The thermosyphon is a type of heat exchanger that has been widely used in many applications. The use of thermosyphons has been intensified in recent years, mainly in the manufacture of solar collectors and various industrial activities. A thermosyphon is a vertical sealed tube filled with a working fluid, consisting of, from bottom to top, by an evaporator, an adiabatic section, and a condenser. The study of geyser-boiling phenomena, which occurs inside the thermosyphon is of extreme importance, therefore the experimental analysis of the parameters related to the two-phase flow (liquid-steam), such as void fraction, bubble frequency, bubble velocity, and bubble length are necessary, since these parameters have a significant influence on heat transfer. In this work, a pair of wire mesh sensors was used, a relative innovative technology to obtain experimental values of the reported quantities for measuring these parameters of slug flow in thermosyphons. An experimental setup is assembled and the sensors are coupled to the thermosyphon enabling the development of the experimental procedure. Here is presented an experimental study of a glass thermosyphon instrumented with two Wire-Mesh Sensors, in which the aforementioned slug flow hydrodynamic parameters inherent to the geyser type boiling process are measured. It was measured successfully, as a function of the heat load (110, 120, 130, 140, and 150W), the void fraction (instantly and average), liquid film thickness, translation velocity of the elongated bubbles, lengths of the bubbles, and the liquid slug (displaced by the bubble rise up). It was observed that the higher the heat load, the lower is the bubble translation velocity. For all heat loads, based on the measured length of liquid slug (consequent displacement of liquid volume), caused by bubbles rise from evaporator to condenser, it could be affirmed to some extent that both boiling regime (pool and film) exist in the evaporator. The measured average void fraction (80%) and liquid film thickness (around 2.5mm) during the elongated bubble passages were approximately constant and independent of the heat load.
Multiphase flows are recurrent phenomena both in natural environments-such as volcanic eruptions and blood flow through veins-and industrial environments-such as the nuclear and petroleum industries. Knowledge about the hydrodynamics of the flow as well as its evolution across the pipeline is essential to correctly design pipelines, equipments (such as pumps and slug catchers) and to formulate strategies to optimize the crude oil exploitation from reservoirs. A frequently reported flow pattern in oil pipelines is slug flow, reason why the present study focuses in its investigation. In order to analyze the flow, a novel methodology is proposed and applied to data retrieved in Multiphase Flow Center (NUEM) experimental facilities. The experimental loop has a length of 35.6 m and 26 mm internal diameter and was operated under 18 different slug flow conditionsvarying gas superficial velocity from 0.3 to 2.5 m/s and liquid superficial velocity from 0.3 to 3.0 m/s-across 5 different measuring stations composed by a pair of two-wire resistive sensors distributed along the pipe. Data was analyzed using Eulerian reference frame (ERF), which provides distributions for each hydrodynamic parameter in each measuring station for every experimental point, and Lagrangian reference frame (LaRF), which follows unit cells across the pipeline in order to evaluate the change in hydrodynamic parameters of single structures. Correlations were proposed based on retrieved results for hydrodynamic parameters average values and standard deviation. Moreover, a comparison against previous works was made in order to test the presented correlations as well as to propose corrections to the existing ones. Furthermore, details of the flow were investigated using the developed methodology, which was able to provide additional and insightful information about the flow behavior-such as the intrinsically unsteady nature of slug flow, as slug lengths were found to oscillate at all times, even though average values did not report significant changes, which would indicate developed flow conditions. Moreover, it was shown that gas expansion is a driver phenomenon in heavily aerated points, but becomes lees pronounced in low aeration flows-such as plug flows.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.