Bubble Nucleation Temperature Research Articles

Acoustically controlled bubble nucleation

Fundamental studies of single bubble heat transfer are crucial to improve our understanding of boiling phenomena and develop modeling and simulation tools for the design and optimization of boiling systems. However, conducting these kinds of experiments over a wide range of conditions is challenging and may involve expensive and complicated experimental techniques (e.g., lasers) to isolate and control bubble nucleation. In this work, we introduce a new technique to control nucleation with an ultrasonic beam. A low-cost and widely available piezoelectric disc driven at megahertz frequencies directed at a heated surface can increase the time-averaged pressure and suppress evaporation until the moment the transducer is turned off, allowing us to control the incipience of boiling to within 150 µs. We demonstrate this technique by measuring the physical and thermal footprint of natural and acoustically controlled bubbles with high-resolution infrared thermometry and phase detection diagnostics. We were able to raise the bubble nucleation temperature by over 30 K compared to a reference case with no acoustic control, which significantly changes bubble growth rate, microlayer formation and evaporation and departure diameter. We highlight the potential of this new low-cost and easy-to-use technique in a variety of different boiling heat transfer studies.

Experimental and molecular dynamics study on micro-explosion of water-in-diesel droplets in the presence of solid nanoparticles

In recent years, multicomponent fuels have been widely studied; among them, dual fuels with different boiling points have attracted attention because of the micro-explosion phenomenon, which makes the mixing and combustion of diesel and air more complete. Strengthening the micro-explosion processes and further improving the degree of mixing of diesel and air is one of the core problems of micro-explosions. This study conducted experiments and molecular dynamics simulation to investigate this problem by adding nanoparticles to emulsified water-in-diesel droplets. First, the concept of puffing was proposed to describe the time and difficulties of bubble nucleation. Second, frequency distributions of a single micro-explosion intensity were proposed, and S-n diagrams comprising the cumulative micro-explosion intensity and total micro-explosion frequency were used to describe the micro-explosion intensity comprehensively. The results show that nanoparticles promote heat transfer between the droplets and high-temperature environments. Moreover, it weakens the potential energy between liquid water molecules and generates bubble nuclei around the nanoparticles, decreasing the bubble nucleation temperature and time and increasing bubble occurrence probability. Furthermore, the micro-explosion mode gradually shifts from low frequency (intensity) to medium frequency (intensity) with increasing carbon nanoparticle concentration.

Nucleation at Finite Temperature: A Gauge-Invariant Perturbative Framework.

We present a gauge-invariant framework for bubble nucleation in theories with radiative symmetry breaking at high temperature. As a procedure, this perturbative framework establishes a practical, gauge-invariant computation of the leading order nucleation rate, based on a consistent power counting in the high-temperature expansion. In model building and particle phenomenology, this framework has applications such as the computation of the bubble nucleation temperature and the rate for electroweak baryogenesis and gravitational wave signals from cosmic phase transitions.

Boiling heat transfer of CO2/lubricant on structured surfaces using molecular dynamics simulations

In this paper, the molecular dynamics (MD) simulations are employed to investigate the effects of lubricant (PEC4) on the boiling heat transfer of CO2 on the structured surface. The results show that the structured surfaces can enhance the nucleation boiling of CO2 by providing effective bubble nucleation sites and larger heat transfer areas. However, with the increase of the mass fraction of PEC4, the nucleation boiling heat transfer efficiency decreases on the structured surface. The distribution characteristics of the CO2/PEC4 mixture during the boiling process show that parts of CO2 molecules in the liquid mixture are more likely to be adsorbed by the double-bonded oxygen atoms and carbon atoms of the ester groups of the PEC4 molecules, which hinders the movement and phase transition process of CO2 molecules. Therefore, the PEC4 molecules in the nucleation region first migrate to the top liquid region before bubble nucleation, and then bubble nuclei comes into being. When the mass fraction of PEC4 is higher than 7 wt%, the nucleation temperature is increased by 10 K to 20 K. The decrease of the CO2 nucleation boiling heat transfer performance caused by PEC4 istheconsequenceof thecoaction ofmanyfactors, including that the lubricant leads to a decrease in self-diffusion coefficient of CO2, an increase in liquid phase viscosity, an increase in bubble nucleation temperature of CO2, and a decrease in heat transfer resistance of the solid-liquid interface.

Boiling heat transfer enhancement on titanium through nucleation-promoting morphology and tailored wettability

• Cavity- and spear-type TiO 2 nanostructures are prepared by hydrothermal treatment. • Nucleation-promoting cavity morphology is superior to spear-like microstructure. • Hydrophobic surface with microcavities (CTH) provides HTC enhancement of over 200%. • High nucleation site density on CHT surface narrows surface temperature distribution. • ONB at 2.5 K and D b of 0.55 mm are observed on hydrophobic microcavity surface. Surface engineering aimed at tuning the wettability and morphology of the boiling surface is a facile approach to moderate and enhance the nucleate boiling process. Key issues include control over the active nucleation site density, bubble departure frequency and liquid replenishment of active nucleation sites while simultaneously reducing the bubble nucleation temperature. In this study, we fabricated spear-type (ST) and cavity-type (CT) TiO 2 nanostructures on 25 μm titanium foils via hydrothermal etching in an alkaline solution. High-speed IR and video cameras were used to detect local phenomena in terms of temperature and heat flux fluctuations and observe the bubble dynamics during saturated pool boiling of water. Intrinsically hydrophilic ST and CT surfaces provided a moderate overall enhancement of the heat transfer coefficient compared to an untreated surface due to increased nucleation site density and bubble frequency. The CT surface also decreased the bubble nucleation temperature due to effective vapor-entrapping and nucleation-promoting cavities. In a further step, both surfaces were hydrophobized through chemical vapor deposition of a fluorinated silane to tailor the wettability of the surface into a superhydrophobic state. This further reduced the average surface superheat by at least 40%, while the nucleation frequencies exceeded 200 Hz on the hydrophobized CT surface. In comparison with the untreated reference surface, the heat transfer coefficient on hydrophobized ST and CT surfaces was enhanced by 89% and 237% at 100 kW m −2 , respectively. Moreover, the full width at half maximum (FWHM) value of the surface temperature distribution was reduced by 73% and 95% at the same heat flux, respectively. The study confirms that hydrophobic surface treatment can significantly enhance the nucleate boiling process when combined with an appropriate surface structure. Despite the affinity between the vapor and the hydrophobic layer, the cavity-type and spear-type TiO 2 structures are able to maintain active nucleation sites well-separated, which prevents the undesirable vapor spreading that possibly leads to an early onset of critical heat flux.

Molecular dynamics simulation on micro-explosion of water-in-oil droplets in presence of solid particles or electric field

The effects of solid particles or external electric field on the whole micro-explosions, especially bubble nucleation, were explored by molecular dynamics simulation. The corresponding reasons are also revealed. For this purpose, a water-in-oil droplet in nitrogen environment were constructed and the whole micro-explosion processes were simulated. Bubble nucleation time and nucleation temperature were estimated and compared with the cases in presence of solid particles or an electric field. The energy, force and coordination number of the water sub-droplet were explored to clarify the effects of the solid particles or an electric field. Results indicate that the presence of solid particles or an electric field can shorten the nucleation time and lower nucleation temperature, which are effective ways to control the micro-explosion process. Adding solid particles can weaken the potential restriction on water molecules, which much facilitates water molecules evaporations, and the effect is positive correlation with solid particle sizes. The effect of an external electric field on micro-explosion is essentially caused by the reduction of electrostatic potential. In the alternating electric field case, the reason for the faster temperature rise and the shorter nucleation time is that the sinusoidal change of the electrostatic force.

Laser texturing of silicon surface to enhance nucleate pool boiling heat transfer

• The laser texturing technique is used to modify the silicon-based heat exchange surface. • Modified surface is characterized by superhydrophilic properties and high stability. • The laser-textured surface demonstrates the heat transfer enhancement during water pool boiling. • The surface modification leads to the considerable change in the dynamics of vapor bubbles. The surface modification is one of the most promising and discussed methods to improve the boiling performance. To date there are a lot of techniques to modify a heating surface, but the search for the optimal, simple and reliable one is still an actual problem. Recently, the surface texturing using laser ablation was applied in a number of studies, which showed its great potential for heat transfer enhancement and critical heat fluxes increase during pool boiling on the metal surfaces. In this paper, we modified a silicon surface by laser texturing and analyzed its effect on the heat transfer and bubble dynamics during water pool boiling using high-speed thermography and video recording. The experiments showed that the usage of laser-textured surface results in the heat transfer enhancement up to 49.5% compared to the reference rough silicon sample and up to 234% compared to the polished sample. Moreover, the modified surface is characterized with lower onset of nucleate boiling and lower bubble nucleation temperature. Dataset on the major characteristics of bubbles dynamics during boiling on the untreated and laser-textured surfaces was obtained using the high-speed video recording. Its analysis showed that the laser treatment leads to the significant increase in the nucleation site density and nucleation frequency, while the bubble departure diameter value dramatically decreases compared to the reference surface. On the basis of experimental data the relationship between nucleation frequency and departure diameter was found and analyzed both for untreated surface and for laser-textured one.

Numerical modelling and investigation of microwave heating and boiling phenomena in binary liquid mixtures using OpenFOAM

To understand Microwave (MW) heating and boiling of binary liquid mixtures, a new multiphysics model was developed. The new model solves Maxwell's equations for the electromagnetic field distribution. Concerning the coupled dispersed and segregated vapor-liquid flow during MW boiling, it was modelled based on a hybrid Two-Fluid-Volume-of-Fluid method. As for the modelling of heat and mass transfer, Two-fluid energy and species conservation equations were solved, with new dispersed and segregated interphase heat and mass transfer closures formulated using appropriate interface jump conditions combined with vapor-liquid equilibrium relations. The new model showed reasonably good agreement with the experimental data. The capability of the model to simulate MW heating, superheating, superboiling, and interphase transfer phenomena in methanol-water mixture (heated in a multi-mode MW cavity) was demonstrated, and the associated physics was investigated. The simulation results revealed three underlying mechanisms that lead to superheating (up to 9.5°C at 300 W) in binary mixtures, namely limited bubble nucleation, inefficient mixing, and higher interfacial saturation temperature compared to that in bulk liquid (about 2°Chigher). Besides, the results also showed that the increase of heating time mainly increases the amount of superheat rather than the superheat temperature. It was also found that MW superheating tends to reduce the mass fraction of the lighter component in the released vapor (by up to 2%). In the subsequent study, the effects of several operating conditions were examined. The simulation results generally showed that higher liquid methanol concentration, higher MW power, rectangular sample geometry, and smaller sample volume lead to higher superheat intensity, but poorer methanol concentration in the vapor released. The new model and findings could open up new avenues for the design and improvement of processes such as MW-assisted synthesis, extraction, biodiesel production, and distillation.

Dynamics of Electroweak Phase Transition in the 3-3-1-1 Model

The bubble nucleation in the framework of 3-3-1-1 model is studied. Previous studies show that first order electroweak phase transition occurs in two periods. In this paper we evaluate the bubble nucleation temperature throughout the parameter space. Using the stringent condition for bubble nucleation formation we find that in the first period, symmetry breaking from \(SU(3)\rightarrow SU(2)\), the bubble is formed at the nucleation temperature $T=150$ GeV and the lower bound of the scalar mass is 600 GeV. In the second period, symmetry breaking from \((SU(2)\rightarrow U(1)\), only subcritical bubbles are formed. This constraint eliminates the electroweak baryon genesis in the second period of the model.

Mapping the shape of the scalar potential with gravitational waves

We study the dependence of the observable stochastic gravitational wave background induced by a first-order phase transition on the global properties of the scalar effective potential in particle physics. The scalar potential can be that of the Standard Model Higgs field, or more generally of any scalar field responsible for a spontaneous symmetry breaking in beyond-the-Standard-Model settings that provide for a first-order phase transition in the early universe. Characteristics of the effective potential include the relative depth of the true minimum [Formula: see text], the height of the barrier that separates it from the false one [Formula: see text] and the separation between the two minima in field space [Formula: see text], all at the bubble nucleation temperature. We focus on a simple yet quite general class of single-field polynomial potentials, with parameters being varied over several orders of magnitude. It is then shown that gravitational wave observatories such as aLIGO O5, BBO, DECIGO and LISA are mostly sensitive to values of these parameters in the region [Formula: see text]. Finally, relying on well-defined models and using our framework, we demonstrate how to obtain the gravitational wave spectra for potentials of various shapes without necessarily relying on dedicated software packages.

Plasmonic Bubble Nucleation and Growth in Water: Effect of Dissolved Air.

Under continuous laser irradiation, noble metal nanoparticles immersed in water can quickly heat up, leading to the nucleation of so-called plasmonic bubbles. In this work, we want to further understand the bubble nucleation and growth mechanism. In particular, we quantitatively study the effect of the amount of dissolved air on the bubble nucleation and growth dynamics, both for the initial giant bubble, which forms shortly after switching on the laser and is mainly composed of vapor, and for the final life phase of the bubble, during which it mainly contains air expelled from water. We found that the bubble nucleation temperature depends on the gas concentration: the higher the gas concentration, the lower the bubble nucleation temperature. Also, the long-term diffusion-dominated bubble growth is governed by the gas concentration. The radius of the bubbles grows as R(t) ∝ t1/3 for air-equilibrated and air-oversaturated water. In contrast, in partially degassed water, the growth is much slower since, even for the highest temperature we achieve, the water remains undersaturated.

Bubble nucleation over patterned surfaces with different wettabilities: Molecular dynamics investigation

The bubble nucleation of liquid argon over patterned surfaces with different wettabilities is investigated by using molecular dynamics (MD) simulations. In order to study effects of different wall temperatures on bubble nucleation process, bubble nucleation positions and bubble dynamics behaviors are observed. Simulation results show that at low wall temperatures bubble nucleation tends to occur over the hydrophobic part of the wall. With increasing wall temperature, the bubble nucleus gradually changes its position from the hydrophobic to hydrophilic part. When the wall temperature increases to a certain value, bubble nuclei first appear on both the hydrophobic and hydrophilic parts. By analyzing heat flux and change trend of argon state points, differences in bubble nucleation process at different wall temperatures are explained. Moreover, the effect of area fraction of hydrophobic part on bubble nucleation temperature is investigated. It is found that there exists an optimal area fraction which makes the bubble nucleation temperature the lowest.

Giant and explosive plasmonic bubbles by delayed nucleation

When illuminated by a laser, plasmonic nanoparticles immersed in water can very quickly and strongly heat up, leading to the nucleation of so-called plasmonic vapor bubbles. While the long-time behavior of such bubbles has been well-studied, here, using ultrahigh-speed imaging, we reveal the nucleation and early life phase of these bubbles. After some delay time from the beginning of the illumination, a giant bubble explosively grows, and collapses again within 200 μs (bubble life phase 1). The maximal bubble volume [Formula: see text] remarkably increases with decreasing laser power, leading to less total dumped energy E. This dumped energy shows a universal linear scaling relation with [Formula: see text], irrespective of the gas concentration of the surrounding water. This finding supports that the initial giant bubble is a pure vapor bubble. In contrast, the delay time does depend on the gas concentration of the water, as gas pockets in the water facilitate an earlier vapor bubble nucleation, which leads to smaller delay times and lower bubble nucleation temperatures. After the collapse of the initial giant bubbles, first, much smaller oscillating bubbles form out of the remaining gas nuclei (bubble life phase 2). Subsequently, the known vaporization dominated growth phase takes over, and the bubble stabilizes (life phase 3). In the final life phase 4, the bubble slowly grows by gas expelling due to heating of the surrounding. Our findings on the explosive growth and collapse during the early life phase of a plasmonic vapor bubble have strong bearings on possible applications of such bubbles.

Dynamics of electroweak phase transition in singlet-scalar extension of the standard model

An addition to the Standard Model of a real, gauge-singlet scalar field, coupled via a Higgs portal interaction, can reopen the possibility of a strongly first-order electroweak phase transition (EWPT) and successful electroweak baryogenesis (EWBG). If a discrete symmetry that forbids doublet-singlet mixing is present, this model is notoriously difficult to test at the Large Hadron Collider. As a result, it emerged as a useful benchmark for evaluating the capabilities of proposed future colliders to conclusively test EWPT and EWBG. In this paper, we evaluate the bubble nucleation temperature throughout the parameter space of this model where a first-order transition is expected. We find that in large parts of this parameter space, bubbles in fact do not nucleate at any finite temperature, eliminating these models as viable EWBG scenarios. This constraint eliminates most of the region where a "two-step" phase transition is naively predicted, while the "one-step" transition region is largely unaffected. In addition, expanding bubble walls must not reach relativistic speeds during the transition for baryon asymmetry to be generated. We show that this condition further reduces the parameter space with viable EWBG.

Rapid evaporation at the superheat limit of methanol, ethanol, butanol and n-heptane on platinum films supported by low-stress SiN membranes

The bubble nucleation temperatures of several organic liquids (methanol, ethanol, butanol, n-heptane) on stress-minimized platinum (Pt) films supported by SiN membranes is examined by pulse-heating the membranes for times ranging from 1μs to 10μs. The results show that the nucleation temperatures increase as the heating rates of the Pt films increase. Measured nucleation temperatures approach predicted superheat limits for the smallest pulse times which correspond to heating rates over 108K/s, while nucleation temperatures are significantly lower for the longest pulse times. The microheater membranes were found to be robust for millions of pulse cycles, which suggests their potential in applications for moving fluids on the microscale and for more fundamental studies of phase transitions of metastable liquids.

Method of examination of bubble nucleation in glass melts

The method of high temperature monitoring and image analysis was applied to determine the temperature at which the bubbles were nucleated on a platinum wire immersed in the melt of a float type of glass. The bubbles that rose during a slow increase of temperature were identified, monitored and subsequently, their diameter was measured and the obtained dependence between the bubble diameter and time was extrapolated to the zero size of the relevant bubbles. The bubble nucleation temperature has been determined at the temperature of bubble zero size. The obtained average value of the bubble nucleation temperature in glass with 0.185wt.% of chemically dissolved SO3 was 1502.6°C whereas the same quantity showed the value in glass with 0.250wt.% of chemically dissolved SO3 to be 1501.4°C. The intensity of bubble nucleation in the form of the number of nucleated bubbles and the volume of released gas versus time were also measured in both glass samples and described by a theoretical equation. The relation between the diffusion and thermodynamic barriers of the nucleation was determined and discussed. The results were also discussed with respect to the literature data relating to the bubble nucleation and the fining process.

Measurement of the bubble nucleation temperature of water on a pulse-heated thin platinum film supported by a membrane using a low-noise bridge circuit

Abstract This study describes the performance of stress-minimized platinum (Pt) films supported by thin membranes (200 nm thick) to promote bubble nucleation of water near its theoretical superheat limit. The membrane configurations consist of Pt films deposited on 200 nm thick SiN films over bulk Si, with membranes being formed by etching Si from the back side of the films. Results are compared with more conventional Pt films supported by SiO2 and Si substrates. The average metal temperature is monitored by a bridge circuit with capacitive and inductive filtering to reduce noise in the output signal. Voltage pulses with durations ranging between 0.5 and 10 μs are imposed on the bridge to electrically heat the Pt film. The paper includes discussion of fabrication of the films, their treatment prior to using them as temperature sensors, the bridge circuit design for monitoring the change in electrical resistance during the power pulse, the calibration process of the films, and results of the bubble nucleation temperatures for the range of pulse durations examined. The results show that significantly less power is needed to trigger bubble nucleation on a membrane-supported platinum film compared to a platinum film on a bulk Si substrate. The nucleation temperatures which were closest to the theoretical limit of water were realized at heating rates of nearly 109 C/s. The potential for employing back-side etched devices is suggested for fundamental studies of phase transitions of highly superheated liquids and in applications where bubble nucleation is an important process such as for ink-jet printers and microscale bubble pump concepts.

Molecular Dynamics Studies of Homogeneous and Heterogeneous Thermal Bubble Nucleation

Thermal bubble nucleation was studied using molecular dynamics for both homogeneous and heterogeneous argon systems using isothermal-isobaric (NPT) and isothermal-isostress (NPzzT) ensembles. Unlike results using NVE and NVT ensembles, no stable nanoscale bubble exists in the NPT ensembles, but instead, the whole system changes into vapor phase. In homogeneous binary systems, reducing the interaction strength between alien atoms and argon atoms significantly decreases the nucleation temperature; however, enhancing the interaction strength only increases the nucleation temperature marginally. For nanoconfined heterogeneous NPzzT ensembles with liquid argon between two solid plates, the nucleation temperature increases as the channel height decreases if the channel height is less than ∼7.63 nm. More interestingly, in this regime, the bubble nucleation temperature could be significantly higher than the corresponding homogeneous nucleation temperature. This observation is different from the common expectation that homogeneous thermal bubble nucleation, as a result of fundamental thermodynamic instability, sets an upper limit for thermal bubble nucleation temperature under a given pressure. However, the result can be understood physically based on the more ordered arrangement of atoms, which corresponds to a higher potential energy barrier.

Bubble nucleation, growth and surface temperature oscillations on a rapidly heated microscale surface immersed in a bulk subcooled but locally superheated liquid under partial vacuum

The effect of ambient pressures below atmospheric, liquid subcooling and heating rate on bubble dynamics associated with rapid evaporation in highly superheated water is investigated. Platinum films of various aspect ratios are electrically heated under partial vacuum and the average metal film temperature monitored during a power pulse of duration of several tens of microseconds. At high liquid subcooling, the surface temperature of the pulse-heated thin platinum strips is shown to oscillate with a frequency on the order of 0.5 MHz. The oscillation frequency increases with ambient pressure in the range 0.02 MPa and 0.101 MPa, and decreases with increasing ambient temperature at a fixed pressure. An unusual dynamic instability is observed in which the surface temperature is constant before relaxing into oscillations, and the delay to oscillations increases with decreasing pressure. High speed imaging shows that the bubble growth phase of the oscillation is associated with surface heating and the collapse phase with surface cooling in the cyclic temperature history. These effects are explained by a bubble growth theory that includes a heat loss mechanism to the surrounding liquid. The nucleation temperature is unaffected by pressure in the sub-atmospheric range examined and it approaches the theoretical superheat limit for water at a heating rate of about 10 9 °C/s.

Microscopic explosive boiling induced by a pulsed-laser irradiation

This paper presents an experimental study of microscopic explosive boiling introduced by a pulsed laser. The violent explosive boiling was observed in the liquid film, and the vapor bubbles together with liquid droplets were expelled from the platinum film. It is found that the apparent bubble nucleation temperature is a strong function of the heating rate. The pressure signal appears as continuous oscillation and is intensified as laser power density increases.