Abstract
Nanofluids are systems with several interesting heat transfer applications, but it can be a challenge to obtain highly stable suspensions. One way to overcome this challenge is to create the appropriate conditions to disperse the nanomaterial in the fluid. However, when the heat transfer fluid used is a non-polar organic oil, there are complications due to the low polarity of this solvent. Therefore, this study introduces a method to synthesize TiO2 nanoparticles inside a non-polar fluid typically used in heat transfer applications. Nanoparticles produced were characterized for their structural and chemical properties using techniques such as X-ray Diffraction (XRD), Raman spectroscopy, Transmission Electron Microscopy (TEM), Fourier Transform Infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The nanofluid showed a high stability, which was analyzed by means of UV-vis spectroscopy and by measuring its particle size and ζ potential. So, this nanofluid will have many possible applications. In this work, the use as heat transfer fluid was tested. In this sense, nanofluid also presented enhanced isobaric specific heat and thermal conductivity values with regard to the base fluid, which led to the heat transfer coefficient increasing by 14.4%. Thus, the nanofluid prepared could be a promising alternative to typical HTFs thanks to its improved thermal properties and high stability resulting from the synthesis procedure.
Highlights
Nanofluids are a colloidal suspension on nanosized materials in a base fluid which was for the first time reported by Choi et al in 1995 [1]
The crystalline phases and crystallinity of the synthesized nanoparticles were analyzed by X-ray diffraction
The synthesized TiO2 nanoparticles show low crystallinity, observed from the low intensity of the diffractogram compared with the reference of TiO2 anatase phase in the pattern below, and from the presence of broad peaks in the diffractogram obtained
Summary
Nanofluids are a colloidal suspension on nanosized materials in a base fluid which was for the first time reported by Choi et al in 1995 [1]. In the case of nanofluids, stability is an important factor to take into account because their thermal properties depend on the amount of nanoparticles in the base fluid that are able to transport heat [5,6,7]. The single-step method involves the in-situ synthesis of the nanoparticles in the base fluid. In the two-step method, the nanoparticles are first synthesized, controlling their shape, size, etc., and dispersed into the base fluid to obtain a colloidal suspension, typically by means of sonication. Xuan et al [15] studied the effect of the loading of SBDS in Cu-nanofluids prepared with water as the base fluid, reporting a decrease in thermal conductivity among the nanofluids with a higher concentration of surfactant
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