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This paper investigates the force features of inclined pipes under the action of waves and flows through both test and numerical simulation. Firstly, the wave and flow loads on inclined pipes were examined through tests in circulating water flumes. Next, the unsteady Reynolds-averaged Navier-Stokes (RANS) equations were adopted to numerically simulate the test conditions. Multiple factors were taken into consideration: immersion depth, inclination, flow rate, wave height, and cycle. The results show that, the wave and flow loads on the pipes both increase with wave height and flow rate. When the inclination β = 0°, the flow force is most rapid, conversely, it is most slow when the inclination β = 30°. Furthermore, when the pipe was immersed by 75%, the change of inclination directly affected the ratio of vertical force to horizontal force. For the pipes with different inclinations, the wave load increases basically at the same rate with the rising wave height. With the widening of the inclination, the wave and flow loads on the pipes become less sensitive to immersion depth, and the maximum loads remain near the free water surface. [ABSTRACT FROM AUTHOR]

In this paper, the entropy generation analysis in dropwise condensation in an inclined pipe is carried out. As the vapor passes through the inclined pipe, the flow of the droplets occurs due to the interfacial shear and gravity. Three distinct zones considered in the numerical study include the saturated vapor flowing in the axial direction, saturated liquid traveling through the bottom of the pipe, and the condensate droplet flowing on the inner side of the pipe wall. With the aim of achieving optimal geometrical conditions of the pipe and flow, the entropy generation was calculated for various cases. The results show that the minimum entropy generation of 0.0754 W·K−1 occurs in a configuration with a diameter of 9.5 mm and an inclination angle of 1°. Finally, the Bejan number, irreversibility distribution ratio, and variation according to the flow conditions were presented. [ABSTRACT FROM AUTHOR]

The inclined pipe is widely used as a downward particle-conveying structure. Bubbles accompanying with the descending particles always induce complex flow pattern and pipe vibration, which would shorten the service life of equipment. In this paper, the gas-solid interaction and fluid-vibration coupling were experimentally studied by analyzing dynamic pressure and displacement of an inclined pipe. The results showed that, with increased mass flow rate, there was a progressive gas-solid flow behavior in the inclined pipe due to the water-pouring phenomenon. With the generation and upward channeling flow of bubbles, the downward particle flow showed an unstable motion, causing pressure fluctuations and severe vibration of the pipe system. Downward behavior of particles in the inclined pipe were eventually divided into three flow patterns: (1) creeping stratified flow, (2) gas channeling flow, and (3) dense phase fluidization flow. This work can provide theoretical basis for the design and operation of inclined pipe. [Display omitted] • A water-pouring phenomenon affects the gas-solid flow behavior in the inclined pipe. • Particle downward flow in the inclined pipe is divided into three flow patterns. • Valve bubbles upwardly flow into the pipe introducing particles' regular flow. • Channeling bubbles cause pressure fluctuations and severe vibration of the pipe. • A dense phase fluidization flow occur as the particle flow rate close to the maximum. [ABSTRACT FROM AUTHOR]

In this experimental work the effect of inclination on the pressure gradient in two phase oil–water flow is investigated. The experiments were performed in a 6 m long, 20 mm inner diameter and inclinable acrylic pipe using oil (3 mPa s viscosity and 830 kg/m 3 density) and water (1 mPa s viscosity and 990 kg/m 3 density) as test fluids. Pressure gradients between inlet and outlet of flow in pipe were measured for inclination angles of 0°, ±5°, ±15°, ±30° and ±45° with respect to the horizontal plane. The experimental results were compared with Homogeneous and Two-Fluid models. It was observed that in high mixture velocities, where dispersed flow prevails, there is a peak pressure gradient which is related to phase inversion. It was also found that, phase inversion appears at higher inlet water cut values in inclinations of −30° and −45° compared with other inclinations. However the two-fluid model and homogeneous model both over-predicted the pressure drop, but two-fluid model predicted the pressure drop with less average deviation. Several correlations for effective mixture viscosity in a homogeneous model were considered and the results were compared with experimental results. Acceptable agreement was seen between the computed and measured data. The experimental two-phase friction factors were compared with the friction factors for single phase flow of oil and water, at the same velocities as the two phase mixture and it was found that the experimental friction factors were less than the predicted friction factors of single phase flow. [ABSTRACT FROM AUTHOR]

Abstract: The turbulent heat transfer in gas-solid flows through an inclined pipe under various inclination angles is studied with constant wall heat flux. The hydrodynamic k − τ and kθ − τθ thermal two phase model is used in a lagrangian/Eulerian four way approach. The numerical results agreed reasonably with available experimental data in vertical and horizontal pipe flows. The effects of inclination angles on the flow patterns are reported. The pressure drop and Nusselt number are enhanced significantly as the inclination increases up to a certain angle. The mass loading ratio has influence on the optimal inclination angle. With increasing loading ratio, the optimal inclination angle of maximum pressure drop shifts to the lower amount. [Copyright &y& Elsevier]

Abstract: The stratified oil–water flow pattern is common in the petroleum industry, especially in offshore directional wells and pipelines. Previous studies have shown that the phenomenon of flow pattern transition in stratified flow can be related to the interfacial wave structure (problem of hydrodynamic instability). The study of the wavy stratified flow pattern requires the characterization of the interfacial wave properties, i.e., average shape, celerity and geometric properties (amplitude and wavelength) as a function of holdup, inclination angle and phases’ relative velocity. However, the data available in the literature on wavy stratified flow is scanty, especially in inclined pipes and when oil is viscous. This paper presents new geometric and kinematic interfacial wave properties as a function of a proposed two-phase Froude number in the wavy-stratified liquid–liquid flow. The experimental work was conducted in a glass test line of 12m and 0.026m i.d., oil (density and viscosity of 828kg/m3 and 0.3Pas at 20°C, respectively) and water as the working fluids at several inclinations from horizontal (−20°, −10°, 0°, 10°, 20°). The results suggest a physical relation between wave shape and the hydrodynamic stability of the stratified liquid–liquid flow pattern. [Copyright &y& Elsevier]

• Studied the behaviour of elongated bubbles in slightly upwardly inclined pipes. • Bubble characteristics; shape, length, fraction and velocity are presented. • Information on the bubble velocity behaviour along the pipe is discussed. • Experimental results comparison with some recently developed drift velocity models. Two phase flow is of great interest in chemical and petroleum industries, and multiphase pipe flow models with closure relationships require experimental data for their development and validation. However, only little experimental information is available for slightly upward inclined pipes. Experimental investigations of single elongated bubble in marginally upwardly inclined pipes less than 10° have therefore been performed. Observations of the bubble drift velocity along the pipe has been highlighted. The drift velocity data presented here can contribute to improve knowledge of pipe inclination and viscosity dependency in drift velocity correlations. The new data on the bubble characteristics - shape, length, fraction and drift velocity may also provide useful information for the development and validation of numerical models. The measured drift velocity data have therefore been compared with some recently developed bubble velocity correlations. [ABSTRACT FROM AUTHOR]