Microchannel heat exchangers, including a bionic secondary branch (MHE-BS), complete vein bionic branch (MHE-CVB), and incomplete vein bionic branch (MHE-IVB), were designed based on the straight secondary branch (MHE-SS) inspired by the leaf vein structure of Parashorea chinensis. ANSYS FLUENT software was utilized to simulate the flow and temperature characteristics of 20 ℃ cooling water entering these heat exchanger structures under a constant heat flux of 50 kW/m² at different inlet Reynolds numbers (Re=660.07, 990.10 and 1 320.13). The research findings indicate that multistage bionic channel structure can significantly enhance the overall heat transfer performance of the heat exchanger, with MHE-CVB showing more than a 35% reduction in inlet and outlet pressure drop compared to MHE-SS under different working conditions. In addition, it showed an decrease in surface temperature by over 2 ℃ and a strengthening factor for comprehensive heat transfer performance exceeding 1.2.

Steam ejectors are vital components of ejector refrigeration systems and have attracted considerable attention owing to their energy savings and environmental protection. In this study, steam ejector models were optimized, validated, and compared by considering the three-dimensional and non-equilibrium condensation effects. The simulation results of the optimization model were compared with those of the ideal gas model. Based on the condensation model, the effects of the turbulence models (Reynolds-averaged Navier-Stokes (RANS) and large eddy simulation methods (LES)) on the simulation results were studied. Complex flow phenomena captured by different models, such as shock waves, non-equilibrium condensation, and boundary layer separation, were compared and analyzed. The results show that the optimized steam ejector model can credibly predict the ejector performance and capture the complex flow phenomena inside the ejector at the lowest computational cost. The maximum liquid mass fraction obtained using the large eddy simulation method is lower than that obtained using the Reynolds-averaged Navier-Stokes method. The maximum relative deviation against experiments of the entrainment ratio was obtained using the large eddy simulation method of 11%. The condensation model reduces the average relative deviations of the entrainment ratio and critical discharge pressure by 72.0% and 29.9%, respectively.

Room-temperature magnetic heat pumps, one of the main applications of the magnetocaloric effect near room temperature, offer high efficiency, environmental protection, low noise, and low vibrations. This study discusses the application potential of a cascade magnetic heat pump cycle with a large temperature span by comparing the theoretical magnetic heat pump and refrigeration cycles. The results show that meeting the kilowatt-level heating capacity and achieving a wide temperature span of approximately 30 K in an actual heating scenario poses challenges to room-temperature magnetic heat pumps. The differences in design and application between the room-temperature magnetic heat pump and the existing room-temperature magnetic refrigeration prototypes are discussed, with a focus on magnetocaloric material selection strategies and performance evaluation indices suited for large temperature spans. The comparative analysis of magnetic heat pumps and magnetic refrigeration in this study also helps researchers to clarify the key to the design and application of large temperature span magnetic heat pumps based on existing research on room-temperature magnetic refrigeration. It promotes the comprehension and application of room-temperature magnetic heat pumps.

Unnecessary or delayed defrosting results in increased energy consumption, reduced stability, and increased failure rates in refrigeration and heat pump units. Accurately identifying the frost status and timely defrosting are important for improving the performance of refrigeration and heat pumps. Frost status identification methods based on digital and intelligent technologies have shown significant potential. However, existing technologies have significantly reduced accuracy in complex real-world conditions and require urgent improvement. In this paper, we proposed an intelligent recognition method based on the texture features of evaporator surface images. We used a gray-level co-occurrence matrix to extract texture features and combine them with the extreme learning machine optimized by the sparrow algorithm for classification. This is expected to mitigate the impact of external conditions, such as shooting angles and light intensity, thereby achieving strong adaptability. An experimental setup was established to collect 4 125 images of the evaporator in three different frost states under complex working conditions, and the proposed method was validated and compared. The results showed that the accuracy of the method in identifying different conditions can reach 95%, which is significantly higher than that of existing methods by 5-35%. Furthermore, this method has high stability and low cost thereby demonstrating great potential for practical applications.

To address the low thermal storage performance of solid-liquid phase change composites caused by the encapsulation composite effect, composite-shaped phase change materials based on paraffin (PA)/hydrogenated styrene-butadiene block copolymer (SEBS) were prepared using the melt-blending method. A porous mesh structure was designed to optimize the thermal storage performance of the materials through the modulation of process parameters. First, the optimal mass ratio of SEBS-encapsulated PA was determined to be 2∶8; at this ratio, the 80% PA/20% SEBS composite material was well-shaped, and the mass retention rate was maintained above 99%. Furthermore, the results of the orthogonal experiments showed that the process parameters significantly affected the encapsulation and thermal storage properties of the materials, and the extreme difference in the enthalpy of phase change of the nine groups of 80% PA/20% SEBS samples was as high as 28 J/g. Among them, the enthalpy of phase change was increased by 8% when the melting temperature was increased from 150 ℃ to 200 ℃. The results of the orthogonal experiments also showed that the phase change enthalpy of the 80% PA/20% SEBS composites increased by 8%. The optimized PA/SEBS melt blending process parameters were finally determined as: blending time of 2 h, temperature of 200 ℃, stirring rate of 100 r/min, and direct cooling to room temperature. Under this preparation process, the phase transition enthalpy of the composites reached 161.2 J/g with 99.3% crystallinity.

With global warming and the rapid growth of the ski industry, the demand for artificial snowmaking technology and improved snow quality has increased, both of which are closely linked to the atomization characteristics of snowmaking nozzles. In this study, the influences of different nozzle interferences and gas-liquid mass mixing ratios (g_glr) on the droplet size distribution and collision mechanism in a spray field were investigated. The nozzle spacing (d) represents the degree of interference between the nozzles, whereas g_glr signifies the varying degrees of mixing disturbance under identical nozzles. The velocity and size distribution of the droplets in the spray field were measured using a laser particle size measuring instrument and a high-speed camera, whereas the fragmentation and collision of the droplets in the spray field were analyzed based on the Weber number (We). The results indicated that the axial velocity of double nozzles exceeded that of single nozzles at varying spacing intervals. Specifically, when the nozzle spacing was 10 cm and 15 cm, the peak axial velocities were recorded as 5.6 m/s and 5.5 m/s, respectively. The droplet size underwent a non-monotonic variation with the axial distance because of the competition between fragmentation and coalescence, which initially decreased before increasing. The interaction between the spray fields of the two nozzles enhanced the droplet collision, resulting in a higher We number than the individual nozzles. Analysis of the flow field of double nozzles under different arrangement conditions revealed that a higher level of uniformity in particle size distribution was observed when g_glr=0.10 and d=15 cm.

Coastal wells are a commonly used intake method for seawater-source heat pump systems because they help mitigate biofouling and increase seawater temperatures. Coastal well water intake systems operate underground across both saturated and unsaturated zones. Therefore, a three-dimensional gas-liquid porous media seepage model of coastal wells was established based on COMSOL Multiphysics to conduct in-depth research on the seepage mechanisms and water intake behavior of coastal wells. The effects of parameters, such as well depth, pressure difference, well arrangement, and well spacing, on the seepage water intake system were studied. The results indicate that as the well spacing increases, the well depth and well flow rate increase, but the flow rate per unit well depth decreases. The flow rate of the coastal wells is directly proportional to the square difference between the coastline and coastal well porosity pressure. When the seawater hydrostatic porosity pressure difference between the coastline and coastal well was 5 m, the influence radius of the well seepage velocity was approximately 25 m. The velocity field was not affected when the distance between the two wells was greater than 50 m, regardless of whether the wells were arranged parallel or perpendicular to the coastline.

Hydrogen energy, as a carbon-free energy source and a pivotal technology for attaining the goals of "carbon peaking and carbon neutrality", has attracted considerable global interest in recent years. The storage of liquid hydrogen offers several advantages owing to its high hydrogen storage density, low storage pressure, and high energy density. However, the industrial development of hydrogen energy still faces many problems. Technologies for large-scale, long-term storage and long-distance transportation are crucial problems in the utilization of liquid hydrogen. Therefore, it is necessary to develop efficient technologies for storing and transporting liquid hydrogen and to build large liquid hydrogen storage tanks with good thermal insulation performance. In this paper, the development status of large liquid hydrogen storage tank storage technology at home and abroad is reviewed, and key problems such as cryogenic insulation and material thermal stress in liquid hydrogen storage are analyzed. The difficulties associated with hydrogen storage and transportation are highlighted, and the development direction of liquid hydrogen storage technology is examined.

A household photovoltaic intelligent power supply system was proposed to increase the on-site consumption capacity of household photovoltaics and fulfill the requirements for a comfortable and convenient living environment. The system can fulfill the requirements of household electricity, space heating, space cooling, and hot water supply throughout the year. Heating and cooling were realized using air source heat pumps (ASHP), underfloor heating, fan coil units, and energy storage water tanks, which store hot water in winter and cold water in summer. A TRNSYS simulation model of the system was created based on residential buildings in Shandong, China. Based on the simulation results and local electricity prices, the energy storage operation plan was optimized, and the economic efficiency of the system was analyzed. The results indicate that the system can meet the building's year-round electricity consumption, maintain indoor temperatures in winter and summer, and generate revenue from photovoltaic power, yielding the maximum return on investment throughout the entire life cycle. The optimal operating schedule for the ASHP is from 09:00 to 16:00 and 22:00 to 05:00 in winter and from 07:00 to 18:00 and 22:00 to 05:00 in summer. Controllable electrical appliances were used from 10:00 to 16:00. In contrast, appliances with energy storage were used from 11:00 to 14:00 to consume and store the photovoltaic electricity. The energy-storage water tank reduces standard coal consumption by 46% compared to the case without a water tank, demonstrating a substantial energy-saving effect.

Dimethyl sulfoxide (Me₂SO) in cell banking exhibits significant side effects on both the cells and the human body. Therefore, an approach that mitigates the side effects of Me₂SO with comparable efficacy is urgently needed. The human umbilical cord mesenchymal was used as the research material. First, the thermal physical properties of trehalose, glucose, and L-proline and their regulation of ice crystal growth were measured using a differential scanning calorimeter and a cryomicroscope. Cryopreservation experiments were performed to determine the optimal concentration of each component in the cryopreservation solution, and the viability and functionality of the cells after cryopreservation were validated. The results show that there is no significant difference in cell viability (92.42%±0.28%) and recovery rate (87.80%±4.22%) between the use of the novel stem cell cryopreservation solution (1.25 mol/L ethylene glycol+10 g/L whey protein+0.1 mol/L trehalose+Normosol-R) and the conventional cryopreservation solution (a volume fraction of 10% Me₂SO). Moreover, after 3 days of culture, the cell number was (12.42±0.60) × 10⁶ (proliferation fold of 4.97), and the cell phenotype was not significantly different from that of fresh cells. The proposed novel solution for stem cell cryopreservation solves the problem of "Me₂SO-free" cryopreservation of cells and offers promising potential for clinical applications.