Experimental study of nucleate boiling heat transfer under low gravity conditions using TLCs for high resolution temperature measurements

Wagner, E.; Sodtke, Christof; Schweizer, Nils; Stephan, Peter

doi:10.1007/s00231-006-0146-2

Cited by 27 publications

(6 citation statements)

References 7 publications

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“…Near this threephase contact area, which is about one-micron wide, the evaporation rate is extremely high and induces a strong local cooling of the heated wall (Figure 2, bottom left panel). This observation was confirmed during microgravity experiments: indeed, in the absence of buoyancy, the growth rate of the vapour bubbles is slowed down and their detachment is delayed, which enables measurements at higher spatial and temporal resolutions [6]. Such high local evaporation rates can now be predicted by advanced models of transient nucleate boiling.…”

Section: Pool and Convective Boilingmentioning

confidence: 54%

See 1 more Smart Citation

Bubbles, drops, films: transferring heat in space

Celata

Colin²,

Colinet³

et al. 2008

Europhysics News

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hase-change phenomena play an important role in our daily life. They are of great interest for cooling electronic components or engines. They are also used in vapour generators. At least two thirds of the electrical energy produced in the world uses this technique. Two-phase flows are also present in space applications: energy production, electronic cooling devices and, as one can expect in the future, in waste water treatment and life support systems for long-duration space exploration missions. So, in many applications high heat fluxes are achieved by utilising the latent heat associated with the phase change from liquid to vapour. However, the physical mechanisms involved are intricate and many questions remain unanswered: how does a bubble nucleate on a heated surface? When will bubbles completely cover a hot surface? What is the amount of heat transferred by boiling evaporation or reversely, by condensation?The field clearly is at the crossroads of thermodynamics, fluid dynamics, materials sciences and physical chemistry of interfaces. Because of the complexity of the coupling effects in systems involving phase change and the lack of reliable prediction capabilities, the development of industrial devices is essentially based on empirical rules. Their utilisation then relies on correlations established between operational parameters and heat transfer performances, which cover a limited range of parameters and thus cannot be extrapolated to other situations and in particular to a microgravity environment.Progress in the field requires a better understanding of the basic mechanisms and the development of predictive capabilities. This is supported by recent advances in measurement techniques and an increase in computing performances. It is however still difficult, if not impossible to discriminate between these individual basic phenomena.Phase change occurs at interfaces, the boundaries separating different phases. Although molecularly thin, liquid-gas interfaces play a major role in the overall behaviour of the system. It is therefore crucial to understand the details of their static and dynamic behaviour. Because of the principle of minimal surface energy, an interface ideally tends to assume a spherical shape. However, on Earth, the gradient of hydrostatic pressure leads to the flattening of drops and elongation of bubbles. In a flow, viscous and inertia effects are also responsible for pressure gradients and thereby, for interface deformation. In liquid-vapour flows, the density difference is very high and gravity effects dominate capillary and viscous effects. Gravity generates thermal convection and causes bubble detachment during boiling and stabilises liquid films. Under normal gravity it is thus impossible to separate the various mechanisms involved.Microgravity is a good tool to improve the quantitative understanding of these physical mechanisms. Experiments have been performed in free-fall conditions at different time scales demonstrating the relevance of two-phase flow studies in space. Several inst...

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Section: Pool and Convective Boilingmentioning

confidence: 54%

“…Celata 1 , C. Colin 2 , P. Colinet 3 , P. di marco 4 , t. gambaryan-roisman 5 , o. Kabov 3 , o. Kyriopoulos 5 , P. stephan 5 , l. tadrist 6 and C. tropea 5 1 ENEA Roma, 2 IMF Toulouse, 3 UL Brussels, 4 UNI Pisa, 5 TU Darmstadt, 6 …”

Section: [Physics In Space]mentioning

confidence: 99%

Bubbles, drops, films: transferring heat in space

Celata

Colin²,

Colinet³

et al. 2008

Europhysics News

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“…Nucleate boiling in micro-gravity conditions is actually a topic of large scientific interest, and a number of questions remain unanswered. For instance there are open questions on the quantitative impact of the gravity level on the critical heat flux and more in general on the heat transfer behaviour [1,2]. Moreover, the impact of wall superheat and wetting properties, that have been largely investigated in normal gravity conditions, are not clearly understood in micro-gravity conditions [3,4].…”

Section: Introductionmentioning

confidence: 99%

“…However, the drawbacks of these methodologies are a short observation time and continuously varying gravity conditions. The gravity acceleration never reaches a zero value, but typically a minimum value that varies between 10 À2 et 10 À6 g [8,9,7,10,2]. To achieve longer times and lower gravity levels down to 10 À7 g, orbital flights must be considered, onboard a space station for instance, but these experiments are rare and expensive [11,3].…”

Section: Introductionmentioning

confidence: 99%

Direct numerical simulation of nucleate boiling in zero gravity conditions

Urbano

Tanguy

Colin

2019

International Journal of Heat and Mass Transfer

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Understanding and controlling nucleate pool boiling phenomena in zero gravity conditions is fundamental for space applications. An analytical model for the equilibrium radius reached by a bubble nucleated in sub-cooled conditions is established in this work and verified numerically. Indeed, direct numerical simulations of two phase flows conjugated with the heat conduction in the solid wall are carried out in order to verify and correct the analytical model. Fine grids, with cells size of the order of the micron, are mandatory in order to capture the subtle equilibrium between condensation and evaporation that characterises stationary conditions. This has been possible thanks to the house made solver DIVA, validated for nucleate pool boiling simulations, and that permits to carry out parallel numerical simulations. Results show that the equilibrium radius of the bubble is a function of the thermal gradient, of the Jakob numbers associated with condensation and evaporation and of the apparent contact angle. The analysis of the thermal field is carried out and an interpretation of the physical processes that characterise the equilibrium is given. In addition, useful information on the heat transfer behaviour, reported in terms of Nu numbers, completes the work.

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“…Microgravity nucleate boiling experiment was designed with an artificial nucleation site on a thin electrically heated wall introducing a two-dimensional, high resolution temperature measurement technique using unencapsulated thermochromic liquid crystals and a high speed color camera (Wagner et al 2006). As a result, transient measurements of the temperature profile close to the three phase contact line at the base of a vapor bubble and the corresponding shapes of the bubble were obtained.…”

Section: Introductionmentioning

confidence: 99%

Heat Transfer and Bubble Behaviors in Microgravity Pool Boiling in ESA Parabolic Flight Experiment

Kawanami

Ohta

Kabov

et al. 2009

Microgravity Sci. Technol.

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To clarify the relation between local heat transfer and bubble behaviors in pool boiling under microgravity conditions, a transparent heating surface, which has multiple array of heaters and temperature sensors, and experimental apparatus were developed to make the measurement of local heat transfer characteristics and the observation of liquid-vapor behavior simultaneously possible. In this paper, preliminary results of the microgravity pool boiling experiments conducted in ESA 49th parabolic flight campaign were reported. It was found that the bubble behaviors were strongly affected by the fluctuation of gravity in lowgravity period, and the effect of gravity on the bubble behaviors and heat transfer was dependent on the liquid subcooling. In the case of high subcooling, boiling bubbles were pushed on to the heating surface

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Experimental study of nucleate boiling heat transfer under low gravity conditions using TLCs for high resolution temperature measurements

Cited by 27 publications

References 7 publications

Bubbles, drops, films: transferring heat in space

Bubbles, drops, films: transferring heat in space

Direct numerical simulation of nucleate boiling in zero gravity conditions

Heat Transfer and Bubble Behaviors in Microgravity Pool Boiling in ESA Parabolic Flight Experiment

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