Eventos Anais de eventos
COBEM 2023
27th International Congress of Mechanical Engineering
The influence of pipe diameter on liquid film features in vertical downward annular flow
Submission Author:
Ana Luiza Beltrão Santana , PR
Co-Authors:
Ana Luiza Beltrão Santana, Eduardo Nunes dos Santos, Marco Jose Da Silva, Moisés Marcelino Neto, Rigoberto Morales
Presenter: Ana Luiza Beltrão Santana
doi://10.26678/ABCM.COBEM2023.COB2023-1349
Abstract
The annular two-phase flow is characterized by a gas core with dispersed droplets and a liquid film wetting the pipe wall. The film presents structures on the gas-liquid interface of the flow, classified into disturbance waves and ripples. These waves are affected by the high interfacial shear stress between the phases and the gas-liquid flow rate variation. The disturbance waves are the interfacial structures that play a role in influencing the properties of the flow, such as pressure drop, liquid entrainment, transfer of momentum, mass, and heat. The knowledge of these flow parameters is essential to optimize models and contribute to the progress of the monitoring processes in the industry. From previous works, it is known that the diameter affects the flow parameters. Furthermore, the literature shows many studies on upward vertical annular flows and a lack of research on downward annular flows. Regarding that latter, most works use limited experimental apparatuses concerning the length-to-diameter ratio. In this scenario, an experimental evaluation was conducted to analyze the liquid film parameters in downward vertical air-water annular flow using a rig with two different internal diameters, 26 mm, and 50 mm, and a 14 m long pipe at ambient conditions. Twenty-eight annular flow combinations of superficial air and water velocities were investigated for each diameter, ranging from 0 m/s to 15 m/s and 0.05 m/s to 0.25 m/s, respectively. Time series of cross-sectional average liquid thickness obtained by a non-intrusive dual ring-shaped conductance sensor was used to provide the fluid film characterization. Moreover, high-speed visualization was used to contribute to the phenomenological and morphology behavior of the annular flow. The liquid film time series analysis provided features such as the average film thickness, film roughness, velocity, frequency, amplitude, length, and appearance of the disturbance waves. Individual identification of the disturbances waves was performed to investigate the velocity and frequency regarding the distribution and interaction of the waves. Results comparison of the flow parameters between the flow conditions for the two different diameters analyzed shows variations in the frequency and velocity of the disturbance waves, with the larger diameter (50 mm ID) presenting the small results.
Keywords
Annular flow, pipe diameter, liquid film, Disturbance wave, Conductance Sensor
