurs only in short cylinders and for sufficiently high reynolds numbers. information about the frequency of appearance of periodic vortex systems is presented, from which we could define a cylinder height beyond which the flow behavior becomes independent of height. information of the position of the main vortex closer to the cylinder and the position of the stagnation point over the cylinder is also reported.
Comparison of several models of the laminar/turbulent transition  [cached]
Fürst V.,Straka J.,P?íhoda P.,?imurda J.
EPJ Web of Conferences , 2013, DOI: 10.1051/epjconf/20134501032
Abstract: The contribution deals with modelling of the laminar/turbulent transition using several transition models. Transition models of various types were tested: a) the model with the algebraic equation for the intermittency coefficient according to Straka and P íhoda; b) the three-equation transition model with the transport equation for the energy of non-turbulent fluctuations proposed by Walters and Cokljat; c) the γ-Reθ model with the transport equation forthe intermittency coefficient of Langtry and Menter. The transition models were compared by means of test cases covering both flat-plate boundary-layer flows with various free stream turbulence and the flow over an airfoil including the effect of foregoing wake on the transition. The agreement of numerical results with experimental data is in all cases quite satisfactory.
Mixed-convection laminar film condensation on a semi-infinite vertical plate  [PDF]
Jian-Jun Shu,Graham Wilks
Physics , 2014, DOI: 10.1017/S0022112095003661
Abstract: A comprehensive study of the problem of laminar film condensation with both a gravitational type body force and a moving vapour concurrent and parallel to the surface has been presented here. It demonstrates where both the body force and vapour velocity are significant through a comprehensive numerical solution obtained by a modified Keller box method. Important parameters governing condensation and heat transfer of pure vapour are determined. A perturbation analysis is applied in the leading edge and downstream regimes. The thin film approximations for the both regimes are obtained and compared with exact numerical solutions.
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