Search Results (100)

C₆F₁₂O has been recognized as an environmentally friendly substitute applied in the fire protection, insulation equipment, and refrigeration industry. The stability and catalytic decomposition characteristics of C₆F₁₂O in the presence of metals are crucial for evaluating the applicability of such alternatives across different scenarios and recycling treatment. In this study, the adsorption and decomposition mechanisms of C₆F₁₂O on Cu (1 0 0), Cu (1 1 0), and Cu (1 1 1) surfaces have been investigated based on the density functional theory (DFT). The adsorption structures and energies of C₆F₁₂O and its key dissociation products are investigated to obtain the most stable adsorption configurations. Additionally, the projected density of states (PDOS) and electron density difference calculations are performed to explore the electronic properties of the adsorption systems. Four major dissociation reactions involving the C-C bond breakage of C₆F₁₂O that occurred on Cu surfaces are examined individually, with comparisons made to the corresponding homolytic reactions of free C₆F₁₂O. The results indicate that Cu surfaces exhibit a promising catalytic effect for C₆F₁₂O decomposition, which depends on both the kind of surfaces and the reaction pathway. Furthermore, most decomposition pathways of C₆F₁₂O on Cu surfaces are exothermic and C₆F₁₂O tends to decompose into C₅F₉O and CF₃ under the Cu catalytic effect. Full article

Rigid polyurethane foams (RPUFs) are essential polymeric materials, prized for their low density, high mechanical strength, and superior thermal insulation, making them indispensable in construction, refrigeration, and transportation. Despite these advantages, their highly porous, carbon-rich structure renders them intrinsically flammable, promoting rapid flame spread, intense heat release, and the generation of toxic smoke. Traditional strategies to reduce flammability have primarily focused on incorporating additive or reactive flame retardants into the foam matrix, which can effectively suppress combustion but often compromise mechanical integrity, suffer from migration or compatibility issues, and involve complex synthesis routes. Despite recent progress, the long-term stability, scalability, and durability of surface flame-retardant coatings for RPUFs remain underexplored, limiting their practical application in industrial environments. Recent advances have emphasized the development of surface-engineered flame-retardant coatings, including intumescent systems, inorganic–organic hybrids, bio-inspired materials, and nanostructured composites. These coatings form protective interfaces that inhibit ignition, restrict heat and mass transfer, promote char formation, and suppress smoke without altering the intrinsic properties of RPUFs. Emerging deposition methods, such as layer-by-layer assembly, spray coating, ultraviolet (UV) curing, and brush application, enable precise control over thickness, uniformity, and adhesion, enhancing durability and multifunctionality. Integrating bio-based and hybrid approaches further offers environmentally friendly and sustainable solutions. Collectively, these developments demonstrate the potential of surface-engineered coatings to achieve high-efficiency flame retardancy while preserving thermal and mechanical performance, providing a pathway for safe, multifunctional, and industrially viable RPUFs. Full article

This study explores innovative approaches for sustainable food preservation by incorporating Sichuan pepper extract into biodegradable gelatin and alginate films. In response to growing environmental and health concerns, these natural polymers offer alternatives to petroleum-based plastics and synthetic additives. The aim of this study was to compare films made from gelatin and alginate and containing Sichuan pepper extract (2.5 and 5%) and to evaluate their effectiveness in extending the shelf life of refrigerated beef patties. Scavenging activity and polyphenol content of the extract were evaluated by DPPH (4.70 µmol TE/mL), ABTS (4.03 µmol TE/mL), and Folin–Ciocalteu assays (2.35 mg GAE/mL). In addition, the physical characteristics of the films were also assessed. Film characterization showed that gelatin-based films had greater stiffness (water-based alginate film; 1156 MPa), which diminished with increased extract content (5% extract-based alginate film: 215.5 MPa), and surface homogeneity also declined with higher extract content. However, higher concentrations of the extract (5%) improved optical properties such as UV protection and opacity. Preservation tests performed on beef patties revealed that the films with the extract could significantly reduce lipid oxidation, with lower TBARS values observed in samples covered with these films. Nevertheless, no significant differences were detected between films with the extract. Moreover, samples without the extract were the most oxidized, proving that the film without the extract had no protective effect against oxidation. Overall, these findings underscore the potential of Sichuan pepper as a natural ingredient and highlight the promise of biodegradable films as an effective and eco-friendly strategy for meat product packaging. Full article

This study investigates the dynamic performance and degradation behavior of corrugated cardboard used as protective packaging for home appliances subjected to random vibrations during transportation. Simulated vibration tests were conducted on fully packaged refrigerators to assess the mechanical response of cardboard and expanded polystyrene (EPS) supports under prolonged vibration excitation. Relaxation tests were performed to characterize time-dependent stress decay in the absence of vibration, while cantilever beam experiments quantified dynamic stiffness degradation during vibration exposure. The vibration-induced damage was evaluated by monitoring the decrease in support stiffness over time, revealing a distinct exponential reduction that correlated with increasing excitation levels. Statistical load count analyses, based on auto-spectral methods and Basquin’s power law, were used to model fatigue behavior and predict service life. The findings demonstrated that corrugated cardboard exhibited comparable performance to EPS in maintaining support stiffness while offering the advantage of environmental sustainability. These results provide quantitative evidence supporting the use of cardboard as an effective and eco-friendly alternative to polymer-based packaging materials, contributing to the development of optimized packaging solutions with enhanced vibration durability. Full article

This review article focuses on the long-term durability challenges associated with bamboo fiber-reinforced polymer composites when subjected to various environmental aging conditions such as water immersion, hygrothermal fluctuations, ultraviolet (UV) radiation, soil burial, and refrigerated storage. The primary issue addressed is the degradation of mechanical and structural performance of bamboo fiber-reinforced polymer composites due to moisture absorption, fiber swelling, and fiber–matrix interface deterioration. To mitigate these aging effects, the study evaluates and compares multiple strategies, including chemical and physical fiber surface treatments, filler additions, and fiber hybridization, which aim to enhance moisture resistance and mechanical stability. These composites are relevant in automotive interiors, construction panels, building insulation, and consumer goods due to their eco-friendly nature and potential to replace conventional synthetic composites. This review is necessary to consolidate current knowledge, identify effective enhancement approaches, and guide the development of environmentally resilient bamboo fiber-reinforced polymer composites for real-world applications. Full article

This review paper addresses the design and testing of ultra-low temperature (ULT) freezers, highlighting their critical functions in various industries, particularly foods, medicine, and research. ULT freezers operating at temperatures of −86 °C and lower have come a long way with improvements in freezing technology, for instance, from traditional vapor compression systems to new multi-stage refrigeration technologies. This progress has added operational reliability and energy efficiency, essential for preserving delicate samples and facilitating groundbreaking research. The article deeply explores the contribution of refrigerants to ULT freezer efficiency and sustainability. With the use of chlorofluorocarbons (CFCs), previously reliant on them, being prohibited due to environmental concerns, the sector opted for environmentally friendly substitutes like hydrofluorocarbons (HFCs), natural refrigerants, and hydrofluoroolefins (HFOs). Regulatory compliance is ensured by rigid validation protocols to guarantee ULT freezers are safe and meet quality requirements without compromising the integrity of the stored material. In addition to their wide-ranging advantages, ULT freezers also have disadvantages, such as energy efficiency, incorporating automation, the integration of IoT and AI for proactive maintenance, and the development of environmentally sustainable refrigerants. Adequate management strategies, including regular employee training and advanced monitoring systems, are vital to counteract threats from temperature variations and reduce long-term diminished performance. Finally, subsequent innovations in ULT freezer technology will not only aid in research and medical initiatives but also support sustainable practices, ensuring their core role as beacons of innovation in preserving the quality of precious biological materials and increasing public health gains. Full article

To promote renewable energy utilization and enhance the environmental friendliness of refrigerants, this study presents a novel experimental investigation on a transcritical CO₂ double-evaporator heat pump water heater integrating both air and water sources, designed for high-temperature hot water production. A key innovation of this work lies in the integration of an ejector into the dual-source system, aiming to improve system performance and energy efficiency. This study systematically compares the conventional circulation mode and the proposed ejector-assisted circulation mode in terms of system performance, exergy efficiency, and the economic payback period. Experimental results reveal that the ejector-assisted mode not only achieves a higher water outlet temperature and reduces compressor power consumption but also improves the system’s exergy efficiency by 6.6% under the condition of the maximum outlet water temperature. Although the addition of the ejector increases initial manufacturing and maintenance costs, the payback periods of the two modes remain nearly the same. These findings confirm the feasibility and advantage of incorporating an ejector into a transcritical CO₂ compression/ejection heat pump system with integrated air and water sources, offering a promising solution for efficient and environmentally friendly high-temperature water heating applications. Full article

Automotive air conditioning systems improve passenger comfort and safety while keeping pace with changing environmental and technological requirements. This review evaluates the historical development, technological progress, and future trends of automotive air conditioning systems, primarily focusing on passenger vehicles, where cabin comfort and individualized thermal control are essential. The analysis examines the transition from early, energy-intensive cooling systems typically operating at a coefficient of performance (COP) of around 1.5 to modern, environmentally friendly alternatives that achieve COP values of approximately 3.0 or higher, highlighting the impact of regulatory measures such as the Kigali Amendment. A particular focus is placed on comparing refrigerants, especially the transition from HFC-134a to HFO-1234yf, with a discussion of their ecological impact and compliance with regulations. Innovative technologies, including adsorption cooling, AI-enhanced climate control, and the integration of renewable energy, are being explored as potential solutions to current challenges. Initially, 121 articles were reviewed, with 84 chosen for detailed examination based on their relevance, methodological soundness, and contributions to the field. The results reveal the trade-offs among efficiency, cost, and sustainability, highlighting the need for ongoing innovation to balance energy usage and environmental stewardship. Future studies should focus on creating refrigerants with extremely low global warming potential, improving battery efficiency in electric vehicles, and utilizing AI for tailored climate control. By tackling these issues, the automotive sector can offer more sustainable and efficient air conditioning options that align with consumer expectations and environmental regulations. Full article

To implement the Kigali Amendment to the Montreal Protocol, the global academic community has intensified its research on environmentally friendly refrigerant substitutes. This effort aims to effectively reduce greenhouse gas emissions and facilitate the achievement of carbon neutrality goals. In this study, 14 key influencing factors were identified through the Delphi method, and the Decision-making Trial and Evaluation Laboratory (DEMATEL) approach was innovatively applied to systematically analyze the interrelationships among these factors. The results indicate that technological innovation related to refrigerant substitution ranks first with a centrality score of 5.429, confirming it as the core driving factor for refrigerant substitution. Subsequently, through the integration of Interpretive Structural Modeling (ISM) and Cross-impact Matrix Multiplication Applied to Classification (MICMAC), a hierarchical structure of influencing factors was further developed. This clarified high-driving factors such as government policies and life-cycle costs, as well as highly interrelated factors including climate conditions, greenhouse gas emissions, and performance coefficients. The key contribution of this paper is its success in overcoming the limitations of single-factor analysis by integrating multiple dimensions of influencing factors to construct a hierarchical classification. This innovative and systematic theoretical framework not only offers a scientific basis and decision-making support for refrigerant substitution but also possesses substantial theoretical value and practical guidance. Furthermore, it serves as an essential reference for advancing the development of low-carbon refrigeration technologies. Full article

The twin-screw compressor exhibits significant application value in the fields of energy, refrigeration, construction, transportation, and related domains. Owing to the benefits of short cycles and low costs, numerical simulation technology has attracted increasing attention. Over recent years, the numerical simulation technology for twin-screw compressors has advanced rapidly, and many important results have been achieved. This paper comprehensively discusses the modeling method of twin-screw compressors, the meshing technique, advances in numerical simulation of internal flow, the research status of numerical simulation research regarding structural operating conditions, and performance optimization. The synergistic potential between these technologies for improving the performance and efficiency of twin-screw compressors is investigated. The numerical simulation research progress of the internal flow and performance optimization of twin-screw compressors is systematically reviewed. Against the background of global energy saving and carbon reduction, this paper offers readers an in-depth understanding of the technical challenges, research hotspots, and development directions in the related field. It fills the relevant gaps within the current literature. The results highlight the role and potential of deep exploration of the intrinsic relationship between local complex flow characteristics and structural optimization for the performance optimization of twin-screw compressors. For conforming to actual conditions and pertinency, mathematical models such as multiphase flow and turbulence models should be further improved. The current research results remain constrained by the lack of comprehensive consideration of multi-field coupling. In the future development of energy-saving and environment-friendly high-performance twin-screw compressors, numerical simulation research should be developed for high precision, multi-physical field coupling, influencing mechanism research, energy-saving, and environmental friendliness, and intelligence. It establishes a theoretical foundation for further enhancing the performance and mechanism theory of twin-screw compressors. Full article

This study experimentally analyzes the performance of a passive thermal management system using a three-dimensional (3D) pulsating heat pipe (PHP) designed for pouch cell batteries in electric vehicles. The term “3D” refers to the complex spatial arrangement of the PHP, which features multiple interconnected loops arranged in three dimensions to maximize heat dissipation efficiency and improve temperature uniformity around the battery pack. Lithium-ion pouch cells are increasingly favored for compact and lightweight battery packs but managing their heat generation is crucial to maintaining efficiency and preventing failure. This research investigates the operational parameters of a 3D PHP by testing two working fluids (R134a and Opteon-SF33), three filling ratios (30%, 50%, and 80%), and various condenser conditions (natural and forced convection at 5 °C, 20 °C, and 35 °C). The effectiveness of the PHP was tested using simulated battery discharge cycles, with power inputs ranging from 5 to 200 W. The results show that the 3D PHP significantly improves battery thermal management. Additionally, Opteon-SF33, an environmentally friendly refrigerant, offers excellent heat transfer properties, making 3D PHP with this fluid a promising passive cooling solution for electric vehicle batteries. Full article

Since the Montreal Protocol (dated 1987), the reduction of the environmental impact has been one of the main goals in the HVAC sector, which has led to the replacement of widely used fluids with new environmentally friendly ones. Nevertheless, only new fluids with suitable heat transfer features can be used. The refrigerant mixture R449a, one of the fourth-generation refrigerants, was tested during flow boiling inside a horizontal smooth tube. The experiments were carried out at six different mass fluxes G ∈ [175;400] kg·m⁻²·s⁻¹ and four different bubble temperatures T_b ∈ [2.5;10] °C, while the nominal values for inlet and outlet quality were selected as x_Ti = 0.1 and x_To = 0.9, respectively. The results highlighted that, as the bubble temperature increases, it has an opposite effect on the pressure drop per unit length and the heat transfer coefficient: the former decreases while the latter grows. The comparison between experimental results and the correlations showed that the Zhang and Webb formula provides the best prediction of pressure drop, while the models provided by Bertsch yield the most reliable predictions for the heat transfer coefficient. Nevertheless, for both quantities, other correlations with similar performances are available. Full article

The adoption of eco-friendly refrigerants in air conditioning systems is crucial for advancing low-carbon architecture. The current refrigerant R410A, with its high global warming potential, underscores the need for sustainable alternatives that balance cooling efficiency and environmental impact. This study investigates a binary mixture of R32 and R290 as a potential replacement for R410A. Using the Peng–Robinson equation of state, the thermodynamic properties of the mixed refrigerant were calculated post-temperature glide, analyzing variations across different mixing ratios. A specific ratio of 0.3:0.7 (R32:R290) was identified as optimal, offering a balance between safety and performance, closely matching R410A’s properties. Simulations of the refrigeration cycle were conducted to assess the effects of condensation and evaporation temperatures, as well as subcooling and superheating, on system performance. Key findings reveal that the 0.3:0.7 mixture not only meets safety standards for central air conditioning but also demonstrates efficiency comparable to R410A. These results provide a robust theoretical foundation for the development of low-carbon air conditioning technologies, highlighting the potential of R32/R290 mixtures in reducing environmental impact while maintaining performance. Full article

Urban road traffic congestion has become a serious issue for cold chain logistics in terms of delivery time, distribution cost, product freshness, and even organization revenue and reputation. This study focuses on the cold chain distribution path by considering road traffic congestion with transportation, real-time vehicle delivery speeds, and multiple-vehicle conditions. Therefore, a vehicle routing optimization model has been established with the objectives of minimizing costs, reducing carbon emissions, and maintaining cargo freshness, and a multi-objective hybrid genetic algorithm has been developed in combination with large neighborhood search (LNSNSGA-III) for leveraging strong local search capabilities, optimizing delivery routes, and enhancing delivery efficiency. Moreover, by reasonably adjusting departure times, product freshness can be effectively enhanced. The vehicle combination strategy performs well across multiple indicators, particularly the three-type vehicle strategy. The results show that costs and carbon emissions are influenced by environmental and refrigeration temperature factors, providing a theoretical basis for cold chain management. This study highlights the harmonious optimization of cold chain coordination, balancing multiple constraints, ensuring efficient logistic system operation, and maintaining equilibrium across all dimensions, all of which reflect the concept of symmetry. In practice, these research findings can be applied to urban traffic management, delivery optimization, and cold chain logistics control to improve delivery efficiency, minimize operational costs, reduce carbon emissions, and enhance corporate competitiveness and customer satisfaction. Future research should focus on integrating complex traffic and real-time data to enhance algorithm adaptability and explore customized delivery strategies, thereby achieving more efficient and environmentally friendly logistics solutions. Full article

The production technology for stretch film is highly energy-intensive. Electrical energy is used not only to power individual components of the technological line but also to change the physical state of the raw material (granules) from solid to liquid, which is poured onto the first calender roller. The calender roller must be cooled to solidify the liquid raw material, and the low-temperature heat generated in this process has been treated so far as waste heat and dispersed into the atmosphere. A low-temperature process heat recovery line has been developed, enabling its transformation into high-temperature heat. High-temperature process heat can be utilized in the technological process for the preliminary preparation of raw material when recycled material (regranulate) with highly variable parameters is added to the base material (granules) with strict specifications. The regranulate content can be as high as 80%. The waste heat recovery system is based on two compressor heat pumps powered by eco-friendly refrigerants. This innovative solution facilitates a circular economy, reduces the carbon footprint, and aligns with the European Green Deal. Full article