Supercooling Process Research Articles

Time-resolved X-ray Tracking of Expansion and Compression Dynamics in Supersaturating Ion-Networks.

Supersaturation of a solution system is a metastable state containing more solute than can be normally solubilized. Moreover, this condition is thermodynamically important for a system undergoing a phase transition. This state plays critical roles in deposition morphology in inorganic, organic, polymer and protein solution systems. In particular, microscopic solution states under supersaturated conditions have recently received much attention. In this report, we observed the dynamic motion of individual ion-network domains (INDs) in a supersaturated sodium acetate trihydrate solution (6.4 M) by using microsecond time-resolved and high accuracy (picometre scale) X-ray observations (diffracted X-ray tracking; DXT). We found that there are femto-Newton (fN) anisotropic force fields in INDs that correspond to an Angstrom-scale relaxation process (continuous expansion and compression) of the INDs at 25 μs time scale. The observed anisotropic force-field (femto-Newton) from DXT can lead to new explanations of how material crystallization is triggered. This discovery could also influence the interpretation of supercooling, bio-polymer and protein aggregation processes, and supersaturated systems of many other materials.

An overview of ice storms and their impact in the United States

ABSTRACTIce storms, defined by the US National Weather Service as freezing rain accumulations over 0.635 cm (0.25 inch), are often costly and destructive. Formation processes include the classic ‘melting’ process and supercooled warm rain process. Freezing rain is most commonly found ahead of a warm front or occlusion, where warm air is lifted over a cold shallow layer near the surface. Other synoptic patterns conducive to freezing rain include arctic fronts, isentropic lift over an arctic air mass, and cold air damming. Causes of spatial and temporal variations in freezing rain include, but are not limited to, terrain and proximity to water. Areas with the most occurrences of freezing rain in the United States include the Pacific Northwest, Upper Midwest, and Northeast/Appalachian regions. Empirical forecasting methods and numerical weather prediction are currently used to predict freezing rain. Successful forecasting of ice storm events requires evaluation of the thermodynamic profile of the atmosphere. Local effects such as proximity to water and topography must be taken into account, and non‐linear processes such as latent heating and cooling must not be ignored. Ice accumulation can cause tree damage, which, in addition to breakage of electrical cables, can lead to power outages. Deposition of ice also impacts road, rail, and air travel, with associated economic costs due to lost hours as workers are unable to travel. Ice storms also provide a significant risk to human health and life, with falling debris and slippery surfaces being primary threats.

Measurements of the evolution of frazil ice particle size distributions

A series of 27 experiments were carried out at three different turbulence intensities in the frazil ice production tank at the University of Alberta. The frazil particles produced were photographed in suspension throughout the duration of the supercooling process using a high-resolution digital camera. An acoustic Doppler velocimeter (ADV) was used to record vertical profiles of the velocities at three locations in the tank, and the velocity time series data were processed to determine the rate of dissipation of turbulent kinetic energy per unit mass. A computer algorithm was written to process the captured images to determine the particle sizes and compute the properties of the particle size distribution. The resulting data were used to study the evolution of the size distribution throughout the supercooling process. It was found that the number of individual particles in suspension peaked shortly after the maximum degree of supercooling had been reached, and at approximately the same time the mean and standard deviation of the particle diameter approached constant values. The overall mean particle diameter prior to the onset of particle flocculation was found to decrease with increasing values of the dissipation rate, and ranged from 0.94 to 0.66mm for dissipation rates of 24 to 336cm2/s3.

Thermomechanical transitions of egg-ceramide monolayers.

Ceramides have unique biophysical properties. Their high melting temperature and their ability to form lateral domains have converted ceramides into the paradigm of rigid lipids. Here, using shear surface rheology of egg-ceramide Langmuir monolayers, a solid to fluid transition was evidenced as a vanishing shear rigidity at lower temperatures than the lipid melting temperature. Such a mechanical transition, which depends on the lipid lateral pressure, was found in a broad range temperature (40-50 °C). The solid to fluid transition was correlated to a LC to LC+LE phase transition, as confirmed by BAM experiments. Interestingly, together with the softening transition, a supercooling process compatible with a glassy behavior was found upon freezing. A new phase scenario is then depicted that broadens the mechanical behavior of natural ceramides. The phase diversity of ceramides might have important implications in their physiological roles.

System Design and Performance Analysis of a Quick Freezer using Supercooling

Purpose: This study was conducted for enhancing the performance of a conventional quick freezer by introducing the supercooling state, using a low-temperature coolant. Methods: In the present investigation, the supercooling process was executed prior to quick freezing for reducing the time by which the temperature passes the zone of maximum ice crystal formation. Every food has different nucleation points and hence, we used silicone oil as the coolant for supercooling for easy modification of temperature. Additionally, for quick freezing, we used liquid nitrogen spray. Results: Using the heat exchangertype precooler with silicone oil, the temperature of the chamber was easily changed for enabling supercooling. Particularly, the results of the freezing test with garlic indicated that this system improved the hardness of garlic after it was thawed, compared to the conventional freezing method. Conclusions: Before quick freezing, if the food item is subjected to the supercooling state, the time from nucleation to the temperature reaching the frozen state (-5°C, which is the maximum ice crystal formation zone) will be shorter than that incurred using quick freezing alone. The combination of the heat exchangertype supercooler and liquid nitrogen sprayer is expected to serve as a promising technology for improving the physicochemical qualities of frozen foods.

Development of columnar jointing in albite rhyolite in a rapidly cooling volcanic environment (Rupnica, Papuk Geopark, Croatia)

AbstractThe Rupnica locality became the first protected geosite in Croatia in 1948 owing to a well‐exposed phenomenon of columnar jointing developed in albite rhyolite. According to the geochemical signature, melt that originated at mid‐crustal depths (10–15 km) reached a shallow emplacement level as a high‐temperature lava. Non‐destructive statistical analysis conducted at the geosite revealed that relatively narrow (29.4 ± 6.3 cm) predominantly four‐ and five‐sided columns, tightly packed striae (4.8 ± 2.1 cm) and small‐amplitude wavy sets of columns (wavelength of 32.5 ± 6.7 cm) dominate the exposed part of the Rupnica. A number of features quantified through this statistical approach, together with petrography, geochemistry and the geology of the geosite's surroundings, suggest the rapid cooling of a (sub)surface acidic lava body and the behaviour of the evolving volcanic system, developing columnar jointing under the combined influence of large‐scale constitutional supercooling and thermal contraction processes.

Kovacs effect enhanced broadband large field of view electro-optic modulators in nanodisordered KTN crystals

The unique physical effect-Kovacs effect is explored to enhance the performance of EO modulators by employing the non-thermal equilibrium state nanodisordered KTN crystals created by super-cooling process, which can have a significant 3.5 fold increase in quadratic electro-optic coefficient. This enables to reduce the switching half wave voltage (almost by half) so that a broadband (~GHz range) and large field of view (+/-30 deg) electro-optic modulator can be realized with much lowered driving power, which can be very useful for a variety of applications: laser Q-switches, laser pulse shaping, high speed optical shutters and modulating retro reflectors.

The Performance Analysis of Single Water Droplet Evaporative Supercooled Process for Ice Slurry Production

To analyze evaporative supercooled process of single water droplet in the air with low temperature and low humidity ratio, a mathematical model was constructed to simulate the evaporative process of single water droplet. The droplet temperature during its evaporation process and the influence of different initial droplet diameter, initial water temperature, air temperature and air humidity ratio were analyzed. The evaporative process of droplet in supercooled stage was simulated through the mathematical model, results from modeling basically tallies with the experiment. The numerical results show that lower initial temperature of water droplet can lessen the supercooled time of reaching steady state evaporation stage. Additionally it can not only lessen the supercooled time but also acquire lower supercooled temperature of water droplet by reducing air humidity ratio or lowering air temperature. Furthermore, the smaller initial diameter of water droplet is, the shorter supercooled time of reaching steady state evaporation stage becomes.

Effects of power ultrasound on immersion freezing parameters of potatoes

Abstract Ultrasound has attracted great interest in recent years and its application in food freezing has shown promising advantages. In the present study the application of ultrasound during immersion freezing of potato cubes was studied and particular attention was given to the effects on supercooling process. Ultrasound, produced through a 35 kHz sonotrode, was applied when the temperature in the geometrical center of potato sample was in the range from − 0.1 to − 3.0 °C. Several freezing parameters, as nucleation temperature and time, supercooling, initial freezing temperature, transition phase and global freezing duration, were evaluated and discussed. A significant anticipation of nucleation was detected when the ultrasound application temperature was lower than − 0.1 °C; moreover it was found a linear correlation between ultrasound irradiation temperature and supercooling reached in potato samples; finally a reduction in freezing time was recorded when ultrasound was applied at − 2.0 °C. Industrial relevance Ultrasound has acquired relevance in several industrial sectors, including food science and technology. In the present investigation power ultrasound has been studied in assisting and accelerating immersion freezing of potato cubes, obtaining promising results. In fact it was found that ultrasound was able to induce nucleation in the centre of potato cubes, interrupting the supercooling process. Moreover, under particular operative conditions, the freezing time of ultrasound-assisted potato cubes was significantly reduced with respect to non–irradiated samples. The results achieved demonstrate that the application of power ultrasound during immersion freezing has a great potential in the control of the freezing process. In particular the possibility of reduction of the freezing time and costs, as well as the influence of ultrasound on quality, stability and sensory properties of frozen food have a crucial importance to food industry and have to be widely investigated.

Response of the East Asian climate system to water and heat changes of global frozen soil using NCAR CAM model

Under the condition of land-atmosphere heat and water conservation, a set of sensitive numerical experiments are set up to investigate the response of the East Asian climate system to global frozen soil change. This is done by introducing the supercooled soil water process into the Community Land Model (CLM3.0), which has been coupled to the National Center of Atmospheric Research Community Atmosphere Model (CAM3.1). Results show that: (1) The ratio between soil ice and soil water in CLM3.0 is clearly changed by the supercooled soil water process. Ground surface temperature and soil temperature are also affected. (2) The Eurasian (including East Asian) climate system is sensitive to changes of heat and water in frozen soil regions. In January, the Aleutian low sea level pressure circulation is strengthened, Ural blocking high at 500 hPa weakened, and East Asian trough weakened. In July, sea level pressure over the Aleutian Islands region is significantly reduced; there are negative anomalies of 500 hPa geopotential height over the East Asian mainland, and positive anomalies over the East Asian ocean. (3) In January, the southerly component of the 850 hPa wind field over East Asia increases, indicating a weakened winter monsoon. In July, cyclonic anomalies appear on the East Asian mainland while there are anticyclonic anomalies over the ocean, reflective of a strengthened east coast summer monsoon. (4) Summer rainfall in East Asia changed significantly, including substantial precipitation increase on the southern Qinghai-Tibet Plateau, central Yangtze River Basin, and northeast China. Summer rainfall significantly decreased in south China and Hainan Island, but slightly decreased in central and north China. Further analysis showed considerable upper air motion along ∼30°N latitude, with substantial descent of air at its north and south sides. Warm and humid air from the Northeast Pacific converged with cold air from northern land areas, representing the main cause of the precipitation anomalies.

Catalytic metal-free formation of multi-walled carbon nanotubes in atmospheric arc discharge

Metallic-impurity-free, nano-sized, short multi-walled carbon nanotubes (MWCNTs) in the form of a tape have been synthesized using stabilized arc discharge under atmospheric conditions. The long, thin tape consisted of crystalline MWCNTs exhibiting indiscernibly blurred interior lattice images and a narrow, hollow core, as well as small and large nanoparticles. The disordered interior regions of the tubes were enlarged into hollow cores by thermal treatment at 2000°C, suggesting that the elongated tubes crystallize via a super-cooling process. The proposed macroscopic model for the growth process of the tubes in the arc resembles the fiber formation of a recently reported electrospinning process; thermally activated carbon ion and vapor create viscous carbon clusters, and the built-up charge in the clusters leads to the elongation into tubules.

Evaporation Characteristics of Single Water Droplet in Ice Slurry Production System of Evaporative Supercooled Water

To analyze the evaporation characteristics of single water droplet in the air with low temperature and low humidity, a theoretical model of droplet heat and mass transfer was proposed. The evaporation process of droplet in supercooled stage was simulated through theoretical model, results from modeling basically tallies with experiment, thus it is feasible to predict the evaporation characteristics of water droplet with smaller diameter by the mathematical model. The evaporative supercooled process of droplet in ice-slurry production system was calculated using the above-mentioned theoretical model. Results show that both the smaller droplet diameter and the lower droplet initial temperature can increase the cooling rate of water, in addition, the cooling rate can also be increased with the increase of air velocity or with the decrease of air temperature. Futhermore, droplet with lower supercooled temperature can be obtained with lower the air temperature. The initial droplet diameter less than 100µm can not only greatly improve the supercooling degree when the evaporative time of droplet is same, but also decrease the height of the ice making chamber.

Evaporative supercooling method for ice production

Producing ice with supercooled water is a favourable method for ice-storage. However, it undergoes the problems of often unexpected ice blockage and heavy electric power consumption. To improve, this paper proposes a new method: it evaporates water to supercooled state in an atmosphere of low humidity instead of supercooling water inside a heat exchanger; liquid dehumidification reproduces the atmosphere of low humidity to form a cycle. In theoretical analysis made about the evaporative supercooling, we ameliorate the traditional evaporation model to predict the temperature variation. To the experimental research, we adopted particle dynamics analyzer and infrared camera to examine the physical process, and it got ice with this new method. The theoretical results agree well with the experimental results. Also, it found this new method cannot only solve the ice blockage problem, but also reduce the electric power consumption and raise the efficiency. Compared with the conventional supercooled water method, the highest performance improvement can arrive at 98%. ► We present an evaporative supercooling method for ice slurry production. ► We investigate evaporative supercooling process theoretically and experimentally. ► We make analysis on the performance of the proposed systems. ► The proposed system has better performance compared to conventional methods.

Temperature dependence on free volume in cured natural rubber and styrene-butadiene rubber blends

A systematic study on the evolution of free volume as a function of the temperature in vulcanized at 433 K natural rubber (NR) and styrene butadiene rubber (SBR) in 25-75, 50-50, 75-25 NR-SBR (percent content of pure NR and SBR, respectively) blends was studied by positron annihilation lifetime spectroscopy. All samples were prepared with sulfur and TBBS (n-t-butyl-2-benzothiazole sulfenamide) as accelerator. The glass transition temperatures of the samples studied were determined by differential scanning calorimetry (DSC) and from lifetime data. In general, a sigmoidal-like complex behavior of the long-lived lifetime component, linked to the nanohole free volume, as a function of the temperature was found. For SBR, the slope of the ortho-positronium lifetime against temperature curves could be well-fitted using a linear function. For blends and also for NR, two different linear functions were necessary. This last behavior is explained in terms of the supercooled process involving a reconfiguration of the elastomeric chains. In the case of blends, the state of cure of NR and SBR in each NR-SBR sample was also taken into account in the discussion of the results obtained. Besides, thermal expansion coefficients of the free volumes in the transition and glassy region of all compounds were estimated. The differences observed in the values of this parameter are discussed by taking into account the morphology and formulation of each blend, the crosslink densities, and the role of the interphases formed between both NR and SBR elastomers.

A model on the financial panic

The mechanism of the financial panic is clarified by the two band model in a simplified capitalist society from statistical mechanics. A financial panic occurs on an occasion of the supercooling process to avoid completing the financial (buy–sell) cycles under the circumstances: extremely high consumption causes enormous bubbles of buy–sell pairs of securities in financial markets, which form the configuration entropy (the Kauzmann entropy) and trigger a chain recession. As society cools down, the dynamical processes of financial panic are governed by universal features such as the Kauzmann entropy crisis and the drastic drop of the dynamical motions (the VTF law), which also cause further recession so that a chain recession occurs. And the financial markets eventually freeze.

A novel ice slurry producing system: Producing ice by utilizing inner waste heat

Ice storage is a potential energy saving method for air conditioning systems. An ice slurry is an ideal material for ice storage. The conventional ice slurry producing method using supercooled water suffers from the instability of ice block and depends heavily on electric power. A novel ice slurry producing system utilizing inner waste heat was proposed to improve this situation. This system consists of two major processes: an evaporative supercooling process and a liquid dehumidification process. Both theoretical and experimental works are presented about these two processes. Simulation analysis has been made on the evaporative supercooling process and the performance of the whole system. Experiments were performed about the two processes. The theoretical conclusion agrees well with the experimental results. Compared with the conventional system, this new system can alleviate the burden on electric power and raise the efficiency. Those improvements are essentially attributed to the reutilization of the inner waste heat generated from the system itself.

Densification study of ITO films during high temperature annealing by GISAXS

Abstract Three thermal routes were treated on the sol–gel ITO films, i.e. conventional thermal annealing (CTA), rapid thermal annealing (RTA) and thermal cycle annealing (TCA). The near surface and internal structures of films were characterized by grazing incidence small angle X-ray scattering (GISAXS) technique. It is found that slit-like pores show fractal structures laterally and the near surface is sparser with bigger pores. Ordered pore structure normal to the film appears when films are annealed at high heating rate. The shrinkage of pores is mainly owing to structural relaxation and diffusion during the superheating process. However, the supercooling process has no significant effect on the structures. Furthermore, CTA samples have the greatest porosity and surface roughness due to the prevailing crystallization as well as the coarsening procedure. However small pores inside the films are eliminated at low temperature.

Development of a mathematical model of frazil ice evolution based on laboratory tests using a counter-rotating flume

A mathematical model to simulate the supercooling process and frazil ice evolution in a counter-rotating flume was developed. It considers the effect of frazil ice thermal growth while neglecting several complicated physical processes such as secondary nucleation, flocculation, and (or) break up. The supercooling process, vertical distribution of flow turbulence parameters, and frazil ice number concentration were simulated, as well the variation of the mean size of frazil ice during the supercooling process was modeled. The simulation results from this model show good agreement with experimental data.Key words: frazil ice, turbulence, numerical models, counter-rotating flume, supercooling.

ガスジェット浮遊型電磁溶融プロセスによって作製したLa-Cu-Ni-Co-AlおよびNd-Fe-Co-Al系バルク状近似アモルファス合金

For Rare Earth-Transition Metal-Al with high undercooled liquid formability and glass-forming ability, bulk alloys have been produced with gas jet flow type electromagnetic levitation process, which is a new containerless process. A series of alloys of La80-xCu10Ni5Co5Alx (x=15, 20, 25 at%) were analyzed with respects to the supercooled solidification process, nucleation behavior of a crystalline phase, and the possibility of the formation of bulk amorphous alloys. In addition, the similar studies were carried out for the specimens containing SiC, which is reported to be effective to enlarge undercooling when used in the containerless process. The results show that the addition of SiC suppresses the nucleation of a crystalline phase, and thus, the undercooling (ΔT) increases in the range of ΔT=0.22 to 0.28 Tm, where Tm is the melting point. In addition, partially crystallized bulk amorphous alloys with a diameter of 6 mm are obtainable for the alloys with 0.2 mass% SiC addition when they are solidified at approximate cooling rate of 100 K/s. Furthermore, the SiC free alloys of La65Cu10Ni5Co5Al15 and Nd60Fe20Co10Al10 are also obtainable as partially crystallized bulk amorphous alloys.

Numerical Simulation of Supercooling Process and Frazil Ice Evolution

A mathematical model to simulate the supercooling process and frazil ice evolution is developed from previous models. It incorporates improvements for the physical process of initial seeding, ice particle growth, secondary nucleation, flocculation/breakup, and gravitational removal. A variable Nusselt number related to the flow turbulence is used. It has been found that two calibrated parameters, initial seeding, and a parameter that limits the secondary nucleation are correlated to the turbulence intensity, which is useful for the practical application of the model developed in this paper. Furthermore sensitivity analysis is carried out for these two parameters. The simulations results show good agreements with experimental data.