Development and characterization of novel and stable silicon nanoparticles-embedded PCM-in-water emulsions for thermal energy storage. (15th March 2019)

• Record Type: Journal Article
• Authors: Zhang, Xiyao; Niu, Jianlei; Wu, Jian-Yong
• Is Part Of: Applied energy. Volume 238(2019)
• Page Start: 1407
• Page End: 1416
• Publication Date: 2019-03-15
• Subjects: PCM emulsion -- Nano-emulsion -- Nano-particle -- Stability -- Viscosity -- Supercooling; Power (Mechanics) -- Periodicals; Energy conservation -- Periodicals; Energy conversion -- Periodicals; 621.042
• DOI: 10.1016/j.apenergy.2019.01.159
• Languages: English
• ISSNs: 0306-2619

Abstract

Graphical abstract: Mechanisms of emulsion instability and PCM emulsions in small bottles prepared in different conditions during the storage period: (a) homogenization with an Ultra-Turrax at 8000 rpm; (b) homogenization at 13, 500 rpm; (c) homogenization at 24, 000 rpm; (d) nano-emulsion with Tween 80 and Span 80; (e) nano-emulsion with an ethoxylate surfactant. Highlights: Carefully examined major factors affecting stability of PCM emulsions. Novel PCM nano-emulsions exhibited a high stability. Addition of SiO2 nanoparticles as nucleating agent improved the stability. Small and uniform droplets with suitable emulsifiers and viscosity was favorable. Abstract: A phase change material (PCM) emulsion was prepared by dispersing the PCM in water with the aid of emulsifiers, which had higher fluidity, higher thermal conductivity, and more flexible volume change than the solid-liquid PCMs. However, a critical issue for their large-scale applications is phase instability due to aggregation and precipitation of the PCM droplets. This work was to develop stable PCM emulsions prepared with n-hexadecane by manipulating the key factors and analyzing the emulsion properties including emulsifier combinations and process conditions, interfacial film properties, droplet size distribution, and rheology characteristics. The stability was further improved with the addition of SiO2 nano-particles. The SiO2 nano-particles also acted as an effective nucleating agent to reduce the degree of supercooling. The thermal performance for potential application in thermal energy storage systems was also examined. Eventually, a novel and highly stable PCM-in-water nano-emulsions with droplets on a scale of tens of nanometers and a transparent appearance was developed for potential application in active thermal energy storage systems.