Two-phase Pressure Drop and Flow Regime of Refrigerants and Refrigerant-oil Mixtures in Small Channels PDF Download
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Author: Brandon S. Field
Publisher: ProQuest
ISBN: 9780549339977
Category :
Languages : en
Pages : 130
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Book Description
As microchannel heat exchangers have become more sophisticated in their design, more exact understanding of the flow inside them is necessary. A decrease in diameter enhances the heat transfer (which takes place at the inner walls of the tubes), but also increases the pressure drop (as the diameter decreases, it becomes like drinking a milkshake through a coffee stirrer). The inclusion of even small amounts of oil in circulation can have a significant effect as well. Historical correlations and studies of two-phase flow have been shown to be insufficient for predicting pressure drops in the smaller channels, due to the different fluid physics that are relevant in flows of small diameter. This study is aimed at understanding the fluid property effects that contribute to pressure drop and flow regime. Two-phase pressure drop data for four refrigerants (R134a, R410A, R290 and R717) were measured in a channel with hydraulic diameter of 148 mum. These data were combined with previous two-phase data of R134a in small channels (hydraulic diameters ranging from 70 to 300 mum) to generate a separated flow model that spans a wide variety of fluid properties. Refrigerant was then mixed with two different viscosities of oil at concentrations ranging from 0.5 to 5% oil, and two-phase pressure drop measurements were taken of those mixtures. Flow visualizations of three of these refrigerants (R134a, R290 and R717) and several concentrations of a R134a-oil mixture were made in a channel with 500 mum hydraulic diameter, and flow regime classifications and comparisons with previous flow maps were made. Finally, a mechanistic description of the two-phase flow that occurs in small channels is put forth, based on the pressure drop measurements and the flow visualizations.
Author: Brandon S. Field
Publisher: ProQuest
ISBN: 9780549339977
Category :
Languages : en
Pages : 130
Get Book Here
Book Description
As microchannel heat exchangers have become more sophisticated in their design, more exact understanding of the flow inside them is necessary. A decrease in diameter enhances the heat transfer (which takes place at the inner walls of the tubes), but also increases the pressure drop (as the diameter decreases, it becomes like drinking a milkshake through a coffee stirrer). The inclusion of even small amounts of oil in circulation can have a significant effect as well. Historical correlations and studies of two-phase flow have been shown to be insufficient for predicting pressure drops in the smaller channels, due to the different fluid physics that are relevant in flows of small diameter. This study is aimed at understanding the fluid property effects that contribute to pressure drop and flow regime. Two-phase pressure drop data for four refrigerants (R134a, R410A, R290 and R717) were measured in a channel with hydraulic diameter of 148 mum. These data were combined with previous two-phase data of R134a in small channels (hydraulic diameters ranging from 70 to 300 mum) to generate a separated flow model that spans a wide variety of fluid properties. Refrigerant was then mixed with two different viscosities of oil at concentrations ranging from 0.5 to 5% oil, and two-phase pressure drop measurements were taken of those mixtures. Flow visualizations of three of these refrigerants (R134a, R290 and R717) and several concentrations of a R134a-oil mixture were made in a channel with 500 mum hydraulic diameter, and flow regime classifications and comparisons with previous flow maps were made. Finally, a mechanistic description of the two-phase flow that occurs in small channels is put forth, based on the pressure drop measurements and the flow visualizations.
Author: Sujoy Kumar Saha
Publisher: Butterworth-Heinemann
ISBN: 0128043563
Category : Science
Languages : en
Pages : 358
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Book Description
Microchannel Heat transfer is the cooling application of high power density microchips in the CPU system, micropower systems and many other large scale thermal systems requiring effective cooling capacity. This book offers the latest research and recommended models on the microsize cooling system which not only significantly reduces the weight load, but also enhances the capability to remove much greater amount of heat than any of large scale cooling systems. A detailed reference in microchannel phase change (boiling and condensation) including recommended models and correlations for various requirements such as pressure loss, and heat transfer coefficient. Researchers, engineers, designers and students will benefit from the collated, state-of-the-art of the research put together in this book and its systematic, addressing all the relevant issues and providing a good reference for solving problems of critical analysis. - Up-to-date information will help delineate further research direction in the microchannel heat transfer - The latest modeling information and recommendations will help in design method and purpose
Author: Satish Kandlikar
Publisher: Butterworth-Heinemann
ISBN: 0080983510
Category : Science
Languages : en
Pages : 588
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Book Description
Heat exchangers with minichannel and microchannel flow passages are becoming increasingly popular due to their ability to remove large heat fluxes under single-phase and two-phase applications. Heat Transfer and Fluid Flow in Minichannels and Microchannels methodically covers gas, liquid, and electrokinetic flows, as well as flow boiling and condensation, in minichannel and microchannel applications. Examining biomedical applications as well, the book is an ideal reference for anyone involved in the design processes of microchannel flow passages in a heat exchanger. - Each chapter is accompanied by a real-life case study - New edition of the first book that solely deals with heat and fluid flow in minichannels and microchannels - Presents findings that are directly useful to designers; researchers can use the information in developing new models or identifying research needs
Author: Volker Hessel
Publisher: John Wiley & Sons
ISBN: 3527315500
Category : Technology & Engineering
Languages : en
Pages : 1413
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Book Description
This three-volume handbook provides an overview of the key aspects of micro process engineering. Volume 1 covers the fundamentals, operations and catalysts, volume 2 examines devices, reactions and applications, with volume 3 rounding off the trilogy with system, process and plant engineering. Fluid dynamics, mixing, heat/mass transfer, purification and separation microstructured devices and microstructured reactors are explained in the first volume. Volume 2 segments microreactor design, fabrication and assembly, bulk and fine chemistry, polymerisation, fuel processing and functional materials into understandable parts. The final volume of the handbook addresses microreactor systems design and scale-up, sensing, analysis and control, chemical process engineering, economic and eco-efficiency analyses as well as microreactor plant case studies in one book. Together, this 3-volume handbook explains the science behind micro process engineering to the scale-up and their real life industrial applications.
Author: Vasile Minea
Publisher: CRC Press
ISBN: 0429874065
Category : Science
Languages : en
Pages : 705
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Book Description
This book discusses conventional as well as unconventional wood drying technologies. It covers fundamental thermophysical and energetic aspects and integrates two complex thermodynamic systems, conventional kilns and heat pumps, aimed at improving the energy performance of dryers and the final quality of dried lumber. It discusses advanced components, kiln energy requirements, modeling, and software and emphasizes dryer/heat pump optimum coupling, control, and energy efficiency. Problems are included in most chapters as practical, numerical examples for process and system/components calculation and design. The book presents promising advancements and R&D challenges and future requirements.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 19
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Book Description
Two-phase flow pressure drop measurements were made during a phase-change heat transfer process with three refrigerants (R-134a, R-12, and R-113) at six different pressures ranging from 138 kPa to 856 kPa, and in two sizes of round tubes (2.46 mm and 2.92 mm inside diameters) and one rectangular channel (4.06 x 1.7 mm). State-of-the-art large-tube correlations failed to satisfactorily predict the experimental data. The data were used to develop a new correlation for two-phase pressure drop during flow boiling in small channels. The correlation was then tested against the experimental data for the three refrigerants; the error was "20%.
Author: Mirza Mohammed Shah
Publisher: John Wiley & Sons
ISBN: 1119618673
Category : Science
Languages : en
Pages : 388
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Book Description
A guide to two-phase heat transfer theory, practice, and applications Designed primarily as a practical resource for design and development engineers, Two-Phase Heat Transfer contains the theories and methods of two-phase heat transfer that are solution oriented. Written in a clear and concise manner, the book includes information on physical phenomena, experimental data, theoretical solutions, and empirical correlations. A very wide range of real-world applications and formulas/correlations for them are presented. The two-phase heat transfer systems covered in the book include boiling, condensation, gas-liquid mixtures, and gas-solid mixtures. The authora noted expert in this fieldalso reviews the numerous applications of two-phase heat transfer such as heat exchangers in refrigeration and air conditioning, conventional and nuclear power generation, solar power plants, aeronautics, chemical processes, petroleum industry, and more. Special attention is given to heat exchangers using mini-channels which are being increasingly used in a variety of applications. This important book: Offers a practical guide to two-phase heat transfer Includes clear guidance for design professionals by identifying the best available predictive techniques Reviews the extensive literature on heat transfer in two-phase systems Presents information to aid in the design and analysis of heat exchangers. Written for students and research, design, and development engineers, Two-Phase Heat Transfer is a comprehensive volume that covers the theory, methods, and applications of two-phase heat transfer.
Author: Sujoy Kumar Saha
Publisher: Springer
ISBN: 3319202855
Category : Science
Languages : en
Pages : 63
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Book Description
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.
Author: Junjie Gu
Publisher: Springer Science & Business Media
ISBN: 1461483239
Category : Science
Languages : en
Pages : 167
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Book Description
Two-Phase Flow in Refrigeration Systems presents recent developments from the authors' extensive research programs on two-phase flow in refrigeration systems. This book covers advanced mass and heat transfer and vapor compression refrigeration systems and shows how the performance of an automotive air-conditioning system is affected through results obtained experimentally and theoretically, specifically with consideration of two-phase flow and oil concentration. The book is ideal for university postgraduate students as a textbook, researchers and professors as an academic reference book, and by engineers and designers as handbook.
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.
