Latent heat thermal energy storage (LHTES) has many advantages such as high energy density and phase change at a nearly constant temperature compared with sensible thermal energy storage or chemical energy storage techniques. However, one of its major drawbacks is the low thermal conductivity of phase change materials (PCMs) which impedes the heat transfer efficiency. High thermal conductivity metal foams could be added into the LHTES to enhance the heat transfer speed. Under this case, the investigation of the effects of metal foam porosity and pore size on the melting process is essential for improving the heat storage capability of LHTES. In this article, a pore-scale modeling of melting process in a LHTES unit filled with metal foams is carried out by enthalpy-based multiple-relaxation-time lattice Boltzmann method. The quartet structure generation set is used to generate the morphology of metal foams. In addition, a Compute Unified Device Architecture (CUDA) Fortran code is developed in this work for executing highly parallel computation through graphics processing units. The melting process in the PCMs is investigated in terms of porosity, pore size, nonuniform metal foam, hot wall temperature, and initial subcooled temperature to optimize the design of LHTES filled with metal foams.

Ionic wind, an induced phenomenon during corona discharge, possessing the features of silent operation and no moving parts, has a wide range of applications. Ionic wind generation is accompanied by complex physical processes, involving gas ionization, ion recombination, flow, and various chemical reactions, as well as mutual couplings between some of them. Therefore, understanding the corona discharge process and ionic wind generation is crucial for researchers and engineers to better utilize this phenomenon in practical applications. In this review, the principles of corona discharge and its induced ionic wind are presented. Subsequently, ionic wind generators are discussed according to their applications, and the corresponding advances based on experimental studies and numerical simulations are also reviewed. Moreover, the challenges of transitioning the ionic wind technology from laboratory studies to practical applications are discussed. These challenges include the excessively high onset voltage of the corona, ozone emission, and influence of environmental conditions. Furthermore, the mechanisms of these barriers and several effective approaches for mitigating them are provided. Finally, some future research prospects and the conclusions are presented.

Efficient separation of oil droplets from oily wastewater is an essential task for handling the world water crisis and environmental pollution. However, existing passive oil/water separation technologies suffer from the drawbacks of relatively low separation efficiency and strict material requirements. We present an active dielectrophoretic oil/water separation technique without inducing further environmental contamination. Based on the non-uniform electric field generated through insulated nanopores under direct current (DC) voltage, an oil droplet experiences a negative dielectrophoresis (nDEP) force because of its weaker dielectric property compared with wastewater. Meanwhile, electroosmotic flow also occurs in oil/water separation devices due to the ion motion inside the electric double layer of the nanopore solid surface. Through developing a multiphysical model for immiscible oil/water flow under hybrid electrokinetic effects, the oil/water separation is investigated at different parametric conditions. Electrokinetic filtration of oil droplets through nanopores is successfully achieved when the nDEP force is dominant rather than the electroosmotic electrohydrodynamic (EHD) force for oil droplet movement. To enhance the oil/water separation rate, the relative strength between nDEP force and EHD force on an oil droplet is consolidated via increasing DC voltage, decreasing surface charge density, and optimizing the nanopore configuration. The designed active oil/water separation using DC-DEP offers significant potential for future oily wastewater treatment.