Refrigeration Research Articles

Experimental measurement and expression of atmospheric ice Young's modulus according to its density

Ice properties are hard to define and vary significantly in literature. While some of this variation can be attributed to different testing methods, the authors believe that most of this variation comes from the nature of the ice accretion itself. To address the problematic of scattering in mechanical properties values, a new approach is proposed which consists of expressing the behavior of atmospheric ice according to its density. Thanks to a hybrid experimental/numerical approach, the accurate measurement of the Young's modulus of atmospheric ice can be done. Ice samples are generated in both cold room and wind tunnel and at many different test conditions. The results obtained in this study confirm the validity of this new approach and gives a concrete relationship between the Young's modulus and the ice density. Finally, the relevance of using porous material hypothesis to explain the relation and the results domain of validity are discussed.

Cold stress resilience of Iranian olive genetic resources: evidence from autochthonous genotypes diversity.

Olive (Olea europaea L.) is one of the most cultivated tree species in Iran. This plant is characterized by its tolerance to drought, salt, and heat stresses while being vulnerable to frost. During the last decade, periods of frost have occurred several times in Golestan Province, in the northeast of Iran, which caused severe damage to olive groves. This study aimed to evaluate and individuate autochthonous Iranian olive varieties with regard to frost tolerance and good agronomic performance. For this purpose, 218 frost-tolerant olive trees were selected from 150,000 adult olive trees (15-25 years old), following the last harsh autumn of 2016. The selected trees were reassessed at different intervals, i.e., 1, 4, and 7 months after the cold stress in field conditions. Using 19 morpho-agronomic traits, 45 individual trees with relatively stable frost-tolerance were reevaluated and selected for this research. Ten highly discriminating microsatellite markers were used for the genetic profiling of the 45 selected olive trees, and, ultimately, five genotypes with the highest tolerance among 45 selected ones were placed in a cold room at freezing temperatures for image analyses of cold damage. The results of morpho-agronomic analyses evidenced no bark splitting or symptoms of leaf drop in the 45 cold-tolerant olives (CTOs). The oil content of the cold-tolerant trees comprised almost 40% of the fruit dry weight, highlighting the potential of these varieties for oil production. Moreover, through molecular characterization, 36 unique molecular profiles were individuated among the 45 analyzed CTOs that were genetically more similar to the Mediterranean olive cultivars than the Iranian ones. The present study demonstrated the high potential of local olive varieties, which would be promising and more suitable than commercial olive varieties, with regard to the establishment of olive groves under cold climate conditions. This could be a valuable genetic resource for future breeding activities to face climate changes.

Performance Assessment of Evaporative-Cooled Storage System in Short-Term Storage of Fruit Vegetables during Transportation

The study presents the performance and potential of an evaporative-cooled storage system for the short-term storage of fruit vegetables during transportation. The evaporative cooler, storage unit, power supply, control panel, and real-time data monitoring system are the components of the evaporative-cooled storage system. In this study, the system performance was assessed in terms of the cooling profile of the storage unit (temperature and relative humidity profiles), and postharvest quality of the selected fruit vegetables (chili, tomato, and long bean) for the fresh market. Three storage treatments for the selected fruit vegetables were investigated, i.e., evaporative-cooled storage unit (T1), ambient room (T2), and cold room (T3). The average temperature inside the storage unit was T3 < T2 < T1. T1 demonstrated RH of > 90 %, in agreement with recommended RH for vegetable storage. Post-five-hour storage treatments, vegetables stored under T1 exhibited the least weight loss as compared to T2 and T3. The application of an evaporative-cooled storage system provided potential to preserve fruit vegetable postharvest quality during transportation.

Simplified test bench for experimental investigations of space heating appliances

The energy transition requires efficient space heating appliances. In that context, it is common that thermodynamics laboratories are asked to conduct experimental investigations on those appliances to establish or verify their performance. This paper aims to offer and report an example of a very simple test rig that allows for controlling both the space heating water flow rate and the space heating return temperature. Space heating depart temperature thus depends on those two controlled parameters as well as the heat transfer rate provided by the space heating appliance, based on its settings. The test rig described in this paper has been used to conduct experimental studies on residential Solid Oxide Fuel Cells used as micro-cogeneration units. It has the advantage of being reproductible or reused with other residential space heating appliances. It can easily be adapted for refrigeration appliances testing or even heat exchanger characterization Also, the test rig controlling the space heating flow rate and working temperature implies an approximative cost of only about 1 k€ (with 2021 hardware prices, without the space heating appliance to be tested).

Influence of long-distance air transport conditions on horticultural product quality: Case study of fresh mango shipment from Thailand to France

Four instrumented boxes of mangoes Mangifera indica L. cv. “Nam Dok Mai” were shipped from Bangkok, Thailand, to Paris, France, without control of the boxes’ positions on the aircraft. Two boxes were shipped via a direct flight and two boxes were shipped via an indirect flight. For each box, the internal air temperature, the external air temperature and relative humidity and surface temperature of two fruits were recorded throughout the supply chain from a packing house in Thailand to a storage room in France. A maximum fruit temperature of 33 °C (during transport from an orchard to the packing house) and a minimum fruit temperature of 8 °C (in a cold room of the logistics company following arrival at the airport in France via the indirect flight) were observed. The slight temperature difference between the air and the fruit surface temperature (< 1 °C on average) for both direct and indirect flights suggests that the air was stagnant inside the box and, thus conduction was the main heat transfer mode. Models of product temperature, mass loss, and peel color changes throughout the supply chain were developed. The numerical and the experimental values were in good agreement. These models were able to predict the product mass loss and peel color evolution as a function of a supply chain scenario.

Reasonable kitchen space for urban residences: based on an investigation in Beijing

ABSTRACT Undersized space in kitchens remains a widespread and enduring problem in urban residences in China. However, no consensus exists on the area a satisfactory kitchen should take up and the causes of an undersized kitchen are still not sufficiently understood. This study examined reasonable spatial indices for kitchen design from the perspective of user satisfaction, based on 80 kitchens selected from multi-family residences in Beijing, People’s Republic of China. Data were collected using on-site measurement and face-to-face questionnaires, including spatial features, household structure, cooking habits, possession of appliances and residents’ binary judgement about the kitchen area. Factors associated with residents’ kitchen area perception were explored using correlation analysis, while the reasonable design indices were proposed by scatter diagram analysis. This study confirmed the influence of floor space and width of the kitchen and recommends 5.11–6.10 m2 and 1.71–2.00 m as a reasonable scope for the respective dimensions. It also demonstrates that the area requirement increased in families with higher cooking frequency and decreased in youthful households and suggests that the accommodation of the refrigerator and large appliances should be considered in kitchen area allocation.

Reducing the Scrap Rate on a Production Process Using Lean Six Sigma Methodology

The aim of this case study is to implement the Lean Six Sigma methodology to reduce the scrap rate of the edge-bending process of a metal door case used in the assembly process of refrigeration appliances. This study was initiated because the assembly process of refrigerators does not work at maximum capacity due to the scrap that occurs for this component. Losses have direct effects on a company’s profits and on its competitiveness on the market. This research provides an overview of the identification of the most optimal and useful tools that can be used in each context; this will help to establish a protocol which can be applied in similar contexts. Although this study is limited to one process, the results will have direct effects on the assembly line of the organization. The purpose of this study is to increase the capability of the process and to improve the efficiency of the delivery of the component parts to the assembly line. This case study provides further evidence of the effectiveness of the use of the Six Sigma methodology in identifying and reducing scrap rates.

Influence of foliar spray and post-harvest treatments on head yield, shelf-life, and physicochemical qualities of broccoli.

Rapid senescence is the key factor in the deterioration of post-harvest shelf-life in broccoli heads. This study evaluates the head yield and its related traits, and physicochemical attributes of broccoli under four foliar sprays of mineral nutrients (B, Zn, Mo, and B + Zn + Mo) with control. The interaction effects of shelf-life and physicochemical attributes of broccoli for these five pre-harvest and five post-harvest storage treatments (LDP bag, HDP vacuum pack, 2% eggshell powder solution, 2% ascorbic acid, and control) both at cold storage and room temperature were evaluated with three replications. The significantly higher marketable head yield of 28.02 t ha-1, maximum gross return [(Bangladesh Taka (BDT 420300 ha-1)], net return (BDT 30565 ha-1), and maximum benefit-cost ratio (BCR) of 3.67 were obtained from the pre-harvest foliar application of B + Zn + Mo in broccoli. Pre-harvest foliar spray of combined nutrient B + Zn + Mo and post-harvest treatment high-density polyethylene (HDP, 15 μm) vacuum packaging efficiently improve post-harvest physicochemical attributes, viz., compactness, green color, texture, carbohydrates, fats, energy, antioxidants, vitamin C, and total phenols in broccoli head compared to the rest of the treatment combinations. In addition, this treatment combination also confirmed a maximum shelf-life of 24.55 days at cold storage [relative humidity (RH) 90-95% and 4°C] and 7.05 days at room temperature (RH 60-65% and 14-22°C) compared to the rest of the treatment combinations. Therefore, we recommend a pre-harvest foliar spray of combined nutrient elements B + Zn + Mo and an HDP (15 μm) vacuum post-harvest packaging for the maximum benefits for both farmers and consumers to get the best head yield, anticipated physicochemical attributes, and maximum shelf-life of broccoli.

Short Report on the Excavations in the Legionary Fortress of Brigetio in 2021-2022

While the legionary fortress of Brigetio is one of the key sites in the province of Roman Pannonia, its inner structure and buildings are almost unknown. Although the retentura of the legionary fortress is almost entirely covered by modern buildings, the praetentura can be researched using remote sensing methods. Over the past few years, systematic excavations took place in the praetentura, based on results of the geophysical surveys. A large building complex was identified as the bath of the legionary fortress, with an area of at least 4,000 m2. In the excavation seasons 2021 and 2022, about 1,200 m2 of the bath was unearthed. Several cold and hot rooms, pools, sewers, hypocaust systems and praefurnia were found, yielding abundant find material. In the present state of research, the chronological periods and building phases of the bath are mostly unknown. The only chronological data comes from the in situ stamped bricks of the Legio XI Claudia, dating the earliest period of the bath between AD 101 and 105, which was also the earliest period of the legionary camp. From the Late Roman Period, some tegulae with the names of Lupicinus tribunus and Frigeridus dux have been preserved, which indicate building activity in the last third of the 4th century AD.

Beef handling practices at Abattoirs and Butcher shops in Uganda: implications for meat safety and health of consumers

Proper beef handling contributes to achieving sustainable development goals 3 (good health and well-being) and 12 (sustainable consumption and production patterns). This is because it ensures the safety of meat and consumers’ health. However, the meat sector is still underdeveloped in most African countries. In addition, there is limited research addressing meat safety challenges. In Uganda particularly, in the recent past, there was whistle-blowing over contaminated beef on the market, indicating a loophole in food safety. Despite this, studies focusing on beef handling practices have remained scanty. Thus, this study aimed to examine beef handling practices at the abattoirs and butcher shops in Uganda's Central, Western, and Eastern regions. A mixed-methods approach was employed to collect data through a survey, in-depth interviews, and on-site observations. Findings revealed that beef handling practices were poor at abattoirs and butcher shops and that most facilities for safety measures were lacking or inadequate. Only 3% of the respondents had cold room storage facilities, and meat spoilage was relatively high (85.3%). Appropriate knowledge of meat safety among abattoir and butcher operators was inadequate, contributing to low compliance with food safety guidelines. Inappropriate handling practices and poor handling facilities may put consumers at a health risk. The study recommends that responsible authorities should ensure compliance mechanisms and sensitization initiatives are prioritized.

Feasibility assessment of a CO2 based power, cooling, and heating system driven by exhaust gas from ocean-going fishing vessel

The research presents a novel CO2 transcritical trigeneration system for ocean-going fishing vessel. Cascade ejectors are employed to decrease the exergy destruction caused by the dual evaporators, enhancing the cooling capacity of the system. By recovering the waste heat of exhaust, the system is designed to cover refrigeration demand of a refrigerated sea water (RSW) tank, the domestic hot water demand at different temperature levels onboard, as well as the power for sailing. The performance of the system is investigated from both thermodynamic and economic perspectives. The feasibility of applying the proposed system to replace the original refrigeration system of a RSW tank is evaluated in different periods, including prechilling, chilling, and chilling maintenance. Analysis show that sufficient cooling can be provided to a RSW tank under most typical engine operation modes, which is significantly influenced by the split ratio and refrigeration capacity ratio. Constraint multi-objective genetic algorithm under engine load of 100% is conducted to determine the maximum potential of the system under the optimum working condition and ensure the smooth operation of the system under all typical engine load. It is estimated that a cooling capacity of 619.9 kW can be offered to the RSW, and the cooling provided to the cold room (502.8 kW) can realize the freezing of 25018 kg fish. After covering the power consumed by compressor and pump, the system still can reach a net power output of 97.32 kW. The thermal efficiency of the engine integrated with the proposed system is improved by 2.89%, and the brake specific fuel consumption is reduced by 5.88%. And the heat rejected by the system can be used to heat water from 25 °C to 45 °C (11.93 kg/s) and 90 °C (2.18 kg/s), respectively. The proposed system shows better overall performance compared to the basic system without ejectors.

Stabilitas Ekstrak Pewarna Daun Singkong (Manihot esculenta C.) Pada Perlakuan pH Awal dan Suhu Penyimpanan

Cassava leaves are leaves that can be used as a source of natural dye. Cassava leaves have a fairly high chlorophyll content and can be extracted into green dye extract. This study aimed to determine how the stability of the cassava leaf dye extract at the initial pH treatment and storage temperature and to determine the initial pH and temperature that provide the best stability to the cassava leaf dye extract during storage. This experiment used a completely randomized design with two factors. The first factor is the initial pH which consists of pH 9, pH 10 and pH 11. The second factor is the storage temperature consisting of cold temperature (8±2ºC) and room temperature (28±2ºC). The data were analyzed by analysis of variance to determine the effect of treatment on the observed variables. The results showed the initial pH and temperature treatment during storage and their interactions affected the total chlorophyll content, chlorophyll a content, chlorophyll b content, antioxidant capacity, brightness level value (L*), redness level value (a*) and yellowness level value ( b*) cassava leaf coloring extract. Cassava leaf dye extract was most stable at initial pH 9 and cold temperature (8±2ºC) during storage. Storage of cassava leaf dye extract for 7 days caused a decrease in total chlorophyll content of 48.44%, chlorophyll a by 46.86%, chlorophyll b by 49.35%, antioxidant capacity by 30.87%, redness level value (a*) by 62.91%, but caused an increase in the value of the redness level (a*) of 62.91%, the value of the brightness level (L*) of 29.28% and the value of the yellowness level (b*) of 49.02% against the control.

Preservation of high pressure pasteurised milk by hyperbaric storage at room temperature versus refrigeration – Effect on natural microbiota and physicochemical properties

Compared to refrigeration (RF), hyperbaric storage (HS) has been applied as a preservation methodology to increase foods shelf-life. The aim of this study was to compare HS at naturally variable uncontrolled room temperature (RT) to RF and evaluate its feasibility to preserve high pressure pasteurised milk (HPP milk), using different pressure levels (50, 75 and 100 MPa), by testing microbial and physicochemical parameters.While RF merely inhibited microbial growth over 40 days, HS/RT (75/100 MPa) maintained pH and gradually reducing all endogenous microorganisms tested to below the detection limit (< 1.0 log CFU/mL) corresponding to at least 2.60 log CFU/mL reduction on total aerobic mesophiles. Additionally, total soluble solids and apparent viscosity could both be kept using HS/RT for at least for 21 days. For 40 days, the total colour difference showed a small but discernible change for RF and HS/RT conditions, being also observed an increase on soluble protein for HS/RT samples, which may have resulted by pressure leading to aggregation of micelle caseins and whey proteins.In conclusion, the present work showed the potential of HS to preserve HPP milk with longer microbial shelf-life compared to RF and with a minor impact on physicochemical properties, being more environmentally friendly and sustainable than conventional RF.

Analysis of an Industrial Energy Audit for Refrigeration

The investigation focused on the energy consumption of part of the refrigeration equipment of a food supply chain company based in France. The cold rooms concerned are used for fresh and frozen food. The objective of the audit is to verify and analyse the electricity consumption of the equipment and to propose sustainable solutions to improve the whole site. The requested energy audit concerned only two machine rooms (machine room 5 and 7). The study predicted an economic gain of up to €30,000/year from equipment maintenance and a significant reduction in environmental impact at this site. In addition, this energy audit identified additional areas for improvement in machine room 7 that could lead to supplementary energy savings of €16,600 and a potential reduction of 15 tonnes of CO2 emissions. Keywords: Energy efficiency, audit, preventive diagnosis, CO2 emissions, energy saving.

Case study: Design of an absorption refrigeration system for milk preservation in Jalisco, Mexico

This article presents a case study focused on designing a refrigeration system for milk storage in a town of Jalisco, Mexico. An absorption refrigeration unit is proposed, activated with a geothermal heat source from an existing well. An economic analysis of the proposal and its comparison with a conventional system and a solar system is presented. The proposed system must provide refrigeration to the warehouse (cold room) with a cooling load of 5 kW, with a geothermal heat source temperature of 80 °C for the single effect system and 163 °C for the double effect system. For the design of the warehouse, the thermal loads were obtained through ceilings and walls, by lighting, infiltration, and by occupation, through the EnergyPlus software. The results show values of monthly thermal loads ranging between 0.94 and 1.1 kW. The single-effect system achieved a COP of 0.85 costing approximately $13,083, while the double-effect system reached a COP of 1.38 with a cost of $18,144.

Use of Phase Change Materials for Food Applications—State of the Art in 2022

The availability of food to a growing world population is a matter of concern for decades. Despite that, post-harvest losses are large in many countries, due to insufficient food preservation. And recently rising prices for fossil energies additionally increase food cost, thus increase the demand for energy efficiency. Probably the first application of phase change materials (PCM) ever was the use of ice for food storage, for preservation. Related to that is the use of ice for transport, and for fast cool down in food processing. The result of a desktop study shows the range of food applications of PCM, the advantages using PCM, and the state-of-the-art, meaning past and ongoing R&amp;D, also including existing commercial products. The overview covers food processing, e.g., industrial process cooling and heating, local pre-cooling of harvested food, solar drying and cooking, for storage and transport e.g., solar cold rooms, fridges, display coolers, trucks and containers, and for food production specifically greenhouses and water purification. PCM are used in many real applications as commercial products, and in many other applications their advantages are proven. Regarding future R&amp;D, the overview also identifies potential for improvement, possibly even of commercial products.

Development of a new type of household appliances – refrigerators with a heating chamber

The object of this study is absorption-type refrigeration appliances, which allow to expand the functionality of household appliances without additional energy consumption.&#x0D; Investigated problem: The aim of this study: firstly, due to the novelty of the proposed technique, it was necessary to show the real possibility of obtaining the temperature level required for technological processes (up to 70 °C); secondly, taking into account the experience gained in experimental studies, it was necessary to propose new designs for solving the problems of refrigeration and heat treatment of food products and raw materials in domestic conditions.&#x0D; The main scientific results: It is shown that the development of devices that combine the functions of refrigeration storage and heat treatment of food products, semi-finished products and agricultural raw materials can become a promising area for energy saving in household appliances. In such household combined appliances, the heat released during the implementation of the refrigeration cycle is not immediately removed to the environment, but is transferred to a special heating chamber, while the temperature in the volume of the heating chamber is maintained higher than the air temperature in the room. The effect of energy saving is achieved by expanding the functionality of household appliances without attracting additional energy costs.&#x0D; The original designs of combined absorption-type household appliances are proposed, a description of their operation, advantages and disadvantages, and areas of application are given.&#x0D; The area of practical use of the research results: In the course of experimental studies, it was shown that the introduction of an additional heating chamber into the structure of household absorption refrigerators, thermally connected with the lifting section by the dephlegmator of the absorption refrigeration unit, does not lead to an increase in energy consumption (according to the test results below than in the standard version by 5 %) and does not impair the performance of the cooling chambers.&#x0D; The area of practical use of the research results: household energy-saving appliances.&#x0D; Innovative technological product: the use of an evaporation-condensation cycle that provides highly efficient heat transfer at a distance of up to 1 meter from the heat dissipation zone of the refrigeration unit to the usable volume of the heating chamber of the household appliance.

Analysis of the influence of outdoor surface heat flux on the inlet water and the exhaust air temperature of the wetting pad of a direct evaporative cooling system

The study investigates the interconnectivity between the inlet water temperature, wind flow rate, and storage water heat flux with the performance of biomass wetting pads in direct evaporative cooling under the external ambient condition of Sub-Saharan Africa. Thus, a standalone direct, evaporative cooling system with an upper water storage tank exposed to wind flow was locally developed and evaluated with jute, palm fruit mesocarp and wood charcoal as biomass cooling pad at three air velocities and constant pad thickness and three different air flow rates. The results indicated that increasing the heat flux around the water tank and decreasing the relative humidity of the inlet air through the wetting pad will lower both the inlet water and pad exhaust temperatures. The water demand was higher in palm fruit mesocarp fibre at airflow rates of 3 m/s, while at 4 and 4.5 m/s, it was higher in wood charcoal, and the value ranged from 9.64 × 10−4 to 1.46 × 10−3 kg/s. Except for jute fibre at 4 m/s, higher humidity difference or low cold room temperature did not translate to higher evaporative cooling effectiveness or efficiency. However, the lower inlet water temperature significantly affected the evaporative effectiveness. This shows the possibility of free moisture transfer into the cold room from the pad materials at increased air flow rates that helped boost the exhaust air's humidity. The average evaporative efficiency for the three pads ranged from 56.4 % to 80.96 %. The values for the enlargement coefficient ranged from 5 to 6.82, while the temperature thermal stress ranged from 24.37 to 28.66 °C.

Assessment of the Hygienic Practices and Microbial Quality of Broiler Meat and its Contact Surfaces From Poultry Retail Outlet and Cold Room in Rivers State Nigeria

Poor hygiene and sanitary practices among poultry meat sellers can lead to the contamination of meat. This contamination can occur as a result of contamination from the contact surfaces in the cold room and retail outlet. The aim of the present study was to assess the sanitary quality of Broiler meat and its contact surfaces (apron, butcher hand, butcher table, bowl, butcher knife and weighing scale) in cold room and retail outlet. Swab samples were assessed for total bacteria count, total coliform count, total staphylococcus count and total fungal counts using Standard Microbiology methods. Mean Total viable count of each sample ranged from Log 10 cfu/cm2/g 3.64 to7.94 and 3.14 to 4.75 from the retail outlets and Cold-room respectively. Mean Total Staphylococcus count. of each sample ranged from Log 10 cfu/cm2/g 1.67to 4.67 and 2.01 to 3.87 from the retail outlets and Cold-room respectively. Counts from the retail outlets were significantly higher than counts in the cold room. Organisms isolated included ; Staphylococcus sp, Bacillus sp, Escherichia coli, Proteus sp, Salmonella sp, Aeromonas sp, Pseudomonas sp, Klebsiella sp and Enterobacter sp. Fungi isolated was Aspergillus sp, Saccharomyces sp, Penicillium sp and Rhodotorula sp. Antibiogram was carried out on the isolated organisms it was observed that Klebsiella sp and Enterobacter sp were resistant to most of the antibiotics used. In order to prevent cross-contamination of meat with isolated bacteria, appropriate cleaning and sanitization steps are required. According to the study, meat contact surfaces that were not thoroughly cleaned before usage, could function as a source of cross contamination. It is recommended that meat sellers especially in developing countries need proper education and training on good hygiene practice. Regulating agencies are also advised to ensure strict compliance by meat sellers to safety standards by embarking on routine inspection at retail outlets and market places.

Energy-saving method and performance analysis of chiller plants group control based on Kernel Ridge Regression and Genetic Algorithm

The upgrading of traditional chiller plants to the high-efficiency refrigerator room is conducive to effective utilization and conservation of energy. An energy-saving method of chiller plants group control based on Kernel Ridge Regression and Genetic Algorithm are presented. Combined with machine learning and the classic model of the chiller plants, the multiple nonlinear problems between the system parameters of the chiller plants are solved. A more detailed group control model of chiller plants is established, which is suitable for multiple chillers, variable-speed pumps, and variable-frequency fans. Incorporate the start-up time of the chiller, the difference between the actual cooling capacity and the target cooling capacity into the penalty function, and use the Genetic Algorithm for multi-dimensional optimization to find the best efficiency point of the entire refrigeration room and achieve the goal of energy saving. A comparative analysis of the actual operation of the cold room system of a large electronics factory in Guangdong for three months is carried out. Compared with the traditional PID algorithm, the three-month power saving rate of this group control energy saving method is: 31.34%, 14.33%, 19.22%.