Search

The present work addresses the systematic accurate fabrication and design of biphilic surfaces having superhydrophobic circular islands surrounded by a hydrophilic background by investigating their condensation frosting and defrosting behavior. A significant delay in frost formation is observed on samples with higher superhydrophobicity ratio A*, defined as superhydrophobic area to total area ratio. As the superhydrophobic island diameter D increases from D = 500 µm to D = 700 µm (A* from 19.62% to 38.46%), a 50% improvement/delay is observed in terms of frost formation or densification. Besides delaying icing/frosting, the presence of superhydrophobic areas empowers the formation of porous and nonuniform frost structure, which facilitates ice removal during the defrosting process. To this end, as the surface is recovered the ambient temperature, almost complete passive cleaning performance within only 23 s is observed on the biphilic design having superhydrophobic islands with the diameter of D = 500 µm, that is, a superhydrophobicity ratio A* of 19.62%. This work concludes on the optimum biphilic ratio, which is not only effective as a passive method by hindering frosting but also leads to a slush/water free surface after defrosting eased by the Laplace pressure gradient which is imposed by the different biphilic wettability patterns. [ABSTRACT FROM AUTHOR]

Modern methods of food processing combine ultrasonic and microwave treatment. This article reviews scientific publications on combined microwave and ultrasound technologies in food processing. The review involved standard methods of data analysis and covered 85 Scopus and Web of Science research papers on combined microwave and ultrasonic food treatment published in English in 2010–2023. The article describes the principles and specific features of ultrasonic and microwave food processing methods, their combinations, equipment design, and applications as part of various food processing stages, e.g., defrosting, drying, extraction, sterilization, etc. Microwaves increase the heating rate while ultrasound increases the efficiency of heat and mass transfer. Their combined use reduces processing time, improves product quality, facilitates moisture drainage, and provides uniform heating. The combined effect of microwaves and ultrasound increases the processing efficiency, thus preserving the nutritional value and quality of the final product. Ultrasonic technology serves as an aid to efficient and environmentally-friendly microwave heating, which has a wide range of applications in the food industry. The review can be used in further research in extraction, drying, defrosting, and sterilization. It can help food industry specialists to select optimal food processing methods.

Abstract The present work addresses the systematic accurate fabrication and design of biphilic surfaces having superhydrophobic circular islands surrounded by a hydrophilic background by investigating their condensation frosting and defrosting behavior. A significant delay in frost formation is observed on samples with higher superhydrophobicity ratio A*, defined as superhydrophobic area to total area ratio. As the superhydrophobic island diameter D increases from D = 500 µm to D = 700 µm (A* from 19.62% to 38.46%), a 50% improvement/delay is observed in terms of frost formation or densification. Besides delaying icing/frosting, the presence of superhydrophobic areas empowers the formation of porous and nonuniform frost structure, which facilitates ice removal during the defrosting process. To this end, as the surface is recovered the ambient temperature, almost complete passive cleaning performance within only 23 s is observed on the biphilic design having superhydrophobic islands with the diameter of D = 500 µm, that is, a superhydrophobicity ratio A* of 19.62%. This work concludes on the optimum biphilic ratio, which is not only effective as a passive method by hindering frosting but also leads to a slush/water free surface after defrosting eased by the Laplace pressure gradient which is imposed by the different biphilic wettability patterns.

The article presents the results of a study of the quality indicators of brine-ripened cheeses produced from defrosted sheep’s milk. The objects of the study were natural and defrosted sheep’s milk, brine-ripened cheeses from this milk. The study of defrosted sheep’s milk (experiment) was carried out after 10 days of its storage at a temperature of –18 °C followed by defrostation at a temperature of 20 ± 2 °C. The composition of natural sheep’s milk (control) was examined after storage for 24 ± 12 hours at a temperature of 4 ± 2 °C. It has been found that the freezing of milk and its subsequent defrostation did not have a significant effect on the milk solids content, the mass fraction of protein and fat, titrated acidity; however, the mass fraction of calcium decreased, on average, by 20%. Freezing milk did not significantly affect the total number of micro- organisms, including spore aerobic microorganisms and molds. A decrease in the number of somatic cells (from 3.0 to 4.5 times) was found. There were no differences between the control and experimental milk samples in the renneting ability. The level of syneresis of clots in the control sample was 16 ± 1% higher compared to the experimental sample. The cheeses were produced according to the traditional technological scheme of brine-ripened cheese using a production mesophilic bacterial starter culture. The control and experimental cheeses did not differ significantly in physical and chemical parameters. According to the degree of proteolysis, there were no significant differences between the control and experimental variants. In the experimental sample, a decrease in the buffer capacity of the cheese mass was noted in comparison with the control cheeses. The freezing of milk did not have a significant effect on the taste characteristics of the cheeses: in both variants, the cheeses were characterized by a weakly expressed cheese, fermented milk taste with original taste of sheep’s milk. More noticeable differences were found in the consistency of the cheeses. In the control version, the consistency was characterized as tender, slightly brittle; in the experimental version, it was less tender, but brittle and slightly powdery. The greatest deterioration in consistency was observed in the samples of frozen cheese made from natural milk after defrosting; it was characterized as brittle, powdery, crumbly.

An approach for calculating the energy required for defrosting and subsequent heating of frozen wood during thermal treatment in the production of veneer has been presented. Using two own unsteady models the duration of regimes for steaming of prisms in an autoclave and for boiling of logs in a pit, and also the average mass temperature of the prisms and logs and the energy accumulated by them at the end of heat carrier introduction in these regimes was determined. The obtained values of average temperature were introduced in third own model for engineering calculation of the energy considered in the approach. Computer simulations were carried out for beech prisms with a cross section of 0.4 × 0.4 m and beech logs with a diameter of 0.4 m at an initial wood temperature of −10°C, −20°C, and −30°C and moisture content of 0.6 kg·kg−1. The operating temperature of the prism steaming regimes was equal to 130°C, and that of the log boiling regimes was 80°C. The approach can be applied using Excel for computing the energy and its components needed for defrosting and heating of different frozen capillary-porous materials subjected to multiple types of thermal treatment. [ABSTRACT FROM AUTHOR]

Vapor spontaneously diffuses from areas of high concentration to areas of low concentration as a consequence of the Second Law of Thermodynamics and the hunt for maximum entropy. The distribution of substances with lower saturated vapor pressures on a surface can create this concentration slope in the space. However, most substances, except ice, cannot maintain this slope because humidity sinking causes their saturated vapor pressure to drop. Moreover, the location of ice growth is difficult to control. In this paper, a pattern of CaCl2 was made on the micronano hierarchically aluminum substrate. When the temperature drops below zero, the vapor pressure at the position where CaCl2 is located is low relative to that of water as a way to achieve a continuous phase transition from solid CaCl2 to brine to ice. Thus, vapor nearby continuously diffuses to and deposits at the site, resulting in a lasting dry region around without water condensation. The frost growing on the pattern is also fluffy and can be easily removed by gravity and/or wind. This work has promising applications in areas where it is extremely difficult to use active deicing methods. [ABSTRACT FROM AUTHOR]

This paper applies the phase-change cold storage technology to refrigerated transportation to reduce the energy consumption. Experiment data showed that the electronic expansion valve can be randomly adjusted to simulate the temperature within negative 25 °C to negative 5 °C, and a system for defrosting at low temperature and auxiliary refrigeration based on phase-change thermal energy storage of diethylene glycol were developed to guarantee the reliability of the cold chain system. [ABSTRACT FROM AUTHOR]

The migration and redistribution of refrigerant are critical factors that affect the refrigeration system performance. To improve the defrosting and start-up heating performance, it is essential to investigate the transient distribution characteristics of refrigerant mass. However, quantitative studies on the transient distribution of refrigerant during defrosting and start-up heating stages in heat pump systems are scarce. The dynamic characteristics of defrosting and start-up heating cannot be deeply understood from the perspective of refrigerant migration. Therefore, the purpose of this paper is to experimentally study the transient distribution characteristics of refrigerants during defrosting and start-up heating stages for different defrosting strategies. Based on the refrigerant-side dynamic characteristics, the defrosting cycle is divided into three stages for the defrosting strategy with the indoor fan off, the indoor coil charging stage, accumulator charging stage, and wet compression stage. Additionally, for the defrosting strategy with the indoor fan on, it is divided into two stages: the indoor coil charging stage and the outdoor coil discharging stage. For the defrosting strategy with the indoor fan off, the wet compression phenomenon occurs at 240 s, which poses significant challenges to the stability of the compressor. At the end of defrosting, the accumulator retains the most refrigerant for both defrosting strategies. From the perspective of refrigerant transient distribution, the start-up heating stage is the process of refrigerant migration from the accumulator to indoor and outdoor coils. The two main factors that affect start-up heating performance are heating the indoor coil metal, and vaporizing the liquid refrigerant in the accumulator. For the defrosting strategy with indoor fan on, the energy consumption of heating the indoor coil and vaporizing the liquid refrigerant is reduced by 45.7 % and 48.9 % during start-up heating. Based on the transient refrigerant distribution experiment, some methods to improve defrosting and start-up heating are also proposed. This study can provide useful insights into the transient distribution of refrigerants and provide guidance for defrosting optimization.

Abstract Four hot-gas bypass defrosting configurations for CO2-NH3 cascade blast freezer for application in fish processing firm are numerically investigated. Due to the high moisture content of fish, defrosting is necessary after every 4 to 5 h of batch operation. A thermodynamic model for the cascade system and defrosting was developed to study various defrosting configurations formulated by rearranging the existing compressor to operate as a defrosting compressor and with the addition of an external defrosting compressor. From the simulation findings, it can be summarized that the conventional hot-gas bypass defrosting without defrost compressor is suitable for a high-capacity cascade refrigeration system with more than three evaporators. For low cooling capacity refrigeration systems, a defrosting compressor is necessary to elevate the temperature above the cascade condensing temperature. A dedicated defrosting compressor with a power consumption of 3.1 kW and a modified refrigeration/defrosting compressor with a power consumption of 6.8 kW can deliver 33.3 kW of heating at a temperature of +10 °C (45 bar). Incorporating a desuperheater between the main and defrosting compressors reduces compressor temperature and maintains the lubricating oil stability, without change in defrosting energy consumption and less exergy loss. The defrosting efficiency is obtained in the range of 39.7–42% which is in agreement with published literature.

The article is devoted to the research in the field of using frozen grapes in the technology of production of products for a healthy diet. The main objectives of the research are to substantiate technological significance of frozen table grapes for the development of functional desserts. To study the influence of negative temperatures on the gelling and complexing ability of pectin substances in frozen grapes with subsequent defrosting of the raw material. The object of the research was table grapes of 5 varieties grown in the Krasnodar region. Experimental studies of technological and biochemical parameters of fresh and frozen grapes in order to study and confirm the use of grapes in the food industry for the development of desserts with different functional areas were carried out on the territory of the Kuban State Agrarian University named after I.T. Trubilin in the laboratories of the Faculty of Food Production and Biotechnology. Biochemical methods of analysis, generally accepted in the food industry, were used as research tools. It is well known that low-temperature freezing helps to maximize the preservation of the nutritional value of plant materials, however, in the health food industry, recipes and technologies for processing frozen grapes are practically not represented. An information search of scientific literature has shown that there are no studies on the study and selection of grape varieties for canning by freezing and the production of functional products from defrosted raw materials, which indicates the need to conduct experimental studies, study the kinetics of the chemical and biochemical composition of fresh, frozen and defrosted grapes in order to differentiate raw materials for the production of desserts with different functional orientations. Using biochemical analysis methods, it has been established that, regardless of varietal characteristics, the main components of the chemical composition of grapes are preserved during freezing and further defrosting.

Four hot-gas bypass defrosting configurations for CO2-NH3 cascade blast freezer for application in fish processing firm are numerically investigated. Due to the high moisture content of fish, defrosting is necessary after every 4 to 5 h of batch operation. A thermodynamic model for the cascade system and defrosting was developed to study various defrosting configurations formulated by rearranging the existing compressor to operate as a defrosting compressor and with the addition of an external defrosting compressor. From the simulation findings, it can be summarized that the conventional hot-gas bypass defrosting without defrost compressor is suitable for a high-capacity cascade refrigeration system with more than three evaporators. For low cooling capacity refrigeration systems, a defrosting compressor is necessary to elevate the temperature above the cascade condensing temperature. A dedicated defrosting compressor with a power consumption of 3.1 kW and a modified refrigeration/defrosting compressor with a power consumption of 6.8 kW can deliver 33.3 kW of heating at a temperature of +10 °C (45 bar). Incorporating a desuperheater between the main and defrosting compressors reduces compressor temperature and maintains the lubricating oil stability, without change in defrosting energy consumption and less exergy loss. The defrosting efficiency is obtained in the range of 39.7–42% which is in agreement with published literature. [ABSTRACT FROM AUTHOR]

Vegetables are perishable and cultivated seasonally. The aim of this study was to employ a combined thawing through hot air-infrared system, while investigating the effects of temperature, airflow velocity, and infrared radiation power on thawing time and the quality attributes of thawed carrots. In this research, carrot samples, having been washed and shaped using a cylindrical mold measuring 22.5 mm in diameter and 12 mm in height, were subjected to freezing at -18°C for 48 hours. Thawing parameters were air temperature (30°C and 40°C), airflow velocity (0.5 and 5 m/s), and infrared power (100 and 300 watts). The sample thawed at 25°C was control sample. Data analysis showed that reciprocal effect of increasing temperature, power of the radiation source and air flow speed had a significant effect on the thawing time, vitamin C, βcarotene, the thawing loss, and pH (P≤0.05). This system was able to significantly reduce the thawing time this time for the control sample was 47.66 minutes and for the shortest thawing time, the treatment 8 (F5P300T40) was 6.23 minutes. The lowest pH value was related to treatment 7 (F0.5P300T40) 5.81 and the highest value was related to treatment 1(F0.5P100T30) 6.15. The highest amount of β -carotene was related to treatment number 8 (F5P300T40) 48.12 mg/100g and the lowest amount was related to treatment 5 (F0.5P100T40) 14.03 mg/100g. The highest amount of vitamin C was related to treatment 4(F5P300T30) 12.36 mg/100g and the lowest amount was related to treatment 1(F0.5P100T30) 3.68 mg/100g. In the thawing loss, the highest amount was related to treatment 1 (F0.5P100T30) 19.7% and the lowest amount was related to the control sample7.44%. Combined thawing is widely used in the food industry and for various products. Due to the low start-up cost, shorter process time and favorable quality, hybrid defrosting is widely used in the food industry. [ABSTRACT FROM AUTHOR]

Introduction. The aim of the study was to evaluate changes in the content of ascorbic acid, bioflavonoids, and ß-carotene, as well as the organoleptic properties of frozen wild berries under the influence of cryoprotectants after long-term storage. Materials and methods. Wild edible berries (fresh, frozen, and defrosted) of chokeberry, blackberry, raspberry, blueberry, and guelder rose were used in the study. The berries were frozen under the protection of a cryoprotectant (a 10% aqueous solution of sucrose together with a 1% solution of citric acid). Defrosting of frozen berries after 9 months of storage was performed by four different methods to determine the most effective one. Results and discussion. The berries contain ascorbic acid ranging from 49.7 (guelder rose) to 139.5 (chokeberry) mg/100 g of fresh weight (FW), and β-carotene ranging from 1.94 (blueberry) to 3.76 (chokeberry) mg/100 g FW. Wild berries had high content of bioflavonoids, ranging from 785 mg/100 g FW (guelder rose) to 1654 mg/100 g FW (blueberry). Even after 9 months of storage, frozen berries under the protection of cryoprotectants lost no more than 11.6% of ascorbic acid that is the most labile bio-component; sensory characteristics of the berries showed almost no significant difference with fresh raw material by all indicators. The methods of defrosting frozen berries affect sensory characteristics and the indicator of cell juice loss of the resulting product; the most effective method was found to be defrosting berries in a refrigerator at a temperature of 0 ℃ for 30-33 minutes. This method preserved the tissue strength of the berry surface completely, resulting in null loss of cell juice. The best indicators were obtained after thawing the berries in air at a temperature of 18-22 ℃ for 130-135 minutes: the loss of cell juice was 19.8%, and the surface of the berries had cracks, so the sensory characteristics were 4.1 points, and 3.7 points for the color. Frozen berries proved to be a reliable source of vitamins for dietary needs: 50 g of berries provide the human body with 24.9-65.7% of the Recommended Dietary Allowances for ascorbic acid, 19.0-36.6% for β-carotene, and 156.4-332.2% for bioflavonoids (priority was given to blueberries). Conclusions. Berries, processed with a water solution of cryoprotectant before freezing, after 9 months of storage, showed almost no significant difference with fresh raw materials in terms of vitamin content and sensory characteristics. The optimal conditions for defrosting of berries was temperature 0 ℃ for 30-33 minutes. [ABSTRACT FROM AUTHOR]

Many meat processing enterprises use the frozen raw meat. Its defrosting and thawing is a crucial technological operation that fundamentally affects the quality of food products. The experience and knowledge obtained directly in the workshop in the process of thawing the raw materials and their using to obtain a specific finished product are of great importance. Defrosting and thawing of the frozen beef meat, as one of the stages of raw meat processing, still remains a challenging process in industrial food production. The importance of this process is constantly increasing due to the growing volumes of frozen raw materials processed in food enterprises. Scientific research shows that one of the most efficient methods of defrosting and thawing is the process of meat thawing with saturated water steam under vacuum. When applying the steam the raw materials is heated at its least and minimal losses are observed, while the duration of the process is significantly reduced. This work examines the process of beef meat defrosting and thawing with simultaneous shaking and crumpling the frozen mass, which can be called as massaging of raw materials. As studies have shown, this method of thawing makes it possible to reduce losses down to almost zero and obtain raw materials with good structural characteristics for the production of a finished product with a wide range of consumer properties. The obtained experimental curves of changes in the mass and temperature of raw materials make it possible to analyze the kinetics of heat transfer and mass transfer processes at the macro- and micro levels of the food system, which serve as the basis for modeling and controlling the technological process. This study presents the results of conventional defrosting and thawing of the raw meat but combined with massaging. Studies of the parameters of processing modes have shown that the proposed program makes it possible to use efficiently the design and technological features of the defroster-massager in order to obtain the raw beef for the production of high-quality food products. The results of experimental studies and their analysis allow making conclusion about the prospects of applying this process for the other types of raw meat materials before the main technological processing of raw materials.

80% of current UK housing stock is expected to still be in use in 2050. Difficult, intrusive and expensive, refurbishment measures are required to achieve the level of insulation required for current low temperature heat pumps. Transcritical CO2 heat pumps can achieve higher efficiencies, with higher output temperatures, than current, Carnot limited, synthetic gas heat pumps, with less environmental impact. Widely deployed in water heating and supermarket chilling systems, CO2 heat pumps need heating return temperatures of 30 °C or less to function effectively. This has impeded their adoption with hydronic heating systems which have high return temperatures.This study identified system modifications external to the refrigeration cycle that address return temperatures. It modelled a transcritical CO2 air source heat pump with a hydronic heating system in a solid wall semi-detached house. Full year system coefficients of performance over 3 were achieved in four UK locations by using space heating return fluids to defrost the air source heat exchanger and to pre-heat inlet water, recovering any remaining excess return fluid heat as a source for the heat pump. Solar panels boosted this to 5.1. The levelized cost of energy for the system was calculated (with heat pump grant) at 22p/kWh, lower than a gas boiler, with 9.45 tonnes CO2 emission savings over a fifteen-year life.

• Dynamic characteristics of refrigerant and lubricating oil were researched. • R290 LT-AWHP have different defrosting time with different oil. • Different oil has different change trend of oil sump physical properties. • μ ol is lower than the steady state value for a long time after defrosting. • Oil sump level drops a lot after the four-way valve reversed first time. The dynamic characteristics of refrigerant and lubricant in R290 rolling piston compressor used in LT-AWHP (ambient temperature (t a) of 7 ∼ −30 °C) are not clear at present. In this study, the changing characteristics of suction and discharge pressure and temperature, physical properties of oil sump (temperature, viscosity, solubility) and oil sump liquid level in the high pressure shell double-cylinder rolling piston compressor during defrosting cycle (steady state→ defrosting→ steady state) were experimentally researched in a R290 LT-AWHP with the rated power consumption of 1.9 kW using PAG40 and POE68 lubricants at t a of −12 and −20 °C. The results show that, the defrosting time and the change rule of oil sump physical properties are different when completely miscible oil and partially miscible oil used, but the defrosting time (about 3 – 5 min) is less than that of the R290 air to air heat pump (about 8 min). After defrosting, the fluid in the upside of compressor shell remains liquid and gas mixture for a long time, which would decrease total heating performance of the heat pump. After defrosting, oil sump viscosity is lower than the steady state value for a long time after discharge pressure is stabilized again. Within a period after the four-way valve reversing, the oil sump liquid level drops a lot, which may result in metal wear for insufficient oil supply on the side of sliding vane. This research would promote the improvement of defrosting process and provide guidance for the lubricant selection of R290 LT-AWHP. [ABSTRACT FROM AUTHOR]

The article presents the results of a study of the quality indicators of semi-hard cheeses produced from defrosted goat’s milk. Natural and defrosted goat’s milk, semi-hard cheeses with a low temperature of the second heating were used as objects of research. Studies of defrosted goat’s milk were carried out after 6±1 days of its storage at a temperature of minus 18°C and subsequent defrosting at a temperature of 37±2°C for 60 minutes; natural goat’s milk — after storage for 24±12 hours at a temperature of 4±2°C. It was found that milk freezing and its subsequent defrosting did not affect the chemical composition of milk and the total content of microorganisms, but the number of somatic cells decreased. Cheeses were produced according to the traditional technological scheme of semi-hard cheese using a bulk mesophilic-thermophilic bacterial starter culture. There was no significant effect of the freezing process of goat’s milk on its technological properties: the duration of curd formation in both variants was (30±1) min, the duration of processing of cheese grain was (90±2) min. The level of syneresis was (55±2)% in the control, (55±6)% — in the test versions and was in the range of error of the method. The degree of transition of dry matter to whey was: in the control — (7.26±0.21)%, in the test — (7.21±0.32)%. It was found that there were no differences in the degree of proteolysis in cheeses during ripening. The values of the acidity the content of available fat in the cheeses of both variants was comparable. The organoleptic characteristics of cheeses at the standard age of 60 days had similar characteristics, both in terms of the degree of intensity of the cheese taste, and in the taste notes of “zest” and “spice”, typical of goat’s milk cheeses. The cheese texture of both variants was characterized as “homogeneous, moderately dense”. It has been established that the process of freezing goat’s milk does not reduce its cheese properties and the qualitative characteristics of the semi-hard cheese produced from it.

In order to solve the problem of frosting on surface of the evaporators in rapid freezing equipment, a new defrosting system was proposed based on pneumatic defrosting and heat storage defrosting. A three-dimensional flow model including an evaporator and a thermal flow defrosting system was established to observe the temperature distributions of the fins and gas flowing outside the evaporator and to reflect the defrosting effect. The correctness of the model was verified by a freezing experiment. On this basis, the effects of the nozzle placement hole sizes, hot air inlet temperatures and velocities on the fins and cold air temperatures were simulated. The results show that the appropriate horizontal distance between the nozzle and the evaporator is 40 mm considering the large area of heat transfer. The initial temperatures of the hot gas and nozzle sizes have little effects on the heat exchange areas, but the initial velocities of the hot gas have great effects on the heat exchange areas. It takes 180 s for the air outlet temperature of the heat accumulator with the decrease of the temperature from 44 °C to 25 °C. The frost on the surface of the fin melts rapidly within the time that the heat accumulator can maintain a certain temperature range. More studies are required to perform defrosting experiments by choosing appropriate heat storage materials and elevating gas pressure and temperature.

Heat pumps are used for energy-efficient heating in electric vehicles. If ambient air is used as a heat source, frost may form on the surface of the exterior heat exchanger at low ambient temperatures. If significant amounts of frost accumulate, the heat exchanger performance degrades and it must be defrosted. The aim of this work is the energy analysis of a heat-release-controlled vehicle heat pump with a direct flat tube evaporator in cyclic frosting and defrosting operation. The effects of fan speed and number of refrosting phases on the heat quantity released per frosting phase are analyzed on a laboratory test rig. The experiments show that the heat quantity released decreases with lower fan speed and increasing number of frosting phases. Defrosting operation parameters are also examined using the test rig and it is found that shorter defrosting times can be achieved at higher compressor speeds and larger expansion valve openings. A numerical model of the heat pump in cyclic frosting and defrosting operation is developed and validated using test rig data. An average relative deviation of less than 7% is determined between the model and experimental data. The heat pump is then integrated in a prototypical vehicle and the model is calibrated with experimental data from test drives. A numerical study of the validated vehicle heat pump model in cyclic frosting and defrosting operation shows a maximum increase of the mean total electric power consumption of 33% between dry air and saturated moist air at an ambient temperature of 0 °C. At an ambient temperature of -10 °C the mean total electric power consumption increases by 17% from dry air to saturated moist air conditions. • Experimental analysis of a vehicle heat pump in a cyclic frosting operation. • Experimental analysis of a defrosting process of a vehicle heat pump. • Modeling of cyclic frosting and defrosting process for a vehicle heat pump. • Model validation on a test rig and a prototypical vehicle. • Vehicle heat pump energy analysis in cyclic frosting and defrosting operation. [ABSTRACT FROM AUTHOR]

Whipped desserts made of fermented milk are very popular. They also make it possible to expand the range of functional products. The consumer properties of defrosted desserts depend on the air phase. This research featured the impact of different formulations and methods on the dispersion of the air phase in the process of defrosting fermented-milk desserts. The study featured several samples of whipped fermented desserts. Sample 1 contained gelatin; Sample 2 contained pectin. Samples 1 and 3 had different contents of fermented foundation while Samples 3 and 5 differed in the amount of gelatin stabilizer. Sample 4 contained a whey protein concentrate. The dispersion of structural elements was measured using microstructural methods. The experiments included the quality parameters of mixes, as we ll as the dispersion of air phase in the frozen state and after 24 h of storage at 4 ± 2°C. The viscosity of the sample with pectin exceeded that with gelatin by 3.8 times. Extra whey protein increased the viscosity by 4.4 times and the overrun – by 1.4 times. In the whey protein sample, the average diameter of air bubbles was 36 μm after 24 h of storage at 4 ± 2°C and 50 μm after 12 months, while in the sample without protein it was 48 and 86 μm, respectively. Sample 3, which had a greater fermentation, demonstrated a smaller average diameter of air bubbles (by 21 μm) after 24 h of storage than the sample with yogurt. The sample with extra gelatin increased the overrun by 1.3 times and negatively affected the dispersion of the air phase. After 24 h of storage, the average diameter of the air bubbles in the sample with an increased content of stabilizer was higher by 27 μm. The air phase was less stable in the sample with pectin. The research established the effect of gelling agents, whey protein concentrates, and fermented foundation on the dispersion and stability of the air phase in fermented-milk desserts. Pectin appeared to have a negative effect on the air phase during defrosting and caused excessive condensation and drainage. The increasing amount of fermented base and gelatin, as well as the use of whey protein concentrates, increased the stability of the air phase during 24 h of storage at 4 ± 2°C. The research results could be used to develop new production technologies of overrun fermented desserts and their preservation in the defrosted state.

The article is devoted to the research in the field of the use of frozen grapes in the production of functional products. The main tasks are to substantiate the technological significance of frozen table grapes for the development of recipes for functional products and to investigate the influence of negative temperatures on the change in the quality indicators of raw materials. The objects of the research are 5 table varieties of grapes grown on plantations of the peasant farm of the Dinskoy district of Krasnodar. At the Department of Technology of Storage and Processing of Crop Products of the Kuban State Agrarian University named after I.T. Trubilin, experimental studies of the qualitative characteristics of fresh grapes have been carried out in order to study and confirm the prospects for using frozen grapes for the production of functional products. To perform the research, standard physicochemical and organoleptic methods of analysis, generally accepted in the food industry, have been used. The grape berry is a source of nutrients that the body needs to maintain a full and active lifestyle when consumed fresh: anthocyanins, pectins, vitamins and minerals.The disadvantage of replenishing these nutrients is the short period of consumption of fresh grapes. To study the technological qualities of grapes, varieties with different ripening periods have been studied.Freezing as a preservation method allows these products to be consumed throughout the year. The methods of physical and chemical analysis have been used to determine the indicators of the biochemical composition of fresh and defrost grapes, confirming their biological and nutritional value. It has been established that shock freezing of grapes with subsequent defrosting allows preserving biologically valuable components of the chemical composition of the objects under study, which makes it possible to develop healthy food products from frozen table grapes.

The paper aims to investigate how to improve the performance of a refrigeration system (Rs) that equips a cold room, by incorporating phase change materials (Phase Change Materials - PCMs) in these systems, a study that has not yet been extended experimentally. The study is carried out on a cold room within the National University of Science and Technology Politehnica Bucharest - Faculty of Mechanical and Mechatronics Engineering, Department of Thermodynamics, Engines, Thermal and Refrigeration Equipment. This room is equipped with a refrigeration system with mechanical vapour compression (VCRs), which uses R404A as refrigerant. Mechanical vapour compression refrigeration system (VCRs) with an evaporation temperature below 0oC causes ice to form on the evaporator leading to reduced performance. Currently, the widely used methods for defrosting are the standard methods, the most used being the electric one, which of course consumes energy. This paper aims to evaluate the availability of heat that could be used in the defrosting process by means of PCMs. The study was made using the Engineering Equation Solver software, several types of PCMs and also different refrigerants (R600a, R600, R1234yf, R1234ze, R152a, R290, R32) and in this way it was intended to identify the right agent to be used for a particular type of PCM. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Refrigeration is the property of Journal of Refrigeration Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Frosting behavior and dynamic defrosting characteristics of horizontally oriented hybrid surfaces with heterogeneous wettability were experimentally investigated. The developed hybrid surfaces with superhydrophobic patterns built on superhydrophilic background integrated the properties of frost retardation under frosting conditions and fast surface cleaning of residual water upon defrosting. Four types of hybrid surfaces with different pattern spacings were tested in this work. Hybrid surfaces exhibited superior anti-frosting performance compared with that of a bare copper surface but lower than a complete superhydrophobic surface. During defrosting process, surface energy gradient and Laplace pressure gradient enabled by heterogeneous wettability on hybrid surfaces could drive the mobile slush composites on superhydrophobic regions move to superhydrophilic areas to achieve quick cleaning even in the absence of gravity force. The proportion of surface clean time of one full cycle duration on hybrid surfaces was as low as 32.2%–41.5%. Compared to complete superhydrophobic and bare copper surfaces, hybrid surfaces exhibited a significant enhancement on defrost efficiency due to larger three phase contact line length on evaporation-mediated surface cleaning performance, especially the SSH-3 surface, achieving the largest defrost efficiency within the present frost mass range.

Heat pumps (HPs) are energy-efficient space heating devices that are key to global carbon reduction and carbon neutrality. However, current commercial HPs have performance issues in cold climates where space heating is needed most, including low COP and high energy consumption of defrosting. Aiming to tackle these issues, a novel two-stage heat recovery heat pump (THRHP) is therefore developed to enable heat recovery from exhaust air for improving COP and preventing dramatic energy use during winter defrosting. The performance of THRHP was optimized in the laboratory by investigating its expansion valve opening and exhaust air fans situation. Finally, the experiment results showed the prototype provided a heating capacity of 32.3 kW, generating 4 m3/h hot water of 55 °C with COP of 2.57 at outdoor temperature of 0 °C, achieving 20.1% higher COP than the commercial HPs, while the efficient and quick defrosting process only consumed 0.46 kW and 4 mins under outdoor temperature on −6 °C. The results gave more insights into the characteristics of THRHP and obtained the optimal control strategies of THRHP for better performance, thus promoting the wide deployment of HPs and achieving the ambitious carbon-neutrality targets. [ABSTRACT FROM AUTHOR]

Frost formation in the heat exchangers of refrigeration systems is a well-documented phenomenon. This frost accumulation creates a thermally insulating barrier that can restrict, or even block, the airflow between fins, resulting in decreased efficiency and degradation of the food products. Several methods of frost detection and defrosting have been developed, although there is not an efficient mainstream method to measure and control frost formation. In previous works, the results of a small low-cost resistive sensor for frost detection were shown to be promising. This paper extends that research using computer vision to compare the results of this sensor with the frost formed on the heat exchanger, allowing for a better study of the sensor. This method allowed to trace and plot a frost formation curve of the sensor detected values.

• Novel flexible heat pump integrating heat storage with new defrosting mechanism. • Uninterrupted heating and constant capacity during the defrosting process. • Optimization of the storage temperature to maximize COP improvement. • Impact of defrosting time was investigated. • Up to 13.2% of COP improvement compared to a baseline heat pump with R1234yf. There has been growing interest in using air-source heat pumps as an alternative to potentially replace fossil-fuel-based heating technologies for heat decarbonisation. One of the technical issues that hinders the wide uptake of air source heat pumps is the decreasing energy efficiency caused by frequent defrosting operations under low ambient temperatures. Currently, the most widely used defrosting method is the reverse-cycle defrosting but this operation would have to interrupt the heating supply during the defrosting process. The authors recently proposed, developed, and demonstrated a flexible heat pump concept that recovers partial of the subcooled heat from the hot refrigerant exiting the condenser and stores it in an integrated thermal storage. The stored heat could later be used to save compressor power and defrosting applications. In this paper, we proposed an innovative method by using a multi-valve design of the flexible heat pump to achieve the defrosting function. In this new concept, defrosting is achieved by condensing the refrigerant inside the evaporator and simultaneously ensuring uninterrupted heating during the heat storage discharge process. A model has been established to study the heat pump performance during a full charge/discharge cycle of the storage. Results indicated that with R410a, R134a and R1234yf, the proposed flexible heat pump has the potential to respectively save up to 11.2%, 10.8% and 13.2% of compressor power, in comparison with a heat pump using the conventional reverse cycle defrosting method. Concurrently with the defrosting operation, the same heating capacity is ensured without interruption by the flexible heat pump. [ABSTRACT FROM AUTHOR]

A novel dual source vapor injection heat pump (DSVIHP) using exhaust and ambient air is proposed. The air exhausted from the building first releases energy to the medium-pressure evaporator and is then mixed with the ambient air to heat the low-pressure evaporator. A vapor injection (VI) compressor of two inlets is connected with the low and medium pressure evaporators. It's first time that a VI compressor is employed to recover the ventilation heat. The system can minimize the ventilation heat loss and provide a unique defrosting approach by using the exhaust waste heat. Fundamentals of the proposed DSVIHP are illustrated. Mathematical models are built. Both energetic and exergetic analyses are carried out under variable conditions. The results indicate that the DSVIHP has superior thermodynamic performance. The superiority is more appreciable at a lower ambient temperature. It has a higher COP than the conventional vapor injection heat pump and air source heat pump by 11.3% and 23.2% respectively at an ambient temperature of -10 °C and condensation temperature of 45 °C. The waste heat recovery ratio from the exhaust air is more than 100%. The novel DSVIHP has great potential in the cold climate area application.

The concept of defrosting, heating and partially melting a crystal-rich, weakly mobile or immobile magma (magmatic mush) has gained wide support from volcanological studies. This process has been called on as a means to promote eruption of crystal-rich (monotonous) dacites and also to permit extraction of felsic magmas, which may accumulate in the upper crust and erupt as crystal-poor rhyolite or trachyte. Most studies of the latter type of defrosting call on a conjugate plutonic part of the system from which the felsic melt was extracted. Although petrographic and geochemical features of defrosting are well described for eruptive rocks, few studies have investigated petrographic and geochemical features of plutons that indicate defrosting. The Jurassic Ashland pluton is a tilted intrusive complex exposed in southern Oregon and northern California, USA. The central part of the pluton, quartz monzodiorite (QMD), displays petrographic features (crystal fragmentation, widespread resorption, local concentrations of refractory minerals) characteristic of partial melting. This unit is intruded and overlain by biotite granite, which displays plagioclase cores identical in composition to plagioclase in the underlying QMD, resorbed titanite cores in plagioclase, and local subhedral to anhedral cores of alkali feldspar in poikilitic alkali feldspar crystals. Hornblende and biotite in the biotite granite display enrichments in Ti and Nb relative to these minerals in QMD, negating fractional crystallization as a petrogenetic process. Instead, these high Ti and Nb contents reflect significant partial melting of titanite in the QMD, thereby releasing high field strength elements to the defrosted biotite granite melt. The biotite granite magmas are thus interpreted as the melt-rich products of defrosting caused by intrusion of mafic–intermediate magmas into the QMD magma column. [ABSTRACT FROM AUTHOR]

This paper describes an approach for computing the specific heat capacities of logs stored for long in an open warehouse. It includes the heat capacities of the wood of non-frozen and frozen zones in the logs and of both the frozen free and bound water in these zones, also the capacities formed by the release of the latent heat of both the free and bound water during their crystallization, as well as the effective specific heat capacities of logs stored in an open warehouse at periodically changing air temperature. The approach is based on the solutions of 2D models of the temperature distribution in logs during their alternating heating and cooling. Results from a simulative study of 2D unsteady temperature distribution and all types of the specific heat capacities of beech logs with a diameter of 0.4 m, length of 0.8 m, moisture content of 60%, and initial temperature of 0°C and 20°C during their 5 days and nights continous alternating heating, cooling, freezing and defrosting in an open warehouse at sinusoidal change of the ambient air temperature with various initial and different amplitudes in the range from –25°C to 40°C are graphically presented and analyzed. [ABSTRACT FROM AUTHOR]

Temperature fluctuations cause significant harm to the quality of poultry meat and its food safety, both at various stages of storage and transportation, as well as sales. Repeated repeated defrosting and freezing lead to a violation of the integrity of cells or protein denaturation, which is accompanied by a change in the ratio of the forms of moisture binding to the product. In this regard, there is an urgent task of establishing the facts of thawing and freezing of poultry meat, determining the number of cycles of repeated freezing. This article is devoted to the development of a new express method for determining the number of cycles of freezing – thawing of a broiler at the stages of the life cycle of poultry products. As the number of «freeze-defrost» cycles increases, the peak area of the differential scanning calorimetry curve (DSC) decreases from 206.4 to 192.6 kJ/mol with electric stunning and from 168.6 to 151.5 kJ/mol with gas stunning, the melting peak temperature also decreases from 5.7 to 5.2 oC with electric stunning and from 5.0 to 4.0 oC with gas stunning. The DSC temperature program and recommendations for its use for monitoring broiler processing and storage processes accompanied by phase transformations of water have been developed.

The rapid anthropomorphic emission of greenhouse gases is contributing to global climate change, resulting in the increased frequency of extreme weather events, including unexpected snow, frost, and ice accretion in warmer regions that typically do not encounter these conditions. Adverse weather events create challenges for energy systems such as wind turbines and photovoltaics. To maintain energy efficiently and operational fidelity, snow, frost, and ice need to be removed efficiently and rapidly. State‐of‐the‐art removal methods are energy‐intensive (energy density > 30 J cm−2) and slow (>1 min). Here, pulsed Joule heating is developed on transparent self‐cleaning interfaces, demonstrating interfacial desnowing, defrosting, and deicing with energy efficiency (energy density < 10 J cm−2) and rapidity (≈1 s) beyond what is currently available. The transparency and self‐cleaning are tailored to remove both snow and dust while ensuring minimal interference with optical light absorption. It is experimentally demonstrated a multi‐functional coating material on a commercial photovoltaic cell, demonstrating efficient energy generation recovery and rapid ice/snow removal with minimal energy consumption. Through the elimination of accretion, this technology can potentially widen the applicability of photovoltaics and wind technologies to globally promising locations, potentially further reducing greenhouse gas emissions and global climate change. [ABSTRACT FROM AUTHOR]

An experimental study is proposed to analyze the frosting behavior of ice on a superhydrophobic surface. Ice accumulation can result in performance problems and safety concerns for transmission lines, marine and offshore structures, refrigeration, cryogenics, wind turbines, and heat-exchangers. Wetting properties are important for ice formation on surfaces from the liquid phase, where the water repellency of the surfaces could enhance their anti-icing effect. Such surfaces will be prepared by using a nanotextured coating. A thermal evaporation system will be proposed for nanocoating on a copper surface. The prepared surface produces a contact angle of 162° ± 2°. The Low Bond Asymmetric Drop Shape analysis is used to measure the contact angle using imageJ software. The heat-transfer performance of an evaporator is affected by frost formation. In this work, the heat-transfer coefficient of the surface will be estimated in the defrosting process. The effect of hydrophobicity and superhydrophobicity of surfaces, surface chemistry, morphology, and roughness scale will be studied on the defrosting process. In particular, wetting characteristics of the superhydrophobic surfaces revealed defrosting performance. The experiments will be performed in controlled environmental conditions. The anti-icing properties of superhydrophobic surfaces with different topography but similar chemistry are studied. [ABSTRACT FROM AUTHOR]

• A novel ejector-enhanced heat pump cycle with solar energy utilization is proposed. • Flexible switch in operating modes overcomes the intermittence of solar energy. • Continuous heating is ensured during defrosting without extra power consumption. • Energy, exergy, economic and environmental analysis are performed in typical cities. • The cycle is a promising solution to replace traditional heating methods. Energy, exergy, economic, and environmental analysis of a novel solar-assisted ejector-enhanced heat pump cycle (SEHPC) for space heating were conducted. Two flexible working modes have been designed to address the intermittency of solar energy, including the solar-assisted (SA) mode and the ejection-compression (EC) mode. Moreover, a hot liquid defrosting technique is employed to utilize the high-grade energy of the working fluid at the outlet of separator, ensuring the continuous heating and enabling defrosting without additional power consumption. The COP of the system in SA mode improved by 6.00–8.34 % within the studied ranges compared to that in EC mode. Exergy analysis indicates that the solar collector and turbomachinery are the primary components requiring optimization. Four cities situated in severe cold and cold regions were selected as typical application scenarios for system assessment. The analysis reveals that the COP increases with rising city latitude, whereas defrosting time, life cycle cost (LCC), primary energy cost (PEC), and pollutant emissions exhibit opposite trends. In comparison to traditional heating solutions, the LCC and PEC of SEHPC in Hailar are lower than those of direct electric heating (DEH) but higher than those of coal-fired boiler (CFB) and wall-hanging gas boiler (WGB). However, as the ambient temperature rises, these evaluation indicators of SEHPC approach or may even fall below those of CFB and WGB. Environmental analysis indicates that the pollutant emissions of DEH and CFB are 2.75–3.58 times and 1.42–1.85 times those of SEHPC, respectively, indicating the potential for SEHPC to replace traditional heating methods in the long term. [ABSTRACT FROM AUTHOR]

Air source heat pumps (ASHPs) have emerged as up-and-coming alternatives to fossil fuel heating systems due to their energy efficiency, environmental friendliness, and installation flexibility. However, the performance of ASHPs can be compromised by frost accumulation on the outdoor evaporator in low-temperature and high-humidity environmental conditions. This article reviews the recent advancements in anti-frosting and defrosting technologies of the ASHP, explicitly focusing on developments from 2018 to 2023. Firstly, the characteristics of frost layer growth and the influential factors that affect the frosting process were introduced. Next, various anti-frosting methods were examined, including modifications to the evaporator structure and surface wettability, optimization of operational principles, and design of operating parameters for ASHP systems. Finally, the recent developments in reverse cycle defrosting, hot gas bypass defrosting, hot liquid defrosting, and thermal storage defrosting methods were discussed. In addition, the defrosting control strategies based on machine learning, mathematical models, and image processing techniques were analyzed. The results demonstrate that the solar-assisted ASHP system and the superhydrophobic and superhydrophilic moistening heterosexual hybrid surfaces exhibit superior frost suppression performance and warrant further investigation. Regarding defrosting methods, utilizing multiple outdoor heat exchangers for rotational hot liquid defrosting and utilizing phase change materials for thermal storage defrosting can provide continuous room heating during the defrosting process, thereby improving thermal comfort during defrosting. Therefore, future defrosting methods should focus on achieving uninterrupted heating. This comprehensive review establishes a theoretical foundation and provides valuable references for selecting anti-frosting and defrosting methods in ASHPs, thus promoting their technological advancement. Studies of anti-frosting, defrosting techniques and their impact on Air Source Heat Pump (ASHP) from 2018 to 2023 are reviewed: • The characteristics of frost layer growth and the influential factors that affect the frosting process are summarized. • Two types of 4 anti-frosting techniques are classified and analyzed. • Four types of defrosting methods and 3 types of defrosting control methods are summarized. • Impact of frosting, anti-frosting and defrosting techniques on the energy performance of ASHP are identified. • The research focus of ASHP performance improvement in the whole cycle of heating, frost formation and defrost is pointed out. [ABSTRACT FROM AUTHOR]

Dust deposition on the fin surface of the outdoor heat exchanger seriously affects the operating efficiency of the air source heat pump (ASHP). Considering the operation characteristics of ASHP in summer for cooling and in winter for heating, a dust removal strategy is proposed based on superhydrophobic fin surface (SFS). In summer, the SFS is sprayed to remove dust by collecting the condensate water of air conditioning. In winter, by coupling the dust deposition with the condensation or frosting/defrosting phenomenon on SFS, the self-propelled motions of condensate droplets or the peeling off of the frost layer in defrosting is used to realize the dust removal. The experiment results show that the water spray on SFS has excellent dust removal performance, and the deposited dust is completely removed after 2 sprays. The dust is carried away by the jumping or gliding of the water droplets. The condensation has poor dust removal performance and takes long removal time. After several hours of condensation, the dust removal rate is 89.6 % and 40.0 % on SFS under different dust deposition levels. Due to the peeling off of the frost layer from the SFS at beginning of defrosting, the melting water at the bottom of the frost layer carries the dust away from the fin surface effortlessly. After 2 defrosting cycles, the dust removal rate reaches 99.6 %, while it is 50.1 % on the bare surface. Therefore, the strategy of dust removal by water spray in summer and defrosting in winter is suitable for ASHP. • Dust removal strategy is proposed based on superhydrophobic fin surface. • Strategy considers the operation characteristics of ASHP in summer and winter. • Water spray and defrosting methods show excellent dust removal performance. • Condensation method has poor dust removal performance and takes long removal time. • Dust removal by water spray in summer and defrosting in winter are suitable. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the influence of frozen storage time on the nutritional quality of boxed vegetables prepared with different cooking oils prior to freezing. Two types of vegetables, broccoli and Chinese cabbage, prepared with palm oil (PO) and soybean oil (SBO), were analyzed during their 12-month freezing storage (− 20 °C). The results showed that the nutritional quality of the frozen vegetable products was seriously affected during the storage period. During the storage period, some of the nutritional quality indexes, such as the vitamin C and total phenolic (TP) content, strongly deteriorated by 27–56% and 8.1–8.6%, respectively, whereas the nitrite content was increased by 10–14%. Additionally, a slight change was observed in the nitrate content. Concurrently, the oxidative degradation of the extracted cooking oils was also evaluated, and PO showed better oxidative stability than SBO. The peroxide value (PV), acid value (AV), malondialdehyde (MDA), and anisidine value (AnV) in PO increased less than those in SBO after 12 months at − 20 °C, and the PV, AV, MDA and AnV in PO were lower than those in SBO after frozen storage. On the basis of the findings from this study, PO was recommended as the best oil for the preparation of boxed frozen vegetables to reduce adverse effects during long-term storage. [ABSTRACT FROM AUTHOR]

Introduction. Low-temperature freezing technology extends the shelf life of perishable fruits as it causes a sharp slowdown in the biochemical and microbiological processes in frozen products. However, it cannot provide complete destruction of microorganisms. The present research featured the reaction of apricot microbiota to the technological techniques of shock freezing. The research objective was to study the effect of low-temperature freezing modes (t = –25, –30, and –35°C), storage time (3 and 9 months), methods, and defrosting modes (in air at t = 5 and 22°C; in water at t = 5, 16, and 22°C; under the effect of microwave irradiation) on the surface microflora of apricots. Study objects and methods. The experiment featured apricots of the varieties Uzden, Untsukulskiy Pozdniy, Honobah, Krasnoshchyokiy, and Shalakh. The microbiological profile of defrosted apricots was based on the State Standard. Results and discussion. Fast freezing at t = –25°C provided a better inhibition of epiphytic microflora than at t = –30 and –35°C: aerobic-mesophilic and optionally anaerobic microorganisms – by 65.2–68.6%, yeast – by 61.5–69.0%, and mold – by 59.3–68.4%, compared to their initial content on fresh apricots. During the initial period of refrigeration storage, the number of microorganisms decreased, while the subsequent nine-month storage (t = –18°C) led to a slight increase in microbiota. After nine months of storage, the number of microorganisms on defrosted fruits, depending on the variety, was the following: aerobic-mesophilic and optionally anaerobic microorganisms – 1.2×103–2.0×103 CFU/g, yeast – 14–26 CFU/g, and molds – 75–108 CFU/g. Defrosting of apricots by microwave irradiation resulted in a greater destruction of microorganisms than after traditional thawing in air and water. Conclusion. The results of microbiological studies indicate that the shock freezing technology ensures the production of quick-frozen apricots that meet the requirements of Technical Regulations of the Customs Union No. 021/2011.

During radio frequency (RF) thawing—tempering (defrosting) of frozen food products, some regions, mostly along the corners and edges, heat—thaw first due to the strong interaction of electric field and evolved heating leading to temperature increase. Resulting higher power absorption along these regions, compared to the rest of the volume, is the major cause of this problem. Besides, increase in temperature with phase change results in a significant increase of dielectric properties. This situation leads to runaway heating, which triggers the non-uniform temperature distribution in an accelerated manner. All these power absorption and temperature non-uniformity-based changes lead to significant quality changes, drip losses, and microbial growth. Based on this background, the objective of this review was to provide a comprehensive background regarding the most relevant and novel defrosting application studies using RF process, dielectric property data for frozen foods in the RF band, and novel mathematical modeling based computer simulation approaches to achieve a uniform process. Experimental and modeling studies were related with electrode position, sample geometry and size, electrode gap of the applied RF process, and the potential of charged electrode. Applying translational and rotational movement of the food product and the charged electrode vertical movement during the process to adjust the electric field and use of two-cavity systems and curved electrodes were also explained in detail. The data presented in this review is expected to give an insight information for further development of innovative RF thawing/tempering systems. [ABSTRACT FROM AUTHOR]

Reducing food waste demands improvements in refrigeration systems. Furthermore, the rise of temperatures worldwide demands more capable and efficient refrigeration equipment. One of the problems that affects refrigeration equipment is the accumulation of frost in the heat exchanger that reduces efficiency, and in extreme cases, blocks the air flow. Usually, defrosting is timed for the worst-case scenario, which results in many unnecessary defrosting operations that compromise the efficiency, and temperature stability in the refrigerated environment. This paper presents a low-cost resistive sensor’s reliability case studies, using several materials and configurations.