This paper presents BubbleID, a sophisticated deep learning architecture designed to comprehensively identify both static and dynamic attributes of bubbles within sequences of boiling images. By amalgamating segmentation powered by Mask R-CNN with SORT-based tracking techniques, the framework is capable of analyzing each bubble's location, dimensions, interface shape, and velocity over its lifetime and capturing dynamic events such as bubble departure. BubbleID is trained and tested on boiling images across diverse heater surfaces and operational settings. This paper also offers a comparative analysis of bubble interface dynamics prior to and post-critical heat flux conditions.
more »
« less
Deep learning predicts boiling heat transfer
Abstract Boiling is arguably Nature’s most effective thermal management mechanism that cools submersed matter through bubble-induced advective transport. Central to the boiling process is the development of bubbles. Connecting boiling physics with bubble dynamics is an important, yet daunting challenge because of the intrinsically complex and high dimensional of bubble dynamics. Here, we introduce a data-driven learning framework that correlates high-quality imaging on dynamic bubbles with associated boiling curves. The framework leverages cutting-edge deep learning models including convolutional neural networks and object detection algorithms to automatically extract both hierarchical and physics-based features. By training on these features, our model learns physical boiling laws that statistically describe the manner in which bubbles nucleate, coalesce, and depart under boiling conditions, enabling in situ boiling curve prediction with a mean error of 6%. Our framework offers an automated, learning-based, alternative to conventional boiling heat transfer metrology.
more »
« less
- Award ID(s):
- 1752147
- PAR ID:
- 10326512
- Date Published:
- Journal Name:
- Scientific Reports
- Volume:
- 11
- Issue:
- 1
- ISSN:
- 2045-2322
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
The boiling efficacy is intrinsically tethered to trade-offs between the desire for bubble nucleation and necessity of vapor removal. The solution to these competing demands requires the separation of bubble activity and liquid delivery, often achieved through surface engineering. In this study, we independently engineer bubble nucleation and departure mechanisms through the design of heterogeneous and segmented nanowires with dual wettability with the aim of pushing the limit of structure-enhanced boiling heat transfer performances. The demonstration of separating liquid and vapor pathways outperforms state-of-the-art hierarchical nanowires, in particular, at low heat flux regimes while maintaining equal performances at high heat fluxes. A deep-learning based computer vision framework realized the autonomous curation and extraction of hidden big data along with digitalized bubbles. The combined efforts of materials design, deep learning techniques, and data-driven approach shed light on the mechanistic relationship between vapor/liquid pathways, bubble statistics, and phase change performance.more » « less
-
Abstract Squeezing bubbles in a tapered microgap has proved to be effective for improving flow stability in flow boiling. A previous study from our research group has successfully demonstrated using tapered microgap for transforming pool boiling into a self-sustained flow boiling-like system for cooling CPU through thermosiphon. To overcome the imaging challenges with nucleating vapor bubbles, the present work investigates the squeezing behaviour of air-injected bubbles between a tapered microgap with taper angles of 5°, 10°, and 15°. The air bubbles are injected at a rate of 3 ml/min, 15ml/min, and 30 ml/min in a pool of water. The bubble squeezing is recorded at 2000fps using a Photron high-speed camera. The experimental analysis compares the displacement and velocity of the advancing and receding bubble interfaces. The analysis found that in certain test cases, multiple bubbles coalesced while exiting the tapered microgap. In all the test cases, the receding interface of the bubble slingshots after detaching pushes the bubble out of the tapered microgap. The result from the current study provides an insight into the bubble flow and squeezing behavior that can be used for optimizing taper microgap geometries to enhance critical heat flux and heat transfer coefficient of two-phase, and air-injected single-phase heat transfer systems.more » « less
-
Nucleation and bubble dynamics on a heater surface contribute to high heat transfer rate in pool boiling. Introducing two-phase flow in narrow channels further improves heat transfer. Use of expanding taper microgap geometry further enhances heat transfer, and proper balancing of taper angles and flow lengths leads to self-sustained flow boiling in tapered microgap geometries. This paper focuses on understanding the underlying enhancement mechanism by studying the bubble behavior as they expand and accelerate in the direction of increased taper. The present study conducts a 2D simulation analysis of bubble growth in tapered microgaps with numerical simulations to identify the effect of the fluid properties and tapered angle in the bubble and fluid dynamics behavior. Ansys-Fluent is customized with user-defined-functions (UDFs) accounting for the interfacial heat and mass transport, including a sharp interface and direct calculation of mass transfer with temperature gradients. The study was conducted using air injection and boiling simulation from the conception to the departure of a bubble. The tapered angles were 5°, 10°, and 15°, with flowrates between 3 ml/min to 30 ml/min, 1 mm air inlet, and at 1 mm distance from the convergent end. The departure time of 10 subsequent bubbles was recorded to check the configuration with the quickest bubble removal. A critical flowrate and surface tension region was established for the escape direction of the bubble. In addition, the numerical simulation considered the tapered microgap with a nucleating bubble at atmospheric conditions with a wall superheats of 5 K. The results show that the bubble growing over the heated surface creates fluid circulations and interfacial conditions that suppress the thermal boundary layer leading to an increased local heat transfer coefficient within a range of 1 mm from the interface.more » « less
-
Abstract We reveal and justify, both theoretically and experimentally, the existence of a unifying criterion of the boiling crisis. This criterion emerges from an instability in the near-wall interactions of bubbles, which can be described as a percolation process driven by three fundamental boiling parameters: nucleation site density, average bubble footprint radius and product of average bubble growth time and detachment frequency. Our analysis suggests that the boiling crisis occurs on a well-defined critical surface in the multidimensional space of these parameters. Our experiments confirm the existence of this unifying criterion for a wide variety of boiling surface geometries and textures, two boiling regimes (pool and flow boiling) and two fluids (water and liquid nitrogen). This criterion constitutes a simple mechanistic rule to predict the boiling crisis, also providing a guiding principle for designing boiling surfaces that would maximize the nucleate boiling performance.more » « less
An official website of the United States government

