Author: Camil-Daniel Ghiu
Publisher:
ISBN:
Category : Ebullition
Languages : en
Pages :
Book Description
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%.
Pool Boiling from Enhanced Structures Under Confinement
Author: Camil-Daniel Ghiu
Publisher:
ISBN:
Category : Ebullition
Languages : en
Pages :
Book Description
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%.
Publisher:
ISBN:
Category : Ebullition
Languages : en
Pages :
Book Description
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%.
Enhancement of Pool Boiling Heat Transfer in Confined Space
Author: Chia-Hsiang Hsu
Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
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
Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
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
Hydrodynamic Aspects of Boiling Heat Transfer
Author: N. Zuber
Publisher:
ISBN:
Category : Heat
Languages : en
Pages : 216
Book Description
Publisher:
ISBN:
Category : Heat
Languages : en
Pages : 216
Book Description
Handbook of Thermal Science and Engineering
Author:
Publisher: Springer
ISBN: 9783319266947
Category : Science
Languages : en
Pages : 0
Book Description
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.
Publisher: Springer
ISBN: 9783319266947
Category : Science
Languages : en
Pages : 0
Book Description
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.
Mechanistic Understanding and Enhancing Pool Boiling Heat Transfer Via Surface Property and Structure Design
Author: Youngsup Song
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
Book Description
This thesis provides important insights to understand the role of surface properties and structures on pool boiling heat transfer, thereby providing guidelines for the systematic design of surface structures for enhanced pool boiling heat transfer.
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
Book Description
This thesis provides important insights to understand the role of surface properties and structures on pool boiling heat transfer, thereby providing guidelines for the systematic design of surface structures for enhanced pool boiling heat transfer.
The effects of confinement and transient to pool boiling on vertical tubes
Author: Yung Chang
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
Book Description
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
Book Description
Enhanced Heat Transfer in Pool Boiling
Author: H. Yamaguchi
Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
Encyclopedia Of Two-phase Heat Transfer And Flow Iii: Macro And Micro Flow Boiling And Numerical Modeling Fundamentals (A 4-volume Set)
Author: John R Thome
Publisher: World Scientific
ISBN: 9813227427
Category : Technology & Engineering
Languages : en
Pages : 1460
Book Description
Set III of this encyclopedia is a new addition to the previous Sets I and II. It contains 26 invited chapters from international specialists on the topics of numerical modeling of two-phase flows and evaporation, fundamentals of evaporation and condensation in microchannels and macrochannels, development and testing of micro two-phase cooling systems for electronics, and various special topics (surface wetting effects, microfin tubes, two-phase flow vibration across tube bundles). The chapters are written both by renowned university researchers and by well-known engineers from leading corporate research laboratories. Numerous 'must read' chapters cover the fundamentals of research and engineering practice on boiling, condensation and two-phase flows, two-phase heat transfer equipment, electronics cooling systems, case studies and so forth. Set III constitutes a 'must have' reference together with Sets I and II for thermal engineering researchers and practitioners.
Publisher: World Scientific
ISBN: 9813227427
Category : Technology & Engineering
Languages : en
Pages : 1460
Book Description
Set III of this encyclopedia is a new addition to the previous Sets I and II. It contains 26 invited chapters from international specialists on the topics of numerical modeling of two-phase flows and evaporation, fundamentals of evaporation and condensation in microchannels and macrochannels, development and testing of micro two-phase cooling systems for electronics, and various special topics (surface wetting effects, microfin tubes, two-phase flow vibration across tube bundles). The chapters are written both by renowned university researchers and by well-known engineers from leading corporate research laboratories. Numerous 'must read' chapters cover the fundamentals of research and engineering practice on boiling, condensation and two-phase flows, two-phase heat transfer equipment, electronics cooling systems, case studies and so forth. Set III constitutes a 'must have' reference together with Sets I and II for thermal engineering researchers and practitioners.
An Experimental Study on Pool Boiling Performance Enhancement and Effect of Aging
Author: Aniket M. Rishi
Publisher:
ISBN:
Category : Ebullition
Languages : en
Pages : 194
Book Description
"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.
Publisher:
ISBN:
Category : Ebullition
Languages : en
Pages : 194
Book Description
"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.
The Critical Heat Flux Under Pool Boiling and Confined Boiling Conditions
Author: James A. Riley
Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description