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Enhanced Flow Boiling Heat Transfer In Microchannels With Structured Surfaces At Varied Mass Flow Rates
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Book Synopsis Enhanced Flow Boiling Heat Transfer in Microchannels with Structured Surfaces at Varied Mass Flow Rates by : David Wei Bian
Download or read book Enhanced Flow Boiling Heat Transfer in Microchannels with Structured Surfaces at Varied Mass Flow Rates written by David Wei Bian and published by . This book was released on 2015 with total page 46 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis investigates the role of mass flux on flow boiling heat transfer in microchannels with surface micropillar arrays. The motivation for this investigation was to determine the general trends of the optimal micropillar array geometry in terms of its heat transfer capabilities. The experiment was conducted with three microchannels: a flat surface microchannel, a sample called the 5-15 (height h = 25 [mu]m, diameter d = 5 [mu]m, and pitch l = 15 [mu]m) and a sample called the 10-40 (height h = 25 [mu]m, diameter d = 10 [mu]m, and pitch l = 40 [mu]m). The structured surface microchannels, due to their capillary pressure-induced wicking capabilities, exhibited less temperature rise and pressure drop fluctuations at high heat fluxes. Furthermore, it was verified that the critical heat flux value of all microchannels increased with mass flux. In addition, it was concluded that at lower mass fluxes, the relative percentage heat transfer enhancement of the structured surface microchannels over the flat surface microchannel was greater. The trend observed suggests that denser samples are better at lower mass fluxes. However, if a sample is too dense, there may be too much viscous drag. Thus, an optimal balance between capillary force and viscous drag must be found in order to determine the optimum micropillar array geometry and density for maximizing the critical heat flux value. Finally, for a given mass flux, the pressure drop across every microchannel was approximately equal at all heat fluxes. This implies that no additional power consumption is required to pump a particular mass flux through a structured surface microchannel than a flat surface microchannel, though there is certainly additional power required to increase the mass flux. This work provides insights into the roles of both the micropillar array surface structures and the mass fluxes on the heat transfer performance of flow boiling in microchannels. The results and observations of this experiment may prove helpful in guiding future work in an attempt to optimize microchannels for heat transfer applications in electronics.
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 Bubble Dynamics on Structured Surface in Microchannel by : Siyu Chen (S.M.)
Download or read book Bubble Dynamics on Structured Surface in Microchannel written by Siyu Chen (S.M.) and published by . This book was released on 2013 with total page 72 pages. Available in PDF, EPUB and Kindle. Book excerpt: Surface enhancement is a potential way to improve the performance of flow boiling in microchannels, which is considered to be one of the most promising cooling methods to solve thermal management challenges faced by future semiconductor products. Considerable research has been done on examining the functions of engineered surfaces. However, the mechanism of how these surfaces improve the flow boiling performance is still unclear. In this thesis, bubble dynamics on micropillar array surfaces were studied. A surface energy based model is presented to predict the bubble morphology on pillar array surfaces. The results showed that bubbles tend to stay on top surfaces of pillars at solid fractions greater than 0.162, keeping liquid films underneath the bubbles. On the other hand, on surfaces at solid fraction less than 0.162, bubbles tend to propagate within the pillar unit cells. A flow loop with good degassing and a fluid temperature control system was designed and built for various flow boiling experiments. Five different types of silicon micropillar array surfaces were fabricated. Moreover a setup for observing bubble dynamics in microchannels under flow boiling conditions was developed. Experiments were performed to investigate the bubble dynamics on silicon micropillar array surfaces. Bubble departure modes were observed. The bubble departure size of direct departing mode was found to be independent with flow rate while departure size of sliding mode decreased with increasing of the flow rate. Three potential methods to create single nucleation sites for improved studies of bubble dynamics were also presented in this thesis. An experimental setup to investigate behavior of a single bubbles created by air injection on micropillar array was presented. Single 10-30 [mu]m injection holes were fabricated on micropillar array surfaces by laser cutter. The experimental results show that structured surfaces have higher bubble departure sizes than that for a plain surface. The surfaces with solid fractions greater than 0.162 had larger departure sizes than that of surfaces with solid fractions smaller than 0.162 at mass flow rates above 250 kg/m2s while departure sizes of the higher solid fraction surfaces become smaller than that of lower solid fraction surfaces when flow rates decreased below 200 kg/m2s. The similarity between the departure sizes obtained by air injection experiments and flow boiling experiments suggest that air injection experiments could provide useful information on understanding the vapor bubble departure behavior on micropillar array surfaces. Silicon micropillar array surfaces may have larger bubble departure sizes than plain surfaces, however, the surfaces with solid fractions greater than 0.162 are suggested for boiling due the a large amount of liquid thin films may create for higher heat transfer rates.
Book Synopsis Flow Boiling in Expanding Microchannels by : Tamanna Alam
Download or read book Flow Boiling in Expanding Microchannels written by Tamanna Alam and published by Springer. This book was released on 2017-05-24 with total page 89 pages. Available in PDF, EPUB and Kindle. Book excerpt: This Brief presents an up to date summary of details of the flow boiling heat transfer, pressure drop and instability characteristics; two phase flow patterns of expanding microchannels. Results obtained from the different expanding microscale geometries are presented for comparison and addition to that, comparison with literatures is also performed. Finally, parametric studies are performed and presented in the brief. The findings from this study could help in understanding the complex microscale flow boiling behavior and aid in the design and implementation of reliable compact heat sinks for practical applications.
Book Synopsis Convective Boiling and Condensation by : John G. Collier
Download or read book Convective Boiling and Condensation written by John G. Collier and published by Clarendon Press. This book was released on 1994-05-19 with total page 646 pages. Available in PDF, EPUB and Kindle. Book excerpt: * Third edition of a well-known and well established text both in industry and for teaching * Fully up-to-date and includes extra problems This book is an aid to heat exchanger design written primarily for design and development engineers in the chemical process, power generation, and refrigeration industries. It provides a comprehensive reference on two-phase flows, boiling, and condensation. The text covers all the latest advances like flows over tube bundles and two-phase heat transfer regarding refrigerants and petrochemicals. Another feature of this third edition is many new problems at chapter ends to enhance its use as a teaching text for graduate and post-graduate courses on two-phase flow and heat transfer. - ;This book is written for practising engineers as a comprehensive reference on two-phase flows, boiling, and condensation. It deals with methods for estimating two-phase flow pressure drops and heat transfer rates. It is a well-known reference book in its third edition and is also used as a text for advanced university courses. Both authors write from practical experience as both are professional engineers. -
Book Synopsis Flow Boiling in Microgap Channels by : Tamanna Alam
Download or read book Flow Boiling in Microgap Channels written by Tamanna Alam and published by Springer Science & Business Media. This book was released on 2013-08-26 with total page 88 pages. Available in PDF, EPUB and Kindle. Book excerpt: Flow Boiling in Microgap Channels: Experiment, Visualization and Analysis presents an up-to-date summary of the details of the confined to unconfined flow boiling transition criteria, flow boiling heat transfer and pressure drop characteristics, instability characteristics, two phase flow pattern and flow regime map and the parametric study of microgap dimension. Advantages of flow boiling in microgaps over microchannels are also highlighted. The objective of this Brief is to obtain a better fundamental understanding of the flow boiling processes, compare the performance between microgap and conventional microchannel heat sinks, and evaluate the microgap heat sink for instabilities and hotspot mitigation.
Book Synopsis Enhanced Flow Boiling Heat Transfer in Radial Microchannel and Offset Strip Fin Geometries by : Alyssa Recinella
Download or read book Enhanced Flow Boiling Heat Transfer in Radial Microchannel and Offset Strip Fin Geometries written by Alyssa Recinella and published by . This book was released on 2016 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Devices used for various electronic purposes are increasing in power consumption and performance. Due to this growth, the amount of heat dissipated over a small surface area has proportionally continued to increase. Despite previous efforts involving single phase natural and forced convection, these methods are no longer effective in high heat removal. Research in two-phase liquid cooling has become more prominent. Boiling has the potential to yield large critical heat flux values, high heat transfer coefficients and lower pressure drops. Many different surface enhancements and working fluids have been tested to increase efficiency and minimize heat losses. Flow boiling in microchannels have been widely explored in literature for high heat flux dissipation. Microchannels are compact and subsequently easy to manufacture. However, due to flow instabilities that accompany microchannels, different configurations and additional modifications have been explored in order to maximize performance. In this work, a radial geometry is experimentally investigated with a flow inlet over the center of the chip. This central inlet creates a reduction in flow length and therefore a reduction in pressure drop and flow instabilities. Two testing surfaces were explored including a radial microchannel array and a radial offset strip fin array. To maximize performance even further, a gap has been added between the cover plate and testing surface to increase flow area and reduce pressure drop. One significant observation shows that an increase in flow rate mitigates the instabilities seen in the channels and prolongs critical heat flux (CHF). Due to these phenomena, all configurations are tested in the modified configuration with higher flow rates ranging from 120-320 mL/min. Radial microchannels with an added gap yielded maximum performance values of 385.5 W/cm^2 at 42.7°C wall superheat with a high pressure drop of about 140 kPa while the offset strip fin configuration achieved much higher heat transfer performance with CHF values exceeding 900 W/cm^2 at 58.6°C wall superheat. The offset strip fin geometry shows significant performance enhancements compared to the microchannels. For both the gap geometries and the closed geometries, the offset values are much higher than the radial microchannels."--Abstract.
Book Synopsis Fluid Flow, Heat Transfer and Boiling in Micro-Channels by : L. P. Yarin
Download or read book Fluid Flow, Heat Transfer and Boiling in Micro-Channels written by L. P. Yarin and published by Springer Science & Business Media. This book was released on 2008-09-19 with total page 487 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Book Synopsis VDI Heat Atlas by : VDI Gesellschaft
Download or read book VDI Heat Atlas written by VDI Gesellschaft and published by Springer Science & Business Media. This book was released on 2010-07-21 with total page 1608 pages. Available in PDF, EPUB and Kindle. Book excerpt: For more than 50 years, the Springer VDI Heat Atlas has been an indispensable working means for engineers dealing with questions of heat transfer. Featuring 50% more content, this new edition covers most fields of heat transfer in industrial and engineering applications. It presents the interrelationships between basic scientific methods, experimental techniques, model-based analysis and their transfer to technical applications.
Book Synopsis Handbook of Thermal Science and Engineering by :
Download or read book Handbook of Thermal Science and Engineering written by and published by Springer. This book was released on 2018-07-31 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This Handbook provides researchers, faculty, design engineers in industrial R&D, and practicing engineers in the field concise treatments of advanced and more-recently established topics in thermal science and engineering, with an important emphasis on micro- and nanosystems, not covered in earlier references on applied thermal science, heat transfer or relevant aspects of mechanical/chemical engineering. Major sections address new developments in heat transfer, transport phenomena, single- and multiphase flows with energy transfer, thermal-bioengineering, thermal radiation, combined mode heat transfer, coupled heat and mass transfer, and energy systems. Energy transport at the macro-scale and micro/nano-scales is also included. The internationally recognized team of authors adopt a consistent and systematic approach and writing style, including ample cross reference among topics, offering readers a user-friendly knowledgebase greater than the sum of its parts, perfect for frequent consultation. The Handbook of Thermal Science and Engineering is ideal for academic and professional readers in the traditional and emerging areas of mechanical engineering, chemical engineering, aerospace engineering, bioengineering, electronics fabrication, energy, and manufacturing concerned with the influence thermal phenomena.
Book Synopsis Encyclopedia of Two-Phase Heat Transfer and Flow IV by : John R Thome
Download or read book Encyclopedia of Two-Phase Heat Transfer and Flow IV written by John R Thome and published by World Scientific Publishing. This book was released on 2018-05-18 with total page 1372 pages. Available in PDF, EPUB and Kindle. Book excerpt: Set IV is a new addition to the previous Sets I, II and III. It contains 23 invited chapters from international specialists on the topics of numerical modeling of pulsating heat pipes and of slug flows with evaporation; lattice Boltzmann modeling of pool boiling; fundamentals of boiling in microchannels and microfin tubes, CO2 and nanofluids; testing and modeling of micro-two-phase cooling systems for electronics; and various special topics (flow separation in microfluidics, two-phase sensors, wetting of anisotropic surfaces, ultra-compact heat exchangers, etc.). The invited authors are leading university researchers and well-known engineers from leading corporate research laboratories (ABB, IBM, Nokia Bell Labs). Numerous 'must read' chapters are also included here for the two-phase community. Set IV constitutes a 'must have' engineering and research reference together with previous Sets I, II and III for thermal engineering researchers and practitioners.
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 Instability in Flow Boiling in Microchannels by : Sujoy Kumar Saha
Download or read book Instability in Flow Boiling in Microchannels written by Sujoy Kumar Saha and published by Springer. This book was released on 2015-09-14 with total page 63 pages. Available in PDF, EPUB and Kindle. Book excerpt: This Brief addresses the phenomena of instability in flow boiling in microchannels occurring in high heat flux electronic cooling. A companion edition in the SpringerBrief Subseries on Thermal Engineering and Applied Science to “Critical Heat Flux in Flow Boiling in Microchannels,” and "Heat Transfer and Pressure Drop in Flow Boiling in Microchannels,"by the same author team, this volume is idea for professionals, researchers, and graduate students concerned with electronic cooling.
Book Synopsis Handbook of Phase Change by : S.G. Kandlikar
Download or read book Handbook of Phase Change written by S.G. Kandlikar and published by Routledge. This book was released on 2019-01-22 with total page 786 pages. Available in PDF, EPUB and Kindle. Book excerpt: Provides a comprehensive coverage of the basic phenomena. It contains twenty-five chapters which cover different aspects of boiling and condensation. First the specific topic or phenomenon is described, followed by a brief survey of previous work, a phenomenological model based on current understanding, and finally a set of recommended design equa
Book Synopsis Experimental Investigation and Analytical Modeling of Flow Boiling Characteristics in Silicon Microchannel Arrays by : Ayman Megahed
Download or read book Experimental Investigation and Analytical Modeling of Flow Boiling Characteristics in Silicon Microchannel Arrays written by Ayman Megahed and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 Principles of Enhanced Heat Transfer by : Ralph L. Webb
Download or read book Principles of Enhanced Heat Transfer written by Ralph L. Webb and published by Wiley-Interscience. This book was released on 1994-03-28 with total page 584 pages. Available in PDF, EPUB and Kindle. Book excerpt: Indeed, today "second generation" enhancement concepts are routing in the automotive and refrigeration industries to obtain lower cost, smaller heat exchanger size, and higher energy efficiency in system operation. And the aerospace, process, and power generation industries are not far behind.