Numerical Simulations of Laminar, Transitional, and Turbulent Flow and Heat Transfer in Continuous- and Interrupted-plate Channels PDF Download
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Author: Kelechi Ezeji Publisher: 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." --
Author: Kelechi Ezeji Publisher: 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." --
Author: Siegfried Wagner Publisher: Springer Science & Business Media ISBN: 9783540404903 Category : Science Languages : en Pages : 350
Book Description
Methodic investigations of laminar-turbulent transition in wall-bounded she ar flows under controlled conditions are essential for untangling the various complex phenomena of the transition process occurring in flows at practical conditions. They allow understanding of the instability processes of the la minar flow, and thus enable the development of tools for flow control. On the one hand the laminar flow regime can be extended by delaying transition to reduce viscous drag, and on the other hand large-scale flow disturbances or transition can be forced in order to enhance momentum and mass ex change. Thus flow separation can be prevented, or mixing of fuel and air in combustion engines enhanced, for instance. The "DFG Verbund-Schwerpunktprogramm Transition" - a cooperative priority research program of universities, research establishments and indu stry in Germany - has been launched in April 1996 with the aim to explore transition by a coordinated use, development and validation of advanced experimental techniques and theoretical/numerical simulation methods, bin ding together all the appropriate resources available in Germany. At the very beginning of the six-year research period specifically selected test problems were to be investigated by various theoretical and experimental methods to identify and possibly rule out inadequate numerical or experimental methods. With respect to experiments it was planned to use multi-sensor-surface measuring techniques, the infrared measuring technique, and particle image velocimetry (PlV) in addition to hot-wire techniques to get instantaneous images of flows in sections, on surfaces, or within the complete flow field.
Author: Chia-Ch'iao Lin Publisher: Princeton University Press ISBN: 1400879418 Category : Science Languages : en Pages : 570
Book Description
Volume V of the High Speed Aerodynamics and Jet Propulsion series. Topics include transition from laminar to turbulent flow; turbulent flow; statistical theories of turbulence; conduction of heat; convective heat transfer and friction in flow of liquids; convective heat transfer in gases; cooling by protective fluid films; physical basis of thermal radiation; and engineering calculations of radiant heat exchange. Originally published in 1959. The Princeton Legacy Library uses the latest print-on-demand technology to again make available previously out-of-print books from the distinguished backlist of Princeton University Press. These editions preserve the original texts of these important books while presenting them in durable paperback and hardcover editions. The goal of the Princeton Legacy Library is to vastly increase access to the rich scholarly heritage found in the thousands of books published by Princeton University Press since its founding in 1905.
Author: D. Brian Spalding Publisher: Elsevier ISBN: 1483160661 Category : Technology & Engineering Languages : en Pages : 445
Book Description
Numerical Prediction of Flow, Heat Transfer, Turbulence and Combustion: Selected Works of Professor D. Brian Spalding focuses on the many contributions of Professor Spalding on thermodynamics. This compilation of his works is done to honor the professor on the occasion of his 60th birthday. Relatively, the works contained in this book are selected to highlight the genius of Professor Spalding in this field of interest. The book presents various research on combustion, heat transfer, turbulence, and flows. His thinking on separated flows paved the way for the multi-dimensional modeling of turbulence. Arguments on the universality of the models of turbulence and the problems that are associated with combustion engineering are clarified. The text notes the importance of combustion science as well as the problems associated with it. Mathematical computations are also presented in determining turbulent flows in different environments, including on curved pipes, curved ducts, and rotating ducts. These calculations are presented to further strengthen the claims of Professor Spalding in this discipline. The book is a great find for those who are interested in studying thermodynamics.
Author: Igor V. Shevchuk Publisher: Springer ISBN: 3319209612 Category : Science Languages : en Pages : 253
Book Description
This monograph presents results of the analytical and numerical modeling of convective heat and mass transfer in different rotating flows caused by (i) system rotation, (ii) swirl flows due to swirl generators, and (iii) surface curvature in turns and bends. Volume forces (i.e. centrifugal and Coriolis forces), which influence the flow pattern, emerge in all of these rotating flows. The main part of this work deals with rotating flows caused by system rotation, which includes several rotating-disk configurations and straight pipes rotating about a parallel axis. Swirl flows are studied in some of the configurations mentioned above. Curvilinear flows are investigated in different geometries of two-pass ribbed and smooth channels with 180° bends. The author demonstrates that the complex phenomena of fluid flow and convective heat transfer in rotating flows can be successfully simulated using not only the universal CFD methodology, but in certain cases by means of the integral methods, self-similar and analytical solutions. The book will be a valuable read for research experts and practitioners in the field of heat and mass transfer.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
Extended or finned surfaces are widely used in compact heat exchangers to reduce the thermal resistance of air- or gas-side flows. Besides increasing the effective heat transfer surface area, geometrically modified finned surfaces also improve the heat transfer coefficient by altering the flow field. Wavy plate-fin surfaces have such properties and promote relatively high thermal-hydraulic performance. They are also attractive for their simplicity of manufacture and ease of use in compact heat exchangers. The current study numerically investigates the fluid flow and enhanced convection heat transfer in two-dimensional and three-dimensional wavy plate-fin passages with sinusoidal wall corrugations in the low Reynolds number regime. Constant property, periodically fully developed, and laminar or low Reynolds number forced convection are considered. The governing equations of continuity, momentum, and energy are solved computationally using finite-volume techniques. The solution procedure is based on the SIMPLE algorithm and a non-orthogonal, non-uniform grid. The influences of fin geometry (fin spacing, fin height, fin amplitude and fin length) on the enhanced heat transfer and fluid flow behaviors are investigated. The simulation results for the velocity and temperature distributions, isothermal Fanning friction f, and Colburn factor j are presented and discussed. The complex flow patterns in the wavy-fin channel are characterized by re-circulating and/or helical swirl flows with periodic flow separation and reattachment. Two flow regimes can be classified based on these results, namely, (1) low-Re streamline-flow regime where viscous forces dominate, and (2) high-Re swirl-flow regime characterized by flow recirculation and/or helical vortices. Heat transfer enhancement is observed in the swirl flow regime along with an increased pressure drop penalty, as a consequence of the periodic thermal boundary-layer thinning, strong flow mixing, and periodic generation and dissipation of vortices or re-circulating cells. In the streamline-flow regime, the flow and heat transfer behavior are similar to that in straight flow channel, though an enhanced performance is obtained. Also, results of flow visualization experiment for a two-dimensional wavy flow channel are shown to agree well with the numerical results. Finally, the computational methodology is extended to illustrate the flow behaviors in out-of-phase wavy flow passages.
Author: Victor I. Terekhov Publisher: Springer ISBN: 3319044532 Category : Technology & Engineering Languages : en Pages : 64
Book Description
In this book the author presents selected challenges of thermal-hydraulics modeling of two-phase flows in minichannels with change of phase. These encompass the common modeling of flow boiling and flow condensation using the same expression. Approaches to model these two respective cases show, however, that experimental data show different results to those obtained by methods of calculation of heat transfer coefficient for respective cases. Partially that can be devoted to the fact that there are non-adiabatic effects present in both types of phase change phenomena which modify the pressure drop due to friction, responsible for appropriate modelling. The modification of interface shear stresses between flow boiling and flow condensation in case of annular flow structure may be considered through incorporation of the so called blowing parameter, which differentiates between these two modes of heat transfer. On the other hand, in case of bubbly flows, the generation of bubbles also modifies the friction pressure drop by the influence of heat flux. Presented are also the results of a peculiar M-shape distribution of heat transfer coefficient specific to flow boiling in minichannels. Finally, some attention is devoted to mathematical modeling of dryout phenomena. A five equation model enabling determination of the dryout location is presented, where the mass balance equations for liquid film, droplets and gas are supplemented by momentum equations for liquid film and two-phase core.
Author: Kelechi Ezeji
Author: Kelechi Ezeji
Author: Frederick F. Simon
Author: Siegfried Wagner
Author: Chia-Ch'iao Lin
Author: Paul D. Hancock
Author: D. Brian Spalding
Author: Bart A. Singer
Author: Igor V. Shevchuk
Author: 
Author: Victor I. Terekhov