Freezing Rate Research Articles

Impact freezing modes of supercooled droplets determined by both nucleation and icing evolution

Supercooled large droplet (SLD), which can cause abnormal icing phenomenon like run-back ridged ice, poses a serious threat to aircraft safety. In impact freezing of a supercooled droplet, the coupling of impact dynamics and ice growth determines its freezing rate and heat transfer efficiency, which is responsible for the abnormal icing phenomenon. The knowledge of supercooled droplet impact freezing is vital for the development of aircraft anti-icing and safety technologies. However, the effect of icing evolution on impact freezing is not well understood yet, especially on surfaces with different properties. This work experimentally investigates the freezing process of supercooled droplets impinging on surfaces with different heat conduction properties. By observing the phenomenon of droplet impact-nucleation and ice growth with high-speed camera, the frozen morphology, spreading ratio and freezing time are recorded with different temperatures and surface heat conduction properties. The mechanism of impact freezing of supercooled droplet is analyzed in different nucleation and ice growth conditions. In experiment, two frozen morphologies of droplets are found: irregular shape on plexiglass and poached egg shape on metal surface, besides the previously discovered frozen morphologies (basin, pancake, semisphere). The former shape exists when the horizontal growth rate of ice is lower than retraction rate of droplet, while the latter one exists when the vertical growth rate of ice is low enough. These two morphologies (irregular shape and poached egg) would evolve into shapes of basin or pancake with the increase of horizontal and vertical growth rate of ice, when the supercooling and surface thermal conductivity rise. During this transformation, the freezing of droplet is mainly influenced by nucleation rather than ice growth. Theoretical analysis shows that the freezing of supercooled droplet is determined by both nucleation and icing evolution. The freezing mode is nucleation-dominated if the growth rate of ice is higher than retraction rate, and the freezing mode is ice growth-dominated in the opposite case.

On melting and freezing for the 2D radial Stefan problem

We consider the two dimensional free boundary Stefan problem describing the evolution of a spherically symmetric ice ball \{r\leq \lambda (t)\} . We revisit the pioneering analysis of [31] and prove the existence in the radial class of finite time melting regimes \lambda(t)=\left\{\begin{array}{ll} (T-t)^{1/2}e^{-\frac{\sqrt{2}}{2}\sqrt{|\ln(T-t)|}+O(1)}\\ (c+o(1))\frac{(T-t)^{\frac{k+1}{2}}}{|\ln (T-t)|^{\frac{k+1}{2k}}}, \ \ k\in \mathbb N^*\end{array}\right. \quad\text{ as } t\to T which respectively correspond to the fundamental stable melting rate, and a sequence of codimension k excited regimes. Our analysis fully revisits a related construction for the harmonic heat flow in [60] by introducing a new and canonical functional framework for the study of type II (i.e. non-self-similar) blow up. We also show a deep duality between the construction of the melting regimes and the derivation of a discrete sequence of global-in-time freezing regimes \lambda_\infty - \lambda(t)\sim\left\{\begin{array}{ll} \frac{1}{\log t}\\ \frac{1}{t^{k}(\log t)^{2}}, \ \ k\in \mathbb N^*\end{array}\right.\quad\text{ as } t\to +\infty which correspond respectively to the fundamental stable freezing rate, and excited regimes which are codimension k stable.

Experimental investigation of water freezing and estimating refreezing time in ice boreholes

Borehole closure owing to the refreezing of meltwater poses a serious limitation in ice thermal drilling, and estimates of the refreezing rate are essential for determining safe drilling rates. In this paper, we describe the results of water cooling and freezing experiments in cylindrical ice holes with a diameter of 200 mm at a setup temperature within the range of −20 to −50 °C. These experiments represent a new means of estimating cooling/refreezing rates using two mutually perpendicular diametric sets of thermoresistors installed inside the holed ice sample. In a colder environment, water cooled/froze faster than in the warmer setup: the cooling rates for a hole diameter of 200 mm were 33.3 to 38.5 °C h−1 at −50 °C and 8.5 to 9.5 °C h−1 at −20 °C, while the average freezing rates were 32.3 to 35.1 mm h−1 at −50 °C and 14.9 to 20.9 mm h−1 at −20 °C. Data from the refreezing rates are applied for practical ice drilling purposes, and a method for predicting safe hot-point drilling performance in cold ice is suggested.

Effects of different freezing rates on purification efficiency of sandy soil contaminated by heavy metal copper

Over the last several decades, a variety of methods have been developed for treating contaminated sites. Which technique is applied depends on the type of contaminant, the extent of dispersion, and the likelihood of additional contamination during the cleanup. Among the selection of potential techniques is the artificial freezing method, in which soil is frozen to significantly lower the permeability and prevent further diffusion of pollutants. While this method appears to have merit in theory, few studies have investigated the migration of pollutants during the soil freezing process. In this paper, a series of artificial freezing purification tests were performed and the influences of different freezing rates on purification efficiency were investigated. The experimental results show that the freezing rate is an important factor affecting the freezing purification efficiency for heavy metal copper and the purification rate decreases rapidly with increasing freezing rate. A soil freezing rate of 0.3 °C/h results in a heavy metal copper purification rate of only 27%; far less than that of the freezing rate of 0.05 °C/h, where the purification rate is 85%. This study demonstrates that a strong correlation exists between the purification rate of heavy metal copper and the soil freezing rates. We also demonstrate that the purification rate can be expressed as a cubic of the soil freezing rate. Therefore, the optimal purification of contaminated sites can be obtained by determining the proper freezing rate.

Study on frost resistance durability and bubble parameters of high air content concrete under different freezing rate

The frost resistance durability and bubble parameters of high air content concrete under different freezing rate were studied from the perspective of macroscopic and microscopic properties. The frost resistance durability and air void parameters of concrete were analysed at multiple scales by electronic balance, non-metal ultrasonic tester and linear traverse method, respectively. The results indicated that the mass and dynamic elastic modulus of concrete decrease with the increase of freezing rate. As the freezing rate increases, the bubble spacing of concrete increases, and the average diameter of the bubbles becomes larger. Therefore, in addition to the low temperature during freezing, freezing rate is another important factor affecting the durability of concrete.

ВЛИЯНИЕ СКОРОСТИ ЗАМОРАЖИВАНИЯ НА РЫБОВОДНЫЕ КАЧЕСТВА СПЕРМЫ ОСЕТРОВЫХ РЫБ

The article describes the methods of cryopreservation which provides the reliable protection of cell organelles integrity after freezing-defrosting processes, as well as the needed supply of organic substances generating metabolic process in cells and tissues after a double temperature shock, and helps to achieve a significant progress in the cell long-term storage. There are considered the aspects of low temperature preservation of sturgeon sperm. Reproductive cells of Russian sturgeon ( Acipenser gueldenstaedtii Brandt & Ratzeburg, 1833) and sterlet ( Acipenser ruthenus Linnaeus, 1758) obtained at sturgeon hatcheries of the Astrakhan region and the research-expeditionary base “Kagalnik” in the Rostov region during spawning campaign served as the material for research. The purpose of the work was to establish optimal freezing rates during sturgeon sperm cryopreservation process that could ensure saving structural components of reproductive cells. It has been found that the freezing rate is species-specific. The best freezing speed for Russian sturgeon sperm proved to be 3°C/min. When experimenting with sterlet sperm there was registered less damage after freezing and defrosting at 10°C/min. Freezing speed 3°C/min was found less effective for sterlet sperm. Staged freezing process showed worse results in both cases. However, the quality of defrosted sperm didn’t get lower the fish breeding standards in all three studied speeds, which justifies sturgeon sperm freezing at all three rates subject to different conditions of preservation.

Effect of particle size and freezing conditions on freeze-casted scaffold

Abstract Freeze casting is one of the emerging and novel manufacturing routes to fabricate porous scaffolds for various applications including orthopedic implants, drug delivery, energy storing devices etc. Thus, it becomes important to understand this process in a deeper sense. Present work was focused to study the effect/influence of basic parameters, particle sizes, and freezing conditions on the mechanical properties and microstructures of porous scaffold fabricated by freeze casting. β-tricalcium phosphate (β-TCP) and hydroxyapatite (HAp) powder with particle sizes of 10 μm and 20 nm were used. Prepared slurries were freeze casted at constant freezing temperature (5 °C) and constant freezing rate (1.86 °C/min) to study the effect of freezing conditions on mechanical and microstructural properties of the porous scaffold. It was observed that porous scaffold fabricated by nanoparticles has given better porosity (63.22–76.16%), than scaffold fabricated by microparticles (13–43.05%) at given solid loading of both freezing conditions. Although, the range of pore size of the scaffold fabricated by nanoparticles (CFR: 2.60–0.84 μm; CFT: 1.66–0.46 μm) was lower than that of scaffold fabricated by microparticles (CFR: 9.45–4.83 μm; CFT: 4.72–2.84 μm). The compressive strength of scaffolds prepared by nanoparticles was in the range of trabecular bone. Moreover, the results of present work will pave the way for the fabrication of porous scaffold with desired pore size and porosity for various implants, energy, and drug delivery applications.

Effects of high-voltage electric field produced by an improved electrode system on freezing behaviors and selected properties of agarose gel

This work aimed at evaluating the effects of high-voltage electric field (HVEF) produced by an improved electrode system on the freezing behaviors and selected properties of agarose gel. The freezing of the agarose gel was realized by a Peltier cooler coupled with an improved electrode system. The electrode system was integrated with a dielectric spacer having high permittivity to avoid partial discharges. Results showed that HVEF combined with a low freezing rate significantly reduced the supercooling degree, enhanced the average freezing rate in particular the nucleation rate, and higher internal electric field intensity showed a better microstructure with smaller ice crystals in frozen samples. Under the highest applied voltage of 9 kV (Ein = 1.09 E+05 V/m) tested in this study, a 100% supercooling release was achieved. Maximum reductions of 78.83%, 25.79% and 28.75% were observed for the nucleation time, tempering time and total freezing time, respectively, while the phase transition time was prolonged by 14.86% as compared with the control (p < 0.05). Some reinforcement was detected in the gel strength by increasing internal electric field intensity, but not significant enough to prevent the structural damage and syneresis caused by freezing and thawing. This study suggested that HVEF-assisted freezing was able to reduce the size of ice crystals formed in semi-solid model foods, and the integration of a dielectric spacer with high permittivity to the electrode could be used as a potential method to solve the electrical discharge problem.

Pretreatment and Freezing Rate Effect on Physical, Microstructural, and Nutritional Properties of Fried Sweet Potato

Abstract. Sweet potato is a unique high-calorie food because it is an excellent source of some essential micronutrients, such as provitamin A (ß-carotene). The quality of par-fried frozen sweet potato products is impacted by several factors that have not been well researched, such as freezing rate and surface modification. In this study, our objective was to evaluate the effect of freezing rate (at -20°C, -30°C, -40°C, and -60°C), surface pretreatment including blanching and gum coating (methylcellulose, sodium alginate, or mixed gums), sample dimensions (strips or slices), and cultivar (Covington and Murasaki) on several quality attributes of fried sweet potato. Based on our study, frying at 180°C yielded the lowest oil content among the tested temperatures. Compared with Covington samples, Murasaki strips coated with mixed gums produced fried samples that were significantly (p = 0.05) lower in fat uptake (10.84%), less porous (35.5%), crispier (maximum force = 6.90 N), lighter, less red, and yellower. Higher freezing rate, 5.12°C min-1 (at -60°C), showed significantly lower fat content, and lower lightness or yellowness than lower freezing rates. Frying at 180°C significantly reduced vitamin C and ß-carotene levels from 3.75 mg and 349.27 µg per 100 g to 1.92 mg and 105.99 µg per 100 g, respectively. X-ray micro-computed tomography showed a significant decrease in porosity because of high freezing rates. The general conclusion is that faster freezing rate is better for par-fried sweet potato quality preservation. Keywords: ß-carotene, Fat uptake, Gum coating, Par-frying, Sweet potato, X-ray micro-computed tomography, Vitamin C.

Experience in designing and operating the buildings located on subsiding and heaving soils of the Minusinsk Hollows

The article presents the experience of design, expert research within the period of construction and operation of the buildings located on subsiding soils. It describes the experiment in conducting the organized soaking of a mounted house made of reinforced-concrete slabs and claydite-concrete panels. It shows the absence of danger of frost heaving while soaking the subsiding soils. There are tables demonstrating the expert studies during the inspections of deformable buildings and long-term observations over their behavior in freezing and thawing depending on the groundwater level and pressures under the bottom of the foundations. As a result of the analysis of long-term studies it has been established that the building load contributes to the reduction of frost heaving for sandy soils (fine and dust sands). In case of clayey soils, in contrast to the views on this problem emerged at the end of the 20th century, it is impossible to extinguish the migration process using pressure. If the migration flow slows down under the foundation bottom, it occurs due to the higher rate of soil freezing arising from the high thermal conductivity of the foundation body and the formation of vertical ice lenses on the borders of tension zones. The most important thing showed herein is that the thawing process in these lenses provokes the process of stability loss, where the soil protrudes from the foundation bottom. The long-term studies of frost heaving in a severe continental climate of the Minusinsk hollows enabled the development of the most effective direction of the anti-heave stabilization.

СТРУКТУРА ПРОМЕРЗАЮЩЕГО ПОДОЗЕРНОГО ТАЛИКА НА СТАЦИОНАРЕ ПАРИСЕНТО (П-ОВ ГЫДАН) ПО ДАННЫМ ЭЛЕКТРОТОМОГРАФИИ

The article presents the results of studies of freezing talik under lake with using of electrical resistivity tomography. The research was conducted on one of paleolake – khasyrey. The measurements performed in two perpendicular profiles by pole-dipole array with a maximum spacing of 435 m. According to results of two-dimensional inversion, an area of low electrical resistivity of rocks at a depth of 25-30 m associated with a freezing talik under lake was identified. It was determined that the depth of freezing within drained lake for the period from 1996 to 2018 is 17-22 m. The approximate rate of freezing is 1 m/year. Formation of talik have a resistance of 5-15 Ω·m. Frozen formations in the contours of young paleolake have apparent resistivity hundreds Ω·m. Within the boundaries of the more ancient khasyrey apparent resistivity of the frozen rocks up to several thousand Ω·m.

Quality of Aquatic Products via Cryogenic Freezing

The quality of perishable nutritious aquatic products can be sustained by the technique of cryogenic freezing. In this paper, physicochemical changes that aquatic products experienced in the cryogenic freezing process were reviewed. Due to the rapid freezing rates, cryogenic freezing resulted in the lower drip loss, higher water holding capacity and smaller ice crystals. The technique can obviate the protein denaturation of fish muscle, inhibit the formation of thiobarbituric acid reactive substances and reduce the lipid oxidation. The pH values, firstly decreased and then increased in the storage duration after cryogenic freezing. Texture of cryogenic aquatic products experienced the significant differences in different parameters. Few studies about color and sensory attributes of cryogenic aquatic products were investigated. Besides, quality drawbacks of cryogenic technique were still existed in defective morphology, thawing loss and other enzymatic changes of food products. Moreover, some methods applied recently to assist cryogenic freezing had been presented.

Researches on the freezing of blueberries and green bean pods using an experimental model of a fast freezing equipment

In order to conserve perishable food and extend the permissible storage and marketing period, one of the best methods that uses artificial frost is freezing. The action of low temperatures leads to a slowing down of the modifying processes, both nutritionally and organoleptically. The researches presented within the paper aims to determine some specific parameters for the freezing process using an experimental model of a fast freezing equipment with liquid nitrogen. Experimental researches use two species of horticultural products, namely blueberries and green bean pods. The results indicate that the values of total freezing time, average linear freezing rate and liquid nitrogen consumption for quick freezing of blueberries were higher than those recorded for green bean pods. Also, with the lowering of the set temperature inside the freezing chamber, the freezing time from 0°C to the temperature of -15°C decreases, resulting in lower freezing times, higher average linear freezing rates and liquid nitrogen consumptions with increasing tendency.

Simulation of Soil Freezing and Thawing for Different Groundwater Table Depths

Core Ideas The SHAW model was used to simulate the freeze–thaw process during freeze–thaw periods. It revealed the effects of soil texture and groundwater table depth on soil freezing and thawing. The frost depth and accumulated negative soil surface temperature relationship was determined. During freeze–thaw periods, the transformation between phreatic water and soil water will change the soil hydrothermal properties and affect the soil freezing and thawing in shallow groundwater areas. The purpose of this study was to determine the effect of four different groundwater table depths (GTDs) and two soil textures on the process of soil freezing and thawing during two successive freeze–thaw periods using the Simultaneous Heat and Water (SHAW) model. The results show that the frost depth was the maximum when the GTD was 1.0 m, and the maximum frost depths of sandy loam and fine sand were 97.6 and 98.9 cm, respectively. When the GTD was larger than 1.5 m, the maximum frost depth decreased with an increase in GTD, and the maximum frost depth of the soil profile was more sensitive to changes in the air temperature. The frost depth of the soil profile was linear with the square root of the accumulated negative soil surface temperature (ANST) under different GTDs. The ANST was influenced by the phreatic evaporation, and the soil freezing rate increased with an increase in GTD under the same ANST. This research is significant for the rational development of soil water and heat resources and the study of soil water–heat transfer in shallow groundwater areas.

Effect of freezing rate and storage time on quality parameters of strawberry frozen in modified and home type freezer

Freezing rate and storage time are the most important parameters in the losses of bioactive compounds of food during the freezing process. For this reason, the quality of strawberries which were frozen at different freezing mediums and the effect of storage time on samples were investigated in this research. The freezer section of the domestic refrigerator was used for slow freezing. Besides that, a modified freezer cabinet which capable of blowing air at a speed of 1.2 m/s at -30°C designed and produced by Bosch und Siemens Hausgerate GmbH (Çerkezköy,Turkey) was used for quick freezing. In the quick freezing chamber inside the refrigerator, the samples were provided to be frozen with a higher freezing speed than the static freezing unit of the refrigerator. Freezing time and freezing rates were determined from the cooling curves obtained experimentally. Slow and quick frozen samples were stored at −25°C for 4 months. Drip loss, total phenolic content, ascorbic acid content and total monomeric anthocyanin content of samples were significantly different after freezing and during storage time. It has been determined that higher freezing rate is essential for the better preservation of bioactive compounds of the strawberries. Freezing should be done at an appropriate freezing rate to preserve the cell structure and the nutritional content of strawberries.

Temperature in pavement and subgrade and its effect on moisture

This paper gives the results of experimental research of temperature variation and its effect on distribution of moisture in pavement and subgrade of a highway located in the eastern region of Kazakhstan. The sensors consisting of two elements have been used to measure temperature and moisture. The first of them is designed for measurement of temperature and based on the effect of thermal resistance, and the second one based on diamagnetic penetration allows measuring of moisture. Peculiarities of temperature variation in time in pavement layers and points of subgrade, temperature distribution in the depth at different time moments have been described. Important characteristics have been determined – duration of a frozen condition and freezing, average rates of freezing and defreezing in points of pavement and subgrade located in various depths. Quantity of unfrozen water in subgrade soil depends on negative temperature and initial moisture and it is satisfactorily approximated by semi-logarithmic function.

Cryopreservation of embryos and larvae of the edible sea urchin loxechinus albus (Molina, 1782)

The natural population of the edible red sea urchin, Loxechinus albus, is decreasing due to overfishing. The embryos and larvae of the species are highly useful for monitoring marine pollution, which makes it necessary to conserve gametes, embryos and larvae to facilitate their use in diverse areas of aquaculture and environmental quality monitoring. This need can be met by cryopreserving individuals representing the different developmental stages to provide an ongoing supply of genetic material of the species. The present study establishes a reproducible protocol for cryopreserving red sea urchin blastula and larvae. Toxicity tests were conducted in the first stage of this study using two permeable cryoprotectors, dimethyl sulfoxide (Me2SO) and propylene glycol (PG), at three concentrations (5%, 10% and 15%). The tests were repeated in the second stage, but mixing the cryoprotectors with 0.04 M of trehalose (TRE), a non-permeable cryoprotector. Cryopreservation tests were conducted in the third stage employing different freezing rates: 2 °C/min, 3 °C/min, 3.5 °C/min, 4 °C/min and 4.5 °C/min, using the cryoprotectors that yielded the highest post-incubation survival rates.The highest post-freezing survival rates for blastula (76 ± 7%) and larvae (79 ± 7%) were obtained with Me2SO at 10% + 0.04 M of trehalose, with freezing rates of 3 °C/min and 4.5 °C/min, respectively.

Effects of freezing method on water distribution, microstructure, and taste active compounds of frozen channel catfish (Ictalurus punctatus)

AbstractEffects of freezing method and frozen storage duration (16 weeks) at −18 °C on water distribution, microstructure, and taste active compounds of channel catfish fillets were investigated. Results showed that freezing and frozen storage resulted in increase in thawing loss, extracellular space, and loss of some taste active free amino acids and inosine monophosphate (IMP). After 16 weeks of storage, the total content of free amino acids decreased to 77.68% (static air freezing), 78.92% (air‐blast freezing), and 83.13% (liquid nitrogen immersion freezing) of their initial value, while IMP decreased by 45.06% (static air freezing), 25.08% (air‐blast freezing), and 24.11% (liquid nitrogen immersion freezing), respectively. Low‐field 1H NMR T2 relaxation data showed an increase in relaxation time of T21 and T22, and a decrease of T21 population with concomitant increase in T22 population during frozen storage. Compared with the other two freezing methods, liquid nitrogen immersion frozen fillets with rapid freezing rate showed a less alteration of quality, exhibiting more compact fiber arrangements, less thawing loss and better retention of taste active compounds.Practical applicationsFrozen storage has been widely used to preserve meat products for a long time, but it inevitably caused undesirable physical, chemical, and structural changes, thus leading to quality loss in texture, flavor, and color. And the degree of quality deterioration of frozen food varies depending on materials, freezing process, and frozen storage conditions. Frozen fillet is one of the main processed fish products. The study of the influence of freezing method and frozen storage on the quality of fillets in terms of water distribution, structural changes, and taste active compounds is of importance to better control the quality of frozen fish products in the industry.

Effect of different sugars on the freezing characteristics of Kyoho grape.

The aim of this work was to analyze the effect of different osmotic dehydration (OD) processes (sucrose, trehalose, glucose, and lactose) as a pretreatment for grape before exposure to freezing. The osmotic treatment had less effect on blueberry moisture content among different sugars. Impregnation with sugars decreases the freezing time of grapes, compared to untreated grapes. Trehalose and lactose had a remarkable effect on shortening the time for grapes to pass the zone of maximum crystallization of ice. It was concluded that drip loss and electrolyte permeability of cell membranes decreased and the soluble solids content increased after OD treatment. In addition, the firmness and L* values of trehalose-treated grapes were significantly higher than those of other treatments (p < .05). In summary, osmosis with a carbohydrate solution not only increased the freezing rate but improved quality characteristics of grapes after freezing and thawing. PRACTICAL APPLICATIONS: Grapes are subject to freezing damage during storage, including significant water loss, berry softening, off flavor occurrence, which reduce the commodity and consumption of grapes. OD can improve the freezing rate by reducing the moisture content in the raw material and reducing the impact of freezing on the quality of fruits and vegetables, which may be beneficial to the process of freezing grapes.

Forecast accuracy hardly improves with method complexity when completing cohort fertility

Forecasts of completed fertility predict how many children will be born on average by women over their entire reproductive lifetime. These forecasts are important in informing public policy and influencing additional research in the social sciences. However, nothing is known about how to choose a forecasting method from a large basket of variants. We identified 20 major methods, with 162 variants altogether. The approaches range from naive freezing of current age-specific fertility rates to methods that use statistically sophisticated techniques or are grounded in demographic theory. We assess each method by evaluating the overall accuracy and if provided, uncertainty estimates using fertility data of all available birth cohorts and countries of the Human Fertility Database, which covers 1,096 birth cohorts from 29 countries. Across multiple measures of forecast accuracy, we find only four methods that consistently outperform the naive freeze rates method, and only two methods produce uncertainty estimates that are not severely downward biased. Among the top four, there are two simple extrapolation methods and two Bayesian methods. The latter are demanding in terms of input data, statistical techniques, and computational power but do not consistently complete cohort fertility more accurately at all truncation ages than simple extrapolation. This broad picture is unchanged if we base the validation on 201 United Nations countries and six world regions, including Africa, Asia, Europe, Latin America and the Caribbean, northern America, and Oceania.