A Study of Bubble Departure in Forced-Convection Boiling

1968 ◽  
Vol 90 (2) ◽  
pp. 223-230 ◽  
Author(s):  
N. Koumoutsos ◽  
R. Moissis ◽  
A. Spyridonos
Keyword(s):  
Forced Convection ◽  
Liquid Flow ◽  
High Speed ◽  
Water System ◽  
Heating Surface ◽  
Nucleate Boiling ◽  
High Speed Photography ◽  
Spherical Bubble ◽  
Velocity Relationship ◽  
Departure Size

Visual observations in a boiling liquid flow indicate that, as the flow velocity is increased, the size of bubbles leaving the heating surface decreases. The purpose of this investigation is to arrive at a criterion for bubble departure in forced-convection nucleate boiling. Photographic studies indicate that a little before departure a “neck” is formed joining the almost spherical bubble to the heating surface. From a consideration of the hydrodynamic stability of the bubble-and-neck model, the departure-size-to-velocity relationship may be predicted. Measured departure radii in a forced-convection boiling water system taken by means of high-speed photography are satisfactorily correlated with the results derived analytically.

An Experimental Study on Saturated Liquid Nitrogen’s Boiling Under Transient Pulsed Laser Irradiation

2004 ◽  
Author(s):  
Zhaoyi Dong ◽  
Xiulan Huai ◽  
G.-X. Wang
Keyword(s):  
Temperature Variation ◽  
High Speed ◽  
Short Pulse ◽  
Heating Surface ◽  
High Heat ◽  
Measuring System ◽  
Experimental Result ◽  
High Speed Photography ◽  
High Heat Flux ◽  
Explosive Boiling

Liquid nitrogen (LN2) was widely applied in many areas, but researches on the boiling behavior under the transient high heat flux have not been reported. In this paper, the high power short pulse duration laser was used to heat the saturated LN2 rapidly, and the high-speed photography aided by the spark light system was employed to take series of photos which displayed the process of LN2’s boiling behavior under such conditions. At the same time, a special temperature measuring system was applied to record the temperature variation of the heating surface. The experimental result disclosed that at the earlier stage of laser heating, an explosive boiling would happen within LN2. After the newly-defined changeover time, the conventional boiling behavior would follow. Therefore the changeover time became an important index to distinguish these two kinds of boiling behaviors. By analyzing the temperature variation of the heating surface, it is found that the latent heat released by the crack of bubbles in explosive boiling is an important factor that greatly influences the boiling heat transfer mechanism.

scholarly journals The Simultaneous Analysis of Droplets’ Impacts and Heat Transfer during Water Spray Cooling Using a Transparent Heater

Water ◽  
2021 ◽  
Vol 13 (19) ◽  
pp. 2730
Author(s):  
Vladimir Serdyukov ◽  
Nikolay Miskiv ◽  
Anton Surtaev
Keyword(s):  
Heat Transfer ◽  
High Speed ◽  
Heating Surface ◽  
Nucleate Boiling ◽  
Spray Cooling ◽  
Capillary Waves ◽  
Heat Fluxes ◽  
Small Scale ◽  
Unsteady Temperature ◽  
The Impact

This paper demonstrates the advantages and prospects of transparent design of the heating surface for the simultaneous study of the hydrodynamic and thermal characteristics of spray cooling. It was shown that the high-speed recording from the reverse side of such heater allows to identify individual droplets before their impact on the forming liquid film, which makes it possible to measure their sizes with high spatial resolution. In addition, such format enables one to estimate the number of droplets falling onto the impact surface and to study the features of the interface evolution during the droplets’ impacts. In particular, the experiments showed various possible scenarios for this interaction, such as the formation of small-scale capillary waves during impacts of small droplets, as well as the appearance of “craters” and splashing crowns in the case of large ones. Moreover, the unsteady temperature field during spray cooling in regimes without boiling was investigated using high-speed infrared thermography. Based on the obtained data, the intensity of heat transfer during spray cooling for various liquid flow rates and heat fluxes was analyzed. It was shown that, for the studied regimes, the heat transfer coefficient weakly depends on the heat flux density and is primarily determined by the flow rate. In addition, the comparison of the processes of spray cooling and nucleate boiling was made, and an analogy was shown in the mechanisms that determine their intensity of heat transfer.

Laser Interferometric Investigation of the Microlayer Evaporation Phenomenon

1975 ◽  
Vol 97 (1) ◽  
pp. 88-92 ◽  
Author(s):  
C. M. Voutsinos ◽  
R. L. Judd
Keyword(s):  
Heat Transfer ◽  
High Speed ◽  
Laser Interferometry ◽  
Nucleate Boiling ◽  
High Speed Photography ◽  
Heater Surface ◽  
Nucleate Boiling Heat Transfer ◽  
Interferometric Investigation ◽  
Microlayer Evaporation ◽  
Laser Interferometric

An experimental investigation is presented in which the growth and evaporation of the microlayer underlying a bubble forming on a glass heater surface has been studied using laser interferometry and high speed photography. The results presented for a single bubble indicate that the microlayer thickness is of the order of 5 μm. Subsequent analysis of these results confirms that the microlayer evaporation phenomenon is a significant heat transfer mechanism, representing approximately 25 percent of the total nucleate boiling heat transfer rate for the conditions investigated.

Thermal-Fluid Phenomena Induced by Nanosecond-Pulse Heating of Materials in Water

2001 ◽  
Vol 123 (6) ◽  
pp. 1123-1132 ◽  
Author(s):  
I. Ueno ◽  
M. Shoji
Keyword(s):  
High Speed ◽  
Bubble Formation ◽  
Water System ◽  
Solid Material ◽  
Laser Wavelength ◽  
High Speed Photography ◽  
Time Resolved ◽  
Pump And Probe ◽  
Shock Wave Generation ◽  
Speed Up

Thermal-hydraulic phenomena adjacent to the liquid metal-water and solid material-water interfaces induced by nanosecond pulsed Nd:YAG laser (wavelength: 532 nm, FWHM: ∼13 ns) heating with the fluence F of 5.0×101∼1.0×103 mJ/cm2 were experimentally investigated. By applying the high-speed photography with a frame speed up to 2.0×107 fps, the aspects of the bubble formation, shock wave generation and propagation were observed. The bubble formation on the heated material’s surface of about 80 nm in diameter was detected in Si-water system from the time-resolved reflection (TRR) signal by applying the pump and probe method.

Flow Boiling on Micropin Fins Entrenched Inside a Microchannel—Flow Patterns and Bubble Departure Diameter and Bubble Frequency

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
Santosh Krishnamurthy ◽  
Yoav Peles
Keyword(s):  
High Speed ◽  
Flow Boiling ◽  
Bubbly Flow ◽  
Nucleate Boiling ◽  
Flow Patterns ◽  
Heat Fluxes ◽  
High Speed Photography ◽  
Bubble Frequency ◽  
Pin Fins ◽  
Parallel Microchannels

Flow boiling of HFE 7000 in five parallel microchannels of 222 μm hydraulic diameter, each containing a single row of 24 in-line 100 μm pin fins, was investigated. High speed photography revealed the dominant flow patterns, namely, the bubbly flow, the multiple flow, and the wavy-annular flow. The interaction of the bubble with the pin fins during nucleate boiling from G=350 kg/m2 s to G=827 kg/m2 s and wall heat fluxes from 10 W/cm2 to 110 W/cm2 is detailed.

Vibration Mechanisms of a Heated Rod Due to Subcooled Boiling Flow

2006 ◽  
Author(s):  
M. R. Nematollahi ◽  
M. H. Akbari
Keyword(s):  
Quantitative Estimate ◽  
High Speed ◽  
Bubble Formation ◽  
Heating Surface ◽  
High Speed Photography ◽  
Subcooled Boiling ◽  
Bubble Behavior ◽  
Boiling Flow ◽  
Excitation Force ◽  
Power Densities

Vibration characteristics of subcooled boiling flow on thin and long structures such as a heating rod were recently investigated by the authors. The results show that the intensity of the subcooled boiling-induced vibration (SBIV) was influenced strongly by the conditions of subcooling temperature, linear power density and flow velocity. Implosive bubble formation and collapse are the main nature of subcooled boiling, and their behavior are the only sources to originate SBIV. Therefore, in order to explain the phenomenon of SBIV, it is essential to obtain reliable information about bubble behavior in subcooled boiling conditions. This was investigated at different conditions of coolant subcooling temperatures of 25 to 75°C, coolant flow velocities of 16 to 53 cm/s, and linear power densities of 100 to 600 W/cm. High speed photography at 13,500 frames per second was performed at these conditions. The results show that even at the highest subcooling condition, the absolute majority of bubbles collapse very close to the surface after detaching from the heating surface. Based on these observations, a simple model of surface tension and momentum change is introduced to offer a rough quantitative estimate of the force exerted on the heating surface. The formation of a typical bubble in subcooled boiling is predicted to exert an excitation force in the order of 10−4 N.

On the Influence of Heating Surface Structure on Bubble Detachment in Sub-Cooled Nucleate Boiling Flows

2006 ◽  
Author(s):  
Wen Wu ◽  
Peipei Chen ◽  
Barclay G. Jones ◽  
Ty A. Newell
Keyword(s):  
Surface Structure ◽  
High Speed ◽  
Bubble Dynamics ◽  
Bubble Radius ◽  
Heating Surface ◽  
Nucleate Boiling ◽  
Bubble Detachment ◽  
Lift Off ◽  
R 134A ◽  
Bubble Movement

This research examines the influence of heating surface structure on bubble detachment, which includes bubble departure and bubble lift-off, under sub-cooled nucleate boiling condition, in order to obtain better understanding to the bubble dynamics on horizontal flat heat exchangers. Refrigerant R-134a is chosen as a simulant fluid due to its merits of having smaller surface tension, reduced latent heat, and lower boiling temperature than water. Experiments were run with varying experimental parameters e.g. pressure, inlet sub-cooled level, and flow rate, etc. High speed digital images at frame rates up to 4000 frames/s were obtained, showing characteristics of bubble movement. Bubble radius and center coordinates were calculated via Canny’s algorithm for edge detection and Fitzgibbon’s algorithm for ellipse fitting. Results were compared against the model proposed by Klausner et al. for prediction of bubble detachment sizes. Good overall agreement was shown, with several minor modifications and suggestions made to the assumptions of the model.

Effects of Heating Surface Materials on a Liquid–Solid Contact State in a Sessile Drop-Boiling System

1993 ◽  
Vol 115 (1) ◽  
pp. 222-230 ◽  
Author(s):  
S. Inada ◽  
W.-J. Yang
Keyword(s):  
High Speed ◽  
Sessile Drop ◽  
Bubble Radius ◽  
Heating Surface ◽  
Experimental Investigations ◽  
High Speed Photography ◽  
Solid Contact ◽  
Contact State ◽  
Interfacial Pressure ◽  
The Relationship

Three experimental investigations are performed on the liquid–solid contact state at the instant when a liquid comes in contact with a heating surface in the transition-boiling regime between the maximum evaporation rate point and the spheroidal state: (1) measuring the piezoelectric potential by means of a quartz oscillator being placed on the heating surface, (2) monitoring the boiling sound generated at the instant of liquid–solid contact using a condenser microphone, and (3) observation of drop behavior, by means of high-speed photography. The information obtained from these three investigations is synthesized to quantify the liquid–solid contact state. The study has disclosed the roles of thermal properties and heating surface temperatures on the endurance time of the instantaneous liquid–solid contact state and the relationship between the critical bubble radius and the measured vapor–liquid interfacial pressure difference.

Subcooled Flow Boiling in a Minichannel

2009 ◽  
Author(s):  
Akira Oshima ◽  
Koichi Suzuki ◽  
Chungpyo Hong ◽  
Masataka Mochizuki
Keyword(s):  
Heat Flux ◽  
High Speed ◽  
Flow Boiling ◽  
Heating Surface ◽  
Nucleate Boiling ◽  
High Heat Flux ◽  
Subcooled Flow Boiling ◽  
Maximum Heat ◽  
High Speed Video ◽  
Subcooled Flow

It has been considered that the dry-out is easy to occur in boiling heat transfer for a small channel, a mini or microchannel because the channel was easily filled with coalescing vapor bubbles. In the present study, the experiments of subcooled flow boiling of water were performed under atmospheric condition for a horizontal rectangular channel of which size is 1mm in height and 1mm in width with a flat heating surface of 10mm in length and 1mm in width placed on the bottom of the channel. The heating surface is a top of copper heating block and heated by ceramics heaters. In the high heat flux region of nucleate boiling, about 70 ∼ 80 percent of heating surface was covered with a large coalescing bubble and the boiling reached critical heat flux (CHF) by a high speed video observation. In the beginning of transition boiling, coalescing bubbles were collapsed to many fine bubbles and microbubble emission boiling was observed at higher liquid subcooling than 30K. The maximum heat flux obtained was 8MW/m2 (800W/cm2) at liquid subcooling of higher than 40K and the liquid velocity of 0.5m/s. However, the surface temperature was extremely higher than that of centimeter scale channel. The high speed video photographs indicated that microbubble emission boiling occurs in the deep transition boiling region.

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