Eventos Anais de eventos
ENCIT 2022
19th Brazilian Congress of Thermal Sciences and Engineering
High-speed imaging of flow boiling in asymmetric Dual-V microchannels with tapered manifold
Submission Author:
Debora Carneiro Moreira , SP , Brazil
Co-Authors:
Debora Carneiro Moreira, Jorge Nicolau dos Santos, Valter Salles do Nascimento Junior, Satish Kandlikar, Gherhardt Ribatski
Presenter: Debora Carneiro Moreira
doi://10.26678/ABCM.ENCIT2022.CIT22-0546
Abstract
Flow boiling in microchannels is a promising thermal management solution for high heat flux dissipation from restricted spaces. High heat transfer capability at relatively low temperature gradients provided by the exchange of latent heat together with the low volume of fluid required in microchannel-based systems are some of the most desirable characteristics in such applications. However, to date the foreseen performance of flow boiling heat transfer in microchannel-based heat sinks is yet to be achieved, mainly due to significant instabilities that resulted in prohibitive pressure drop, early critical heat flux, and lower than expected heat transfer coefficient. In general, the reported instabilities are closely related to the confined growth of bubbles, fluid maldistribution and interaction between channels, and some techniques were proposed to improve the overall performance of these heat sinks. Recently, encouraging results were obtained during flow boiling of water over microstructured surfaces containing asymmetric Dual-V microchannels with an open and tapered manifold. The performance was attributed to the successful combination of previously employed strategies to enhance pool and flow boiling heat transfer, promoting bubble cross-flow and inducing separate liquid and vapor pathways. The main goal of this work is to assess bubble movement through high-speed images, identifying possible preferential directions and quantifying their velocities. The high-speed images were obtained during flow boiling experiments conducted with deionized water at four distinct flow rates varying from 60 – 340 ml/min for a heat flux dissipation that reached 580 W/cm2. An acquisition rate of 18000 fps at a resolution of 128 x 256 was selected for images of single bubbles. The movement of bubbles was tracked through interface and pattern identification algorithms using Matlab, revealing the bubble cross-flow caused by the microstructured surface. Further investigation will be conducted combining imaging analysis with heat transfer performances so it can be verified if the performance improvement can be attributed to the movement of bubbles.
Keywords
Cross Correlation, Low GWP Refrigerants, Heat transfer enhancement
