The Structure of Complex Air-water Flows: Studies of Void Fraction and Liquid Phase Axial Mixing in a Microbubble-enhanced Gas-liquid Mixer and a Model Nuclear Fuel Rod Bundle
Başlık:
The Structure of Complex Air-water Flows: Studies of Void Fraction and Liquid Phase Axial Mixing in a Microbubble-enhanced Gas-liquid Mixer and a Model Nuclear Fuel Rod Bundle
Yazar:
Kleinbart, Simon, author.
ISBN:
9780438002739
Yazar Ek Girişi:
Fiziksel Tanımlama:
1 electronic resource (249 pages)
Genel Not:
Source: Dissertation Abstracts International, Volume: 79-10(E), Section: B.
Advisors: Masahiro Kawaji Committee members: Jyeshtharaj B. Joshi; Taehun Lee; Charles Maldarelli; Shripad Revankar.
Özet:
This thesis seeks to characterize the two-phase air-water flow in two different complex flow systems by measuring and analyzing the axial dispersion coefficient and the void fraction. One system is a gas-liquid mixer in which high speed liquid jets generate a suspension of microbubbles in surfactant-enhanced water. This system has been constructed at two scales: 0.1 m diameter and 0.29 m. The other is a square channel containing a 4 by 4 array of cylindrical rods, modelled on a nuclear fuel rod assembly.
In the gas-liquid mixer, void fraction and axial dispersion are measured to assess the separate effects of surfactant (sodium dodecyl sulfate) concentration, gas sparging location within the flow, and scale-up. Bulk void fraction measurements are analyzed using the drift-flux model.
Additionally, two developing technologies for measuring high-resolution void fraction distributions are assessed. These are electrical resistance tomography (ERT) and the wire mesh sensor (WMS). They are both compared to the established void fraction measurement techniques of gamma densitometry and the pressure difference method. They are also discussed in the context of the tradeoff they represent between minimal disturbance of the flow (ERT) and maximal elegant simplicity of raw signal reconstruction (WMS).
In the rod bundle, the water is doped with 1.5% pentanol in order to drastically lower the surface tension of an atmospheric pressure air-water system to a level (∼0.03 N/m) that might be encountered in the high pressure steam-water flow of a nuclear reactor core. The effect of this reduction of surface tension is investigated by measuring the void fraction and axial dispersion. Axial dispersion is measured in both the central subchannel and a corner subchannel. A correlation is developed, inspired by one for dilute aqueous alcohol solutions in standard bubble columns, which relates the axial dispersion coefficient to the surface tension of the fluid and the hydraulic diameter of the subchannel. Bulk void fraction measurements are compared to the drift-flux model.
For both systems, a routine is presented for calculating the axial dispersion coefficient by using a measured upstream concentration versus time curve as the inlet boundary condition to numerically solve the advection-dispersion equation, [Special characters omitted], and fitting the solution to a downstream concentration curve by adjusting D. The method also uses void fraction measurements to generate an available area-corrected velocity (equal to the superficial velocity divided by the liquid fraction) for the input parameter, V.
Notlar:
School code: 1606
Tüzel Kişi Ek Girişi:
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Yer Numarası | Demirbaş Numarası | Shelf Location | Lokasyon / Statüsü / İade Tarihi |
---|---|---|---|
XX(678007.1) | 678007-1001 | Proquest E-Tez Koleksiyonu | Arıyor... |
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