Propagation of rarefaction waves in bubble flow with evaporation.

Nakagawa, Masafumi; Mamiya, Naohisa

doi:10.1299/kikaib.52.650

Cited by 2 publications

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“…In particular, it is important to elucidate the mixing process of the two-phase fluid and the suctioned vapor in the mixing section of the two-phase ejector in a refrigeration cycle. There are many studies (Nakagawa and Mamiya 1986) that treat the expansion wave of two-phase flow with phase change with a one-dimensional approach. However, there are few that treat it with a two-dimensional approach (Marble 1963).…”

Section: Introductionmentioning

confidence: 99%

Analysis of Expansion Waves Appearing in the Outlets of Two-Phase Flow Nozzles

Nakagawa¹,

Harada

Berana

2009

HVAC&R Research

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Two-phase flow nozzles are used in the total flow systems of geothermal power plants and in the ejector refrigeration cycle. The purpose of the present study is to theoretically elucidate the characteristics of expansion waves at the outlets of supersonic two-phase flow nozzles. Two-dimensional basic equations for compressible two-phase flow were derived by incorporating the equation of momentum transfer between the phases into equations of gas dynamics. In this study, the theoretical analyses were carried out by focusing on momentum-relaxation phenomena in high-speed vapor-mist flow. Expansion waves occurring right after two-phase flow nozzles were calculated by using the CIP method. The calculated expansion curves were compared with the experimentally obtained curves, and the two showed close resemblance.

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Section: Introductionmentioning

confidence: 99%

Analysis of Expansion Waves Appearing in the Outlets of Two-Phase Flow Nozzles

Nakagawa¹,

Harada

Berana

2009

HVAC&R Research

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Expansion Waves at the Outlet of the Supersonic Two-Phase Flow Nozzle

Nakagawa

Miyazaki²,

Harada

et al. 2007

JTST

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Two-phase flow nozzles are used in the total flow system of geothermal power plants and in the ejector of the refrigeration cycle, etc. One of the most important functions of the two-phase flow nozzle is converting two-phase flow thermal energy into kinetic energy. The kinetic energy of the two-phase flow exhausted from a nozzle is available for all applications of this type. In the case of non-best fitting expansion conditions, when the operation conditions of the supersonic nozzle are widely chosen, there exist shock waves or expansion waves at the outlet of the nozzle. Those waves affect largely the energy conversion efficiency of the two-phase flow nozzle. The purpose of the present study is to elucidate character of the expansion waves at the outlet of the supersonic two-phase flow nozzle. High-pressure hot water blowdown experiments have been carried out. The decompression curves of the expansion waves are measured by changing the flowrate in the nozzle and inlet temperature of the hot water. The back pressures of the nozzle are also changed in those experiments. The expansion angles of the two-phase flow flushed out from the nozzle are measured by means of the photograph. The experimental results show that the decompression curves are different from those predicted by the isentropic homogeneous two-phase flow theory. The regions where the expansion waves occur become wide due to the increased outlet speed of the two-phase flow. The qualitative dependency of this expansion character is the same as the isentropic homogeneous flow, but the values obtained from the experiments are quite different. When the back pressure of the nozzle is higher, these regions do not become small in spite of the supersonic two-phase flow. This means that the disturbance in the downstream propagates to the upstream. It is shown by the present experiments that the expansion waves in the supersonic two-phase flow of water have a subsonic feature. The measured expansion angles become larger with increasing flowrate of the two-phase flow and decreasing back pressures.

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Propagation of rarefaction waves in bubble flow with evaporation.

Cited by 2 publications

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Analysis of Expansion Waves Appearing in the Outlets of Two-Phase Flow Nozzles

Analysis of Expansion Waves Appearing in the Outlets of Two-Phase Flow Nozzles

Expansion Waves at the Outlet of the Supersonic Two-Phase Flow Nozzle

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