Eventos Anais de eventos
ENCIT 2020
18th Brazilian Congress of Thermal Sciences and Engineering
Start-up Flow Visualization of Viscoplastic Fluid in Horizontal Pipes Geometries Using Particle Image Velocimetry
Submission Author:
Angel De Jesus Rivera Jimenez , PR , Brazil
Co-Authors:
Angel De Jesus Rivera Jimenez, Vitor Yoshiharu Urazaki, Yamid José García Blanco, Eduardo Matos Germer, Admilson Franco
Presenter: Angel De Jesus Rivera Jimenez
doi://10.26678/ABCM.ENCIT2020.CIT20-0714
Abstract
The viscoplastic fluid flows through pipelines can be found in several industrial processes, such as polymer extrusion, food pumping, and drilling of oil wells. The gel-like state of these fluids inside the pipelines after flow interruptions, represents in some situations a relevant challenge, such as the case of transportation of crude in the oil industry, due to this phenomenon increases the minimum pressure necessary to start-up the flow. However, there are not enough experimental studies focused on the relationship between the minimum pressure drop and the breaking mechanisms in the transient start-up flow. This paper presents an experimental study of transient start-up flow of viscoplastic fluids in two different horizontal pipe configurations: a straight section and an abrupt contraction arrangement (1.85 contraction ratio). An ultrasound gel solution with 30 and 20 wt% composed by Carbopol R 940 are used as a viscoplastic fluid, characterized by the Herschel-Bulkley model. Particle Image Velocimetry (PIV) is used as a visualization technique to obtain detailed measurements of mean velocity and deformation maps in the transient start-up flow. A previous stage for validation of the methodology used with the PIV technique was performed for pure glycerine in a straight tube at laminar flow conditions, and the data were compared with the analytical solution for velocity in transient flow regime for a Newtonian fluid. For the viscoplastic flow through both configurations it was possible to observe three different flow regimes: solid (plug-like), solid-fluid, and fluid. In both geometries and as the forcing of the flow gradually increases, the yielding appears through a transition. The deformation states are greater in abrupt contraction and are coupled with the wall slip phenomenon. The wall shear stress increases with external forcing, that is, with the Reynolds number. The slip velocity increases as a function of the wall shear stress and is higher for the straight section. The results show that the elastic effect plays an important role in the initial phase of destructuring of solid regime, and that the variation of Reynolds number has an influence on the elastic behavior of the material.
Keywords
Viscoplastic flow, Start-up Flow, Yielding process, PIV, Wall slip
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