The Experts below are selected from a list of 264 Experts worldwide ranked by ideXlab platform
Somchai Wongwises - One of the best experts on this subject based on the ideXlab platform.
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Review on the experimental studies of refrigerant Flow mechanisms inside short-tube orifices
International Journal of Refrigeration, 2012Co-Authors: Kitti Nilpueng, Somchai WongwisesAbstract:A short-tube orifice is a kind of an expansion device. The advantages of a short-tube orifice are simplicity, low cost, and low starting torque of the compressor as the pressures across the short-tube orifice equalise during the off-cycle. The two-phase Flow mechanisms of refrigerant inside the short-tube orifice are very complicated although its physical configurations are simple. During the past decade, investigations of the mass Flow rate of various refrigerants inside short-tube orifices, which is useful for selecting the proper size in practical applications, have been reported by many researchers. However, few researchers focused on the Flow pattern, Choked Flow, and metastable Flow phenomena inside short-tube orifices, which are necessary for a clear understanding of the Flow behaviour and developing suitable calculation techniques. The aim of this paper is to summarise the evolution of the experimental research on refrigerant Flow characteristics inside short-tube orifices to provide guidelines for future research. © 2011 Elsevier Ltd and IIR. All rights reserved.
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Choked Flow mechanism of hfc 134a Flowing through short tube orifices
Experimental Thermal and Fluid Science, 2011Co-Authors: Kitti Nilpueng, Somchai WongwisesAbstract:Abstract This paper is a continuation of the author’s previous work. New experimental data on the occurrence of Choked Flow phenomenon and mass Flow rate of HFC-134a inside short-tube orifices under Choked Flow condition are presented. Short-tube orifices diameters ranging from 0.406 mm to 0.686 mm with lengths ranging from 1 mm to 3 mm which can be applied to a miniature vapour-compression refrigeration system are examined. The experimental results indicated that the occurrence of Choked Flow phenomena inside short-tube orifices is different from that obtained from short-tube orifice diameters of greater than 1 mm, which are typically used in air-conditioner. The beginning of Choked Flow is dependent on the downstream pressure, degree of subcooling, and length-to-diameter ratio. Under Choked Flow condition, the mass Flow rate is greatly varied with the short-tube orifice dimension, but it is slightly affected by the operating conditions. A correlation of mass Flow rate through short-tube orifices is proposed in terms of the dimensionless parameters. The predicted results show good agreement with experimental data with a mean deviation of 4.69%.
Kitti Nilpueng - One of the best experts on this subject based on the ideXlab platform.
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Review on the experimental studies of refrigerant Flow mechanisms inside short-tube orifices
International Journal of Refrigeration, 2012Co-Authors: Kitti Nilpueng, Somchai WongwisesAbstract:A short-tube orifice is a kind of an expansion device. The advantages of a short-tube orifice are simplicity, low cost, and low starting torque of the compressor as the pressures across the short-tube orifice equalise during the off-cycle. The two-phase Flow mechanisms of refrigerant inside the short-tube orifice are very complicated although its physical configurations are simple. During the past decade, investigations of the mass Flow rate of various refrigerants inside short-tube orifices, which is useful for selecting the proper size in practical applications, have been reported by many researchers. However, few researchers focused on the Flow pattern, Choked Flow, and metastable Flow phenomena inside short-tube orifices, which are necessary for a clear understanding of the Flow behaviour and developing suitable calculation techniques. The aim of this paper is to summarise the evolution of the experimental research on refrigerant Flow characteristics inside short-tube orifices to provide guidelines for future research. © 2011 Elsevier Ltd and IIR. All rights reserved.
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Choked Flow mechanism of hfc 134a Flowing through short tube orifices
Experimental Thermal and Fluid Science, 2011Co-Authors: Kitti Nilpueng, Somchai WongwisesAbstract:Abstract This paper is a continuation of the author’s previous work. New experimental data on the occurrence of Choked Flow phenomenon and mass Flow rate of HFC-134a inside short-tube orifices under Choked Flow condition are presented. Short-tube orifices diameters ranging from 0.406 mm to 0.686 mm with lengths ranging from 1 mm to 3 mm which can be applied to a miniature vapour-compression refrigeration system are examined. The experimental results indicated that the occurrence of Choked Flow phenomena inside short-tube orifices is different from that obtained from short-tube orifice diameters of greater than 1 mm, which are typically used in air-conditioner. The beginning of Choked Flow is dependent on the downstream pressure, degree of subcooling, and length-to-diameter ratio. Under Choked Flow condition, the mass Flow rate is greatly varied with the short-tube orifice dimension, but it is slightly affected by the operating conditions. A correlation of mass Flow rate through short-tube orifices is proposed in terms of the dimensionless parameters. The predicted results show good agreement with experimental data with a mean deviation of 4.69%.
Moonsun Chung - One of the best experts on this subject based on the ideXlab platform.
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Simulation of SBLOCA based on an Improved Choked Flow Model for RELAP5/MOD3 Code
Annals of Nuclear Energy, 2005Co-Authors: Moonsun ChungAbstract:Abstract This paper is a continuation of the present author’s previous publication dealing with a new Choked Flow model for two-phase Flow. The model based on a hyperbolic one-dimensional two-fluid model, where in the momentum equations the terms representing the interfacial pressure difference has been included in lieu of the virtual mass force terms. The new Choked Flow model is an improvement upon the Choked Flow model of the current RELAP5/MOD3 code, which itself is based on the Trapp–Ransom method. The author compares the predictions of this improved model with Trapp–Ransom model and Henry–Fauske model, for an assumed Flow in a vertical pipe. The author simulates a typical PWR system with a hypothetical SBLOCA as well, and compares the system behaviors predicted by RELAP5/MOD3, based on the aforementioned Choked Flow models. He shows that the improved Choked Flow model leads to better predictions.
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simulation of sbloca based on an improved Choked Flow model for relap5 mod3 code
Annals of Nuclear Energy, 2005Co-Authors: Moonsun ChungAbstract:Abstract This paper is a continuation of the present author’s previous publication dealing with a new Choked Flow model for two-phase Flow. The model based on a hyperbolic one-dimensional two-fluid model, where in the momentum equations the terms representing the interfacial pressure difference has been included in lieu of the virtual mass force terms. The new Choked Flow model is an improvement upon the Choked Flow model of the current RELAP5/MOD3 code, which itself is based on the Trapp–Ransom method. The author compares the predictions of this improved model with Trapp–Ransom model and Henry–Fauske model, for an assumed Flow in a vertical pipe. The author simulates a typical PWR system with a hypothetical SBLOCA as well, and compares the system behaviors predicted by RELAP5/MOD3, based on the aforementioned Choked Flow models. He shows that the improved Choked Flow model leads to better predictions.
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Choked Flow calculations of two phase bubbly Flow
Numerical Heat Transfer Part A-applications, 2002Co-Authors: Moonsun Chung, Kwiseok HaAbstract:A new Choked Flow criterion based on the system eigenvalues derived by the characteristic analysis of a hyperbolic nonequilibrium two-fluid model is employed in the RELAP5/MOD3 code. A modification of the Choked Flow model produced by the earlier works of Trapp and Ransom is elaborated so that better predictions of Choked Flow rate can be made in the two-phase bubbly Flow. Marviken Choked Flow tests on the large-scale break of pipes are assessed by using the present criterion. The assessment results demonstrate more accurate predictions of Choked Flow rate in the bubbly Flow regime without any adjustment than those of the earlier calculations by using the equilibrium Choked Flow criterion.
Ivo Furno - One of the best experts on this subject based on the ideXlab platform.
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Two-fluid plasma model for radial Langmuir probes as a converging nozzle with sonic Choked Flow, and sonic passage to supersonic Flow
Physics of Plasmas, 2019Co-Authors: Alan Howling, Ph. Guittienne, Ivo FurnoAbstract:Using the Lambert function, Guittienne et al. [Phys. Plasmas 25, 093519 (2018)] derived two-fluid solutions for radial Langmuir probes in collisionless and isothermal plasma. In this Brief Communication, we point out the close analogy with classical compressible fluid dynamics, where the simultaneous Flows of the ion and electron fluids experience opposite electrostatic body forces in the inward radial Flow of the plasma, which behaves as a converging nozzle. Hence, the assumed boundary condition of sonic Flow of the repelled species at the probe is explained as Choked Flow. The sonic passage from subsonic to supersonic Flow of the attracted species at the sonic radius is also interpreted using classical fluid dynamics. Moreover, the Lambert function can provide a general solution for one-dimensional, isothermal compressible fluids, with several applications.Using the Lambert function, Guittienne et al. [Phys. Plasmas 25, 093519 (2018)] derived two-fluid solutions for radial Langmuir probes in collisionless and isothermal plasma. In this Brief Communication, we point out the close analogy with classical compressible fluid dynamics, where the simultaneous Flows of the ion and electron fluids experience opposite electrostatic body forces in the inward radial Flow of the plasma, which behaves as a converging nozzle. Hence, the assumed boundary condition of sonic Flow of the repelled species at the probe is explained as Choked Flow. The sonic passage from subsonic to supersonic Flow of the attracted species at the sonic radius is also interpreted using classical fluid dynamics. Moreover, the Lambert function can provide a general solution for one-dimensional, isothermal compressible fluids, with several applications.
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two fluid plasma model for radial langmuir probes as a converging nozzle with sonic Choked Flow and sonic passage to supersonic Flow
Physics of Plasmas, 2019Co-Authors: Alan Howling, Ph. Guittienne, Ivo FurnoAbstract:Using the Lambert function, Guittienne et al. [Phys. Plasmas 25, 093519 (2018)] derived two-fluid solutions for radial Langmuir probes in collisionless and isothermal plasma. In this Brief Communication, we point out the close analogy with classical compressible fluid dynamics, where the simultaneous Flows of the ion and electron fluids experience opposite electrostatic body forces in the inward radial Flow of the plasma, which behaves as a converging nozzle. Hence, the assumed boundary condition of sonic Flow of the repelled species at the probe is explained as Choked Flow. The sonic passage from subsonic to supersonic Flow of the attracted species at the sonic radius is also interpreted using classical fluid dynamics. Moreover, the Lambert function can provide a general solution for one-dimensional, isothermal compressible fluids, with several applications.
Eric S Hendricks - One of the best experts on this subject based on the ideXlab platform.
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meanline analysis of turbines with Choked Flow in the object oriented turbomachinery analysis code
54th AIAA Aerospace Sciences Meeting, 2016Co-Authors: Eric S HendricksAbstract:The prediction of turbomachinery performance characteristics is an important part of the conceptual aircraft engine design process. During this phase, the designer must examine the effects of a large number of turbomachinery design parameters to determine their impact on overall engine performance and weight. The lack of detailed design information available in this phase necessitates the use of simpler meanline and streamline methods to determine the turbomachinery geometry characteristics and provide performance estimates prior to more detailed CFD (Computational Fluid Dynamics) analyses. While a number of analysis codes have been developed for this purpose, most are written in outdated software languages and may be difficult or impossible to apply to new, unconventional designs. The Object-Oriented Turbomachinery Analysis Code (OTAC) is currently being developed at NASA Glenn Research Center to provide a flexible meanline and streamline analysis capability in a modern object-oriented language. During the development and validation of OTAC, a limitation was identified in the code's ability to analyze and converge turbines as the Flow approached choking. This paper describes a series of changes which can be made to typical OTAC turbine meanline models to enable the assessment of Choked Flow up to limit load conditions. Results produced with this revised model setup are provided in the form of turbine performance maps and are compared to published maps.