The Dynamics of Bubble Growth at Medium-High Superheat: Boiling in an Infinite Medium and on a Wall

2013 ◽  
Vol 135 (7) ◽  
Author(s):  
Herman D. Haustein ◽  
Alon Gany ◽  
Georg F. Dietze ◽  
Ezra Elias ◽  
Reinhold Kneer
Keyword(s):  
Nusselt Number ◽  
Bubble Growth ◽  
Growth Curves ◽  
Nucleate Boiling ◽  
Empirical Models ◽  
Heated Wall ◽  
Reliable Model ◽  
High Superheat ◽  
Radial Convection ◽  
Convection Dominated

At high superheat, bubble growth is rapid and the heat transfer is dominated by radial convection. This has been found, in the case of a droplet boiling within another liquid and in the case of a bubble growing on a heated wall, leading to similar bubble growth curves. Based on an experimental parametric study for the droplet-boiling case, an empirical model was developed for the prediction of bubble growth, within the radial convection dominated regime (the RCD model) occurring only at high superheat. This model suggests a dependence of R∼t1/3—equivalent to a Nusselt number decreasing over time (Nu∼t−1/3), as opposed to R∼t1/2 —equivalent to a highly-unlikely constant Nusselt number, in most other models. The new model provides accurate prediction for both the droplet boiling and nucleate pool boiling cases, in the medium-high superheat range (0.26<Ste <0.41, 0.19<Ste<0.30, accordingly). By comparison, the new RCD model shows a more consistent prediction, than previous empirical models. However, in the nucleate boiling case, the RCD model requires the foreknowledge of the departure diameter, for which a reliable model still is lacking.

A New Empirical Model for Bubble Growth: Boiling in an Infinite Medium and on a Wall at High Superheat

2011 ◽  
Author(s):  
Herman D. Haustein ◽  
Georg F. Dietze ◽  
Reinhold Kneer
Keyword(s):  
Nusselt Number ◽  
Empirical Model ◽  
Bubble Growth ◽  
Growth Curves ◽  
Nucleate Boiling ◽  
Heated Wall ◽  
First Case ◽  
Reliable Model ◽  
High Superheat ◽  
Radial Convection

At high superheat bubble growth is rapid and the heat transfer is dominated by radial convection. This has been found, in the case of a droplet boiling within another liquid and in the case of a bubble growing on a heated wall, leading to similar bubble growth curves. Based on experiments conducted for the first case, an empirical model is developed for the prediction of bubble growth within the radial convection dominated regime (the RCD model), occurring only at high superheat (0.26<Ste<0.41). This model shows a dependence of R∼t1/3 equivalent to Nusselt number decreasing over time (Nu∼t1/3) as opposed to R∼t1/2 appearing in most other models, leading to a highly unlikely constant Nusselt number. The new model is shown to give accurate predictions for the first case and for the second case at medium-high superheat (0.19<Ste<0.30, experimental data taken from literature). A comparison of the RCD model to other models, shows a more consistent and accurate prediction. However, in the second case (nucleate boiling) the RCD model requires the foreknowledge of the departure diameter, for which a reliable model still is lacking.

Experimental Observation on Bubble Dynamics During Nucleate Boiling in Micro/Mini/Macro Tubes

2011 ◽  
Author(s):  
Di Wu ◽  
Ying Piao ◽  
Yuan-yuan Duan ◽  
Zhen Yang
Keyword(s):  
Thin Film ◽  
Bubble Growth ◽  
Bubble Dynamics ◽  
Thin Liquid Film ◽  
Nucleate Boiling ◽  
Tube Diameter ◽  
Heated Wall ◽  
Growth Stages ◽  
Positive Interaction ◽  
Liquid Vapor

A series of experiments was conducted to observe nucleate boiling phenomena in horizontal tubes with inner diameters varying from 0.05 mm to 3.0 mm. Diverse behaviors of bubble growth were explored, identified by which tubes were classified into micro, mini and macro scales. In micro tubes (Di ≤ 200 μm), the liquid was emitted instantaneously with extremely fast liquid-vapor interfacial movement, referred as explosive emission boiling phenomenon. It is hard to record bubble growth process with high speed camera. In mini tubes (200 μm < Di < 2.5 mm), though liquid was also emitted outsides, the interface moves relative slow and the whole process of bubble growth can be observed. Two distinct stages, referred as spherical and oblate bubble growth stages, were divided. In macro tubes (Di ≥ 2.5 mm), only spherical bubble growth stage exists and the growth rate is much smaller than that in mini tubes. Furthermore, the mechanism of diverse bubble dynamics was analyzed. In mini/micro tubes, decreasing tube diameter can trigger a transition from spherical to oblate bubble growth and consequently establish a thin film between liquid-vapor interface and heated wall. The thin liquid film evaporates vigorously and accelerates the interfacial movement, which reversely enhances evaporation of thin film. A positive interaction between interfacial movement and thin film evaporation establishes, resulting in the interface moving faster and faster and consequently emitted liquid outsides instantaneously. In macro tubes, as tube diameter increasing, the transition and sequential positive interaction can not be raised. Hence, the bubble maintains growing spherically as that in pool boiling.

Direct numerical simulation of a turbulent jet impinging on a heated wall

2015 ◽  
Vol 764 ◽  
pp. 362-394 ◽  
Author(s):  
T. Dairay ◽  
V. Fortuné ◽  
E. Lamballais ◽  
L.-E. Brizzi
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Nusselt Number ◽  
Direct Numerical Simulation ◽  
Temperature Fields ◽  
Heated Wall ◽  
Small Scale ◽  
Turbulent Regime ◽  
High Heat Transfer ◽  
Radial Evolution

AbstractDirect numerical simulation (DNS) of an impinging jet flow with a nozzle-to-plate distance of two jet diameters and a Reynolds number of 10 000 is carried out at high spatial resolution using high-order numerical methods. The flow configuration is designed to enable the development of a fully turbulent regime with the appearance of a well-marked secondary maximum in the radial distribution of the mean heat transfer. The velocity and temperature statistics are validated with documented experiments. The DNS database is then analysed focusing on the role of unsteady processes to explain the spatial distribution of the heat transfer coefficient at the wall. A phenomenological scenario is proposed on the basis of instantaneous flow visualisations in order to explain the non-monotonic radial evolution of the Nusselt number in the stagnation region. This scenario is then assessed by analysing the wall temperature and the wall shear stress distributions and also through the use of conditional averaging of velocity and temperature fields. On one hand, the heat transfer is primarily driven by the large-scale toroidal primary and secondary vortices emitted periodically. On the other hand, these vortices are subjected to azimuthal distortions associated with the production of radially elongated structures at small scale. These distortions are responsible for the appearance of very high heat transfer zones organised as cold fluid spots on the heated wall. These cold spots are shaped by the radial structures through a filament propagation of the heat transfer. The analysis of probability density functions shows that these strong events are highly intermittent in time and space while contributing essentially to the secondary peak observed in the radial evolution of the Nusselt number.

High-Resolution Measurements at Nucleate Boiling of Pure FC-84 and FC-3284 and Its Binary Mixtures

2009 ◽  
Vol 131 (12) ◽  
Author(s):  
Enno Wagner ◽  
Peter Stephan
Keyword(s):  
Binary Mixtures ◽  
High Speed ◽  
Contact Region ◽  
Infrared Camera ◽  
Nucleate Boiling ◽  
Heated Wall ◽  
Rear Side ◽  
Phase Contact ◽  
Pure Fluids ◽  
Three Phase

In a special boiling cell, vapor bubbles are generated at single nucleation sites on top of a 20μm thick stainless steel heating foil. An infrared camera captures the rear side of the heating foil for analyzing the temperature distribution. The bubble shape is recorded through side windows with a high-speed camera. Global measurements were conducted, with the pure fluids FC-84 and FC-3284 and with its binary mixtures of 0.25, 0.5, and 0.75mole fraction. The heat transfer coefficient (HTC) in a binary mixture is less than the HTC in either of the single component fluid alone. Applying the correlation of Schlünder showed good agreement with the measurements (1982, “Über den Wärmeübergang bei der Blasenverdampfung von Gemischen,” Verfahrenstechnik, 16(9), pp. 692–698). Furthermore, local measurements were arranged with high lateral and temporal resolution for single bubble events. The wall heat flux was computed and analyzed, especially at the three-phase-contact line between liquid, vapor, and heated wall. The bubble volume and the vapor production rate were also investigated. For pure fluids, up to 50–60% of the latent heat flows through the three-phase-contact region. For mixtures, this ratio is clearly reduced and is about 35%.

Inverse Determination of the Local Heat Transfer Coefficients for Nucleate Boiling on a Horizontal Cylinder

2003 ◽  
Vol 125 (6) ◽  
pp. 1087-1095 ◽  
Author(s):  
H. Louahlia-Gualous ◽  
P. K. Panday ◽  
E. A. Artioukhine
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Pool Boiling ◽  
Gradient Methods ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Nucleate Boiling ◽  
Nucleate Pool Boiling ◽  
Transfer Coefficients ◽  
Iterative Regularization

This article treats the local heat transfer for nucleate pool boiling around the cylinder using the inverse heat conduction analysis. The physical model considers a half section of a cylinder with unknown surface temperature and heat flux density. The iterative regularization and the conjugate gradient methods are used for solving the inverse analysis. The local Nusselt number profiles for nucleate pool boiling are presented and analyzed for different electric heat. The mean Nusselt number estimated by IHCP is closed with the measured values. The results of IHCP are compared to those of Cornewell and Houston (1994), Stephan and Abdelsalam (1980) and Memory et al. (1995). The influence of the error of the measured temperatures and the error in placement of the thermocouples are studied.

An Experimental Investigation of the Effect of Subcooling on Bubble Growth and Waiting Time in Nucleate Boiling

1985 ◽  
Vol 107 (1) ◽  
pp. 168-174 ◽  
Author(s):  
E. A. Ibrahim ◽  
R. L. Judd
Keyword(s):  
Heat Flux ◽  
Waiting Time ◽  
Bubble Growth ◽  
Nucleate Boiling ◽  
Copper Surface ◽  
Growth Theory ◽  
Growth Time ◽  
Time Data ◽  
Relationship Of ◽  
Different Levels

The effect of subcooling on bubble waiting time and growth time for water boiling on a copper surface was examined in conjunction with measurements obtained over a range of subcooling from 0 to 15°C and three different levels of heat flux 166, 228, and 291 kW/m2. The growth-time data was successfully correlated with a model that combined the bubble growth theory of Mikic, Rohsenow, and Griffith with the bubble departure diameter relationship of Staniszewski, thereby establishing confidence in the measuring procedure. The waiting time data agreed with the predictions of the Han and Griffith waiting time theory at lower levels of subcooling but then showed a behavior contrary to that predicted for higher levels of subcooling.

Numerical study of bubble growth and merger characteristics during nucleate boiling

2019 ◽  
Vol 112 ◽  
pp. 7-19
Author(s):  
Jingliang Bi ◽  
David M. Christopher ◽  
Dawei Zhao ◽  
Jianjun Xu ◽  
Yanping Huang
Keyword(s):  
Bubble Growth ◽  
Numerical Study ◽  
Nucleate Boiling

scholarly journals Droplet desorption modes at high heat flux

2019 ◽  
Vol 196 ◽  
pp. 00002
Author(s):  
Sergey Misyura ◽  
Anton Meleshkin
Keyword(s):  
Temperature Field ◽  
Salt Solution ◽  
Ambient Air ◽  
Nucleate Boiling ◽  
High Heat ◽  
Droplet Surface ◽  
Aqueous Salt Solution ◽  
Heated Wall ◽  
High Heat Flux ◽  
Desorption Rate

Nonisothermal droplet desorption of aqueous salt solution H2O/LiBr during nucleate boiling was studied experimentally. A droplet was placed on a horizontal heated wall. The initial concentration of salt C0 = 25 %. The wall temperature Tw = 120 °C and ambient air pressure is 1 bar. Thermal images of the temperature field on the droplet surface show an extremely non-uniform temperature field. At nucleate boiling in LiBr salt solution it is incorrect to predict the desorption behavior in stationary approximation. It was previously believed that the rate of evaporation does not vary with time. For the first time it is shown that the desorption rate is divided into several characteristic time intervals. These intervals is characterized by a significant change in the desorption rate.

Simulation of Nucleate Boiling With Interfacial Temperature Gradients and Sharp Interface

2018 ◽  
Author(s):  
Isaac Perez-Raya ◽  
Satish G. Kandlikar
Keyword(s):  
Heat Transfer ◽  
Contact Line ◽  
Growth Rates ◽  
Bubble Growth ◽  
Heated Surface ◽  
Nucleate Boiling ◽  
Bubble Nucleation ◽  
Heat Fluxes ◽  
Temperature Gradients ◽  
Interfacial Temperature

Effective heat transfer techniques benefit the development of nuclear and fossil fuel powered steam generators, high power electronic devices, and industrial refrigeration systems. Boiling dissipates large heat fluxes while keeping a low and a constant surface temperature. However, studies of the fluid behavior surrounding the bubble and the heat transfer near the contact-line are scare due to difficulties of flow visualization, chaotic conditions, and small length scales. The preset study shows the simulation of bubble growth over a heated surface from conception to departure. The computation of mass transfer with interfacial temperature gradients leads to proper bubble growth rates. Models to include the interface sharpness uncover the dynamic and thermal interaction between the interface and the fluid. Results indicate that the nucleation of a bubble (in water at 1 atm with 6.2 K wall superheat) has an influence region of 2Db (where Db is the departure bubble diameter). In addition, results reveal a thin thermal film near the interface that increases the heat transfer at the contact-line region. Numerical bubble growth rates compare well with experimental data on single bubble nucleation.

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