Search Results (554)

Rising global demand for space cooling is driving peak electricity loads, greenhouse gas emissions, and refrigerant pollution from vapor compression air conditioning. Evaporative cooling is a proven, low-electricity alternative using no synthetic refrigerants, but its evidence base is fragmented and its regulation underdeveloped. This review synthesizes sixteen publicly available institutional publications from 2009 to 2024, analyzing performance, barriers, and deployment conditions. Multistage indirect evaporative cooling achieved reported or simulated energy reductions of 57–95% against study-specific vapor compression baselines in hot–dry climates, with Energy Efficiency Ratio values of 63–76 versus a rooftop unit baseline of 12. These figures rest almost entirely on monitoring in one ASHRAE climate zone, with several compared against modeled rather than measured baselines. Two independent reviews published twelve years apart each identify Iran as the only country with mandatory energy performance requirements for evaporative coolers; water use labeling remained similarly underdeveloped. The evidence base is asymmetric: the United States provides the most rigorous monitoring, while India’s larger deployment, exceeding 800 buildings, lacks equivalent verification. Five research gaps are identified, most urgently the absence of integrated water–energy life-cycle accounting. A four-part policy response is proposed: climate suitability mapping, mandatory performance and water use standards, open monitoring for publicly funded pilots, and prioritization of data centers for market development. The regulatory gap identified here also holds in the European Union, where the Ecodesign framework addresses vapor compression air conditioners but does not constitute standalone evaporative air coolers as a regulated product group. Full article

Total postharvest losses of fresh fruits and vegetables in tropical and subtropical agricultural systems frequently exceed 30 percent, driven by high crop perishability, limited cold-chain infrastructure, and the geographic concentration of conventional processing facilities far from production zones. This review examines the engineering principles, operational architecture, and applied performance of mobile aseptic processing platforms (MAPPs) as a decentralized strategy for postharvest stabilization of perishable agricultural commodities. MAPPs integrate in-line homogenization, high-temperature short-time (HTST) or ultra-high-temperature (UHT) thermal treatment, clean-in-place (CIP) and sterilization-in-place (SIP) cycles, and aseptic filling within transportable, modular units engineered for field deployment. Projected MAPP capacities reach up to approximately 11,300 kg (25,000 lb) per 8 h shift, while still complying with internationally recognized food safety frameworks, including HACCP, ISO 22000, and SQF. Comparative analysis with centralized processing infrastructure and earlier decentralized initiatives, including the EU Horizon 2020 Food Processing in a Box (FOX) project, indicates that mobile aseptic systems uniquely combine field mobility with the production of ambient-stable shelf-life formats independent of refrigerated distribution. Conservative impact modeling suggests that single-unit deployments may recover on the order of 3000 t of edible product annually, with corresponding water, fertilizer, and greenhouse gas externality reductions. The review synthesizes the current state of the technology, identifies engineering and socioeconomic knowledge gaps, and proposes research priorities for scaled adoption in tropical and subtropical food systems. Full article

Carbon dioxide is the number one choice for use as a natural refrigerant for environmentally friendly and sustainable solutions in refrigeration technologies today. It is used for new installations required for all types of applications, from small cold rooms in restaurants or supermarkets to large industrial applications. Practically, it is used to cool down solid products or liquids. Due to its significant inefficiencies, especially related to high operating pressures and throttling processes, the basic CO₂ transcritical refrigeration system requires improvement for superior overall efficiency. For this reason, this review paper provides insight into four types of improved CO₂ transcritical refrigeration systems: first, a CO₂ transcritical refrigeration system with one EJ or dual EJs, parallel compression, and mechanical subcooling; second, a CO₂ transcritical refrigeration system with two-stage heat recovery and a GS/CC heat exchanger; third, a CO₂ transcritical refrigeration system with two-stage compression and intermediary gas supplementation; and fourth, a solar-assisted ejector subcooling CO₂ transcritical refrigeration system. These systems provide COP increases of 21.6%, 26.3%, 25%, up to 30.1%, and 3.4%, as calculated for certain conditions. This review paper explains the mathematical modulation assumptions, energy model construction, heat recovery thermodynamic principle, and conventional and advanced exergy evaluation. As a result, all four improved CO₂ transcritical systems have superior efficiency when compared with standard CO₂ transcritical systems, consuming less energy and being suitable for use in real applications. Full article

Food cold chains rely on refrigeration, cold storage, refrigerated transport, packaging and monitoring systems that consume electricity and fuel while preserving food safety, quality and shelf life. Although many studies propose energy-saving technologies or optimization models for individual cold-chain operations, less is known about how energy-efficiency actions are distributed across refrigeration, logistics and digital monitoring domains, which actors must collaborate to implement them, and which benefits and barriers shape adoption. This paper presents a systematic literature review supported by bibliometric and structured content analysis. Searches in Scopus and Web of Science identified 3930 records before deduplication. After removing out-of-year records and duplicates, 2368 unique records were screened; 896 reports were sought for full-text assessment; 751 reports were retrieved and assessed; 466 studies were included in the final review corpus; and 408 were coded as an applied/action corpus. The synthesis identifies ten energy-efficiency action families, seven cold-chain stage classes, multi-actor configurations, evidence types, collaboration-intensity levels, energy benefits, non-energy benefits and implementation barriers. Transport, routing and distribution is the largest action family (134 records), followed by cold storage and refrigeration technology (66), digital monitoring and information sharing (58), life-cycle assessment, energy assessment and decision support (36), energy systems and renewable cooling (34), packaging and thermal insulation (33), and inventory, and planning and coordination (27). The findings show that food cold-chain energy efficiency is not only a technical refrigeration problem but also a collaborative implementation challenge: many actions require information sharing, coordinated operating decisions, joint investment, data governance or cost/benefit-sharing mechanisms. The review contributes an action-oriented framework that links energy-saving actions to stages, actors, collaboration requirements, benefits and barriers, and it identifies future research priorities on comparable energy metrics, measured savings, renewable cooling, digital twins, demand-side flexibility and governance of collaborative energy-efficiency investments. Full article

Off-grid agricultural cold chains suffer from high energy conversion losses due to intermediate electrical stages in traditional refrigeration. This study addresses the lack of empirical quantification by comparing Direct Mechanical Drive (DMD) and Electrical Power Generation (EPG) drive trains for an R-134a vapor compression refrigeration system. Under steady-state conditions (randomized block design), DMD achieved a statistically significant 13.89% reduction in biomass consumption over EPG (1840.0 vs. 2136.7 g/h; p < 0.001). The biomass consumption was evaluated based on the measured charcoal mass flow under the same lower heating value basis. Conversely, refrigeration COP was statistically equivalent (2.74 vs. 2.73; p = 0.815), confirming that drive-train architecture does not alter internal vapor compression thermodynamics. Only 19.6% of the compressor shaft power appeared as useful fluid-side compression work under this fractional-load operating condition, a volumetric rather than mechanical deficiency arising from operation at 7.7–15.5% of the compressor’s rated capacity. Referenced consistently to the primary biomass chemical energy input, the First-Law biomass-to-cooling system efficiency was 3.66% (equivalent to 5.34% when referenced to the syngas delivered to the engine), with a corresponding biomass-referenced exergy efficiency of 0.44%. Component exergy analysis revealed that the internal combustion engine (59.13% of total exergy destruction, ε = 13.1%) and the gasifier (32.4%, ε = 67.7%) dominated total system exergy destruction (15.49 kW). Furthermore, a 10-year life-cycle cost (LCC) analysis indicates DMD-Syngas yields net present value savings of 21,071.57 USD over gasoline-EPG, yielding a 0.14-year (~50-day) simple payback period on the 400.12 USD net incremental hardware capital cost (the gasification subsystem less the alternator–motor drive train that the direct-drive configuration does not require, and excluding one-time installation and training costs). When the fully installed cost is accounted for—including site preparation, process-water supply and effluent handling, low-voltage provision, installation labor, operator training and contingency—the incremental investment rises to 1298–2405 USD and the payback period extends to approximately 162–301 days. Under the least favorable combination examined, in which commercially purchased charcoal is imposed simultaneously with the upper installed-cost bound, capital recovery extends to approximately 1.4 years; the base case nevertheless recovers the incremental investment within the first operating year. An operational-phase (gate-to-gate) carbon assessment indicates near parity with the gasoline baseline on a strictly attributional basis (+120 to +1200 kg CO₂e yr⁻¹); a net saving of 8880–13,320 kg CO₂e yr⁻¹ arises only under the consequential scenario in which open-field burning of orchard residues is displaced and is further contingent on including black carbon in the accounting basket. This is not a full ISO 14040/44 life-cycle assessment, and the environmental outcome is therefore scenario-dependent rather than intrinsic to fuel substitution. These results demonstrate that mechanical drive-train optimization substantially enhances fuel economy without compromising refrigeration performance, providing a rigorous evidence base for scalable biomass-powered off-grid cold chains. Full article

This study investigates the performance of a diesel engine exhaust gas-driven Rankine Cycle-supported vapor compression refrigeration system using quantum chemical approaches beyond conventional thermodynamic analyses. The study focuses on R448A and its components, namely R32, R125, R134a, R1234yf, and R1234ze(E), evaluated at both the system level and the molecular level. At the system level, the Rankine–VCR system was analyzed using a Fortran-based macroscopic thermodynamic model, in which the thermophysical properties of the working fluids were obtained from the NIST Chemistry WebBook. At the molecular level, Density Functional Theory (DFT) calculations were performed to determine molecular structure parameters, including entropy, heat capacity, chemical hardness, and thermal enthalpy correction. The main objective is to investigate the possible relationships between these molecular descriptors and system-level performance indicators, while considering that mass flow rate is primarily governed by cycle thermodynamic properties. The results show that molecular stability and structural order are strongly associated with system performance. Among the R448A components, R32, with the highest chemical hardness (8.19 eV) and lowest molecular entropy (58.9 cal/mol K), exhibits the most favorable exergetic behavior and achieves the highest plant exergy efficiency of 44.92%. In contrast, R1234ze(E), chemically softer (η = 4.42 Ev) and higher in entropy, exhibits the lowest performance. Additionally, R32’s lower thermal enthalpy correction is associated with higher latent heat of vaporization under the selected operating conditions, reducing the required mass flow by approximately 60–70% compared to the other components. This study demonstrates that, in refrigerant selection, not only the global warming potential (GWP) but also quantum parameters such as chemical hardness, molecular entropy, heat capacity, and thermal enthalpy correction can serve as important complementary performance indicators when interpreted together with macroscopic thermodynamic and exergetic results. Full article

Fermentation is a longstanding preservation process used in meat manufacture to improve product stability, safety and sensory quality. Renewed interest in fermented meats has stimulated research into reformulation and processing strategies intended to address concerns associated with salt, nitrate, nitrite, smoke-derived contaminants and animal fat while maintaining effective fermentation and product quality. This narrative review critically examines current innovations in fermented meat manufacture, including the replacement or reduction of conventional preservatives, smoking alternatives, fat reformulation, functional starter cultures, probiotics, prebiotics and bacteriocins. Developments in non-thermal and accelerated processing, edible and active packaging, intelligent monitoring systems and emerging culture-development technologies are also considered. Evidence indicates that selected functional cultures and formulation strategies can support preservative reduction, microbial control, curing, oxidative stability and sensory development, although their effectiveness is strain-, product- and process-dependent. Several processing and packaging technologies offer additional possibilities for improving manufacturing efficiency, shelf-life management and product safety, but their validation in fermented meat systems varies considerably. Potential environmental benefits, including reduced refrigeration, shorter processing or extended shelf life, cannot be assumed to confer lower overall environmental impacts and require comparative assessment of energy use, material inputs, food-waste effects and life-cycle performance. Future development should therefore prioritise product-specific validation, integrated hurdle-system assessment, regulatory compliance, consumer acceptance and comparative environmental evaluation. Full article

This study investigated a high-temperature heat pump for industrial steam production at 200 °C. Considering refrigerant thermal degradation at elevated temperatures, R1336mzz(Z) was selected because of its thermal stability. Two systems were analyzed: a flash tank (FT) cycle producing steam using a water valve and flash tank, and a steam generator (SG) cycle directly generating steam in the gas cooler. Unlike previous studies focusing primarily on cycle-level thermodynamic performance, this study systematically compares two steam production configurations for a 3 MW-class HTHP by considering heat pump–steam loop interactions and further evaluates their economic and environmental feasibility through LCC and LCCP analyses. Applying an internal heat exchanger reduced the operating pressure and increased the heat pump coefficient of performance (COP) by up to 13%, depending on the pressurized water temperature. In the FT cycle, lowering the valve outlet temperature from 180 °C to 150 °C increased the heat pump COP to a maximum of 3.06. However, the additional mechanical vapor recompression (MVR) power limited the overall system COP to 2.29–2.44. In the SG cycle, the system COP ranged from 1.94 to 2.54 according to the saturated water temperature at the gas cooler inlet, although operation at lower water temperatures approached the critical region, resulting in a narrower operating margin. LCC and LCCP analyses showed that replacing conventional boilers with heat pumps reduced operating costs by 26–59%, depending on regional energy prices, with payback periods of 2.27–8.76 years. Heat pump adoption also reduced life cycle climate impacts by 13–72%. These results demonstrate that high-temperature heat pumps can provide an economically and environmentally viable alternative for industrial steam production at 200 °C. Full article

Battery-electric rail vehicles are a sustainable alternative for diesel-powered vehicles on tracks without catenary. However, the energy demand to heat and cool the cabin limits the vehicle range, and the applied synthetic refrigerants are environmentally harmful. Therefore, this paper studies how energy demand and load on the battery in battery-electric rail vehicles can be reduced using heat pumps with natural refrigerants and efficient thermal management. A heat pump and thermal car body model are developed and validated, which calculate the energy demand in battery-electric rail vehicles. In these models, an optimized thermal management strategy is implemented, which changes the cabin set-point temperature based on catenary availability. For a two-car battery-electric rail vehicle in the climate zone II of Central Europe, the annual thermal energy demand is up to 110 MWh. The application of a heat pump with R290 (propane) can reduce the annual electrical energy demand for heating and cooling by up to 55%. The load on the battery can be mitigated further with the optimized thermal management strategy, reducing the equivalent full cycles by 3%. Overall, the heat pump operation and efficient thermal management strategy lead to higher vehicle range and flexibility in daily operation, increasing the acceptance of battery-electric rail vehicles. Full article

The use of non-certified commercial electronics for cryogenic applications may be attractive due to their reduced cost and high availability, but they also carry risks related to reliability, performance, and thermal compatibility. The decision to use commercial components that are not certified for cryogenics instead of components specifically designed for such applications must be carefully weighed based on specific project needs and risk tolerances. This work presents the characterisation of a Low-Noise Amplifier (LNA) at cryogenic temperatures for use in astronomical instrumentation applications with a microwave kinetic inductance detector (MKID) readout system. The cooling system comprises a cryostat, a cold head operating in a closed-cycle helium refrigeration system based on the Gifford–McMahon principle, a compressor, connectors, cables, a vacuum pump, pressure and temperature sensors, and a temperature control system. The circuit was characterised over the temperature range of 295.4 K to 78.3 K. Full article

This investigation introduces a conceptual configuration for an innovative combined cooling and power (CCP) arrangement that harnesses waste thermal energy from a supercritical carbon dioxide (sCO₂) power loop through integration with a cascading transcritical CO₂ cycle coupled with a lithium bromide–water vapor absorption chiller (tCO₂/LiBr-H₂O VAR). A systematic comparative assessment of thermodynamic behavior and exergoeconomic characteristics was executed across three configurations: the newly proposed CCP scheme, a hybrid sCO₂/tCO₂ power system, and a conventional standalone sCO₂ engine. Parametric sensitivity analyses were conducted to evaluate how various operating parameters influence overall system effectiveness, while particle swarm optimization (PSO) was employed to determine the optimal exergetic efficiency peaks and minimum unit product costs for each architecture. Findings demonstrate that the proposed CCP topology delivers exergy efficiency enhancements of 8.46% and 1.65% relative to the standalone sCO₂ configuration and the combined sCO₂/tCO₂ arrangement, respectively. Correspondingly, reductions in total product unit costs reach 2.80% and 0.80% for the same comparisons. These outcomes confirm that employing a cascading tCO₂/LiBr-H₂O VAR subsystem as the bottoming cycle represents a compelling solution for cooling and power production. Full article

Background: Fresh-cut apples are highly susceptible to quality deterioration due to enzymatic browning and oxidative degradation of bioactive compounds. This study investigated the effects of conventional polyethylene packaging (PE, Pack 1) and two innovative biodegradable packaging materials (Pack 2 and Pack 3) on the stability of bioactive compounds in fresh-cut Golden Delicious apples during refrigerated storage. Individual phenolic compounds ((+)-catechin, caffeic acid, (−)-epicatechin, p-coumaric acid, rutin, and quercetin) were quantified by HPLC-PDA, while spectrophotometric assays were used to determine total phenolic content (TPC), total flavonoid content (TFC), and antioxidant capacity (ABTS and DPPH). The environmental performance of the packaging materials was assessed through Life Cycle Assessment (LCA) using SimaPro v.9.5.5. Results: Polyphenol stability was significantly influenced by packaging and storage time (p < 0.001). Compared with fresh-cut apples at t0, Pack 2 promoted a 17.4% increase in total phenolic content after 21 days, whereas Pack 1 and Pack 3 showed reductions of 31.0% and 37.6%, respectively. HPLC analysis revealed compound-specific responses, with rutin and quercetin being markedly better preserved in Pack 3 after 21 days (17.65 and 1.93 mg/100 g, respectively) than in Pack 1 (0.67 and 0.19 mg/100 g, respectively). Two-way ANOVA confirmed significant effects of storage time, packaging, and their interaction on TPC, TFC, ABTS activity, and all individual phenolic compounds (p < 0.001), whereas DPPH activity was not significantly affected (p > 0.05). Pearson correlation (TPC–ABTS, r = 0.6885, p < 0.001) and principal component analysis indicated that antioxidant capacity was more closely associated with the qualitative phenolic profile than with total phenolic concentration alone. LCA highlighted environmental trade-offs among the packaging systems: Pack 1 showed lower impacts in several categories, Pack 2 displayed an intermediate environmental profile, whereas Pack 3 reduced dependence on fossil resources but exhibited higher land- and water-use impacts together with limitations related to end-of-life management. Conclusion: Packaging materials significantly affected the preservation of phenolic compounds and antioxidant activity in fresh-cut apples while exhibiting distinct environmental profiles. The results demonstrate that no packaging system simultaneously maximized product quality and environmental sustainability, highlighting the importance of integrating analytical performance with life-cycle assessment when developing innovative food packaging solutions. Full article

Color instability in anterior composite restorations remains a primary cause for clinical replacement. While pre-polymerization thermal modification is increasingly utilized in daily practice, its precise impact on phase-specific and long-term optical resistance against continuous thermal aging and aggressive dietary staining remains unclarified. This in vitro study evaluated the impact of pre-polymerization thermal modification (4 °C, 23 °C, and 55 °C) on the phase-specific and cumulative color stability (ΔE₀₀) of four anterior composite resins subjected to sequential thermal aging and prolonged coffee immersion. One hundred twenty specimens (n = 10) were prepared, and ΔE₀₀ was assessed using the CIEDE2000 formula at baseline (T0), post-thermal cycling (T1), and post-coffee immersion (T2). Mixed repeated-measures ANOVA revealed a significant three-way interaction (phase × material × temperature, p < 0.001), demonstrating that thermal conditioning effects vary by material formulation and aging dynamics. During thermal aging (ΔE₀₀ T0–T1), pre-polymerization cooling (4 °C) induced significantly higher discoloration in Estelite Sigma Quick compared to preheated conditions (p < 0.001). Following coffee immersion (ΔE₀₀ T1–T2), refrigeration at 4 °C significantly increased staining in Enamel Plus HRI (p = 0.026) and Estelite Sigma Quick (p = 0.007) compared to room temperature and preheated groups. For cumulative color change (ΔE₀₀ T0–T2), the material type was the primary determinant (p < 0.001), while the independent effect of temperature was not statistically significant (p = 0.395). In conclusion, preheating (55 °C) provides no significant cumulative advantage against staining, whereas refrigeration (4 °C) increases susceptibility to physical and chemical discoloration. The intrinsic chemical composition remains the critical factor driving long-term color stability. Full article

Conventional food packaging cannot actively regulate spoilage-related molecules such as ethylene and volatile organic compounds that accumulate inside sealed packages. Smart adsorption based nanocatalysts (SABNs) integrate adsorptive scaffolds, catalytic centers, and stimuli responsive triggers to progressively remove these spoilage markers. This review establishes a unified three pillar framework and critically examines how adsorption, catalytic degradation, and regeneration cycles are proposed to function under food-relevant conditions. Across major food categories, reported photocatalytic systems achieve ethylene removal efficiencies of 50% to 90% and extend shelf life by 1 to 5 days under controlled light and temperature. However, performance declines sharply under the dark, humid, and refrigerated conditions typical of real supply chains. A systematic evidence level grading of twelve representative SABN systems reveals that the majority cluster at levels L³ and L⁴, while none has yet reached level L⁵, which requires both standardized migration testing and sensory evaluation. Key barriers, including nanoparticle migration, fragmented regulation, scalability, and life-cycle impacts, are assessed. By introducing explicit inclusion/exclusion criteria and a six-level evidence grading framework, this review maps critical gaps in migration data and cold-chain validation and outlines a staged roadmap toward regulation-ready active packaging technologies. Full article

The increase in neutron flux at the Oak Ridge National Laboratory (ORNL) Spallation Neutron Source (SNS), currently operating at 2.0 MW proton beam power, has created new opportunities for higher-throughput neutron scattering experiments while also increasing the importance of minimizing background scattering and optimizing sample-environment operations. To address these challenges faced by the Backscattering Silicon Spectrometer (BASIS), several upgrades were developed and evaluated, including boron carbide (B₄C) masking for flat-plate sample containers, multi-cell sample holders used with a vertically translating sample stick, and an automated helium pump-and-purge (HPP) system for closed-cycle refrigerators. Neutron diffraction measurements demonstrate that B₄C masks reduce background scattering by 49–67%, outperforming both borated aluminum and boron nitride masks while introducing no additional Bragg reflections within the instrument’s accessible Q-range. Commissioning tests of a double-cell flat-plate sample container showed no measurable crosstalk between adjacent sample compartments and confirmed a stable thermal performance, enabling multiple samples to be measured without repeated temperature cycling. In addition, the automated HPP system provided reproducible sample-space gas handling with approximately ±1 mbar precision while reducing the need for operator intervention and supporting remote operation. Together, these developments improve signal-to-noise performance, increase experimental throughput, and enhance operational efficiency at BASIS, supporting the instrument’s continued operation under higher neutron flux conditions. Full article