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Analysis Of Conjugate Heat Transfer And Pressure Drop In Microchannels For Different Aspects Ratios
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Book Synopsis Analysis of Conjugate Heat Transfer and Pressure Drop in Microchannels for Different Aspects Ratios by : Marc Robert Greenland
Download or read book Analysis of Conjugate Heat Transfer and Pressure Drop in Microchannels for Different Aspects Ratios written by Marc Robert Greenland and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In this study the heat transfer and hydrodynamic parameters were experimentally investigated for a single microchannel housed in a stainless steel solid base material for different aspect ratios in the laminar regime with water as the working fluid. The stainless steel base material had a low thermal conductivity (15.1 W / mK) which magnified the conjugative effects in order to better understand the heat transfer. Rectangular microchannels with a height and width of 0.64 mm x 0.41 mm for Test Section 1, 0.5 mm x 0.5 mm for Test Section 2 and 0.43 mm x 0.58 mm for Test Section 3 were considered. The overall width of the solid substrate was 1.5 mm and the length was 50 mm for all of the test sections. The aspect ratio of the channel and the solid substrate was kept equal. A constant heat flux of 10 W / cm2 was applied to the bottom outer wall of the test section. A sudden contraction inlet and a sudden expansion outlet manifold contained pressure ports, to measure the pressure drop across the test sections, and thermocouples measured the mean inlet and outlet fluid temperatures. Thermocouples were used to measure the outer top and side wall temperatures at four equally spaced positions along the axial direction. The amount of axial heat conduction was below 0.6 % for all of the test sections and therefore warranted the use of a two-dimensional conduction model to determine the heat transfer parameters at the fluid to solid interface based on the outer measured wall temperatures. The local Nusselt number decreased, along the axial direction but increased towards the exit for all of the test sections. The average Nusselt number increased with the flow rate and the critical Reynolds number for fully turbulent flow Test Section 1 was 1950, for Test Section 2 was 2250 and for Test Section 3 was 1650. The average Nusselt number was directly related to the perimeter of the microchannels two side walls and the bottom wall (not the top wall), and thus decreased as the aspect ratio of the channel increased. The experimentally determined Nusselt numbers were larger for all three test sections when compared to common acceptable correlations. The friction factor decreased with the flow rate and was smaller in magnitude when compared to conventional theories. The diabatic friction factor magnitudes were smaller than the adiabatic friction factors. The friction factor decreased as the aspect ratio decreased, where the aspect ratio was calculated by taking the maximum of the microchannels width or height, divided by the minimum of the two. The possibility of a relationship could exist between the Colburn j-factor and the friction factor when considering the results for Test Section 1 and Test Section 2 but the results for Test Section 3 were significantly different.
Book Synopsis Study of Pressure Drop and Heat Transfer in Micro Channel Branch with Varying Bifurcation Angle, Aspect Ratio, and Temperature by : Teja Swaroop Naik Mudiki
Download or read book Study of Pressure Drop and Heat Transfer in Micro Channel Branch with Varying Bifurcation Angle, Aspect Ratio, and Temperature written by Teja Swaroop Naik Mudiki and published by . This book was released on 2017 with total page 43 pages. Available in PDF, EPUB and Kindle. Book excerpt: The current study is focused on studying the effects of temperature and bifurcation angle on pressure drop as well as heat transfer in micro-channels for two Newtonian fluids - water and air. The microchannel of aspect ratio 1 and 1.5 with hydraulic diameters 500 microns and 600 microns were investigated for a fully developed laminar flow bifurcated after the flow reached its hydrodynamic developed length with bifurcation angles of 30?,60?,90?,120? and 150?. Temperatures of 318.15K, 333.15K, and 345.15K are induced on top surface of the microchannel for mentioned bifurcated angles to analyze the effective angle at which the heat transfer was highest with minimal pressure drop. The branching of the microchannel was done after the flow has reached its hydrodynamically developed length, which is calculated based on the hydraulic diameter [11] and flow is thermally developing due to the wake effects at entrance region [29]. Accordingly, the test section was modeled in Ansys, imposing constant temperature boundary condition on one face of the ducts of varied aspect ratios. The 3-D simulations are performed in Ansys - Fluent software with the laminar model and conditions of the steady state, considering fluids as incompressible and irrotational. The pressure drop and heat transfer characteristics of the various configurations are tabulated for examining and to draw comparisons. It is observed that both the heat transfer and pressure drop increases with bifurcation angle. The relative bifurcation angle between two symmetrically branched microchannels at which the pressure drop and heat transfer are optimum is concluded.
Book Synopsis Heat Transfer and Pressure Drop in Flow Boiling in Microchannels by : Sujoy Kumar Saha
Download or read book Heat Transfer and Pressure Drop in Flow Boiling in Microchannels written by Sujoy Kumar Saha and published by Springer. This book was released on 2015-07-08 with total page 63 pages. Available in PDF, EPUB and Kindle. Book excerpt: This Brief addresses the phenomena of heat transfer and pressure drop in flow boiling in micro channels occurring in high heat flux electronic cooling. A companion edition in the Springer Brief Subseries on Thermal Engineering and Applied Science to “Critical Heat Flux in Flow Boiling in Micro channels,” by the same author team, this volume is idea for professionals, researchers and graduate students concerned with electronic cooling.
Book Synopsis Heat Transfer and Fluid Flow in Minichannels and Microchannels by : Satish Kandlikar
Download or read book Heat Transfer and Fluid Flow in Minichannels and Microchannels written by Satish Kandlikar and published by Elsevier. This book was released on 2006 with total page 492 pages. Available in PDF, EPUB and Kindle. Book excerpt: &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.
Book Synopsis Laminar Flow Forced Convection in Ducts by : R. K. Shah
Download or read book Laminar Flow Forced Convection in Ducts written by R. K. Shah and published by Academic Press. This book was released on 2014-06-28 with total page 492 pages. Available in PDF, EPUB and Kindle. Book excerpt: Laminar Flow Forced Convection in Ducts is a sourcebook for compact heat exchanger analytical data. This book describes the analytical solutions for laminar fluid flow and forced convection heat transfer in circular and noncircular pipes, including applicable differential equations and boundary conditions involving velocity and temperature problems of fluid flow. The book also discusses fluid flow—how much power is required to pump fluids through the heat exchanger, as well as the heat transfer—the determination of q" distribution, and the temperature of fluid and walls. The text also analyzes the coolant or heat transfer fluid flows in a nuclear power reactor composed of a bundle of circular section fuel rods located inside a round tube. R.A. Axford addresses fluid flow and heat transfers results for the rod bundle geometry in "Heat Transfer in Rod Bundles." The book also provides an overview and guidelines that can be used for the designer and the applied mathematician. This book is suitable for engineers working in electronics, aerospace, instrumentation, and biomechanics that use cooling or heating exchanges or solar collection systems.
Book Synopsis Numerical Investigation of Fluid Flow and Heat Transfer Effects in Minichannels and Microchannels Under H2 Boundary Condition by : Viral Vinodray Dharaiya
Download or read book Numerical Investigation of Fluid Flow and Heat Transfer Effects in Minichannels and Microchannels Under H2 Boundary Condition written by Viral Vinodray Dharaiya and published by . This book was released on 2011 with total page 184 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Deviations in heat transfer predictions by classical theory for single-phase laminar flow in microchannels have been mainly attributed to surface roughness, deviations in channel dimensions, errors in measurement, entrance and exit effects. Identifying correct thermal boundary conditions in a given application also plays an important role in accurate estimation of heat transfer coefficients. Different thermal boundary conditions generally applied in fluid domain are: T, H1, and H2. However, there are very few solutions available for the heat transfer under the H2 boundary condition which is the most applicable thermal boundary condition in many microchannel heat exchangers. The current work aimed at addressing two outstanding issues in this field: (i) predicting heat transfer rate in rectangular channels under H2 boundary conditions, and (ii) numerically studying the effects of structured roughness on pressure drop and heat transfer. A numerical model is developed to predict accurate fluid flow and heat transfer effects in microchannels under H2 boundary condition. Numerical data sets are generated for rectangular microchannels with different heated wall configurations. Although the results are seen as relevant in microscale applications, they are applicable to any sized channels. Based on the numerical results obtained for a wide range of aspect ratios, generalized correlations for fully developed laminar Nusselt number as a function of channel aspect ratio are presented for all the cases. This information can provide better understanding and insight into the transport processes in the microchannels. Surface roughness effects in conventional ducts are minimal whereas for the micro-sized channel, the roughness effects needs to be taken into account for laminar flow. Developing a better insight of the fundamental effects of surface roughness in parallel plate microchannels is therefore essential. Based on various roughness characterization schemes, the effect of structured roughness elements for incompressible laminar fluid flow is analyzed and the proposed numerical model is extended to accurately predict the pressure drop and heat transfer coefficient in presence of roughness using CFD software, FLUENT. The results are compared with the available experimental data for some of the rough surfaces."--Abstract.
Book Synopsis Selected Papers from the ISTEGIM'19 by : Lucien Baldas
Download or read book Selected Papers from the ISTEGIM'19 written by Lucien Baldas and published by MDPI. This book was released on 2021-03-01 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt: This Special Issue compiles 11 scientific works that were presented during the International Symposium on Thermal Effects in Gas Flow in Microscale, ISTEGIM 2019, held in Ettlingen, Germany, in October 2019. This symposium was organized in the framework of the MIGRATE Network, an H2020 Marie Skłodowska-Curie European Training Network that ran from November 2015 to October 2019 (www.migrate2015.eu). MIGRATE intends to address some of the current challenges in innovation that face the European industry with regard to heat and mass transfer in gas-based microscale processes. The papers collected in this book focus on fundamental issues that are encountered in microfluidic systems involving gases, such as the analysis of gas–surface interactions under rarefied conditions, the development of innovative integrated microsensors for airborne pollutants, new experimental techniques for the measurement of local quantities in miniaturized devices and heat transfer issues inside microchannels. The variety of topics addressed in this book emphasizes that multi-disciplinarity is the real common thread of the current applied research in microfluidics. We hope that this book will help to stimulate early-stage researchers who are working in microfluidics all around the world. This book is dedicated to them!
Book Synopsis Fluid Mechanics and Fluid Power (Vol. 1) by : Suvanjan Bhattacharyya
Download or read book Fluid Mechanics and Fluid Power (Vol. 1) written by Suvanjan Bhattacharyya and published by Springer Nature. This book was released on 2023-05-10 with total page 479 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents the select proceedings of the 48th National Conference on Fluid Mechanics and Fluid Power (FMFP 2021) held at BITS Pilani in December 2021. It covers the topics such as fluid mechanics, measurement techniques in fluid flows, computational fluid dynamics, instability, transition and turbulence, fluid‐structure interaction, multiphase flows, micro- and nanoscale transport, bio-fluid mechanics, aerodynamics, turbomachinery, propulsion and power. The book will be useful for researchers and professionals interested in the broad field of mechanics.
Book Synopsis Measurement of Pressure Drop and Heat Transfer Analysis of Microchannels by : Cormac James Eason
Download or read book Measurement of Pressure Drop and Heat Transfer Analysis of Microchannels written by Cormac James Eason and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Fundamentals of Heat Exchanger Design by : Ramesh K. Shah
Download or read book Fundamentals of Heat Exchanger Design written by Ramesh K. Shah and published by John Wiley & Sons. This book was released on 2003-08-11 with total page 978 pages. Available in PDF, EPUB and Kindle. Book excerpt: Comprehensive and unique source integrates the material usually distributed among a half a dozen sources. * Presents a unified approach to modeling of new designs and develops the skills for complex engineering analysis. * Provides industrial insight to the applications of the basic theory developed.
Book Synopsis Handbook of Heat Transfer by : Warren M. Rohsenow
Download or read book Handbook of Heat Transfer written by Warren M. Rohsenow and published by McGraw-Hill Companies. This book was released on 1973 with total page 1552 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Gas Flows in Microsystems by : Lucien Baldas
Download or read book Gas Flows in Microsystems written by Lucien Baldas and published by MDPI. This book was released on 2019-10-28 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt: The last two decades have witnessed a rapid development of microelectromechanical systems (MEMS) involving gas microflows in various technical fields. Gas microflows can, for example, be observed in microheat exchangers designed for chemical applications or for cooling of electronic components, in fluidic microactuators developed for active flow control purposes, in micronozzles used for the micropropulsion of nano and picosats, in microgas chromatographs, analyzers or separators, in vacuum generators and in Knudsen micropumps, as well as in some organs-on-a-chip, such as artificial lungs. These flows are rarefied due to the small MEMS dimensions, and the rarefaction can be increased by low-pressure conditions. The flows relate to the slip flow, transition or free molecular regimes and can involve monatomic or polyatomic gases and gas mixtures. Hydrodynamics and heat and mass transfer are strongly impacted by rarefaction effects, and temperature-driven microflows offer new opportunities for designing original MEMS for gas pumping or separation. Accordingly, this Special Issue seeks to showcase research papers, short communications, and review articles that focus on novel theoretical and numerical models or data, as well as on new experimental results and technics, for improving knowledge on heat and mass transfer in gas microflows. Papers dealing with the development of original gas MEMS are also welcome.
Book Synopsis Laminar Flow Forced Convection Heat Transfer Behavior of Phase Change Material Fluid in Straight and Staggered Pin Microchannels by : Satyanarayana Kondle
Download or read book Laminar Flow Forced Convection Heat Transfer Behavior of Phase Change Material Fluid in Straight and Staggered Pin Microchannels written by Satyanarayana Kondle and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Microchannels have been studied extensively for electronic cooling applications ever since they were found to be effective in removing high heat flux from small areas. The rate of heat removed using microchannels depends on many factors including the geometry shape, solid and fluid materials used, and surface roughness, among others. Many configurations of microchannels have been studied with various materials and compared for their effectiveness in heat removal. However, there is little research done so far in using Phase Change Material (PCM) fluids and pin fins in microchannels to enhance the heat transfer. PCM fluids exhibit greater heat transfer when the phase change material undergoes liquid-to-solid transformation. Staggered pins in microchannels have also shown higher heat removal characteristics because of the continuous breaking and formation of the thermal and hydrodynamic boundary layer; they also exhibit higher pressure drop because pins act as flow obstructers. This paper presents numerical results of circular, square, straight rectangular microchannels with various aspect ratios (1:2, 1:4 and 1:8), and rectangular microchannels with two characteristic staggered pins (square and circular, fixed height with no variation in aspect ratio). The heat transfer performance of a single phase fluid and PCM fluid in all of these microchannels and the corresponding pressure drop characteristics are also presented. An effective specific heat capacity model was used to account for the phase change process of PCM fluid. Comparison of heat transfer characteristics of single phase fluid and PCM fluid are presented for all the geometries considered. Among the straight microchannels, 1:8 geometry was found to have the highest Nusselt number. The use of PCM fluid in straight microchannels increased the Nusselt number by 3-7 percent compared to the single phase fluids. Among the staggered pin microchannels, circular pins were found to be more effective in terms of heat transfer by exhibiting higher Nusselt number. Circular pin microchannels were also found to have lower pressure drop compared to the square pin microchannels. Overall, for all the geometries considered, it was found that the PCM fluid enhances the heat transfer compared to the SPF fluid.
Book Synopsis Fluid Mechanics and Heat Transfer by : Kaveh Hariri Asli
Download or read book Fluid Mechanics and Heat Transfer written by Kaveh Hariri Asli and published by CRC Press. This book was released on 2015-06-10 with total page 246 pages. Available in PDF, EPUB and Kindle. Book excerpt: This valuable new book focuses on new methods and techniques in fluid mechanics and heat transfer in mechanical engineering. The book includes the research of the authors on the development of optimal mathematical models and also uses modern computer technology and mathematical methods for the analysis of nonlinear dynamic processes.It covers techn
Book Synopsis Compact Heat Exchangers by : Alexander Louis London
Download or read book Compact Heat Exchangers written by Alexander Louis London and published by CRC Press. This book was released on 1990 with total page 798 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Book Synopsis Effect of Aspect Ratio and Bifurcation Angle on Single Phase Flow Through Branched Structure Microchannel by : Pavan Vellore Kumaraswamy
Download or read book Effect of Aspect Ratio and Bifurcation Angle on Single Phase Flow Through Branched Structure Microchannel written by Pavan Vellore Kumaraswamy and published by . This book was released on 2017 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt: The introduction of microchannel heat exchangers (MCHE) has revolutionized the cooling technology which has led to the miniaturization of devices. MCHEs are highly preferred in many applications because of their characteristic large heat transfer area to unit volume leading to higher efficiency compared to conventional heat exchangers. Due to their compactness, they are mainly used in electronic cooling; in recent times, their application is extended to the medical field for cooling scanning equipment. However, the small channel size increases pressure drop. Present study focuses on optimizing the performance of the MCHEs by carrying out single phase flow analysis of lung bronchial like branched structure in ANSYS (Fluent) with different aspect ratios (AR) between 0.5, 1.0, 1.5 and 2.0 at the inlet, and at different bifurcation angles of 30, 45 and 60 and 70 degrees. Symmetric geometry containing four bifurcation levels were designed. A number of geometries were created for varying bifurcation angle and varying aspect ratio. Simulations were carried out for steady state and laminar flow conditions. Results so far show that pressure drop decreased with increase in AR and achieved better uniformity in temperature throughout the channel length for higher AR.
Book Synopsis Analysis of Heat Transfer Enhancement Through Multi-harmonic Wavy Microchannels by : Justin Moon
Download or read book Analysis of Heat Transfer Enhancement Through Multi-harmonic Wavy Microchannels written by Justin Moon and published by . This book was released on 2019 with total page 219 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this study, a three-dimensional finite element model of steady-state flow and heat transfer in micro-channels are simulated to investigate the effects of conjugate heat transfer. The baseline geometry consists of a copper block with water as the working fluid as the micro-sized heat exchanger system. The governing equations of both an incompressible non-isothermal laminar flow and conjugate heat transfer are built and solved. The focus is on the influence of channel surface-topography for the proposed multi-harmonic geometry, through a parametric analysis via finite element methods.The analysis is then extended by considering a variety of conductive materials for the solid block that encloses the channel, and their impact on the heat transfer enhancement in these devices. The same governing equations are used, for representative single- and harmonic-wavy-channel models, with copper, aluminum, silicon, and steel-317 as solid-block materials and different operating conditions, by the finite element technique.By using the ratio of the Nusselt number for wavy to straight channels, a parametric analysis -- for a set of cold-water flow-rates (Re=50, 100 and 150) -- shows that the addition of harmonic surfaces enhances the transfer of energy and that such ratio achieves the highest value with wave harmonic numbers of n=-2 and n=+2. Regardless of the material, as wave amplitude and Reynolds number increase, so does the effectiveness of the device, and that the selection of specific material highly impacts the diffusion of heat in the solid, but it is negligible on the Nusselt number for the fluid.Finally, results of the performance factor PF, defined as the ratio of the Nusselt number to the pressure drop, indicate that the device is ineffective in the heat transfer enhancement relative to the required pumping power for small values of Reynolds number Re, but the device becomes very effective for larger Re-values.
