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 Publications of the National Institute of Standards and Technology Catalog written by National Institute of Standards and Technology (U.S.) and published by . This book was released on 1994 with total page 1162 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Experimental Investigation of Nucleate Boiling Bubble Dynamics in Normal and Zero Gravities written by Thomas H. Cochran and published by . This book was released on 1968 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Experiments in Pool Boiling Heat Transfer and Nucleation Dynamics of High Pressure Refrigerants written by Daniel Joo and published by . This book was released on 2006 with total page 71 pages. Available in PDF, EPUB and Kindle. Book excerpt: A high pressure pool boiling experiment of pressurized R134a is designed and built, utilizing thermochromatic liquid crystal techniques. Liquid crystals thermo-chromatography uses encapsulated liquid crystals that are sensitive to temperature. When exposed to hot temperatures the crystal reflect a blue/violet color, and when exposed to cooler temperatures it reflects a red/orange color. The color value or hue is proportional to its temperature. Using this technique this experiment is capable of studying the physics and thermodynamics of refrigerants under nucleate pool boiling.
Download or read book Bulletin de L Institut International Du Froid written by and published by . This book was released on 2008 with total page 656 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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. -
Download or read book An Experimental Investigation Into the Effect of Vapor Bubbles on Boiling in Narrow Gaps written by Joseph F. Borowsky and published by . This book was released on 1993 with total page 124 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book An Experimental Investigation of the Condensation of Bubbles in an Immiscible Liquid in Downward Flow written by Nejib Ben Hedi Smaoui and published by . This book was released on 1990 with total page 188 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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.
Download or read book An Experimental Investigation of the Bubble Behaviour and Gas Flow Distribution in a Pressurized Fluidized Bed written by and published by . This book was released on 1989 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book An experimental investigation of pressure gradients in two phase flow with gas bubbles in the vicinity of the wall written by Robert Michael Roidt and published by . This book was released on 1967 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Thermal Design of Electronic Equipment written by Ralph Remsburg and published by CRC Press. This book was released on 2017-12-19 with total page 440 pages. Available in PDF, EPUB and Kindle. Book excerpt: In a field where change and growth is inevitable, new electronic packaging problems continually arise. Smaller, more powerful devices are prone to overheating, causing intermittent system failures, corrupted signals, lower MTBF, and outright system failure. Since convection cooling is the heat transfer path most engineers take to deal with thermal problems, it is appropriate to gain as much understanding about the underlying mechanisms of fluid motion as possible. Thermal Design of Electronic Equipment is the only book that specifically targets the formulas used by electronic packaging and thermal engineers. It presents heat transfer equations dealing with polyalphaolephin (PAO), silicone oils, perfluorocarbons, and silicate ester-based liquids. Instead of relying on theoretical expressions and text explanations, the author presents empirical formulas and practical techniques that allow you to quickly solve nearly any thermal engineering problem in electronic packaging.
Download or read book Experimental Investigation of the Bubble Column Hydrodynamics written by Booncheng Ong and published by . This book was released on 2003 with total page 590 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Bubble Generation in a Continuous Liquid Flow Under Reduced Gravity Conditions written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-06-13 with total page 158 pages. Available in PDF, EPUB and Kindle. Book excerpt: The present work reports a study of bubble generation under reduced gravity conditions for both co-flow and cross-flow configurations. Experiments were performed aboard the DC-9 Reduced Gravity Aircraft at NASA Glenn Research Center, using an air-water system. Three different flow tube diameters were used: 1.27, 1.9, and 2.54 cm. Two different ratios of air injection nozzle to tube diameters were considered: 0.1 and 0.2. Gas and liquid volumetric flow rates were varied from 10 to 200 ml/s. It was experimentally observed that with increasing superficial liquid velocity, the bubbles generated decreased in size. The bubble diameter was shown to increase with increasing air injection nozzle diameters. As the tube diameter was increased, the size of the detached bubbles increased. Likewise, as the superficial liquid velocity was increased, the frequency of bubble formation increased and thus the time to detach forming bubbles decreased. Independent of the flow configuration (for either single nozzle or multiple nozzle gas injection), void fraction and hence flow regime transition can be controlled in a somewhat precise manner by solely varying the gas and liquid volumetric flow rates. On the other hand, it is observed that uniformity of bubble size can be controlled more accurately by using single nozzle gas injection than by using multiple port injection, since this latter system gives rise to unpredictable coalescence of adjacent bubbles. A theoretical model, based on an overall force balance, is employed to study single bubble generation in the dynamic and bubbly flow regime. Under conditions of reduced gravity, the gas momentum flux enhances bubble detachment; however, the surface tension forces at the nozzle tip inhibits bubble detachment. Liquid drag and inertia can act either as attaching or detaching force, depending on the relative velocity of the bubble with respect to the surrounding liquid. Predictions of the theoretical model compare well with performed expe
Download or read book Flow Boiling in Multi Microchannels Using Refrigerant R134a and R1234yf written by Rand Mohamad Ali Al-Janabi and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
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.
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:
