Hydrophilic Coating of Copper Particle Monolayer Wicks for Enhanced Passive Water Transport

Passive water transport through thin-surface wicks made of heat conducting material is important for developing thermal management devices such as heat pipes and spreaders. In this study, we demonstrated the hydrophilic coating of a Cu particle monolayer wick for enhanced water transport. We fabricated a Cu particle monolayer using Cu powder with a nominal particle diameter of 100 μm and determined the particle size distribution using scanning electron microscopy (SEM). We observed a remarkable change in the water contact angle on the application of a hydrophilic coating, which demonstrated the enhanced passive water transport. The elemental mapping of Cu, O, and Si obtained by electron probe microanalysis confirmed the deposition of the SiO2-based coating material on each Cu particle. Although the Cu particles were only partially covered by SiO2, a remarkable enhancement in wettability was achieved. Finally, we conducted a rate-of-rise experiment to quantitatively characterize the water transport performance of the coated Cu particle monolayer. Thus, we propose hydrophilic coating as a simple and effective method to enhance passive water transport through Cu particle monolayer wicks.

Numerical Modeling of the Conductivity of the Particle Monolayer with Reduced Size

Fractures filled with a proppant monolayer play an important role in the hydraulic fracture network. Predicting the conductivity of these fractures is the basis of fracture network optimization. However, little attention has been paid to the conductivity of the proppant monolayer. The change of conductivity under various conditions is currently not fully understood. Therefore, in this paper, the conductivity variation under different conditions are simulated. The reduction of particle size was calculated by existing analytical models. The permeability variation was calculated through computational fluid dynamics (CFD) combined with COMSOL Multiphysics. The controlling factors of conductivity under a proppant monolayer were identified. Simulation results indicate that elastic parameters, closure pressure, and proppant distribution have significant influence on conductivity, while creep parameters, such as rock viscosity and time, have limited influence on conductivity. Moreover, the changes in permeability, porosity, and tortuosity with variation of embedment were analyzed. Results indicated that with an increase in embedment, the permeability and porosity decrease as expected. The main reduction (nearly half) emerges in the first 20% of proppant embedment. Furthermore, the permeability of a single particle deviates largely from the prediction of Carman-Kozeny (CK) equation. The tortuosity of proppant particle increases with a decrease in particle size due to embedment. A modification of the Carman-Kozeny equation is proposed to address this influence.

Interface deformations affect the orientation transition of magnetic ellipsoidal particles adsorbed at fluid–fluid interfaces

Magnetic ellipsoidal particles adsorbed at a fluid–fluid interface create dipolar interface deformations in response to a magnetic field, which affects their orientation and may lead to novel particle monolayer structures.