The purpose of this study is to investigate experimentally the effects of reduced surface tension on the liquid film structure in vertical-upward air-liquid annular flows in a 19.2 mm i.d. and 5.4 m long circular tube. The test liquid was water and/or a dilute water solution of Polyoxyethylene-Lauryl-Ether, and the surface tension of these liquids ranged from 72 to 45 dyne/cm. The liquid film structure was observed by use of both the still photographs and the maps of time and spatial characteristics of peripheral-mean liquid film thickness detected with a series of 63 liquid holdup sensors each axially 15 mm apart in a constant current method. The parameters studied were the wave heights of the liquid film, the passing frequencies of the waves, the mean value and the standard deviation of the wave velocities, each determined from the liquid film thickness signals through a computer program of signal processing. From the observations of still photographs and the maps of time and spatial characteristics of peripheral-mean liquid film thickness, it was cleared that the liquid film structure depends strongly on the surface tension, i.e., the reduction of surface tension makes the passing of the large waves decrease remarkably, the wave height of the large waves lower like small waves, the passing of the small waves more frequent, and the small wave velocity faster.

The purpose of the present experimental study is to investigate the effects of liquid viscosity on the flow patterns of upward air–liquid two-phase flow in a vertical tube of 19.2 mm in inner diameter and about 5.4 m in length. Three different liquids, including water and aqueous glycerol solutions, were employed. Kinematic viscosity of these liquids varied from 1.0×10−6 to 14.7×10−6 m2/s. The flow patterns were observed using a video recorder and still photography. The time-spatial characteristic maps of gas–liquid interfaces which were drawn using the mean liquid holdup signals detected by 70 pairs of holdup sensors arranged with the axial spacing of 15 mm over the length of 1.035 m were also used. In this report, we first defined the flow pattern of each flow. Next, the effects of liquid viscosity on the overall flow pattern and interfacial structures, or the interfacial waves, were discussed. Finally, based on those results we proposed flow pattern maps for each liquid viscosity. It is found that the flow pattern transitions strongly depend on the liquid viscosity.

The purpose of the present study is to investigate the effects of liquid viscosity on the mean liquid film thicknesses, wave heights, and gas–liquid interfacial shear stresses in the vertical-upward co-current annular flow in a 26.0mm inner diameter tube. Water and glycerol solutions were used as working fluids to change the kinematic viscosity of liquid from 0.85×10−6 to 8.6×10−6m2/s. The mean liquid film thicknesses and wave heights were determined using the signals of time-varying cross-sectionally averaged holdup which were detected by a constant current method at a distance of about 3.5m from an air–liquid mixer. The pressure gradients were also measured by a U-tube manometer. As a result we proposed correlations for the mean liquid film thicknesses and the interfacial friction factors. In addition a method to estimate the pressure drops is proposed and verified that the calculated values are in good agreement with the measured values.

The effects of liquid viscosity on the rising velocity of a large gas bubble in a stagnant liquid, and on the flow parameters of slug flow were experimentally investigated using a 19.2mm diameter vertical tube with air and liquid as working fluids. The liquids used in the present experiment were water and glycerol solutions, and the kinematic viscosity of these liquids ranged from 0.83×10-6 to 15.5×10-6m2/s. The important parameters in slug flow such as the rising velocity of large gas bubbles, liquid slug length, liquid film thickness around large gas bubbles etc., were measured. As a result, it is clarified that the rising velocity of a large gas bubble in a stagnant liquid decreases only slightly with increasing liquid viscosity. On the other hand the rising velocity in flowing liquid, i.e., in slug flow increases with increasing liquid viscosity. These results are discussed in relation to the liquid film thickness around large gas bubbles. Furthermore, the mean values of gas and liquid slug lengths and the ratio of their standard deviations to mean values of their length are examined by paying attention on the effect of liquid viscosity.

Experimental data are presented on the liquid lump velocities in vertical upward gas-liquid two-phase flow. The liquids used in this experiment are water and glycerol solutions, and the kinematic viscosity of these liquids ranges from 1.0×10-6 to 15.5×10-6 m2/s. Flow regimes concerned herein cover plug flow, huge wave flow and annular flow. Velocities of liquid lumps, such as liquid slugs, huge waves, disturbance waves or ephemeral large waves, are determined using two sets of signals of time-varying cross-sectional mean liquid holdups which are electrically detected at two axially separated locations in the test tube. It is first described, from the observations of liquid holdup signals, that the liquid viscosity affects the formation of liquid lumps or the appearance frequency of the same kind of liquid lump under the same gas and liquid flow rates. Next, the mean values of liquid lump velocity and their standard deviations are discussed with attention paid to the effect of liquid viscosity.

Experimental data are presented on the phase distribution of air-water two-phase mixtures which flow vertically upwards in annular passages. Three annuli with different radius ratios, R1/R2 =5/13, 8/13 and 10/13, are used in the present experiments. Flow patterns observed in the annuli are first demonstrated. Next, two items characterizing void fraction distributions, i.e. void fraction near the wall and the position of the radius of maximum void fraction are discussed with attention paid to the effect of the passage width. Flow regimes concerned here-in cover bubbly, slug, froth and froth-annular or huge wave flow. Finally, an attempt is made to obtain a correlation for evaluating cross-sectional average void fraction. The proposed correlation is in good agreement with experimental values for both the annuli and a round tube.

A computer-aided data reduction method was newly developed for determining principal flow parameters on disturbance wave and liquid film in gas-liquid two-phase annular flow. Hold-up data on magnetic tape were processed by computer to discriminate disturbance wave from base-film based on the proposed criteria and to evaluate flow parameters with sub-stantial reduction of time and labor. Four test tubes of 8, 12, 18 and 26 mm bore were employed, and time-varying liquid hold-up was recorded by means of the constant-current method. The flow parameters computed were velocity, frequency, separation distance and height of disturbance waves, base-film thickness, and superficial film thickness. It was found that most of the flow parameters present a maximum or minimum with the tube of 12 mm bore.

蒸発を伴う蒸気-水ニ相流動系におけるドライパッチの生成消滅に対して流動障害物の有無がどのような影響を与えるかについて調査した。その結果、ドライパッチの生成消滅は障害物の有無にかかわらず主として発達したスラグ流および環状流において観察されたが、障害物がある場合にはドライパッチは障害物近傍に発生しやすく、発達したスラグ流ではその上流部に、また環状流ではその下流部に出現する性質のあることが見い出された。