To provide further insight into humid air condensation on hybrid surfaces, an experiment was conducted to visually investigate the condensation process on wettability-interval grooved surfaces, which had hydrophobic ridges and hydrophilic grooves. The droplet dynamic behavior and heat transfer performance of condensation on a wettability-interval grooved surface were explored and compared with four other functional surfaces, including the plain hydrophilic surface, plain hydrophobic surface, hydrophilic grooved surface, and hydrophobic grooved surface. The presence of hydrophobic ridges perpendicular to the groove direction and hydrophilic grooves allowed for the exclusion and easy spreading of droplets, respectively. Compared with the other four functional surfaces, the coupling phenomena during condensation, i.e., the spontaneous suction and directional drainage via hydrophilic grooves, were only found on the wettability-interval grooved surface. These could not only remove condensate quickly but also suppress the formation of the flooded liquid film, which was beneficial to the enhancement of heat transfer performance. It was proven by the experimental results that at subcooling 12 K, the condensation heat flux on the wettability-interval grooved surface reached 1280 W/m², which was 1.25 times that of the plain hydrophobic surface (1030 W/m²), and 15% higher than that of the hydrophobic grooved surface (1110 W/m²). This indicated that the wettability-interval microgrooves could effectively enhance humid air condensation heat transfer performance.

基于体积分数法建立了Y型微通道中双重乳液流动非稳态理论模型, 数值模拟研究了Y型微通道内双重乳液破裂情况, 详细分析了双重乳液流经Y型微通道时的流场信息以及双重乳液形变参数演化特性, 定量地给出了双重乳液流动破裂的驱动以及阻碍作用, 揭示了双重乳液破裂流型的内在机理. 研究结果表明: 流经Y型微通道时, 双重乳液受上游压力驱动产生形变, 形变过程中乳液两端界面张力差阻碍双重乳液形变破裂, 两者正相关; 隧道的出现将减缓双重乳液外液滴颈部收缩速率以及沿流向拉伸的速率, 并减缓了内液滴沿流向拉伸的速率, 其对于内液滴颈部收缩速率影响不大; 隧道破裂和不破裂工况临界线可以采用幂律关系式${l^*} = \beta C{a^b}$进行预测, 隧道破裂和阻塞破裂工况临界线可以采用线性关系${l^*} = \alpha $描述; 与单乳液运动相图相比, 双重乳液运动相图各工况的分界线关系式系数$\alpha $和$\beta $均相应增大.

Cascade utilization is the most promising solution for efficient recovery of industrial waste heat. In this paper, a combine cooling and power(CCP) system including an organic Rankine cycle (ORC) and an absorption refrigeration cycle (ARC) is proposed, aiming to realize the cascade utilization of efficient utilization of low-grade flue gas. With the objective of maximizing the equivalent specific net power output, a particle swarm optimization (PSO) algorithm is employed to optimize the operation parameters of proposed system and the composition and mass fractions of zeotropic working fluid. The results indicate that the proposed system can realize efficient cascade utilization for flue gas waste heat energy. The optimized proposed system achieves a specific net power output of 6.09 kW/kg_FG of a specific refrigeration capacity of 27.65kW/kg_FG. Additionally, heat exchanger exergy losses account for 73.7% and 53.6% of the total exergy losses in the ORC and ABR subsystems, respectively. Therefore, optimizing the heat exchanger equipment is a feasible approach to further enhance the thermodynamic performance of the proposed system.

Piezoelectric micropumps have attracted considerable research attention due to their low production cost, compact size, and controllable output performance. However, the fluid-structure interaction mechanisms in passive check valve-based piezoelectric micropumps remain insufficiently understood, leading to gaps in the current understanding of how their flow characteristics influence overall performance. This study addresses these gaps by establishing a flow model for a typical cantilever valve piezoelectric micropump, considering the effects of fluid-structure interaction. Numerical simulations were performed to investigate the flow field, pressure distribution within the pump chamber, and the dynamic behavior of the check valve during operation. The simulations revealed that the mechanical inertia of the valve causes its opening to lag behind the fluid pressure wave propagation, leading to a phase difference between the piezoelectric actuator and the valve. This delay results in transient backflow during the valve's state transition, which negatively impacts the micropump's overall performance by reducing efficiency. Furthermore, the influences of valve dimensions, pump chamber size, piezoelectric actuator size, as well as external driving voltage and frequency on the pump's operational characteristics were systematically analyzed and optimized. Following the optimization process, the micropump's output flow rate increased to 34.02 mL/min, representing a 54.54% improvement over its initial design, demonstrating the substantial performance gains achieved through structural refinement.

A single-tank molten-salt heat-exchanger storage system is promising for small-scale industrial heat supply, yet transient natural convection and heat transfer in closed tanks remain insufficiently understood. This study develops a physical model and performs numerical simulations of a top-heated single-tank sensible thermal storage unit using a realistic post-discharge, non-uniform initial temperature field. During charging, an upward plume forms near the heating rod, with heat concentrated around the rod and weak flow in remote regions. Two large-scale circulation cells separated by an inclined thermocline are observed, and the interface shifts downward over time. To address short storage duration, a segmented-heating strategy is proposed by varying the heating-section height. Results show that heater height strongly governs flow and storage performance: compared with full-length heating, 2/3-, 1/2-, and 1/3-length configurations extend storage duration by 93%, 100%, and 103.9%, respectively. Lowering the heating zone toward the tank bottom effectively prolongs storage and improves thermal efficiency.