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%.

Incipient Flow Boiling in a Vertical Channel With a Wavy Wall

2010 ◽  
Author(s):  
T. Netz ◽  
R. Shalem ◽  
J. Aharon ◽  
G. Ziskind ◽  
R. Letan
Keyword(s):  
Heat Transfer ◽  
Temperature Field ◽  
High Speed ◽  
Flow Boiling ◽  
Heated Surface ◽  
Vertical Channel ◽  
Infrared Camera ◽  
Heat Fluxes ◽  
Heated Wall ◽  
Boiling Incipience

In the present study, incipient flow boiling of water is studied experimentally in a square-cross-section vertical channel. Water, preheated to 60–80 degrees Celsius, flows upwards. The channel has an electrically heated wall, where the heat fluxes can be as high as above one megawatt per square meter. The experiment is repeated for different water flow rates, and the maximum Reynolds number reached in the present study is 27,300. Boiling is observed and recorded using a high-speed digital video camera. The temperature field on the heated surface is measured with an infrared camera and a software is used to obtain quantitative temperature data. Thus, the recorded boiling images are analyzed in conjunction with the detailed temperature field. The dependence of incipient boiling on the flow and heat transfer parameters is established. For a flat wall, the results for various velocities and subcooling conditions agree well with the existing literature. Furthermore, three different wavy heated surfaces are explored, having the same pitch of 4mm but different amplitudes of 0.25mm, 0.5mm and 0.75mm. The effect of surface waviness on single-phase heat transfer and boiling incipience is shown. The differences in boiling incipience on various surfaces are elucidated, and the effect of wave amplitude on the results is discussed.

scholarly journals Thermocapillary rupture of a horizontal liquid layer on a silicon substrate

2019 ◽  
Vol 196 ◽  
pp. 00041
Author(s):  
Dmitry Kochkin ◽  
Valentin Belosludtsev ◽  
Veronica Sulyaeva
Keyword(s):  
Experimental Study ◽  
Contact Line ◽  
High Speed ◽  
Video Camera ◽  
Phase Contact ◽  
High Speed Video ◽  
High Speed Video Camera ◽  
Three Phase ◽  
Breakdown Phenomenon ◽  
Dry Spot

This paper is an experimental study of thermocapillary breakdown phenomenon in a horizontal film of liquid placed on a silicon nonisothermal substrate. With the help of a high-speed video camera the speed of the three-phase contact line was measured during the growth of a dry spot.

scholarly journals On the mechanism of droplet rolling and spinning in inclined hydrophobic plates in wedge with different wetting states

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Bekir Sami Yilbas ◽  
Mubarak Yakubu ◽  
Abba Abdulhamid Abubakar ◽  
Hussain Al-Qahtani ◽  
Ahmet Sahin ◽  
...  
Keyword(s):  
Experimental Data ◽  
High Speed ◽  
Recording System ◽  
Experimental Results ◽  
Phase Contact ◽  
Droplet Motion ◽  
3D Space ◽  
Three Phase ◽  
Tangential Momentum ◽  
Recorded Data

AbstractA water droplet rolling and spinning in an inclined hydrophobic wedge with different wetting states of wedge plates is examined pertinent to self-cleaning applications. The droplet motion in the hydrophobic wedge is simulated in 3D space incorporating the experimental data. A high-speed recording system is used to store the motion of droplets in 3D space and a tracker program is utilized to quantify the recorded data in terms of droplet translational, rotational, spinning, and slipping velocities. The predictions of flow velocity in the droplet fluid are compared with those of experimental results. The findings revealed that velocity predictions agree with those of the experimental results. Tangential momentum generated, via droplet adhesion along the three-phase contact line on the hydrophobic plate surfaces, creates the spinning motion on the rolling droplet in the wedge. The flow field generated in the droplet fluid is considerably influenced by the shear rate created at the interface between the droplet fluid and hydrophobic plate surfaces. Besides, droplet wobbling under the influence of gravity contributes to the flow inside the rolling and spinning droplet. The parallel-sided droplet path is resulted for droplet emerging from the wedge over the dusty surface.

Boiling Heat Transfer With Binary Mixtures: Part II—Flow Boiling in Plain Tubes

1998 ◽  
Vol 120 (2) ◽  
pp. 388-394 ◽  
Author(s):  
S. G. Kandlikar
Keyword(s):  
Heat Transfer ◽  
Binary Mixtures ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Nucleate Boiling ◽  
Mean Deviation ◽  
Data Set ◽  
Pure Fluids ◽  
Starting Point ◽  
Data Points

Flow boiling heat transfer with pure fluids comprises convective and nucleate boiling components. In flow boiling of binary mixtures, in addition to the suppression effects present in pool boiling, the presence of flow further modifies the nucleate boiling characteristics. In the present work, the flow boiling correlation by Kandlikar (1990, 1991b) for pure fluids is used as the starting point, and the mixture effects derived in Part I (Kandlikar, 1998) of this paper are incorporated. Three regions are defined on the basis of a volatility parameter, V1 = (cp/ΔhLG)(k/D12)1/2|(y1 − x1)dT/dx1|. They are: region I—near azeotropic, region II—moderate diffusion-induced suppression, and region III—severe diffusion-induced suppression. The resulting correlation is able to correlate over 2500 data points within 8.3 to 13.3 percent mean deviation for each data set. Furthermore, the α–x trend is represented well for R-12/R-22, R-22/R-114, R-22/R-152a, R-500, and R-132a/R-123 systems. Electrically heated stainless steel test sections as well as fluid-heated copper test sections are both covered under this correlation.

Effect of Surface Roughness on the Behavior of Bubbles Growing and Departing From a Heated Surface

2017 ◽  
Author(s):  
Navdeep S. Dhillon
Keyword(s):  
Surface Roughness ◽  
Contact Line ◽  
Bubble Growth ◽  
High Speed ◽  
Heated Surface ◽  
Scaling Analysis ◽  
Phase Contact ◽  
Bubble Behavior ◽  
Three Phase ◽  
Effect Of Surface

The phenomenon of bubble growth on a heated surface is of fundamental importance in many scientific and engineering applications, including boiling heat transfer. Although the growth of a homogeneous bubble in a pool of hot liquid is well understood, bubbles growing on hot solid surfaces involve evaporation from a three-phase contact line and therefore exhibit several peculiar features. One of these is the effect of surface texture and wetting properties on the size and timing of bubbles that form and depart from a uniformly heated surface. Here, we present pool boiling experimental results elucidating this important phenomenon. Using high-speed optical imaging, we perform a comparative study of the process of growth and departure of bubbles on plain and rough surfaces and explore the different factors that dictate this behavior. Using scaling analysis, we analyze the primary forces acting on a growing bubble and show that the effect of surface roughness on bubble behavior can be explained in terms of the dependence of these forces on the rate of bubble growth and in-turn on the rate of thin-film evaporation from the three-phase contact line of the bubble.

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