As a core heat exchange component in forced-draft cooling towers, the performance of packing material significantly impacts the power consumption of the equipment. In this study, an experimental platform for crossflow cooling tower packing was developed to examine the effects of wind speed, water spray density, and packing height on the heat and mass transfer performance and resistance characteristics of herringbone corrugated packing. Empirical formulas were derived to analyze fan power consumption in crossflow cooling towers. Results reveal that heat and mass transfer performance improves with increased wind speed and water spray density and decreased packing height. Wind speed was found to be the most influential factor; increasing wind speed from 0.96 m/s to 2.05 m/s raised the mass-transfer coefficient by 70%. At low water spray densities, increasing the density significantly enhanced heat and mass transfer. Air resistance in the packing zone increased with air velocity, approximately proportional to the 1.68-1.91 power of wind speed. When the cooling water volume flow rate was 70 m³/h, sacrificing 20% of heat exchange capacity and reducing the inlet-outlet temperature difference from 5 ℃ to 4 ℃ reduced power consumption by approximately 71%. To maintain a power consumption ratio of 0.035 kW·h/m³, lowering the approach temperature from 4 ℃ to 3 ℃ required a 31% reduction in cooling water volume flow rate.

The refrigeration industry is advancing towards environmentally friendly, efficient, and safe alternative refrigerants. To analyze compressor performance with various refrigerants, this study proposes a modified semi-empirical model with 13 characteristic parameters. Experiments were conducted with R22, R507, and R744 under variable operating conditions to identify parameters and validate the model. The experimental and simulated results showed strong agreement, with average relative errors of 2.07% for input power and 1.17% for mass flow rate. Using a typical operating condition, the losses and efficiencies of different refrigerants were compared at various frequencies. Results indicate that R744, with the lowest pressure, leakage, and power losses, demonstrated superior performance. While R507 and R22 showed similar efficiencies, the efficiency of R507 declined significantly at frequencies above 50 Hz due to increased pressure losses. This study provides a theoretical basis for optimizing compressor designs for various refrigerants.

Large cold storage systems play a significant role in economic development with substantial energy consumption and environmental impacts. To promote the green, low-carbon, and efficient development of cold storage, this study mainly focuses on refrigerant substitution, refrigeration system optimization, and the application of transcritical CO₂ systems with ejectors in large cold storage systems. The performance and energy consumption characteristics of different refrigeration systems were compared through a comprehensive annual hourly energy consumption analysis based on the cold storage demands at different temperatures and under various climatic conditions. The results show that the COPs of a transcritical CO₂ system integrated with specifically optimized ejectors are higher than that of the R507A system in all four cities for low-temperature (-32 ℃), medium-temperature (-8 ℃), and high-temperature (0 ℃) cold storages. However, it exhibited performance advantages over the R717 system only in cold climate zones, with the highest system COPs of 2.45, 4.86, and 5.98 for low, medium, and high-temperature cold storages, respectively. Considering the system′s annual energy consumption, the application of CO₂ transcritical systems in low, medium, and high-temperature cold storages in Beijing achieved energy savings of 7.9%, 10.1%, and 10.5%, respectively, compared to the R507A system. The energy savings of the R717 system were slightly higher than that of the CO₂ system in low-temperature cold storage, but the CO₂ system had more obvious advantages in medium- and high-temperature cold storage. The energy consumption of the CO₂ transcritical system also varied across climate zones. In the cold climate zone, the energy savings reached 9.3%, outperforming the R717 system, while in the hot climate zone, its energy savings dropped to 2.8%, slightly lower than that of R717. With the appropriate selection of temperature range and climate zone, the overall operational efficiency and energy-saving performance of the transcritical CO₂ system can surpass those of the R717 system. This study conducted a comprehensive analysis of the operational performance and energy consumption distribution characteristics of the CO₂ system and highlighted its applicability in different scenarios, providing important references for promoting and applying the system, which is crucial for achieving dual carbon goals.

Because the piston volume of a scroll compressor with variable base circle involute can be reduced under the premise of obtaining the same cooling capacity, it can satisfy the compact and lightweight requirements of vehicle air conditioning compressors. To improve the isentropic and volumetric efficiencies of the scroll compressor, a mathematical and geometric model of the scroll disc with a variable base circle involute was established. With the variable index k and the modified increment δ₀ as variables, the internal flow field of the scroll compressor is numerically simulated, and fluid dynamic analysis is conducted. The numerical results show that when the parameters of the variable base circle line are k=1 and δ₀=-0.03 mm, the specific dissipation rate of the fluid in the compressor working chamber is 180.28 s^-1, which is 103.11 s^-1 lower than the 283.39 s^-1 of the flow field in the fixed base circle compressor. The isentropic efficiency of the scroll compressor can be improved by reducing energy loss due to the turbulent kinetic energy dissipation. The performance of the scroll compressor for electric vehicle air-conditioning was tested. Compared with the fixed base circle scroll compressor, the input power of the variable base circle scroll compressor with k=1 and δ₀=-0.03 mm decreases by 1.392%, and the performance coefficient COP_el increases by 4.204%.

A composite cold storage phase change material (PCM) based on Na₂SO₄·10H₂O and Na₂HPO₄·12H₂O was developed to meet the temperature requirements of cold storage air conditioning. The phase change temperature was 8.3 ℃, with a latent heat of 151.3 kJ/kg, representing a 14.24% increase in latent heat compared to previous works. Additionally, a novel thermal energy storage device utilizing spherical encapsulated PCM within a packed bed was proposed. A three-dimensional physical model of the packed bed was constructed using EDEM software to study the effects of sphere capsule size, inlet temperature, and heat transfer fluid (HTF) flow rate on the system's thermal performance. Results show that reducing the sphere capsule size, lowering the HTF inlet temperature, and increasing the HTF flow rate accelerate the thermal energy storage process and reduce charging time. For instance, when the HTF inlet temperature increases from 2 ℃ to 4 ℃, the packed bed's cold storage capacity and density decrease by 5%, the average cold storage rate drops by 41.93%, and the pressure drop remains relatively constant. However, the effect of sphere capsule size on thermal energy storage capacity and density lacks a clear trend and depends on specific engineering applications. These findings offer theoretical guidance for the practical application and broader use of packed-bed thermal energy storage systems for air conditioning.

An energy-saving optimization operation strategy based on maintaining the high-energy-efficiency operation of chillers is proposed to address the prevalent issue of increased energy consumption in the application of cold-storage technology for economic optimization in the current air-conditioning industry. This strategy involves the storage and release of cooling using small cold-storage tanks to actively control the load ratio of the water chiller, thus ensuring that the unit operates efficiently for an extended period to achieve energy savings. A physical model of the air-conditioning system is established and simulated using operational data from the central air-conditioning system of a hospital. Performance curves of the water chiller under different environmental conditions are obtained to accurately depict the high-efficiency operational states of the unit at each moment. On a typical day with a peak cooling load of 9 979 kW, using an active chilled-water storage system, as compared with using the conventional chiller operation strategy without active storage, can reduce 2 777 kW·h of daily electricity consumption, which constitutes 6.0% of the daily electricity usage of the central air-conditioning system. Over the entire cooling season, this approach can save 2.35% of the total electricity consumption of the central air-conditioning system and 4.45% of the electricity consumption of the chiller.

Achieving low-carbon combined cooling and heating supply in distributed areas away from centralized cooling and heating networks is highly significant in the context of carbon neutrality. This study proposes a combined cooling and heating system based on an absorption heat pump, which uses a variety of clean and renewable energies, such as solar heat, geothermal, waste heat, biomass, and air-source energy, to achieve the combined cooling and heating in a wide temperature range from -20 ℃ to 90 ℃. Such systems are suitable for distributed areas, such as villages, cities, and industrial parks. The system model was constructed based on Aspen, and a prototype was developed. The prototype uses a vacuum tube collector to capture solar thermal energy and introduces natural gas as a supplementary heat source to balance fluctuations of solar energy. Multiple sets of indoor heating and cooling terminals can be driven through medium circulation and valve switching using a single set of absorption heat pumps and outdoor units. The environmental test of the prototype was performed in Jinan, and the solar thermal ratio reached 35% during the testing period. An all-weather stable energy supply was achieved by proportional control of natural gas. Moreover, a wide range of concentration adjustments was achieved by controlling the liquid level in the solution tank, enabling efficient system operation in a wider temperature range. The coefficient of performance (COP) of cooling reached 0.30-0.43 at -20 ℃ and 0.70-0.78 at 7 ℃, with cooling water temperatures varying from 30 ℃ to 20 ℃; the COP of heating reached 1.40-1.90 at 45 ℃ and 1.35-1.56 at 80 ℃, with evaporation temperature varying from -15 ℃ to 20 ℃. The study results demonstrated that introducing solar thermal energy and ambient energy recovery increased the fraction of renewable energy in the system to over 50%. Compared with the traditional method of gas furnace plus air conditioning, the annual operating cost and carbon emissions of the proposed system were reduced by over 54.3% and 44%, respectively, which has significant application potential.

The low-carbon transformation of data centers is highly significant for achieving carbon peaking and carbon neutrality. This study compared and analyzed the overall situation of data centers in China. Three variables—energy efficiency improvement rate, proportion of non-fossil energy—and negative emission technology intensity were introduced based on the CO₂ emission and intensity targets of China in key years, and the total CO₂ emissions of the data centers were projected via scenario analysis. The results demonstrated that the power consumption of the data centers increased gradually; the carbon emissions first increased and then decreased, and the power usage effectiveness (PUE) of the data centers decreased gradually. The carbon peak time of the three scenarios is 2030, and the expected times to achieve carbon neutrality are 2059, 2057, and 2055 in the three scenarios. In light of the goal to achieve carbon neutrality by 2060, the data center industry should further improve the energy efficiency utilization rate, increase the proportion of non-fossil energy, strengthen the technological innovation of carbon capture and storage, and enhance the level of carbon sinks.

Microencapsulation technology based on sodium alginate hydrogels can be used to optimize freezing and rewarming procedures and to reduce cryo-damage to cells and tissues. This study first observed the morphology of oocytes of sodium alginate hydrogels at different volume fractions (0.5%, 1.0%, 1.5%, and 2.0%) to determine the safe concentration for their encapsulation. Second, the crystallization temperature and crystallization behavior of sodium alginate hydrogels with different volume fractions were systematically investigated using cryo-microscopy, and the morphology and crystallization of oocytes were compared when they were cooled down/retempered in the base solution (cryoprotectant solution). Finally, the freezing effects of the sodium alginate antifreeze hydrogel-encapsulated oocytes prepared by solvent replacement and physical mixing were compared. The results revealed that oocytes maintained their overall morphology and volume better in sodium alginate gels at volume fractions of 0.5% and 1.0%. Furthermore, oocytes in both the 1.0% sodium alginate group and the cryoprotectant solution group of 12.5% DMSO + 12.5% EG + 0.5 mol/L trehalose did not produce intracellular ice during the cooling process. Additionally, compared with the physical mixture, oocytes in the hydrogel solvent replacement group did not produce intracellular ice during the cooling process, and the cells retained their normal morphology after rewarming.

The refrigeration systems in high- and low-temperature test chambers face challenges of high energy consumption and low efficiency. This study developed an enhanced vapor injection system in a test chamber and conducted experiments using R448A and R404A refrigerants to improve the system efficiency and ensure its alignment with low-carbon environmental goals. The impact of refrigerant charge amounts and compressor frequencies on system performance was analyzed. The results demonstrated that the cooling capacity and coefficient of performance (COP) of the R404A and R448A systems initially increased and then decreased with increasing refrigerant charge amounts. The R448A system demonstrated an 11.3% higher maximum cooling capacity and a 10.4% higher COP than the R404A system. In addition, the compressor power consumption of the R448A system was lower than that of the R404A system. At a refrigerant charge amount of 2.0 kg, the R448A system consumed 7.5% less power than the R404A system. The refrigeration capacity of the R448A system exhibited a 7.7% higher increase compared with that of the R404A system, whereas the compressor power consumption increase was 1.9% lower than that of the R404A system.