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This paper presents an experimental and numerical study of the freezing-thawing behavior of water in fully saturated sand. A relatively inexpensive and easily replicable experimental procedure was developed to simulate the freezing-thawing cycles in a medium-sized sand sample placed in a modified commercial freezer. By insulating the sides and bottom of the sample well, while allowing good thermal conductivity at the top of the sample, a nearly vertical advance of the freezing and thawing front was achieved. A series of freeze-thaw cycles were performed with higher and lower temperature gradients. A numerical multiphysics model, assuming an axially symmetric geometry based on the transient heat transfer during the phase transition, used a parametric approach to estimate the effective thermal properties of the sand-water-ice system. A good agreement between experimental and modelling results was shown, but slightly different parameter sets were obtained for each temperature gradient. The presented method could be a simple way to characterize the freeze-thaw process in natural and artificial porous materials. [ABSTRACT FROM AUTHOR]

The export of fresh‐cut durians has increased steadily. However, the shelf life of durians remains limited. The shelf life can be extended by decreasing the temperature of durian. Although the optimal temperature for storing fresh‐cut durians has been examined previously, few studies have addressed the efficiency of cooling systems. This study aimed to determine the parameters that affected the forced‐air precooling of 15 kg of fresh Monthong durians to 7°C, taking into account room temperature conditions of 6, 3.5, and 1°C. Experiments showed that the highest performance was attained with a precooling temperature of 1°C, which reduced the pulp temperature from 29 to 7°C in 266 min while using.83 kWh. After a 6‐h precooling time, the pulp maintained its firmness, color, and TSS, although its weight dropped by 2.30%. The pulp met the quality standards and exhibited only minor changes compared to fresh durians. Practical application: As a major exporter of fresh‐cut durians, Thailand faces the challenge of meeting growing demand while ensuring efficient precooling and product quality. Although small and medium‐sized businesses commonly use commercial freezers for durian chilling, the impact on quality remains uncertain. Precooling, which rapidly lowers the temperature before storage or shipment, is essential for maintaining cold chain efficiency. However, research on the effects of precooling specifically for fresh‐cut durians remain limited. This investigation aims to fill the gap in knowledge by studying the preservation effects of precooling at different temperatures (6, 3.5, and 1°C) and placements. The findings could greatly benefit small and medium‐sized enterprises by improving their ability to precool fresh‐cut durians using commercial refrigerators. This, in turn, can enhance the export value of durians and boost Thailand's agriculture revenue. By optimizing precooling efficiency and product quality preservation, Thailand can strengthen its position as a leading exporter of fresh‐cut durians. [ABSTRACT FROM AUTHOR]

The United States Food and Drug Administration (U.S. FDA) has identified improper (“slow”) cooling as an important contributing factor in foodborne illness outbreaks. The efficacy of post-thermal treatment cooling techniques on controlling surrogate Escherichia coli growth in taco meat, chili con carne with beans, and low-sodium marinara sauce was evaluated. Each product was cooked to 73.9°C, portioned to 2- and 3-inch depths in stainless steel steam table pans, and cooled to 60°C ± 5°C before inoculation with E. coli. Pans were prepared with different cover methods to allow or restrict air exposure and then placed inside a -20°C commercial walk-in freezer or situated in ice water baths inside a 4°C commercial walk-in refrigerator. Product temperatures were recorded for 24 hours. Microbial populations were enumerated at 0, 4, 8, 12, and 24 hours. Temperature data for taco meat and chili con carne with beans revealed that few cooling methods met the 2017 FDA Food Code cooling criteria, while data for low-sodium marinara sauce showed that no cooling method met the Food Code chilling criteria. Population changes were < 0.50 log10 CFU/g over 24 hours in all products, indicating that all cooling methods were low risk for microbial proliferation and were therefore effective at controlling E. coli within these products. [ABSTRACT FROM AUTHOR]

The global commercial refrigeration equipment market size was valued at USD 33.53 billion in 2020. It is expected to expand at a compound annual growth rate (CAGR) of 4.2 % from 2021 to 2028. Furthermore, factors such as regulatory pressures, shift to lower Global Warming Potential (GWP) refrigerants, technological breakthroughs, and the ability to cater to the ever-changing consumer behaviors are also anticipated to create promising growth opportunities for the market. Environmental issues related to high GWP refrigerants, including global warming and ozone depletion, are compelling commercial refrigeration equipment manufacturers to seek alternatives. The rising demand for advancements in technologies that can help reduce hazardous gas emissions has led to the market participants increasingly equipping their products with modern and magnetic refrigeration systems. Apart from this, these systems improve the energy efficiency of refrigeration equipment, bringing down the cost of operation. The analysis of the structure and heat loads of the commercial freezer with monitoring of temperature distribution on the body of heat-insulating fences and in the internal volume during operation of the system is carried out. The heat loads on the body depending on the structure of the freezer are substantiated on the example of the M400S commercial freezer model. The obtained results allow to significantly reduce the time of selection and calculation of the dimensions of a given model range of equipment for product storage, by developing a standard calculation taking into account the climatic class in which the equipment will be used, and taking into account experimental data obtained during the experiment. [ABSTRACT FROM AUTHOR]

Refrigeration systems can experience operating faults that negatively impact their performance, such as reducing their ability to maintain the temperature setpoint, increasing energy consumption, or reducing the life of the equipment. To better understand the impacts on the physical operating characteristics of a system, a numerical model can be used. However, fully physics-based models require significant computational effort and detailed system information that is typically unavailable; whereas data-driven models require a prohibitively large amount of test data. In this paper a gray-box model is described, using a semi-empirical approach from the literature. It combines into a complete cycle the models for each component: compressor, heat exchangers, pipelines, expansion valve, and liquid line receiver. A set of 35 test data from laboratory experiments on a commercial walk-in freezer was used for training and validating the model. The liquid line receiver was found to provide particular challenges for charge estimation, but the overall model performs quite well and is able to predict the effects of faults on most operating variables with reasonable accuracy. [ABSTRACT FROM AUTHOR]

Isochoric freezing, different from isobaric (conventional) freezing, allows for storage below freezing temperatures without significant damage from ice formation. While several types of tissues have been successfully stored in sub‐zero isochoric conditions, it is unknown how isochoric freezing affects pathogenic microorganisms. Thus, the objective of this study was to investigate the survival of Salmonella Typhimurium and Listeria monocytogenes at below freezing storage (<0°C) in isochoric conditions. Tested conditions included storage at −4, −7, and −15°C for 24 hr and at −15°C for 1, 2, 3, 6, 12, and 24 hr. A comparison of bacterial survival during isobaric freezing was included with every trial. Additionally, bacterial cells were examined for morphological damage using transmission electron and field‐emission scanning electron microscopes. Isochoric freezing at −15°C for 24 hr reduced both species of bacteria down to unrecoverable levels and maximum efficacy achieved after the 6 hr timepoint for L. monocytogenes and the 12 hr timepoint for S. Typhimurium. When viewed using electron microscopy, S. Typhimurium cells were noticeably disfigured with regions of cytosol separated from the cell wall. The results of this study demonstrate that isochoric freezing is capable of substantial levels of pathogen reduction. Unlike conventional nonthermal interventions, isochoric freezing does not require additional devices such as elevated pressure machines or pulsed electric fields and can be achieved with simple, inexpensive, rigid closed volume containers such as household freezers or commercial cold storage facilities. [ABSTRACT FROM AUTHOR]

The Integrated Research Biobank (IRB) at the Institute of Clinical Chemistry and Laboratory Medicine (IKCL) is the central biobank resource of the University Medicine Greifswald (UMG) for all biological materials collected within the framework of clinical and experimental studies carried out by internal and external researchers. The IRB is a core unit of the UMG and focuses on collection, processing and storage of mainly liquid biomaterials, e.g. blood, urine, saliva or swaps in established workflows and thereby securing highest quality standards. Aliquots are usually stored at -80°C in one of the two fully automated LiCONiC biorepositories or, if necessary, in one of the -80°C freezers. Up to now, the IRB stores more than 1.1 million liquid aliquots and the collection grows continuously. Currently, the storage capacity of the IRB is limited to 3 million aliquots. [ABSTRACT FROM AUTHOR]

The article discusses need to understand scraped-surface freezer, which is at the core of ice cream production. It mentions that modem manufacturing processes employ advanced control to ensure efficient operation in relation to frozen desserts. It reveals that controlling the creation of the ice phase is critical to product quality and shelf life.

Highlights • The malfunction behavior of the ejector in EARC system was experimentally investigated. • The effects of the ejector geometries on the pumping failure behavior were obtained. • Optimal ejector geometry existed with respect to the operation reliability. Abstract In this paper, the dynamic failure of the two-phase ejector in a modified auto-cascade freezer system was experimentally investigated in the pull-down process. The effects of the critical ejector geometries including the nozzle throat diameter, mixing section diameter and nozzle exit position on the ejector performance were discussed in detail. The entrainment ratio and pressure lift ratio were used to evaluate the ejector performance. The malfunction behaviors of the pressure rise and fluid entrainment at different ejector geometries were analyzed. The results showed that two typical malfunction modes, i.e., pressure lifting failure and refrigerant entrainment failure, occurred in the pull-down process when ejector geometry were improperly adopted. The operation reliability of the ejector was sensitive to the nozzle throat diameter. Low mass entrainment ability and poor mixing effect for the mixing fluids were the main reasons of pumping failure for the ejector at undersize and overlarge mixing section diameters, respectively. Pressure lifting failure was prone to occur at smaller NXP, and the pulsation of the pressure lift ratio became obvious at large NXP when the secondary fluid was at two-phase state. The variation of temperature at the secondary fluid inlet was an important symbol of detecting the reverse flow of the primary from the secondary fluid inlet. The ejector with throat diameter of 0.8 mm, mixing section diameter of 3 mm and NXP of 6 mm was proposed in consideration of the ejector operation reliability in the pull-down process, and the time-average value of the pressure lift ratio could reach 2.197 at the entrainment ratio of 0.663. [ABSTRACT FROM AUTHOR]

Heat pumps and refrigerators are two systems with different usage, but same working principles. Generally, HPs work in steady state condition and specific thermodynamic cycle, but refrigerator or freezer apparatus have variable cycle and work in the unsteady condition. In this study, two different data sources are gathered to analyze thermodynamic differences between two mentioned systems. Initially, an existing heat pump unit is analyzed in different working conditions with different refrigerants and then the unit is converted to a refrigeration device to compare their thermodynamic conditions and treatments. Thermodynamic laws, COP value and efficiency, compressor power consumption, optimum charge amount, and flow rate of secondary fluid are main parameters which are considered to compare heat pump and refrigerator performances by using several refrigerants including R134a, R407c, R22, and R404a. In the case of freezer mode, entropy reduction in compressor and COP L drop to very low values are other substantial issues discussed in this research. It was also revealed that, optimal charge amount of the freezer is 15–25% lower than that of the system when works in HP mode. Experiments showed that, in some cases COP of the heat pump was even more than 100 times greater than that of the freezer. [ABSTRACT FROM AUTHOR]

The presented work studies the use of a commercial freezer to produce ice efficiently by photovoltaic energy. An innovative control unit was developed which adapts the operation of the compressor to the availability of solar energy. The proposed solar ice-maker was analysed with the help of simulations and experiments for the location of Sidi Bouzid in Tunisia. A design methodology was presented to optimize the solar energy supply system for a target ice production of 12 kg ice per day. A PV array of 600 Wp and battery bank of 65 Ah capacity at 24 V were selected. The one-year simulation results showed that the ice-maker, which stores a total of 50 kg ice, is able to deliver the target ice production for 89% of the days of a typical year at the selected location. Additionally, a testing bench equipped with PV simulator and climate chamber was implemented in order to assess the ice-maker experimentally under two representative weather profiles. Under repeated unfavourable weather conditions, an autonomy of 5 days was concluded from the experiments. [ABSTRACT FROM AUTHOR]

PBSC products for auto- and allografting can be cryopreserved in liquid nitrogen with controlled-rate freezing until their use. Alternatively, they can be stored at −80 °C in a mechanical chest freezer, but it remains to be clarified whether PBSCs can be stored for the long term. We evaluated viability and functions of PBSCs cryopreserved for more than 10 years with this simplified method. Although recovery rate and viability of CD34+ cells were significantly decreased, myeloid differentiation potential and in vivo reconstitution and self-renewal potential of CD34+ cells in a xenogeneic engraftment assay were maintained for more than 10 years. These results indicate that PBSCs can be stored at −80 °C for years. Although accumulation of clinical engraftment data is required to confirm our results, this simplified cryopreservation will thus meet the increasing worldwide demand for PBSC transplantation in a region with limited resources. [ABSTRACT FROM AUTHOR]

In this work, a discussion on a methodology to optimize the performance of a commercial freezer by using a simulation tool is presented. In order to provide a practical tool for deciding the best combination of refrigerant charge and capillary tube diameter, the results of the numerical studies are shown in the form of two-dimensional maps. The usefulness of this type of representation lies in the possibility of selecting the best operating point of the system, taking into account not only the efficiency or the power consumption but also the technical constrictions imposed by parameters such as the suction line temperature, the condenser subcooling, the evaporator superheat, and the run-time ratio. The discussion leads to the conclusion that the useful performance map is drastically reduced when all the operation requirements must be satisfied. Once the system design had been optimized, an additional numerical study, aimed at identifying the influence of the external conditions on the system behavior, was performed. The results show that the performance reduction can be effectively minimized modifying the refrigerant charge. [ABSTRACT FROM AUTHOR]

Abstract: The concentration of H2O and the pressure in the headspace of vials are simultaneously measured by a tunable diode laser sensor based on absorption spectroscopy techniques. The 7168.437cm−1 spectral line of H2O is chosen as the sensing transition for its strong absorption strength and being reasonably far away from its neighboring molecular transitions. In order to prevent interference absorption by ambient water vapor in the room air, a difference between the measured signal and the referenced signal is used to calculate the pressure and H2O concentration in the headspace of vials, eliminating the need for inert gas purges and calibration with known gas. The validation of the sensor is conducted in a static vial, yielding an accuracy of 1.23% for pressure and 3.81% for H2O concentration. The sensitivity of the sensor is estimated to be about 2.5Torr for pressure and 400ppm for H2O concentration over a 3cm absorption path length respectively. Accurate measurements for commercial freeze-dried products demonstrate the in-line applications of the sensor for the pharmaceutical industry. [Copyright &y& Elsevier]

A laboratory-scale freeze dryer was adapted to allow control of the heat supply and on-line monitoring of sample weight during drying under vacuum condition. Several tests were carried out to verify the reliability of the developed system. The system was also tested with 10-mm-thick banana slices, obtaining the fruit drying rate, at different sample holder plate temperatures including 20 and 30°C as well as an unheated plate. The system presented in this work represents a low-cost, flexible, and easy-to-assemble piece of equipment that allows the study and optimization of the freeze drying of foods. [ABSTRACT FROM AUTHOR]

Highlights: [•] Parametric analysis of heat exchangers volumes, charge, regenerative length of the capillary tube. [•] The optimized configuration reduces the charge with negligible effects on energy consumptions. [•] The replacement of R404A with propane reduces energy consumption. [Copyright &y& Elsevier]

A domestic refrigerator and freezer use a condenser as a heat exchanger. A conventional refrigerators and freezers use a wire on tube condenser. A well-designed domestic refrigerator or freezer provides low energy consumption. Improving of the condenser heat transfer performance is one of the most important ways for reducing the energy consumption. Therefore, this study perform determination of the influences of pass distance and pass quantity on condenser cooling performance in order to improve the energy efficiency of upright freezer. Experiments were carried out on a real upright freezer using R600a as the refrigerant to obtain the condenser performance. Seven prototypes have been manufactured and several experiments have been done to find cooling performance. Energy consumption test results in the upright freezer depending on 3 different pass distance showed that shelf temperatures inside the compartment decrease as the distance between tube passes on the condenser increases. According to pass quantity experiments of the condenser, 24 pass condenser has been provided the best cooling performance with the lowest energy consumption compare to the other pass quantities [ABSTRACT FROM AUTHOR]

Abstract: Storage and transport of temperature sensitive products have become an important issue worldwide. The enhancement of thermal performance of cold application is under investigation and implementing thermal energy storage (TES) systems by using phase change materials (PCM) is one of the solutions to better storage. Hence, the selection of the suitable PCM for each specific application is an important matter. In this paper, a TES system using PCM for low temperature applications such as commercial freezers is studied. A set of PCM formulations based on ammonium chloride – water binary system were tested and analyzed to provide information useful for the selection of PCM with regards to their melting range, latent heat, stability under cycling, and cost. Thermal cycling was conducted to determine the thermal reliability of the PCM and the thermal properties were determined using differential scanning calorimetry (DSC) analysis. [Copyright &y& Elsevier]

The quality and shelf life of whole and gutted Indo Pacific king mackerel stored in freezer were studied. The changes in the fish were investigated by sensory assessments, chemical analyses. The sensory scores of uneviscerated and gutted Indo Pacific king mackerel stored in -10 °C were 20 days. pH value of Indo Pacific king mackerel fillet was increased (P < 0.05) with storage time, indicating that alkaline compounds were accumulated through autolytic activities or microbial metabolism. Sensory properties of samples were evaluated according to hedonic scale. General appearance, odor, color and texture were used as criteria for acceptability. The shelf life of Indo Pacific king mackerel fillets stored at-10°C ranged 8 - 18 days considering fish freshness. [ABSTRACT FROM AUTHOR]

Abstract: An investigation into the effect of phase change material (PCM) panels placed against the internal walls of a freezer during repeated power loss every 24h over a 2week period was conducted. Comparisons of the freezer air temperature and product temperature in a freezer containing PCM panels showed lower temperature fluctuations than in a freezer without PCM. Product analysis was also conducted by measuring the drip loss in 1×1cm cubes of bovine muscle (Musculus semimembranosus) and the ice crystal size in 1L blocks of vanilla ice cream. Drip loss was measured by centrifuging the samples and weighing the drip collected. Analysis of ice crystal diameters was conducted by microscopy and an image analysis tool. Drip loss in meat was found to be lower and ice crystal sizes in the ice cream were found to be smaller in the freezer with PCM compared to without PCM. [Copyright &y& Elsevier]

This study examines the theory and forensic engineering analysis of multiple freezer sub-floor heating systems, the accidental event that lead to failure of each, an Analytical Model to determine the viability of a corrective action approach, those results, the ensuing successful repair, and the resulting Legal Complaint. The case presented involves a food distribution warehouse facility operation located in Massachusetts which utilized a resistance heating element sub-floor heating system in the building's 65 foot by 130 foot freezer section (freezer height 40 feet). Resistance heat was used to precisely control the freezer sub-floor to a temperature of 34°F. This level of control allowed the freezer floor surface to be kept as cold as possible, while at the same time, keeping the sub-floor above freezing so that disruptive frost wouldn't develop. An incident occurred in which the floor heating system was damaged beyond repair and an entirely new heating system was installed. The new heating system experienced a catastrophic failure after a few months of operation, resulting in severe damage to the facility. [ABSTRACT FROM AUTHOR]

Background aims. An optimal cooling rate is one of the critical factors influencing the survival of cells during cryopreservation. We describe a novel device, called the box-in-box, that has been developed for optimal cryopreservation of human hematopoietic stem cells (HSC). Methods. This work presents the design of the device, a mathematical formulation describing the expected temperature histories of samples during the freezing process, along with actual experimental results of thermal profile tests. In experiments, when the box-in-box device was transferred from room temperature to a −80°C freezer, a cooling rate of −1 to −3.5°C/min, which has been widely used for the cryopreservation of HSC, was achieved. In order to evaluate this device further, HSC cryopreservation was compared between the box-in-box device and a commercially available controlled-rate freezer (CryoMed). Results. The experimental data, including total cell population and CD34+ hematopoietic progenitor cell recovery rates, viability and cell culture colony assays, showed that the box-in-box worked as well as the CryoMed instrument. There was no significant difference in either survival rate or the culture/colony outcome between the two devices. Conclusions. The box-in-box device can work as a cheap, durable, reliable and maintenance-free instrument for the cryopreservation of HSC. This concept of a box-in-box may also be adapted to other cooling rates to support cryopreservation of a wide variety of tissues and cells. [ABSTRACT FROM AUTHOR]

The effect of conventional continuous freezer parameters [mix flow (L/h), overrun (%), drawing temperature (°C), cylinder pressure (kPa), and dasher speed (rpm)] on the hardness of ice cream under varying measured temperatures (-5, -10, and -15°C) was investigated systematically using response surface methodology (central composite face-centered design), and the relationships were expressed as statistical models. The range (maximum and minimum values) of each freezer parameter was set according to the actual capability of the conventional freezer and applicability to the manufacturing process. Hardness was measured using a penetrometer. These models showed that overrun and drawing temperature had significant effects on hardness. The models can be used to optimize freezer conditions to make ice cream of the least possible hardness under the highest overrun (120%) and a drawing temperature of approximately -5.5°C (slightly warmer than the lowest drawing temperature of -6.5°C) within the range of this study. With reference to the structural elements of the ice cream, we suggest that the volume of overrun and ice crystal content, ice crystal size, and fat globule destabilization affect the hardness of ice cream. In addition, the combination of a simple instrumental parameter and response surface methodology allows us to show the relation between freezer conditions and one of the most important properties-hardness-visually and quantitatively on the practical level. [ABSTRACT FROM AUTHOR]

We have analysed sets of capillary rheometry data (0.3 s-1 ≤ Yapp ≤ 360 s-1) for a commercial ice cream as it flowed from a freezer on an industrial flow line. Pressure drop measurements were used and particular attention was paid to viscous dissipation effects. A semi-analytical model presented by Bird in 1955 indicated that over one third of the data points were subject to local wall heating, which was consistent with available temperature measurements. The filtered data were used to construct a viscosity function which, when implemented in a detailed CFD simulation of the flow, predicted the observed flow curve behaviour. The results demonstrate that viscous dissipation can be significant in ice cream and that interpretation of this behaviour in terms of wall slip is erroneous. [ABSTRACT FROM AUTHOR]

Abstract: Air-cooled centrifugal chillers are commonly used in commercial buildings but their performance analysis is lacking. This paper investigates the part load performance of the chillers via a thermodynamic model. The model was validated using a wide range of operating data from an existing chiller with specific settings of outdoor temperature and condensing pressure in controlling the condensing temperature. The validated model was developed specifically to ascertain the maximum coefficient of performance of chiller (COP) together with the strategy for optimizing the condensing temperature under various operating conditions. It is found that the highest COP occurs at a part load ratio (PLR) of 0.71–0.84, depending on the outdoor temperature and the control of condensing temperature, rather than at full load. Yet the chillers operating at such part load conditions will cause extra energy used for the early staging of chilled water pumps. To minimize the overall chiller plant energy consumption, it is still preferable to implement chiller sequencing based on the full load condition than on the aforementioned PLRs. The results of this paper present criteria for implementing low-energy strategies for operating air-cooled chillers satisfying a given building cooling load profile. [Copyright &y& Elsevier]

The article features several equipment and supplies in the chemical industry, including the 809 Titrando titrator from Metrohm, the BenchCel handling system from Velocity11 and Thermo Scientific Revco PLUS upright freezers from Thermo Fisher Scientific.