Characteristics Of Ice Crystals Research Articles

Investigation on Phase Transition and Collection Characteristics of Non-Spherical Ice Crystals with Eulerian and Lagrangian Methods

Ice crystal icing occurs in jet engine compressors, which can severely degrade jet engine performance. In this paper, two different numerical calculation methods, the Eulerian method and the Lagrangian method, were used to evaluate the dynamics, mass transfer, heat transfer, phase transition and trajectory of ice crystals. Then, we studied the effects of initial diameter, initial sphericity, initial temperature of ice crystal, and relative humidity of airflow on the phase transition and collection characteristics of ice crystal particles. Results indicate that the non-spherical characteristics of ice crystals have a significant impact on their impingement limits and collection characteristics. The collection coefficient of unmelted ice crystals is positively correlated with the initial particle diameter and sphericity, and negatively correlated with the initial particle temperature and the relative humidity of airflow. The melting rate of ice crystal particles on the impact surface increases exponentially with the initial diameter of the particles, linearly increases with the relative humidity of the airflow and initial temperature of the particles, and exponentially decreases with the sphericity of the particles.

The Radiative Effect on Cloud Microphysics from the Arctic to the Tropics

Abstract Cloud representation is one of the largest uncertainties in the current weather and climate models. In this article, the observations and modeling of the radiative effect on (cloud) microphysics (REM) from the Arctic to the Tropics are overviewed, providing a new direction to meet the challenge of cloud representation. REM deals with the radiation-induced temperature difference between cloud particles and air. It leads to two common phenomena observed at the surface—dew and frost—and impacts clouds aloft significantly, which is noticed via the wide occurrence of horizontally oriented ice crystals (HOICs). However, REM has been overlooked by all of the operational weather and climate models. Based on the bin model of REM and the global distribution of radiative cooling/warming, the observations of REM from several platforms (e.g., aircrafts, field campaigns, and satellites) are coordinated in this article, yielding a global picture on REM. As a result, the picture is compatible with the global distribution of HOICs and other ice crystal characteristics obtained from various clouds on the globe, such as diamond dust (or clear-sky precipitation) in the Arctic, sub-visual cirrus clouds in the tropical tropopause layer, and other cirrus clouds from the low to high latitudes. In addition, ice crystals possess relatively strong REM compared to liquid drops because their aspect ratio is usually not one. The global picture on REM can be used by the weather and climate modelers to diagnose their cloud representation biases. It can also be used to improve the atmospheric ice retrieval algorithm from satellite observations.

AC electric field-assisted fabrication of ice-templated alumina materials and remarkable enhancement of compressive strength

A novel methodology was developed that uniquely employs alternating current (AC) electric field to fabricate ice-templated ceramics. In the methodology, AC field was applied to an aqueous ceramic suspension, and then ice-templating was performed. Field application to an aqueous ceramic suspension resulted in a net motion of ceramic particles due to DC voltage generation. Suspension concentration increased near one of the electrodes, which was controllable through AC frequency and field duration. Density of the very bottommost regions in sintered materials increased with field duration, attributed to increased local suspension concentration. In sintered materials, the thickness of non-templated region increased with field duration, whereas templated microstructure turned increasingly dendritic with field duration, suggesting a strong influence of AC field on the growth characteristics of ice crystals. AC-field assisted materials exhibited remarkably enhanced compressive strength without any change in porosity. This work contributes to advancing the ice-templating technology using externally energized fields.

Evolution of tissue microstructure, protein properties, and oxidative stability of salted bigeye tuna (Thunnus obesus) meat during frozen storage

The characteristics of ice crystals, tissue recoverability, protein properties, and lipid oxidation were investigated to reveal the effects of salting time (0–8 h) on the frozen storage stability of tuna meat. After 2 w of frozen storage, the ice crystals in tuna meat with different salting time varied in morphological properties, evolving from large columns (0 h) to ellipsoid (0.5–3 h) and plate shape (5–8 h). The ice crystals in tuna meat with salting time of 1–3 h were more stable with the extension of frozen storage. The enhanced water-holding capacity, springiness, and cohesiveness were attributed to the modified morphology and stability of ice crystals and tissue recoverability after thawing with the formation of moderate protein-protein interactions under proper salting conditions. The declined oxidative stability of salted tuna meat was likely associated with the loss of redox balance with the extension of salting as indicated by aggravated oxidation of lipid and myoglobin and discoloration. Salting time must be taken into account for the frozen storage stability of salted aquatic products, which could modify the microstructure of both frozen and thawed meat, protein properties, redox status of tissue, and thus quality attributes.

On the experimental and theoretical model for ice crystal characteristics near a substrate

For better understanding the mechanism of ice cohesion on a solid substrate, an experimental study on ice crystal structure growing from a substrate is conducted. The characteristics of crystal structure as well as their growing patterns in different supercooling degrees are observed and recorded. Besides, theoretical analysis has been carried out to identify the heat diffusion effect on crystal growing.Different from the uniform morphology and constant growing velocity observed in previous researches, it is found that the side branches upon bottom part of the crystal are usually wider and more disorderly configured while those upon upper part are always more slender and more regularly distributed. In addition, crystal growing velocity changes continuously in vertical direction with a trend of convergence. Higher supercooling degree enhances such structure evolution and advances convergence of the growing velocity. Crystal structure diversity is determined by the principle of local transient temperature evolution due to the thermal diffusion from substrate. A model is presented to estimate local supercooling degree at different height from substrate and its regularity of evolution. Comparisons are made between our results and relevant literatures for correlation.

Microstructure and quality attributes of Saurida tumbil muscle during superchilled storage as affected by shell/ and non-shell freezing

ABSTRACT The aim of this study was to determine the influence of shell freezing and non-shell freezing methods on the location/distribution of ice crystals and quality properties (microbiological analysis and physiochemical properties (pH, total volatile bases nitrogen (TVB-N), thiobarbituric acid reactive substances (TBARS), free fatty acid (FFA), water holding capacity (WHC)) during the superchilling storage of Greater Lizardfish Saurida tumbil. Non-shell frozen fillets resulted in form of extracellular ice crystals during superchilling. Shell frozen fillets formed both intracellular and extracellular ice crystals uniformly. From the result, it was found that using the shell freezing method had significant effect on reduced bacteria population or decreased capacity of bacteria or both. At the end of the storage, TVB-N, pH, TBARS, and FFA values of the non-shell freezing method was more than others (P < 0.05). There was significant difference (P < 0.05) in the WHC between shell-frozen samples and non-shell-frozen samples. Shell-frozen freezing had a strong influence on the characteristics of ice crystals (location/distribution) and quality of the final superchilled fillets.

Computation and Comparison of Cloud Infrared Radiation Characteristics

Abstract Cloud is a common weather phenomenon in the sky. It is formed by condensation of water vapor in the atmosphere. It is a suspension composed of water droplets, ice crystals or their mixtures. The infrared radiation characteristics of clouds are related to the particles phase state in clouds, the particle radius distribution and the cloud optical thickness. They are also affected by the sun, earth surface types and atmospheric conditions. In this paper, it introduces the physical parameters of the ice crystals in cloud, and researches the scattering characteristics of ice crystals. Based on radiation transfer algorithms, an ice cloud radiation model is established. The ice cloud infrared radiation is analyzed that the ice clouds infrared radiation varies with optical thickness. It shows that when the cloud optical thickness is not large, the radiance of ice clouds decreases with the increase of optical thickness.

Investigating the effect of freezing operating conditions on microstructure of frozen minced beef using an innovative X-ray micro-computed tomography method

The freezing rate determines the ice crystal size distribution and morphology. Ice crystal characteristics may have a direct impact on the microstructure of food products, providing irreversible cell and tissue damages resulting in quality losses. In this paper, an innovative method was used for imaging and quantifying ice crystals directly in frozen samples of minced beef by X-ray micro-computed tomography. The results were compared to those obtained by X-ray micro-computed tomography on freeze-dried samples. The effects of the integral cooling rate on ice crystal characteristics were studied for various mechanical and cryogenic freezing operating conditions. It was pointed out that crystals become 2.5 times smaller when the freezing temperature goes down from −30 °C to −100 °C. These crystals are also more numerous with a narrower distribution. Fluorescence optical microscopy and electron scanning microscopy were also used to do qualitative analysis. These results confirmed the effect of the freezing temperature on ice crystal sizes.

Advances in present‐day frozen dough technology and its improver and novel biotech ingredients development trends—A review

AbstractBackground and objectivesIn response to the need for product flexibility and fast response to consumer trends, research interest frozen dough technology has continued to increase since its inception in 1970s. Common categories of these products are prefermented, unfermented, and par‐baked frozen dough products, with widely known frozen dough products such as refrigerated cookies and brownies, sweet rolls, biscuits, dinner rolls, and pizza, sold “as if freshly baked” to the consumer. The underlying catalyst for the development and growth of the frozen dough products in the 1970s–1990s is closely related the development of improver technology and increased research efforts to improve frozen dough quality, thus a steady market growth in frozen dough products in the following. Despite increased popularity of frozen dough products, they are still faced with processing challenges such as reduced yeast activity and viability, damaged dough gluten–starch network, and alteration of individual dough components which are induced by freezing and frozen storage treatment. Therefore, increased research efforts by both industry and academic institutions have been vital in understanding and improving processing parameters as well as the end‐product quality of frozen bread‐dough products. This review provides an overview of the effect of ice crystal characteristics on water redistribution and major components (starch and gluten) and ingredient (yeast) during freezing and frozen storage of frozen bread‐dough systems. Additionally, advances in frozen dough improver technology such as use of hydrocolloids, ice structuring proteins, ice‐nucleating agents, and novel fermentation end products and enzymes that alter ice crystal characteristics to improve steamed bread frozen dough quality are suggested and discussed. In addition, due to the recent increase in popularity of frozen steamed products, they are used as a case study and some critical conditions for their processing were suggested.FindingsFreezing and frozen treatment on key components. Gluten: Gluten protein quality is mainly indicated by gluten macropolymer depolymerization during freezing and frozen storage. In frozen steamed dough systems, SH groups, an indicator of S‐S bond disruption, increased in gluten but fluctuated in glutenin fraction during frozen storage. This invariably increases the molecular weight distribution of the glutenin subunits (HMW‐GS and LMW‐GS). Starch: Freezing and frozen storage induces granule structure re‐organization; decline in amorphous state coupled with increase in crystallinity as starch granule materials leach out influences the A‐ and B‐type granules differently. Yeast: Freezing and frozen storage treatment decreases yeast activity and viability in frozen dough systems; with the degree of damage related to the freezing conditions used (e.g., freezing rates, ice crystal size and location, and ice recrystallization) and ability to metabolize different molecules (e.g., glycerol, trehalose, proline, arginine). Despite loss in activity and viability, yeasts are comparatively advantageous to use than chemical leaveners in frozen steamed dough systems. The degree of damage can be related to the freezing conditions used and ability to metabolize different molecules. Hydrated frozen steamed dough: three water sources identified as rigid, confined, and bulk water are found in the dough matrix system and are redistributed differently through ice crystallization and recrystallization in dough, thus affecting component structure and functionality. Bulk followed by confined water crystallizes to ice during freezing. The freezing rate applied will also affect the ice characteristics, thus altering structure and functionality. Hence, studies on water redistribution induced by ice crystallization and recrystallization may give a deeper understanding in the search of solutions to preserve gluten in frozen dough. Improver and cryoprotective technology: Advances in additives improver technology such as the use of hydrocolloids, ice structuring proteins or antifreeze proteins, and ice‐nucleating agents and the use of novel biotech ingredients and enzyme technology were able to (a) increase yeast cell freeze tolerance and (b) enhance gluten and starch functional (rheological, thermal) properties during freezing and frozen storage treatment. Subsequently, the yeast cells in frozen dough have better fermentative capacity, resulting in improved end‐product quality in terms of higher specific volume, lower hardness, and increased shelf life.ConclusionsThis is attributed to the additives ability to alter ice crystallization and recrystallization characteristics in frozen dough. Knowledge on development of ice crystallization and recrystallization during freezing and frozen storage, respectively, is useful to enable optimization of freezing conditions and reduction in temperature fluctuations to maintain yeast viability and frozen dough quality.Significance and noveltyThis overview adds new knowledge and useful insights into (a) use of biotech ingredients for clean label technology in frozen dough and food industry, a consumer demand trend for clean label products, and (b) optimization of frozen dough processing and equipment technology for modern baking and food industry.

A new fracture model for reservoir ice layers in the northeast cold region of China

The cracking and fracture behaviour of ice material in cold regions significantly affects the mechanical properties of concrete material and structures due to ice pressure or the ultimate load carrying capacity. The mechanical performance of ice material depends on the characteristics of ice crystals, ice depth, temperature and geographical distribution in different regions. The main objective of this paper was to propose an innovative model for describing the fracture toughness of ice material subjected to different geographical distributions, depths and temperatures based on the energy balance theory, the generalized self-consistent method and Gurson’s damage model, and the model results were then compared with experimental results and those of Ji. In addition, according to statistical theory, an equation for calculating the variance of the fracture behaviour of ice material was established based on the fracture flexibility results for determining the mechanical properties of the ice material.

Radiatively Induced Precipitation Formation in Diamond Dust.

Radiative cooling leads to the formation of dew and frost. This process is extended into a numerical model to simulate the ice crystal characteristics of diamond dust. The model replicates the low ice crystal concentration of diamond dust and the precipitation in stationary air. Its results are consistent with the arctic observations that large ice crystals grow while small ones sublimate and partly explain the geographic and seasonal distributions of diamond dust such as the high frequency of diamond dust in the arctic regions and winter. Furthermore, its results show that plate/column‐like ice crystals with radiative cooling grow in expense of quasi‐spherical ice particles, partly explaining the ice crystal shapes observed in diamond dust.

Numerical simulation of flow and melting characteristics of seawater-ice crystals two-phase flow in inlet straight pipe of shell and tube heat exchanger of polar ship

The ice crystal particles are easy to enter into the seawater cooling system of polar ship together with seawater when it sails in the Arctic. They are easy to accumulate in the pipeline, causing serious blockage of the cooling pipe. In this study, the flow and melting characteristics of ice particles-seawater two-phase flow in inlet straight pipe of shell-and-tube heat exchanger were numerically simulated by using Eulerian-Eulerian two-fluid model coupled with the interphase heat and mass transfer model. The influences of inlet ice packing factor, ice crystal particle diameter, and inlet velocity on the distribution and melting characteristics of ice crystals were investigated. The degree of asymmetry of the distribution of ice crystals in the cross section decreases gradually when the IPF changes from 5 to 15%. The volume fractions of ice crystals near the top of the outlet cross section are 19.59, 19.51, and 22.24% respectively for ice packing factor of 5, 10 and 15%. When the particle diameter is 0.5 mm, the ice crystals are gradually stratified during the flow process. With particle diameters of 1.0 and 2.0 mm, the region with the highest volume fraction of ice crystals is a small circle and the contours in the cloud map are compact. The greater the inlet flow velocity, the less stratified the ice crystals and the more obvious the turbulence on the outlet cross section. The average volume fraction of ice crystals along the flow direction is firstly rapidly reduced and then stabilized after 300 mm.

A study of ice crystal development in hairtail samples during different freezing processes by cryosectioning versus cryosubstitution method

Hairtail samples were frozen by three different treatments, including conventional air freezing (CAF) at −20 oC, refrigerator cryogenic freezing (RCF) at −80 oC and liquid nitrogen immersion freezing (LIF) at −196 oC. In order to investigate the influence of freezing treatments on the development of ice crystal in hairtail samples, an improved method based on cryosection was applied to observe the formation of ice crystals in frozen hairtail meat, comparing with the traditional method of cryosubstitution. Results showed that cryosectioning was a highly effective tool for intuitionistic view of ice crystals, and greatly shortened the time from 3–5 days to 20–30 min. The equivalent diameter of the ice crystals determined by cryosectioning were 12.6 ± 3.73, 3.62 ± 1.91, and 1.22 ± 0.39 µm for the samples subjected to CAF, RCF and LIF, respectively. Smaller and more regular intracellular ice crystals were observed in hairtail samples frozen by LIF compared with other treatments. The microstructure of three frozen treated samples was profiled by scanning electron microscopy as well. Significant differences were observed in the water holding capacity in frozen samples of CAF (86.8%), RCF (87.4%), and LIF (89.2%). The characteristics of ice crystals, which have a strong influence on the final quality of the food, were considered as an important factor for the quality of hairtail during freezing.

The influence of superchilling storage methods on the location/distribution of ice crystals during storage of Atlantic salmon (Salmo salar)

The objective of this work was to study the influence of superchilling storage methods, shell freezing and non-shell freezing on the location/distribution of ice crystals during the superchilled storage of salmon. Physical measurements, water holding capacity and drip loss were also studied. Non-shell frozen samples resulted in extracellular ice crystals. Shell frozen samples showed both intracellular and extracellular ice crystals with a uniform distribution. Liquid loss (LL) decreased with storage time in both superchilling storage methods. There was no significant difference (p > 0.05) in LL between shell and non-shell frozen samples. There was significant difference (p < 0.05) in the drip loss between shell frozen samples (1.62% as maximum) and non-shell frozen samples (1.4% as maximum). The information on the characteristics of ice crystals (location/distribution), which has a strong influence on the quality of the final superchilled food, is a factor key for the manufacturing of products with desired quality and shelf life.

A Novel Adiabatic-Expansion-Type Cloud Simulation Chamber

A new cloud simulation chamber was built at the Meteorological Research Institute (MRI) to investigate the details of the fundamental processes of cloud formation. The MRI cloud chamber was designed as an adiabatic-expansion-type cloud chamber covering temperatures from 30 to −100°C, pressures from 1030 to 30 hPa, and an evacuation rates corresponding to ascent rates from 0 to 30 m s−1. Improvements to the cooling system and cloud characterization instrumentation distinguish the new facility from past devices of this type that are no longer functional (e.g., the Colorado State University dynamic cloud chamber), and the capabilities exceed those of any other active facility (e.g., the Aerosol Interactions and Dynamics in the Atmosphere (AIDA) chamber) for covering a range of atmospheric conditions while reproducing approximately adiabatic parcel conditions. Results from the preliminary experiments demonstrate the accuracy of coordinated pressure and temperature controls to reproduce cloud formation processes (both dry and wet adiabatic expansion processes) and the ability of the chamber's instrumentation to measure aerosol, cloud droplet, and ice crystal characteristics. Performance tests demonstrate the chamber's usefulness as a facility to investigate cloud droplet and ice crystal formation processes through the activation of various types of aerosol particles.

Numerical simulation of macro- and micro-structures of intense convective clouds with a spectral bin microphysics model

By use of a three-dimensional compressible non-hydrostatic convective cloud model with detailed microphysics featuring spectral bins of cloud condensation nuclei (CCN), liquid droplets, ice crystals, snow and graupel particles, the spatial and temporal distributions of hydrometeors in a supercell observed by the (Severe Thunderstorm Electrification and Precipitation Study) STEPS triple-radar network are simulated and analyzed. The bin model is also employed to study the effect of CCN concentration on the evolution characteristics of the supercell. It is found that the CCN concentration not only affects the concentration and spectral distribution of water droplets, but also influences the characteristics of ice crystals and graupel particles. With a larger number of CCN, more water droplets and ice crystals are produced and the growth of graupel is restrained. With a small quantity of CCN the production of large size water droplets are promoted by initially small concentrations of water droplets and ice crystals, leading to earlier formation of small size graupel and restraining the recycling growth of graupel, and thus inhibiting the formation of large size graupel (or small size hail). It can be concluded that both the macroscopic airflow and microphysical processes influence the formation and growth of large size graupel (or small size hail). In regions with heavy pollution, a high concentration of CCN may restrain the formation of graupel and hail, and in extremely clean regions, excessively low concentrations of CCN may also limit the formation of large size graupel (hail).

Effects of locust bean, xanthan and guar gums on the ice crystals of a sucrose solution frozen at high pressure

Hydrocolloids are added in ice-creams and frozen desserts to produce smooth texture and protect the product during its storage. The high-pressure freezing techniques also aimed to enhance product qualities. In this work, both the hydrocolloid and the high-pressure processing actions are combined. A 0.3% (w/w) of guar gum (viscous solution) or of locust bean gum plus xanthan gum (gel) was mixed in sucrose solutions (16% w/w) to analyze whether water mobility affected ice crystal formation. Sucrose solutions with or without hydrocolloids were frozen by high-pressure assisted freezing (HPAF) at 100 MPa and by high-pressure shift freezing (HPSF) from 210 MPa to 0.1 and 100 MPa, to compare their effects on the ice crystal characteristics. Ice crystal sizes were determined from images obtained by low temperature scanning microscopy (LT-SEM). Ice crystals were smaller after HPSF than after HPAF, due to greater supercooling following expansion and to shorter phase transition times. As regards the hydrocolloids, ice crystals were smaller when the mixture of locust bean and xanthan gums were added irrespective of the freezing method. The formation of a gel-like structure at ambient temperature strengthened by a cryo-gelation effect in the frozen state may limit water molecule diffusion and ice crystal growth.

In Situ Observation of Cirrus Scattering Phase Functions with 22° and 46° Halos: Cloud Field Study on 19 February 1998

Observations of halos and related phenomena due to ice crystals are commonly reported from ground observations and presented in the literature. Nevertheless, ice crystal characteristics have only been poorly documented from in situ measurements performed in halo-producing cirrus with simultaneous observations of optical phenomena. Using the Polar Nephelometer, a new instrument for in situ measuring of the scattering phase function of cloud droplets and ice particles, 22° and 46° halo features have been evidenced during a cirrus uncinus cloud case study between −30°C and −38°C. Simultaneous microphysical measurements were made with a 2D-C probe manufactured by Particle Measuring Systems Inc. (PMS). The results show that ice crystal properties derived from 2D-C measurements do not present substantial differences when comparing cirrus cloud samples with and without halos. Consequently, the cloud scattering properties appear to be dominated by small ice particles (smaller than about 100 μm), which are poorly documented with conventional PMS probes. The halo occurrences are observed in only a few cloud portions (2%), which are characterized by small horizontal scales (100–400 m). Furthermore, the observed 22° and 46° peak features are smoothed out with regard to modeling results relative to geometric pristine-crystal shape. These differences are discussed by using the new Inhomogeneous Hexagonal Monocrystal theoretical model of light scattering.

New model for the vapor growth of hexagonal ice crystals in the atmosphere

We present a new microphysical model for the vapor growth and aspect ratio evolution of faceted, hexagonal ice crystals in the atmosphere. Our model is based on a novel, efficient numerical method for solving Laplace's equation for steady state diffusion on the surface of a three‐dimensional hexagonal prism, and also takes into account the surface kinetic processes of crystal growth. We do not include ventilation, so our model is limited to stationary crystals or falling crystals smaller than 100 μm. We calculate a self‐consistent solution for the distribution of the supersaturation and the condensation coefficient on each crystal face, for several different assumptions regarding the crystal growth mechanism and ice surface properties. We use this model to predict the aspect ratios expected for faceted ice crystals over a range of temperatures and supersaturations, as well as to estimate the conditions for which faceted growth becomes unstable and the crystals become hollowed or dendritic. We compare these predictions to observed features of ice cloud crystals to infer some microphysical characteristics of ice crystals and their temperature dependence. We also compare our predicted mass growth rates with those of the capacitance model for spheres and ellipsoids to look at the effects of shape and surface kinetics. Finally, we insert the single‐particle code into a simple parcel cloud model to investigate the feedbacks between crystal surface kinetics, shape, and the thermodynamic properties of clouds.

Kinetics of freezing of an oil-in-water emulsion by pressure release. Impact on ice crystals and oil droplets

Pressure release freezing (PRF) of an oil-in-water emulsion is studied. The characteristics of ice crystals as a function of freezing process is studied.