Annular two-phase flow in vertical smooth and corrugated pipes

Abstract

Two-phase flow in ribbed or corrugated pipes is of interest in many industrial applications. Experiments are performed to assess the flow regime characteristics in upward annular flow through vertical smooth and corrugated pipes. From high speed recordings, the flow regime and temporal film characteristics are obtained. A novel implementation of a planar laser-induced fluorescence (PLIF) method is used to measure the film thickness, preventing strong reflections from deteriorating the measurements. Liquid accumulation between the ribs of the corrugated pipe is also measured using a PLIF technique. Furthermore, droplet sizing is performed combining shadowgraphic and interferometric techniques to capture a large droplet size range. The measurements show that the presence of pronounced corrugations at the pipe wall causes a strong increase in entrainment of liquid into the gas flow. The entrainment is correlated to the filling of the corrugations with liquid; it is significantly reduced (from 90% entrainment to 50%) when the corrugations are entirely filled with liquid. The amount of liquid filling of the corrugations is related to the superficial liquid film flow velocity. The liquid filling fraction (α) scales with the Weber and liquid Reynolds number, and the obtained scaling also holds when the experiments are repeated with a different liquid (mono-ethylene glycol) and with a larger corrugation geometry. Droplets occurring in corrugated pipe flow are 30-50% larger compared to the smooth pipe, as a consequence of the locally (at the locations of the cavities) increased film thickness.

Pressure Drop dan Pola Aliran Dua Fase (Air-Udara) Melewati Pipa Groove Vertikal

“…Aliran dua fase vertikal pada pipa bergelombang juga sudah diidentifikasikan dibandingkan dengan pipa tanpa alur. Hasil yang diperoleh menunjukkan perilaku yang berbeda pada kondisi pola aliran yang sama [12].…”

Structured planar laser-induced fluorescence (S-PLIF) for the accurate identification of interfaces in multiphase flows

“…A thin laser-sheet (< 500 µm) was generated using a frequency-doubled Litron Nd:YAG laser (emission at 532 nm) and LaVision sheet optics, and was directed to the flow at an angle of ≈ 30°through a Ronchi ruling plate that comprised 5 line-pairs per mm and was attached to the correction box. The laser sheet was inclined, rather than being positioned at right angles to the pipe, also in contrast to the work of van Eckeveld et al [44], in order to limit the occurrence of reflections of the intensity-modulated fluorescence by the gas-liquid interface without a prominent shift in the observed pattern. This scenario would ensue, for example, when the interface slope is ≈ 0°(i.e., when the film is flat or in the troughs of any inetrface fluctuations).…”

“…Another noteworthy difference compared to the arrangement used in Ref. [44] is the employment of a Ronchi plate for generating the modulation of the fluorescence emission, which allows us to obtain film thickness measurements with high spatial resolution in the axial direction of the flow. In contrast, the former tracked the deflections (due to TIR) of the shadows cast by a sparse grid that was placed in front of the laser-sheet, resulting in thin dark lines that were separated by much larger bright-emission intervals.…”

“…Finally, it is noted that although the basic principle of the measurement technique (i.e., the employment of structured illumination) we employ here, as well as in the original publication [43], where this technique was first reported in the literature, is similar to that proposed more recently by van Eckeveld et al [44], its implementation in our work, as well as the scope of our paper differ. In particular, we generate a regular illumination-pattern using a Ronchi ruling plate with a high line-density (see Section 3), which allows us to recover filmthickness measurements with a high spatial resolution (in the axial direction of the flow), and have developed and present an image-processing methodology to systematically track the location of the gas-liquid interface (described in Section 4).…”

C Investigation of Heat Transfer Coefficient Augmentation in Divergent Rectangular Duct for Two Phases Flow (Air-Water)

“…The ribs were positioned in the duct at three various locations to establish three various conditions. It was found that, increasing of the rib height initiated hydro-dynamical instability at lower fluid velocities [Turaihi, et al (2018) and Van Eckeveld, et al (2018)]. Karthikeyan et al (2015), experimentally studied the influence of the rib's height on the heat transfer and fluid characteristics of air flow in a convergent/divergent rectangular channel with an inclination angle of 1° in y-direction.…”