Low viscous ZnO–propylene glycol nanofluid: a potential coolant candidate
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The rheological characteristics of ZnO–propylene glycol nanofluid have been studied over a temperature range of 10–140 °C and nanoparticle concentration range of 0–2 vol%. The addition of ZnO nanoparticles (35–40 nm) to propylene glycol (PG) weakens the inter-molecular hydrogen bonding in propylene glycol. This is reflected in the reduced values of viscosity for nanoparticle dispersions (nanofluids) compared to that of base fluid. The viscosity decrease is more pronounced at lower temperatures and at higher nanoparticle concentration. The percentage reduction in viscosity is 53 and 32 % at 10 and 28 °C, respectively, for 2 vol% ZnO–propylene glycol nanofluid compared to pure PG. This dispersion has immense potential for cooling application owing to lower viscosity. At high temperatures where the hydrogen bonds in the base fluid are substantially weaker, viscosity of ZnO–PG dispersions is higher than that of PG. An estimated 80 and 37 % enhancement in heat transfer coefficient can be achieved using 2 vol% ZnO–PG nanofluid at temperatures of 10 and 28 °C, respectively.
KeywordsZnO–propylene glycol dispersion Hydrogen bond Viscosity Nanoparticle concentration Colloids
This work is supported by (i) INSPIRE fellowship (Reg. No.: IF110312) of Department of Science and Technology (DST), India. (ii) PG teaching Grant No.: SR/NM/PG-16/2007 of Nano Mission Council, Department of Science & Technology (DST), India (iii) Grant No.: SR/FT/ET-061/2008, DST, India and (iv) Research & Modernization Project #1, SASTRA University, India. The authors thank SASTRA University for the infrastructural support extended during the work.
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