Theoretically-Based Leidenfrost Point Model

2000 ◽  
Author(s):  
John D. Bernardin ◽  
Issam Mudawar
Keyword(s):  
Bubble Nucleation ◽  
Liquid Gallium ◽  
Interface Temperature ◽  
Sessile Droplet ◽  
Solid Interface ◽  
Leidenfrost Temperature ◽  
Size Characterization ◽  
Surface Cavity ◽  
Effect Of Surface ◽  
Good Agreement

Abstract This study presents a theoretically-based model of the Leidenfrost point (LFP); the minimum liquid/solid interface temperature required to support film boiling on a smooth surface. The model is structured around bubble nucleation, growth, and merging criteria, as well as surface cavity size characterization. It is postulated that for liquid/solid interface temperatures at and above the LFP, a sufficient number of cavities (about 20%) are activated and the bubble growth rates are sufficiently fast that a continuous vapor layer is established nearly instantaneously between the liquid and the solid. The model is applicable to both pools of liquid and sessile droplets. The effect of surface cavity distribution on the LFP predicted by the model is verified for boiling on aluminum, nickel and silver surfaces, as well as on a liquid gallium surface. The model exhibits good agreement with experimental sessile droplet data for water, FC-72, and acetone. While the model was developed for smooth surfaces on which the roughness asperities are of the same magnitude as the cavity radii (0.1–1.0 μm), it is capable of predicting the boundary or limiting Leidenfrost temperature for rougher surfaces with good accuracy.

A Cavity Activation and Bubble Growth Model of the Leidenfrost Point

2002 ◽  
Vol 124 (5) ◽  
pp. 864-874 ◽  
Author(s):  
John D. Bernardin ◽  
Issam Mudawar
Keyword(s):  
Bubble Growth ◽  
Mechanistic Model ◽  
Bubble Nucleation ◽  
Liquid Gallium ◽  
Interface Temperature ◽  
Sessile Droplet ◽  
Solid Interface ◽  
Leidenfrost Temperature ◽  
Size Characterization ◽  
Surface Cavity

This study presents a new mechanistic model of the Leidenfrost point (LFP); the minimum liquid/solid interface temperature required to support film boiling on a smooth surface. The model is structured around bubble nucleation, growth, and merging criteria, as well as surface cavity size characterization. It is postulated that for liquid/solid interface temperatures at and above the LFP, a sufficient number of cavities (about 20 percent) are activated and the bubble growth rates are sufficiently fast that a continuous vapor layer is established nearly instantaneously between the liquid and the solid. The model is applicable to both pools of liquid and sessile droplets. The effect of surface cavity distribution on the LFP predicted by the model is verified for boiling on aluminum, nickel and silver surfaces, as well as on a liquid gallium surface. The model exhibits good agreement with experimental sessile droplet data for water, FC-72, and acetone. While the model was developed for smooth surfaces on which the roughness asperities are of the same magnitude as the cavity radii (0.1–1.0 μm), it is capable of predicting the boundary or limiting Leidenfrost temperature for rougher surfaces with good accuracy.

A Leidenfrost Point Model for Impinging Droplets and Sprays

2004 ◽  
Vol 126 (2) ◽  
pp. 272-278 ◽  
Author(s):  
John D. Bernardin ◽  
Issam Mudawar
Keyword(s):  
Sessile Drop ◽  
Bubble Nucleation ◽  
Interface Temperature ◽  
Solid Interface ◽  
Interfacial Pressure ◽  
Fluid Properties ◽  
Leidenfrost Temperature ◽  
Size Characterization ◽  
The Impact ◽  
Surface Cavity

This study presents, for impinging droplets and sprays, a model of the Leidenfrost point (LFP); the minimum liquid/solid interface temperature required to support film boiling on a smooth surface. The present model is an extension of a previously developed sessile drop model, based on bubble nucleation, growth, and merging criteria, as well as surface cavity size characterization [3]. The basic concept of the model is that for liquid/solid interface temperatures at and above the LFP, a sufficient number of cavities are activated and the bubble growth rates are sufficiently fast that a continuous vapor layer is established nearly instantaneously between the liquid and the solid. For impinging droplets, the influence of the rise in interfacial pressure created by the impact of the droplet with the surface, must be accounted for in determining fluid properties at the liquid-solid interface. The effect of droplet impact velocity on the LFP predicted by the model is verified for single impinging droplets, streams of droplets, as well as sprays. While the model was developed for smooth surfaces on which the roughness asperities are of the same magnitude as the cavity radii (0.1–1.0 μm), it is capable of predicting the boundary or limiting Leidenfrost temperature for rougher surfaces with good accuracy.

Study on Surface Roughness Muring Metal Manufacturing Process

2011 ◽  
Vol 325 ◽  
pp. 731-736
Author(s):  
Zheng Yi Jiang ◽  
Shu Jun Wang ◽  
Dong Bin Wei ◽  
Hei Jie Li ◽  
Hai Bo Xie ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Crack Nucleation ◽  
Metal Plate ◽  
Experimental Result ◽  
Strip Rolling ◽  
Surface Asperity ◽  
Asperity Flattening ◽  
Cold Strip Rolling ◽  
Effect Of Surface ◽  
Good Agreement

In the paper, a crystal plasticity finite element method (CPFEM) model was developed based on ABAQUS to analyse the surface roughness transfer during metal manufacturing. The simulation result shows a good agreement with the experimental result in the flattening of surface asperity, and the surface roughness decreases significantly with an increase of reduction with considering friction effect. Lubrication can delay surface asperity flattening. The effect of surface roughness on produced metal defect (crack) was also studied, and the surface roughness affects the crack initiation significantly in cold strip rolling. In addition, the surface roughness variation along the metal plate width contributes to stress distribution and then inhibition of crack nucleation.

Computation of a Propagating Interface in Multiphase Flows Using an Adaptive Coupled Level Set Method

2002 ◽  
Author(s):  
Ruquan Liang ◽  
Satoru Komori
Keyword(s):  
Surface Tension ◽  
Level Set Method ◽  
Level Set ◽  
Multiphase Flows ◽  
Surface Tension Force ◽  
Numerical Results ◽  
Passive Transport ◽  
Effect Of Surface ◽  
Good Agreement ◽  
Numerical Strategy

We present a numerical strategy for a propagating interface in multiphase flows using a level set method combined with a local mesh adaptative technique. We use the level set method to move the propagating interface in multiphase flows. We also use the local mesh adaptative technique to increase the grid resolution at regions near the propagating interface and additionally at the regions near points of high curvature with a minimum of additional expense. For illustration, we apply the adaptive coupled level set method to a collection of bubbles moving under passive transport. Good agreement has been obtained in the comparision of the numerical results for the collection of bubbles using an adaptative grid with those using a single grid. We also apply the adaptive coupled level set method to a droplet falling on a step where it is important to accurately model the effect of surface tension force and the motion of the free-surface, and the numerical results agree very closely with available data.

Measurement of Ultrafast Melting and Regrowth Velocities in Pulsed Laser Heated Silicon

1983 ◽  
Vol 23 ◽  
Author(s):  
Philip H. Bucksbaum ◽  
Jeffrey Bokor
Keyword(s):  
Laser Fluence ◽  
Pulsed Laser ◽  
Liquid Films ◽  
Heat Diffusion ◽  
Solid Interface ◽  
Direct Measurements ◽  
Laser Heated ◽  
Good Agreement

ABSTRACTDirect measurements of the liquid/solid interface veiocity have been made during both melt-in and regrowth for puised (20 psec) ultraviolet lasei irradiation or crystailine silicon. The regrowth velocity was 25 m/sec, independent or laser fluence. Regrowtn velocities of 50 to 100 m/sec are expected from heat diffusion calculations which neglect undercooling, whereas the inclusion of an appropriate undercooling curve brings the calculation into good agreement with the data. Tne liquid films produced were up to 40 nm thick and were fully amorphized on resoliaificaion.

Effect of Surface Roughness on Nanocontact: Quasicontinuum Simulation

2012 ◽  
Vol 502 ◽  
pp. 342-347 ◽  
Author(s):  
Wu Gui Jiang ◽  
Zheng Wei Wang
Keyword(s):  
Rough Surface ◽  
Smooth Surface ◽  
Characteristic Size ◽  
Contact Forces ◽  
Atomic Scale ◽  
Quasicontinuum Method ◽  
Cu Substrate ◽  
Nonlinear Fashion ◽  
Effect Of Surface ◽  
Good Agreement

By using the two-dimensional quasicontinuum method, the nanocontact between Ni indenter and single crystal Cu substrate with a smooth or rough surface is simulated. The contact force varies in a nonlinear fashion with the increasing indenter displacement, including several force drops. The atomic-scale deformation mechanism in the Cu substrate during nanocontact process is monitored. Shockley partials, Lomer-Cottrel locks as well as twinning faults are observed at the force drops. The Lomer-Cottrel locks play an important role in smooth surface nanocontact process, and they insure that Cu substrate undergoes elastic deformation dominantly during nanocontact process. The contact forces calculated from the Maugis-Dugale (M-D) theory show a good agreement with those obtained by the QC simulation in the smooth surface nanocontact process. It must be noted that the M-D theory is no longer suitable to describe the rough surface nanocontact problem due to the severe plastic deformation in the asperities of the substrate when the characteristic size of roughness is on the order of the indenter depth.

scholarly journals A Multi-scale Contact Temperature Model for Dry Sliding Rough Surfaces

2021 ◽  
Vol 69 (4) ◽  
Author(s):  
Jamal Choudhry ◽  
Andreas Almqvist ◽  
Roland Larsson
Keyword(s):  
Surface Roughness ◽  
Interface Temperature ◽  
Temperature Model ◽  
Flash Temperature ◽  
Wear Model ◽  
Multi Scale ◽  
Proposed Model ◽  
Model Predictions ◽  
Pin On Disc ◽  
Effect Of Surface

AbstractA multi-scale flash temperature model has been developed and validated against existing work. The core strength of the proposed model is that it can be adapted to predict flash contact temperatures occurring in various types of sliding systems. In this paper, it is used to investigate how different surface roughness parameters affect the flash temperatures. The results show that for decreasing Hurst exponents as well as increasing values of the high-frequency cut-off, the maximum flash temperature increases. It was also shown that the effect of surface roughness does not influence the average interface temperature. The model predictions were validated against data from an experiment conducted in a pin-on-disc machine. This also showed the importance of including a wear model when simulating flash temperature development in a sliding system.

An Experimental Study of Magnetic Damping Effect on Temperature Gradient Induced Natural Convection in Liquid Gallium

2004 ◽  
Author(s):  
B. Xu ◽  
B. Q. Li ◽  
D. E. Stock
Keyword(s):  
Magnetic Field ◽  
Natural Convection ◽  
Liquid Gallium ◽  
Horizontal Magnetic Field ◽  
Magnetic Damping ◽  
Damping Effect ◽  
Different Temperatures ◽  
Hot Film ◽  
The Magnetic Field ◽  
Good Agreement

The results of an experimental investigation of natural convection driven flow of liquid gallium are presented. The gallium contained by a rectangular box with two opposite ends held at different temperatures and is subject to a uniform horizontal magnetic field. The objective of this study was to examine the damping effect of a magnetic field on the natural convection in a liquid metal. A hot film anemometry was used to measure the velocity profile and a thermocouple was used to measure the temperature field. The hot-film probe was calibrated over a narrow range of temperatures in a rotating container fill with liquid gallium. The velocity and temperature profiles are compared with previous numerical simulations and reasonably good agreement was found. The damping effect of the external magnetic field was observed in both the temperature and the velocity profiles and found to increase as the strength of the magnetic field increases.

Analytical Investigation on the Homogeneous Nucleation in a Mono-Component and Bi-Component Droplet

2019 ◽  
Author(s):  
Xi Xi ◽  
Hong Liu ◽  
Chang Cai ◽  
Ming Jia ◽  
Weilong Zhang
Keyword(s):  
Nucleation Rate ◽  
Homogeneous Nucleation ◽  
Ambient Pressure ◽  
Analytical Investigation ◽  
Bubble Nucleation ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Liquid Temperature ◽  
Wide Range ◽  
Good Agreement

Abstract The work attempts to analyze the performance of homogeneous nucleation by using the non-equilibrium thermodynamics theory and the classical nucleation theory. A nucleation rate graph was constructed under a wide range of operating temperature conditions. The results indicate that the superheat limit temperature (SLT) estimated by the modified homogeneous nucleation sub-model is in good agreement with the experimental results. The nucleation rate increases exponentially with the liquid temperature rise when the liquid temperature exceeds the SLT under atmospheric pressure. The superheated temperature needed to trigger the bubble nucleation decreases with the elevated ambient pressure.

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