evaporation is deemed to be a green and sustainable
strategy to cope with the global freshwater crisis. However, effective
water evaporation to achieve high water yield in practical application
is significant but usually neglected. Here, a molybdenum carbide/carbon-based
chitosan hydrogel (MoCC-CH) is designed not only as a solar absorber
but also as a water evaporation accelerator. The proportion of the
chitosan matrix in the hydrogel is tunable to acquire low-tortuosity
channels for facilitating solar-driven evaporation. Thus, the evaporation
rate of MoCC-CH is up to ∼2.19 kg m–2 h–1, and a corresponding solar-thermal conversion efficiency
of 96.15% is obtained under one sun illumination. The highly efficient
water generation is also attributed to a novel water collection device
and valid cooling strategy. The outdoor experiment possesses an excellent
daily freshwater yield of 13.86 kg m–2 in one sunny
day. The successful demonstration of both the well-designed hybrid
hydrogel and an optimized passive solar desalination system offers
the possibility for sustainable solar-driven desalination.
Solar‐powered water evaporation is a primitive technology but interest has revived in the last five years due to the use of nanoenabled photothermal absorbers. The cutting‐edge nanoenabled photothermal materials can exploit a full spectrum of solar radiation with exceptionally high photothermal conversion efficiency. Additionally, photothermal design through heat management and the hierarchy of smooth water‐flow channels have evolved in parallel. Indeed, the integration of all desirable functions into one photothermal layer remains an essential challenge for an effective yield of clean water in remote‐sensing areas. Some nanoenabled photothermal prototypes equipped with unprecedented water evaporation rates have been reported recently for clean water production. Many barriers and difficulties remain, despite the latest scientific and practical implementation developments. This Review seeks to inspire nanoenvironmental research communities to drive onward toward real‐time solar‐driven clean water production.
Solar‐driven interfacial steam generation has emerged as an innovative technique for seawater desalination due to its high photothermal conversion efficiency and potential industrial applications. Herein, a superior interfacial heat accumulation structure composed of semiconductive in situ polymerization (polypyrrole) of nickel foam (IPNF) is reported. The IPNF photothermal layer is assembled with superhydrophilic polyurethane substrate for synchronous water transport and excellent thermal insulation. The 2D ultrablack mesh induces multiple incident rays within the diffused polymerized surface, which allows omnidirectional solar absorption (88.5 %) and intensifying heat localization (49.5 °C @ 1 sun). The state‐of‐the‐art evaporation performances reveal that the integrated IPNF solar evaporator exhibits an excellent evaporation rate (1.74 kg m−2 h−1) and solar‐to‐vapor conversion efficiency (90% excluding heat losses) under 1 kW m−2 solar intensity. Besides this, the long‐term evaporation experiments show negligible discrepancy under seawater conditions (13.27 kg m−2/8 h under 1 kW m−2) and engrain its functioning potential for multimedia and salt rejection (3.2 g × NaCl/240 min). More importantly, herein, insights into different water states in the polymeric network systems during solar‐driven evaporation are provided. This work shows a significant potential to generate freshwater excluding heavy metals and other oil emulsions for industrial applications.
The paper presents a new computational model of non-steady operation of a PEM fuel cell. The model is based on the macroscopic hydrodynamic approach and assumptions of low humidity operation and one-dimensionality of transport processes. Its novelty and advantage in comparison with similar existing models is that it takes into account the finite-time equilibration between vapor and membrane-phase liquid water within the catalyst layers. The phenomenon is described using an additional parameter with the physical meaning of the typical reciprocal time of the equilibration. A computational parametric study is conducted to identify the effect of the finite-time equilibration on steady-state and transient operation of a PEM fuel cell.
This paper describes the development of a comprehensive mathematical and numerical model for simulating the performance of automotive three-way catalytic converters, which are employed to reduce engine exhaust emissions. The model simulates the emission system behavior by using an exhaust system heat conservation and catalyst chemical kinetic submodel. The resulting governing equations are solved numerically. Good agreements were found between the numerical predictions and experimental measurements under both steady-state and transient conditions. The developed model will be used to facilitate the converter design improvement efforts, which are necessary in order to meet the increasingly stricter emission requirements.
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