Eventos Anais de eventos
COBEM 2023
27th International Congress of Mechanical Engineering
Digital Image Correlation applied to interface tracking during flow boiling in microchannels
Submission Author:
Debora Carneiro Moreira , SP , Brazil
Co-Authors:
Debora Carneiro Moreira, Jorge Nicolau dos Santos, Valter Salles do Nascimento Junior, Gherhardt Ribatski
Presenter: Debora Carneiro Moreira
doi://10.26678/ABCM.COBEM2023.COB2023-2064
Abstract
The use of heat sinks based on flow boiling in microchannels has been widely investigated over the last decades, mainly due to the ability of dissipating high heat loads from restricted spaces with minimum temperature gradients throughout the devices. Despite these desirable characteristics for thermal management technologies, most investigations from the literature still rely on empirical observations and parametric studies, while fundamental aspects regarding the phenomena are yet to be understood. Recently, encouraging flow boiling heat transfer results were obtained with microstructured surfaces containing asymmetric Dual-V microchannels with an open and tapered manifold. The performance was attributed to the successful combination of strategies previously employed to enhance pool and flow boiling heat transfer, promoting bubble crossflow and inducing separate liquid and vapor pathways. High-speed images of the flow patterns during those experiments were associated with the operational conditions and parameters of interest, like pressure drop and heat transfer coefficient. However, it should be noted that these images can also reveal the locations of active nucleation sites, be used to estimate the single-phase length, the bubble departure diameters and frequencies, bubble trajectories, and the occurrence of instabilities and back-flow, for example. The main goal of this work is to process the acquired full-field high speed images in order to track the generated interfaces through the digital image correlation method and assess the displacements and velocities of the interfaces. The interface identification and displacement calculations were implemented using MATLAB scripts, and the evolution of flow patterns related to each condition was observed in full-field images, revealing the activation of nucleation sites at upstream portions of the channels and the establishment of liquid-vapor preferential paths. Finally, the image analysis was applied to image sequences obtained at various experimental conditions, and the observations were compared with heat transfer performances and calculated single-phase lengths, showing good agreement between theoretical and experimental results and supporting that the performance improvement is directly related to the generation of preferential liquid and vapor paths.
Keywords
High-speed image, microchannels, Separate liquid-vapor pathways, phase change, DIC
