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

Download or read book Hydrodynamic Aspects of Boiling Heat Transfer written by N. Zuber and published by . This book was released on 1959 with total page 216 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Theoretical Study for Boiling Heat Transfer in a Confined Space written by Aboubakr A. Khalil and published by . This book was released on 1992 with total page 102 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Enhancement of Pool Boiling Heat Transfer Using a Combination of Open Microchannels and Microporous Surfaces written by Chinmay Patil and published by . This book was released on 2014 with total page 196 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Enhancement of Pool Boiling Critical Heat Flux in Dielectric Liquids written by Mehmet Arik and published by . This book was released on 2001 with total page 462 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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:

Download or read book Pool Boiling Heat Transfer written by Dong Soo Jung and published by . This book was released on 1984 with total page 246 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Advances in Heat Transfer written by and published by Elsevier. This book was released on 2023-09-13 with total page 598 pages. Available in PDF, EPUB and Kindle. Book excerpt: Advances in Heat Transfer, Volume 56, presents the latest in a serial that highlights new advances in the field, with this updated volume presenting interesting chapters written by an international board of authors. - Provides the authority and expertise of leading contributors from an international board of authors - Presents the latest release in Advances in Heat Transfer serials

Download or read book Heat Transfer Enhancement with Nanofluids written by Vincenzo Bianco and published by CRC Press. This book was released on 2015-04-01 with total page 473 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanofluids are gaining the attention of scientists and researchers around the world. This new category of heat transfer medium improves the thermal conductivity of fluid by suspending small solid particles within it and offers the possibility of increased heat transfer in a variety of applications. Bringing together expert contributions from

Download or read book Pool Boiling from Enhanced Structures Under Confinement written by Camil-Daniel Ghiu and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A study of pool boiling of a dielectric liquid (PF 5060) from single-layered enhanced structures was conducted. The parameters investigated were the heat flux, the width of the microchannels and the microchannel pitch. The boiling performance of the enhanced structures increases with increase in channel width and decrease in channel pitch. Simple single line curve fits are provided as a practical way of predicting the data over the entire nucleate boiling regime. The influence of confinement on the thermal performance of the enhanced structures was also assessed. The main parameter investigated was the top space (0 mm 3{13 mm). High-speed visualization was used as a tool . For the total confinement (= 0 mm), the heat transfer performance of the enhanced structures was found to depend weakly on the channel width. For>0 mm, the enhancement observed for plain surfaces in the low heat fluxes regime is not present for the present enhanced structure. The maximum heat flux for a prescribed 85 °C surface temperature limit increased with the increase of the top spacing, similar to the plain surfaces case. Two characteristic regimes of pool boiling have been identified and described: isolated flattened bubbles regime and coalesced bubbles regime. A semi-analytical predictive model applicable to pool boiling under confinement is developed. The model requires a limited number of empirical constants and is capable of predicting the experimental heat flux within 30%.

Download or read book Heat Transfer Enhancement of Heat Exchangers written by Sadik Kakaç and published by Springer Science & Business Media. This book was released on 2013-03-09 with total page 670 pages. Available in PDF, EPUB and Kindle. Book excerpt: Heat transfer enhancement in single-phase and two-phase flow heat exchangers in important in such industrial applications as power generating plant, process and chemical industry, heating, ventilation, air conditioning and refrigeration systems, and the cooling of electronic equipment. Energy savings are of primary importance in the design of such systems, leading to more efficient, environmentally friendly devices. This book provides invaluable information for such purposes.

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.

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 Boiling Heat Transfer in Confined Space written by Shi-Chune Yao and published by . This book was released on 1980 with total page 42 pages. Available in PDF, EPUB and Kindle. Book excerpt: In many equipments, boiling occurs in confined space such as the clearance between the tube and the support plate of steam generators. Corrosive concentration builds up at the boundary of dryout zone and induces severe damage. The knowledge on this kind of boiling phenomena is very limited. It is the objective of this research to understand this fundamental heat transfer of this problem through systematical analysis and experimental studies. This report covers the following aspects of the boiling in confined space: (1) Analysis of single phase forced convection in support plate crevices; (2) Analysis of convective boiling and dryout in support plate crevices; (3) Experiments of boiling and dryout in annular crevices with closed bottom; and (4) Experiments of convective boiling and dryout in annular crevices. (Author).

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:

Download or read book Enhanced Heat Transfer in Pool Boiling written by H. Yamaguchi and published by . This book was released on 1982 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Enhanced Pool Boiling of Water with Open Microchannels Over Cylindrical Tubes written by Jeet S. Mehta and published by . This book was released on 2013 with total page 222 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Pool boiling is a stable and efficient method for transferring large quantities of heat. It is employed in a wide range of applications, including steam generation in boilers, petrochemical, pharmaceutical, cryogenic and many other industrial processes. The objective of this work was to investigate the augmentation in the boiling heat transfer rates with an array of open microchannels over a cylindrical tube. In order to develop high performance surfaces, rectangular and V-groove cross-sectional geometry microchannels were fabricated and tested over tubular test sections. These microchannels were manufactured in two configurations: circumferentially around the test section and axially along the length. The effects of the microchannel geometric parameters on pool boiling performance were studied under horizontal and vertical orientations. Twenty uniquely modified microchannel surfaces were designed, fabricated and tested. The best performance was obtained with a circumferential rectangular microchannel test section in the horizontal orientation. A maximum heat transfer coefficient of 129 kW/m2*K was achieved at a heat flux of 1095 kW/m2, while maintaining a wall superheat of 8.5 K. The overall enhancement factors obtained at the maximum heat flux condition, ranged between 1.9 and 3.4 in the horizontal orientation, and 2.1 and 3.1 in the vertical orientation. The critical heat flux for almost all the designed test surfaces was increased by a factor of at least 1.6 over a plain tube. Area normalized results indicated that factors other than area enhancement are responsible for augmenting the heat transfer performance. High-speed videography of bubbles nucleating, growing and departing from the heated surface was performed. The bubble behavior over these open microchannels was analyzed to understand the fundamental mechanism during pool boiling. The bubble interactions in and over the open microchannels, and the liquid rewetting phenomenon greatly influence the heat transfer performance for these surface."--Abstract.