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![Beverage cooler vending machine with an integrated PCM evaporator: a) System principle sketch, b) PCM evaporator [130]. Copyright ©IIF/IIR. Published with the authorization of the International Institute of Refrigeration (IIR): www.iifiir.org](profile/Hakon-Selvnes/publication/347991052/figure/fig9/AS:975233192308753@1609525120267/Beverage-cooler-vending-machine-with-an-integrated-PCM-evaporator-a-System-principle.png)
Beverage cooler vending machine with an integrated PCM evaporator: a) System principle sketch, b) PCM evaporator [130]. Copyright ©IIF/IIR. Published with the authorization of the International Institute of Refrigeration (IIR): www.iifiir.org
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![Figure 2: Bin with PCM for transport and storage of food [91]....](profile/Hakon-Selvnes/publication/347991052/figure/fig2/AS:975233188122627@1609525119769/Bin-with-PCM-for-transport-and-storage-of-food-91-Reprinted-from-Applied-Thermal_Q320.jpg)
This paper presents a thorough review on the recent developments and latest research studies on cold thermal energy storage (CTES) using phase change materials (PCM) applied to refrigeration systems. The presented study includes a classification of the different types of PCMs applied for air-conditioning (AC) systems (20∘C) to low-temperature freez...
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... than the peak load. The novel vending machine is composed of a triple-layer glass door and vacuum insulated panels on the three other sides to reduce the heat transfer and air infiltration from the ambient, thereby reducing the cooling load. The PCM storage consists of three PCM-HEX units located at the rear wall of the cabinet as represented in Fig. 9a. A PCM-HEX is represented in Fig. 9b and consists of a tube-and-plate HEX placed inside a thin metal container. The tube-and-plate HEX consists of copper tubes where the refrigerant circulates, attached to a conducting plate. During the charging process, the PCM storage unit acts as an additional evaporator to the main evaporator ...
Context 2
... machine is composed of a triple-layer glass door and vacuum insulated panels on the three other sides to reduce the heat transfer and air infiltration from the ambient, thereby reducing the cooling load. The PCM storage consists of three PCM-HEX units located at the rear wall of the cabinet as represented in Fig. 9a. A PCM-HEX is represented in Fig. 9b and consists of a tube-and-plate HEX placed inside a thin metal container. The tube-and-plate HEX consists of copper tubes where the refrigerant circulates, attached to a conducting plate. During the charging process, the PCM storage unit acts as an additional evaporator to the main evaporator located at the bottom of the cabinet. The ...
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Citations
... PCMs enhance temperature control in cold storage and HVAC systems, offering significant benefits in energy efficiency, cost savings, and grid stability [12][13][14]. By integrating PCMs into HVAC systems, cooling energy can be stored during off-peak hours, such as at night, and released during high-demand periods [15,16]. ...
A R T I C L E I N F O Keywords: Cold thermal energy storage (TES) Macro-encapsulated phase change materials (PCM) Residential cooling applications Numerical and experimental analysis Energy storage efficiency COMSOL Multiphysics and MATLAB modeling A B S T R A C T The study focuses on the numerical simulation of the charging and discharging phases of a thermal energy storage designed for cold applications, utilizing water and a macro-encapsulated Phase Change Material (PCM). The experimental setup, used for the experimental validation, comprises an electric chiller, a heat exchanger, and a 320-liter cold storage tank containing 55 aluminum bottles filled partially with a biological PCM. This setup experimentally simulates a residential scenario in Italy's climate zone E, characterized by minimum winter temperatures below 0 • C and maximum summer temperatures over 25 • C. Numerical simulations are performed through the commercial solver COMSOL Multiphysics integrated with Matlab. A one-dimensional Matlab model simulates water behavior in the storage tank, while the performance of the PCM is analyzed using the Effective Heat Capacity (EHC) method in COMSOL Multiphysics. Key results include system charging/discharging times, water temperature variation, energy storage charge/discharge rates, and the PCM melt fraction. The numerical data on water temperature variations inside the tank are compared with experimental results, showing good agreement. Additionally, a parametric analysis is performed to assess how the size of the PCM container influences the system's performance.
... Regarding physical properties, the PCM should exhibit minimal density changes during phase transitions to reduce storage volume and encapsulation size. Chemical criteria are also important, with low phase hysteresis effect requirements, strong cyclic thermal stability with minimal degradation of latent heat capacity, and PCT over time [57,58]. The material should also be compatible with encapsulation materials and non-hazardous to ensure safe implementation. ...
This study investigates the thermal properties of glycerol-water mixtures and their potential as Phase Change Materials (PCMs) for Cold Thermal Energy Storage (CTES) in cold chain applications. The study characterizes key thermal properties, including Phase Change Temperature (PCT), latent heat, density, thermal conductivity, and specific heat. Results indicated that increasing glycerol concentration decreased the PCT of the mixture, reaching −7.76 °C to −21.82 °C, at glycerol concentrations ranging between 25 wt% to 45 wt%, respectively. However, this decrease in PCT is accompanied by a reduction in latent heat, 147.5 kJ·kg−1 to 73.6 kJ·kg−1 for the respective concentrations.
To enhance the PCM properties and achieve optimal thermal performance, NaCl was added as an additive to the glycerol-water mixture. The Response Surface Methodology (RSM) was employed to optimize the concentrations of PCM components, aiming to achieve a desired PCT of −20 °C and maximize latent heat capacity. The developed model demonstrated high predictability, with an R2 of 99.20 %, and good statistical significance, as indicated by an overall model F-value of 98.68 and a P-value of 0.0003. Based on this optimization, three mixtures were selected for further characterization, exhibiting suitable PCT values of around −20 °C to −18 °C and latent heat capacities ranging from 97 kJ·kg−1 (PCM-M1) to 280 kJ·kg−1 (PCM-M3).
A one-dimensional model was developed to assess the impact of optimized PCM-M3 on the temperature stability of frozen food products. Incorporating the PCM layers significantly improved the thermal control of the perishable product. During standard freezer operation, the product temperature was maintained at −20 °C ± 0.065 °C compared to the reference case (without PCM) at −20 ± 0.81 °C. During defrost cycles, and using PCM-M3, the maximum product temperature reached −19.42 °C, compared to −16.98 °C without PCM.
... Moreover, the efficiency of refrigeration systems is also reduced in the daytime due to augmentation in air temperature [4]. To overcome these challenges, cold thermal energy storage (CTES) systems are receiving attention due to their flexibility in storing energy amidst lowdemand times and utilizing it at peak demand [5]. However, the dependence of commercial CTES systems on traditional phase-changing materials (PCMs) is challenging owing to their poor thermal conductivity in solid phase [6]. ...
The porous powdered composites, containing metal halide salts are being used to enhance the storage of cold thermal energy storage (CTES) medium such as ammonia for efficient cooling systems. However, due to the low mass transfer attributable to agglomeration, reduction in pore accessibility, and sample loss, the powdered samples face challenges translating from lab to pilot scale. Conversely, the structuring of composites in beads and pallets can modify the surface chemistry and adsorption mechanism. To investigate the impact of structuring, a comparative analysis of pure, calcium chloride (CaCl 2 )-impregnated activated carbon (AC) powder and CaCl 2 -crosslinked AC beads was conducted in this work, to observe the ramification of surface chemistry due to salt distribution, porosity, surface area and pH-controlled crosslinking, on ammonia adsorption. The role of pH in bead formation introduced a new dimension in tailoring ammonia adsorption efficiency. The bead sample containing 20% CaCl 2 (AC-B (20%)), with pH-8 crosslinking solution, has shown the two times more ammonia adsorption due to optimum crosslinking, physicochemical interactions and the presence of tuned amount of calcium chloride (CaCl 2 ) on the surface and pores. SEM, XRD, FTIR, BET, DFT, and XPS are used to analyse the fabricated samples before and after the adsorption to thoroughly investigate the adsorption mechanism. The kinetic analysis of experimental results was conducted by applying nonlinear Pseudo 1 st order (PFO), Pseudo 2 nd order (PSO), and Elovich models, with best fit with N-PSO model confirming the highest mass transfer by the bead sample (AC-B (20%)). Lastly, the economic feasibility analysis as well as the impact of thermal treatment on recovery and sample regeneration was studied by desorbing the best samples at four different temperatures (120 °C, 140 °C, 160 °C, and 180 °C).
Graphical Abstract
... Two commonly used refrigeration methods are absorption and vapor compression refrigeration (VCR), which require considerable activation energy [2]. Vaporcompression refrigeration systems overtax the power grid [3]. Absorption refrigeration systems require considerable high-temperature heat while suffering from low coefficient of performance. ...
... Given that energy efficiency can contribute to 44% of the reduction in CO 2 emissions required by the Paris Agreement, advancing towards efficient and sustainable refrigeration is critical [10]. Phase change materials (PCMs) stand out for this purpose through their ability to store 5-14 times more heat per unit of volume as latent heat than sensible heat methods, making them attractive for improving DRSs [11]. ...
The urgency for more efficient and sustainable domestic refrigeration systems (DRSs) is intensifying due to climate change events like more frequent heat waves. Such challenges impose reducing greenhouse gas emissions, increasing renewable energy storage rates, meeting the perishable food needs for cooling, and mitigating food wastage through power outages. While previous investigations contributed to these goals by studying the potential benefits of adding phase change materials (PCMs) to DRSs, our study extends their application to chest freezers: a type of system still underexplored. Additionally, it seeks to enhance industrialization and design decision‐making towards tailoring different solutions to distinct markets. Namely, by adopting test procedures closely adhering to the European Standard EN 62552:2013 for experimentally testing four prototypes. The analysis of the novel systems' performance focuses on two metrics internationally recognized but scientifically overlooked by previous peer research: the temperature rise time and the daily energy consumption. A novel approach for filling the top‐mounted door with PCMs and an industrialization technique for simultaneous wrapping PCM bags and evaporator tubes around the freezer compartment are introduced to incorporate PCMs, with melting temperatures (Tm) of −21°C and −12°C. Our findings reveal the potential to extend blackout autonomy by 7%–40% and to reduce daily energy consumption by 13%. Furthermore, the results demonstrate that higher Tm values enhance the commercial attractiveness of DRSs in regions with unstable electricity grids where significant autonomy gains are appreciated, while lower Tm values suit sophisticated markets where extended energy storage capacity and compressor lifetime can be prioritized.
... They discuss the enhancement of heat transfer by using the PCM materials listed in their paper. The applications of PCM materials specifically for refrigeration systems were reviewed by Selvnes et al. [10]. They discussed the applications of water, ice, and salt solutions as PCM for refrigeration systems which is very similar to the PCM used in commercial reusable ice cubes that are available in the market. ...
Reusable ice cubes as mini–ice packs have been widely used in the food industry and have played important roles in preventing waterborne diseases and microplastic contamination from using water ice cubes due to unhygienic water sources. This study investigates the thermal performance of various commercially available reusable ice cubes, assessing their cooling efficiency using a DS18B20 thermocouple sensor integrated with an Arduino microcontroller and a HIKMICRO B20 infrared camera. The primary objective is to evaluate and compare the cooling capabilities of different reusable ice cubes by measuring minimum temperatures and cooling times when placed in a water-filled glass. Experimental results indicate that stainless steel ice cubes exhibit faster cooling rates due to their higher thermal conductivity, whereas plastic ice cubes achieve lower minimum temperatures. The study further examines the influence of key parameters, including the number of ice cubes (N), water volume (V), and glass diameter (D). Empirical relationships for local plastic ice cubes were derived, showing dependencies of minimum temperature at Tmin ~ N1/5V1/3D5/2 and minimum cooling at tmin ~ N1/5V-1/5D3. These findings provide insights into the usage of reusable ice cube performance for various cooling applications.
... Addressing these challenges is essential to improving their performance and expanding their practical applications. Numerous reviews have extensively covered the practical challenges associated with PCMs and the various strategies employed to mitigate these issues, more details on these matters can be found in the following papers [17,39,[71][72][73]. Key challenges include low thermal conductivity, the supercooling effect, phase segregation, and the corrosiveness to encapsulation materials. ...
... The low thermal conductivity of PCMs presents a significant challenge. Researchers have primarily studied two strategies to address this drawback [17,37,42,72]. The first approach involves introducing high thermal conductivity nanoparticles, which can be either carbon-based or metal-based [68,[74][75][76][77][78][79][80][81][82][83][84][85][86]. ...
... a high supercooling degree compared to the organic PCMs. These latter are characterized by less to no supercooling effect [72,96]. To mitigate these issues, nucleating agents have been employed to stabilize the phase change process and minimize supercooling and segregation [17,72,[97][98][99]. ...
The integration of Phase Change Materials (PCMs) as Cold Thermal Energy Storage (CTES) components represents an important advancement in refrigeration system efficiency. These materials have demonstrated significant capabilities in storing and releasing thermal energy, leading to improved system performance and reduced energy consumption. Conventional PCMs such as water/ice, hydrated salts, and paraffin are commonly used in CTES applications due to their favorable thermal properties and/or cost-effectiveness. This review paper explores the benefits and performance of integrating conventional PCMs in various refrigeration systems. It thoroughly discusses the effects of PCM integration on energy consumption, temperature stabilization, storage product quality, and greenhouse gas emissions.
While conventional PCMs are widely used in CTES applications, there is growing interest in exploring sustainable alternatives. Bio-based PCMs, derived from biomass and bio-waste materials, have shown promise as thermal storage candidates. Although these materials have been extensively studied for building applications, their potential in CTES applications remains largely unexplored. This paper also provides a detailed evaluation of bio-based materials based on their phase change temperature and latent heat, assessing their suitability for use in CTES applications.
Through this extensive review, the paper provides insights into the current state and future potential of PCM technology in CTES, highlighting both the proven benefits of conventional PCMs in enhancing refrigeration system efficiency and the potential sustainability of bio-based PCMs.
... They discuss various cooling methods, including compression refrigeration, absorption refrigeration, and thermoelectric cooling, emphasizing the operational efficiency and environmental impact of each method. The integration of phase change materials (PCMs) [13] is also explored for stable temperature control [1]. However, the review focuses primarily on large-scale applications and does not address the specific needs of street vendors, such as portability, cost-effectiveness, and ease of use. ...
Street vendors in developing regions often lack access to portable and affordable cold storage, leading to accelerated food spoilage, financial losses, and health risks. Traditional refrigeration solutions are bulky and costly, while manual freshness assessment is error-prone. This study proposes a smart vending cart integrating IoT sensors and federated learning (FL) to address these challenges, offering real-time environmental monitoring, freshness classification, and privacy-preserving data handling. The smart vending cart incorporates IoT sensors to monitor temperature, humidity, and gas emissions. A Peltier cooling module and a humidifier maintain optimal conditions. Machine learning models classify food freshness, while federated learning ensures vendor privacy by training models locally on each cart. The study explores nine federated learning approaches to train machine learning models across multiple carts without sharing raw data, thus preserving vendor privacy. The Stacking Ensemble approach outperformed all other methods, achieving the highest accuracy, F1-Score, and Cohen’s Kappa (0.99964), with the lowest log loss (0.0022). MetaLearning and Weighted Aggregation also demonstrated high performance but with marginally higher log loss values. Personalized models performed well in heterogeneous data environments but were less effective than ensemble methods. The developed smart vending cart system effectively reduces food spoilage and enhances vendor profitability through automated freshness classification and real-time environmental control. The integration of federated learning ensures privacy, while ensemble techniques improve robustness in resource-constrained settings, offering a scalable solution for street vendors.
... Phase Change Materials (PCMs), have been widely used in several applications [1][2][3][4][5] that exploit the released (or absorbed) energy during a phase transition. PCMs allow for latent heat utilization and have attracted the keen interest of the heat-storage engineering community. ...
We present an innovative enthalpy method for determining the thermal properties of phase change materials (PCM). The enthalpy-temperature relation in the “mushy” zone is modelled by means of a fifth order Obreshkov polynomial with continuous first and second order derivatives at the zone boundaries. The partial differential equation (PDE) for the conduction of heat is rewritten so that the enthalpy variable is not explicitly present, rendering the equation nonlinear. The thermal conductivity of the PCM is assumed to be temperature dependent and is modelled by a fifth order Obreshkov polynomial as well. The method has been applied to lauric acid, a standard prototype. The latent heat and the conductivity coefficient, being the model parameters, were retrieved by fitting the measurements obtained through a simple experimental procedure. Therefore, our proposal may be profitably used for the study of materials intended for heat-storage applications.
... Figure 1 provides a schematic overview of the cascade refrigeration system, highlighting its components, which include a lowertemperature (pressure) cycle and a higher-temperature (pressure) cycle, connected by a cascade condenser. Key components of the cascade system include a low-temperature compressor, a high-temperature compressor, a condenser, an evaporator, a cascade condenser (heat exchanger), and expansion devices for both temperature cycles [10,11]. ...
