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Experimental study on thermal conductivity of mono and hybrid Al 2 O 3 –TiO 2 nanofluids for concentrating solar collectors
Author(s) -
Gulzar Ovais,
Qayoum Adnan,
Gupta Rajat
Publication year - 2020
Publication title -
international journal of energy research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.808
H-Index - 95
eISSN - 1099-114X
pISSN - 0363-907X
DOI - 10.1002/er.6105
Subject(s) - nanofluid , thermal conductivity , materials science , nanoparticle , chemical engineering , analytical chemistry (journal) , oleic acid , nanotechnology , chromatography , chemistry , composite material , engineering , biochemistry
Summary Hybrid nanofluids with Therminol‐55 as base fluid and TiO 2 and Al 2 O 3 as nano additives are investigated for parabolic trough collectors. Stable mono nanofluids based on Therminol‐55 with Al 2 O 3 and TiO 2 nanoparticles, and hybrid Al 2 O 3 –TiO 2 nanopowder as additives are prepared by the two‐step method. Oleic acid has been made as a surfactant. The impact of nanoparticle content and fluid temperature on thermal conductivity was studied using the transient hot‐wire technique. Thermal conductivity exhibited an increase with an increase in both temperature and nanoparticle concentration. Al 2 O 3 –TiO 2 Therminol‐55 hybrid nanofluids exhibit the highest increase of 33.5% in thermal conductivity followed by 27.06% in Al 2 O 3 –Therminol‐55, and lowest rise of 21% is found in TiO 2 –Therminol‐55 nanofluids. Synergetic effect of Al 2 O 3 and TiO 2 nanoparticles, increased Brownian motion, and filling of vacant spaces by smaller‐sized TiO 2 nanoparticles in Al 2 O 3 –TiO 2 hybrid nanofluids lead to effective thermal network for enhanced thermal conductivity. Maximum thermal conductivity of 0.15 W/m‐K is observed in the case of hybrid Al 2 O 3 –TiO 2 Therminol‐55 nanofluid with 0.5 wt% concentration. Augmented thermal conductivity of HNF's leads to the efficient photothermal conversion in concentrating solar collectors. Further, a correlation for thermal conductivity with variation in nanoparticle content and the fluid temperature is proposed with R 2 = 0.92.