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Author: Phaninder Injeti Publisher: ISBN: Category : Languages : en Pages :
Book Description
ABSTRACT: In this project we studied the effect of different parameters on heat transfer in two-dimensional microchannels, microtubes and also tube-in-block heat exchangers for various engineering applications. These included the use of flow restrictions to enhance local heat or mass transfer rate, enhancement of conjugate heat transfer with discrete heating and magnetic coolers (or heaters) associated with magnetic refrigeration system. The results of this research will help in designing the heating or cooling systems and selection of their appropriate geometrical dimensions and materials for specific applications. Types of problems studied in this project are: steady state analysis of forced convection around a restricted flow passage in a micro channel, effect of protrusions in a microtube or microchannel for conjugate heat transfer with uniform or discrete heating and transient analysis of heat transfer in trapezoidal microchannels under time varying heat source. For each of these problems a numerical simulation model was developed. The mass, momentum, and energy conservation equations were solved in the fluid region and energy conservation in the sold region to arrive at the velocity and the temperature distributions. Detailed parametric study was carried out for each problem. The parameters were shape and size of the restriction/protrusion, number of restrictions/protrusions, wall thickness, Reynolds number, solid materials and working fluids. The results showed that in microtubes the local value of Nusselt number increases at the restriction/protrusion and the global value for the whole tube is somewhat lower. For a two-dimensional microchannel, both the local Nusselt number at the restriction/protrusion as well as the global Nusselt number for the entire channel is higher. In the trapezoidal channels the results showed that with the increase in Reynolds number, the outlet temperature decreased and the average heat transfer coefficient increased. With an increase in magnetic field there was an increase in the solid fluid interface temperature and in turn the average heat transfer coefficient increased. With a decrease in the channel height and width there was an increase in the average Nusselt number in the channel.
Author: Phaninder Injeti Publisher: ISBN: Category : Languages : en Pages :
Book Description
ABSTRACT: In this project we studied the effect of different parameters on heat transfer in two-dimensional microchannels, microtubes and also tube-in-block heat exchangers for various engineering applications. These included the use of flow restrictions to enhance local heat or mass transfer rate, enhancement of conjugate heat transfer with discrete heating and magnetic coolers (or heaters) associated with magnetic refrigeration system. The results of this research will help in designing the heating or cooling systems and selection of their appropriate geometrical dimensions and materials for specific applications. Types of problems studied in this project are: steady state analysis of forced convection around a restricted flow passage in a micro channel, effect of protrusions in a microtube or microchannel for conjugate heat transfer with uniform or discrete heating and transient analysis of heat transfer in trapezoidal microchannels under time varying heat source. For each of these problems a numerical simulation model was developed. The mass, momentum, and energy conservation equations were solved in the fluid region and energy conservation in the sold region to arrive at the velocity and the temperature distributions. Detailed parametric study was carried out for each problem. The parameters were shape and size of the restriction/protrusion, number of restrictions/protrusions, wall thickness, Reynolds number, solid materials and working fluids. The results showed that in microtubes the local value of Nusselt number increases at the restriction/protrusion and the global value for the whole tube is somewhat lower. For a two-dimensional microchannel, both the local Nusselt number at the restriction/protrusion as well as the global Nusselt number for the entire channel is higher. In the trapezoidal channels the results showed that with the increase in Reynolds number, the outlet temperature decreased and the average heat transfer coefficient increased. With an increase in magnetic field there was an increase in the solid fluid interface temperature and in turn the average heat transfer coefficient increased. With a decrease in the channel height and width there was an increase in the average Nusselt number in the channel.
Author: Abdullatif Abdulhadi Gari Publisher: ISBN: Category : Languages : en Pages : 218
Book Description
This project studied the effect of different parameters on the conjugate heat transfer in tube-in-block heat exchangers for various engineering applications. These included magnetic coolers (or heaters) associated with a magnetic refrigeration system, high heat flux coolers for electronic equipment, and hydronic snow melting system embedded in concrete slabs. The results of this research will help in designing the cooling/heating systems and select their appropriate geometrical dimensions and material for specific applications. Types of problems studied in this project are: steady state circular microchannels with heat source in the gadolinium substrate, transient heat transfer in circular microchannels with time varying heat source in a gadolinium substrate, transient heat transfer in composite trapezoidal microchannels of silicon and gadolinium with constant and time varying heat source, steady state heat transfer in microchannels using fluids suspended with nanoparticles, and analysis of steady state and transient heat transfer in a hydronic snow melting system. For each of these problems a numerical simulation model was developed. The mass, momentum, and energy conservation equations were solved in the fluid region and energy conservation in the solid region of the heat exchanger to arrive at the velocity and temperature distributions. Detailed parametric study was carried out for each problem. Parameters were Reynolds number, heat source value, channel diameter or channel height, solid materials and working fluids. Results are presented in terms of solid-fluid interface temperature, heat flow rate, heat transfer coefficient, and Nusselt number along the length of the channel and with the progression of time. The results showed that an increase in Reynolds number decreases the interface temperature but increases the heat flow rate and Nusselt number. When the heat source varied with time, by applying and removing the magnetic field, the interface temperature, heat flow rate, and Nusselt number attained a periodic variation with time. The decrease in the diameter at constant Reynolds number decreases the interface temperature and increases the heat flow rate at the fluid-solid interface.
Author: Roxana Durantes Sandoval Publisher: ISBN: Category : Conjugate heat transfer Languages : en Pages : 0
Book Description
In this thesis, numerical simulations of the convective heat transfer on single-phase fluid flow wavy microchannel exposed to a heat flux are presented. First, a methodology based on local and global energy balances in the device instead of the commonly used Nusselt number is proposed to investigate the heat transfer enhancement in these systems. Then, to reduce the computational cost, an examination of the validity of two-dimensional approximations of three-dimensional is performed. A systematic approach is used to determine when the two-dimensional approximation for different channel width values departs from the three-dimensional original model and at what width values it isreasonable to make a two-dimensional simplification. For comparison, a two-dimensional model is also built and solved. The governing equations for an incompressible laminar flow and conjugate heat transfer are solved for representative models, under steady state and several operating conditions, by the finite element method. Results show that theaveraged energy-balance methodology enables higher accuracy than that based on the Nusselt number since neither heat transfer coefficients nor characteristic temperatures are needed. For the two-dimensional approximation, as the width is increased beyond 15 mm in width, results in the three-dimensional model tend to approach the ones of thetwo-dimensional model. Two-dimensional models require less memory and computational time, and they can have some advantages when performing parameter optimization.
Author: Renato M. Cotta Publisher: Springer ISBN: 3319233122 Category : Science Languages : en Pages : 175
Book Description
This book focuses on the modeling and analysis of heat and fluid flow in microchannels and micro-systems, compiling a number of analytical and hybrid numerical-analytical solutions for models that account for the relevant micro-scale effects, with the corresponding experimental analysis validation when applicable. The volume stands as the only available compilation of easy to use analytically-based solutions for micro-scale heat and fluid flow problems, that systematically incorporates the most relevant micro-scale effects into the mathematical models, followed by their physical interpretation on the micro-system behavior.
Author: Satish Kandlikar Publisher: Elsevier ISBN: 9780080445274 Category : Science Languages : en Pages : 492
Book Description
&Quot;This book explores flow through passages with hydraulic diameters from about 1 [mu]m to 3 mm, covering the range of minichannels and microchannels. Design equations along with solved examples and practice problems are also included to serve the needs of practicing engineers and students in a graduate course."--BOOK JACKET.
Author: L. P. Yarin Publisher: Springer Science & Business Media ISBN: 3540787550 Category : Science Languages : en Pages : 487
Book Description
The subject of the book is uid dynamics and heat transfer in micro-channels. This problem is important for understanding the complex phenomena associated with single- and two-phase ows in heated micro-channels. The challenge posed by high heat uxes in electronic chips makes thermal management a key factor in the development of these systems. Cooling of mic- electronic components by new cooling technologies, as well as improvement of the existing ones, is becoming a necessity as the power dissipation levels of integrated circuits increases and their sizes decrease. Miniature heat sinks with liquid ows in silicon wafers could signi cantly improve the performance and reliability of se- conductor devices. The improvements are made by increasing the effective thermal conductivity, by reducing the temperature gradient across the wafer, by reducing the maximum wafer temperature, and also by reducing the number and intensity of localized hot spots. A possible way to enhance heat transfer in systems with high power density is to change the phase in the micro-channels embedded in the device. This has motivated a number of theoretical and experimental investigations covering various aspects of heat transfer in micro-channel heat sinks with phase change. The ow and heat transfer in heated micro-channels are accompanied by a n- ber of thermohydrodynamic processes, such as liquid heating and vaporization, bo- ing, formation of two-phase mixtures with a very complicated inner structure, etc., which affect signi cantly the hydrodynamic and thermal characteristics of the co- ing systems.
Author: Alexander Louis London Publisher: CRC Press ISBN: 9781560320128 Category : Heat exchangers Languages : en Pages : 798
Book Description
Heat exchangers are a crucial part of aerospace, marine, cryogenic and refrigeration technology. These essays cover such topics as complicated flow arrangements, complex extended surfaces, two-phase flow and irreversibility in heat exchangers, and single-phase heat transfer.
Author: Yan Fan Publisher: Springer ISBN: 3319096478 Category : Science Languages : en Pages : 143
Book Description
The main aim of this book is to introduce and give an overview of a novel, easy, and highly effective heat transfer augmentation technique for single-phase micro/minichannel heat sink. The specific objectives of the volume are to: Introduce a novel planar oblique fin microchannel and cylindrical oblique fin minichannel heat sink design using passive heat transfer enhancement techniques Investigate the thermal transport in both planar and cylindrical oblique fin structures through numerical simulation and systematic experimental studies. Evaluate the feasibility of employing the proposed solution in cooling non-uniform heat fluxes and hotspot suppression Conduct the similarity analysis and parametric study to obtain empirical correlations to evaluate the total heat transfer rate of the oblique fin heat sink Investigate the flow mechanism and optimize the dimensions of cylindrical oblique fin heat sink Investigate the influence of edge effect on flow and temperature uniformity in these oblique fin channels.
Author: Susumu Kotake Publisher: Elsevier Publishing Company ISBN: Category : Computers Languages : en Pages : 370
Book Description
This book describes methodologies for performing numerical simulations of transport processes in heat transfer and fluid flow. The reader is guided to make the proper selection of simulation techniques and to interpret the acquired results based on the flow physics involved. Computer programs which are used to solve heat transfer and fluid flow problems are integrated into the text. Illustrative examples of thermo-fluid phenomena are provided in every chapter to enhance understanding of the subjects by offering the reader hands-on experience of numerical simulations. Most of the fundamental transport processes in heat transfer and fluid flow, e.g. heat conduction in a solid body, convection heat transfer of a fin, laminar and turbulent heat transfer and flow in a duct or tube, and boundary layers over a flat plate are covered. A strong emphasis is placed on examinations of the thermo-fluid phenomena inside a flow passage (such as tube and a channel). The book contains detailed discussions on the formulation of the boundary conditions which is often the key issue in making successful numerical simulations of the physical phenomena of interest. Simulations are carefully designed so that conventional 16-bit personal computers, such as IBM PCreg; or Apple Macintoshreg; can be used. Visualizing the simulated results in graphic form (plotting charts and line contours of physical variables) significantly enhances the reader's understanding of the important transport processes. The book is intended as an introductory text for numerical simulations of heat transfer and fluid flow phenomena. Description is simple and self-contained so that beginners can easily understand the material, yet it will also serve as a useful reference work for the practitioner. Exercise problems are supplied by which the reader can consolidate knowledge of simulation techniques described and gain further insight in the physical processes of interest. The book contains two 3frac12; inch floppy disks, each of which stores a complete set of simulation source codes discussed in the text. These programs are recorded in ASCII format and can be run either on IBM PCreg; or Macintoshreg; using QuickBasicreg;. The programs are well-documented within the text as well as in the codes themselves with a number of comment statements. This helps the reader understand the flow of program runs and, if the reader so wishes, modifying the original source codes. To facilitate prescription of the physical conditions for simulations, these programs run in a highly interactive mode. In addition, the diskettes contain a number of compiled programs which can be executed without the QuickBasicreg; program.
Author: Phaninder Injeti
Author: Phaninder Injeti
Author: Abdullatif Abdulhadi Gari
Author: Ningli Liu
Author: Roxana Durantes Sandoval
Author: Renato M. Cotta
Author: Satish Kandlikar
Author: L. P. Yarin
Author: Alexander Louis London
Author: Yan Fan
Author: Susumu Kotake