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Reynolds Number Range (reynold + number_range)
Selected AbstractsNumerical simulation of heat transfer and fluid flow over two rotating circular cylinders at low Reynolds numberHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 4 2010Nikolay Pavlovich Moshkin Abstract This paper presents a numerical investigation of the characteristics of two-dimensional heat transfer in a steady laminar flow around two rotating circular cylinders in a side-by-side arrangement. The simulation is validated by comparing our computational results for the large gap-spacing between cylinder surfaces with the available numerical and experimental data for a single cylinder. Numerical simulations were carried out for the Reynolds number range 10,Re ,40, for the Prandtl number range 0.7,Pr ,50, and for a variety of absolute rotational speeds (|,|,2.5) at different gap spacings. The study revealed that for the range of parameters considered the rate of heat transfer decreases with the increasing speed of rotation. An increase of the Prandtl number resulted in an increase in the average Nusselt number. The streamlines and isotherms are plotted for a numbers of cases to show the details of the velocity and thermal fields. © 2010 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20293 [source] Convective heat transfer and pressure drop of annular tubes with three different internal longitudinal finsHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 1 2008Lin Tian Abstract Pressure drop and heat transfer characteristics of air in three annular tubes with different internal longitudinal fins were investigated experimentally at uniform wall heat flux. The tested tubes have a double-pipe structure with the inner blocked tube as an insertion. Three different kinds of fins, plain rectangle fin, plain rectangle fin with periodical ridges and wave-like fin, were located peripherally in the annulus. The friction factor and Nusselt number can be corrected by a power-law correction in the Reynolds number range tested. It was found that the tube with periodical ridges on the plain fin or with wave-like fin could augment heat transfer; however, the pressure drop was increased simultaneously. In order to evaluate the comprehensive heat transfer characteristics of the tested tubes, two criteria for evaluating the comprehensive thermal performance of tested tubes were adopted. They are: 1) evaluating the comprehensive heat transfer performance under three conditions: identical mass flow, identical pumping power, and identical pressure drop; 2) the second law of thermodynamics, i.e., the entropy generation. According to the two different evaluating methods, it was found that the tube with wave-like fins provided the most excellent comprehensive heat transfer performance among the three tubes, especially when it was used under higher Reynolds number conditions. © 2007 Wiley Periodicals, Inc. Heat Trans Asian Res, 37(1): 29,40, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20186 [source] Effect of the plate thermal resistance on the heat transfer performance of a corrugated thin plate heat exchangerHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 3 2006Hiroshi Iwai Abstract Two-dimensional conjugate conduction/convection numerical simulations were carried out for flow and thermal fields in a unit model of a counter-flow-type corrugated thin plate heat exchanger core. The effects of the thermal resistance of the solid plate, namely the variation of the plate thickness and the difference of the plate material, on the heat exchanger performance were examined in the Reynolds number range of 100 Effect of tabs on impinging heat transferHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 7 2001Munehiko Hiwada Abstract The present work experimentally investigates the effect of vortex generators, in the form of small tabs projecting normally into the flow at the nozzle exit, on the fluid flow and heat transfer characteristics of an axisymmetric impinging air jet in the subcritical Reynolds number range. With this comes the expectation of a large eddy structure variation and the possibility of active control. Local heat transfer and static pressure were measured on a target plate for a round air jet issuing from a circular nozzle with rectangular tabs whose numbers and lengths changed at a constant nozzle-to-plate gap (L/d = 8) and jet Reynolds number (Re = 34,000). The main results are the following: When two tabs were set at the exit of the circular nozzle, Cpw and Nu profiles flatten in the direction of the tab setting. In the case of three tabs, however, among both Cpw and Nu profiles a concentric profile is found, as well as in the case without any tabs. © 2001 Scripta Technica, Heat Trans Asian Res, 30(7): 561,570, 2001 [source] A two-step Taylor-characteristic-based Galerkin method for incompressible flows and its application to flow over triangular cylinder with different incidence anglesINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 11 2010Yan Bao Abstract An alternative characteristic-based scheme, the two-step Taylor-characteristic-based Galerkin method is developed based on the introduction of multi-step temporal Taylor series expansion up to second order along the characteristic of the momentum equation. Contrary to the classical characteristic-based split (CBS) method, the current characteristic-based method does not require splitting the momentum equation, and segregate the calculation of the pressure from that of the velocity by using the momentum,pressure Poisson equation method. Some benchmark problems are used to examine the effectiveness of the proposed algorithm and to compare with the original CBS method, and the results show that the proposed method has preferable accuracy with less numerical dissipation. We further applied the method to the numerical simulation of flow around equilateral triangular cylinder with different incidence angles in free stream. In this numerical investigation, the flow simulations are carried out in the low Reynolds number range. Instantaneous streamlines around the cylinder are used as a means to visualize the wake region behind, and they clearly show the flow pattern around the cylinder in time. The influence of incidence angle on flow characteristic parameters such as Strouhal number, Drag and Lift coefficients are discussed quantitatively. Copyright © 2009 John Wiley & Sons, Ltd. [source] Transition from vortex to wall driven turbulence production in the Taylor,Couette system with a rotating inner cylinderINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 3 2002W. M. J. Batten Abstract Axisymmetrically stable turbulent Taylor vortices between two concentric cylinders are studied with respect to the transition from vortex to wall driven turbulent production. The outer cylinder is stationary and the inner cylinder rotates. A low Reynolds number turbulence model using the k - , formulation, facilitates an analysis of the velocity gradients in the Taylor,Couette flow. For a fixed inner radius, three radius ratios 0.734, 0.941 and 0.985 are employed to identify the Reynolds number range at which this transition occurs. At relatively low Reynolds numbers, turbulent production is shown to be dominated by the outflowing boundary of the Taylor vortex. As the Reynolds number increases, shear driven turbulence (due to the rotating cylinder) becomes the dominating factor. For relatively small gaps turbulent flow is shown to occur at Taylor numbers lower than previously reported. Copyright © 2002 John Wiley & Sons, Ltd. [source] Numerical simulation of the unsteady flow over an elliptic cylinder at different orientationsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 8 2001H. M. Badr Abstract A numerical method is developed for investigating the two-dimensional unsteady viscous flow over an inclined elliptic cylinder placed in a uniform stream of infinite extent. The direction of the free stream is normal to the cylinder axis and the flow field unsteadiness arises from two effects, the first is due to the flow field development following the start of the motion and the second is due to vortex shedding in the wake region. The time-dependent flow is governed by the full conservation equations of mass and momentum with no boundary layer approximations. The parameters involved are the cylinder axis ratio, Reynolds number and the angle of attack. The investigation covers a Reynolds number range up to 5000. The minor,major axis ratio of the elliptic cylinder ranges between 0.5 and 0.6, and the angle of attack ranges between 0° and 90°. A series truncation method based on Fourier series is used to reduce the governing Navier,Stokes equations to two coupled infinite sets of second-order differential equations. These equations are approximated by retaining only a finite number of terms and are then solved by approximating the derivatives using central differences. The results reveal an unusual phenomenon of negative lift occurring shortly after the start of motion. Various comparisons are made with previous theoretical and experimental results, including flow visualizations, to validate the solution methodology. Copyright © 2001 John Wiley & Sons, Ltd. [source] CFD Simulation of Inlet Design Effect on Deoiling Hydrocyclone Separation EfficiencyCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 12 2009S. Noroozi Abstract An Eulerian-Eulerian three-dimensional CFD model was developed to study the effect of different inlet designs on deoiling hydrocyclone separation efficiency. Reynolds averaged Navier Stokes and continuity equations were applied to solve steady turbulent flow through the cyclone with the Reynolds stress model. In addition, the modified drag correlation for liquid-liquid emulsion with respect to the Reynolds number range and viscosity ratio of two phases was used and the simulation results were compared with those predicted by the Schiller-Naumann correlation. Pressure profile, tangential and axial velocities and separation efficiency of the deoiling hydrocyclone were calculated for four different inlet designs and compared with the standard design. The simulation results for the standard design demonstrate an acceptable agreement with reported experimental data. The results show that all new four inlet designs offer higher efficiencies compared to the standard design. The difference between the efficiency of the LLHC, of the new inlets and the standard design can be improved by increasing the inlet velocity. Furthermore, the simulations show that the separation efficiency can be improved by about 10 % when using a helical form of inlet. [source]
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