Two-phase flow instabilities: A review
TL;DR: An updated review of two-phase flow instabilities including experimental and analytical results regarding density-wave and pressure-drop oscillations, as well as Ledinegg excursions, is presented in this article.
Abstract: An updated review of two-phase flow instabilities including experimental and analytical results regarding density-wave and pressure-drop oscillations, as well as Ledinegg excursions, is presented. The latest findings about the main mechanisms involved in the occurrence of these phenomena are introduced. This work complements previous reviews, putting all two-phase flow instabilities in the same context and updating the information including coherently the data accumulated in recent years. The review is concluded with a discussion of the current research state and recommendations for future works.
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TL;DR: In this article, a comprehensive review of the recent developments and applications of ultra-thin micro heat pipe (UTHP) for thermal management of electronics is presented, and the challenges affecting the development and application of UTHPs are outlined, and recommendations for future research are presented.
Abstract: The development of miniaturization and high-density packaging of electronic components demands heat dissipation components that are compact and exhibit high performance. An ultra-thin micro heat pipe (UTHP), as a novel heat pipe with a flat shape that is highly suitable for application with high power and limited heat dissipation space, has been extensively investigated and widely used in mobile electronics. Understanding the influence of the manufacturing processes, capillary wick structures and flattened thickness on the thermal performance of UTHPs has been the aim of numerous studies. This paper presents a comprehensive review of the recent developments and applications of UTHPs for thermal management of electronics. The different types and applications of UTHPs are introduced, and the packaging technologies of UTHPs are summarized and compared. Furthermore, the fabrication methodology and heat transfer characteristics of various wick structures used for UTHPs are reviewed and analysed in detail. Finally, the challenges affecting the development and application of UTHPs are outlined, and recommendations for future research are presented.
245 citations
TL;DR: In this paper, the authors reviewed the applications of ANN for thermal analysis of heat exchangers and highlighted the limitations of ANN in this field and its further research needs in the field.
Abstract: Artificial neural networks (ANN) have been widely used for thermal analysis of heat exchangers during the last two decades. In this paper, the applications of ANN for thermal analysis of heat exchangers are reviewed. The reported investigations on thermal analysis of heat exchangers are categorized into four major groups, namely (i) modeling of heat exchangers, (ii) estimation of heat exchanger parameters, (iii) estimation of phase change characteristics in heat exchangers and (iv) control of heat exchangers. Most of the papers related to the applications of ANN for thermal analysis of heat exchangers are discussed. The limitations of ANN for thermal analysis of heat exchangers and its further research needs in this field are highlighted. ANN is gaining popularity as a tool, which can be successfully used for the thermal analysis of heat exchangers with acceptable accuracy.
232 citations
Cites methods from "Two-phase flow instabilities: A rev..."
...(xvii) The identification of two phase flow instabilities in condensers and evaporators using ANN is a topic of major interest in many heat transfer applications [222]....
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TL;DR: In this paper, a comprehensive review of dynamic simulation, its development and application to various thermal power plants is presented, highlighting current research efforts and future development potential in the field of thermal power generation.
Abstract: While the conventional design of thermal power plants is mainly focused on high process efficiency, market requirements increasingly target operating flexibility due to the continuing shift towards renewables. Dynamic simulation is a cost-efficient tool for improving the flexibility of dispatchable power generation in transient operation such as load changes and start-up procedures. Specific applications include the optimisation of control structures, stress assessment for critical components and plant safety analysis in malfunction cases. This work is a comprehensive review of dynamic simulation, its development and application to various thermal power plants. The required mathematical models and various components for description the basic process, automation and electrical systems of thermal power plants are explained with the support of practical example models. The underlying flow models and their fundamental assumptions are discussed, complemented by an overview of commonly used simulation codes. Relevant studies are summarised and placed in context for different thermal power plant technologies: combined-cycle power, coal-fired power, nuclear power, concentrated solar power, geothermal power, municipal waste incineration and thermal desalination. Particular attention is given to those studies that include measurement validation in order to analyse the influence of model simplifications on simulation results. In conclusion, the study highlights current research efforts and future development potential of dynamic simulation in the field of thermal power generation.
215 citations
TL;DR: In this article, a hierarchical manifold micro-channel heat sink array is used to reduce the parasitic thermal resistances due to contact and conduction resistances, which can reduce the chip footprint area and shorten effective fluid flow lengths.
Abstract: High-heat-flux removal is necessary for next-generation microelectronic systems to operate more reliably and efficiently. Extremely high heat removal rates are achieved in this work using a hierarchical manifold microchannel heat sink array. The microchannels are imbedded directly into the heated substrate to reduce the parasitic thermal resistances due to contact and conduction resistances. Discretizing the chip footprint area into multiple smaller heat sink elements with high-aspect-ratio microchannels ensures shortened effective fluid flow lengths. Phase change of high fluid mass fluxes can thus be accommodated in micron-scale channels while keeping pressure drops low compared to traditional, microchannel heat sinks. A thermal test vehicle, with all flow distribution components heterogeneously integrated, is fabricated to demonstrate this enhanced thermal and hydraulic performance. The 5 mm × 5 mm silicon chip area, with resistive heaters and local temperature sensors fabricated directly on the opposite face, is cooled by a 3 × 3 array of microchannel heat sinks that are fed with coolant using a hierarchical manifold distributor. Using the engineered dielectric liquid HFE-7100 as the working fluid, experimental results are presented for channel mass fluxes of 1300, 2100, and 2900 kg/m2 s and channel cross sections with nominal widths of 15 μm and nominal depths of 35 μm, 150 μm, and 300 μm. Maximum heat flux dissipation is shown to increase with mass flux and channel depth and the heat sink with 15 μm × 300 μm channels is shown to dissipate base heat fluxes up to 910 W/cm2 at pressure drops of less than 162 kPa and chip temperature rise under 47 °C relative to the fluid inlet temperature.
205 citations
Cites background from "Two-phase flow instabilities: A rev..."
...This degradation of performance is triggered by vapor blanketing causing local and intermittent dryout at the wall, and has been previously observed in flow boiling experiments for microchannels [41,42]....
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TL;DR: In this paper, a hierarchical manifold microchannel heat sink array is fabricated and experimentally characterized for uniform heat flux dissipation over a footprint area of 5'mm'×'5'mm.
Abstract: A hierarchical manifold microchannel heat sink array is fabricated and experimentally characterized for uniform heat flux dissipation over a footprint area of 5 mm × 5 mm. A 3 × 3 array of heat sinks is fabricated into the silicon substrate containing the heaters for direct intrachip cooling, eliminating the thermal resistances typically associated with the attachment of a separate heat sink. The heat sinks are fed in parallel using a hierarchical manifold distributor that delivers flow to each of the heat sinks. Each heat sink contains a bank of high-aspect-ratio microchannels; five different channel geometries with nominal widths of 15 μm and 33 μm and nominal depths between 150 μm and 470 μm are tested. The thermal and hydraulic performance of each heat sink array geometry is evaluated using HFE-7100 as the working fluid, for mass fluxes ranging from 600 kg/m2 s to 2100 kg/m2 s at a constant inlet temperature of 59 °C. To simulate heat generation from electronics devices, a uniform background heat flux is generated with thin-film serpentine heaters fabricated on the silicon substrate opposite the channels; temperature sensors placed across the substrate provide spatially resolved surface temperature measurements. Experiments are also conducted with simultaneous background and hotspot heat generation; the hotspot heat flux is produced by a discrete 200 μm × 200 μm hotspot heater. Heat fluxes up to 1020 W/cm2 are dissipated under uniform heating conditions at chip temperatures less than 69 °C above the fluid inlet and at pressure drops less than 120 kPa. Heat sinks with wider channels yield higher wetted-area heat transfer coefficients, but not necessarily the lowest thermal resistance; for a fixed channel depth, samples with narrower channels have increased total wetted areas owing to the smaller fin pitches. During simultaneous background and hotspot heating conditions, background heat fluxes up to 900 W/cm2 and hotspot fluxes up to 2700 W/cm2 are dissipated. The hotspot temperature increases linearly with hotspot heat flux; at hotspot heat fluxes of 2700 W/cm2, the hotspot experiences a temperature rise of 16 °C above the average chip temperature.
79 citations
References
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Book•
01 Aug 1969
3,841 citations
"Two-phase flow instabilities: A rev..." refers background or methods in this paper
...One of the first works summarising different analytical andempiricalmodelswasperformedbyWallis [178]....
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...and Findlay [138] is a 1D approximation of the two-fluid model that introduces a time-independent correlation between the void fraction and the relative velocity between phases [178]....
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...A drift-flux model including the void distribution parameter C0, see Zuber and Findlay [138]; Wallis [178], is implemented....
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TL;DR: In this article, a generalized flow regime map based on this theory is presented, which is used for determining flow regime transitions in two-phase gas-liquid flow, and the mechanisms for transition are based on physical concepts and are fully predictive.
Abstract: Models are presented for determining flow regime transitions in two-phase gas-liquid flow. The mechanisms for transition are based on physical concepts and are fully predictive in that no flow regime transitions are used in their development. A generalized flow regime map based on this theory is presented.
2,420 citations
"Two-phase flow instabilities: A rev..." refers methods in this paper
...[26] analyse the internal characteristic curve of a natural circulation pipe, using different pressure drop models for the different flow patterns, based on the maps of Taitel and Dukler [27]....
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2,063 citations
"Two-phase flow instabilities: A rev..." refers background or methods in this paper
...Several forms of the conservation equations have been obtained [138,183,74]....
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...There are several versions of DFM, mainly depending on the assumption for the void distribution parameter [138,186]....
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...NSub stability maps Zuber and Findlay [138]....
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...and Findlay [138] is a 1D approximation of the two-fluid model that introduces a time-independent correlation between the void fraction and the relative velocity between phases [178]....
[...]
...A drift-flux model including the void distribution parameter C0, see Zuber and Findlay [138]; Wallis [178], is implemented....
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Book•
29 Nov 2005
TL;DR: In this article, two-phase field equations based on time average are proposed. But they do not consider the effect of structural materials in a control volume on the two-fluid model.
Abstract: Part I Fundamental of two-phase flow.- Introduction.- Local Instant Formulation.- Part II Two-phase field equations based on time average.- Basic Relations in Time Average.- Time Averaged Balance Equation.- Connection to Other Statistical Averages.- Part III. Three-dimensional model based on time average.- Kinematics of Averaged Fields.- Interfacial Transport.- Two-fluid Model.- Interfacial Area Transport.- Constitutive Modeling of Interfacial Area Transport.- Hydrodynamic Constitutive Relations for Interfacial Transfer.- Drift Flux Model.- Part IV: One-dimensional model based on time average.- One-dimensional Drift-flux Model.- One-dimensional Two-fluid Model.- Two-Fluid Model Considering Structural Materials in a Control Volume.
1,289 citations
"Two-phase flow instabilities: A rev..." refers background in this paper
...Several years later, Ishii and Hibiki [179] presented a rigorous mathematical formulation for the models describing multi-phase flow systems....
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