Semi-annular flow

Bubbly Plug flow Semi-annular Wavy flow Annular flow Spray... 

Slug/semi-annular flow. Here both slug and semi-annular flows were present. The vapor velocity increased with the heat flux and the rear of elongated bubbles began to break up (Fig. 2.30d). Coalescence was no longer clean and created a churn-like zone where the liquid slug had been. 

Semi-annular flow. Liquid slugs were non-existent (Fig. 2.30e). A liquid film formed at the tube wall with a nearly continuous central vapor core, truncated periodically by churning liquid-vapor zones, which disappear gradually. 

Semi annular flow at (f) Wavy annular flow at =82%... 

Slug/semi nnularflow O Semi-annular flow... 

Semi-annular flow is the flow in which the flow alternates mostly between A and C. The time-averaged void fraction is greater than 0.8. 

To determine the dominant frequency of excitation, the near-fleld acoustic spectrum was obtained using a microphone. Typical near-fleld acoustic spectra for an excited jet and a natural jet are shown and compared in Fig. 29.5. When multiple peaks were observed in the spectrum, the peak with the highest spectral amplitude was denoted as the excitation frequency. By systematically varying the dimensions of the cavity, flow excitation occurred over a wide range of frequencies (4-40 kHz). Table 29.2 summarizes the normalized data. Initial tests were performed with semi-annular cavities to eliminate possible... 

Unstable Slug Flow Froth, Turbulent, Semi-Annular) in Vertical Tubes... 

Slug/semi-annular flow Here both slug and semi-aimular flows are present. The bubble velocity increases with heat flux and the rear of the elongated bubbles begin to break up (Figure 3.2d). Coalescence is no longer dean but instead creates a chum-like zone in place of the liquid slug. 

Costello, C. R, and W. J. Frea, 1965, A Salient Non-Hydrodynamic Effect on Pool Boiling Burnout of Small Semi Cylindrical Heaters, AIChE Chem. Eng. Prog. Symp. Ser. 6/(57) 258-268. (2) Cousins, L. B., W. H. Denton, and G. F. Hewitt, 1965, Liquid Mass Transfer in Annular Two-Phase Flow, UK Rep. AERE-R-4926, Harwell, England. (5)... 

The CNMMR model with laminar flow liquid stream in the annular region consists of three ordinary differential equations for the gas in the tube core and two partial differential equations for the liquid in the annular region. These equations are coupled through the diffusion-reaction equations inside the membrane and boundary conditions. The model can be solved by first discretizing the liquid-phase mass balance equations in the radial direction by the orthogonal collocation technique. The resulting equations are then solved by a semi-implicit integration procedure [Harold etal., 1989]. 

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