Flow in horizontal tubes

FIG. 23-25 Typ es of industrial gas/Hqiiid reactors, (a) Tray tower, (h) Packed, counter current, (c) Packed, parallel current, (d) Falling liquid film, (e) Spray tower, if) Bubble tower, (g) Venturi mixer, h) Static in line mixer, ( ) Tubular flow, (j) Stirred tank, (A,) Centrifugal pump, (/) Two-phase flow in horizontal tubes. 

The classification made by Alves (Al) for two-phase flow in horizontal tubes appears to describe adequately the majority of flow patterns for this case. The following patterns are clearly observable, and are shown sketched in Fig. 3. 

For example, typical for the empirical flow charts is the flow-regime map of Charpentier and Favier [14], whose use has been recommended by Tosun [15]. It uses the coordinates proposed by Baker [16] for two-phase flow in horizontal tubes. The abscissa is the superficial mass flow-rate of the gas the ordinate is the ratio of the liquid-to the gas-mass flow-rates. The properties of the gas and the liquid are taken into account by the parameters ... 

Bergles, A. E., and R. R. Simonds Combined Forced and Free Convection for Laminar Flow in Horizontal Tubes with Uniform Heat Flux, Int. J. Heat Mass Transfer, vol. 14, p. 1989, 1971. 

Flow in horizontal tubes as well as inclined tubes can be studied at Pr-numbers from 0.8 to 22, Re-numbers up to 1.5x10s and Gr-number up to 8x10 . 

For bubble flow and plug flow in horizontal tubes, the following correlation is proposed by Scott and Hayduk (S12) and Shah and Sharma (S16) ... 

D. R. Oliver and V. G. Jenson, Heat Transfer to Pseudoplastic Fluids in Laminar Flow in Horizontal Tubes, Chem. Eng. Sci. (19) 115,1964. 

The most widely quoted flow pattern maps for predicting the transition between two-phase flow regimes for adiabatic flow in horizontal tubes are those of Baker (1954) and Taitel and Dukler (1976). The Baker (1954) map for horizontal two-phase flow in tubes is presented with coordinates ritg/X and In order to use the map first the mass velocities of the liquid (m ) and vapor (wig) must be determined. Then the parameters lambda X and j/ are calculated using the following equations ... 

Then assuming laminar case (because turbulent flow in horizontal tubes is relatively rare), we obtain... 

The density and geometry of fabric pores, which can be varied according to woven fabric structure, has a significant influence on the liquid flow pattern both in the interstices and downstream characterize porous media by analyzing the kinetics of capillary penetration. Ichikawa and Satoda [49] have described the interface dynamics of capillary flow in horizontal tube as ... 

Serizawa et al. (2002) studied experimentally, through visualization, the two-phase flow patterns in air-water two-phase flows in round tubes. The test section for air-water experiments consisted of a transparent silica or quartz capillary tube with circular cross-section positioned horizontally. The two-phase flow was realized through a mixer with different designs, as shown in Figs. 5.4 and 5.5. The air was injected into the mixer co-axially while water was introduced peripherally. 

Kariyasaki A, Fukano T, Ousaka A, Kagawa M (1991) Characteristics of time-varying void fraction in isothermal air-water co-current flow in horizontal capillary tube Trans JSME 57(544) 4036-4043... 

Two flow models are used to estimate the mean condensation coefficient in horizontal tubes stratified flow, Figure 12.45a, and annular flow, Figure 12.45. The stratified flow model represents the limiting condition at low condensate and vapour rates, and the annular model the condition at high vapour and low condensate rates. For the stratified flow model, the condensate film coefficient can be estimated from the Nusselt equation, applying a suitable correction for the reduction in the coefficient caused by... 

Chen s method was developed from experimental data on forced convective boiling in vertical tubes. It can be applied, with caution, to forced convective boiling in horizontal tubes, and annular conduits (concentric pipes). Butterworth (1977) suggests that, in the absence of more reliable methods, it may be used to estimate the heat-transfer coefficient for forced convective boiling in cross-flow over tube bundles using a suitable cross-flow correlation to predict the forced-convection coefficient. Shah s method was based on data for flow in horizontal and vertical tubes and annuli. 

Figure 3.15 Generalized flow pattern map boiling in horizontal tubes. (From Dukler and Taitel, 1991b. Copyright 1991 by University of Houston, Houston, TX. Reprinted with permission.)...

S.4.6.2 Critical heat flux in horizontal tubes. Horizontal CHF data are rather meager, so correlations for predicting such cases are less accurate than for vertical flows. Groeneveld et al. (1986) suggested that use be made of a correction factor, K, such that... 

Dukler, A. E., and M. G. Hubbard, 1975, A Model for Gas-Liquid Slug Flow in Horizontal and Near Horizontal Tubes, Ind. Eng Chem. Fundam. 14(4) 337. (3)... 

B, Flow Patterns in Horizontal Tubes 1. Visual Appearance... 

Kosterin (K3) investigated the effect of tube inclination on flow patterns for air-water systems. As tube inclination increases, the flow patterns become more dispersed tube slope is an important variable at the lower liquid or gas rates. At high gas rates, when annular or dispersed flow normally occurs in horizontal tubes, tube inclination has little effect on flow-pattern. 

Pressure pulsations for incremental flow-patterns are of the least amplitude in horizontal tubes, and increase steadily with tube inclination to become a maximum in vertical tubes. Apparently no correlations for pressure-drops which allow specifically for the effect of tube inclination have yet been developed. 

There have been numerous studies of the effects of gas streams on the thicknesses of liquid films flowing in contact with them. Cases studied in the literature refer mainly to gas/film flow in vertical tubes or channels or horizontal pipes. The latter case will not be considered here. The gas/film flows may be countercurrent, cocurrent upwards, or cocurrent downwards. Only the most important studies can be discussed here. 

Killion, J. D., and Garimella, S. (2003) Gravity-Driven Flow of Liquid Films and Droplets in Horizontal Tube Banks, International Journal of Refrigeration, Vol. 26(5), pp. 516-526. 

In horizontal tubes, at low flow velocities, the liquid film that develops is not annular, but stratified. The condensate collects in the lower part of the tube, whilst the upper walls are wetted by the liquid. Stratified flow appears if the dimensionless vapour velocity is... 

The force of gravity causes the liquid in a horizontal, unheated tube or channel, to flow mainly in the lower section and the vapour in the upper part of the tube. The smaller the inertia forces are in comparison to the gravitational forces, the greater the difference between the flow in horizontal and vertical tubes. Thus, at low velocities flow patterns develop in horizontal tubes that are never seen in vertical tubes. Fig. 4.45 shows the characteristic patterns of two-phase flow in a horizontal tube. 

---