Maximum Two-Phase Flow Rates of Sub-Cooled Nitrogen Through a Sharp-Edged Orifice

Simoneau, R. J.

doi:10.1007/978-1-4757-0208-8_39

Cited by 6 publications

(9 citation statements)

References 7 publications

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“…For short nozzles or orifices uncertainties may exist implying that geometry might have less influence. As reported in the NASA experiment [16] considered in the present study, the flashing jet vaporises within the orifice leading to an alteration of the flow regime and the measured flow coefficient. In the present numerical simulations, the metastable jet exists inside the orifice and phase change starts at the tip of the inlet corners.…”

Section: Numerical Implementationmentioning

confidence: 76%

“…The current solver is based on the RANS approach. Validations have been conducted using the NASA experiments [16] involving liquid nitrogen jets flowing within short-edged orifices for a large range of pressures and different inlet temperatures. The flash-boiling model employs a semi-empirical formulation, derived for water but proved to be applicable for cryogenic nitrogen as well.…”

Section: Resultsmentioning

confidence: 99%

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Numerical simulation of flash-boiling through sharp-edged orifices

Lyras¹,

Dembele²,

Vyazmina³

et al. 2017

Int. J. CMEM

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Flash boiling is the rapid phase change of a pressurised fluid that emerges to ambient conditions below its vapour pressure. Flashing of a flowing liquid through an orifice or a nozzle can occur either inside or outside the nozzle depending on the local pressure and geometry. Vapour generation during flashing leads to interfacial interactions that eventually influence the jet.Empirical models in the literature for simulating the inter-phase heat transfer employ many simplifying assumptions, which limits their applicability. Typical models, usually derived from cavitation, fail to describe the physics of heat and mass transfer, making them unreliable for flashing. The Homogeneous Relaxation Model (HRM) is a reliable model able to capture heat transfer under these conditions accounting for the non-equilibrium vapour generation. This approach uses a relaxation term in the transport equation for the vapour. On the basis of the generic compressible flow solver within the open source computational fluid dynamics (CFD) code OpenFOAM, the HRM has been implemented to create a dedicated new solver HRMSonicELSAFoam. An algorithm that links the standard pressure-velocity coupling algorithm to the HRM is used. In this method, a pressure equation is derived which employs the continuity equation including compressibility effects. A relaxation term has been defined such that the instantaneous quality would relax to the equilibrium value over a given timescale. Although it is possible to consider this timescale constant, it is calculated via an empirical correlation in the present study.Validations have been carried out by simulating two-phase flows through sharp-edged orifices. The relatively good agreement achieved has demonstrated that the solver accurately calculates the pressure and vapour mass fraction. This demonstrates the potential of HRMSonicELSAFoam for flash boiling simulations and predicting the properties of the subsequent flash atomisation.

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Section: Numerical Implementationmentioning

confidence: 76%

Section: Resultsmentioning

confidence: 99%

Numerical simulation of flash-boiling through sharp-edged orifices

Lyras¹,

Dembele²,

Vyazmina³

et al. 2017

Int. J. CMEM

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show abstract

“…Previous studies in flashing jets indicate a rapid phase change as soon as the local pressure drops lower than the saturation pressure. The initiation of this phase change is more likely to happen within the nozzle for longer nozzles but is also possible for short nozzles with L/D less than seven like here, even in low superheat degrees [8]. The jet vaporises within the nozzle, and the flow separation at the sharp inlet corners results in a pressure drop and consequently in phase change (for more details see in [21]).…”

Section: Resultsmentioning

confidence: 95%

“…Despite the simplifications it suffers from, it is a logical approach to the problem since after the primary atomisation and the consequent break-up, the liquid structures become small enough to resemble spherical droplets. Experimental studies for water [5][6][7] and various cryogenic fluids like liquid nitrogen in [8] indicate that two-phase jets emerging through a nozzle might begin flashing with a severe impact on the spray. Numerical works of Lee et al in [9] and Schmidt et al in [10] also agree with this change in the disintegration regime.…”

Section: Introductionmentioning

confidence: 99%

Numerical simulation of superheated jets using an Eulerian method.

Lyras¹,

Dembele²,

Vendra

et al. 2017

Proceedings ILASS–Europe 2017. 28th Conference on Liquid Atomization and Spray Systems

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Flash boiling is the rapid phase change of a pressurised fluid that emerges in ambient conditions below its vapour pressure. Flashing can occur either inside or outside the nozzle depending on the local pressure and geometry and the bubble formation leads to interfacial interactions that eventually influence the emerging spray. Lagrangian methods which exist in literature to simulate the flash atomisation and inter-phase heat transfer employ many simplifying assumptions. Typically, sub-models used for the break-up, collisions and evaporation introduce an extensive empiricism that might result in unrealistic predictions for cases like flashing. In this study, a fully Eulerian approach is selected employing the Σ − Y model proposed by Vallet and Borghi. The model tracks liquid structures of any shape and computes the spray characteristics comprising a modified version for the transport equation of the surface density. The main goal of this study is to investigate the performance of this model in flash boiling liquids using the Homogeneous Relaxation Model (HRM) developed by Downar-Zapolski, a model capable of capturing the heat transfer under sudden depressurisation conditions accounting for the non-equilibrium vapour generation. The model in this present study considers that the instantaneous quality would relax to the equilibrium value over a given timescale which is calculated using the flow field values. A segregated approach linking the HRM and Σ − Y is implemented in a compressible formulation in an attempt to quantify the effects of flash boiling in the spray dynamics. The developed model is naturally implemented in RANS in a dedicated solver HRMSonicELSAFoam. Results from simulations of two-phase jets of different subcooled fluids through sharp-edged orifices show that the proposed approach can accurately simulate the primary atomisation and give reliable predictions for the droplet sizes and distribution. Strong effects of the flashing and turbulent mixing on the jet are demonstrated. The model is tested for turbulent flows within small nozzles and was developed within the open source code OpenFOAM. KeywordsFlash-boiling, atomisation, ELSA model. IntroductionFlashing jets occur when a high-pressure liquid flowing through a nozzle or an orifice is suddenly exposed to a low-pressure environment, becoming superheated if it is not already so. Flashing is characterised by a rapid phase change along the jet and bubble nucleation within the liquid core that influences the spray formation [1,2]. Flashing is very important in safety studies in cases of accidental releases of a liquefied flammable gas through a small crack in the pipeline system. In the aerosol industry it can be used to control nucleation having the advantage of producing sprays with very fine droplets within small domains [3]. In its dense part, the two-phase jet might appear in different forms like bubbly, slug or annular and the nucleation is possible to start upstream of the orifice (a process generally termed internal flashing) or at ...

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“…Liquid nitrogen (LIN) releases were conducted at Lewis Research Center in 1975, by R.J Simoneau . Flow rates were measured across sharp‐edged orifices for different pressures with temperatures ranging from subcooled liquid to supercritical.…”

Section: Analysis Of Relevant Data Setsmentioning

confidence: 99%

Quantifying the mass discharge rate of flashing two phase releases through simple holes to the atmosphere

Spicer

Miller

2018

Process Safety Progress

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Many toxic industrial chemicals (TICs) such as chlorine and ammonia are stored as liquids at ambient temperature which flash when released to atmospheric pressure. Sponsored by the Chemical Security Analysis Center (CSAC) of the U.S. Department of Homeland Security, the Defense Threat Reduction Agency (DTRA) of the U.S. Department of Defense, and Transport Canada, the Jack Rabbit II tests were designed to release liquid chlorine at ambient temperature in quantities of 4,500–18,000 kg (5 to 20 T) to quantify the hazards of catastrophic release at scales represented by rail and truck transport vessels. All trials were conducted releasing chlorine through a 15.2 cm (6 in) circular breach in the 9,100 kg (10 T) capacity test vessel (disseminator) at different orientations (vertically downward, 45° below horizontal, and vertically up). A final 18,000 kg (20 T) release was made vertically downward using a truck vessel. This article analyzes disseminator load cell data to determine the mass release rate. Along with this data, previously published data are also considered to quantify the impact on release rate of flash fraction and superheat limit temperature for various materials. This work develops a general approach to quantifying the mass release rate of flashing two phase releases of TICs and other flashing liquids such as cryogenics. © 2018 American Institute of Chemical Engineers Process Process Saf Prog 37:382–396, 2018

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Maximum Two-Phase Flow Rates of Sub-Cooled Nitrogen Through a Sharp-Edged Orifice

Cited by 6 publications

References 7 publications

Numerical simulation of flash-boiling through sharp-edged orifices

Numerical simulation of flash-boiling through sharp-edged orifices

Numerical simulation of superheated jets using an Eulerian method.

Quantifying the mass discharge rate of flashing two phase releases through simple holes to the atmosphere

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