Review on Bubble Dynamics in Microchannel Heat Sink

2019 ◽  
Author(s):  
Sambhaji T. Kadam ◽  
Ibrahim Hassan ◽  
Ritunesh Kumar ◽  
Aziz Rahman
Keyword(s):  
Bubble Growth ◽  
Bubble Dynamics ◽  
Growth Models ◽  
Flow Boiling ◽  
Nucleation Site ◽  
Bubble Nucleation ◽  
Operating Conditions ◽  
Geometrical Parameters ◽  
Detailed Knowledge ◽  
Diffusion Controlled

Abstract Inception of the boiling, in pool or flow boiling, is the formation of the vapour bubble at active nucleation site. The bubble dynamics plays an important role in the boiling process. It is critical as it unfolds many facets especially when channel size is reduced to submicron. The detailed knowledge of the bubble dynamics is helpful in establishing the thermal and hydraulic flow behaviour in microchannel. In this paper, the bubble dynamics which include bubble nucleation at nucleation site, its growth, departure and motion along the flow in a microchannel are discussed in details. Different models are developed for the critical cavity radius are compiled and observed that they show large variation when compare. The bubble growth models are compiled and concluded that a development of more generalized bubble growth model is necessary to account for the inertia controlled and thermal diffusion controlled regions. The bubble at the nucleation site in a microchannel grows under the influence of various forces such as surface tension, inertia, shear, gravitational and evaporation momentum. Parametric variations of these forces are critically studied and reckoned that the slope of these forces seems to be reduced beyond 500 μm. Eventually, possible impact of the various factors such as operating conditions, geometrical parameters, and thermophysical properties of fluid on bubble dynamics in microchannel has been reported.

Bubble Growth at Nucleation Cavity in Microchannels

2013 ◽  
Author(s):  
Sambhaji T. Kadam ◽  
Ritunesh Kumar ◽  
Kuldeep Baghel
Keyword(s):  
Vapor Phase ◽  
Waiting Time ◽  
Bubble Growth ◽  
Bubble Dynamics ◽  
Flow Boiling ◽  
Nucleation Site ◽  
Bubble Nucleation ◽  
Two Phase ◽  
Proposed Model ◽  
Gravity Effects

Bubble dynamics i.e. bubble nucleation, growth and departure plays an important role in heat transfer and pressure drop characteristics during two phase flow of microchannels. A simplified mathematical model has been developed to predict the bubble growth rate in microchannels at nucleation cavity after its inception. It is assumed that heat supplied at nucleation site is divided between liquid phase and vapor phase as per instantaneous void fraction value. The energy consumed by vapor phase is utilized in overcoming evaporation, surface tension, inertia, shear and gravity effects. Proposed model shows good agreement (∼14 % error) with available experimental work. In addition, the physical phenomena of the bubble waiting time for flow boiling is also addressed utilizing proposed model. The waiting time predicted by the model is close to that obtained from experimental data.

Force Analysis of Bubble Dynamics in Flow Boiling Silicon Nanowire Microchannels

2016 ◽  
Author(s):  
Tamanna Alam ◽  
Wenming Li ◽  
Fanghao Yang ◽  
Ahmed Shehab Khan ◽  
Yan Tong ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Surface Tension ◽  
Bubble Growth ◽  
Bubble Dynamics ◽  
Flow Boiling ◽  
Silicon Nanowire ◽  
Bubble Nucleation ◽  
Force Analysis ◽  
Vapor Interface ◽  
Liquid Vapor

In microchannel flow boiling, bubble nucleation, growth and flow regime development are highly influenced by channel cross-section and physical phenomena underlying this mechanism are far from being well-established. Relative effects of different forces acting on wall-liquid and liquid-vapor interface of a confined bubble play an important role in heat transfer performances. Therefore, fundamental investigations are necessary to develop enhanced microchannel heat transfer surfaces. Force analysis of vapor bubble dynamics in flow boiling Silicon Nanowire (SiNW) microchannels has been performed based on theoretical, experimental and visualization studies. The relative effects of different forces on flow regime, instability and heat transfer performances of flow boiling in Silicon Nanowire microchannels have been identified. Inertia, surface tension, shear, buoyancy, and evaporation momentum forces have significant importance at liquid-vapor interface as discussed earlier by several authors. However, no comparative study has been done for different surface properties till date. Detailed analyses of these forces including contact angle and bubble flow boiling characteristics have been conducted in this study. A comparative study between Silicon Nanowire and Plainwall microchannels has been performed based on force analysis in the flow boiling microchannels. In addition, force analysis during instantaneous bubble growth stage has been performed. Compared to Plainwall microchannels, enhanced surface rewetting and critical heat flux (CHF) are owing to higher surface tension force at liquid-vapor interface and Capillary dominance resulting from Silicon Nanowires. Whereas, low Weber number in Silicon Nanowire helps maintaining uniform and stable thin film and improves heat transfer performances. Moreover, force analysis during instantaneous bubble growth shows the dominance of surface tension at bubble nucleation and slug/transitional flow which resulted higher heat transfer contact area, lower thermal resistance and higher thin film evaporation. Whereas, inertia force is dominant at annular flow and it helps in bubble removal process and rewetting.

Flow Boiling Dynamics of Water and Nanofluids in a Single Microchannel at Different Heat Fluxes

2015 ◽  
Vol 137 (1) ◽  
Author(s):  
Zachary Edel ◽  
Abhijit Mukherjee
Keyword(s):  
Flow Boiling ◽  
Nucleate Boiling ◽  
Nucleation Site ◽  
Bubble Nucleation ◽  
Heat Fluxes ◽  
Forced Flow ◽  
Electronic Systems ◽  
Rectangular Microchannel ◽  
Nanoparticle Deposition ◽  
Flow Regime Transition

The preferable cooling solution for micro-electronic systems could be forced flow boiling in micro heat exchangers. Nanoparticle deposition affects nucleate boiling via alteration of surface roughness, capillary wicking, wettability, and nucleation site density. In this study, flow boiling was investigated using water and nanofluids in a single rectangular microchannel at different heat fluxes. The observed change in flow regime transition revealed the effect of nanoparticles on the onset of nucleate boiling (ONB) and the onset of bubble elongation (OBE). The addition of nanoparticles was found to stabilize bubble nucleation and growth and increase heat transfer in the thin film regions.

scholarly journals Comparison of the Volume of Fluid and CLSVOF Methods for the Assessment of Flow Boiling in Silicon Microgaps

2017 ◽  
Vol 139 (11) ◽  
Author(s):  
Daniel Lorenzini ◽  
Yogendra Joshi
Keyword(s):  
Phase Change ◽  
Two Phase Flow ◽  
Flow Boiling ◽  
Experimental Studies ◽  
Volume Of Fluid ◽  
Bubble Nucleation ◽  
Operating Conditions ◽  
Substrate Thickness ◽  
Phase Flow ◽  
Two Phase

The three-dimensional (3D) stacking of integrated circuits (ICs), and emergent microelectronic technologies require low-profile cooling solutions for the removal of relatively high heat fluxes. The flow boiling of dielectric refrigerants represents a feasible alternative to such applications by providing compatibility with the electrical interconnections, relatively uniform temperature profiles, and higher heat transfer coefficients than those obtained with single phase-cooling. Despite important experimental evidence in this area has been recently reported in the literature, the modeling of such has remained in basic and limited forms due to the associated complexities with the physics of two-phase flow with phase-change. In an effort to expand the studied possibilities for the modeling of flow boiling, the present investigation compares two different phase-tracking methods for the analysis of such phenomena: the volume of fluid (VOF) and the coupled level set—volume of fluid (CLSVOF) techniques. These interface tracking and reconstruction techniques are coupled with a phase change model that accounts for the mass and energy transfer source terms to the governing equations. The geometric domain is constituted by a silicon microgap 175 μm high with a substrate thickness of 50 μm, and populated with circular pin fins of 150 μm diameter, where the heat conduction is simultaneously solved with temperature dependent properties. The flow boiling regimes and their spatial and temporal evolution are compared between both methods by maintaining the operating conditions. Results indicate that both methods provide a good capability to predict major two-phase flow regimes observed in experimental studies with these types of arrangements. However, the CLSVOF offers a sharper interface reconstruction than the standard VOF method by predicting bubble nucleation and departure mechanisms more closely to experimental observations.

Experiment Research of Vapor Bubble Stochastic Characteristics in a Narrow Rectangular Channel

2016 ◽  
Author(s):  
Shaodan Li ◽  
Yong Li ◽  
Yuansheng Lin ◽  
Zhiguo Wei ◽  
Bangming Li ◽  
...  
Keyword(s):  
Vapor Bubble ◽  
Flow Boiling ◽  
Rectangular Channel ◽  
Nucleation Site ◽  
Bubble Nucleation ◽  
Maximum Diameter ◽  
Working Fluid ◽  
Subcooled Flow Boiling ◽  
Subcooled Flow ◽  
Stochastic Characteristics

In most of the previous studies, the vapor bubble parameters were averaging processed in order to establish the empirical-based correlations or mechanism-based models. While it should be noted that the thermal hydraulic parameters around a bubble in a subcooled flow boiling channel are unsteady, that means the vapor bubbles behaves some stochastic characteristics. In the present research, a high speed visualization experiment was conducted in a subcooled flow boiling narrow rectangular channel to investigate the vapor bubble behavior. The working fluid in the experiment was deionized water. The obtained bubble images were processed by a digital image processing program in order to acquire the bubble parameters. The stochastic features of the bubbles were analyzed based on the experimental results. Two types of bubble behaviors were observed under different working conditions, which results in two types of bubble stochastic features. The results shown that the distribution function of the bubble maximum diameter in a specific nucleation site can be expressed by the normal distribution, while in the whole range of the observation window the distribution of the bubble maximum diameter was expressed by the lognormal distribution. The distribution of the second type bubble diameter depends on the local bubble nucleation site and the upstream bubble behaviors.

Suitability Evaluation of Bubble Departure Diameter and Frequency Models for the Simulation of Subcooled Confined Jet Impingement Boiling

2014 ◽  
Author(s):  
S. Abishek ◽  
R. Narayanaswamy ◽  
V. Narayanan
Keyword(s):  
Heat Transfer ◽  
Bubble Dynamics ◽  
Flow Boiling ◽  
Jet Impingement ◽  
Operating Conditions ◽  
Accurate Estimation ◽  
Momentum Exchange ◽  
Ansys Fluent ◽  
Suitability Evaluation ◽  
Jet Impingement Boiling

Accurate estimation of multiphase turbulence, interphase momentum exchange and bubble dynamics parameters such as bubble departure diameter and frequency is critical for a realistic simulation of flow boiling heat transfer. While there are experimental and mechanistic models available for the estimation of these parameters for rather specific geometric configurations, fluids and operating conditions, there is no specific comprehensive model for jet impingement boiling. Nor is there a consensus on a generalized model, particularly for the ebullition parameters, that could be extended to jet impingement boiling. Hence, a problem-based evaluation of the available models to conform to experimental data is often required. In the present work, a rigorous study is carried out to ascertain the suitability of different bubble departure diameter and departure frequency models for the simulation of confined and submerged, subcooled jet impingement boiling. The choice of ebullition models considered encompass both pool boiling as well as flow boiling based models, developed from both experimental as well as mechanistic approaches. The suitability of the models are evaluated by comparison of the predicted local and surface averaged heat transfer characteristics against experimental boiling data from the present research as well as that available in the literature. The computational simulations are carried out using the finite volume computational solver ANSYS FLUENT 14.5, with necessary customized functions for boiling parameters formulated and integrated into the solver.

Nucleate Boiling Bubble Dynamics in a PDMS Microchannel With a Single Nucleation Site

2011 ◽  
Author(s):  
Haojie Wang ◽  
Xipeng Lin ◽  
David M. Christopher
Keyword(s):  
High Speed ◽  
Bubble Dynamics ◽  
Flow Boiling ◽  
Nucleate Boiling ◽  
Nucleation Site ◽  
Working Fluid ◽  
Heater Surface ◽  
Short Period ◽  
Pdms Microchannel ◽  
Very High

The bubble dynamics for flow boiling in a single microchannel was experimentally studied in the present work. A platinum heater was used as the nucleation site in a 0.1 mm hydraulic diameter PDMS (Polydimethylsiloxane) microchannel with FC72 as the working fluid. A high speed camera was used to visualize the bubble dynamics. The results show that the bubbles grow much slower than predicted by standard correlations due to the very large convective heat transfer to the liquid flowing around the bubble in the microchannel. The results also show that the bubble departure frequency, heat flux and bubble departure diameter are well correlated by two dimensionless parameters that also include the effect of the properties. Finally, the results suggest very high speed dryout and rewetting of the heater surface during the bubble growth with a very short period of more complete rewetting of the heater surface when a bubble separates from the main vapor stem.

Single Bubble Dynamics on a Hydrophobic Surface

2007 ◽  
Author(s):  
Youngsuk Nam ◽  
Gopinath Warrier ◽  
Jinfeng Wu ◽  
Y. Sungtaek Ju
Keyword(s):  
Silicon Substrate ◽  
Bubble Dynamics ◽  
Growth Period ◽  
Hydrophobic Surface ◽  
Nucleation Site ◽  
Bubble Surface ◽  
Bubble Nucleation ◽  
Root Mean Square Roughness ◽  
Static Contact ◽  
Artificial Cavity

The growth and departure of single bubbles on two surfaces with very different wettability is studied using highspeed video microscopy. An artificial cavity of approximately 10μm diameter is microfabricated on a bare and a Teflon-coated silicon substrate to serve as a nucleation site. The static contact angle of water is approximately 40° on the bare silicon substrate and approximately 120° on the Teflon-coated substrate. The bubble departure diameter is observed to be almost three times larger and the growth period almost 60 times longer for the hydrophobic surface than for the hydrophilic surface. The waiting period is practically zero for the hydrophobic surface because a small residual bubble nucleus remains on the cavity from the previous ebullition cycle. Bubble nucleation occurs on nominally smooth hydrophobic regions with root mean square roughness below 4 nm even at superheat as small as 4 °C. Liquid subcooling significantly affects bubble growth on the hydrophobic surface due to the increased bubble surface area.

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