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International Heat Transfer Conference 15

ISSN: 2377-424X (online)
ISSN: 2377-4371 (flashdrive)

Improving Solidification Structure of Paraffin-Based Nanofluid by Surfactant and Ultrasound

Lisi Jia
Soft Matter Center, Guangdong Provincial Key Laboratory on Functional Soft Condensed Matter, School of Materials and Energy, Guangdong University of Technology, Guangzhou 510006, China

Ying Chen
Soft Matter Center, Guangdong Provincial Key Laboratory on Functional Soft Condensed Matter, School of Materials and Energy, Guangdong University of Technology, Guangzhou 510006, China

Shijun Lei
Guangdong University of Technology, No. 100 Waihuan Xi Road, GuangzhouHigher Education Mega Center

Songping Mo
Soft Matter Center, Guangdong Provincial Key Laboratory on Functional Soft Condensed Matter, School of Materials and Energy, Guangdong University of Technology, Guangzhou 510006, China

Zhuowei Liu
Guangdong University of Technology, No. 100 Waihuan Xi Road, GuangzhouHigher Education Mega Center

Xuefeng Shao
Guangdong University of Technology, No. 100 Waihuan Xi Road, GuangzhouHigher Education Mega Center

DOI: 10.1615/IHTC15.cnd.009506
pages 1443-1450


KEY WORDS: Conduction, Heat transfer enhancement, nanofluid, ice layer, surfactant, supersonic vibration

Abstract

Paraffin-based nanofluids have higher thermal conductivities compared to the paraffins, which makes them potential useful in thermal energy storage. However, few studies have been conducted on the solidification structure of paraffin-based nanofluids which directly decides whether or not they can be reused for energy storage. This paper investigated the effects of surfactant and ultrasound on the solidification behaviors of Al/Paraffin nanofluid. Sodium dodecyl sulfonate (SDS), polyvinyl pyrrolidone (PVP) and cetyl trimethyl ammonium bromide (CTAB) were used as surfactants to prepare Al/Paraffin nanofluids. Al/SDS/Paraffin, Al/PVP/Paraffin and Al/CTAB/Paraffin nanofluids as well as Al/Paraffin nanofluid without surfactant were cooled down with and without ultrasonic vibration. An environmental scanning electron microscope was used to measure the solidification structures of paraffin-based nanofluids. The Al/Paraffin nanofluid was found to solidify in the form of annulus icing. The advancing solidification front pushed the Al nanoparticles to the middle of container, resulting in the aggregation of Al nanoparticles there. The Al micro-aggregates settled down quickly during the subsequent melting process, bring out the failure problem of Al/Paraffin nanofluid. Surfactants CTAB, PVP and SDS couldn’t solve this failure problem of Al/Paraffin nanofluid fundamentally, but ultrasonic vibration could. The SEM images of solidified paraffin-based nanofluids with ultrasonic vibration showed that the Al nano-aggregates distributed evenly in the paraffin. It was found that solidification of each paraffin-based nanofluid assisted by ultrasonic vibration almost took place simultaneously throughout the container. We therefore obtained that ultrasonic vibration could promote the heterogeneous nucleation on Al nanoparticles mainly by reducing the temperature inhomogeneity in paraffin-based nanofluids.

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