Search Results (17)

This study explores the potential of machine learning models to predict evaporator heat transfer performance in Modular Refrigerated Display Cases (MRDCs). Six experimental datasets from MRDC systems were analyzed to compare the efficacy of six machine learning models: Linear Regression, Decision Tree Regression, Support Vector Machines (SVMs), Feedforward Neural Networks (FNNs), Random Forest (RF), and Light Gradient Boosting Machine (LightGBM). The findings indicate that the ensemble tree-based models, LightGBM and RF, are particularly effective in predicting evaporator heat transfer performance. These models demonstrate high accuracy and robustness, effectively capturing the nonlinear relationship between the evaporator temperature and heat transfer coefficient. Moreover, LightGBM and RF exhibit notable stability and adaptability in scenarios of limited data availability and elevated noise levels. Their consistent predictive accuracy across different experimental conditions highlights their suitability for complex refrigeration systems. This research provides essential insights for optimizing MRDC evaporator performance, establishing a theoretical and data-driven foundation for energy-efficient enhancements and intelligent management within cold chain systems. Full article

This research presents a solution for improving energy efficiency in convenience stores by implementing a building energy management system (BEMS) that uses new logic control in air conditioning and refrigeration systems. These systems currently consume the most energy in convenience stores. Implementing this system not only reduces the energy consumption of the compressors in both systems but also minimizes energy loss due to low desired temperatures in the sale area while maintaining the cabinet temperature at the same level. An experiment was conducted at a 314-square-meter convenience store that was open from 6:00 a.m. to 11:00 p.m., and we demonstrated a 4.4-year payback period by controlling AC units close to the desired sale-area temperature of 25 degrees Celsius and increasing the suction pressure at a medium-temperature CDU by 0.3 bar or 31 kPa. This resulted in energy savings of 7.1 kilowatt-hours per day, or 2591.5 kilowatt-hours per year, for the air conditioning system and 2.8 kilowatt-hours per day, or 1022.0 kilowatt-hours per year, for the refrigeration system, resulting in a total energy savings of 9.9 kilowatt-hours per day, or 3613.5 kilowatt-hours per year. The convenience store can use the results of this research to improve the energy efficiency of its cooling system, which includes air conditioning and refrigeration systems, thereby promoting sustainable energy conservation. Full article

This study utilizes a simplified two-dimensional time-dependent computational fluid dynamic (CFD) model to compare the performance of single- and two-layer air curtains in an open-type multi-deck refrigerated display cabinet. Two layers of air curtain generate a more effective invisible barrier from ambient air impact that can reduce electrical energy consumption and maintain a uniform temperature distribution within the cabinet. The CFD model of a refrigerated display cabinet was validated by the experimental data. The results showed a two-layer air curtain advantage over a single air curtain. Electrical energy consumption decreased by 18.5%, and the average temperature of the test products decreased from 5.75 °C to 5.17 °C. The results obtained are important for cabinet design to improve the quality of product storage and reduce energy consumption. Full article

This study presents the experimental investigations of the thermal conductivity properties of refrigerated packages in an autonomous commercial open refrigerated display cabinet. The study aimed to determine whether the type of packaging can reduce the impact of a malfunctioning refrigeration unit on the product. The characteristics of refrigerated packages are studied during the freezing process on the level of loading and the arrangement of the packages in the display case. For the research, four types of packaging were used: combined, composite, plastic, and pulp. Based on the results obtained, the compliance of the packages with the established/existing requirements was determined during each test. It was found that during the refrigeration process, the permissible temperature norms in the case of individual packages complied with the most commonly used. None of the test packages met the norms during refrigeration by filling the products to the intended limit. As a result, simplified labeling of the respective cooling zones is proposed, and the issue of ensuring the uniformity of the cooling itself remains open. Given the cost of production, it is also proposed to take into account this issue (marking the corresponding cooling zones) when designing similar refrigeration equipment. Full article

(1) Background: With the development of cold chain logistics in recent years, the demand for refrigerated display cases has greatly increased in the home and commercial markets. However, the difference of temperature and humidity between each layer of refrigerated display cabinet is great, which affects the health of consumers. In order to reduce the temperature difference for each layer in a cabinet and to improve the temperature uniformity inside the cabinet, an open-hole shelf is designed according to the principle of aerodynamics. (2) Methods: The influence of different shelf aperture ratios on the periodic temperature fluctuation, average temperature, temperature non-uniformity coefficient, and temperature maintenance coefficient inside the cabinet is studied by means of experiments with pork. (3) Results: The results show that when the aperture ratio increases from 0% to 90%, the average maximum temperature in a single cycle in the cabinet shows a trend of first decreasing and then increasing. The minimum temperature difference in the cabinet is 4.3 °C, and the corresponding aperture ratio is 25%. (4) Conclusions: The results show that 25% is the optimal aperture ratio for a shelf in the refrigerated display cabinet. The results provide a better reference for optimization of the structure and temperature in an open refrigerated display cabinet. Full article

This study uses a simplified two-dimensional time-dependent computational fluid dynamic (CFD) model to study the influence of wall shelf configuration and outtake honeycomb inclination angle on the performance of the air curtain in an open-type semi-vertical refrigerated display cabinet. Numerical simulation results show that changing the angle, along with changing the shelf configuration, can reduce the temperature of the intake air grille and improve the warm/cold air ratio. The average temperature of the simulated food products decreased by 1.2 °C compared to the unmodified display cabinet and began to meet the requirements of the temperature category 3M0. The proposed CFD model was validated by the experimental results. The simulation results obtained are important for cabinet design to improve product storage quality and reduce energy consumption. Full article

An experimental rig of a zeotropic mixture separation condensation-based dual-temperature refrigeration cycle is built and the mixture R290/R600a is used as the refrigerant. Compared with a conventional cycle, the proposed refrigeration system demonstrates its application advantages under an on–off operation mode. Furthermore, the on–off periodic operation behaviors of this refrigeration system are experimentally investigated. The influence of a different refrigerant charge, a refrigerant mass fraction, a throttling valve opening, and ambient temperature are explored to evaluate the cyclic operation characteristics. The results reveal that the compressor average power for the duration of the compressor startup increases and the compressor duty cycle first declines then increases with the rise of the refrigerant charge. The average compressor during an on-period decreases from 104.5 W to 79.2 W and meanwhile the compressor duty cycles fluctuates between 72.1% and 96.9% as the R600a-charged concentration increases from 30% to 70%. The average power of the compressor during the on-period and the duty cycle are also sensitive to the freezer valve opening variation. Thus, the minimum energy consumption of 1.60 kWh·24 h⁻¹ is achieved at the refrigerant charge of 300 g, a R600a-charged mass fraction of 50%, and a freezer throttling valve opening of 10%. A higher ambient temperature deteriorates heat transfer during condensation and increases the cabinets’ heat load, the compressor duty cycle, and eventually affects the daily power consumption. Generally, the present study offers an in-depth insight of cyclic operation characteristics of a separation condensation-based hydrocarbon mixture dual-temperature refrigerator under two parallel evaporators’ concurrent cooling process. Full article

The purpose of this study is to develop a variable frequency brushless DC motor drive for the compressors of refrigerated cabinets. It is based on the microcontroller unit (MCU) produced by Renesas Co., Ltd. using the space vector pulse width modulation (SVPWM) for the modulation of the inverter. In addition, at the AC power supply side of the inverter developed, a circuit for suppressing electromagnetic interference (EMI) and a power factor corrector (PFC) are integrated to control the power factor (PF) at the AC power supply side to be above 0.95, which is far better than the commercially available inverters with a power factor of only 0.5. Finally, an intelligent variable frequency control approach based on the extension theory is designed to classify the rotational speed difference and the rate of change in rotational speed difference between the rotational speed commands and the actual rotational speed of the compressor into 20 zones. Then, for the rotational speed difference and the rate of change in rotational speed difference actually measured, their correlations to the 20 zone categories are calculated to determine an appropriate rotational speed command. The temperature of the refrigerated cabinets can quickly be determined to reach the set target value. The proposed extension speed control is simple in computation and does not require much learning data, making it easy to implement. Furthermore, the drive developed is verified by actual testing and its performance is compared to the compressor drives of the refrigerated cabinets commercially available. It is proved that the performance of the drives developed is indeed far better than that of the drives commercially available. Full article

This paper deals with the experimental research and verification of a passive cooling system operating on the principle of a loop gravity heat pipe designed for cooling electrical cabinets. This type of cooling works automatically by changing the state of the working substance and thus saves energy consumption. Since the designed cooling system ensures heat transfer from the interior cabinet to the outdoor space, where the heat can naturally dissipate to the surroundings, it is dustproof. The heat pipe consists of an innovative evaporator concept designed to minimize liquid and vapour phase interference in the refrigeration circuit. The aim of the research was to experimentally determine the limit performance parameters of the refrigeration system for different volumes of working medium in the evaporator and decrease heat loss in the cabinet interior. The designed device was verified experimentally and by mathematical calculations as well. The greatest benefit of the work is that the cooling device was able to ensure temperature conditions inside the electrical enclosure at a heat load of 2000 W under 60 °C, 1500 W under 55 °C, 1000 W under 50 °C, 750 W under 45 °C and 500 W under 40 °C. Full article

The decontamination efficacy of antimicrobial treatments against Campylobacter jejuni on chicken wings was evaluated. Chicken wings surface-inoculated with C. jejuni (3.9 log colony-forming units [CFU]/mL) were left untreated (control) or were treated by immersion (5 s) or in a spray cabinet (4 s) with water, a sulfuric acid and sodium sulfate blend (SSS; pH 1.2), formic acid (1.5%), peroxyacetic acid (PAA; 550 ppm), or PAA (550 ppm) that was pH-adjusted (acidified) with SSS (pH 1.2) or formic acid (1.5%). All evaluated immersion and spray chemical treatments effectively (p < 0.05) lowered C. jejuni populations on chicken wings. Spray application of chemical treatments resulted in immediate pathogen reductions ranging from 0.5 to 1.2 log CFU/mL, whereas their application by immersion lowered initial pathogen levels by 1.7 to 2.2 log CFU/mL. The PAA and acidified PAA treatments were equally (p ≥ 0.05) effective at reducing initial C. jejuni populations, however, following a 24 h refrigerated (4 °C) storage period, wings treated with acidified PAA had lower (p < 0.05) pathogen levels than samples that had been treated with PAA that was not acidified. Findings of this study should be useful to the poultry industry in its efforts to control Campylobacter contamination on chicken parts. Full article

Phase Change Materials (PCMs) incorporated in refrigerators can be used to shift their energy consumption from peak periods, when the electric network energy demand is the highest, to off-peak periods. While PCMs can flatten the energy demand curve, they can achieve economic savings if Time-of-Use (TOU) electricity tariffs are applied. However, the hourly carbon emission factor is not commonly linked to the hourly tariff, and the final CO₂ emitted due to the operations of the refrigerator would not be fully optimized. In this work, a method based on the Simulated Annealing optimization technique was proposed to identify the optimal working schedule of a cabinet refrigerator incorporating a PCM to reduce its indirect carbon emissions. Data from countries with different representative carbon intensity profiles were used. The normalized standard deviation and normalized range are the best statistical indexes to predict carbon emission reduction in the proposed solution. These parameters proved that countries with a higher hourly carbon intensity variation (Uruguay, France, Denmark, and Germany) benefit from the application of the algorithm. Cost and carbon emission reduction cannot be maximized simultaneously, and a trade-off is required. Full article

Refrigerators play an important role in perishable goods supply chains and are expected to operate efficiently. Thermoelectric refrigerators need specific criteria for assessing their energy efficiency. The existing criteria do not take into account the insulation properties of a refrigerator cabinet, which results in a low credibility of the assessment of energy parameters of thermoelectric coolers. The aim of the research was to develop and approve a new universal criterion for assessing the energy efficiency of stationary thermoelectric refrigerators used in supply chains. It was proposed to replace the known criterion of specific power consumption with a new indicator Pk, that takes into account the overall thermal transfer coefficient of the refrigerator cabinet. Based on experimental studies, the approval of the proposed indicator was carried out on the example of a comparative analysis of four thermoelectric refrigerators from different manufacturers. The indicator application resulted in changes in ranking of the examined refrigerators. It was found that the proposed criterion allows us to assess the effectiveness of a thermoelectric cold source more adequately, including the electric power supply and temperature control system. The research results may constitute guidelines for the design and application of standards for assessing the effectiveness of thermoelectric refrigerators. Full article

Compared with the waste-to-heat and electricity-based hybrid refrigeration system, the innovative lab-scale refrigeration system integrated with the DC and AC cooling units that able to use solar and electricity as energy resources. Previous studies found that temperature control and uniform temperature distribution in refrigeration systems are both critical factors reducing vibrio growth on raw oysters and saving energy consumption. Therefore, this refrigeration system also equipped a specially designed divider and was used to test various air circulation strategies to achieve uniform temperature distribution in six individual compartments. The objective is to investigate and evaluate the effects of air circulation strategies and operating conditions on the cooling performance, including temperature distribution, standard deviation of compartment temperatures, and cooling time using a factorial design method. Results indicated the maximum temperature difference between the compartments was 8.9 ± 2.0 °C, 6.7 ± 2.0 °C, and 4.8 ± 2.0 °C in the scenarios of no air circulation, natural air circulation, and combined natural and forced air circulation, respectively. The interaction of fan location and fan direction showed a significant effect on the compartment temperatures while there was no significant effect on cooling time. A circulation fan on the lower part of the 12-volt section with an air supply from the 12- to 110-volt section was determined as the optimal condition to achieve relatively uniform temperature distribution. Refrigeration system also achieved a cooling temperature of 7.2 °C within 150 min to meet regulations. To that end, the innovative hybrid oyster refrigeration system will benefit oyster industries, as well as the aquaculture farmers in terms of complying with regulations and energy savings. Full article

Food deserts have emerged in underserved urban and rural areas throughout the United States. Corner markets have filled the food voids, but generally without offering residents access to healthy food. The economics for doing so are prohibitive. The purpose of the study is to investigate an opportunity for reducing corner store energy costs in order to make possible retail of fresh produce and meat. Given the typical dominance of refrigeration to the energy cost in such stores, an integrated solar dehumidification system with heating, ventilation, and air conditioning (HVAC) is considered. A typical corner store baseline reliant upon conventional refrigeration and HVAC equipment is defined to serve as a basis for comparison. MATLAB Simulink dynamic models are developed for the posed system and baseline model. The results show energy reduction in the refrigerated cabinets of maximally 28%, 27%, and 20%, respectively, in Dayton, OH, Phoenix, AZ, and Pine Bluff, AR. The respective HVAC energy savings are respectively 28%, 56%, and 4%. Collectively these correspond to total annual energy savings of 43%, 51%, and 53%, translating to annual energy cost savings of greater than $12K in all locations. Full article

The control of refrigeration in the food chain is fundamental at all stages, with special emphasis on the retail stage. The implementation of information and communication technologies (IoT, open-source hardware and software, cloud computing, etc.) is representing a revolution in the operational paradigm of food control. This paper presents a low-cost IoT solution, based on free hardware and software, for monitoring the temperature in refrigerated retail cabinets. Specifically, the use of the ESP-8266-Wi-Fi microcontroller with DS18B20 temperature sensors is proposed. The ThingSpeak IoT platform is used to store and process data in the cloud. The solution presented is robust, affordable, and flexible, allowing to extend the scope of supervising other relevant parameters in the operating process (light control, energy efficiency, consumer presence, etc.). Full article