Engineering topics
Hoxie, Chris
Publications and source records attributed to Hoxie, Chris.
Evaluation of interfacial area transport models for horizontal bubbly flow
This paper presents evaluation results of interfacial area transport equation (IATE) for horizontal air-water bubbly flow. The steady-state one-dimensional, one-group IATE for adiabatic air-water bubbly flow developed by Talley [1] is employed in the current evaluation study. The models evaluated include: (a) drift-flux-based closure relations for void-weighted bubble velocity and void fraction; (b) frictional pressure drop model based on the Lockhart-Martinelli approach; (c) bubble interaction mechanisms; and (d) covariance associated with asymmetric bubble distribution in horizontal two-phase flow. In order to evaluate the models, a local two-phase flow database obtained by the four-sensor conductivity probe in fourteen different test conditions is employed, which covers a wide range of flow conditions in horizontal bubbly flow regime, with superficial liquid and gas velocities ranging from 3.50-6.00 m/s and 0.09- 1.00 m/s, respectively. It is demonstrated that both the void weighted bubble velocity and void fraction are predicted well with an average percent difference of ±2.7%. The fictional pressure loss can be predicted with an average percent difference of ±1.12%. The covariance parameters calculated from the modeling approach generally compare well with those calculated from experimental data within ±20% difference. It is found that the IATE generally predicts the measured interfacial area concentration with an average percent difference of ±5.7%. Furthermore, the effect of liquid velocity on individual bubble interaction mechanisms is investigated. It is found that both the contributions of random collision and turbulent impact decrease as liquid velocity decreases. (authors)
Image Analysis for Plug Bubbles in Horizontal Flow
Horizontal plug flow is different from horizontal slug flow in that relatively few small bubbles exist in plug flow, whereas slug flow is characterized by highly aerated liquid slugs and liquid films. While the nose position and nose propagation velocity of plug bubbles may provide physical insights in understanding the flow regime transition mechanism between the plug and slug flows, few systematic investigations on these parameters have been performed in previous research. In view of this, this paper presents the development of an image processing method for the purpose of (a) obtaining data for nose position and nose propagation velocity of plug bubbles and (b) benchmarking local four-sensor conductivity probe measurements of time-averaged bubble velocity and void fraction. (authors)
Drift-flux Analysis in Horizontal Two-phase Flow
While the most detailed approach to model two-phase flows is the two-fluid model, the drift-flux model may also provide effective methods for estimating one-dimensional two-phase flow parameters. For example, in the current nuclear system analysis codes, the interfacial drag force is a function of the void fraction, drift velocity, and area-averaged relative velocity, which are estimated based on drift-flux approach. While correlations for these parameters exist for vertical two-phase flows, correlations for horizontal two-phase flows have not been developed. (authors)