Next Generation Microchannel Heat Exchangers
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Next Generation Microchannel Heat Exchangers
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Author : Michael Ohadi
language : en
Publisher: Springer Science & Business Media
Release Date : 2012-10-16
Next Generation Microchannel Heat Exchangers written by Michael Ohadi and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012-10-16 with Technology & Engineering categories.
In Next Generation Microchannel Heat Exchangers, the authors’ focus on the new generation highly efficient heat exchangers and presentation of novel data and technical expertise not available in the open literature. Next generation micro channels offer record high heat transfer coefficients with pressure drops much less than conventional micro channel heat exchangers. These inherent features promise fast penetration into many mew markets, including high heat flux cooling of electronics, waste heat recovery and energy efficiency enhancement applications, alternative energy systems, as well as applications in mass exchangers and chemical reactor systems. The combination of up to the minute research findings and technical know-how make this book very timely as the search for high performance heat and mass exchangers that can cut costs in materials consumption intensifies.
Next Generation Microchannel Heat Exchangers
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Author : Michael M. Ohadi
language : en
Publisher: Springer Science & Business Media
Release Date : 2012-10-16
Next Generation Microchannel Heat Exchangers written by Michael M. Ohadi and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012-10-16 with Technology & Engineering categories.
In Next Generation Microchannel Heat Exchangers, the authors’ focus on the new generation highly efficient heat exchangers and presentation of novel data and technical expertise not available in the open literature. Next generation micro channels offer record high heat transfer coefficients with pressure drops much less than conventional micro channel heat exchangers. These inherent features promise fast penetration into many mew markets, including high heat flux cooling of electronics, waste heat recovery and energy efficiency enhancement applications, alternative energy systems, as well as applications in mass exchangers and chemical reactor systems. The combination of up to the minute research findings and technical know-how make this book very timely as the search for high performance heat and mass exchangers that can cut costs in materials consumption intensifies.
The Thermal Hydraulic Characterisation Of A Microchannel Heat Exchanger For Use In Next Generation Photonic Integrated Circuits
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Author : Niamh Richardson
language : en
Publisher:
Release Date : 2020
The Thermal Hydraulic Characterisation Of A Microchannel Heat Exchanger For Use In Next Generation Photonic Integrated Circuits written by Niamh Richardson and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2020 with categories.
Thermohydraulic And Mechanical Modeling Of Printed Circuit Heat Exchangers For Next Generation Nuclear Service
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Author : Ian William Jentz
language : en
Publisher:
Release Date : 2021
Thermohydraulic And Mechanical Modeling Of Printed Circuit Heat Exchangers For Next Generation Nuclear Service written by Ian William Jentz and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2021 with categories.
In this work an approach to thermodyraulic and mechanical modeling of a full 3-dimensional Printed Circuit Heat Exchanger is presented. A new approach to Finite Element analysis of the fluid and structure using homogenization of micro-channel behavior is developed. The accuracy of the thermohydrualic model is verified against experiment for a large range of flow conditions. Using the results from the thermohydraulic model as input to the mechanical FE model allows loading and stress within the PCHE to by resolved. Coupling of the thermodynamic and mechanical models allows the performance and mechanical integrity of all parts of the PCHE to be evaluated simultaneously. Motivation for using airfoil PCHEs in s-CO2 applications is given and the design of PCHEs are briefly discussed. A thermohydraulic model using a homogenized heat exchanger thermohydraulics (HHXT) approach has been developed for PCHE applications. The HHXT model provides a fully resolved PCHE model without the complexity inherent in resolving all facets of the micro-channel geometry throughout the core. The HHXT approach expands on previous work by Urquiza in homogenizing the PCHE micro-channel core as an anisotropic media. Flow distribution in the PCHE is determined using a porous media approach. Heat transfer between fluids is modeled using heat transfer coefficients and is coupled to a conduction model of the solid PCHE body. The Homogenized Heatexchanger Thermohydraulics model properly resolves American Society of Mechanical Engineers Boiler and Pressure Vessel Code (BPVC) Sec-3 loading conditions without the complexity inherent in resolving all facets of the PCHE geometry. The accuracy of the model is verified through experimental validation. A purpose designed zig-zag channel test PCHE was tested over a wide range of flow, using 60 separate tests with Reynolds number ranging from 1,790 to 64,200. Embedded fiber-optic temperature sensors measured 2-dimensional temperature distribution within the test recuperator. Along with measurement of inlet and outlet conditions, the internal temperature measurements provide 7,542 distributed measurements for each flow rate tested. This allowed the verification of HHXT against a large set of data. Combined modelling and measurement allowed for better insight into PCHE performance. The interaction of side entrance and transition regions could be resolved. Flow redistribution within the cold CO2 of the zig-zag PCHE was found to be a major factor in the distribution of temperature. Mechanical analysis per BPVC section III design by analysis rules is demonstrated. Linearized stress analysis was used to break the stress within micro-channel walls into membrane and bending components needed in BPVC stress intensity calculations. A homogenized approach to modeling mechanical loads in the full 3-dimensional PCHE is used. The method consisted of separate micro-channel structure and PCHE structure analyses. The resulting model resolved pressurization and thermal stresses within the zig-zag test PCHE. Stress intensities within 108,000 distinct micro-channel walls could be determined. Thermal stress arising from the differential expansion of the PCHE body was found to contribute the most stress. The zig-zag test PCHE meets BPVC section III stress intensity limits at design operating conditions. Additionally the measurement of airfoil micro-channel heat transfer and hydraulic performance is made. As direct internal measurement of bulk CO2 or fluid-wall temperatures within the channels of the airfoil PCHE is not possible, convective heat transfer is calculated from inlet and outlet CO2 conditions and simple models of heat transfer within the recuperator. Since CO2 properties changed over the length of the recuperator, a 1D discrete model of the recuperator for calculating localized values of j and f is presented.
Heat Exchangers
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Author : Jovan Mitrovic
language : en
Publisher: BoD – Books on Demand
Release Date : 2012-03-09
Heat Exchangers written by Jovan Mitrovic and has been published by BoD – Books on Demand this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012-03-09 with Technology & Engineering categories.
Selecting and bringing together matter provided by specialists, this project offers comprehensive information on particular cases of heat exchangers. The selection was guided by actual and future demands of applied research and industry, mainly focusing on the efficient use and conversion energy in changing environment. Beside the questions of thermodynamic basics, the book addresses several important issues, such as conceptions, design, operations, fouling and cleaning of heat exchangers. It includes also storage of thermal energy and geothermal energy use, directly or by application of heat pumps. The contributions are thematically grouped in sections and the content of each section is introduced by summarising the main objectives of the encompassed chapters. The book is not necessarily intended to be an elementary source of the knowledge in the area it covers, but rather a mentor while pursuing detailed solutions of specific technical problems which face engineers and technicians engaged in research and development in the fields of heat transfer and heat exchangers.
Phase Separation In Two Phase Microfluidic Heat Exchangers
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Author : Milnes P. David
language : en
Publisher: Stanford University
Release Date : 2011
Phase Separation In Two Phase Microfluidic Heat Exchangers written by Milnes P. David and has been published by Stanford University this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011 with categories.
Two-phase microfluidic heat exchangers have the potential to meet the large heat dissipation demands of high power electronics and computing systems. Two-phase cooling systems face practical challenges brought on by the growth and advection of the vapor phase in the confined geometries, which lead to large pressure drops, increased thermal resistance and the formation of detrimental flow instabilities. One proposed solution to these issues is phase separation, whereby the vapor is locally separated from the two-phase flow through a porous hydrophobic membrane. This dissertation describes a series of studies conducted to develop an understanding of the factors that influence vapor separation and its impact on the hydraulic and thermal characteristics of two-phase heat exchangers. Flow phenomena are a critical component in developing this understanding of phase separation. High speed visualization of adiabatic and diabatic vaporizing flows was carried out in a single 124[Mu]m by 98[Mu]m copper microchannel with a 65[Mu]m thick, 220nm pore diameter hydrophobic PTFE membrane wall. During adiabatic air-water flow, wavy-stratified and stratified flow dominated lower liquid velocities, while plug and annular type flows dominated at the higher velocities. Analysis found that air removal could be improved by increasing the venting area, increasing the trans-membrane pressure or using thinner, high permeability membranes. Diabatic water-vapor experiments with mass flux velocities of 140 and 340 kg/s-m2 and exit qualities up to 20% found that stratified type flows dominate at lower mass fluxes while cyclical churn-annular flow became more prevalent at the higher mass-flux and quality. The observed flow regimes are hypothesized to play a significant role in determining the pressure drop and heat transfer coefficient during flow boiling. To study the impact of various geometric and membrane factors on the performance of a phase separating microchannel heat exchanger dissipating 100W of heat, a numerical model incorporating vapor separation and transport during two-phase flow boiling in a microchannel was developed. The impact of substrate thermal conductivity and thickness, membrane permeability and thickness, liquid channel density, liquid and vent channel diameter and vent-to-liquid channel diameter ratio was studied and compared for a standard non-venting heat exchanger, a vapor venting heat exchanger and a non-venting heat exchanger occupying the same increased volume as the venting heat exchanger. The numerical study found that the venting heat exchanger had improved pressure drop and device temperatures for all tested conditions when compared against a standard heat exchanger but only under very limited conditions when compared against the volumetrically equivalent non-venting heat exchanger. The study indicates that the best venting heat exchanger performance is achieved when the membrane conductance is of the same order or higher than that of the microchannel; this can be achieved through the use of thin high permeability membranes coupled with small hydraulic diameter microchannels. Finally, a study was conducted to explore the fabrication methods to build a vapor separating heat exchanger and to quantify the operating performance of multichannel silicon and copper phase separating devices. A copper parallel microchannel heat exchanger with nineteen 130[Mu]m square microchannels was built and tested at heat fluxes of up to 820 kW/m2 and water mass fluxes of between 102 and 420 kg/s-m2. Normalized pressure drop was improved by as much as 60% and average substrate temperature by a maximum of 4.4°C between the non-venting control and vapor venting device under similar operating conditions. Comparison between the experimental results and simulation predictions found higher than expected pressure drop improvements at higher mass fluxes and poorer heat transfer coefficients at the lowest mass flux. Based on the flow phenomena study these discrepancies are believed to be due to the mass flux and vapor quality dependent two-phase flow structures. The encouraging experimental and numerical results motivate further study into phase separation methods, materials and flow physics. The development of a high performance phase separating heat exchanger, with the thermal benefits of two-phase boiling flow and the hydraulic benefits of single-phase liquid flow, would strongly enable the adoption and application of two-phase heat exchangers to provide effective and efficient cooling for next generation high power computing systems.
Phase Separation In Two Phase Microfluidic Heat Exchangers
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Author : Milnes P. David
language : en
Publisher:
Release Date : 2011
Phase Separation In Two Phase Microfluidic Heat Exchangers written by Milnes P. David and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011 with categories.
Two-phase microfluidic heat exchangers have the potential to meet the large heat dissipation demands of high power electronics and computing systems. Two-phase cooling systems face practical challenges brought on by the growth and advection of the vapor phase in the confined geometries, which lead to large pressure drops, increased thermal resistance and the formation of detrimental flow instabilities. One proposed solution to these issues is phase separation, whereby the vapor is locally separated from the two-phase flow through a porous hydrophobic membrane. This dissertation describes a series of studies conducted to develop an understanding of the factors that influence vapor separation and its impact on the hydraulic and thermal characteristics of two-phase heat exchangers. Flow phenomena are a critical component in developing this understanding of phase separation. High speed visualization of adiabatic and diabatic vaporizing flows was carried out in a single 124[Mu]m by 98[Mu]m copper microchannel with a 65[Mu]m thick, 220nm pore diameter hydrophobic PTFE membrane wall. During adiabatic air-water flow, wavy-stratified and stratified flow dominated lower liquid velocities, while plug and annular type flows dominated at the higher velocities. Analysis found that air removal could be improved by increasing the venting area, increasing the trans-membrane pressure or using thinner, high permeability membranes. Diabatic water-vapor experiments with mass flux velocities of 140 and 340 kg/s-m2 and exit qualities up to 20% found that stratified type flows dominate at lower mass fluxes while cyclical churn-annular flow became more prevalent at the higher mass-flux and quality. The observed flow regimes are hypothesized to play a significant role in determining the pressure drop and heat transfer coefficient during flow boiling. To study the impact of various geometric and membrane factors on the performance of a phase separating microchannel heat exchanger dissipating 100W of heat, a numerical model incorporating vapor separation and transport during two-phase flow boiling in a microchannel was developed. The impact of substrate thermal conductivity and thickness, membrane permeability and thickness, liquid channel density, liquid and vent channel diameter and vent-to-liquid channel diameter ratio was studied and compared for a standard non-venting heat exchanger, a vapor venting heat exchanger and a non-venting heat exchanger occupying the same increased volume as the venting heat exchanger. The numerical study found that the venting heat exchanger had improved pressure drop and device temperatures for all tested conditions when compared against a standard heat exchanger but only under very limited conditions when compared against the volumetrically equivalent non-venting heat exchanger. The study indicates that the best venting heat exchanger performance is achieved when the membrane conductance is of the same order or higher than that of the microchannel; this can be achieved through the use of thin high permeability membranes coupled with small hydraulic diameter microchannels. Finally, a study was conducted to explore the fabrication methods to build a vapor separating heat exchanger and to quantify the operating performance of multichannel silicon and copper phase separating devices. A copper parallel microchannel heat exchanger with nineteen 130[Mu]m square microchannels was built and tested at heat fluxes of up to 820 kW/m2 and water mass fluxes of between 102 and 420 kg/s-m2. Normalized pressure drop was improved by as much as 60% and average substrate temperature by a maximum of 4.4°C between the non-venting control and vapor venting device under similar operating conditions. Comparison between the experimental results and simulation predictions found higher than expected pressure drop improvements at higher mass fluxes and poorer heat transfer coefficients at the lowest mass flux. Based on the flow phenomena study these discrepancies are believed to be due to the mass flux and vapor quality dependent two-phase flow structures. The encouraging experimental and numerical results motivate further study into phase separation methods, materials and flow physics. The development of a high performance phase separating heat exchanger, with the thermal benefits of two-phase boiling flow and the hydraulic benefits of single-phase liquid flow, would strongly enable the adoption and application of two-phase heat exchangers to provide effective and efficient cooling for next generation high power computing systems.
Compact Heat Exchangers
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Author : C. Ranganayakulu
language : en
Publisher: John Wiley & Sons
Release Date : 2018-02-02
Compact Heat Exchangers written by C. Ranganayakulu and has been published by John Wiley & Sons this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018-02-02 with Technology & Engineering categories.
A comprehensive source of generalized design data for most widely used fin surfaces in CHEs Compact Heat Exchanger Analysis, Design and Optimization: FEM and CFD Approach brings new concepts of design data generation numerically (which is more cost effective than generic design data) and can be used by design and practicing engineers more effectively. The numerical methods/techniques are introduced for estimation of performance deteriorations like flow non-uniformity, temperature non-uniformity, and longitudinal heat conduction effects using FEM in CHE unit level and Colburn j factors and Fanning friction f factors data generation method for various types of CHE fins using CFD. In addition, worked examples for single and two-phase flow CHEs are provided and the complete qualification tests are given for CHEs use in aerospace applications. Chapters cover: Basic Heat Transfer; Compact Heat Exchangers; Fundamentals of Finite Element and Finite Volume Methods; Finite Element Analysis of Compact Heat Exchangers; Generation of Design Data by CFD Analysis; Thermal and Mechanical Design of Compact Heat Exchanger; and Manufacturing and Qualification Testing of Compact Heat Exchanger. Provides complete information about basic design of Compact Heat Exchangers Design and data generation is based on numerical techniques such as FEM and CFD methods rather than experimental or analytical ones Intricate design aspects included, covering complete cycle of design, manufacturing, and qualification of a Compact Heat Exchanger Appendices on basic essential fluid properties, metal characteristics, and derivation of Fourier series mathematical equation Compact Heat Exchanger Analysis, Design and Optimization: FEM and CFD Approach is ideal for senior undergraduate and graduate students studying equipment design and heat exchanger design.
Heat Exchangers
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Author : Abdelhanine Benallou
language : en
Publisher: John Wiley & Sons
Release Date : 2024-06-05
Heat Exchangers written by Abdelhanine Benallou and has been published by John Wiley & Sons this book supported file pdf, txt, epub, kindle and other format this book has been release on 2024-06-05 with Science categories.
The last few decades have seen huge developments in the use of concentrated solar power plants, communications technologies (mobile telephony and 5G networks), the nuclear sector with its small modular reactors and concentrated solar power stations. These developments have called for a new generation of heat exchangers. As well as presenting conventional heat exchangers (shell-and-tube and plate heat exchangers), their design techniques and calculation algorithms, Heat Exchangers introduces new-generation compact heat exchangers, including printed circuit heat exchangers, plate-fin heat exchangers, spiral heat exchangers, cross-flow tube-fin heat exchangers, phase-change micro-exchangers, spray coolers, heat pipe heat exchangers and evaporation chambers. This new generation of heat exchangers is currently undergoing a boom, with applications in on-board equipment in aircraft, locomotives, space shuttles and mobile phones, where the volume of the equipment is one of the most important design parameters.
Application Of Compact Heat Exchangers For Combined Cycle Driven Efficiency In Next Generation Nuclear Power Plants
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Author : Bahman Zohuri
language : en
Publisher: Springer
Release Date : 2016-08-23
Application Of Compact Heat Exchangers For Combined Cycle Driven Efficiency In Next Generation Nuclear Power Plants written by Bahman Zohuri and has been published by Springer this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016-08-23 with Technology & Engineering categories.
Covers the fundamentals of combined-cycle plants to provide background for understanding the progressive design approaches at the heart of the text Discusses the types of compact heat exchanger surfaces, suggesting novel designs that can be considered for optimal cost effectiveness and maximum energy production Undertakes the thermal analysis of these compact heat exchangers throughout the life cycle, from the design perspective through operational and safety assurance stages This book describes the quest to create novel designs for compact heat exchangers in support of emergent combined cycle nuclear plants. The text opens with a concise explanation of the fundamentals of combined cycles, describing their efficiency impacts on electrical power generation systems. It then covers the implementation of these principles in nuclear reactor power systems, focusing on the role of compact heat exchangers in the combined cycle loop and applying them to the challenges facing actual nuclear power systems. The various types of compact heat exchanger surfaces and designs are given thorough consideration before the author turns his attention to discussing current and projected reactor systems, and how the novel design of these compact heat e xchangers can be applied to innovative designs, operation and safety analyses to optimize thermal efficiency. The book is written at an undergraduate level, but will be useful to practicing engineers and scientists as well.