Nucleation Kinetics for Boiling in Microstructures

2005 ◽  
Author(s):  
J. F. Lu ◽  
X. F. Peng ◽  
B. Bourouga
Keyword(s):  
Kinetic Equation ◽  
Dynamic Characteristics ◽  
Nucleation Rate ◽  
Critical Radius ◽  
Momentum Conservation ◽  
Bubble Nucleation ◽  
Nucleation Process ◽  
Nucleation Kinetics ◽  
Bubble Evolution ◽  
Two Stages

Theoretical investigation is conducted to understand the bubble nucleation process in microstructures. The bubble evolution in microstructures is investigated for momentum conservation, and the evolution rate is deeply dependent on the structure. According to different dynamic characteristics in the region close to the critical radius, the nucleation process is divided into two stages. Based on the characteristics of these two stages, a nucleation kinetic equation is modified from classical theory and then is conducted to understand the special bubble nucleation process. The result concludes that the nucleation rate will be deduced if bubble evolution is restrained in microstructures.

scholarly journals Secondary Nucleation Kinetics of AIBN Crystallisation in Methanol: Online Imaging-Based Measurement and Modelling

Crystals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 506
Author(s):  
Yang Li ◽  
Yang Zhang ◽  
Xue Zhong Wang
Keyword(s):  
Nucleation Rate ◽  
Induction Time ◽  
Nucleation Process ◽  
Stirrer Speed ◽  
Seed Number ◽  
Nucleation Kinetics ◽  
Secondary Nucleation ◽  
On Line ◽  
Small Change ◽  
Crystal Seed

The secondary nucleation process of 2,2-azobisisobutyronitrile (AIBN) seeded crystallisation in methanol in a stirred tank reactor was studied at varying initial supersaturation levels, temperatures, crystal seed numbers, and stirrer speeds. The average secondary nucleation rate, induction time, and agglomeration ratio were measured using on-line microscopic imaging. The initial supersaturation level, temperature, and stirrer speed were found to be positively correlated with the secondary nucleation rate. A small change in the crystal seed number, i.e., 1-20, did not substantially affect the secondary nucleation rate throughout the secondary nucleation process. An increase in the initial supersaturation level and crystal seed number decreased the induction time, and an increase in the strength of agitation promoted the initiation of secondary nucleation at a stirring rate greater than 250 revolutions per minute (rpm). Temperature exerted a complex effect on the induction time. Regarding the agglomeration ratio, the initial supersaturation level positively correlated with the agglomeration ratio, while the stirrer speed negatively correlated with this parameter. Finally, based on the measured data, the average secondary nucleation rate, induction time, and final crystal suspension density were correlated. This study provides guidance for the control of supersaturation, induction time, stirring, and other factors in the crystal seed addition process in AIBN crystallisation.

scholarly journals Electric-Potential-Assisted Crystallisation of L-Isoleucine: A Study of Nucleation Kinetics and Its Associated Parameters

Crystals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 620
Author(s):  
Nik Salwani Md Azmi ◽  
Nornizar Anuar ◽  
Muhamad Fitri Othman ◽  
Noor Fitrah Abu Bakar ◽  
Mohd Nazli Naim
Keyword(s):  
Nucleation Rate ◽  
Electric Potential ◽  
Critical Radius ◽  
Dynamics Simulation ◽  
Nucleation Kinetics ◽  
Electric Potentials ◽  
Temperature Controlled ◽  
Isothermal Crystallisation ◽  
Kinetics Of ◽  
Good Agreement

The potential of producing L-isoleucine crystals with the aid of electric potential and its effect on the nucleation kinetics of L-isoleucine were probed using polythermal and isothermal crystallisation techniques, assisted with 5 V, 9 V, and 20 V electric potentials. The polythermal experiments were conducted with cooling rates of 0.1 °C/min–0.7 °C/min, whilst isothermal crystallisation was conducted with a supersaturation of 1.30–1.70, and both were carried out in a 200 mL temperature-controlled jacketed reactor. Prediction of the nucleation rate and its associated parameters for isothermal crystallisation was carried out using a molecular dynamics simulation. In both crystallisation techniques, electric potentials increased the nucleation rate, but the intensity of the electric potential had less impact on the measured parameters. Nucleation rates for 5 V isothermal crystallisation were in the order of 1010 higher than for polythermal crystallisation. Electric potential doubled the nucleation rates for polythermal crystallisation and increased the nucleation rates 12-fold in isothermal crystallisation. The isothermal technique produced the form B polymorph, but mixtures of forms A and B were produced in polythermal crystallisation. The predicted critical number of molecules, N*, and the critical radius, r*, were in good agreement with the experimental data, with a higher predicted nucleation rate in the order of 102.

Bubble Nucleation on Micro Line Heaters

2003 ◽  
Vol 125 (4) ◽  
pp. 687-692 ◽  
Author(s):  
Jung-Yeop Lee ◽  
Hong-Chul Park ◽  
Jung-Yeul Jung ◽  
Ho-Young Kwak
Keyword(s):  
Contact Angle ◽  
Free Surface ◽  
Cluster Model ◽  
Bubble Nucleation ◽  
Nucleation Temperature ◽  
Molecular Cluster ◽  
Resistance Characteristic ◽  
Nucleation Process ◽  
Superheat Limit ◽  
Current Resistance

Nucleation temperatures on micro line heaters were measured precisely by obtaining the I-R (current-resistance) characteristic curves of the heaters. The bubble nucleation temperature on the heater with 3 μm width is higher than the superheat limit, while the temperature on the heater with broader width of 5 μm is considerably less than the superheat limit. The nucleation temperatures were also estimated by using the molecular cluster model for bubble nucleation on the cavity free surface with effect of contact angle. The bubble nucleation process was observed by microscope/35 mm camera unit with a flash light of μs duration.

scholarly journals Measuring the activation energy barrier for the nucleation of single nanosized vapor bubbles

2019 ◽  
Vol 116 (26) ◽  
pp. 12678-12683 ◽  
Author(s):  
Jing Chen ◽  
Kai Zhou ◽  
Yongjie Wang ◽  
Jia Gao ◽  
Tinglian Yuan ◽  
...  
Keyword(s):  
Activation Energy ◽  
Rate Constant ◽  
Nucleation Rate ◽  
Energy Barrier ◽  
Bubble Nucleation ◽  
Vapor Bubbles ◽  
Activation Energy Barrier ◽  
Facet Structure ◽  
Optical Images ◽  
Local Activation Energy

Heterogeneous bubble nucleation is one of the most fundamental interfacial processes that has received broad interest from diverse fields of physics and chemistry. While most studies focused on large microbubbles, here we employed a surface plasmon resonance microscopy to measure the nucleation rate constant and activation energy barrier of single nanosized embryo vapor bubbles upon heating a flat gold film with a focused laser beam. Image analysis allowed for simultaneously determining the local temperature and local nucleation rate constant from the same batch of optical images. By analyzing the dependence of nucleation rate constant on temperature, we were able to calculate the local activation energy barrier within a submicrometer spot. Scanning the substrate further led to a nucleation rate map with a spatial resolution of 100 nm, which revealed no correlation with the local roughness. These results indicate that facet structure and surface chemistry, rather than geometrical roughness, regulated the activation energy barrier for heterogeneous nucleation of embryo nanobubbles.

Gas bubble nucleation kinetics in a live heavy oil

2001 ◽  
Vol 192 (1-3) ◽  
pp. 25-38 ◽  
Author(s):  
D.A. Lillico ◽  
A.J. Babchin ◽  
W.E. Jossy ◽  
R.P. Sawatzky ◽  
J.-Y. Yuan
Keyword(s):  
Heavy Oil ◽  
Bubble Nucleation ◽  
Gas Bubble ◽  
Nucleation Kinetics

scholarly journals Effect of Propane and NaCl-SDS Solution on Nucleation Process of Mine Gas Hydrate

2017 ◽  
Vol 2017 ◽  
pp. 1-12 ◽  
Author(s):  
Qiang Zhang ◽  
Qiang Wu ◽  
Hui Zhang
Keyword(s):  
Gas Hydrate ◽  
Induction Time ◽  
Equilibrium Points ◽  
Sodium Dodecyl ◽  
Hydrate Formation ◽  
Nucleation Process ◽  
Nucleation Kinetics ◽  
Gas Hydrate Formation ◽  
Experimental Apparatus ◽  
Mine Gas

In order to explore the method of accelerating hydration separation process to recover methane from mine gas, propane hydrate phase equilibrium was used to measure the equilibrium points of three kinds of mine gas in NaCl solution. Driving force was set as 1 MPa on this basis and high-pressure experimental apparatus of mine gas hydrate was used to carry out the nucleation kinetics experiments of mine gas hydrate for three gas samples in different concentrations of sodium chloride (NaCl) and sodium dodecyl sulfate (SDS) compound systems, which was to study the effect of propane and NaCl-SDS solution on nucleation process of mine gas hydrate. The results showed that induction time of multicomponent mine gas hydrate formation was shortened with the decrease of methane concentration and increase of propane concentration. The induction time of mine gas hydrate formation was shortened with the reduction of NaCl concentration and the increase of SDS concentration. It was found that methane and propane in multicomponent mine gas nucleated collaboratively, which simplified its nucleation process compared with the single component. NaCl has two kinds of functions.

scholarly journals Monitoramento da cristalização da lactose em soro concentrado

2017 ◽  
Vol 72 (4) ◽  
pp. 215-226
Author(s):  
Ítalo Tuler Perrone ◽  
João Pablo Fortes Pereira ◽  
Isis Rodrigues Toledo Renhe ◽  
Júlia D’Almeida Francisquini ◽  
Rodrigo Stephani ◽  
...  
Keyword(s):  
Crystal Growth ◽  
Soluble Solids ◽  
Nucleation Process ◽  
Secondary Nucleation ◽  
Primary Nucleation ◽  
Industrial Setting ◽  
Mathematical Equations ◽  
Average Size ◽  
Two Stages ◽  
Kinetics Of

The kinetics of lactose crystal growth in concentrated whey were studied in two stages. The first took place in a bench-top crystallizer and the second in an industrial crystallizer using concentrated whey obtained by vacuum evaporation, consisting of 3 treatments: crystallization by primary nucleation, by secondary nucleation with the addition of 0.05% and with the addition of 0.1% microcrystalline lactose. The average size of the crystals remained between 60.7 mm and 63.8 mm. The percentage of crystallization was greater in the secondary nucleation process than in the primary nucleation, where crystallization stabilized first. Mathematical equations which independently related crystallization times of the concentrated whey to the concentrations of soluble solids, crystallization percentage and mass of lactose in water were established, that can be used in the industrial setting to process whey. The kinetics of lactose crystal growth was not well described by models of first or second order reactions.

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