Chum flow

At high flowrates when chum flow sets in, the pressure drop undergoes a sudden increase and the coefficient in equation 8.57 increases ... 

Figure 3.5 Flow regimes in vertical downflow (A) bubbly flow (B) slug flow (C) falling film flow (D) bubbly falling film flow (E) chum flow (F) dispersed annular flow. (From Oshimowo and Charles, 1974. Copyright 1974 by Canadian Society of Chemical Engineers, Ottawa, Ont. Reprinted with permission.)...

Jayanti, S., and G. F. Hewitt, 1992, On the Prediction of the Slug-to-Chum Flow Transition in Vertical Two-Phase Flows, Int. J. Multiphase Flow 75 847 860. (3)... 

This well-defined flow pattern is destroyed at higher flow rates and a chaotic type of flow, generally known as chum flow, is established. Over... 

The flow pattern in a capillary can change with an increase or decrease of the gas and liquid flow rates. With a given liquid flow rate, increasing the gas velocity will change the flow pattern from bubbly flow, via slug flow and chum flow, to annular flow. 

Slug flow-chum flow transition. As the gas flow is increased even more, a transition to chum flow occurs. The subjective discrimination between slug flow and chum flow makes it difficult to identify the transition exactly. Taitel et al. [3] use the definition that is based on the behavior of the liquid film between the Taylor bubble and the wall. In this case the chum flow is characterized as the condition where oscillatory motion of the liquid is observed. 

Chum flow-segmentedflow transition. This transition is an entry region phenomenon associated with the existence of slug flow further along the pipe, and is described by Taitel et al. [3] as follows ... 

Chum flow or slug flow-annular (dispersed) flow transition. The flow becomes annular when the gas flow rates are enhanced to a certain point. The high gas flow rate causes a wavy interface of the liquid film. As a consequence, parts of the waves will enter the gas core as entrained drops. This results in an upward flow direction of the liquid, due both to interfacial shear and to drag on the waves and drag on the droplets. Annular flow can therefore exist only when the gas velocity is sufficient to lift the droplets in the gas core. The minimum gas velocity required to suspend a drop is determined from the balance between the gravity and drag forces on the drop. 

As depicted in Figure 8.34, the flow patterns formed in a vertical tube follow a trend with increasing gas flow of bubble flow, slug flow, chum flow, and annular flow. These regimes are described briefly below. 

Chum Flow is somewhat similar to slug flow but is more chaotic, frothy, and disordered. 

Chum flow. Here the slug flow regime breaks down to form a region in which liquid is carried upward in large waves, between which a liquid film at the wall may fall downward. Annular flow. Here there is a liquid film carried upward on the walls of the channel, with the vapor flowing in the center of the channel. Usually the vapor contains a dispersion of fine droplets of liquid entrained from the liquid film. 

Calculate the characteristic dimensionless velocity at the smface for churn turbulent flow Wg,a for turbulent chum flow Wg must be larger than Wg,a, where... 

In small channels, a number of flow patterns can be observed, and the same terminology and classifications as in large channels are commonly used. Because of the dominance of the surface tension forces, stratified flow is rarely observed in small channels. In general, bubble flow appears at low gas flow rates. As the gas flow rate increases, Taylor bubbles form. With further increase in the gas flow rate, annular flow appears with the liquid forming an annulus which wets the wall. At high gas and liquid flow rates, chum flow occurs where there is a liquid film at the wall and the gas flow in the center is interrupted by the firequent appearance of frothy bubbles and slugs. 

Chum flow. At very high velocities, regular flow patterns cease to exist and a chaotic flow appears, in which the sizes and shapes of droplets/bubbles vary widely. 

Froth Flow or Chum Flow (7) Bubbly-Annular Flow... 

Figure 5.45 Schematic showing various gas-liquid flow patterns observed in capillary channels (a) film flow, (b) bubbly flow, (c) segmented flow (Taylor flow), (d) chum flow, and (e) annular flow...

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