To increase the efficiency of jumping-droplet condensation, this study proposes a hierarchical superhydrophobic surface that promotes coalescence-induced jumping. Inspired by the phenomenon in which a growing droplet moves spontaneously within a superhydrophobic V structure, we fabricated nanograssed zigzag structures on the surface to induce the spontaneous motion of condensed droplets. The direction of the motion was parallel to the surface, so the condensed droplets easily coalesced on it. Compared with a conventional nanograssed superhydrophobic surface, the proposed surface increased the frequency of coalescence-induced jumping by ≥17 times and increased the cumulative volume of jumping droplets by ∼1.8 times. The proposed surface has great potential to increase the efficiency of applications such as water- and energy-harvesting and cooling systems that exploit jumping-droplet condensation.

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The technique of solar dish and Stirling engine combination is the most challenging and promising one. For the efficient conversion of the externally concentrated heat to the usable power, we studied the influences of the wall temperature, inclination angle, and open area ratio of the receiver on the Stirling engine power and efficiency. The theoretical analysis of the heat exchange element of the solar Stirling engine was performed, and the simulation model of the cavity absorber was built and analyzed. The temperature cloud and heat loss trends of the receiver under different wall temperatures, inclination angles, and opening ratios were illustrated. When the wall temperature of the absorber changes from 700 to 1000 K, the efficiency of the engine has increased by 8.8% from 21.34% to 30.11%. The higher the temperature, the higher the efficiency. As the inclination angle of the absorber increases from 0° to 60°, the efficiency of the engine is increased by 7.7% from 21.1% to 28.8%. With the increases of the aperture ratio, the engine output and efficiency reduced. The engine efficiency at the aperture ratio of 0.5 is 4% larger than that at the aperture ratio of 1.

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The hydrogen compression cycle system recycles hydrogen compressed by a compressor at high pressure and stores it in a high-pressure container. Thermal stress is generated due to increase in the pressure and temperature of hydrogen in the hydrogen storage tank during the fast filing process. For the sake of safety, it is of great practical significance to predict and control the temperature change in the tank. The hydrogen charging process in the storage tank of the hydrogen charging station was studied by experimentation and simulation. In this paper, a Computational Fluid Dynamics (CFD) model for non-adiabatic real filling of a 50 MPa hydrogen cylinder was presented. In addition, a shear stress transport (k-ω) model and real gas model were used in order to account for thermo-fluid dynamics during the filling of hydrogen storage tanks (50 MPa, 343 L). Compared to the simulation results with the experimental data carried out under the same conditions, the temperatures calculated from the simulated non-adiabatic condition results were lower (by 5.3%) than those from the theoretical adiabatic condition calculation. The theoretical calculation was based on the experimentally measured pressure value. The calculated simulation mass was 8.23% higher than the theoretical result. The results of this study will be very useful in future hydrogen energy research and hydrogen charging station developments.