Abstract Growing concern over the environmental impacts of synthetic refrigerants has intensified the need to reduce total carbon-equivalent emissions from refrigeration systems. Deep freezing is critical for preserving the seafood cold chain. India, the world's third-largest fish producer, contributed around 8% of global fish output in 2023–2024, with production reaching 17.5 million metric tons, an annual growth of 9.6%. This growth underscores the urgent need for energy-efficient cold chain solutions to enhance sustainability and global competitiveness. This study evaluates three advanced subcooling-integrated dual-evaporator carbon dioxide–ammonia cascade refrigeration systems against a conventional system without subcooling. Configurations include: (1) a system with mechanical subcooling in both low-temperature and high-temperature circuits, (2) a system with economizer-based subcooling in the low-temperature circuit and mechanical subcooling in the high-temperature circuit, and (3) a system with economizer-based subcooling in both circuits. Performance indicators include annual energy consumption, total equivalent warming impact, and life-cycle cost. For low-temperature subcooling of 1–10K, the system with economizer subcooling in both circuits achieves the highest reduction in compressor power (10.5–12.2%) and coefficient of performance improvement (11.8–14%). The combined economizer and mechanical subcooling show moderate gains, while fully DMS system shows the lowest improvement. The fully economizer-based subcooling system also achieves the highest seasonal energy efficiency and lowest life-cycle cost, making it the most energy-efficient and cost-effective solution for high-ambient seafood cold chain applications.
Abstract To address the limitations of conventional cooling systems and the global shift toward natural refrigerants, this study presents a comprehensive energy, exergy, environmental, and enviroeconomic (4E) analysis of a novel ejector intercooler refrigeration cycle (NEIRC) integrated with a power cycle. Unlike previous studies, the proposed configuration uniquely utilizes the waste heat from the gas cooler of the high-temperature circuit (HTC) to drive a transcritical carbon dioxide (CO2) Rankine cycle, thereby generating auxiliary power for the system. The optimum gas cooler pressures were determined for varying gas cooler temperatures (35 °C to 50 °C) and evaporator temperatures (−50 °C to −25 °C). Results indicate significant performance enhancements: at a gas cooler temperature of 35 °C and an evaporator temperature of −40 °C, the NEIRC demonstrated an 8.59% increase in coefficient of performance (COP) and an 8.56% enhancement in exergy efficiency compared to the standard ejector intercooler refrigeration cycle (EIRC). Additionally, the NEIRC achieved an 11.5% reduction in CO2 emissions and an 11.47% cost advantage over the reference system. These findings provide a vital theoretical benchmark for researchers working on integrated energy systems and demonstrate that the NEIRC is a promising, sustainable solution for low-temperature industrial cooling applications, offering a viable pathway to reduce the carbon footprint of refrigeration technologies.
Evaporation of functional nanoparticle-containing droplets on solid surfaces plays a key role in applications such as air conditioning, refrigeration, and electronic cooling. In this study, we experimentally investigated the evaporation behavior and particle deposition of nanofluid droplets on solid surfaces. The deposition patterns were photographed, and microscopic characterizations were performed. The results show that the droplets always evaporate in the mode of constant contact radius. Changes in substrate temperature and droplet volume have little influence on the evaporation mode and morphology of the droplets, and the contact angle changes linearly with time. The surfactant can significantly regulate the kinetic behavior of droplet spreading. The addition of only 0.25% of surfactant sodium dodecyl sulfate (SDS) increases the droplet spreading radius from 0.71 mm to 1.12 mm, decreases the initial contact angle from 83° to 54°, and increases the area of spreading by 89%. The substrate temperature and droplet volume significantly affect the deposition patterns after droplet evaporation. The higher the substrate temperature, the larger the droplet volume and the more obvious the coffee-ring pattern formed after evaporation. SDS significantly increases the coffee ring width, which reaches 230 μm when the mass fraction of SDS reaches 1.00%, and the particles have been widely distributed throughout the entire evaporation area, suggesting that the coffee ring effect has been effectively suppressed. By introducing the <italic>Ma</italic> number, the influence of the Marangoni effect, guided by temperature, volume, and mass fraction changes, on the internal flow of droplets and the mechanism of coffee-ring formation are explained.
Heating and ventilation. Air conditioning, Low temperature engineering. Cryogenic engineering. Refrigeration
Abstract Hydrogen emerges as a promising alternative energy source, particularly in fuel cell applications, necessitating efficient and safe charging and storage systems. This paper presents the design and development of a specialized regulator tailored for high-pressure hydrogen environments. Focusing on precision control, the regulator ensures optimal performance and safety during charging and storage phases. In order to improve the unstable response characteristics of the existing commercial hydrogen regulator, which has the same differential pressure generation site and pressure control site, a regulator operating at an ultra-high pressure of 105 MPa was designed by separating the differential pressure site and the control site. And structural safety and performance of the regulator were predicted through structural and flow analysis. The results of structural and flow analysis of a 105 MPa high-pressure regulator that can be used for high-pressure hydrogen charging and storage systems were compared with the experimentally measured values.
Low temperature engineering. Cryogenic engineering. Refrigeration
To address the problems of energy waste and imbalance between heat and humidity in traditional combined heat and moisture treatment, the annual hourly energy consumption of a residential building in Shanghai was simulated by EnergyPlus software in this study. According to the simulation results, the independent temperature and humidity control technique was combined with dual evaporative temperature compressor, and a temperature- and humidity-controlled air conditioner test bed was established based on dual evaporation temperature. Relevant theoretical calculations were performed, and the operational characteristics of the air conditioner under whole-year operation conditions were experimentally investigated. The results show that it is feasible to use an air-conditioning unit with a double evaporative temperature compressor in an air-conditioning system with separately controlled temperature and humidity, which meets the design requirements and has obvious energy efficiency. In summer, the energy efficiency ratio of the compressor is 3.5, which is 14.8% higher than that of the inverter compressor of conventional air conditioning with the same cooling capacity (3.04). At the same time, the energy efficiency ratio of the unit compressor under the design conditions in winter is 4.3. Compared with the inverter compressor of conventional air conditioning with the same cooling capacity, the air conditioner with dual evaporation temperature shows remarkable energy savings.
Heating and ventilation. Air conditioning, Low temperature engineering. Cryogenic engineering. Refrigeration
Huang Gensheng, Chen Guangming, Zhang Shaozhi
et al.
The control of ice nucleation temperature during the freezing stage has significant influences on quality uniformity of freeze-dried products and drying rate of later stages. For active depressurization to induce ice nucleation of supercooled water in vials, the effects of depressurization rate, final pressure level and supercooling degree on the nucleation phenomenon were studied experimentally and theoretically here. The following results were obtained: under atmospheric pressure the range of releasing supercooling degree(RSD) was 9-17 ℃,while during depressurization the range of RSD became 8-11 ℃; in the range of 5-20 kPa/s the depressurization rate had little effect on the nucleation of supercooled water; in the range of 100-400 Pa, lower final pressure led to lower RSD. Through numerical calculation and analysis it was indicated that the lowest temperature of surface water during depressurization maybe the key factor influencing ice nucleation.
Heating and ventilation. Air conditioning, Low temperature engineering. Cryogenic engineering. Refrigeration
The reasons for the problems of the existing absorption heat exchangers, such as excessively large size, high manufacture costs, and high return temperature of the primary network hot water, were attributed to the “triangular heat transfer processes” inside the absorption heat pumps. The structures of new Multi-stage Vertical Large Temperature Lift/Drop Generation-condensation And Evaporation-absorption Elementary Units were introduced, as well as their principles on how to eliminate the “triangular heat transfer processes” with a relatively compact structure. A new type of the absorption heat exchanger, called the Multi-stage Vertical Large Temperature Lift/Drop Absorption Temperature Transformer (ATT), was constituted by such elementary units. Simulation models for the ATT were built to compare its performance to the traditional single-stage absorption heat exchanger. Results showed that the ATT can reduce the minimum return temperature of the primary network hot water, from 26℃ to under 20℃. When return temperature of the primary network hot water is 26℃, the ATT can reduce the total KA (heat transfer areas multiplied by heat transfer coefficients) by 25%~32%, while the powers of solution pumps inside the ATT were only increased by 19%~48%, which were not remarkable. The ATT has obvious performance advantages over the traditional single-stage absorption heat exchanger.
Heating and ventilation. Air conditioning, Low temperature engineering. Cryogenic engineering. Refrigeration