Aqueous nanofluids containing paraffin-filled MWCNTs for improving effective specific heat and extinction coefficient

• Published in: Energy (Oxford) 2020-11, Vol.210, p.118523, Article 118523
• Main Authors: Choi, Tae Jong, Kim, Sung Hyoun, Jang, Seok Pil, Lin, Lingnan, Kedzierski, M.A.
• Format: Article
• Language: English
• Subjects: Calorimetry; Capillarity; Coefficients; Decantation; Differential scanning calorimetry; Effective specific heat; Extinction coefficient; Heat; Multi wall carbon nanotubes; Nanofluids; Nanoparticles; Nanotechnology; Nanotubes; Paraffin; Paraffin wax; Paraffin-filled MWCNTs; Scattering; Specific heat; Stability analysis
• ISSN: 0360-5442; 0038-092X; 1873-6785; 1471-1257
• DOI: 10.1016/j.energy.2020.118523

This paper presents measurements of the effective specific heat and the extinction coefficient for aqueous nanofluids dispersed with paraffin-filled Multi-Walled Carbon NanoTubes (MWCNTs). The MWCNTs were filled with paraffin wax by capillary action. Centrifugal decanting was used to modify the traditional two-step method so as to produce a nanofluid dispersion that was more stable than that produced by the traditional method. The stability of each suspension was quantitatively evaluated with a laser scattering method over 7 days. A differential scanning calorimetry (DSC) and the three-slap method were used to measure the effective specific heat and the extinction coefficient of the nanofluids, respectively. The measured effective specific heat of the water-based paraffin-filled MWCNTs nanofluid, with a volume fraction of 1%, was up to 5.1% larger than that for the water-based MWCNT nanofluids without paraffin wax. The nanofluid extinction coefficient was shown to increase linearly with the volume fraction for data within the independent scattering regime, which occurred when the nanoparticle-distance/wavelength ratio (c/λ) was less than 2. •The novel nanofluids dispersing the paraffin-filled MWCNTs are presented.•The enhancement of the effective specific heat of the nanofluids is presented.•The enhancement behavior of the nanofluid extinction coefficient is presented.