Experiments and Modeling in Churn-turbulent to Annular Flows

Qingzi Zhu, Purdue University

Abstract

The Two-Sensor Droplet-Capable Conductivity Probe (DCCP-2) is designed for local measurement in churn-turbulent to annular flows. It can identify droplets, ligaments, bubbles, and continuous gas. The DCCP-2 is benchmarked with conventional two-sensor electrical conductivity probe and gas rotameter. The DCCP-2’s capability in measuring droplets and bubbles is validated. The DCCP-2 measurement is in good agreement with the rotameter measurement, within ±10% uncertainty. A new software is developed to process the DCCP-2 signal, and calculate the volume fraction, particle chord length, velocity, frequency, etc. for droplets, ligaments and bubbles. Local measurement is performed in churn-turbulent to annular flows using the Two-Sensor Droplet-Capable Conductivity Probe. Radial distribution of basic two-phase flow parameters are obtained for both droplets and ligaments. A framework of dynamically modeling two-phase flows in churn-turbulent to annular flow is developed. A near-wall interface function is proposed to deal with the near-vertical interface in the near wall region. The droplet interfacial area concentration is modeled by an algebraic function based on droplet entrainment and deposition rates, and the probability density function of droplet size distribution. The interfacial area concentration is classified into two groups, which is consistent with the conventional two-group interfacial area transport equation. A two-step approach is proposed for the calculation of interfacial area concentration for the two groups. A practical four-field two-fluid model is derived. The flow field is divided into four categories, and the interfaces are divided into three types accordingly. Four continuity equations will be used as is, but the four momentum equations are simplified to two momentum equations.

Degree

Ph.D.

Advisors

Ishii, Purdue University.

Subject Area

Nuclear engineering

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