arXiv subjects

Zhan-Long Wang

Publications and source records attributed to Zhan-Long Wang.

4 recordsLinked to original sources

arXiv2024

Crystallization morphology and self-assembly of polyacrylamide solutions during evaporation

This study investigates the crystallization and self-assembly phenomena of polyacrylamide (PAM) solutions during evaporation. While traditional thin-film fabrication methods such as spin coating and drop casting are commonly used, this study utilizes a simple evaporation approach to gain insights into the self-assembly processes of PAM solutions. We examined PAM solutions with varying concentrations (1%, 2%, and 5%) and observed the resulting crystalline structures and morphological changes during evaporation. Spectroscopic absorbance measurements were employed to analyze concentration gradients and crystallization patterns. The findings reveal that the concentration gradient during evaporation significantly impacts the crystallization behavior of PAM solutions. The 2% solution exhibited the clearest and most regular crystalline patterns, whereas the 1% and 5% solutions displayed more complex and irregular morphologies. These observations provide new insights into how solution concentration influences PAM crystallization, contributing to a better understanding of polymer thin-film self-assembly. The novelty of this study lies in exploring PAM self-assembly through controlled evaporation, offering valuable insights for the development of polymer films.

cond-mat.soft↗

arXiv2024

Analysis of fluid flow in fractal microfluidic channels

Fractal channels have significant applications in fields such as microfluidic chips and in vitro diagnostics. However, there is currently insufficient understanding and recognition of fluid flow within fractal channels. In this paper, the fluid flow within dendritic fractal structures was studied with finite element analysis (FEA), focusing on fluid velocity and mass fraction variations. The research introduces the ratio RA (the ratio of the longitudinal channel length to the lateral channel length) as a key parameter to evaluate fractal structures. A smaller RA corresponds to a flatter fractal configuration. By comparing flow rate, velocity, and mass distribution at the outlet of fractal channels with varying RA values, the results demonstrate that flatter fractal structures lead to more uniform flow distribution at the outlet. Meanwhile, the uniformity of fluid flow at the outlet of the fractal channels was analyzed. This work indicates that channel geometry significantly influences fluid dynamics, and also provides valuable insights into optimizing flow dynamics in small-scale applications, contributing to the design of more efficient fluidic devices.

physics.flu-dyn↗

arXiv2024

Inhibition of water vapor condensation by dipropylene glycol droplets on hydrophobic surfaces via vapor sink strategy

Condensation, frosting and icing are natural phenomena, and have been enduring challenges for human society and modern engineering. These phenomena pose a range of issues, from hazardous icy road surfaces, damage to electronic devices due to condensation, to frost accumulation on power lines and aircraft. Dipropylene glycol (DG) is a non-toxic, non-corrosive, and biologically safe substance with excellent hygroscopicity, capable of inhibiting condensation and ice formation through the vapor sink strategy. However, there has been limited research on DG. Herein, we provides a detailed study of the performance of DG droplets in suppressing condensation with experiments and theoretical analysis. Results found that a dry zone ring would form around the DG droplet on a cooling solid surface. The ratio of the dry-zone radius to the DG droplet radius increases with the solid surface temperature and scales as 1/(Tdew-Tc). Results indicated that the cooling time of substrate surface does not affect the ratio in a short period. When the temperature is higher, the ratio decreases slightly with DG droplet volume; while it keeps almost still, when the temperature is lower. A theoretical model is also proposed to reveal the relationship between the ratio and the substrate surface temperature. These findings hold the promise of not only enhancing our understanding of condensation suppression but also advancing the development of innovative solutions for various industries, including transportation, electronics, aviation, and power distribution.

physics.flu-dyn↗

arXiv2023

Suppression of water vapor condensation by glycerol droplets on hydrophobic surfaces

Vapor sink is an effective strategy to suppress the formation of water vapor condensation around hygroscopic materials, and consequently reduce frosting and icing. However, traditionally used materials, such as salt solutions, fibers, exhibit insufficient condensation inhibition or pose safety concerns, such as corrosiveness. In this study, we highlight the remarkable anti-condensation properties of glycerol droplets, attributed to their strong hygroscopicity. We compared the anti-condensation capabilities of glycerol droplets with commonly used salt solutions and hygroscopic alcohols. The results indicated that glycerol droplets establish a relatively expansive dry zone where the condensation is effectively inhibited, while also offering safety compared to other materials. Furthermore, we conducted a systematic study of the anti-condensation properties of glycerol droplets with experiments and theoretical analysis. We explored the varying trends of the dry zone ratio concerning temperature, cooling time, humidity, and droplet volume on hydrophobic surfaces. To provide a comprehensive understanding, we propose a straightforward yet robust theoretical model that elucidates the relationship between this ratio and temperature, aligning well with the experimental data. Our study not only sheds light on the superior anti-condensation qualities of glycerol but also offers insights and guidelines for the development of effective anti-icing and anti-frost materials.

cond-mat.soft↗