Download or read book Experimental Studies of Nucleation Phenomena and Heat Transfer During Fast Transient Pool Boiling in Water and Organic Fluids written by Waljahat Hussain Salman and published by . This book was released on 1994 with total page 405 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Experimental Studies of Nucleation and Heat Transfer in Fast Transient Boiling Tests with Water written by Lang Hong Zhu and published by . This book was released on 1985 with total page 77 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Experimental Study of Nucleate Boiling Bubble Dynamics and Heat Transfer Enhancement on Printed Bi functional Surfaces written by Michele David and published by . This book was released on 2016 with total page 76 pages. Available in PDF, EPUB and Kindle. Book excerpt: Boiling heat transfer is studied for its ability to dissipate high fluxes and achieve heat transfer coefficients two orders of magnitude greater than single-phase heat transfer systems. Heater surface enhancement with increased surface area, varied geometry, wettability contrast and micro/nano-structures can further enhance boiling heat transfer performance through bubble nucleation augmentation. Bubble nucleation control, growth and departure dynamics is important in understanding boiling phenomena and enhancing nucleate boiling heat transfer performance. Bi-functional surfaces for enhanced boiling heat transfer were fabricated and studied through investigation of bubble dynamics and pool boiling experiments. For the fabrication of the surface, hydrophobic polymer dot arrays are first printed on a substrate, followed by hydrophilic ZnO nanostructure deposition via microreactor-assisted nanomaterial deposition (MAND) processing. Wettability contrast between the hydrophobic polymer dot arrays and aqueous ZnO solution allows for the fabrication of surfaces with distinct wettability regions. Bi-functional surfaces with various configurations were fabricated and their bubble dynamics were examined at elevated heat flux, revealing various nucleate boiling phenomena. In particular, aligned and patterned bubbles with a tunable departure frequency and diameter were demonstrated in a boiling experiment for the first time. A pool boiling experimental facility has been designed and built to investigate nucleate pool boiling in water at atmospheric pressure. Resulting boiling curves of enhanced surfaces showed up to 3X enhancement in heat transfer coefficients at the same surface superheat using bi-functional surfaces, compared to a bare stainless steel surface. The surfaces show promising results for energy savings in two-phase change applications.
Download or read book Experimental and Analytical Study of the Effects of Wettability on Nucleation Site Density During Pool Boiling written by Chunghsiung Wang and published by . This book was released on 1992 with total page 256 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Survey of the Literature Pertaining to the Phenomena of Nucleate Boiling written by R. A. Rockow and published by . This book was released on 1959 with total page 58 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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.
Download or read book Experimental Studies of Fast Transient Boiling in Water and Organic Fluids written by Lang Hong Zhu and published by . This book was released on 1993 with total page 299 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book An Analytical and Experimental Study of the Thermal Boundary Layer and Ebullition Cycle in Nucleate Boiling written by Yih-Yun Hsu and published by . This book was released on 1961 with total page 54 pages. Available in PDF, EPUB and Kindle. Book excerpt: The ebullition cycle of nucleate pool boiling from a heating strip was studied through the use of high-speed motion pictures of schlieren and shadowgraph images. The effects of bubble agitation on thermal layer and neighboring bubbles were observed. An over-all model of ebullition based upon experimental observation was proposed that included an analytical method for predicting bubble growth rate and an analysis of the factors that influence the magnitude of the waiting period (time interval between bubbles at a particular site). Thermal-layer thickness, cavity size, and area of influence of a growing bubble are considered. A film supplement is made available. (Author).
Download or read book Micro and Macro phenomena in Nucleate Pool Boiling on Graphite copper Composite Materials written by Gai-Wai Yang and published by . This book was released on 1995 with total page 350 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Experiments on the Mechanism of Saturated Nucleate Pool Boiling Heat Transfer written by Bruce David Marcus and published by . This book was released on 1963 with total page 444 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book An Empirical Modification of Nucleation Theory and Its Application to Boiling Heat Transfer written by Yan Po Chang and published by . This book was released on 1961 with total page 40 pages. Available in PDF, EPUB and Kindle. Book excerpt: From the equations of momentum and of energy and by the aid of established experimental phenomena, the problem of heat transfer in nucleate boiling is reduced to one of three parameters: the first represents the Stanton number, the second bubble growth, and the third nucleation.
Download or read book An Experimental Investigation of Transition Pool Boiling written by Tadao Aoki and published by . This book was released on 1970 with total page 214 pages. Available in PDF, EPUB and Kindle. Book excerpt: The heat-transfer phenomena studied in this work were associated with pool boiling from a flat horizontal surface facing upward with the bulk liquid at its saturation temperature. The analysis of boiling sound and the investigation of the transition boiling mechanism constituted the essence of the present study. The distinctively large sound intensity with predominant frequency components of 250 Hz and 500 Hz was observed during transition boiling. From the photographic studies of surface temperature variation, it was concluded that the heat transfer mechanism at relatively low heat flux levels of transition boiling involves the direct contact between liquid and the hot surface followed by a spheroidal state of the liquid. At higher heat flux levels while the liquid was in the spheroidal state, its contribution to total heat transfer increased with a decrease in surface temperature.
Download or read book Handbook of Thermal Science and Engineering written by and published by Springer. This book was released on 2018-07-31 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Nuclear Science Abstracts written by and published by . This book was released on 1967 with total page 1220 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Investigation of Nucleation and Heat Transfer During Subcooled Flow Boiling on Augmented Surfaces written by Matthew J. Howell and published by . This book was released on 1996 with total page 338 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Heat transfer characteristics of flat augmented surfaces in subcooled flow boiling with water at atmospheric pressure were obtained as functions of the surface orientation and Reynolds number. Data was collected with the heater surface temperature between 90C and 1 15C. The maximum temperature recorded by the thermocouple closest to the heater was between 200C and 220C. Five augmented surfaces and a base line plain polished aluminum surface were prepared and their performance was experimentally obtained in a 3 mm x 40 mm rectangular channel. The five augmented surfaces consisted of a sintered plain surface, microfin #1 (fin height- 132 mm, pitch - 635 mm, fin shape - round), sintered microfin #1, microfin #2 (fin height - 197 mm, pitch - 726 mm, fin shape - trapezoidal), and microfin #3 (fin height - 240 mm, pitch - 870 mm, fin shape - trapezoidal). Two microfin orientations of 0 and 20 were tested by rotating the heater surface. The heat transfer performance of the heater surface in the non-boiling (single-phase) and boiling regions were obtained over a Reynolds number range of 1565 to 7254 and compared with the plain surface performance. Microfin #3 and microfin #1 exhibited better heat transfer performance compared to the polished aluminum surface while microfin #2 transferred less heat compared to the polished aluminum surface. For microfin #1 nucleation started as soon as positive wall superheat was attained, while for microfin #2, microfin #3, and a polished aluminum surface a wall superheat of 6 to 10 C was required for inception of nucleation. A number of parameters affect the heat transfer from the augmented surfaces - subcooling, flow rate, swirl angle, surface finish, and surface geometry. The effect of these parameters was investigated for the six surfaces studied. Bubble activity was studied with the aid of video images obtained using a regular 30 frames per second video camera and a high speed video camera up to 1 000 frames per second under a magnification of up to 43 OX. As the degree of superheat increased beyond 10C, bubble activity became faster and could not be tracked by the high speed camera which only showed streaks of bubbles. It is thought that this increased bubble behavior continues with faster and smaller bubbles as the surface temperature continues to increase. Using experimental data taken by Mizo (1995), for flow boiling of water on a flat polished aluminum surface, existing pool boiling bubble growth models were investigate for possible extension into flow boiling. Extending existing pool boiling models to flow boiling proved very complex. Mikic and Rohsenow's [17] pool boiling bubble growth rate model is well accepted in literature. Limitations in applying this work to flow boiling were identified."--Abstract.
Download or read book Pool Boiling Studies on Nanotextured Surfaces Under Highly Subcooled Conditions written by Vijaykumar Sathyamurthi and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Subcooled pool boiling on nanotextured surfaces is explored in this study. The experiments are performed in an enclosed viewing chamber. Two silicon wafers are coated with Multiwalled Carbon Nanotubes (MWCNT), 9 microns (Type-A) and 25 microns (Type-B) in height. A third bare silicon wafer is used for control experiments. The test fluid is PF-5060, a fluoroinert with a boiling point of 56°C (Manufacturer: 3M Co.). The apparatus is of the constant heat flux type. Pool boiling experiments in nucleate and film boiling regimes are reported in this study. Experiments are carried out under low subcooling (5 °C and 10 °C) and high subcooling conditions (20°C to ~ 38°C). At approximately 38°C, a non-departing bubble configuration is obtained on a bare silicon wafer. Increase in subcooling is found to enhance the critical heat flux (CHF) and the CHF is found to shift towards higher wall superheats. Presence of MWCNT on the test surface led to an enhancement in heat flux. Potential factors responsible for boiling heat transfer enhancement on heater surfaces coated with MWCNT are identified as follows: a. Enhanced surface area or nano - fin effect b. Higher thermal conductivity of MWCNT than the substrate c. Disruption of vapor-liquid vapor interface in film boiling, and of the "microlayer" region in nucleate boiling d. Enhanced transient heat transfer caused by local quasi-periodic transient liquid-solid contacts due to presence of the "hair like" protrusion of the MWCNT e. Enhancement in the size of cold spots f. Pinning of contact line, leading to enhanced surface area underneath the bubble leading to enhanced heat transfer Presence of MWCNT is found to enhance the phase change heat transfer by approximately 400% in nucleate boiling for conditions of low subcooling. The heat transfer enhancement is found to be independent of the height of MWCNT in nucleate boiling regime in the low subcooling cases. About 75%-120% enhancement in heat transfer is observed for surfaces coated with MWCNT under conditions of high subcooling in the nucleate boiling regime. Surfaces coated with Type-B MWCNT show a 75% enhancement in heat transfer in the film boiling regime under conditions of low subcooling.
Download or read book Activation Growth and Detachment of Boiling Bubbles in Water from Artificial Nucleation Sites of Known Geometry and Size written by John R. Howell and published by . This book was released on 1967 with total page 50 pages. Available in PDF, EPUB and Kindle. Book excerpt:
