Comparison of heat transfer performance of water-based graphene nanoplatelet- and multi-walled carbon nanotube-nanofluids in a concentric tube heat exchanger

• Published in: Diamond and related materials 2022-05, Vol.125, p.108976, Article 108976
• Main Authors: Dayou, Sebastian, Ting, Tiew Wei, Vigolo, Brigitte
• Format: Article
• Language: English
• Subjects: Carbon; Chemical Sciences; Concentric heat exchanger; Graphene; Graphene nanoplatelets; Heat exchangers; Heat transfer; Heat transfer coefficient; Heat transfer coefficients; Material chemistry; Multi wall carbon nanotubes; Multi-walled carbon nanotubes; Nanofluids; Nanomaterials; Performance enhancement; Pipes; Tube heat exchangers; Water flow
• ISSN: 0925-9635; 1879-0062
• DOI: 10.1016/j.diamond.2022.108976

Carbon nanomaterials are of great interest for next generation nanofluids. Carbon nanotubes and graphene are, in particular, highly thermally conductive and their use as thermal fluid is gaining momentum among the research community. This work investigates the thermal performance of graphene nanoplatelet (GnP)-nanofluid and multi-walled carbon nanotube (MWCNT)-nanofluid by using a concentric pipe heat exchanger. The prepared nanofluid flowed in the inner pipe as hot fluid, which was in the opposite direction of a colder water flow in the annulus pipe. The investigation was conducted by varying the volumetric flow (from 1.5 to 2.5 L/min) and nanofluid concentration (from 0.01 to 0.35 vol%). The heat transfer coefficient (HTC) of GnP-nanofluid was observed to be superior to that of MWCNT-nanofluid. The maximum increase in HTC relative to the pure base fluid is approximately 16.8, 24.2 and 26.1% for GnP-nanofluid; and 8.8, 13.8 and 14.4% for MWCNT-nanofluid flowing at 1.5, 2.0 and 2.5 L/min, respectively. This positive impact on heat transfer performance enhancement reached the maximum when an optimum concentration is reached in both nanofluids. Compared to the maximum HTC ratio brought by MWCNT-nanofluid at 0.15 vol% and 2.5 L/min, GnP-nanofluid produced a greater HTC ratio, even at relatively low concentration (0.05 vol%) and volumetric flow (1.5 L/min) which is rather desirable for practical applications. [Display omitted] •Increase in GnP concentration greatly enhances the nanofluid thermal conductivity.•Increase in GnP concentration does not distinctly increase the nanofluid viscosity.•Heat transfer coefficient of GnP-nanofluid is higher than that of MWCNT-nanofluid.•GnPs has better heat transfer performance than MWCNTs even at lower concentration.•Maximum heat transfer performance achieved at an optimum nanoparticle concentration.