› › Enhanced Pool Boiling Of Water With Open Microchannels Over Cylindrical Tubes

Enhanced Pool Boiling of Water with Open Microchannels Over Cylindrical Tubes

Author : Jeet S. Mehta

Publisher :

Page : 222 pages

File Size : 30,77 MB

Release : 2013

Category : Heat-transfer media

ISBN :

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Book Description

"Pool boiling is a stable and efficient method for transferring large quantities of heat. It is employed in a wide range of applications, including steam generation in boilers, petrochemical, pharmaceutical, cryogenic and many other industrial processes. The objective of this work was to investigate the augmentation in the boiling heat transfer rates with an array of open microchannels over a cylindrical tube. In order to develop high performance surfaces, rectangular and V-groove cross-sectional geometry microchannels were fabricated and tested over tubular test sections. These microchannels were manufactured in two configurations: circumferentially around the test section and axially along the length. The effects of the microchannel geometric parameters on pool boiling performance were studied under horizontal and vertical orientations. Twenty uniquely modified microchannel surfaces were designed, fabricated and tested. The best performance was obtained with a circumferential rectangular microchannel test section in the horizontal orientation. A maximum heat transfer coefficient of 129 kW/m2*K was achieved at a heat flux of 1095 kW/m2, while maintaining a wall superheat of 8.5 K. The overall enhancement factors obtained at the maximum heat flux condition, ranged between 1.9 and 3.4 in the horizontal orientation, and 2.1 and 3.1 in the vertical orientation. The critical heat flux for almost all the designed test surfaces was increased by a factor of at least 1.6 over a plain tube. Area normalized results indicated that factors other than area enhancement are responsible for augmenting the heat transfer performance. High-speed videography of bubbles nucleating, growing and departing from the heated surface was performed. The bubble behavior over these open microchannels was analyzed to understand the fundamental mechanism during pool boiling. The bubble interactions in and over the open microchannels, and the liquid rewetting phenomenon greatly influence the heat transfer performance for these surface."--Abstract.



Pool Boiling Enhancement Through Improved Liquid Supply Pathways Over Open Microchannels

Author : Arvind Jaikumar

Publisher :

Page : 158 pages

File Size : 47,15 MB

Release : 2014

Category : Ebullition

ISBN :

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Book Description

"Boiling is an efficacious mode of heat transfer and is utilized in various energy conversions, heat exchange systems and in cooling of high energy density electronic components. Fundamental pool boiling mechanisms suggest that liquid rewetting on a heated surface is a key factor in delaying critical heat flux (CHF) for enhancing pool boiling performance. In this study, pool boiling enhancement is achieved by providing improved liquid supply pathways to nucleation sites in open microchannels. A two part study is conducted to enhance pool boiling performance of open microchannels. Micromachined and porous surfaces are identified as enhancement techniques in Part-I and Part-II respectively. The results obtained in part-I showed significant improvement in the pool boiling performance when tested with water and FC-87. In part-II of the study, porous coatings are deposited on the boiling surface of an open parallel microchannel fin tops, channel bottoms and both, and individually investigated for their pool boiling performance. The best performing surface was with porous coatings throughout the geometry and had a CHF of 313 W/cm2 at a wall superheat of 7.5 °C. High speed images for the three surfaces show that bubble nucleation occurred at the location of porous deposits. Furthermore, additional nucleation sites are identified as the main contributing factor in the best performing surface which had an enhancement of 150% in CHF when compared to a plain surface. Efficient liquid recirculation provided by open microchannels also contributed to improved microconvection in the channels."--Abstract.



Technologies for Sustainable Development

Author : Alka Mahajan

Publisher : CRC Press

Page : 556 pages

File Size : 32,62 MB

Release : 2022-02-14

Category : Technology & Engineering

ISBN : 1000172228

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Book Description

This volume contains a selection of papers presented at the 7th Nirma University International Conference on Engineering ‘NUiCONE 2019’. This conference followed the successful organization of four national conferences and six international conferences in previous years. The main theme of the conference was “Technologies for Sustainable Development”, which is in line with the “SUSTAINABLE DEVELOPMENT GOAL” established by the United Nations. The conference was organized with many inter-disciplinary technical themes encompassing a broad range of disciplines and enabling researchers, academicians and practitioners to choose between ideas and themes. Besides, NUiCONE-2019 has also presented an exciting new set of events to engage practicing engineers, technologists and technopreneurs from industry through special knowledge sharing sessions involving applied technical papers based on case-study applications, white-papers, panel discussions, innovations and technology products. This proceedings will definitely provide a platform to proliferate new findings among researchers. Advances in Transportation Engineering Emerging Trends in Water Resources and Environmental Engineering Construction Technology and Management Concrete and Structural Engineering Futuristic Power System Control of Power Electronics Converters, Drives and E-mobility Advanced Electrical Machines and Smart Apparatus Chemical Process Development and Design Technologies and Green Environment Sustainable Manufacturing Processes Design and Analysis of Machine and Mechanism Energy Conservation and Management Advances in Networking Technologies Machine Intelligence / Computational Intelligence Autonomic Computing Control and Automation Electronic Communications Electronics Circuits and System Design Signal Processing





Handbook of Thermal Science and Engineering

Author :

Publisher : Springer

Page : 0 pages

File Size : 40,4 MB

Release : 2018-07-31

Category : Science

ISBN : 9783319266947

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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.



VDI Heat Atlas

Author : VDI Gesellschaft

Publisher : Springer Science & Business Media

Page : 1608 pages

File Size : 14,93 MB

Release : 2010-07-21

Category : Science

ISBN : 3540778764

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Book Description

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.



Heat Transfer and Fluid Flow in Minichannels and Microchannels

Author : Satish Kandlikar

Publisher : Elsevier

Page : 492 pages

File Size : 18,4 MB

Release : 2006

Category : Science

ISBN : 9780080445274

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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.



Pool Boiling from Enhanced Structures Under Confinement

Author : Camil-Daniel Ghiu

Publisher :

Page : pages

File Size : 43,56 MB

Release : 2007

Category : Ebullition

ISBN :

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Book Description

A study of pool boiling of a dielectric liquid (PF 5060) from single-layered enhanced structures was conducted. The parameters investigated were the heat flux, the width of the microchannels and the microchannel pitch. The boiling performance of the enhanced structures increases with increase in channel width and decrease in channel pitch. Simple single line curve fits are provided as a practical way of predicting the data over the entire nucleate boiling regime. The influence of confinement on the thermal performance of the enhanced structures was also assessed. The main parameter investigated was the top space (0 mm 3{13 mm). High-speed visualization was used as a tool . For the total confinement (= 0 mm), the heat transfer performance of the enhanced structures was found to depend weakly on the channel width. For>0 mm, the enhancement observed for plain surfaces in the low heat fluxes regime is not present for the present enhanced structure. The maximum heat flux for a prescribed 85 °C surface temperature limit increased with the increase of the top spacing, similar to the plain surfaces case. Two characteristic regimes of pool boiling have been identified and described: isolated flattened bubbles regime and coalesced bubbles regime. A semi-analytical predictive model applicable to pool boiling under confinement is developed. The model requires a limited number of empirical constants and is capable of predicting the experimental heat flux within 30%.



Experimental Investigation of Pool Boiling Performance with Ethanol and FC-87 on Open Microchannel Surfaces

Author : Ankit Kalani

Publisher :

Page : 170 pages

File Size : 27,46 MB

Release : 2012

Category : Heat sinks (Electronics)

ISBN :

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Book Description

"The growing trend in miniaturization of electronics has generated a need for efficient thermal management of these devices. Boiling has the ability to dissipate large quantity of heat while maintaining a small temperature difference. Vapor chamber with pool boiling offers an effective way to provide cooling and maintaining temperature uniformity. The objective of the current work is to investigate pool boiling performance of ethanol and FC-87 on microchannel surfaces. Ethanol is an attractive working fluid due to its better heat transfer performance and higher heat of vaporization compared to refrigerants, and lower boiling point compared to water. The saturation temperature of ethanol can be further reduced to temperatures suitable for electronics cooling by lowering the system pressure. Fluorocarbons are considered to be ideal fluids for electronics cooling due to their low normal boiling point, dielectric and inert nature. FC-87 is selected for the current work. Ethanol is tested at four different absolute pressures, 101.3 kPa, 66.7 kPa, 33.3 kPa and 16.7 kPa using different microchannel surface configurations. Heat dissipation in excess of 900 kW/m2 was obtained while maintaining the wall surface below 85°C at 33 kPa. Flammability, toxicity and temperature overshoot issues need to be addressed before practical implementation of ethanol-based cooling systems in electronics cooling application. FC-87 with microchannel yields average performance when compared to literature. Effect of surface area is identified as the key reason for performance enhancement. A new finned structure is developed, which gave a heat flux value 1.25 MW/m2 at 40°C wall superheat for FC-87 at atmospheric conditions."--Abstract.



Handbook of Phase Change

Author : S.G. Kandlikar

Publisher : Routledge

Page : 786 pages

File Size : 18,79 MB

Release : 2019-01-22

Category : Science

ISBN : 1351442198

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Book Description

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