Performance and flow characteristics of nozzles for initially subcooled hot water (influence of turbulence and decompression rate)

Ohta, Junichi; Fujii, Terushige; Akagawa, Koji; Takenaka, Nobuyuki

doi:10.1016/0301-9322(93)90028-s

Cited by 16 publications

(9 citation statements)

References 13 publications

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“…So let's assume a linear expansion between inlet pressure of 5bar and an outlet at 1bar assuming that flashing inception begins at 3.5bar, a linear superheat reduction from 5K to 1K and a linear vapor volume fraction evolution from 0 to 1. These conditions are close to those of the test campaign conducted by [1]. This type of analysis omits 2D effects on the flow.…”

Section: Discussion On the Modelssupporting

confidence: 76%

“…Note that the mass flow in Table 4 does not depend on the outlet pressure; that means that the nozzle operates in critical conditions. The uncertainties of the measured data reported in [1] are within 2% for mass flow rate, 2% for thrust, 1% for pressure and 0.5% for temperature. This leads to an uncertainty of 2.8% for velocity by uncertainty propagation (knowing that thrust is equal to 𝑚̇.…”

Section: Case Studymentioning

confidence: 70%

“…In the early 90's a Japanese team [1] worked on waste heat recovery by impulse turbines using flash nozzles. Various nozzle geometries were tested.…”

Section: Case Studymentioning

confidence: 99%

“…Flash boiling nozzles are the motive elements of various energy conversion components such as twophase impulse turbines [1] or two-phase ejectors [2].…”

Section: Introductionmentioning

confidence: 99%

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Initially sub-cooled liquid flashing flow CFD modeling: closure parameters for a non-symmetric interfacial area density formulation

Sampedro

Nemer

2021

E3S Web Conf.

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A bubble to droplet transition non-symmetric interfacial area density formulation was developed for flash boiling nozzles CFD modeling. This formulation is used in a two fluid Euler- Euler modeling with a thermal phase change model. The regime transition formulation is based on the number of bubbles density and number of droplet density values. The first affects mainly the flow regime close to the nozzle throat and the second parameter affects mainly the flow close to the outlet. The physical factors affecting the calibration values of these parameters are analyzed in this paper with the aim of defining appropriate closure models. The analysis is done using experimental data available in literature. The comparison is done on the mass flow rate and the nozzle outlet velocity. It appears that the number of bubbles density is related to the inlet sub -cooling conditions and that the number of droplets density is affected by the outlet pressure and Reynolds number.

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Section: Discussion On the Modelssupporting

confidence: 76%

Section: Case Studymentioning

confidence: 70%

“…In the early 90's a Japanese team [1] worked on waste heat recovery by impulse turbines using flash nozzles. Various nozzle geometries were tested.…”

Section: Case Studymentioning

confidence: 99%

“…Flash boiling nozzles are the motive elements of various energy conversion components such as twophase impulse turbines [1] or two-phase ejectors [2].…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Initially sub-cooled liquid flashing flow CFD modeling: closure parameters for a non-symmetric interfacial area density formulation

Sampedro

Nemer

2021

E3S Web Conf.

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“…4, the fluid experiences a large pressure drop at the throat. This agrees well with similar results experienced in previous investigations [10] with similar experimental set-up and approximate nozzle geometry, but higher inlet and higher back pressures. …”

Section: Pressure Profilessupporting

confidence: 82%

The efficiency of a two-phase nozzle as a motion force for power generation from low-temperature resources

Vahaji¹,

Akbarzadeh²,

Date³

et al. 2014

WIT Transactions on Engineering Sciences

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Two-phase nozzles could be used as energy conversion devices in geothermal total flow systems or binary fluid systems followed by a trilateral cycle for power generation. In this paper, the efficiency of such nozzles is investigated. Also, a profound research has been done on similar area in the past where mostly high pressure and high temperature energy resources were considered; so, the possibility of utilizing low-temperature energy resources remains limited in the literature. In order to bridge the knowledge gap, the feasibility of utilizing low-temperature resources for power generation is studied in this paper.In this regards, experiments are carried out with the following conditions: a convergent-divergent nozzle is supplied with water at atmospheric pressure with various temperatures at/below 100ºC. This nozzle is connected to a tank that is evacuated by a vacuum pump. The driving force for water to flow through the nozzle is the pressure difference between atmosphere and vacuum pressure in the flash tank. As water is passed through the nozzle, the thermal energy is converted to kinetic energy as a motive force for power generation. The impulse force caused by the jet exiting the nozzle is measured and compared against the ideal case (i.e. isentropic expansion assumption) to calculate the thrust coefficient of the nozzle and evaluate the efficiency of the process. Also, the pressure and temperature profiles along the nozzle are obtained and compared against saturation pressure corresponding to measured temperatures. The results encourage the utilization of low-temperature geothermal energy resources for power generation.

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About the Effect of Two-Phase Flow Formulations on Shock Waves in Flash Metastable Expansions Simulations

Sampedro¹

2023

ERCOFTAC Series

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Two-phase expanders are promising conversion machines that could help in increasing the energy efficiency of several systems such as heat-to-power plants, liquefaction processes or chillers. Expansion of two-phase flows is complex to model since the dynamics of the liquid-gas interactions depend on several factors. This work gives a preliminary insight on the effect of various formulations for liquid-gas interaction terms on the shock waves that may appear in over-expanded flash nozzles simulations. The case study is a water thrust nozzle from literature designed for geothermal energy conversion at inlet temperatures close to 150°C. The compared formulations differ mainly on the homogeneity assumptions regarding momentum and on the interface mass transfer term. The simulations results suggest that these assumptions have a fundamental effect on the flow behavior close to the outlet of the nozzle and in particular on the presence or not of the shock waves. This has meaningful consequences on the velocity profile in the nozzle.

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Performance and flow characteristics of nozzles for initially subcooled hot water (influence of turbulence and decompression rate)

Cited by 16 publications

References 13 publications

Initially sub-cooled liquid flashing flow CFD modeling: closure parameters for a non-symmetric interfacial area density formulation

Initially sub-cooled liquid flashing flow CFD modeling: closure parameters for a non-symmetric interfacial area density formulation

The efficiency of a two-phase nozzle as a motion force for power generation from low-temperature resources

About the Effect of Two-Phase Flow Formulations on Shock Waves in Flash Metastable Expansions Simulations

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