Effect of Pressure on Bubble Growth Within Liquid Droplets at the Superheat Limit

1982 ◽  
Vol 104 (4) ◽  
pp. 750-757 ◽  
Author(s):  
C. T. Avedisian
Keyword(s):  
Vapor Bubble ◽  
Bubble Growth ◽  
High Speed ◽  
Ambient Pressure ◽  
Organic Liquid ◽  
Liquid Droplets ◽  
Growth Data ◽  
Two Phase ◽  
Photographic Evidence ◽  
Good Agreement

A study of high-pressure bubble growth within liquid droplets heated to their limits of superheat is reported. Droplets of an organic liquid (n-octane) were heated in an immiscible nonvolatile field liquid (glycerine) until they began to boil. High-speed cine photography was used for recording the qualitative aspects of boiling intensity and for obtaining some basic bubble growth data which have not been previously reported. The intensity of droplet boiling was found to be strongly dependent on ambient pressure. At atmospheric pressure the droplets boiled in a comparatively violent manner. At higher pressures photographic evidence revealed a two-phase droplet configuration consisting of an expanding vapor bubble beneath which was suspended a pool of the vaporizing liquid. A qualitative theory for growth of the two-phase droplet was based on assuming that heat for vaporizing the volatile liquid was transferred across a thin thermal boundary layer surrounding the vapor bubble. Measured droplet radii were found to be in relatively good agreement with predicted radii.

Analysis of Liquid Slug Motion in a Voided Line

1998 ◽  
Vol 120 (1) ◽  
pp. 74-80 ◽  
Author(s):  
J. Yang ◽  
D. C. Wiggert
Keyword(s):  
Momentum Transfer ◽  
High Speed ◽  
Time History ◽  
Air Entrainment ◽  
Phase Flow ◽  
Liquid Slug ◽  
Two Phase ◽  
Pressure Time ◽  
History Of ◽  
Good Agreement

A quasi-two-dimensional two-phase flow cylindrical model of slug motion in a voided line is developed that can reasonably predict the change of flow pattern of the slug, air entrainment, “holdup” and the distribution of axial velocity. However, when using the theory of incompressible momentum transfer to estimate the pressure-time history of slug at the elbow, the calculated results are not in good agreement with those of the experiments. Further analysis of the experimental results indicate that an acoustic, or waterhammerlike response may occur immediately upon impact of the high-speed slug with the elbow, and subsequently, the waveform exhibits momentum transfer due to the acceleration of the slug at the elbow.

Experimental Measurement of Interfacial Parameters of Elongated Bubbles in Two Phase Gas-Liquid Flow in Horizontal and Slightly Inclined Circular Pipes

2010 ◽  
Author(s):  
J. S. Cunha Filho ◽  
J. L. H. Faccini ◽  
C. A. Lamy ◽  
J. Su
Keyword(s):  
High Speed ◽  
Digital Camera ◽  
Superficial Velocity ◽  
Digital Data ◽  
Visualization Technique ◽  
Two Phase ◽  
Analog Signals ◽  
Circular Pipes ◽  
Gas Liquid Flow ◽  
Good Agreement

This paper reports an experimental study of the measurement of elongated bubbles velocities and their longitudinal shapes using a high speed ultrasonic system in concurrent horizontal and at 5° and 10° inclined upward flow. The circular pipe test section is made of 25.6 mm stainless steel, followed by a transparent acrylic pipe with the same diameter. The high speed ultrasonic system consists of two transducers (10 MHz/6.35 mm diameter), a generator/multiplexer board that convert analog signals into digital data at a rate of 100 million frames per second, and a software that stores all the frames and the results of the time of flight of each signal. The results are compared with a visualization technique that consists of a high-speed digital camera recording images at rates of 125 and 250 frames per second. This range of liquid superficial velocity is from 0.2 to 1.1 m/s and that of the gas superficial velocity is from 0.35 to 1.0 m/s. The results obtained with the two experimental techniques show a good agreement among them for the elongated bubbles lengths and velocities, while having great statistics dispersion. The measured bubble shape is in agreement with literature data.

Experimental and Numerical Investigation of Single Bubble Dynamics in a Two-Phase Bubbly Medium

2011 ◽  
Vol 133 (12) ◽  
Author(s):  
Arvind Jayaprakash ◽  
Sowmitra Singh ◽  
Georges Chahine
Keyword(s):  
Void Fraction ◽  
Compressible Fluid ◽  
High Speed ◽  
Bubble Dynamics ◽  
Ambient Pressure ◽  
Bubble Radius ◽  
Homogeneous Medium ◽  
Two Phase ◽  
Fluid Medium ◽  
Bubbly Medium

The dynamics of a bubble in a dilute bubbly water-air mixture is investigated experimentally and the results compared with a simple homogeneous compressible fluid model in order to elucidate the requirements from a better advanced numerical solution. The experiments are conducted in view of providing input and validation for an advanced bubbly flow numerical model we are developing. Corrections for classical approaches where in the two-phase flow modeling the dynamics of individual bubble is based on spherical isolated bubble dynamics in the liquid or an equivalent homogeneous medium are sought. The main/primary bubble is produced by an underwater spark discharge from charged capacitors, while the bubbly medium is generated using electrolysis. The size of the main bubble is controlled by the discharge voltage, the capacitors size, and the ambient pressure in the container. The size and concentration of the fine bubbles is controlled by the electrolysis voltage, the length, diameter, arrangement, and type of the wires, and also by the pressure imposed in the container. This enables parametric study of the factors controlling the dynamics of the primary bubble and development of relationships between the primary bubble characteristic quantities such as achieved maximum bubble radius and bubble period and the characteristics of the surrounding two-phase medium: micro bubble sizes and void fraction. The dynamics of the main bubble and of the mixture is observed using high speed video photography. The void fraction of the bubbly mixture in the fluid domain is deduced from image analysis of the high speed movies and obtained as a function of time and space. The interaction between the primary bubble and the bubbly medium is analyzed using both field pressure measurements and high-speed videography. Parameters such as the primary bubble energy and the bubble mixture density (void fraction) are varied, and their effects studied. The experimental data is then compared to a simple compressible fluid medium model which accounts for the change in the medium properties in space and time. This helps illustrate where such simple models are valid and where they need improvements. This information is valuable for the parallel development of an Eulerian-Lagrangian code, which accounts for the dynamics of bubbles in the field and their interaction.

Performance of Two-Phase Microchannels at Sub-Atmospheric Pressure

2006 ◽  
Author(s):  
Tao Tong ◽  
Shankar Devasenathipathy ◽  
Je-Young Chang ◽  
John Dirner ◽  
Suzana Prstic ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Atmospheric Pressure ◽  
High Speed ◽  
Flow Boiling ◽  
Ambient Pressure ◽  
Saturation Temperature ◽  
Heat Removal ◽  
Working Fluid ◽  
Cold Plate ◽  
Two Phase

Two-phase microchannel system is a promising technology to achieve enhanced heat removal and more effective cooling of hotspots. The excellent thermodynamic properties of water make it a prime candidate as the working fluid in two-phase microchannel systems. While typical integrated circuit components require die temperature to remain below 95 °C, most of the earlier microchannel flow boiling studies were conducted at or above ambient pressure, where the saturation temperature of water is equal to or higher than 100 °C. In this paper, we tested flow boiling at sub-atmospheric pressure such that the saturation temperature of water can be significantly reduced below 95 °C. We study the pressure drop and heat transfer characteristics of our two-phase cold plate configuration, under uniform and hotspot (non-uniform) heating conditions at sub-atmospheric system pressures. A cold plate with 61 μm wide and 272 μm deep microchannels was tested at two systems pressures of 35 and 46 kPa and at two mass flow rates of 67 and 107 kg/m2-s. High-speed flow imaging was used for identifying flow patterns in the microchannels with the above test conditions. Pressure drop data were compared with the available semi-empirical correlations and the annular flow model. An explanation was proposed for the mismatch between the models under current microchannel configuration.

scholarly journals We -T classification of diesel fuel droplet impact regimes

2018 ◽  
Vol 474 (2215) ◽  
pp. 20170759 ◽  
Author(s):  
Hesamaldin Jadidbonab ◽  
Ilias Malgarinos ◽  
Ioannis Karathanassis ◽  
Nicholas Mitroglou ◽  
Manolis Gavaises
Keyword(s):  
Surface Temperature ◽  
High Speed ◽  
Ambient Pressure ◽  
Dynamic Contact Angle ◽  
Dynamic Contact ◽  
High Speed Imaging ◽  
Two Phase ◽  
Post Impact ◽  
T Classification ◽  
The Impact

A combined experimental and computational investigation of micrometric diesel droplets impacting on a heated aluminium substrate is presented. Dual view high-speed imaging has been employed to visualize the evolution of the impact process at various conditions. The parameters investigated include wall-surface temperature ranging from 140 to 400°C, impact Weber and Reynolds numbers of 19–490 and 141–827, respectively, and ambient pressure of 1 and 2 bar. Six possible post-impact regimes were identified, termed as Stick, Splash, Partial-Rebound, Rebound, Breakup-Rebound and Breakup-Stick , and plotted on the We-T map. Additionally, the temporal variation of the apparent dynamic contact angle and spreading factor have been determined as a function of the impact Weber number and surface temperature. Numerical simulations have also been performed using a two-phase flow model with interface capturing, phase-change and variable physical properties. Increased surface temperature resulted to increased maximum spreading diameter and induced quicker and stronger recoiling behaviour, mostly attributed to the change of liquid viscosity.

scholarly journals Modeling of vapor bubble growth at subatmospheric pressures

2021 ◽  
Vol 2039 (1) ◽  
pp. 012035
Author(s):  
I V Vladyko ◽  
I P Malakhov ◽  
A S Surtaev ◽  
A A Pil’nik ◽  
A A Chernov
Keyword(s):  
Experimental Data ◽  
Analytical Solution ◽  
Growth Model ◽  
Vapor Bubble ◽  
Bubble Growth ◽  
Numerical Calculations ◽  
Superheated Water ◽  
Thermal Growth ◽  
Simulation Results ◽  
Good Agreement

Abstract In this paper, the results of numerical calculations of a vapor bubble growth in superheated water at different pressures are presented. Modeling is based on a previously developed by the authors semi-analytical solution. The results are verified by experimental data obtained at atmospheric and subatmospheric pressures. The presented simulation results and experimental data are in good agreement. The advantage of the solution over the earlier ones (based on the thermal growth model) is shown.

Microscale Heat Transfer Measurements During Subcooled Pool Boiling of Pentane: Effect of Bubble Dynamics

2010 ◽  
Author(s):  
Payam Delgoshaei ◽  
Jungho Kim
Keyword(s):  
Heat Transfer ◽  
Bubble Growth ◽  
High Speed ◽  
Bubble Dynamics ◽  
Pool Boiling ◽  
Growth Time ◽  
Two Phase ◽  
Time Resolved ◽  
Earth Gravity ◽  
Transfer Mechanisms

Measurements of space and time resolved heat transfer during subcooled pool boiling of pentane in earth gravity were obtained using a microscale heater array. Data from individual heater elements in the array were synchronized with bottom and side view images from two high-speed cameras. The heat transfer mechanisms during bubble growth were found to be dependent on bubble dynamics and bubble growth time. Single phase heat transfer mechanisms (transient conduction and/or microconvection) were found to be dominant for single bubbles with short growth times. Two phase heat transfer mechanisms (microlayer evaporation and/or contact line evaporation) were found to be dominant for bubbles with longer growth times.

Experimental Investigation of Nanofluid Flow Boiling in a Single Microchannel

2012 ◽  
Author(s):  
Zachary Edel ◽  
Abhijit Mukherjee
Keyword(s):  
Heat Transfer ◽  
Bubble Growth ◽  
High Speed ◽  
Flow Boiling ◽  
Nucleate Boiling ◽  
Forced Flow ◽  
Nanofluid Flow ◽  
Two Phase ◽  
Nanoparticle Suspension ◽  
Nanoparticle Deposition

The trends of decrease in size and increase in power dissipation for micro-electronic systems present a significant challenge for thermal management of modern electronics. The preferable cooling solution could be micro heat exchangers based on forced flow boiling. Nanoparticle deposition can affect nucleate boiling heat transfer coefficient via alteration of surface thermal conductivity, roughness, capillary wicking, wettability, and nucleation site density. It can also affect heat transfer by changing bubble departure diameter, bubble departure frequency, and the evaporation of the micro and macrolayer beneath the growing bubbles. In this study, flow boiling was investigated for 0.001 vol% aluminum oxide nanofluids in a brass microchannel and compared to results for regular water. For the case of nanofluid flow boiling, high speed images were taken after boiling durations of 25, 75, 125, and 150 min. Bubble growth rates were measured and compared for each case. Flow regime oscillation was observed and regime duration was split into two periods: single-phase liquid and two-phase. The change in regime timing revealed the effect of nanoparticle suspension and deposition on the Onset of Nucelate Boiling (ONB) and the Onset of Bubble Elongation (OBE). The addition of nanoparticles was shown to stabilize bubble growth as well as the transition of flow regimes between liquid, two-phase, and vapor.

Holographic Interferometric Study of Heat Transfer Associated With a Single Vapor Bubble Sliding Along a Downward-Facing Heater Surface

2003 ◽  
Author(s):  
Sathish Manickam ◽  
Vijay Dhir
Keyword(s):  
Heat Transfer ◽  
Vapor Bubble ◽  
High Speed ◽  
Volume Growth ◽  
High Speed Photography ◽  
Heater Surface ◽  
Growth Data ◽  
Volumetric Growth ◽  
Experimental Conditions ◽  
Fringe Patterns

Heat transfer associated with a single vapor bubble sliding along a downward-facing heater surface was studied experimentally to understand the mechanisms contributing to heat transfer enhancement. Heater surface was made of polished silicon wafer of length 185 mm and width 49.5 mm. Saturated and subcooled performance fluid PF 5060 at atmospheric pressure was used as the test liquid. The heater surface was at 75° inclination to the vertical for the experiments reported here. Single vapor bubbles were generated at an artificially formed cavity at the bottom end of the heater surface. Holographic interferometry was used to obtain the temperature profile around the bubble as it slides along the heater surface near the top end of the heater plate. From the fringe patterns, the temperature gradient around the bubble interface was measured and heat transfer into or out of the bubble was computed. In addition to these experiments, the volumetric growth of the vapor bubble as it slides along the heater surface was obtained using direct high-speed photography for the same experimental conditions. Heat transfer from the wall was estimated utilizing inputs from both interferometry studies as well as the volume growth data. Results are given for a range of liquid subcoolings and wall superheats, and are compared with previously published works.

Sign in / Sign up

Export Citation Format

Share Document