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Experimental Investigation Of Pool Boiling Heat Transfer Augmentation In R 123 Using The Electrohydrodynamic Technique And Its Long Term Effects
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Book Synopsis Experimental Investigation of Pool Boiling Heat Transfer Augmentation in R-123 Using the Electrohydrodynamic Technique and Its Long Term Effects by : Alok Kumar
Download or read book Experimental Investigation of Pool Boiling Heat Transfer Augmentation in R-123 Using the Electrohydrodynamic Technique and Its Long Term Effects written by Alok Kumar and published by . This book was released on 1994 with total page 216 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Electric Fields, Additives and Simultaneous Heat and Mass Transfer in Heat Transfer Enhancement by : Sujoy Kumar Saha
Download or read book Electric Fields, Additives and Simultaneous Heat and Mass Transfer in Heat Transfer Enhancement written by Sujoy Kumar Saha and published by Springer. This book was released on 2019-07-18 with total page 125 pages. Available in PDF, EPUB and Kindle. Book excerpt: This Brief deals with electrode design and placement, enhancement of both liquid and gas flow, vapor space condensation, in-tube condensation, falling film evaporation, correlations. It further provides a fundamental understanding of boiling and condensation, pool boiling, critical heat flux, convective vaporization, additives for single-phase liquids like solid particles, gas bubbles, suspensions in dilute polymer and surfactant solutions, solid additives and liquid additives for gases, additives for boiling, condensation and absorption, mass transfer resistance in gas phase (condensation with noncondensible gases, evaporation into air, dehumidifying finned tube heat exchangers, water film enhancement of finned tube exchanger), controlling resistance in liquid phase, and significant resistance in both phases. The volume is ideal for professionals and researchers dealing with thermal management in devices.
Book Synopsis Combined Effect of Electric Field and Surface Modification on Pool Boiling of R-123 by : Syed Waqas Ahmad
Download or read book Combined Effect of Electric Field and Surface Modification on Pool Boiling of R-123 written by Syed Waqas Ahmad and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The effect of surface modification and high intensity electric field (uniform and non - uniform) acting separately or in combination on pool boiling of R-123 is presented in this thesis. The effect of surface modification was investigated on saturated pool boiling of R-123 for five horizontal copper surfaces modified by different treatments, namely: an emery polished surface, a fine sandblasted surface, a rough sandblasted surface, an electron beam (EB) enhanced surface and a sintered surface. Each 40 mm diameter heating surface formed the upper face of an oxygen-free copper block, electrically heated by embedded cartridge heaters. The experiments were performed from the convective heat transfer regime to the critical heat flux, with both increasing and decreasing heat flux, at 1.01 bar, and additionally at 2 bar and 4 bar for the emery polished surface. Significant enhancement of heat transfer with increasing surface modification was demonstrated, particularly for the EB enhanced and sintered surfaces. The emery polished and sandblasted surface results are compared with nucleate boiling correlations and other published data. The effect of uniform and non-uniform electric fields on saturated pool boiling of R-123 at 1.01 bar pressure was also examined. This method of heat transfer enhancement is known as electrohydrodynamic abbreviated as EHD-enhancement. A high voltage potential was applied at the electrode located above the heating surface, which was earthed. The voltage was varied from 0 to 30 kV. The uniform electric field was provided through a 40 mm diameter circular electrode of stainless steel 304 wire mesh having an aperture of 5.1 mm, while the non-uniform electric field was obtained by using a 40 mm diameter circular rod electrode with rods 5 and 8 mm apart. The effect of uniform electric field was investigated using all five modified surfaces, i.e. emery polished, fine sandblasted, rough sandblasted, EB enhanced and sintered surfaces, while non - uniform electric field was tested using the emery polished, fine sandblasted, EB enhanced and sintered surfaces. The effect of pressure on EHD enhancement was also examined using emery polished surface at saturation pressure of 2 and 4 bars while the electric field was fix at 20 kV corresponding to 2 MV/m. Further, the bubble dynamics is presented for the emery polished surface obtained using a high-speed high - resolution camera.
Book Synopsis Advances in Enhanced Heat/mass Transfer and Energy Efficiency by : M. Mohamed Ohadi
Download or read book Advances in Enhanced Heat/mass Transfer and Energy Efficiency written by M. Mohamed Ohadi and published by . This book was released on 1995 with total page 140 pages. Available in PDF, EPUB and Kindle. Book excerpt: Comprises 15 contributions drawn from the November 1995 ASME International Mechanical Engineering Congress and Exposition. Topics include progress in enhanced heat and mass transfer; thermal characteristics of refrigerants/refrigerant mixtures; new methods to improve thermal performance of power and
Book Synopsis AN EXPERIMENTAL INVESTIGATION OF THE EFFECTS OF SURFACE CONDITIONS ON POOL-BOILING HEAT TRANSFER FOR VARIOUS MATERIALS. by : Shikha Ebrahim
Download or read book AN EXPERIMENTAL INVESTIGATION OF THE EFFECTS OF SURFACE CONDITIONS ON POOL-BOILING HEAT TRANSFER FOR VARIOUS MATERIALS. written by Shikha Ebrahim and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In this research, minimum film boiling temperature (Tmin) is quantitatively determined as a function of the initial substrate temperature, liquid subcooling, surface thermophysical properties and surface conditions. Since Tmin defines the boundary between the film and transition boiling regimes, its value is significant for the design of an emergency core cooling system following a hypothetical loss-of-coolant accident (LOCA) in a nuclear power plant. When a sufficiently heated surface is plunged in a water pool, a vapor blanket is generated around the test section acting as a heat transfer insulator due to the poor thermal conductivity of the vapor. At temperatures lower than Tmin, the heat transfer is dramatically enhanced owing the collapse of the vapor film allowing direct physical contact between the water and the heated surface. Therefore, it is very important to explore methods and techniques that increase this temperature in order to improve the safety of nuclear reactors. A test facility was designed and constructed to conduct quenching experiments using vertical rods. Seven cylindrical test samples were fabricated with embedded thermocouples inside the cladding material. The thermocouples were connected to a data acquisition system in order to measure the temperature history during the experiments. The temperature and heat flux at the surface were calculated using an inverse heat conduction code along with an advance image processing technique to quantitatively characterize the liquid-vapor interfacial waves, vapor layer thickness, Tmin, quenching temperature, quenching time, and quench front velocity in the film boiling heat transfer regime. Visualization of the boiling behavior was captured by a high-speed camera at a frame rate of 750 frames per second (fps). The thermocouple data and the captured videos were synchronized to couple the behavior of the vapor layer with the thermal behavior of the heated sample. Various characterization techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM) associated with Energy-dispersive X-ray spectroscopy (EDS), and field emission scanning electron were employed to identify the phases, chemical composition, and surface microstructure of the Inconel-600 before and after being used in a 7 x 7 rod bundle facility. Micro- and nanoparticles composed of nickel, chromium, and iron oxides were observed at the surface of the oxidized Inconel samples. It was found that the porous microstructure coupled with the increase in liquid spreading played a significant role in the enhancement of the film boiling heat transfer. Finally, the heat transfer behavior in the film boiling regime was investigated by calculating the heat transfer coefficient and Nusselt number for various cases. The novelty of this research is the coupling between the results of the quenching experiments and the surface characterization analyses that prompted the development of a new correlation for Tmin. This correlation adequately captures the effects of liquid subcooling, porosity of the oxide layer, and system pressure.
Book Synopsis An Experimental Study on Pool Boiling Performance Enhancement and Effect of Aging by : Aniket M. Rishi
Download or read book An Experimental Study on Pool Boiling Performance Enhancement and Effect of Aging written by Aniket M. Rishi and published by . This book was released on 2017 with total page 194 pages. Available in PDF, EPUB and Kindle. Book excerpt: "The miniaturization of electronic devices requires advanced thermal management techniques. The two-phase heat transfer process offers more effective and sustainable approach compared to the presently used single-phase cooling techniques. The boiling heat transfer is a two-phase cooling technique, that dissipates a high heat flux while maintaining the low surface temperature thereby, offering an efficient heat transfer mechanism compared to the single-phase process. Furthermore, the surface enhancement techniques such as micro/nano porous coatings help to maintain the low surface temperature thus improving the overall heat transfer performance. Electrodeposition is a simple technique that enhances this performance by creating the porous structure on the surface. This research focuses on developing an enhanced microscale structures on plain copper surfaces to improve the pool boiling performance. Additionally, the longevity (or the long-term stability) and aging of these enhanced structures, and their effects on the pool-boiling performance is also investigated. Initially the pool boiling performance of enhanced surfaces is studied. The enhanced surfaces were prepared using electrodeposition of copper and graphene oxide. Later, the effects of repetitive boiling on the morphology of the surfaces were examined using various characterization techniques such as Scanning Electron Microscope (SEM), X-Ray Diffraction (XRD), and Fourier Transform Infrared (FTIR). The chips coated with electrodeposition method rendered a high pool boiling performance for GS-4 (2.5% GO-Cu electrodeposited chip) with CHF of 220 W/cm2 at wall superheat of 14°C, giving ~76% improvement in CHF compared to plain copper chip. While, copper on copper electrodeposited chip, deposited with a different technique, performed better in both CHF and aging. CHF of 192 W/cm2 at wall superheat of 18.8°C was achieved for copper electrodeposited chip, giving ~30% enhancement compared to literature and ~54% enhancement when compared to plain copper chip. Moreover, surface characterization techniques including Scanning Electron Microscope (SEM) with Energy- Dispersive X-Ray Spectroscopy (EDS), Fourier Transform Infrared (FTIR), and X-Ray Diffraction (XRD) were employed to study the morphologies, elemental species, and to confirm the presence of graphene and graphene oxide on the test surfaces."--Abstract.
Book Synopsis An Experimental Investigation of Electrohydrodynamic (EHD) Enhancement of Boiling Heat Transfer by : Joerg H. Stromberger
Download or read book An Experimental Investigation of Electrohydrodynamic (EHD) Enhancement of Boiling Heat Transfer written by Joerg H. Stromberger and published by . This book was released on 1997 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Bubble Dynamics and Boiling Heat Transfer by : Samuel Siedel
Download or read book Bubble Dynamics and Boiling Heat Transfer written by Samuel Siedel and published by . This book was released on 2013 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since boiling heat transfer affords a very effective means to transfer heat, it is implemented in numerous technologies and industries ranging from large power generation plants to micro-electronic thermal management. Although having been a subject of research for several decades, an accurate prediction of boiling heat transfer is still challenging due to the complexity of the coupled mechanisms involved. It appears that the boiling heat transfer coefficient is intimately related to bubble dynamics (i.e. bubble nucleation, growth and detachment) as well as factors such as nucleation site density and interaction between neighbouring and successive bubbles. In order to contribute to the understanding of the boiling phenomenon, an experimental investigation of saturated pool boiling from a single or two neighbouring artificial nucleation sites on a polished copper surface has been performed. The bubble growth dynamics has been characterized for different wall superheats and a experimental growth law has been established. The interaction between successive bubbles from the same nucleation site has been studied, showing the bubble shape oscillations that can be caused by these interactions. The forces acting on a growing bubble has been reviewed, and a complete momentum balance has been made for all stages of bubble growth. The curvature along the interface has been measured, and indications concerning the mechanism of bubble detachment have been suggested. The rise of bubble after detachment has been investigated, and the maximum velocity reached before a change of direction has been estimated and compared to existing models from the literature. The interaction between bubbles growing side by side has been studied: the generation and propagation of a wave front during the coalescence of two bubbles has been highlighted. As boiling heat transfer enhancement techniques are being imagined and developed, this study also focuses on the electrohydrodynamic enhancement technique. Boiling experiments have been performed in the presence of electric fields, and their effects on heat transfer and bubble dynamics have been characterized. Although the volume of the bubbles at detachment and the relationship between the bubble frequency and the wall superheat were not affected, the bubble growth curve was modified. The bubbles were elongated in the direction of the electric field, and this elongation was estimated and compared to other studies from the literature. The rising velocity of the bubble was reduced in the presence of electric field, and the behaviour of bubbles growing side by side was modified, the electric field causing the bubbles to repeal each other. These results, obtained in a fully controlled environment, provide compelling evidence that electric fields can be implemented to alter the bubble dynamics and subsequently heat transfer rates during boiling of dielectric fluids.
Book Synopsis The Effect of Electrode Geometry on the Electrohydrodynamic Enhancement of Pool Boiling Heat Transfer of R123/oil Mixture by : Riyaz Amir Papar
Download or read book The Effect of Electrode Geometry on the Electrohydrodynamic Enhancement of Pool Boiling Heat Transfer of R123/oil Mixture written by Riyaz Amir Papar and published by . This book was released on 1993 with total page 194 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis An Experimental Study of Sodium Pool Boiling Heat Transfer by : R. C. Noyes
Download or read book An Experimental Study of Sodium Pool Boiling Heat Transfer written by R. C. Noyes and published by . This book was released on 1962 with total page 42 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Enhancement of Pool Boiling Heat Transfer with Electrohydrodynamics and Its Fundamental Study by : Sri Laxmi Priya Raghupathi
Download or read book Enhancement of Pool Boiling Heat Transfer with Electrohydrodynamics and Its Fundamental Study written by Sri Laxmi Priya Raghupathi and published by . This book was released on 1998 with total page 194 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis EHD-enhanced Pool Boiling Heat Transfer by : Majid Ali Faani Tabrizi Nezhaad
Download or read book EHD-enhanced Pool Boiling Heat Transfer written by Majid Ali Faani Tabrizi Nezhaad and published by . This book was released on 1997 with total page 492 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Electrohydrodynamic Pool Boiling Heat Transfer in Microgravity by : Charles Akira Murakami
Download or read book Electrohydrodynamic Pool Boiling Heat Transfer in Microgravity written by Charles Akira Murakami and published by . This book was released on 2004 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Enhancement of Pool Boiling Heat Transfer Using Thermally-conductive Microporous Coating Techniques by : Joo Han Kim
Download or read book Enhancement of Pool Boiling Heat Transfer Using Thermally-conductive Microporous Coating Techniques written by Joo Han Kim and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Book Synopsis Experimental Investigation on Effect of Heterogeneous Wettable Surfaces on Pool Boiling Heat Transfer Performance of Cylindrical Copper Surface by : 張耀文
Download or read book Experimental Investigation on Effect of Heterogeneous Wettable Surfaces on Pool Boiling Heat Transfer Performance of Cylindrical Copper Surface written by 張耀文 and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Proceedings of the ASME Heat Transfer Division by :
Download or read book Proceedings of the ASME Heat Transfer Division written by and published by . This book was released on 1997 with total page 380 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Enhancement of Pool Boiling Heat Transfer in Confined Space by : Chia-Hsiang Hsu
Download or read book Enhancement of Pool Boiling Heat Transfer in Confined Space written by Chia-Hsiang Hsu and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Pool boiling is an effective method used in many technical applications for a long time. Its highly efficient heat transfer performance results from not only the convection effect but also the phase change process in pool boiling. Pool boiling enhancement has been studied in the past decade. However, the mechanisms of pool boiling has not yet been fully understood because of the many parameters that affect its behavior including the latent heat of vaporization, nucleation density, bubble and fluid motion, interaction at the interface, and the physical properties of surface. Among the current studies, bubble departure rate is viewed as one of the dominant factors that affect heat transfer. This research considers the effect of bubble confinement on pool boiling. In the study, confinement was achieved by placing a flat plate over heated surface. The flat plate has a hole in the middle, and there is a gap between the flat plate and the heater. The diameters of hole are 2 mm, 3 mm, and 4 mm; the gap distances are 2.3 mm, 3.6 mm, and 5 mm. The heater consists of an indium-tin-oxide layer deposited on a silicon wafer. An IR camera and high speed cameras are used to acquire the surface temperature distribution and bubble image. By controlling the plate hole size and the gap distance, the effect of confinement on heat transfer performance can be evaluated. Moreover, heat transfer performance of pool boiling with three-2mm-holes plate was investigated and compared with that of single-2mm-hole plate with the smallest gap size. At the lower heat flux values, heat transfer enhancement in confined space was experimentally observed. Surface temperature can be reduced by 4 °C at most. Results indicate that higher bubble departure rate and coalescence effect might be the dominant factor for improving heat transfer performance in a confined space caused by induced shear flow. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/152843
