Multidimensional Modeling of Condensing Two-phase Ejector Flow PDF Download
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Author: Michael Colarossi
Publisher:
ISBN:
Category : Computational fluid dynamics
Languages : en
Pages : 85
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Book Description
Condensing ejectors utilize the beneficial thermodynamics of condensation to produce an exiting static pressure that can be in excess of either entering static pressure. The phase change process is driven by both turbulent mixing and interphase heat transfer. Semi-empirical models can be used in conjunction with computational fluid dynamics (CFD) to gain some understanding of how condensing ejectors should be designed and operated. The current work describes the construction of a multidimensional simulation capability built around an Eulerian pseudo-fluid approach. The transport equations for mass and momentum treat the two phases as a continuous mixture. The fluid is treated as being in a non-thermodynamic equilibrium state, and a modified form of the homogenous relaxation model (HRM) is employed. This model was originally intended for representing flash-boiling, but with suitable modification, the same ideas could be used for condensing flow. The computational fluid dynamics code is constructed using the open-source OpenFOAM library. Fluid properties are evaluated using the REFPROP database from NIST, which includes many common fluids and refrigerants. The working fluids used are water and carbon dioxide. For ejector flow, simulations using carbon dioxide are more stable than with water. Using carbon dioxide as the working fluid, the results of the validation simulations show a pressure rise that is comparable to experimental data. It is also observed that the flow is near thermodynamic equilibrium in the diffuser for these cases, suggesting that turbulence effects present the greatest challenge in modeling these ejectors.
Author: Michael Colarossi
Publisher:
ISBN:
Category : Computational fluid dynamics
Languages : en
Pages : 85
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Book Description
Condensing ejectors utilize the beneficial thermodynamics of condensation to produce an exiting static pressure that can be in excess of either entering static pressure. The phase change process is driven by both turbulent mixing and interphase heat transfer. Semi-empirical models can be used in conjunction with computational fluid dynamics (CFD) to gain some understanding of how condensing ejectors should be designed and operated. The current work describes the construction of a multidimensional simulation capability built around an Eulerian pseudo-fluid approach. The transport equations for mass and momentum treat the two phases as a continuous mixture. The fluid is treated as being in a non-thermodynamic equilibrium state, and a modified form of the homogenous relaxation model (HRM) is employed. This model was originally intended for representing flash-boiling, but with suitable modification, the same ideas could be used for condensing flow. The computational fluid dynamics code is constructed using the open-source OpenFOAM library. Fluid properties are evaluated using the REFPROP database from NIST, which includes many common fluids and refrigerants. The working fluids used are water and carbon dioxide. For ejector flow, simulations using carbon dioxide are more stable than with water. Using carbon dioxide as the working fluid, the results of the validation simulations show a pressure rise that is comparable to experimental data. It is also observed that the flow is near thermodynamic equilibrium in the diffuser for these cases, suggesting that turbulence effects present the greatest challenge in modeling these ejectors.
Author: Milan N. Šarevski
Publisher: Butterworth-Heinemann
ISBN: 0081007345
Category : Science
Languages : en
Pages : 306
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Book Description
Water (R718) Turbo Compressor and Ejector Refrigeration/Heat Pump Technology provides the latest information on efficiency improvements, a main topic in recent investigations of thermal energy machines, plants, and systems that include turbo compressors, ejectors, and refrigeration/heat pump systems. This, when coupled with environmental concerns, has led to the application of eco-friendly refrigerants and to a renewed interest in natural refrigerants. Within this context, readers will find valuable information that explores refrigeration and heat pump systems using natural refrigerants, polygeneration systems, the energy efficiency of thermal systems, the utilization of low temperature waste heat, and cleaner production. The book also examines the technical, economic, and environmental reasons of R718 refrigeration/heat pump systems and how they are competitive with traditional systems, serving as a valuable reference for engineers who work in the design and construction of thermal plants and systems, and those who wish to specialize in the use of R718 as a refrigerant in these systems. Describes existing novel R718 turbo compressor and ejector refrigeration/heat pump systems and technologies Provides procedures calculating and optimizing cycles, system components, and system structures Estimates the performance characteristics of the thermal systems Exposes the possibilities for wider applications of R718 systems in the field of refrigeration and heat pumps
Author: Alessandro Mauro
Publisher: MDPI
ISBN: 3039219820
Category : Technology & Engineering
Languages : en
Pages : 234
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Book Description
In recent years, the interest of the scientific community towards efficient energy systems has significantly increased. One of the reasons is certainly related to the change in the temperature of the planet, which has increased by 0.76 °C with respect to preindustrial levels, according to the Intergovernmental Panel on Climate Change (IPCC), and is still increasing. The European Union considers it vital to prevent global warming from exceeding 2 °C with respect to pre-industrial levels, as it has been proven that this will result in irreversible and potentially catastrophic changes. These changes in climate are mainly caused by greenhouse gas emissions related to human activities, and can be drastically reduced by employing energy systems for the heating and cooling of buildings, as well as for power production, characterized by high efficiency levels and/or based on renewable energy sources. This Special Issue, published in the Energies journal, includes 13 contributions from across the world, including a wide range of applications such as hybrid residential renewable energy systems, desiccant-based air handling units, heat exchanges for engine WHR, solar chimney systems, and other interesting topics.
Author: Xin-rong Zhang
Publisher: John Wiley & Sons
ISBN: 1118380045
Category : Science
Languages : en
Pages : 320
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Book Description
A timely and comprehensive introduction to CO2 heat pump theory and usage A comprehensive introduction of CO2 application in heat pump, authored by leading scientists in the field CO2 is a hot topic due to concerns over global warming and the 'greenhouse effect'. Its disposal and application has attracted considerable research and governmental interest Explores the basic theories, devices, systems and cycles and real application designs for varying applications, ensuring comprehensive coverage of a current topic CO2 heat transfer has everyday applications including water heaters, air-conditioning systems, residential and commercial heating systems, and cooling systems
Author: Gaspar, Pedro Dinis
Publisher: IGI Global
ISBN: 1466683996
Category : Technology & Engineering
Languages : en
Pages : 1037
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Book Description
In recent years, the sustainability and safety of perishable foods has become a major consumer concern, and refrigeration systems play an important role in the processing, distribution, and storage of such foods. To improve the efficiency of food preservation technologies, it is necessary to explore new technological and scientific advances both in materials and processes. The Handbook of Research on Advances and Applications in Refrigeration Systems and Technologies gathers state-of-the-art research related to thermal performance and energy-efficiency. Covering a diverse array of subjects—from the challenges of surface-area frost-formation on evaporators to the carbon footprint of refrigerant chemicals—this publication provides a broad insight into the optimization of cold-supply chains and serves as an essential reference text for undergraduate students, practicing engineers, researchers, educators, and policymakers.
Author: Peter Menegay
Publisher:
ISBN:
Category : Two-phase flow
Languages : en
Pages : 148
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Book Description
Code results. Variable parameters in the code, such as droplet diameter and turbulence constants, are shown to have a large influence on the results. Results are shown in which an unexpected problem, separation in the mixing section, occurs. Also described is the distribution of liquid across the mixing section, which matches qualitative experimental observations. From these results, conclusions regarding ejector design and two-phase CFD modelling are drawn.
Author: Guang-Fa Yao
Publisher:
ISBN:
Category : Fluid dynamics
Languages : en
Pages : 558
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Book Description
Author: Sadik Kakaç
Publisher: Springer Science & Business Media
ISBN: 9400927908
Category : Technology & Engineering
Languages : en
Pages : 1090
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Book Description
Two-phase flow heat exchangers are vital components of systems for power generation, chemical processing, and thermal environment control. The art and science of the design of such heat exchangers have advanced considerably in recent years. This is due to better understanding of the fundamentals of two-phase flow and heat transfer in simple geometries, greater appreciation of these processes in complex goemetries, and enhanced predictive capability through use of complex computer codes. The subject is clearly of great fundamental and practical importance. The NATO ASIan Thermal-Hydraulic Fundamentals and Design of Two-Phase Flow Heat Exchangers was held in Povoa de Varzim (near Porto), Portugal, July 6-17, 1987. participating in the organization of" the ASI were the Department of Mechanical Engineering and the Clean Energy Research Institute, University of Miami; Universidade do Porto; and the Department of Mechanical Engineering, Aeronautical Eng ineer ing, and Mechanics, Rensselaer Polytechnic Institute. The ASI was arranged primarily as a high-level teaching activity by experts representing both academic and industrial viewpoints. The program included the presentation of invited lectures, a limited number of related technical papers and discussion sessions.
Author: Mark Joseph Motzer
Publisher:
ISBN:
Category :
Languages : en
Pages : 566
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Book Description
Author: S. Mostafa Ghiaasiaan
Publisher: Cambridge University Press
ISBN: 1316785300
Category : Technology & Engineering
Languages : en
Pages : 1322
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Book Description
Providing a comprehensive introduction to the fundamentals and applications of flow and heat transfer in conventional and miniature systems, this fully enhanced and updated edition covers all the topics essential for graduate courses on two-phase flow, boiling, and condensation. Beginning with a concise review of single-phase flow fundamentals and interfacial phenomena, detailed and clear discussion is provided on a range of topics, including two-phase hydrodynamics and flow regimes, mathematical modeling of gas-liquid two-phase flows, pool and flow boiling, flow and boiling in mini and microchannels, external and internal-flow condensation with and without noncondensables, condensation in small flow passages, and two-phase choked flow. Numerous solved examples and end-of-chapter problems that include many common design problems likely to be encountered by students, make this an essential text for graduate students. With up-to-date detail on the most recent research trends and practical applications, it is also an ideal reference for professionals and researchers in mechanical, nuclear, and chemical engineering.
