A Study of Sintered Copper Porous Surfaces for Pool Boiling Enhancement PDF Download
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Author: Felix Liu
Publisher:
ISBN:
Category : Ebullition
Languages : en
Pages : 146
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Book Description
"Miniaturization in microelectronics demands effective thermal management from high energy density devices. While current cooling solutions employ single-phase heat transfer, they are often limited by high fluid temperature differences and pressure drops. Alternatively, two-phase cooling schemes offers attractive solutions to dissipate high heat fluxes at small temperature differences. Specifically, pool boiling has the potential to dissipate high heat fluxes without using pumps and other complex header configurations. Two performance criterion that govern the heat transfer in pool boiling systems are the (i) Critical Heat Flux (CHF), and the (ii) Heat Transfer Coefficient. The CHF is the upper limit in nucleate boiling, while the Heat Transfer Coefficient dictates the efficiency of the process. The current thesis work relates to increasing the aforementioned parameters through copper porous coatings. In this work, copper substrates were coated with 3M copper powders using a drop coating and screen printing technique. Substrate bonding was achieved by sintering at elevated temperatures. The coated substrates were characterized using Scanning Electron Microscopy and Laser Confocal Microscopy which revealed the different geometrical parameters (pore sizes and coating thickness etc.) associated with the coatings. Pool boiling tests were conducted with distilled and degassed water at atmospheric pressure. A highest Critical Heat Flux (CHF) of 303 W/cm2 was obtained on a test sample corresponding to a coating thickness of 447 μm. This translated to a CHF enhancement of ~135 % when compared to a plain copper surface. The effect of coating thickness on pool boiling performance was studied. High speed visualization was conducted on the test samples to identify underlying boiling mechanisms. The effect of additional nucleation sites, and wickability were evaluated in this study. The experimental observations were supplemented with analytical equations available in literature to identify driving mechanisms with the thin and thick porous coatings."--Abstract.
Author: Felix Liu
Publisher:
ISBN:
Category : Ebullition
Languages : en
Pages : 146
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Book Description
"Miniaturization in microelectronics demands effective thermal management from high energy density devices. While current cooling solutions employ single-phase heat transfer, they are often limited by high fluid temperature differences and pressure drops. Alternatively, two-phase cooling schemes offers attractive solutions to dissipate high heat fluxes at small temperature differences. Specifically, pool boiling has the potential to dissipate high heat fluxes without using pumps and other complex header configurations. Two performance criterion that govern the heat transfer in pool boiling systems are the (i) Critical Heat Flux (CHF), and the (ii) Heat Transfer Coefficient. The CHF is the upper limit in nucleate boiling, while the Heat Transfer Coefficient dictates the efficiency of the process. The current thesis work relates to increasing the aforementioned parameters through copper porous coatings. In this work, copper substrates were coated with 3M copper powders using a drop coating and screen printing technique. Substrate bonding was achieved by sintering at elevated temperatures. The coated substrates were characterized using Scanning Electron Microscopy and Laser Confocal Microscopy which revealed the different geometrical parameters (pore sizes and coating thickness etc.) associated with the coatings. Pool boiling tests were conducted with distilled and degassed water at atmospheric pressure. A highest Critical Heat Flux (CHF) of 303 W/cm2 was obtained on a test sample corresponding to a coating thickness of 447 μm. This translated to a CHF enhancement of ~135 % when compared to a plain copper surface. The effect of coating thickness on pool boiling performance was studied. High speed visualization was conducted on the test samples to identify underlying boiling mechanisms. The effect of additional nucleation sites, and wickability were evaluated in this study. The experimental observations were supplemented with analytical equations available in literature to identify driving mechanisms with the thin and thick porous coatings."--Abstract.
Author: Smreeti Dahariya
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Boiling has received considerable attention in the technology advancement of electronics cooling for high-performance computing applications. Two-phase cooling has an advantage over a single-phase cooling in the high heat removal rate with a small thermal gradient due to the latent heat of vaporization. Many surface modifications have been done in the past including surface roughness, mixed wettability and, porous wick copper play a crucial role in the liquid-vapor phase change heat transfer. However, the mechanisms of high-pressure pool-boiling heat transfer enhancement due to surface modifications has not been well studied or understood. The properties of water, such as the latent heat of vaporization, surface tension, the difference in specific volume of liquid and vapor, decrease at high-pressure. High-pressure pool-boiling heat transfer enhancement is studied fundamentally on various engineered surfaces. The boiling tests are performed at a maximum pressure of 90 psig (620.5 kPa) and then compared to results at 0 psig (0 kPa). The results indicate that the pressure influences the boiling performance through changes in bubble dynamics. The bubble departure diameter, bubble departure frequency, and the active nucleation sites change with pressure. The pool-boiling heat transfer enhancement of a Teflon© coated surface is also experimentally tested, using water as the working fluid. The boiling results are compared with a plain surface at two different pressures, 30 and 45 psig. The maximum heat transfer enhancement is found at the low heat fluxes. At high heat fluxes, a negligible effect is observed in HTC. The primary reasons for the HTC enhancement at low heat fluxes are active nucleation sites at low wall superheat and bubble departure size. The Teflon© coated surface promotes nucleation because of the lower surface energy requirement. The boiling results are also obtained for wick surfaces. The wick surfaces are fabricated using a sintering process. The boiling results are compared with a plain surface. The reasons for enhancements in the pool-boiling performance are primarily due to increased bubble generation, higher bubble release frequency, reduced thermal-hydraulic length modulation, and enhanced thermal conductivity due to the sintered wick layer. The analysis suggests that the Rayleigh-critical wavelength decreases by 4.67 % of varying pressure, which may cause the bubble pinning between the gaps of sintered particles and avoids the bubble coalescence. Changes in the pitch distance indicate that a liquid-vapor phase separation happens at the solid/liquid interface, which impacts the heat-transfer performance significantly. Similarly, the role of the high-pressure over the wicking layer is further analyzed and studied. It is found that the critical flow length, [lambda]u reduces by three times with 200 [mu]m particles. The results suggest that the porous wick layer provides a capillary-assist to liquid flow effect, and delays the surface dry out. The surface modification and the pressure amplify the boiling heat transfer performance. All these reasons may contribute to the CHF, and HTC enhancement in the wicking layer at high-pressure.
Author: N. Zuber
Publisher:
ISBN:
Category : Heat
Languages : en
Pages : 216
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Book Description
Author: Joo Han Kim
Publisher:
ISBN: 9780542979903
Category : Mechanical engineering
Languages : en
Pages :
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Book Description
The present research is an experimental study of the enhancement of boiling heat transfer using microporous coating techniques. The current research is divided into four major phases. During the first phase, the effects of different metal particle sizes in the coating compound for thermally non-conductive microporous coating on pool boiling performance of refrigerants and water are investigated. The test surfaces were solid copper blocks with 1-cm2 base at atmospheric pressure in saturated FC-72, R-123, and water. Results showed that the surface treatment by non-conductive microporous coating significantly enhanced both nucleate boiling and critical heat flux of FC-72 and R-123. However, the enhancement of boiling performance for water was merely shown. In the second phase, thermally conductive microporous coatings to enhance boiling performance of water were developed. The first phase motivated efforts to fabricate microporous coatings with conducting binder options. The second phase was stemmed from an effort to combine the advantages of both a mixture batch type (inexpensive & easy process) and sintering/machining method (low thermal resistance of conduction). Two categories of surface treatment processes were considered in the current research. The first can be achieved by a chemical process, Multi-Staged Electroplating (MSE), which uses electricity in a chemical bath to deposit a microporous structure on the surface. The second is a soldering process, Multi-Temperature Soldering Process (MTSP), which binds the metal particles to generate optimum microporous cavities. Scanning Electron Microscope (SEM) and optical microscope images were obtained for thermally conductive microporous coated surfaces. During the third phase, the pool boiling performance of developed MSE and MTSP from second phase was confirmed for water. Results showed that the MSE and MTSP augmented the boiling performance not only for refrigerants but also for water significantly compared to non-conductive microporous coatings. Further investigation for possible future industrial applications of microporous coatings, such as indirect cooling for electronic chips, nanofluids for high power generation industries, and freezing problem of water, were conducted in the final phase.
Author: Ephraim M. Sparrow
Publisher: Academic Press
ISBN: 0323850820
Category : Technology & Engineering
Languages : en
Pages : 414
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Book Description
Advances in Heat Transfer, Volume 53 in this long-running serial, highlights new advances in the field, with this new volume presenting interesting chapters written by an international board of authors. Provides the authority and expertise of leading contributors from an international board of authors Presents the latest release in the Advances in Heat Transfer series
Author: Igor Pioro
Publisher: BoD – Books on Demand
ISBN: 1803562935
Category : Science
Languages : en
Pages : 164
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Book Description
Advances in Boiling and Condensation provides a comprehensive overview of boiling and condensation, which are two types of convection heat transfer with phase change. Written by experts in the field, the book includes five chapters that address such topics as nucleate pool boiling and flow boiling, heat transfer and hydraulic resistance in fuel bundles of nuclear-power reactors, boiling heat-transfer enhancement with graphene-based functional coatings, water hammer in two-phase systems, and heat transfer during condensation.
Author:
Publisher: Springer
ISBN: 9783319266947
Category : Science
Languages : en
Pages : 0
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Book Description
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.
Author: John R Thome
Publisher: World Scientific
ISBN: 9813227427
Category : Technology & Engineering
Languages : en
Pages : 1460
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Book Description
Set III of this encyclopedia is a new addition to the previous Sets I and II. It contains 26 invited chapters from international specialists on the topics of numerical modeling of two-phase flows and evaporation, fundamentals of evaporation and condensation in microchannels and macrochannels, development and testing of micro two-phase cooling systems for electronics, and various special topics (surface wetting effects, microfin tubes, two-phase flow vibration across tube bundles). The chapters are written both by renowned university researchers and by well-known engineers from leading corporate research laboratories. Numerous 'must read' chapters cover the fundamentals of research and engineering practice on boiling, condensation and two-phase flows, two-phase heat transfer equipment, electronics cooling systems, case studies and so forth. Set III constitutes a 'must have' reference together with Sets I and II for thermal engineering researchers and practitioners.
Author: Sujoy Kumar Saha
Publisher: Springer
ISBN: 3030207552
Category : Science
Languages : en
Pages : 121
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Book Description
This Brief concerns heat transfer and pressure drop in heat transfer enhancement for boiling and condensation. The authors divide their topic into six areas: abrasive treatment and coatings, combined structured and porous surfaces, basic principles of boiling mechanism, vapor space condensation, convective vaporization, and forced condensation inside tubes. Within this framework, the book examines range of specific phenomena including abrasive treatment, open grooves, 3D cavities, etched surfaces, electroplating, pierced 3D cover sheets, attached wire and screen promoters, non-wetting coatings, oxide and ceramic coatings, porous surfaces, structured surfaces (integral roughness), combined structured and porous surfaces, composite surfaces, single-tube pool boiling tests, theoretical fundamentals like liquid superheat, effect of cavity shape and contact angle on superheat, entrapment of vapor in cavities, nucleation at a surface cavity, effect of dissolved gases, bubble departure diameter, bubble dynamics, boiling hysteresis and orientation effects, basic principles of boiling mechanism, visualization and mechanism of boiling in subsurface tunnels, and Chien and Webb parametric boiling studies.
Author: Mehmet Arik
Publisher:
ISBN:
Category :
Languages : en
Pages : 462
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Book Description
