Author: Paul D. HancockPublisher:
ISBN:
Category :
Languages : en
Pages : 222
Book Description
Numerical Simulation of Laminar Flow and Heat Transfer in Two- Dimensional Channels
Numerical Simulation of Fluid Flow and Heat/Mass Transfer Processes
Author: N.C. MarkatosPublisher: Springer Science & Business Media
ISBN: 3642827810
Category : Technology & Engineering
Languages : en
Pages : 477
Book Description
Computational fluid flow is not an easy subject. Not only is the mathematical representation of physico-chemical hydrodynamics complex, but the accurate numerical solution of the resulting equations has challenged many numerate scientists and engineers over the past two decades. The modelling of physical phenomena and testing of new numerical schemes has been aided in the last 10 years or so by a number of basic fluid flow programs (MAC, TEACH, 2-E-FIX, GENMIX, etc). However, in 1981 a program (perhaps more precisely, a software product) called PHOENICS was released that was then (and still remains) arguably, the most powerful computational tool in the whole area of endeavour surrounding fluid dynamics. The aim of PHOENICS is to provide a framework for the modelling of complex processes involving fluid flow, heat transfer and chemical reactions. PHOENICS has now been is use for four years by a wide range of users across the world. It was thus perceived as useful to provide a forum for PHOENICS users to share their experiences in trying to address a wide range of problems. So it was that the First International PHOENICS Users Conference was conceived and planned for September 1985. The location, at the Dartford Campus of Thames Polytechnic, in the event, proved to be an ideal site, encouraging substantial interaction between the participants.
Numerical Simulations of Laminar, Transitional, and Turbulent Flow and Heat Transfer in Continuous- and Interrupted-plate Channels
Author: Kelechi EzejiPublisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
"The long-term goal of this research is to contribute to the development of mathematical models and numerical solution methods for use as cost-effective tools in procedures for designing the next generation of compact and ultra-compact heat exchangers (core heat transfer area density exceeding 700 m^2/m^3 and 3000 m^2/m^3, respectively). Such heat exchangers are expected to play a major role in ongoing worldwide efforts to propose novel energy conversion systems. The desire to participate in such efforts is the main motivation for this work. Attention in this work was focused on rectangular offset strip-fin plate-fin core configurations. Over the last 50 years, there have been many efforts to increase the compactness of such cores. However, increasing compactness reduces the hydraulic diameter and (hence) the Reynolds number, for the same average velocity, which can lead to turbulent-to-laminar transition. These consequences of increasing compactness bring up the issue of its effect on the rate of heat transfer for a fixed pumping power. The rectangular offset strip-fin plate-fin configuration causes starting, interrupting, and restarting of both velocity and thermal boundary layers, and also possible unsteadiness and vortex shedding; and these thermofluid features bring up the issue of maximizing heat transfer for specified heat transfer surface area and fixed pumping power.The main goal of this research was to contribute to the resolution of the first of the aforementioned two issues, in a highly cost-effective manner. Thus, fins of negligible thickness and flow passages of large cross-sectional aspect ratio were assumed, and attention was limited to steady two-dimensional fluid flow and heat transfer phenomena. Air was the fluid of choice, and it was assumed that its thermophysical properties remained essentially constant. Furthermore, the Eckert number was much less than one in the problems considered here, so viscous dissipation could be ignored.Elliptic and parabolic mathematical models of developing fluid flow and heat transfer in continuous parallel-plate channels and arrays of regular staggered plates were considered. Three different low-Reynolds-number turbulence models (all capable of predicting turbulent-laminar transition with reduction in Reynolds number) were selected for comparative assessment. These mathematical models were solved using two-dimensional elliptic (2DE) and parabolic (2DP) finite volume methods (FVMs): the 2DE FVM was an adapted version of an in-house code; the 2DP FVM was specially formulated and implemented for this work, retaining the momentum equation in the direction transverse to the main flow (a novel feature of the proposed method). Mathematical models of fully developed fluid flow and heat transfer in pipes and parallel-plate channels were also considered and solved using one-dimensional FVMs. The results were compared to those yielded by available empirical correlations and also experimental data. Finally, one of the three low-Reynolds-number turbulence models and the 2DP FVM were used to simulate fluid flow and heat transfer in three actual rectangular offset strip-fin plate-fin cores of compact heat exchangers.For fully developed flows, all three low-Reynolds-number turbulence models considered in this work gave results that showed excellent agreement with those yielded by available empirical correlations and also experimental data. For developing fluid flow and heat transfer, the 2DP results compared very well with the 2DE results; however, the 2DP FVM executed 700 to 12,000 times faster than the 2DE FVM for comparable computational grids. In simulations of developing fluid flow and heat transfer in continuous-plate channels and regular arrays of staggered plates, only one of the three low-Reynolds-number turbulence models gave good results. The details of the models, numerical methods, and results, and also some recommendations, are presented and discussed in this thesis." --
Numerical Simulation of 2-Dlaminar Flow, Heat Generation and Forced Convection from Rectangular Blocks in a Narrow Channel
Author: İbrahim ÖzkolPublisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
In this study, a directional-implicit Computational Fluid Dynamics (CFD)finite difference code is developed so as to simulate the direct and indirect heat removal through conduction and convection processes from the rectangular blocks attached to the lower surface of a narrow- channel geometry. Two dimensional, unsteady, incompressible, laminar form of the Navier -Stokes (N-S) equations are considered. L sing the stream function-vorticity approach, they are discretized via finite difference technique, under the assumption of the Taylor series expansions. The discretized equations than reduced to a three-banded form of a matrix equality ready to be used conjugate solution formulation. In the same manner, two dimensional unsteady' energy· equation discretized with the source term included into three-banded matrix form. Tw-o field equations are solved numerically for various channel-rectangular block geometries so as to study the steady--state heat transfer characteristics inside channel with possible heat generation inside the blocks. It is shown that the numerical model is capable of simulating the main features of the flow- field. Detailed benchmarks of the present numerical model is attempted so as to validate the devoloped algorithm. The streamvise extension of the recirculation zone behind the rectangular block which is a function of the Reynolds number is very well simulated. Furthermore, it was shown that the heat transfer characteritics of the zone agrees well with the experinıental and theoretical observations in the literature. Prepared algorithm is a highly' stable algorithm but show'ing slow convergence to a steady state value. Conjugate solution property of the present approach enables one to study complex thermal characteristics of fluid-solid and solid-solid interactions. Beside the classical boundary conditions of the thermal field, the problem domain is further complicated by the presence of discrete heat sources in the rectangular blocks in form of the infinite small heat generating sheet. Heat generatedat various transfer positions are convected by the fluid downstream. The near wall flow temperature and the Nusselt number distributions over the surface depict the most features of the complex fluid-solid interaction. The steady state temperature inside the blocks and in the substrate are found to be functions of the flow Reynolds number. Prandtl number, heat source position and substrate bottom surface temperature. Due to the heat generation the flow is heated well above its inlet value. This causes continous heat flow from fluid to the lower plate in the recirculating regions of the rectangular blocks and in the cavities where there are more than one obstacle. The present model can simulate the chip cooling problems for integrated circuit components, i.e, chips, on a horizontal printed curcuit board which is containing heat generatin; rectangular blocks attached to a single layer substrate. Results consistency with other studies, which are reported in literature, is discussed.
Numerical Methods in Laminar and Turbulent Flow
Author: Numerical Simulations of Three-dimensional Laminar Flow Over a Backward Facing Step
Author: Modern Developments in Numerical Simulation of Flow and Heat Transfer
Author: James L. S. ChenPublisher:
ISBN:
Category : Science
Languages : en
Pages : 112
Book Description
Finite Analytic Numerical Simulations in Two Dimensional Laminar Or Turbulent Fluid Flow and Combined Modes of Heat Transfer
Author: Yousef Sa'ad HaikSimulation of Three-dimensional Laminar Flow and Heat Transfer in an Array of Parallel Microchannels
Author: Justin Dale MlcakPublisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
Heat transfer and fluid flow are studied numerically for a repeating microchannel array with water as the circulating fluid. Generalized transport equations are discretized and solved in three dimensions for velocities, pressure, and temperature. The SIMPLE algorithm is used to link pressure and velocity fields, and a thermally repeated boundary condition is applied along the repeating direction to model the repeating nature of the geometry. The computational domain includes solid silicon and fluid regions. The fluid region consists of a microchannel with a hydraulic diameter of 85.58[mu]m. Independent parameters that were varied in this study are channel aspect ratio and Reynolds number. The aspect ratios range from 0.10 to 1.0 and Reynolds number ranges from 50 to 400. A constant heat flux of 90 W/cm2 is applied to the northern face of the computational domain, which simulates thermal energy generation from an integrated circuit. A simplified model is validated against analytical fully developed flow results and a grid independence study is performed for the complete model. The numerical results for apparent friction coefficient and convective thermal resistance at the channel inlet and exit for the 0.317 aspect ratio are compared with the experimental data. The numerical results closely match the experimental data. This close matching lends credibility to this method for predicting flows and temperatures of water and the silicon substrate in microchannels. Apparent friction coefficients linearly increase with Reynolds number, which is explained by increased entry length for higher Reynolds number flows. The mean temperature of water in the microchannels also linearly increases with channel length after a short thermal entry region. Inlet and outlet thermal resistance values monotonically decrease with increasing Reynolds number and increase with increasing aspect ratio. Thermal and friction coefficient results for large aspect ratios (1 and 0.75) do not differ significantly, but results for small aspect ratios (0.1 and 0.25) notably differ from results of other aspect ratios.
Applications of Mathematical Heat Transfer and Fluid Flow Models in Engineering and Medicine
Author: Abram S. DorfmanPublisher: John Wiley & Sons
ISBN: 1119320569
Category : Technology & Engineering
Languages : en
Pages : 458
Book Description
Applications of mathematical heat transfer and fluid flow models in engineering and medicine Abram S. Dorfman, University of Michigan, USA Engineering and medical applications of cutting-edge heat and flow models This book presents innovative efficient methods in fluid flow and heat transfer developed and widely used over the last fifty years. The analysis is focused on mathematical models which are an essential part of any research effort as they demonstrate the validity of the results obtained. The universality of mathematics allows consideration of engineering and biological problems from one point of view using similar models. In this book, the current situation of applications of modern mathematical models is outlined in three parts. Part I offers in depth coverage of the applications of contemporary conjugate heat transfer models in various industrial and technological processes, from aerospace and nuclear reactors to drying and food processing. In Part II the theory and application of two recently developed models in fluid flow are considered: the similar conjugate model for simulation of biological systems, including flows in human organs, and applications of the latest developments in turbulence simulation by direct solution of Navier-Stokes equations, including flows around aircraft. Part III proposes fundamentals of laminar and turbulent flows and applied mathematics methods. The discussion is complimented by 365 examples selected from a list of 448 cited papers, 239 exercises and 136 commentaries. Key features: Peristaltic flows in normal and pathologic human organs. Modeling flows around aircraft at high Reynolds numbers. Special mathematical exercises allow the reader to complete expressions derivation following directions from the text. Procedure for preliminary choice between conjugate and common simple methods for particular problem solutions. Criterions of conjugation, definition of semi-conjugate solutions. This book is an ideal reference for graduate and post-graduate students and engineers.