Download or read book Experimental Investigation of Single phase and Flow Boiling Submerged and Confined Microjet Array Heat Transfer written by Eric Browne and published by . This book was released on 2010 with total page 242 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book An Experimental Investigation of Pressure Drop and Heat Transfer for Water Boiling in a Vertical upflow Single tube Heat Exchanger written by James R. Stone and published by . This book was released on 1967 with total page 42 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Experimental Investigation of Friction Factor and Heat Transfer for Single Phase Water Flow in Stainless Steel and Nickel Micro tubes written by Qian Li and published by . This book was released on 2012 with total page 76 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Flow Boiling in Microgap Channels written by Tamanna Alam and published by Springer Science & Business Media. This book was released on 2013-08-26 with total page 88 pages. Available in PDF, EPUB and Kindle. Book excerpt: Flow Boiling in Microgap Channels: Experiment, Visualization and Analysis presents an up-to-date summary of the details of the confined to unconfined flow boiling transition criteria, flow boiling heat transfer and pressure drop characteristics, instability characteristics, two phase flow pattern and flow regime map and the parametric study of microgap dimension. Advantages of flow boiling in microgaps over microchannels are also highlighted. The objective of this Brief is to obtain a better fundamental understanding of the flow boiling processes, compare the performance between microgap and conventional microchannel heat sinks, and evaluate the microgap heat sink for instabilities and hotspot mitigation.
Download or read book Investigation of Single Phase and Boiling Jet Impingement Heat Transfer written by Sanjeev K. Hingorani and published by . This book was released on 1996 with total page 368 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Thermal Management for Opto electronics Packaging and Applications written by Xiaobing Luo and published by John Wiley & Sons. This book was released on 2024-08-12 with total page 373 pages. Available in PDF, EPUB and Kindle. Book excerpt: Thermal Management for Opto-electronics Packaging and Applications A systematic guide to the theory, applications, and design of thermal management for LED packaging In Thermal Management for Opto-electronics Packaging and Applications, a team of distinguished engineers and researchers deliver an authoritative discussion of the fundamental theory and practical design required for LED product development. Readers will get a solid grounding in thermal management strategies and find up-to-date coverage of heat transfer fundamentals, thermal modeling, and thermal simulation and design. The authors explain cooling technologies and testing techniques that will help the reader evaluate device performance and accelerate the design and manufacturing cycle. In this all-inclusive guide to LED package thermal management, the book provides the latest advances in thermal engineering design and opto-electronic devices and systems. The book also includes: A thorough introduction to thermal conduction and solutions, including discussions of thermal resistance and high thermal conductivity materials Comprehensive explorations of thermal radiation and solutions, including angular- and spectra-regulation radiative cooling Practical discussions of thermally enhanced thermal interfacial materials (TIMs) Complete treatments of hybrid thermal management in downhole devices Perfect for engineers, researchers, and industry professionals in the fields of LED packaging and heat transfer, Thermal Management for Opto-electronics Packaging and Applications will also benefit advanced students focusing on the design of LED product design.
Download or read book Experimental Investigation of Gravity independent Flow Boiling Regimes written by Jason Scott Bower and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: ABSTRACT: Heat transfer coefficients have been investigated and it appears that a consequence of gravity independence of ebullition phenomena is a corresponding gravity independent thermal transport two-phase flow-boiling regime. The dependent/independent regime map constructed from experimental data suggests that the analytical bubble dynamics model prescribes a conservative design criterion for the gravity-independent regime. The problem of heat exchanger component burnout has been addressed in the study by measuring the critical heat flux at differing orientations relative to gravity. The data exhibit a strong influence of orientation and suggest that flow orientations without sufficient means to sweep and lift vapor away from the heat transfer surface are subject to considerably lower critical heat fluxes. However, at high velocities, the differences among flow orientations are sharply reduced, suggesting there exists a high velocity region where the critical heat flux is gravity-independent.
Download or read book The proceedings of the 16th Annual Conference of China Electrotechnical Society written by Qingxin Yang and published by Springer Nature. This book was released on 2022-04-17 with total page 1465 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book gathers outstanding papers presented at the 16th Annual Conference of China Electrotechnical Society, organized by China Electrotechnical Society (CES), held in Beijing, China, from September 24 to 26, 2021. It covers topics such as electrical technology, power systems, electromagnetic emission technology, and electrical equipment. It introduces the innovative solutions that combine ideas from multiple disciplines. The book is very much helpful and useful for the researchers, engineers, practitioners, research students, and interested readers.
Download or read book Submerged Jet Impingement Boiling Thermal Management written by Ruander Cardenas and published by . This book was released on 2011 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt: Technologies such as avionics and power electronics are driving the demand for thermal management schemes towards high heat fluxes and low surface temperatures. Typically, these applications require the dissipation of heat fluxes in the rage of 100-1000 W/cm2 while maintaining surface temperatures lower than about 85 °C. Phase-change heat transfer schemes such as pool boiling, flow boiling in mini/micro-channel heat sinks, and sprays and jet impingement boiling are frequently used to meet this demand. This dissertation documents global heat transfer characteristics of submerged jet impingement boiling for high heat flux, low surface temperature applications. The effect of geometrical and flow parameters on heat transfer performance are examined for a single circular jet using water and FC-72 as working fluids. Exclusive to this study is the comparison of distinct jet fluids at a fixed saturation temperature, which is achieved by comparing sub-atmospheric jet impingement boiling data of water with atmospheric FC-72 experiments. Under sub-atmospheric conditions, the liquid-to-vapor density ratio of water is within a range that has not been studied in previous jet impingement boiling experiments. Varied geometrical parameters include the surface-to-nozzle diameter ratio, surface roughness, and jet configuration. Varied fluidic parameters include pressure, jet exit Reynolds number, fluid subcooling, and fluid properties. Global experimental data collected during this study are used to document the relationship between surface temperature and surface heat flux through boiling curves. The global data are augmented by qualitative high-speed visualization. Experimental data demonstrate enhanced heat transfer capabilities beyond those of pool boiling by using a submerged impinging jet. For a fixed saturation temperature, significantly higher heat transfer rates are attainable using water in comparison to FC-72. A CHF map for submerged jet impingement boiling is developed based on experimental evidence. A general submerged jet impingement CHF correlation is developed based on a well known CHF model in literature. A novel, passive means of preventing temperature overshoot of highly-wetting fluids during submerged jet impingement boiling is introduced.
Download or read book Experimental Investigation of Subcooled Flow Boiling Using Synchronized High Speed Video Infrared Thermography and Particle Image Velocimetry written by Bren Andrew Phillips and published by . This book was released on 2014 with total page 206 pages. Available in PDF, EPUB and Kindle. Book excerpt: Subcooled flow boiling of water was experimentally investigated using high-speed video (HSV), infrared (IR) thermography, and particle image velocimetry (PIV) to generate a unique database of synchronized data. HSV allowed measurement of the bubble departure diameter. IR thermography allowed measurement of wall superheat (local distribution and surface-averaged values), heat transfer coefficient, nucleation site density, and bubble frequency. Particle image velocimetry allowed for the measurement of velocity profiles in the liquid phase for single bubble nucleation events. The tests were performed at pressures of 1.05, 1.5, and 2.0 bar and at subcoolings of 5, 10, and 15 °C. The mass flux values explored were 150-1250 kg/m2/s. The heat flux values explored were 100-1600 kW/m2. As expected, the heat transfer coefficients increased with increasing mass flux in the single-phase convection and partial boiling regions, and converged to a fully-developed boiling curve for high heat fluxes. The bubble departure diameter decreased with increasing mass flux and decreasing heat flux; in accordance with Sugrue's model. The nucleation site density increased with increasing superheat and decreasing mass flux, as predicted by Kocamustafaogullari and Ishii's model. The nucleation site density models under-predicted the nucleation site density for a given wall superheat. Wait time and frequency models did not reproduce the data accurately, and underestimated wait time by an order of magnitude. A new mechanistic model for calculating the wait time was developed that split the wall heat flux into the component that is transferred to the fluid, and the component that is transferred as sensible heat into the heater wall. Significant localized cooling was observed underneath bubbles sliding along the wall after departure from a nucleation site, an effect which should be considered in advanced models of subcooled flow boiling. The sliding bubble thermal effects were found to be insensitive to system conditions and were limited by the thermal conduction within the substrate. Bubble growth front velocities, and regions of flow influence of departing bubbles were measured with PIV. The database generated in this project can be used to inspire or validate mechanistic models and/or CFD simulations of subcooled flow boiling heat transfer.
Download or read book Experimental Investigation and Analytical Modeling of Flow Boiling Characteristics in Silicon Microchannel Arrays written by Ayman Megahed and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Experimental Investigation of Flow Boiling Heat Transfer in a Microchannel by Using Infrared Thermography written by M. Cortina Diaz and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Heat Transfer Enhancement of Single phase Flow and Flow Boiling in Microchannels an Experimental Study written by Yingying Wang and published by . This book was released on 2014 with total page 264 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Single phase and Boiling Flow in Microchannels with High Heat Flux written by Elmer Galvis and published by . This book was released on 2012 with total page 226 pages. Available in PDF, EPUB and Kindle. Book excerpt: A cooling system for high heat flux applications is examined using microchannel evaporators with water as the working fluid and boiling as the heat transfer mechanism. Experimental studies are performed using single channel microevaporators allowing for better control of the flow mechanics unlike other investigations where multiple, parallel, flow channels can result in a non-uniform distribution of the working fluid. High-speed flow visualizations are performed in conjunction with heat transfer and pressure drop measurements to support the quantitative experimental data. Flow patterns associated with a range of boundary conditions are characterized and then presented in the form of novel flow regime maps that intrinsically reflect the physical mechanisms controlling two-phase pressure distributions and heat transfer behavior. Given the complexity associated with modeling of boiling heat transfer and the lack of a universal model that provides accurate predictions across a broad spectrum of flow conditions, flow regime maps serve as a valuable modeling aid to assist in targeted modeling over specific flow regimes. This work represents a novel and original contribution to the understanding of boiling mechanisms for water in microchannels. The flow patterns in this work are found to be closely coupled with mass flux, heat flux, and channel size; where re-wetting and pressure oscillations play a crucial role, and are likely responsible for its development and evolution. Reversed flow, typically attributed to a non-uniform fluid distribution in multiple channel microevaporators by other researchers, is shown to be a result of the upstream expansion of confined bubbles. During flow boiling, the pressure drop in the microchannel increases with the heat flux for a constant flow rate due to the significant acceleration effects associated with smaller channels, unlike in single-phase flow where the pressure drop is constant. Water flow boiling in rectangular microchannels, although not extensively explored in the published literature, provides an extremely high cooling capacity, with dissipation rates approaching 440 W/cm2, making this an ideal candidate for cooling of next generation electronic systems. Single-phase flow studies revealed that pressure and heat transfer coefficient macroscale models are transferable to microchannels with hydraulic diameters down to 200 [mu]m, when the entrance effects and minor losses are properly considered. These studies include laminar developing flow conditions not commonly considered in the literature and fully developed flow. Since the applicability of macroscale theories to microchannels is often questioned, this investigation helps clarify this issue for microchannels within the range of experimental conditions explored in this work. Finally, new correlations for the hydrodynamic entrance length are proposed for rectangular microchannels and good agreement is found when compared with published experimental data over a wide range of Reynolds number. These correlations are more accurate, and original in the sense that they incorporate the effects of channel aspect ratio, and include creeping flow conditions which are currently unavailable for rectangular microchannels. This work represents a major advance in the development of new cooling systems for high heat flux applications requiring dissipation rates in excess of 100 W/cm2.
Download or read book Experimental Investigations of Flow Boiling Heat Transfer and Flow Instability in a Horizontal Microtube with an Inlet Orifice written by Yan Feng Fan and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book An Experimental Investigation of Pressure Drop and Heat Transfer for Water Boiling in a Vertical upflow Single tube Heat Exchanger written by James R. Stone 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 Experimental Investigation on Multiscale Interactions in Intermittent Flow Boiling and a New Hybrid VOF Lagrangian Modeling Approach written by Xiang Zhang and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: In flow boiling, most phase change heat transfer occurs at the smallest scales: in 1 nm -- 10 [mu]m thick liquid microlayers under nucleating bubbles and in thin thermal boundary layers around such bubbles. Nucleating bubbles evolve from microscopic cavities on heated surfaces (reaching 104 - 106 sites per cm2). Theoretical closure models have been proposed for individual bubble nucleation, growth, and departure due to hydrodynamics. However, high-fidelity integration of such microscale models and theory with full channel flow processes has proven challenging due to the large range of length and time scales. Thus, contemporary boiling engineering still relies on empirical correlations. While such models are validated by large experimental databases, they are limited to specific fluids and geometries. More rigorous descriptions are needed to predict transport with emerging configurations and fluids. The first objective of this study is to experimentally characterize the coupling between micro-scale transport and large-scale hydrodynamics in flow boiling heat transfer through high-speed photography and thermal imaging. A new hybrid volume-of-fluid (VOF)-Lagrangian multi-scale simulation approach is then proposed to directly resolve and couple these processes. Experimental data from this investigation and other publications are employed to assess this modeling approach. First, a square air-oil bubble column facility is built to track the bubble trajectories at free surface and assess the hybrid VOF-Lagrangian simulation approach. High speed videos are captured from both the front and top view to measure flow parameters including: bubble size distribution (BSD), bubble rise velocity in vertical direction, as well as bubble lifetime and propagation velocity at the free surface. A hybrid VOF-Lagrangian solver is developed to characterize the coupling between micro-scale bubble transport and macro-scale hydrodynamics in such multi-scale two-phase flows. The Lagrangian model tracks the trajectory of individual injected discrete small bubbles, accounting for effects such as buoyancy, pressure, virtual mass, drag, and turbulent dispersion. Once bubbles exceed a threshold packing density or overlap with VOF structures, they are converted to the grid-scale vapor phase. An empirical bubble-lifetime model is implemented to account for the finite coalescence times of bubbles at free surfaces. Contributions of this effort include programmable closure for bubble lifetime at the free surface (before popping/coalescence), a pinning force method for bubbles at the free surface, and Lagrangian-to-VOF transition of bubbles based on packing density. Next, a two-phase flow boiling experimental facility is developed to collect simultaneous high-speed visualization and IR temperature distribution data. The test cell channel is 420 mm long with a 10 mm square-cross section. A transparent ITO coated sapphire window serves as a heater and IR interface for measuring the internal wall temperature. The facility is charged with a low boiling point fluid (HFE7000) to reduce uncertainties from heat loss. Vertical saturated flow boiling wake-nucleation interaction experiments are performed for varying volume flow rates (0.5 -- 1.5 L min-1, laminar-to-turbulent Re) and heat fluxes (0 -- 100 kW m-2). Discrete vapor slugs are injected to explore interactions with nucleate boiling processes. By measuring film-heater power, surface temperature distributions, and pressures, local instantaneous heat transfer coefficients (HTC) are obtained. A conjugate gradient method is implemented to solve the 2-D transient inverse heat conduction problem and estimate the non-uniform heat flux distribution. For nucleate flow boiling without slug injection, visualizations show that both bubble cycle and wait time are inversely proportional to the applied heat flux. The average wall temperature displays a linear relationship with heat flux. Moreover, bubble departure diameter tends to increase with increasing the bubble nucleation temperature, and stabilizes at higher temperature. With respect to the wake-nucleation interaction experiments, it is found that small nucleate bubbles only in the core region of Taylor bubble body with a certain bubble size (1.4 to 1.6 mm) would merge into the vapor slug. IR data indicate that the wake shear effect is divided into 5 stages during the whole process. Wake heat transfer enhancement is observed due to the vortex shedding and intense mixing between in the Taylor bubble wake. In addition, the nucleate boiling is firstly suppressed in the Taylor bubble body due to the falling liquid film, then recovered after the wake region. To efficiently simulate such processes, the hybrid VOF-Lagrangian model is extended to account for heat transfer, bulk- and Lagrangian-bubble-scale phase change, and nucleation site processes. The approach tracks discrete nucleation sites on walls and simulates a contact line pinning force. Bubble growth and departure is directly predicted using grid-scale VOF velocity and temperature data rather than idealized conditions. This method is first verified with literature data for pool boiling. It is then qualitatively assessed for the Taylor flow boiling processes studied experimentally.
