Search Results (18)

Vapor compression refrigeration systems account for a substantial share of global electricity consumption in residential and commercial applications, with environmental impacts arising from both energy use and refrigerant leakage. Refrigerant charge optimization offers an economical means of improving system performance without hardware modifications. Oil-free linear compressors mitigate lubricant-induced degradation of heat transfer, yet the combined influence of charge amount on the coefficient of performance (COP) and total equivalent warming impact (TEWI) has not been thoroughly quantified. An experimental investigation was conducted on a vapor compression refrigeration system equipped with an oil-free linear compressor using R134a. The experiments covered refrigerant charges of 220–330 g, piston strokes of 9–12 mm, and pressure ratios of 2.0–3.5. Component-level refrigerant distribution and system performance characteristics were analyzed systematically. The condenser holds 74.7% of the total refrigerant charge at the optimal charge of 280 g. Rising charge reduces superheat and increases subcooling, both of which serve as practical indicators of the charge level. The mass flow rate, cooling capacity, and COP all exhibit characteristic non-monotonic trends. The maximum COP of 4.67 and the maximum cooling capacity of 472.7 W are both achieved at 280 g, which is identified as the optimal operating condition. The oil-free design eliminates lubricant interference and yields a clearly condenser-dominated refrigerant distribution. The TEWI increases by only 3.6% when the charge is raised to 330 g, and this slight environmental drawback is offset by the gain in energy efficiency. A distinct COP reduction is observed at a charge of 220 g. The charge of 280 g achieves the best balance between energy efficiency and lifecycle CO₂ emissions. This work provides quantitative guidance for charge selection in oil-free linear compressor refrigeration systems. Full article

Restaurants combine long opening hours, catering demand, kitchen ventilation, DHW, and mixed-fuel cooking loads, making their decarbonisation different from generic commercial retrofit. For small- and medium-sized enterprise (SME) hospitality premises, this makes the transition to net-zero operation a distinct sustainability challenge because a large, process-driven share of demand lies outside conventional building-fabric and building-services retrofit. This single-case study develops a whole-building utility-calibrated OpenStudio/EnergyPlus model for Beit El Zaytoun, a 655.82 m² restaurant in Park Royal, London. Monthly electricity and gas data for June 2024–May 2025 were used to calibrate the baseline at whole-building level. Standalone and cumulative scenarios tested insulation, low-emissivity double glazing, LED lighting and controls, ASHP service scenarios, and an 11 kWp PV array. Baseline demand was 413,895 kWh/yr, equivalent to 631.1 kWh/m²·yr and 75,020 kgCO₂e/yr. The lowest-net-energy analytical package reduced net imported energy to 314,734 kWh/yr and operational carbon to 56,700 kgCO₂e/yr, a retained 24.0% reduction on the source reporting basis; this package is treated as an analytical bound rather than as a final design recommendation because it excludes cooling. The model-derived residual process load, kitchen and catering gas plus kitchen, and back-of-house electricity remained 233,920 kWh/yr across building-focused scenarios. The Residual-Load Index (RLI) rose from 0.57 to 0.74; with ±15% process-load allocation uncertainty, the optimised RLI range was 0.63–0.85, so the post-retrofit balance remained process-load dominated. The case demonstrates a practical decarbonisation ceiling likely to recur in similar high-process-load hospitality premises: fabric, lighting, heat electrification, and PV are necessary but insufficient without catering-equipment, cooking-fuel, kitchen-ventilation, refrigeration-control, sub-metering, and demand-response strategies. The paper contributes whole-building utility-calibrated quantitative evidence and a transferable RLI metric for sub-sector-specific sustainable retrofit policy, and the net-zero transition of SME food-service premises. Full article

Climate change necessitates a global transition toward green and low-carbon development, underscoring the critical importance of energy efficiency. Buildings account for a substantial portion of urban energy consumption and carbon emissions, with central air-conditioning systems representing the largest energy-consuming component. This study focuses on optimizing equipment selection—including chillers, pumps, and cooling towers—for the refrigeration plant of a commercial complex in Xiamen. Following theoretical optimization, the operational performance of the implemented system was empirically analyzed using long-term monitoring data from 2024 to 2025. The results demonstrate an energy efficiency ratio (EER) of 5.44 in 2024 and 5.28 in 2025, surpassing the Grade I efficiency threshold (5.2) stipulated by the Chinese standard T/CRAAS 1039-2023. Monthly EER values consistently remained above 5.06 throughout the cooling season. Detailed performance analysis of individual equipment further confirmed that actual operational performance of chillers, pumps, and cooling towers closely matched or even exceeded rated performance metrics, with chiller efficiency deviations controlled within 5%. This study integrates optimized equipment selection at the design stage with empirical performance analysis based on actual operation, providing a validated approach for improving the energy efficiency of refrigeration plants in commercial buildings and offering valuable references for the revision of relevant energy efficiency standards. Full article

This study evaluates the techno-economic feasibility of producing a functional baked snack formulated with sweet potato flour, cereals, and upcycled brewer’s spent grain (BSG). The analysis, developed in SuperPro Designer^®, integrates experimentally derived parameters from literature, justifying the transition from laboratory-scale data to an industrial production model. The analysis identified refrigerated storage (48 h) and tray drying as the primary bottlenecks limiting throughput. By synchronizing equipment cycles and increasing the number of units, the production capacity was adjusted from 154.32 to 1077.21 metric tons per year, capturing approximately 0.8% of the estimated annual demand for sweet potato snacks in Mexico. Economic evaluation for this scale demonstrated a capital investment of USD 24.6 million and annual operating costs of USD 8.49 million. The inclusion of a sedimentation-based water treatment, while increasing costs, enables a significant reduction in freshwater intake. The project yielded a payback period of 3.62 years and a Net Present Value (NPV) of USD 23.908 million. Sensitivity analysis revealed that profitability is strongly influenced by production volume and sweet potato costs. These findings provide a realistic framework for assessing the commercial viability of functional food formulations when scaled for industrial production. Full article

The cryopreservation of ovarian tissues from fish has recently been carried out for several endangered and commercially valuable species. However, previous studies in this context have focused on the cryopreservation of immature ovaries—mainly through slow freezing and vitrification—which requires specialized freezing equipment or higher cryoprotectant concentrations to keep cell viability. Therefore, the aim of this study was to explore a convenient, rapid, efficient and less toxic method for the cryopreservation of ovaries at the stage of vitellogenesis from yellow drum (Nibea albiflora), an economically important marine fish. The ovaries at the stage of vitellogenesis were isolated and cut into blocks of approximately 1 cm³, then cryopreserved with 15% propylene glycol (PG), fetal bovine serum (FBS) and 0.2 M trehalose as cryoprotectants. Finally, the samples were treated using three different freezing procedures, including a −80 °C refrigerator, liquid nitrogen, and their combination. After 7 days, the tissues were thawed and digested, and the cell survival rates and gene expression levels were detected using cell viability assay kits and qRT-PCR, respectively. The results of the viability assay showed that the procedure of ovarian tissue storage at −80 °C in a refrigerator for 1 h, followed by transfer to liquid nitrogen, resulted in the highest cell survival rate (>90%). Furthermore, the germ cells at various phases were of normal size; presented a full, smooth surface and regular shape; and did not show any signs of cell rupture, atrophy, depression, granulation or cavitation. Furthermore, the qRT-PCR results revealed that genes related to reproductive development, such as vasa, foxl2, zp3 and gsdf, were all down-regulated under the optimal protocol, while the expression of the nanos2 gene (which is specifically distributed in oogonia) maintained a higher level, similar to that in the control group. This indicated that the viability of germ stem cells (oogonia) was not weakened after freezing and that oogonia could be isolated from the cryopreserved ovaries for germ cell transplantation. The present study successfully establishes an optimal cryopreservation protocol for ovarian tissues from Nibea albiflora, providing reference for the preservation of ovaries at the stage of vitellogenesis from other species. Full article

Efficient cooling and heat recovery systems are becoming increasingly critical in large-scale commercial and industrial facilities, especially with the rising demand for sustainable energy solutions. Traditional air-conditioning and refrigeration systems often dissipate significant amounts of waste heat, which remains underutilized. This study addresses the challenge of harnessing low-potential waste heat from such systems to support fifth-generation district heating and cooling (5GDHC) networks, particularly in moderate-temperate regions like Flanders, Belgium. To evaluate the technical and economic feasibility of waste heat recovery, a methodology is developed that integrates established performance metrics—such as the energy efficiency ratio (EER), power usage effectiveness (PUE), and specific cooling demand (kW/t)—with capital (CapEx) and operational expenditure (OpEx) assessments. Empirical correlations, including regression analysis based on manufacturer data and operational case studies, are used to estimate equipment sizing and system performance across three operational modes. The study includes detailed modeling of data centers, cold storage facilities, and large supermarkets, taking into account climatic conditions, load factors, and thermal capacities. Results indicate that average cooling loads typically reach 58% of peak demand, with seasonal coefficient of performance (SCOP) values ranging from 6.1 to a maximum of 10.3. Waste heat recovery potential varies significantly across building types, with conversion rates from 33% to 68%, averaging at 59%. In data centers using water-to-water heat pumps, energy production reaches 10.1 GWh/year in heat pump mode and 8.6 GWh/year in heat exchanger mode. Despite variations in system complexity and building characteristics, OpEx and CapEx values converge closely (within 2.5%), demonstrating a well-balanced configuration. Simulations also confirm that large buildings operating above a 55% capacity factor provide the most favorable conditions for integrating waste heat into 5GDHC systems. In conclusion, the proposed approach enables the scalable and efficient integration of low-grade waste heat into district energy networks. While climatic and technical constraints exist, especially concerning temperature thresholds and equipment design, the results show strong potential for energy savings up to 40% in well-optimized systems. This highlights the viability of retrofitting large-scale cooling systems for dual-purpose operation, offering both environmental and economic benefits. Full article

Background/Objectives: Urinalysis accuracy requires reliable sample stability that is dependent on the chosen collection and storage conditions. The multiplex Oncuria bladder cancer immunoassay currently needs urine samples stored at 4 °C until analysis, which requires more effort, equipment, and workflow than storing samples at room temperature. Thus, successful sample storage at room temperature (20 °C) may reduce laboratory handling time and expenses. This study evaluated whether different voided urine sample collection and storage parameters affected subsequent biomarker analysis with Oncuria. The Oncuria simultaneously quantifies 10 protein analytes in urine to generate a bladder cancer diagnostic signature. Methods: Samples were stored at varied temperatures (20 °C, 4 °C, −20 °C) for up to 1 month. The effects of adding two commercial urine sample stabilizers and antibiotics (trimethoprim) were also assessed. Subsequently, multiple potential biospecimen stabilizers were tested in urine samples and evaluated with Oncuria in hopes of allowing the urine sample to remain at room temperature for extended periods of time. Results: First, it was demonstrated that voided urine samples stored at room temperate without such stabilizers had different levels of the 10 analytes associated with the Oncuria test compared to voided urine samples stored at 4 °C. Next, we evaluated the effects of commercially available biospecimen stabilizers. Despite the addition of these stabilizers, the levels of the 10 analytes were altered when the samples were stored at room temperature for prolonged periods of time. Therefore, we could not identify a suitable biospecimen stabilizer that would not require sample refrigeration. Conclusions: To minimize sample degradation/alteration after collection, voided urine samples should be refrigerated until analyzed with Oncuria as the refrigeration is advantageous for the storage and the transport of these urine samples. Full article

This paper presents the application of the multiple-criteria decision-making (SAW) method for selecting the optimum refrigerant for the refrigeration systems of commercial cooling equipment used in gastronomy furniture, which is paramount in storing food under optimal conditions. The analysis focused on comparing different refrigerants, including natural refrigerants such as R744 (carbon dioxide) and R290 (propane) and synthetic refrigerants such as R455A, R449A, and R452A. As a result of the analysis using the SAW method, the refrigerant R455A was found to be the best solution. This choice resulted from the consideration of various decision criteria, such as energy efficiency, environmental impact, operating costs, and technology availability. R455A stands out as a synthetic refrigerant that provides high energy efficiency with minimal environmental impact. Its use supports sustainability goals by reducing greenhouse gas emissions and electricity consumption, which is crucial given the modern regulatory requirements and environmental standards. This study offers a practical decision-making tool for commercial refrigeration equipment designers and manufacturers, supporting them while selecting the optimal technological solutions. The choice of refrigerant R455A addresses the need to integrate energy efficiency, environmental protection, and cost-effectiveness in the process of designing modern refrigeration systems for catering furniture. Full article

Because of serious concerns about global warming, manufacturers have started phasing out high global warming potential (GWP) refrigerants in commercial refrigeration equipment (e.g., R-134a). As a potential replacement, propane (R-290) is an environmentally friendly refrigerant for commercial refrigeration equipment because its GWP is only three. However, propane is flammable and is therefore classified as a Class A3 refrigerant per ASHRAE Standards, so safety is a very important consideration when propane-based equipment is designed and deployed in buildings. In the event of a refrigerant leak, flammability of the refrigerant depends on the refrigerant’s local concentration, which is highly affected by the indoor air environment, including temperature and air flow. In this study, a ventilation system attached to a commercial R-290 refrigeration device was designed to eliminate the flammability risk. Moreover, a computational fluid dynamics (CFD) model was developed to investigate the refrigerant leak, thereby evaluating effects of the ventilation system. The CFD model can visualize the flammable zones owing to the leak. Full article

Germany is obliged to report emissions of fluorinated greenhouse gases annually under the UNFCCC. This includes emissions of fluorinated refrigerants when decommissioning RAC equipment. To obtain this information, data on the recovery, recycling, and disposal of fluorinated greenhouse gases is necessary, but such data are scarce. The VDKF-LEC database contains information on the recovery of fluorinated refrigerants from decommissioned RAC equipment in Germany and an extracted dataset was used to obtain real-world information for the years 2017 to 2021. Recovery rates for different fluorinated refrigerants from decommissioned commercial and industrial refrigeration as well as stationary air-conditioning equipment were derived. Furthermore, average lifetimes of equipment for the different sectors were calculated. In the analysis, a dependency of charged refrigerant and age of the unit at decommissioning could be observed. Results from the analysis of the VDKF-LEC dataset were compared with reported data under the UNFCCC for Germany and other available data sources. Full article

Commercial refrigeration systems currently utilize refrigerants with global warming potential (GWP) values ranging from 1250 to 4000. The advent of low GWP alternatives (GWP $<150$) is expected to significantly curtail direct emissions from this segment and greatly influence the ongoing electrification and decarbonization efforts. Most of the low GWP alternatives exhibit flammability risk and hence require robust sensing solutions for a reliable and safe operation of the equipment. This review article aims to provide an overview of different sensing mechanisms suitable for potential applications in systems employing flammable refrigerants, particularly those designated as A2L class. A summary of different A2L refrigerants and their properties is provided followed by a broad review of different classes of sensors, their working principle, transduction method, features, advantages, and limitations. Additionally, key performance characteristics of accuracy, selectivity, sensitivity, dynamic characteristic, and durability among other properties are discussed. Finally, areas of improvement and corresponding approaches are suggested for potential sensors in the successful adoption of A2L class refrigerants. 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

In this study, a lumped parameter model, developed and extensively validated by the authors, is used to simulate the impact of three different dehumidification technologies (mechanical refrigeration dehumidifier, liquid desiccant dehumidifier, and a heat recovery ventilation unit), at a commercial greenhouse growing potted roses in southwestern Ontario, Canada. Typical meteorological year (TMY) data from nearby Vineland, Ontario was used to provide the external weather data used in the model. Each greenhouse bay containing a dehumidification unit was simulated for spring, fall, and winter conditions. The potential reductions in energy use (kWh), greenhouse gas emissions (kg CO_2e), and operating cost were estimated for each test case. The potential energy savings from switching from high-pressure sodium (HPS) to light-emitting diode (LED) lights were also examined. The simulation results showed that switching to LED lamps could reduce the electrical energy usage by up to 60% but would increase the space heating requirements. The expected energy-savings from using dehumidification equipment and switching from HPS to LED lighting in Canadian greenhouses is underrepresented in the literature. With the industry growing in the region, this study provides insight into the expected impact that these systems will have on the energy use in commercial greenhouses. Full article

Cooling towers constitute a fundamental part of refrigeration systems in power plants and large commercial buildings. Their main function is to treat the heat emitted by other equipment to cool down the temperature of the environment and/or processes. In the considered refrigeration system, cooling towers are coupled with compression chillers. The serious world-wide concerns with regard to environmental wear and water scarcity are now common knowledge. One way to mitigate their impact is to reach a state of maximum energy efficiency in industrial processes. For this purpose, this work proposes the application of multi-objective optimization algorithms to find out the optimal operational setpoints of the studied refrigeration system. Here, we exploit swarm intelligence strategies to offer the best trade-offs. This consists of finding solutions that maximize the cooling tower’s effectiveness and yet minimize the global power requirement of the system. Additionally, the solutions must also respect operational constraints for the safe operation of the equipment. In this investigation, we apply two algorithms, multi-objective particle swarm optimization and multi-objective TRIBES, using two different models. The achieved results are compared considering two different scenarios and two different models of the refrigeration system. This allows for the selection of the best algorithm and best equipment model for energy efficiency of the refrigeration system. For the studied configuration, we achieve an energy efficiency factor of 1.78, allowing power savings of 9.48% with tower effectiveness reduction of only 5.32%. Full article

Characterizing the refrigerant side of heat pump water heaters (HPWHs) can be intrusive and expensive. On the other hand, direct external measurement techniques can be unfeasible, particularly in commercial HPWHs for residential applications. Non-intrusive in situ characterization methods have already been successfully implemented in subcritical heat pumps. They provide the refrigerant mass flowrate and the equipment energy performance, by using contact temperature sensors and electric power meters. Subcritical suction and discharge-specific enthalpies necessary to apply the method can be obtained from the measured temperatures and their corresponding saturation pressures. Nevertheless, this approach does not apply to the transcritical CO₂ HPWHs. In the supercritical region, temperature and pressure are independent variables, and an iterative process regarding the compressor isentropic efficiency has to be considered. However, when isentropic efficiency data are not available, an additional procedure is required, using a validated gas cooler model to verify the physical reliability of the numerical solutions. This work aims at presenting base thermodynamic analysis of a novel methodology for non-intrusive refrigerant side characterization of transcritical CO₂ HPWHs, exploring the influence of the compressor isentropic efficiency condition. Full article