Qiang Song

The sustainable development of the ceramics industry is severely impeded by its intensive energy consumption and the concomitant deficits in cooling and freshwater resources. To address these bottlenecks, this study proposes an integrated ejector refrigeration (ER)–humidification–dehumidification (HDH) hybrid system, harnessing ceramic waste heat as the driving energy source to improve overall energy efficiency. A thermodynamic model was developed to analyze the heat transfer characteristics of the ER-HDH system. Comprehensive investigation focuses on the influences of key operating parameters on refrigeration performance, desalination output and overall system efficiency. The results demonstrate that the proposed ER–HDH hybrid system facilitates the efficient thermodynamic cascading of waste heat from both flue gas and internal thermodynamic processes, achieving a high energy utilization factor (EUF) of 0.64 and an exergy efficiency η_Ex of 15.7%. The freshwater yield significantly outperforms that of a standalone HDH system, with the gain output ratio (GOR) more than tripling. The system performance is optimized under elevated generator and evaporator temperatures (T_g and T_e), coupled with a reduced condenser temperature T_c. Across their respective tested ranges, the EUF increases by averages of 19.1%, 45.1% and 38.9%. Furthermore, raising the feed seawater temperature T_{sw_in} significantly elevates the moist air humidity ratio, which in turn drives substantial enhancements in GOR and EUF, by over 83.2% and 58.1%, respectively. T_e and T_{sw_in} should be prioritized to enhance refrigeration and freshwater productions, respectively, while T_c serves as the key determinant for maximizing η_Ex. This study introduces an open dual-cascade ER-HDH system for mid/low-grade flue gas utilization and elucidates the distinct thermodynamic mechanisms governing subsystem interactions, and it addresses a critical knowledge gap in prevalent closed-loop solar-driven ER-HDH systems.

Binary mixtures of difluoromethane (R32) with hydrofluoroolefins (HFOs) possess excellent thermodynamic performance and low global warming potential, supporting the reduction of hydrofluorocarbons (HFCs) usage. In this work, the gaseous speed of sound was measured for R32 + trans-1,3,3,3-tetrafluoropropene (R1234ze(E)) and R32 + hexafluoropropylene (R1216) at temperatures (303.15 to 363.15) K and pressures up to 1063 kPa, with relative expanded uncertainties (k = 2) of 0.022% and 0.026%, respectively. For R32 + R1234ze(E), comparisons with two dedicated models revealed opposite trends: one model systematically overpredicted the speed of sound (positive bias), whereas the other underpredicted it (negative bias). This implies that both models require refinement for gas-phase thermodynamic properties, especially for the gaseous speed of sound. A universal acoustic truncation virial equation was developed using critical parameters and molecular structure parameters. For R32 + R1234ze(E), within the experimental range, this acoustic equation outperformed the two dedicated models. For R32 + R1216, deviations between the acoustic virial equation and experimental data increased with pressure, suggesting inaccuracies in the critical parameters and molecular structure parameters of R1216. Finally, acoustic virial coefficients were derived from the experimental speed of sound. These results provide essential benchmarks for developing and improving dedicated models for these mixtures.

Driven by the large-scale deployment of renewable electricity, water electrolysis has emerged as a leading pathway for high-efficiency hydrogen production. Under practical operating conditions, gas evolution and gas–liquid two-phase flow inside electrolyzers substantially reshape electrode interfacial states and the in-cell mass transfer environment and have been reported to cause performance losses on the order of 10–30% under unfavorable conditions. This review summarizes the evolution of electrode-generated bubbles during nucleation, growth, detachment, and coalescence, and consolidates the fundamental features of two-phase hydrodynamics and phase-distribution patterns in electrolyzer channels. Progress and limitations of major two-phase modeling approaches are then assessed with respect to their capability to resolve the relevant interfacial and transport processes. The impacts of gas evolution and two-phase flow on electrochemical performance, stability, and durability are subsequently discussed. Finally, recent advances in two-phase-flow management—through flow-field organization and structural design, as well as the introduction of external physical fields—are reviewed, together with experimental and diagnostic methods used to quantify bubble behavior and phase distributions. This review aims to provide a coherent understanding of the governing behaviors, research tools, and performance implications of gas evolution and two-phase flow in water electrolysis, and to inform electrode/transport-layer design, flow-field management, and the development of predictive numerical models.

The pursuit of higher current densities and device miniaturization intensifies gas evolution in alkaline water electrolysis, thereby reducing catalyst utilization and degrading system performance. In this work, a visualized alkaline electrolysis system was developed to investigate bubble dynamics on vertically oriented nickel wire electrodes. High-speed imaging coupled with a Yolov8 deep learning model enabled quantitative analysis of oxygen evolution behavior, revealing distinct bubble evolution modes such as isolated growth and coalescence. Systematic experiments demonstrated that current density, electrode diameter, and KOH concentration exert significant influences on bubble size distribution. Further correlation with electrochemical performance showed that increases in bubble population and size result in higher overpotentials, while bubble volume exhibits a strong linear relationship with the system’s ohmic resistance. These findings provide mechanistic insights into the coupling between bubble evolution and electrochemical performance, offering guidance for the design of efficient alkaline electrolyzers.