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 Ma 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.

Ground-source heat pump (GSHP) systems using composite energy geostructures can efficiently transfer heat to soil and provide a high coefficient of performance (COP) for both cooling and heating, which has broad application prospects for energy saving in buildings. However, groundwater seepage in the soil can significantly affect the heat-transfer performance of a composite energy geostructure, thereby affecting the overall system performance. Therefore, this study establishes a numerical model of composite energy geo-structures considering groundwater seepage and investigates their synergistic heat transfer mechanism of composite energy geo-structures during summer. The results indicate that the heat transfer of composite energy geostructures is 60% higher than that of single energy piles under seepage conditions owing to the synergistic heat transfer of the energy pile and borehole. Groundwater seepage contributes to heat transfer in composite energy geostructures. When the seepage velocity reaches 60 m/a, heat transfer capacity increases by 1.39 compared to non-seepage conditions, while the temperature rise of the structure itself decreases by 25.32%. Under seepage, the upstream energy geostructures exhibit greater heat transfer with the soil than those downstream. The thermal influence area of the energy geostructures significantly reduced upstream and expanded downstream. This study guides the rational application of composite energy geostructures in regions with seepage.

A novel design for intermediate discharge ports (IDPs) is proposed in response to the issues of increased power consumption and reduced efficiency. This approach involved establishing a geometric model of the scroll and IDPs, focusing particularly on the involute curve and employing dynamic mesh techniques for pump-valve joint simulations across various operational scenarios to examine the different types of IDPs. This study explored the influence mechanisms of IDPs on compressor performance, demonstrated the limitations of conventional port-type IDPs in terms of size and efficiency enhancement, and validated the superior exhaust capabilities and efficiency benefits of involute-shaped IDPs. The simulation results confirmed that conventional IDPs were restricted by size limitations and offered only marginal improvements in compressor efficiency. In contrast, the involute-shaped IDP provided enhanced exhaust capabilities, significantly increasing the exhaust flow rate, thus reducing the power consumption and boosting the overall efficiency of the compressor.

Thermal insulation is a crucial performance indicator for cold-chain transportation equipment. Improving the thermal insulation performance can effectively reduce transportation energy consumption and, thus, lower costs. To enhance the thermal insulation performance of refrigerated trucks, this study conducted tests, analyzed the insulation performance using high-reflectivity insulation materials, and analyzed energy consumption. The study obtained data on the heat flux through the box, air cooling rate inside the box, and temperature uniformity. The experiments demonstrated that applying high-reflectivity insulation materials reduced the peak temperature of the external wall surface of the box by 23.6 ℃, leading to less heat transfer into the compartment through the roof. In the absence of refrigeration, the proportion of heat flux reduction was 46.3%, while at the set refrigeration temperature of 5 ℃, the reduction ranged from 16.7% to 26%. The insulation material improved the temperature uniformity of the external wall of the compartment to 1.12 and the internal uniformity to 1.68. This simultaneously allows the refrigeration system to reach the set temperature more quickly and maintain a lower temperature more easily. Compartments with insulation materials reduced the operating frequency of the compressor by 9.1%, leading to energy savings and good energy efficiency. The research results provide new insights into the energy-efficient use of cold chain transportation equipment and are relevant for facilities such as granaries and cold storage facilities with insulation requirements.

In tumor cryoablation therapy, the effective improvement of the cooling rate of the freezing process is a research hotspot. In this study, a novel cryoablation needle with an adjustable throttle nozzle was designed. The external surface temperature of the needle could be reduced to -80 ℃ within just 4 s, while the traditional cryoablation needle with a fixed throttling nozzle requires 73 s. The three-dimensional heat transfer model simulation results show that the temperature around the cryoablation needle drops sharply to -150 ℃ within 120 s, and the fastest instantaneous cooling rate is 1 500-1 575 ℃/min, which achieves the purpose of rapid cooling. In addition, the -20 ℃ isotherm has a small variation range from 60 s to 120 s (increasing from 5 mm to 6.5 mm), and the temperature changes tend to be gentle after 120 s, and the tissue damage range increases to 9 mm, indicating that the tissue damage range increases significantly. Comprehensive studies have shown that the adjustable throttling nozzle cryoablation needle has a higher cooling rate and larger effective ablation range, which is of great significance for clinical cryoablation treatment.

With continuous economic development, the world faces a growing freshwater shortage and energy scarcity crisis. Reducing energy consumption in handling heat and moisture loads in air-conditioning systems and solving the global water crises have become urgent priorities. The dynamic adsorption and desorption properties of adsorbents significantly affect the heat and moisture transfer characteristics of adsorptive atmospheric water-harvesting systems and dehumidifying heat-exchanger air-conditioning systems. In this study, the dynamic adsorption and desorption properties of thermosensitive composites doped with different thermally conductive nanomaterials, such as nano-copper powder, nano-silver powder and nanographene, were investigated, and the theoretical daily water production capacity of the optimal materials was analyzed. The results show that the thermosensitive materials doped with graphene nanopowder have good adsorption/desorption kinetics. Their equilibrium adsorption capacity reaches 2.51 g/g, which is 1.46 times higher than the undoped thermally conductive materials. The desorption within 60 min is 1.17 times higher than undoped thermally conductive materials. In addition, with a cycle time of 3 h and an adsorption-to-desorption time ratio of 2∶1, the thermosensitive material doped with nanographene can achieve a theoretical daily water volume of 7.02 g/(g·d), which is 21% higher than that of the undoped material.

To further study the influence of heat exchanger structures on system performance and overall power consumption in transcritical CO₂ heat pump air conditioning systems for high-speed trains to improve performance and reduce power consumption, this study builds a numerical simulation model based on the AMEsim simulation platform. The simulation results show that, in the high-speed train heat pump air conditioning system, the influence of the gas cooler structure on system performance is greater than that of the evaporator structure. In terms of the selection of heat exchanger structure, the optimal structure is that during refrigeration, the outdoor heat exchanger adopts the countercurrent arrangement and the indoor heat exchanger adopts the concurrent arrangement (vice versa for heating). At the rated cooling condition of 35 ℃ ambient temperature, the COP is increased by 20.38% compared to the concurrent arrangement in outdoor heat exchangers, and at a rated heating condition of 7 ℃ ambient temperature, the COP is increased by 68.04% compared to the concurrent arrangement of indoor heat exchangers. Considering both the degree of backflow and fan power consumption, in the "fully heat exchange state", system COP increases with backflow degree, while system COP decreases with backflow degree when the air flow rate is insufficient.

Rainbow trout were used as a research subject to investigate the effects of different preservation techniques on the quality and physicochemical properties of aquatic products during storage. Total volatile basic nitrogen (TVB-N), total viable count (TVC), pH, and drip loss rate were used as technical indicators. A comparative study was conducted on the preservation effects of four preservation methods on rainbow trout flesh, including refrigeration (4 ℃±1 ℃), ice temperature (-1 ℃±1 ℃), high-voltage electrostatic field (HVEF, 3 kV/m) + ice temperature (-1 ℃±1 ℃), and HEVF (3 kV/m) + compound biological preservative (mass fraction: 1.40% chitosan + 0.05% lysozyme + 1.30% theaflavin) + ice temperature (-1 ℃±1 ℃). The results showed that treatment with HVEF + compound biological preservatives effectively inhibited microbial growth. Samples from the refrigeration and ice temperature groups had already decayed by the 10th and 12th day, with TVC reaching 7.12 lg (CFU/g) and 7.13 lg (CFU/g), respectively. In contrast, the TVC values of the HVEF + ice temperature and HVEF + compound biological preservative + ice temperature groups were only 6.32 lg (CFU/g) and 5.89 lg (CFU/g) on the 12th day. On the 14th day of storage, the TVB-N of the HVEF + compound preservative + ice temperature group was only 20.17 mg/100 g, which was much lower than that of the other three groups. This investigation indicates that compared to refrigeration and ice-temperature storage, treatment with HVEF + composite preservatives can effectively delay the spoilage process of fish and extend the shelf life of rainbow trout by four days.

Slurries containing a large number of suspended particles, such as ice slurries, have a strong correlation between internal flow patterns and resistance characteristics. The study of its flow characteristics is of great significance for ensuring safety, energy saving, and the prevention of blockages in slurry transportation systems. To ensure safe and energy-efficient operation of the slurry transport system and prevent blockages, this study experimentally investigated the flow characteristics of slurry in pipelines and its critical Reynolds number (Re_c). The focus is on analyzing the flow behavior of the slurry in the transition region, as well as the effects of the ice packing factor (IPF), particle size, and pipe diameter on the slurry flow properties. The results show that the Re_c increases with an increase in the IPF, while the Re_c decreases with an increase in the pipe diameter and particle size. The flow regime transition of the slurry occurred within the Reynolds number (Re) range of approximately 1 700-2 600. In the transition region, the resistance coefficient of the slurry first increases and then decreases as the Re increases.

The aim of this study is to optimize the cryopreservation scheme for microcarrier hepatocyte complexes used in artificial liver support systems to improve cell survival and adhesion rates. The effects of cryoprotectant concentration, loading temperature, and method on cell viability were evaluated experimentally. It was found that cell toxicity and osmotic damage were reduced significantly, and higher cell survival and adhesion rates were maintained by using two-step loading of 5% volume fraction dimethyl sulfoxide (Me₂SO) at 4 ℃. In addition, we investigated the effects of intracellular ice formation and cooling rate on cell viability and attachment. By performing ice seeding at -6 ℃, the intracellular ice damage was effectively reduced, and the adhesion rate of cells after recovery was improved. The experimental results show that a 10% volume fraction of Me₂SO and a cooling rate of 1 ℃/min, despite having high toxicity and osmotic damage, have the best freezing effect due to the smallest difference in thermal expansion. This study provides important techniques for the cryopreservation of microcarrier hepatocyte complexes for artificial liver support systems.