Experimental investigation on bubble sliding during subcooled flow boiling in microchannel

Yin, Liaofei; Jia, Li; Xu, Mingchen

doi:10.1016/j.expthermflusci.2015.05.010

Cited by 20 publications

(8 citation statements)

References 38 publications

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“…Yin et al [53] observed that the bubble nucleates at the channel corner then it departs the nucleation site by sliding motion along the channel. The bubble size and sliding velocity did not change significantly in the early stage of sliding while at a later stage, immediately before lifting off, the sliding velocity was larger and the bubble size was smaller.…”

Section: Bubble Dynamics -Effect Of Confinementmentioning

confidence: 99%

Flow Boiling in Micro-Passages: Developments in Fundamental Aspects and Applications

Karayiannis

Mahmoud

2018

International Heat Transfer Conference 16

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Flow boiling in mini to micro passages located at the heat source, and as part of a thermal management system, has been identified as a possible way to remove the increasing high heat fluxes generated by high power electronic devices due to their capability of high heat transfer rates with small surface temperature variations. However, some still unresolved fundamental issues hinder the possible full adoption of this technology. These relate to the prevailing flow patterns, heat transfer rates and pressure drop in such geometries, and their dependence on key parameters. The possible major applications of flow boiling in microchannels are first mentioned in this paper, highlighting the requirements and the challenges of the thermal management of each application. The paper then presents new experimental research by the present authors as well as research reported in the literature on flow boiling in single tubes and rectangular multi microchannels to help elucidate the following fundamental issues: the definition of a microchannel, prevailing flow patterns, heat transfer mechanisms, flow instability and reversal and their effect on heat transfer rates, effect of channel material and surface characteristics (including latest research in coatings), effect of different fluid properties, and its relation to channel material, effect of channel length and aspect ratio. An appreciation of the above can help explain the interpretation of the prevailing fluid flow and heat transfer phenomena and the data scatter and discrepancies observed in past studies. In addition, models and correlations predicting flow patterns and heat transfer rates are presented.

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Section: Bubble Dynamics -Effect Of Confinementmentioning

confidence: 99%

Flow Boiling in Micro-Passages: Developments in Fundamental Aspects and Applications

Karayiannis

Mahmoud

2018

International Heat Transfer Conference 16

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“…where the a if term represents IAC. According to Ishii and Zuber, 40 the drag coefficient C D in equation (10) has been formulated for several distinct Reynolds number regions for individual bubbles. For the lift force, it can be calculated based on the slip velocity and the curl of the liquid phase velocity, and it can be seen as follows…”

Section: • Turbulence Modelmentioning

confidence: 99%

“…[1][2][3][4][5][6] Subsequently, many empirical correlations have been formulated, and the resultant data have been used to advance a development of proposed numerical methods. [7][8][9][10][11][12] Based on the physical and mechanistic views, the sizes and frequency of bubbles generated at the heated rod surface can be used to explain how quickly the latent heat is transferred from the heated surface into the bulk liquid. Hence, these bubble parameters are usually involved in determining the wall heat flux partitions, including convective, conductive (quenching) and evaporative heat fluxes.…”

Section: Introductionmentioning

confidence: 99%

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CFD investigation of sub-cooled boiling flow using a mechanistic wall heat partitioning approach with Wet-Steam properties

Promtong

Cheung

Yeoh

et al. 2018

The Journal of Computational Multiphase Flows

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In this paper, the mechanistic wall heat partitioning approach was used to capture the complex heat and mass transfer in sub-cooled boiling flows. In order to accommodate the changes of local variables to be relevant to the physical properties of sub-cooled fluids, the Wet-Steam (IAPWS-IF97) is used as the working fluid. Currently, the approach is evaluated based on the bubble sliding along the wall before lifting-off, which is usually found in the flow boiling situations. In the simulation, the closure mechanistic models, including the fractal analysis, the force balance and the mechanistic frequency, were coupled with the Eulerian-Eulerian two-fluid framework, while the Shear Stress Transport model was used as a turbulent modelling closure. The Multiple Size Group model was introduced to handle the bubble interactions and predict the bubble size distribution. Moreover, the effect of adopting the sub-cooled liquid properties into the modelling was investigated and compared with the experiments over a wide range of flow conditions. Specifically, the predicted void fraction and the sub-cooling temperature near the heated wall were precisely compared with the cases of using the constant-property liquid. Overall, the satisfactory agreements were found between the experiments and the predictions of the liquid temperature, void fraction, interfacial area concentration, Sauter mean diameter and bubble and liquid velocities with the exception of the case of high heat and mass fluxes. To enhance the current prediction accuracy for a situation of having a high superheating temperature, more bubble interactions on the boiling wall, such as merging of the bubbles while sliding, need to be considered. Furthermore, to assess the model capability, this mechanistic approach will be introduced to elucidate the sub-cooled boiling flow in situations of using different fluids in the near future.

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“…In the experiment of subcooled flow boiling of water by Prodanovic et al (Prodanovic et al, 2002), bubble slid for the length of several bubble diameters and migrated toward the bulk fluid. And it was found that bubble sliding is the only way for bubble departure from the nucleation site in microchannel in the study carried out by Yin et al (Yin et al, 2015). Okawa et al (Okawa et al, 2005a,b) investigated the bubble rise after the departure from a nucleation site.…”

Section: Introductionmentioning

confidence: 99%

Visualized Experiment of Bubble Behaviors in a Vertical Narrow Rectangular Channel Under Natural Circulation Condition

et al. 2018

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The characteristics of bubble behavior have been in particular interest for decades due to its significant contribution to understanding the mechanism of heat transfer. In the present work, visualized experiment is conducted to study the bubble characteristics in subcooled flow boiling of a narrow rectangular channel under natural circulation. The experiments were performed at pressures of 0.2 MPa, with inlet subcooling ranging from 20 to 60 K and heat flux ranging from 100 to 300 kW/m 2 . A high-speed digital camera is used to capture the pictures of bubble behaviors. A sequence of image processing algorithms is used deal with the original bubble images to get relevant bubble parameters. We observe the whole process of a single sliding bubble lifetime and found most of bubbles slide along the heating surface after detaching the nucleation sites. Five typical sliding bubble growth paths are observed in the present experimental conditions. According to the analysis of the experimental data, it can be found that the liquid subcooling and wall superheat are the main factors that affect the bubble size during sliding in narrow rectangular channel under natural circulation condition. Due to the difference of driving force, the sliding velocity of bubble in forced circulation is always larger than that in natural circulation. At the same time, the bubble velocity changes significantly at different heat flux and shooting location.

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Experimental investigation on bubble sliding during subcooled flow boiling in microchannel

Cited by 20 publications

References 38 publications

Flow Boiling in Micro-Passages: Developments in Fundamental Aspects and Applications

Flow Boiling in Micro-Passages: Developments in Fundamental Aspects and Applications

CFD investigation of sub-cooled boiling flow using a mechanistic wall heat partitioning approach with Wet-Steam properties

Visualized Experiment of Bubble Behaviors in a Vertical Narrow Rectangular Channel Under Natural Circulation Condition

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