Two-phase Flow In Horizontal Tube Research Articles

Effect of Tube Size on Flow Pattern of Air-Water Two-Phase Flow in Horizontal Tubes

Aiming at the diameter range of boiler water wall tubes in practical engineering application, the air-water two phase flow pattern in horizontal tube was experimentally investigated in tubes with different inner diameters of 20mm and 8 mm under atmosphere condition. The stratified flow, wave flow, plug flow, slug flow, annular flow, bubbly flow and mist flow were observed in the tubes. Most of the experimental points agree well with the Baker flow pattern map when they appear in the map. With the experimental results, the range lines between the flow patterns were suggested for the tube of 20mm in inner diameter as well as 8mm. As the water superficial velocity increases, the annular flow transforms into mist flow at a decreasing air superficial velocity. The two phase flow patterns transition line is similar in tendency for different tubes. The slug flow transforms into annular flow at an increasing air superficial velocity as tube diameter decreases. The stratified flow transforms into slug flow at an increasing water superficial velocity as tube diameter decreases. The transition line between plug flow and slug flow is independent of tube diameter.

Mechanistic multidimensional analysis of horizontal two-phase flows

The purpose of this paper is to discuss the results of analysis of two-phase flow in horizontal tubes. Two flow situations have been considered: gas/liquid flow in a long straight pipe, and similar flow conditions in a pipe with 90° elbow. The theoretical approach utilizes a multifield modeling concept. A complete three-dimensional two-phase flow model has been implemented in a state-of-the-art computational multiphase fluid dynamics (CMFD) computer code, NPHASE. The overall model has been tested parametrically. Also, the results of NPHASE simulations have been compared against experimental data for a pipe with 90° elbow.

ICONE15-10684 INVESTIGATION ON FLOW PATTERN OF GAS-WATER FLOW IN HORIZONTAL TUBES IN ROLLING STATE

Experiments were carried out to investigate the flow patterns of gas-water two-phase flow in horizontal tubes in rolling state. In the experiments, the rolling angle was 10 degrees, and the rolling cycle was 15 seconds. With the help of high digital camera, on the basis of careful observation, a flow pattern map was protracted, and it was found that there might be two flow patterns in one rolling cycle. It was also found that the inertial force, which was induced by rolling tubes, to the air and water in the pipe, had an important influence on the flow pattern transitions. The results were gained to provide basis for farther study of two-phase flow in rolling state.

Condensation heat transfer studies for stratified, cocurrent two-phase flow in horizontal tubes

Condensation heat transfer inside horizontal tubes is investigated for a stratified, cocurrent two-phase flow of vapor and liquid. The analysis takes into account the effects of interfacial shear, axial pressure gradient, saturation temperature level, driving temperature difference and the development of the stratified angle associated with the accumulated condensate layer at the bottom of the tube. The influence of these parameters is evaluated with respect to the peripheral condensate film heat transfer performance for the practically interesting laminar flow range of operating conditions of water-vapor flow. A theoretical predictive method is developed to obtain the overall heat transfer coefficient along the tube length. Results of the theoretical predictions are found to agree favorably with the reported experimental data which cover a variety of fluids with a relatively wide range of operating conditions. A simple, predictive heat transfer coefficient correlation is proposed from the numerical solution by means of regression analysis.

Ultrasonic system for the detection of transient liquid/gas interfaces using the pulse-echo technique

An ultrasonic method has been chosen to examine liquid/gas interfacial areas in closed systems. Although commercial equipment was used for the transducer and ultrasonic analyzer, commercial transient memory devices were inadequate. Consequently, a real-time data analysis and transient memory (DATM) unit was designed and constructed. A series of flight times for a succession of 1024 signals are calculated and recorded in the transient memory. The system clock operates at 10 MHz and increments a 12-bit binary counter. The counter is capable of measuring return signal times as long as 212 μs (4.096 ms) with a 1-μs resolution. The data are available as analog voltages for display on an oscilloscope or the digital data may be directly transferred to a microcomputer for analysis, display, or archival storage. The DATM device was successfully applied, collecting data for the analysis of rising bubbles in metallurgical systems and two-phase flow in horizontal tubes.

Experimental Study of Counter-Current Two-Phase Flow in Horizontal Tube Connected to Inclined Riser

In order to determine the Counter-Current Flow Limitation (CCFL) in hot legs of PWRS, CCFL characteristics of air-water and saturated steam-water flow were experimentally investigated in a modeled flow path of a horizontal tube connected to an inclined riser. The ranges of dimensions of experimental tubes were as follows: diameter D 0.026–0.076 m, length of horizontal tube H 0.01–0.4 m, length of inclined riser I 0.038–0.6 m and inclination angle of inclined riser θ 40° or 45°. Wallis-type correlation (J g *1/2+mJ i *1/2=C) was applicable to the data during a steady separated flow. An analysis based on envelope theory showed that the constant C should be a function of H/D and I. A function of C with those parameters was empirically determined by using data obtained in this study. The developed function correlated well with the results of Richter et al. (D = 0.203 m, H = 1.26 m, I = 0.5 m and θ = 45°). The constant m in the Wallis-type correlation was almost constant 0.75. The problems were discussed, which should be made clear to apply the correlation obtained in this study to an actual PWR hot leg.

Experimental study of counter-current two-phase flow in horizontal tube connected to inclined riser.

In order to determine the Counter-Current Flow Limitation (CCFL) in hot legs of PWRS, CCFL characteristics of air-water and saturated steam-water flow were experimentally investigated in a modeled flow path of a horizontal tube connected to an inclined riser. The ranges of dimensions of experimental tubes were as follows: diameter D 0.026–0.076 m, length of horizontal tube H 0.01–0.4 m, length of inclined riser I 0.038–0.6 m and inclination angle of inclined riser θ 40° or 45°. Wallis-type correlation (J g *1/2+mJ i *1/2=C) was applicable to the data during a steady separated flow. An analysis based on envelope theory showed that the constant C should be a function of H/D and I. A function of C with those parameters was empirically determined by using data obtained in this study. The developed function correlated well with the results of Richter et al. (D = 0.203 m, H = 1.26 m, I = 0.5 m and θ = 45°). The constant m in the Wallis-type correlation was almost constant 0.75. The problems were discussed, which should be made clear to apply the correlation obtained in this study to an actual PWR hot leg.

Flooded countercurrent two-phase flow in horizontal tubes and channels

A criterion for flooding in the countercurrent flow of two fluids in horizontal tubes and channels is developed. It exhibits a dependence upon the density ratio of the fluids beyond that present in the criterion of Wallis (1969). Experiments were carried out with air and water in a horizontal tube at atmospheric pressure and these, together with others reported in the literature, are shown to be in fair agreement with the prediction of the criterion, though it is emphasised that more experimental work is desirable. Work reported in the literature with miscible fluids with a density ratio close to unity confirms the extra dependence upon the density ratio.