Download or read book Time Periodic Flow Boiling Heat Transfer and Associated Bubble Characteristics of Refrigerant R 134a in a Horizontal Annular Duct Due to Flow Rate Or Heat Flux Oscillation written by and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Issues in Mechanical Engineering 2011 Edition written by and published by ScholarlyEditions. This book was released on 2012-01-09 with total page 2526 pages. Available in PDF, EPUB and Kindle. Book excerpt: Issues in Mechanical Engineering / 2011 Edition is a ScholarlyEditions™ eBook that delivers timely, authoritative, and comprehensive information about Mechanical Engineering. The editors have built Issues in Mechanical Engineering: 2011 Edition on the vast information databases of ScholarlyNews.™ You can expect the information about Mechanical Engineering in this eBook to be deeper than what you can access anywhere else, as well as consistently reliable, authoritative, informed, and relevant. The content of Issues in Mechanical Engineering: 2011 Edition has been produced by the world’s leading scientists, engineers, analysts, research institutions, and companies. All of the content is from peer-reviewed sources, and all of it is written, assembled, and edited by the editors at ScholarlyEditions™ and available exclusively from us. You now have a source you can cite with authority, confidence, and credibility. More information is available at http://www.ScholarlyEditions.com/.
Download or read book An Experimental Investigation on the Dynamics of Bubbles Utilizing Refrigerant R134a Under Pressurized Flow Boiling Conditions written by Keon Vereen and published by . This book was released on 2011 with total page 115 pages. Available in PDF, EPUB and Kindle. Book excerpt: Flow boiling heat transfer allows for the dissipation of large amounts of heat. In this work, the effect of heat flux and pressure on flow boiling of liquid refrigerant R-134a is studied in a vertical thin channel. The experimental setup mimics a refrigeration cycle and specifically looks at the effect of pressure and wall heat flux on the departure size and bubble generation rate. The experimental setup consists of a closed loop which includes a vertical narrow rectangular channel and two synchronized high speed cameras for optical measurements at either sides of the channel. The setup is built to employ an accurate measurement technique to define wall temperatures of the representative flow boiling process. Instead of using thermocouples on the surface channel, the thermochromic liquid crystallography (TLC) technique is used to determine non-invasively the heater surface temperature at high temporal and spatial resolution. The TLC interval range is 30-50°C. The TLC is attached to a Fecralloy heating section. The high speed Prosilica cameras simultaneously capture, colored TLC images as well as bubble nucleation and departure at very high frame rates. Experiments on subcooled flow boiling heat transfer have been conducted with refrigerant R-134a under a mass flux range of 484.838 kg/m2s to 1212.1 kg/m2s. With the low mass flux, the wall heat flux ranged from 167.2 to 672.1 kW/m2, the inlet subcooling ranged from 0.35°C to 16.55°C, the system pressure ranged from 621 kPa to 1034 kPa. At high mass flux, the wall heat flux ranged from 329.8 kW/m2 to 744 kW/m2, the inlet subcooling from 0.16°C to 17.21°C, and the system pressure from 621 kPa to 1034 kPa. A parametric study was done by maintaining various input parameters constant. From the high speed images, bubble parameters such as size and frequency are calculated. Temperature contours are utilized to determine the surface wall temperature at specific points. Sequential wall temperatures are traced over a short period of time to understand the cooling effects. The bubble propagation and coalescence are also visualized. Results show that bubble size and frequency increased with heat flux at any particular pressure. At higher pressure, the trend would be for the bubble size to decrease; however, the inlet subcooling and heat flux also affect bubble size. The bubble frequency is also seen to be affected by the inlet subcooling and the heat flux. Even though the inlet subcooling is maintained approximately constant, any slight decrease in subcooling increased bubble growth rate. Another trend that is observed is that at higher the heat flux, the bubble generation frequency is faster; however no specific trend is observed for wall superheat. With an increase in heat flux, the wall superheats are expected to increase; however, the localized nature of the nucleation activity sites is seen to affect the results. The variables are non-dimensionalized to note trends in parameters. In summary, the data analysis demonstrates that both heat flux and pressure significantly influence the bubble generation rate, size, propagation and coalescence.
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
Download or read book Horizontal Nucleate Flow Boiling Heat Transfer Coefficient Measurements and Visual Observations for R12 R134a and R134a Ester Lubricant Mixtures written by Mark A. Kedzierski and published by . This book was released on 1993 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt: The heat transfer characteristics of horizontal nucleate flow boiling of R12, R134a, and R134a/Ester Lubricant mixtures were investigated both visually and calorimetrically. The effect of two different ester lubricants on the boiling characteristics of R134a were investigated. The test refrigerant entered a roughened quartz tube test section slightly above the saturated state. Both the heat flux and the Reynolds number were varied in order to investigate their effect on the heat transfer coefficient. The heat transfer increased nearly proportionally with an increase in the heat flux. An increase in the Reynolds number caused a marginal increase in the heat transfer coefficient. Locally measured heat transfer coefficients were taken simultaneously with high speed motion picture images of the boiling process. The motion pictures were used to obtain a descriptive behavior of the boiling which was compared directly to the measured heat transfer coefficients. The rate of bubble production for pure R134a was 38 % greater than that of R12. This is the most likely reason that the R134a heat transfer coefficient was approximately 20% greater than that of R12. The addition of lubricant to R134a caused a drastic reduction in the diameter of the bubbles. In fact, for one R134a/lubricant mixture, the bubbles were emitted from the surface as a mist. The addition of the low viscosity lubricant to R134a enhanced the heat transfer of R134a. For Reynolds numbers above 8000, the addition of the high viscosity lubricant degraded the heat transfer as compared to that of the pure component. A mechanistic explanation for the observed R134a/ lubricant boiling is provided.
Download or read book Horizontal Convective Boiling of R134a R1234yf r134a and R1234ze e Within a Micro fin Tube With Extensive Measurement and Analysis Details written by National Institute of Standards and Technology and published by CreateSpace. This book was released on 2014-02 with total page 62 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report presents local convective boiling measurements in a micro-fin tube for R134a and two low global warming potential (GWP ) refrigerants: R1234yf/ R134a, 56/44 % mass and R1234ze(E). Water heating either in counterflow or in parallel flow with the test refrigerant was used to vary the heat flux for a given quality. The heat transfer coefficient of the three test fluids were compared at the same heat flux, saturated refrigerant temperature, and refrigerant mass flux using an existing correlation from the literature. The resulting comparison showed that refrigerant R134a exhibited the highest heat transfer performance in large part due to its higher thermal conductivity as compared to the tested low-GWP refrigerants. For the example case presented here, the heat transfer coefficient for R1234yf/ R134a (56/44) remains within 5 % of the heat transfer coefficient for R134a, having essentially identical performance for qualities less than 30 %. The heat transfer coefficient for R1234ze(E) is roughly 700 kW, K-1, m-2 (approximately 14 %) less than that of R134a for qualities greater than 30 %. The smaller heat transfer coefficient of R1234ze(E) as compared to that of R134a is primarily due to the 11 % smaller thermal conductivity and the 21 % smaller reduced pressure as compared to R134a at this test temperature. The measurements are important as part of the evaluation of low-GWP replacement refrigerants for R134a in unitary refrigeration and air-conditioning equipmen
Download or read book Heat Transfer Characteristics for Flow Boiling of R134a in Horizontal Circular Microtubes written by Saptarshi Basu and published by . This book was released on 2009 with total page 246 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Boiling Condensation and Gas liquid Flow written by P. B. Whalley and published by Oxford University Press, USA. This book was released on 1987 with total page 316 pages. Available in PDF, EPUB and Kindle. Book excerpt: Heat transfer phenomena involving boiling and condensation are an important aspect of engineering in the power and process industries. This book, aimed at final year undergraduates and graduate students in mechanical or chemical engineering, deals with these phenomena in detail.
Download or read book Two phase Flow and Heat Transfer written by David Butterworth and published by . This book was released on 1979 with total page 514 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Characterization of Bubble Entrainment Interfacial Roughness and the Sliding Bubble Mechanism in Horizontal Annular Flow written by Daniel J. Rodríguez and published by . This book was released on 2004 with total page 242 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Flow Boiling of Pure Refrigerants and Binary Refrigerant Mixtures in a Horizontal Tube written by Ali A. Rabah and published by . This book was released on 2003 with total page 187 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Pool Boiling of R 134a and R 123 on Smooth and Enhanced Tubes written by and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This project studied the pool boiling of R-134a and R-123 on smooth and enhanced tubes. This is the 1st phase of ASHRAE project RP-1316 "Experimental Evaluation of The Heat Transfer Impacts of Tube Pitch in a Highly Enhanced Surface Tube Bundle". A Turbo BII-HP and a Turbo BII-LP enhanced tubes were used in this study. These tubes were manufactured and donated by Wolverine Tube, Inc. Four different boiling cases were tested, R-134a on smooth tube, R-123 on smooth tube, R-134a on Turbo BII-HP tube, and R-123 on Turbo BII-LP tube. The first step in this study was performing a modified Wilson plot analysis, once completed, the average and local refrigerant heat transfer coefficients were determined. This thesis also presents the enthalpy-based heat transfer analysis (EBHT), a new method for determining the heat exchanger's overall heat transfer coefficient as a function of the enthalpy change of incompressible fluids. The test tubes' outer diameter is 19.05 mm and length is 1 m. Tests were conducted in a single tube test section, in which the test tube was water heated. All tests were conducted at a saturation temperature of 4.44 °C. The heat flux range is 9.2-126.6 kW/m[superscript]2 for testing with R-134a on smooth tube, 9.2-58 kW/m[superscript]2 for R-123 on smooth tube, 4.1-135.1 kW/m[superscript]2 for R-134a on Turbo BII-HP tube and 4.7-59.8 kW/m[superscript]2 for R-123 on Turbo BII-LP tube. Results show that the heat transfer coefficient increases with heat flux for all cases except the case of R-134a on Turbo BII-HP tube, where it experiences a trend change. Part of this study was comparing the smooth and enhanced tubes performances. R-134a Turbo BII-HP tube to smooth tube heat transfer coefficient ratio changes from 4 at low heat flux to 1.7 at high heat flux. R-123 Turbo BII-LP tube to smooth tube heat transfer coefficient ratio changes from 24 at low heat flux to 7 at high heat flux. The performance of Turbo BII-HP and Turbo BII-LP was found to be very similar over the tested heat flux range of the Turbo BII-LP tube. Comparison plots with available literature are presented.
Download or read book Oscillating Heat Pipes written by Hongbin Ma and published by Springer. This book was released on 2015-05-22 with total page 441 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents the fundamental fluid flow and heat transfer principles occurring in oscillating heat pipes and also provides updated developments and recent innovations in research and applications of heat pipes. Starting with fundamental presentation of heat pipes, the focus is on oscillating motions and its heat transfer enhancement in a two-phase heat transfer system. The book covers thermodynamic analysis, interfacial phenomenon, thin film evaporation, theoretical models of oscillating motion and heat transfer of single phase and two-phase flows, primary factors affecting oscillating motions and heat transfer, neutron imaging study of oscillating motions in an oscillating heat pipes, and nanofluid’s effect on the heat transfer performance in oscillating heat pipes. The importance of thermally-excited oscillating motion combined with phase change heat transfer to a wide variety of applications is emphasized. This book is an essential resource and learning tool for senior undergraduate, graduate students, practicing engineers, researchers, and scientists working in the area of heat pipes. This book also · Includes detailed descriptions on how an oscillating heat pipe is fabricated, tested, and utilized · Covers fundamentals of oscillating flow and heat transfer in an oscillating heat pipe · Provides general presentation of conventional heat pipes
Download or read book Pressure Drop and Heat Transfer Characteristics of Refrigerant 114 Boiling in a Horizontal Tube written by William R. Brock and published by . This book was released on 1977 with total page 293 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Rules of Thumb for Chemical Engineers written by Carl Branan and published by Gulf Professional Publishing. This book was released on 2002 with total page 438 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fractionators, separators and accumulators, cooling towers, gas treating, blending, troubleshooting field cases, gas solubility, and density of irregular solids * Hundreds of common sense techniques, shortcuts, and calculations.
Download or read book Two phase Pressure Drops written by Herbert Stanford Isbin and published by . This book was released on 1954 with total page 100 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Industrial Gas Handbook written by Frank G. Kerry and published by CRC Press. This book was released on 2007-02-22 with total page 552 pages. Available in PDF, EPUB and Kindle. Book excerpt: Drawing on Frank G. Kerry's more than 60 years of experience as a practicing engineer, the Industrial Gas Handbook: Gas Separation and Purification provides from-the-trenches advice that helps practicing engineers master and advance in the field. It offers detailed discussions and up-to-date approaches to process cycles for cryogenic separation of
