Numerical Simulation of Water Droplet Freezing Process on Cold Surface

2017 ◽  
Author(s):  
Yina Yao ◽  
Cong Li ◽  
Zhenxiang Tao ◽  
Rui Yang
Keyword(s):  
Contact Angle ◽  
Numerical Model ◽  
Phase Change ◽  
Empirical Relation ◽  
Three Dimensional ◽  
Freezing Process ◽  
Freezing Time ◽  
Water Droplets ◽  
Cold Surface ◽  
Extended Phase

It is significant to clearly understand the freezing process of water droplets on a cold substrate for the prevention of ice accretion. In this study, a three-dimensional numerical model including an extended phase change method was developed on OpenFOAM platform to simulate the freezing of static water droplets on cooled solid substrates. The predicted freezing process was compared with numerical results obtained by others. Good agreements were obtained and our numerical model results in faster convergence compared to the traditional phase change method. The effects of surface wettability on freezing time and freezing velocity were numerically investigated. The results show that the freezing time presents a positive relationship with contact angle due to the smaller contact area with higher contact angle, which agrees well with the theoretical analysis. Besides, the empirical relation between freezing time and contact angle were obtained.

scholarly journals Design of hybrid narrow-band plasmonic absorber based on chalcogenide phase change material in the infrared spectrum

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Israel Alves Oliveira ◽  
Igor Leonardo Gomes de Souza ◽  
Vitaly Felix Rodriguez-Esquerre
Keyword(s):  
Phase Change ◽  
Electromagnetic Waves ◽  
Phase Change Materials ◽  
Empirical Relation ◽  
Three Dimensional ◽  
Normal Incidence ◽  
Resonant Absorption ◽  
Nanophotonic Devices ◽  
Intermediate Phases ◽  
Infrared Spectral

AbstractStructures absorbing electromagnetic waves in the infrared spectral region are important optical components in key areas such as biosensors, infrared images, thermal emitters, and special attention is required for reconfigurable devices. We propose a three-dimensional metal-dielectric plasmonic absorber with a layer of PCM’s (Phase Change Materials). The phase shift effects of PCMs are numerically analyzed, and it is possible to obtain a shifting control of the resonant absorption peaks between the amorphous and crystalline states using the Lorentz–Lorenz relation. By using this empirical relation, we analyzed the peak absorption shift at intermediate phases between the amorphous and the crystalline. The geometric parameters of the structure with the PCM layer in the semi-crystalline state were adjusted to exhibit strong absorption for normal incidence. The effects of the oblique incidence on the absorption for the TM and TE polarization modes were also analyzed. Our results demonstrate that PCMs have great potential for reconfigurable nanophotonic devices.

Superhydrophobic and Highly Oleophilic Polystyrene Fibers (PS) with Delayed Freezing Time and Effective Oil Adsorption

2018 ◽  
Vol 941 ◽  
pp. 2232-2236
Author(s):  
Reza Jafari ◽  
Marc Chameau ◽  
Masoud Farzaneh ◽  
Gelareh Momen
Keyword(s):  
Contact Angle ◽  
Superhydrophobic Surface ◽  
Contact Angle Hysteresis ◽  
Aluminum Surface ◽  
Motor Oil ◽  
Freezing Time ◽  
Water Droplets ◽  
Flexible Behavior ◽  
Oil Adsorption ◽  
Very High

We present an efficient and simple approach for preparing superhydrophobic-superoleophilic polystyrene (PS) fibers via electrospinning. Bead-on-string fibers from a 5% PS solution and micro-sized fibers from a 20% PS solution were combined to achieve a surface having very high contact angle (about 160°) and low contact angle hysteresis. The presence of bead-on-string fibers increases the superhydrophobicity of the sorbent. The micro-sized PS fibers improve the mechanical properties of the electrospun mat through their elastic and flexible behavior. An evaluation of wettability at a low temperature (-10 oC) showed a delayed freezing time for water droplets on the superhydrophobic surface. Water droplets on a polished aluminum surface froze more quickly (about 6 seconds) than droplets on the fabricated superhydrophobic surface (about 500 seconds). Finally, the oil adsorption capacity of the developed superhydrophobic PS fibers, which have a porous surface structure, showed values of 69.1, 69.3 and 61.2 g/g for canola oil, olive oil and motor oil, respectively.

scholarly journals Experimental study of the internal flow in freezing water droplets on a cold surface

2019 ◽  
Vol 60 (12) ◽  
Author(s):  
Linn Karlsson ◽  
Henrik Lycksam ◽  
Anna-Lena Ljung ◽  
Per Gren ◽  
T. Staffan Lundström
Keyword(s):  
Natural Convection ◽  
Internal Flow ◽  
Light Sheet ◽  
Initial Time ◽  
Freezing Time ◽  
Water Droplets ◽  
Cold Surface ◽  
Time Period ◽  
Image Velocimetry ◽  
Marangoni Effects

Abstract The study of a freezing droplet is interesting in areas, where the understanding of build up of ice is important, for example, on wind turbines, airplane wings and roads. In this work, the main focus is to study the internal motion inside freezing water droplets using particle image velocimetry and to reveal if mechanisms such as natural convection and Marangoni convection have a noticeable influence on the flow within the droplet. The flow has successfully been visualized and measured for the first 25% of the total freezing time of the droplet when the velocity in the water is the highest and when the characteristic vortices can be seen. After this initial time period, the high amount of ice in the droplet scatters the PIV light sheet too much and the images retrieved are not suitable for analysis. Initially, it can be seen that the Marangoni effects have a large impact on the internal flow, but after about 15% of the total freezing time, the flow turns indicating increased effects of natural convection on the flow. Shortly after this time, almost no internal flow can be seen. Graphic abstract

A Unified Three Dimensional Numerical Simulation of the Pool Boiling Curve

2017 ◽  
Author(s):  
Deepak Garg ◽  
Vijay K. Dhir
Keyword(s):  
Heat Flux ◽  
Contact Angle ◽  
Numerical Model ◽  
Critical Heat Flux ◽  
Void Fraction ◽  
Pool Boiling ◽  
Three Dimensional ◽  
Boiling Curve ◽  
Wall Superheat ◽  
Experimental Values

Three dimensional numerical simulations for pool boiling of saturated water at atmospheric pressure conditions are performed on a horizontal surface using finite difference method under the framework of parallel computing. Since heat conduction in the solid phase is not considered, in order to simulate realistic heating surface, dependence of bubble nucleation frequency and nucleation site density on wall superheat and contact angle are obtained from the correlations reported in the literature. Steady state boiling curve for all the three regimes viz. nucleate, transition and film boiling has been obtained with a unified numerical model by incrementing the wall superheat for a static contact angle of 38°. Evaporative heat flux from the microlayer is separately accounted for in the present study by sub grid modeling. Both the phases are considered as incompressible while the interface separating the phases is solved using level set method. The governing equations of mass, momentum and energy for both the liquid and the vapor phase are solved coupled with the jump conditions at the interface employing ghost fluid and cut cell method. Diffusion terms are treated implicitly while convection terms are treated using second order ENO scheme. Spatial and temporal averaged wall heat flux and wall void fraction are plotted and compared against correlations and experimental values previously reported. The nucleate boiling heat flux obtained from the present numerical model is under predicted in comparison to the Stephan and Abdelsalam correlation. Comparison of the computed wall void fraction against experimental values is done for the transition boiling region. At critical heat flux formation of long vapor column was seen while intermittent liquid surface contacts were seen in the transition boiling regime. The computed critical heat flux value is lower than that obtained from the correlation of Maracy and Winterton.

scholarly journals Molecular dynamics simulation of freezing process of water droplets impinging on cold surface

2018 ◽  
Vol 67 (5) ◽  
pp. 054702
Author(s):  
Dong Qi-Qi ◽  
Hu Hai-Bao ◽  
Chen Shao-Qiang ◽  
He Qiang ◽  
Bao Lu-Yao
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Dynamics Simulation ◽  
Freezing Process ◽  
Water Droplets ◽  
Cold Surface

Three-Dimensional Numerical Study on Freezing Phase Change Heat Transfer in Biological Tissue Embedded With Two Cryoprobes

2011 ◽  
Author(s):  
Fang Zhao ◽  
Zhenqian Chen ◽  
Mingheng Shi
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Biological Tissue ◽  
Numerical Study ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Freezing Process ◽  
Ice Crystal ◽  
Obvious Effect ◽  
Phase Change Heat Transfer

A mathematical model for phase change heat transfer in cryosurgery was established. In this model, a fractal tree-like branched network was used to describe the complicated geometrical frame of blood vessel. The temperature distribution and ice crystal growth process in biological tissue including normal tissue and tumor embedded with two cryoprobes were numerically simulated. The effects of cooling rate, initial temperature and distance of two cryoprobes on freezing process of tissue were also studied. The results show that the ice crystal grows more rapidly in the initial freezing stage and then slows down in the following process, and the pre-cooling of cryoprobes has no obvious effect on freezing rate of tissue. It also can be seen that the distance of 10 mm between two cryoprobes is the most appropriate choice for operation effect in the range of operating conditions presented in this study.

Freezing Controlled by Natural Convection

1979 ◽  
Vol 101 (4) ◽  
pp. 578-584 ◽  
Author(s):  
E. M. Sparrow ◽  
J. W. Ramsey ◽  
R. G. Kemink
Keyword(s):  
Growth Rate ◽  
Natural Convection ◽  
Liquid Phase ◽  
Phase Change ◽  
Vertical Tube ◽  
Freezing Process ◽  
Freezing Time ◽  
Fusion Temperature ◽  
Invariant Temperature ◽  
Time Invariant

Experiments were performed for freezing under conditions where the liquid phase is either above or at the fusion temperature (i.e., superheated or nonsuperheated liquid). The liquid was housed in a cylindrical containment vessel whose surface was maintained at a uniform, time-invariant temperature during a data run, and the freezing occurred on a cooled vertical tube positioned along the axis of the vessel. The phase change medium was n-eicosane, a paraffin which freezes at about 36°C (97°F). In the presence of liquid superheating, the freezing process is drastically slowed and ultimately terminated by the natural convection in the liquid. The terminal size of the frozen layer and the time at which freezing terminates can be controlled by setting the temperature parameters which govern the intensity of the natural convection. The stronger the natural convection, the thinner the frozen layer and the shorter the freezing time. In the absence of liquid superheating, a cylindrical frozen layer grows continuously as predicted by theory, but the growth rate is higher than the predictions because of the presence of whisker-like dendrites on the freezing surface.

scholarly journals Prediction of Freezing Time and Numerical Model of Heat Transfer during Freezing Process

2021 ◽  
Vol 18 (116) ◽  
pp. 171-181
Author(s):  
mohsen Dalvi-Isfahan ◽  
Amir Daraei Garmakhany ◽  
◽  
Keyword(s):  
Heat Transfer ◽  
Numerical Model ◽  
Freezing Process ◽  
Freezing Time
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